|
|
@@ -0,0 +1,5647 @@
|
|
|
+.\" Automatically generated by Pod::Man 2.28 (Pod::Simple 3.29)
|
|
|
+.\"
|
|
|
+.\" Standard preamble:
|
|
|
+.\" ========================================================================
|
|
|
+.de Sp \" Vertical space (when we can't use .PP)
|
|
|
+.if t .sp .5v
|
|
|
+.if n .sp
|
|
|
+..
|
|
|
+.de Vb \" Begin verbatim text
|
|
|
+.ft CW
|
|
|
+.nf
|
|
|
+.ne \\$1
|
|
|
+..
|
|
|
+.de Ve \" End verbatim text
|
|
|
+.ft R
|
|
|
+.fi
|
|
|
+..
|
|
|
+.\" Set up some character translations and predefined strings. \*(-- will
|
|
|
+.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
|
|
|
+.\" double quote, and \*(R" will give a right double quote. \*(C+ will
|
|
|
+.\" give a nicer C++. Capital omega is used to do unbreakable dashes and
|
|
|
+.\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff,
|
|
|
+.\" nothing in troff, for use with C<>.
|
|
|
+.tr \(*W-
|
|
|
+.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
|
|
|
+.ie n \{\
|
|
|
+. ds -- \(*W-
|
|
|
+. ds PI pi
|
|
|
+. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
|
|
|
+. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
|
|
|
+. ds L" ""
|
|
|
+. ds R" ""
|
|
|
+. ds C` ""
|
|
|
+. ds C' ""
|
|
|
+'br\}
|
|
|
+.el\{\
|
|
|
+. ds -- \|\(em\|
|
|
|
+. ds PI \(*p
|
|
|
+. ds L" ``
|
|
|
+. ds R" ''
|
|
|
+. ds C`
|
|
|
+. ds C'
|
|
|
+'br\}
|
|
|
+.\"
|
|
|
+.\" Escape single quotes in literal strings from groff's Unicode transform.
|
|
|
+.ie \n(.g .ds Aq \(aq
|
|
|
+.el .ds Aq '
|
|
|
+.\"
|
|
|
+.\" If the F register is turned on, we'll generate index entries on stderr for
|
|
|
+.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
|
|
|
+.\" entries marked with X<> in POD. Of course, you'll have to process the
|
|
|
+.\" output yourself in some meaningful fashion.
|
|
|
+.\"
|
|
|
+.\" Avoid warning from groff about undefined register 'F'.
|
|
|
+.de IX
|
|
|
+..
|
|
|
+.nr rF 0
|
|
|
+.if \n(.g .if rF .nr rF 1
|
|
|
+.if (\n(rF:(\n(.g==0)) \{
|
|
|
+. if \nF \{
|
|
|
+. de IX
|
|
|
+. tm Index:\\$1\t\\n%\t"\\$2"
|
|
|
+..
|
|
|
+. if !\nF==2 \{
|
|
|
+. nr % 0
|
|
|
+. nr F 2
|
|
|
+. \}
|
|
|
+. \}
|
|
|
+.\}
|
|
|
+.rr rF
|
|
|
+.\"
|
|
|
+.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
|
|
|
+.\" Fear. Run. Save yourself. No user-serviceable parts.
|
|
|
+. \" fudge factors for nroff and troff
|
|
|
+.if n \{\
|
|
|
+. ds #H 0
|
|
|
+. ds #V .8m
|
|
|
+. ds #F .3m
|
|
|
+. ds #[ \f1
|
|
|
+. ds #] \fP
|
|
|
+.\}
|
|
|
+.if t \{\
|
|
|
+. ds #H ((1u-(\\\\n(.fu%2u))*.13m)
|
|
|
+. ds #V .6m
|
|
|
+. ds #F 0
|
|
|
+. ds #[ \&
|
|
|
+. ds #] \&
|
|
|
+.\}
|
|
|
+. \" simple accents for nroff and troff
|
|
|
+.if n \{\
|
|
|
+. ds ' \&
|
|
|
+. ds ` \&
|
|
|
+. ds ^ \&
|
|
|
+. ds , \&
|
|
|
+. ds ~ ~
|
|
|
+. ds /
|
|
|
+.\}
|
|
|
+.if t \{\
|
|
|
+. ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
|
|
|
+. ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
|
|
|
+. ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
|
|
|
+. ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
|
|
|
+. ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
|
|
|
+. ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
|
|
|
+.\}
|
|
|
+. \" troff and (daisy-wheel) nroff accents
|
|
|
+.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
|
|
|
+.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
|
|
|
+.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
|
|
|
+.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
|
|
|
+.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
|
|
|
+.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
|
|
|
+.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
|
|
|
+.ds ae a\h'-(\w'a'u*4/10)'e
|
|
|
+.ds Ae A\h'-(\w'A'u*4/10)'E
|
|
|
+. \" corrections for vroff
|
|
|
+.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
|
|
|
+.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
|
|
|
+. \" for low resolution devices (crt and lpr)
|
|
|
+.if \n(.H>23 .if \n(.V>19 \
|
|
|
+\{\
|
|
|
+. ds : e
|
|
|
+. ds 8 ss
|
|
|
+. ds o a
|
|
|
+. ds d- d\h'-1'\(ga
|
|
|
+. ds D- D\h'-1'\(hy
|
|
|
+. ds th \o'bp'
|
|
|
+. ds Th \o'LP'
|
|
|
+. ds ae ae
|
|
|
+. ds Ae AE
|
|
|
+.\}
|
|
|
+.rm #[ #] #H #V #F C
|
|
|
+.\" ========================================================================
|
|
|
+.\"
|
|
|
+.IX Title "LIBEV 3"
|
|
|
+.TH LIBEV 3 "2017-06-21" "libev-4.24" "libev - high performance full featured event loop"
|
|
|
+.\" For nroff, turn off justification. Always turn off hyphenation; it makes
|
|
|
+.\" way too many mistakes in technical documents.
|
|
|
+.if n .ad l
|
|
|
+.nh
|
|
|
+.SH "NAME"
|
|
|
+libev \- a high performance full\-featured event loop written in C
|
|
|
+.SH "SYNOPSIS"
|
|
|
+.IX Header "SYNOPSIS"
|
|
|
+.Vb 1
|
|
|
+\& #include <ev.h>
|
|
|
+.Ve
|
|
|
+.SS "\s-1EXAMPLE PROGRAM\s0"
|
|
|
+.IX Subsection "EXAMPLE PROGRAM"
|
|
|
+.Vb 2
|
|
|
+\& // a single header file is required
|
|
|
+\& #include <ev.h>
|
|
|
+\&
|
|
|
+\& #include <stdio.h> // for puts
|
|
|
+\&
|
|
|
+\& // every watcher type has its own typedef\*(Aqd struct
|
|
|
+\& // with the name ev_TYPE
|
|
|
+\& ev_io stdin_watcher;
|
|
|
+\& ev_timer timeout_watcher;
|
|
|
+\&
|
|
|
+\& // all watcher callbacks have a similar signature
|
|
|
+\& // this callback is called when data is readable on stdin
|
|
|
+\& static void
|
|
|
+\& stdin_cb (EV_P_ ev_io *w, int revents)
|
|
|
+\& {
|
|
|
+\& puts ("stdin ready");
|
|
|
+\& // for one\-shot events, one must manually stop the watcher
|
|
|
+\& // with its corresponding stop function.
|
|
|
+\& ev_io_stop (EV_A_ w);
|
|
|
+\&
|
|
|
+\& // this causes all nested ev_run\*(Aqs to stop iterating
|
|
|
+\& ev_break (EV_A_ EVBREAK_ALL);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& // another callback, this time for a time\-out
|
|
|
+\& static void
|
|
|
+\& timeout_cb (EV_P_ ev_timer *w, int revents)
|
|
|
+\& {
|
|
|
+\& puts ("timeout");
|
|
|
+\& // this causes the innermost ev_run to stop iterating
|
|
|
+\& ev_break (EV_A_ EVBREAK_ONE);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& int
|
|
|
+\& main (void)
|
|
|
+\& {
|
|
|
+\& // use the default event loop unless you have special needs
|
|
|
+\& struct ev_loop *loop = EV_DEFAULT;
|
|
|
+\&
|
|
|
+\& // initialise an io watcher, then start it
|
|
|
+\& // this one will watch for stdin to become readable
|
|
|
+\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
|
|
|
+\& ev_io_start (loop, &stdin_watcher);
|
|
|
+\&
|
|
|
+\& // initialise a timer watcher, then start it
|
|
|
+\& // simple non\-repeating 5.5 second timeout
|
|
|
+\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
|
|
|
+\& ev_timer_start (loop, &timeout_watcher);
|
|
|
+\&
|
|
|
+\& // now wait for events to arrive
|
|
|
+\& ev_run (loop, 0);
|
|
|
+\&
|
|
|
+\& // break was called, so exit
|
|
|
+\& return 0;
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.SH "ABOUT THIS DOCUMENT"
|
|
|
+.IX Header "ABOUT THIS DOCUMENT"
|
|
|
+This document documents the libev software package.
|
|
|
+.PP
|
|
|
+The newest version of this document is also available as an html-formatted
|
|
|
+web page you might find easier to navigate when reading it for the first
|
|
|
+time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
|
|
|
+.PP
|
|
|
+While this document tries to be as complete as possible in documenting
|
|
|
+libev, its usage and the rationale behind its design, it is not a tutorial
|
|
|
+on event-based programming, nor will it introduce event-based programming
|
|
|
+with libev.
|
|
|
+.PP
|
|
|
+Familiarity with event based programming techniques in general is assumed
|
|
|
+throughout this document.
|
|
|
+.SH "WHAT TO READ WHEN IN A HURRY"
|
|
|
+.IX Header "WHAT TO READ WHEN IN A HURRY"
|
|
|
+This manual tries to be very detailed, but unfortunately, this also makes
|
|
|
+it very long. If you just want to know the basics of libev, I suggest
|
|
|
+reading \*(L"\s-1ANATOMY OF A WATCHER\*(R"\s0, then the \*(L"\s-1EXAMPLE PROGRAM\*(R"\s0 above and
|
|
|
+look up the missing functions in \*(L"\s-1GLOBAL FUNCTIONS\*(R"\s0 and the \f(CW\*(C`ev_io\*(C'\fR and
|
|
|
+\&\f(CW\*(C`ev_timer\*(C'\fR sections in \*(L"\s-1WATCHER TYPES\*(R"\s0.
|
|
|
+.SH "ABOUT LIBEV"
|
|
|
+.IX Header "ABOUT LIBEV"
|
|
|
+Libev is an event loop: you register interest in certain events (such as a
|
|
|
+file descriptor being readable or a timeout occurring), and it will manage
|
|
|
+these event sources and provide your program with events.
|
|
|
+.PP
|
|
|
+To do this, it must take more or less complete control over your process
|
|
|
+(or thread) by executing the \fIevent loop\fR handler, and will then
|
|
|
+communicate events via a callback mechanism.
|
|
|
+.PP
|
|
|
+You register interest in certain events by registering so-called \fIevent
|
|
|
+watchers\fR, which are relatively small C structures you initialise with the
|
|
|
+details of the event, and then hand it over to libev by \fIstarting\fR the
|
|
|
+watcher.
|
|
|
+.SS "\s-1FEATURES\s0"
|
|
|
+.IX Subsection "FEATURES"
|
|
|
+Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
|
|
|
+BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
|
|
|
+for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
|
|
|
+(for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner
|
|
|
+inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative
|
|
|
+timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling
|
|
|
+(\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status
|
|
|
+change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event
|
|
|
+loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and
|
|
|
+\&\f(CW\*(C`ev_check\*(C'\fR watchers) as well as file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even
|
|
|
+limited support for fork events (\f(CW\*(C`ev_fork\*(C'\fR).
|
|
|
+.PP
|
|
|
+It also is quite fast (see this
|
|
|
+benchmark <http://libev.schmorp.de/bench.html> comparing it to libevent
|
|
|
+for example).
|
|
|
+.SS "\s-1CONVENTIONS\s0"
|
|
|
+.IX Subsection "CONVENTIONS"
|
|
|
+Libev is very configurable. In this manual the default (and most common)
|
|
|
+configuration will be described, which supports multiple event loops. For
|
|
|
+more info about various configuration options please have a look at
|
|
|
+\&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support
|
|
|
+for multiple event loops, then all functions taking an initial argument of
|
|
|
+name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have
|
|
|
+this argument.
|
|
|
+.SS "\s-1TIME REPRESENTATION\s0"
|
|
|
+.IX Subsection "TIME REPRESENTATION"
|
|
|
+Libev represents time as a single floating point number, representing
|
|
|
+the (fractional) number of seconds since the (\s-1POSIX\s0) epoch (in practice
|
|
|
+somewhere near the beginning of 1970, details are complicated, don't
|
|
|
+ask). This type is called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use
|
|
|
+too. It usually aliases to the \f(CW\*(C`double\*(C'\fR type in C. When you need to do
|
|
|
+any calculations on it, you should treat it as some floating point value.
|
|
|
+.PP
|
|
|
+Unlike the name component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for
|
|
|
+time differences (e.g. delays) throughout libev.
|
|
|
+.SH "ERROR HANDLING"
|
|
|
+.IX Header "ERROR HANDLING"
|
|
|
+Libev knows three classes of errors: operating system errors, usage errors
|
|
|
+and internal errors (bugs).
|
|
|
+.PP
|
|
|
+When libev catches an operating system error it cannot handle (for example
|
|
|
+a system call indicating a condition libev cannot fix), it calls the callback
|
|
|
+set via \f(CW\*(C`ev_set_syserr_cb\*(C'\fR, which is supposed to fix the problem or
|
|
|
+abort. The default is to print a diagnostic message and to call \f(CW\*(C`abort
|
|
|
+()\*(C'\fR.
|
|
|
+.PP
|
|
|
+When libev detects a usage error such as a negative timer interval, then
|
|
|
+it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism,
|
|
|
+so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in
|
|
|
+the libev caller and need to be fixed there.
|
|
|
+.PP
|
|
|
+Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions, and also has
|
|
|
+extensive consistency checking code. These do not trigger under normal
|
|
|
+circumstances, as they indicate either a bug in libev or worse.
|
|
|
+.SH "GLOBAL FUNCTIONS"
|
|
|
+.IX Header "GLOBAL FUNCTIONS"
|
|
|
+These functions can be called anytime, even before initialising the
|
|
|
+library in any way.
|
|
|
+.IP "ev_tstamp ev_time ()" 4
|
|
|
+.IX Item "ev_tstamp ev_time ()"
|
|
|
+Returns the current time as libev would use it. Please note that the
|
|
|
+\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp
|
|
|
+you actually want to know. Also interesting is the combination of
|
|
|
+\&\f(CW\*(C`ev_now_update\*(C'\fR and \f(CW\*(C`ev_now\*(C'\fR.
|
|
|
+.IP "ev_sleep (ev_tstamp interval)" 4
|
|
|
+.IX Item "ev_sleep (ev_tstamp interval)"
|
|
|
+Sleep for the given interval: The current thread will be blocked
|
|
|
+until either it is interrupted or the given time interval has
|
|
|
+passed (approximately \- it might return a bit earlier even if not
|
|
|
+interrupted). Returns immediately if \f(CW\*(C`interval <= 0\*(C'\fR.
|
|
|
+.Sp
|
|
|
+Basically this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR.
|
|
|
+.Sp
|
|
|
+The range of the \f(CW\*(C`interval\*(C'\fR is limited \- libev only guarantees to work
|
|
|
+with sleep times of up to one day (\f(CW\*(C`interval <= 86400\*(C'\fR).
|
|
|
+.IP "int ev_version_major ()" 4
|
|
|
+.IX Item "int ev_version_major ()"
|
|
|
+.PD 0
|
|
|
+.IP "int ev_version_minor ()" 4
|
|
|
+.IX Item "int ev_version_minor ()"
|
|
|
+.PD
|
|
|
+You can find out the major and minor \s-1ABI\s0 version numbers of the library
|
|
|
+you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
|
|
|
+\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
|
|
|
+symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
|
|
|
+version of the library your program was compiled against.
|
|
|
+.Sp
|
|
|
+These version numbers refer to the \s-1ABI\s0 version of the library, not the
|
|
|
+release version.
|
|
|
+.Sp
|
|
|
+Usually, it's a good idea to terminate if the major versions mismatch,
|
|
|
+as this indicates an incompatible change. Minor versions are usually
|
|
|
+compatible to older versions, so a larger minor version alone is usually
|
|
|
+not a problem.
|
|
|
+.Sp
|
|
|
+Example: Make sure we haven't accidentally been linked against the wrong
|
|
|
+version (note, however, that this will not detect other \s-1ABI\s0 mismatches,
|
|
|
+such as \s-1LFS\s0 or reentrancy).
|
|
|
+.Sp
|
|
|
+.Vb 3
|
|
|
+\& assert (("libev version mismatch",
|
|
|
+\& ev_version_major () == EV_VERSION_MAJOR
|
|
|
+\& && ev_version_minor () >= EV_VERSION_MINOR));
|
|
|
+.Ve
|
|
|
+.IP "unsigned int ev_supported_backends ()" 4
|
|
|
+.IX Item "unsigned int ev_supported_backends ()"
|
|
|
+Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR
|
|
|
+value) compiled into this binary of libev (independent of their
|
|
|
+availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for
|
|
|
+a description of the set values.
|
|
|
+.Sp
|
|
|
+Example: make sure we have the epoll method, because yeah this is cool and
|
|
|
+a must have and can we have a torrent of it please!!!11
|
|
|
+.Sp
|
|
|
+.Vb 2
|
|
|
+\& assert (("sorry, no epoll, no sex",
|
|
|
+\& ev_supported_backends () & EVBACKEND_EPOLL));
|
|
|
+.Ve
|
|
|
+.IP "unsigned int ev_recommended_backends ()" 4
|
|
|
+.IX Item "unsigned int ev_recommended_backends ()"
|
|
|
+Return the set of all backends compiled into this binary of libev and
|
|
|
+also recommended for this platform, meaning it will work for most file
|
|
|
+descriptor types. This set is often smaller than the one returned by
|
|
|
+\&\f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on most BSDs
|
|
|
+and will not be auto-detected unless you explicitly request it (assuming
|
|
|
+you know what you are doing). This is the set of backends that libev will
|
|
|
+probe for if you specify no backends explicitly.
|
|
|
+.IP "unsigned int ev_embeddable_backends ()" 4
|
|
|
+.IX Item "unsigned int ev_embeddable_backends ()"
|
|
|
+Returns the set of backends that are embeddable in other event loops. This
|
|
|
+value is platform-specific but can include backends not available on the
|
|
|
+current system. To find which embeddable backends might be supported on
|
|
|
+the current system, you would need to look at \f(CW\*(C`ev_embeddable_backends ()
|
|
|
+& ev_supported_backends ()\*(C'\fR, likewise for recommended ones.
|
|
|
+.Sp
|
|
|
+See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
|
|
|
+.IP "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())" 4
|
|
|
+.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())"
|
|
|
+Sets the allocation function to use (the prototype is similar \- the
|
|
|
+semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is
|
|
|
+used to allocate and free memory (no surprises here). If it returns zero
|
|
|
+when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort
|
|
|
+or take some potentially destructive action.
|
|
|
+.Sp
|
|
|
+Since some systems (at least OpenBSD and Darwin) fail to implement
|
|
|
+correct \f(CW\*(C`realloc\*(C'\fR semantics, libev will use a wrapper around the system
|
|
|
+\&\f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions by default.
|
|
|
+.Sp
|
|
|
+You could override this function in high-availability programs to, say,
|
|
|
+free some memory if it cannot allocate memory, to use a special allocator,
|
|
|
+or even to sleep a while and retry until some memory is available.
|
|
|
+.Sp
|
|
|
+Example: Replace the libev allocator with one that waits a bit and then
|
|
|
+retries (example requires a standards-compliant \f(CW\*(C`realloc\*(C'\fR).
|
|
|
+.Sp
|
|
|
+.Vb 6
|
|
|
+\& static void *
|
|
|
+\& persistent_realloc (void *ptr, size_t size)
|
|
|
+\& {
|
|
|
+\& for (;;)
|
|
|
+\& {
|
|
|
+\& void *newptr = realloc (ptr, size);
|
|
|
+\&
|
|
|
+\& if (newptr)
|
|
|
+\& return newptr;
|
|
|
+\&
|
|
|
+\& sleep (60);
|
|
|
+\& }
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ...
|
|
|
+\& ev_set_allocator (persistent_realloc);
|
|
|
+.Ve
|
|
|
+.IP "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())" 4
|
|
|
+.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())"
|
|
|
+Set the callback function to call on a retryable system call error (such
|
|
|
+as failed select, poll, epoll_wait). The message is a printable string
|
|
|
+indicating the system call or subsystem causing the problem. If this
|
|
|
+callback is set, then libev will expect it to remedy the situation, no
|
|
|
+matter what, when it returns. That is, libev will generally retry the
|
|
|
+requested operation, or, if the condition doesn't go away, do bad stuff
|
|
|
+(such as abort).
|
|
|
+.Sp
|
|
|
+Example: This is basically the same thing that libev does internally, too.
|
|
|
+.Sp
|
|
|
+.Vb 6
|
|
|
+\& static void
|
|
|
+\& fatal_error (const char *msg)
|
|
|
+\& {
|
|
|
+\& perror (msg);
|
|
|
+\& abort ();
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ...
|
|
|
+\& ev_set_syserr_cb (fatal_error);
|
|
|
+.Ve
|
|
|
+.IP "ev_feed_signal (int signum)" 4
|
|
|
+.IX Item "ev_feed_signal (int signum)"
|
|
|
+This function can be used to \*(L"simulate\*(R" a signal receive. It is completely
|
|
|
+safe to call this function at any time, from any context, including signal
|
|
|
+handlers or random threads.
|
|
|
+.Sp
|
|
|
+Its main use is to customise signal handling in your process, especially
|
|
|
+in the presence of threads. For example, you could block signals
|
|
|
+by default in all threads (and specifying \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when
|
|
|
+creating any loops), and in one thread, use \f(CW\*(C`sigwait\*(C'\fR or any other
|
|
|
+mechanism to wait for signals, then \*(L"deliver\*(R" them to libev by calling
|
|
|
+\&\f(CW\*(C`ev_feed_signal\*(C'\fR.
|
|
|
+.SH "FUNCTIONS CONTROLLING EVENT LOOPS"
|
|
|
+.IX Header "FUNCTIONS CONTROLLING EVENT LOOPS"
|
|
|
+An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR (the \f(CW\*(C`struct\*(C'\fR is
|
|
|
+\&\fInot\fR optional in this case unless libev 3 compatibility is disabled, as
|
|
|
+libev 3 had an \f(CW\*(C`ev_loop\*(C'\fR function colliding with the struct name).
|
|
|
+.PP
|
|
|
+The library knows two types of such loops, the \fIdefault\fR loop, which
|
|
|
+supports child process events, and dynamically created event loops which
|
|
|
+do not.
|
|
|
+.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4
|
|
|
+.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"
|
|
|
+This returns the \*(L"default\*(R" event loop object, which is what you should
|
|
|
+normally use when you just need \*(L"the event loop\*(R". Event loop objects and
|
|
|
+the \f(CW\*(C`flags\*(C'\fR parameter are described in more detail in the entry for
|
|
|
+\&\f(CW\*(C`ev_loop_new\*(C'\fR.
|
|
|
+.Sp
|
|
|
+If the default loop is already initialised then this function simply
|
|
|
+returns it (and ignores the flags. If that is troubling you, check
|
|
|
+\&\f(CW\*(C`ev_backend ()\*(C'\fR afterwards). Otherwise it will create it with the given
|
|
|
+flags, which should almost always be \f(CW0\fR, unless the caller is also the
|
|
|
+one calling \f(CW\*(C`ev_run\*(C'\fR or otherwise qualifies as \*(L"the main program\*(R".
|
|
|
+.Sp
|
|
|
+If you don't know what event loop to use, use the one returned from this
|
|
|
+function (or via the \f(CW\*(C`EV_DEFAULT\*(C'\fR macro).
|
|
|
+.Sp
|
|
|
+Note that this function is \fInot\fR thread-safe, so if you want to use it
|
|
|
+from multiple threads, you have to employ some kind of mutex (note also
|
|
|
+that this case is unlikely, as loops cannot be shared easily between
|
|
|
+threads anyway).
|
|
|
+.Sp
|
|
|
+The default loop is the only loop that can handle \f(CW\*(C`ev_child\*(C'\fR watchers,
|
|
|
+and to do this, it always registers a handler for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is
|
|
|
+a problem for your application you can either create a dynamic loop with
|
|
|
+\&\f(CW\*(C`ev_loop_new\*(C'\fR which doesn't do that, or you can simply overwrite the
|
|
|
+\&\f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling \f(CW\*(C`ev_default_init\*(C'\fR.
|
|
|
+.Sp
|
|
|
+Example: This is the most typical usage.
|
|
|
+.Sp
|
|
|
+.Vb 2
|
|
|
+\& if (!ev_default_loop (0))
|
|
|
+\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+Example: Restrict libev to the select and poll backends, and do not allow
|
|
|
+environment settings to be taken into account:
|
|
|
+.Sp
|
|
|
+.Vb 1
|
|
|
+\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
|
|
|
+.Ve
|
|
|
+.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
|
|
|
+.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
|
|
|
+This will create and initialise a new event loop object. If the loop
|
|
|
+could not be initialised, returns false.
|
|
|
+.Sp
|
|
|
+This function is thread-safe, and one common way to use libev with
|
|
|
+threads is indeed to create one loop per thread, and using the default
|
|
|
+loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread.
|
|
|
+.Sp
|
|
|
+The flags argument can be used to specify special behaviour or specific
|
|
|
+backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
|
|
|
+.Sp
|
|
|
+The following flags are supported:
|
|
|
+.RS 4
|
|
|
+.ie n .IP """EVFLAG_AUTO""" 4
|
|
|
+.el .IP "\f(CWEVFLAG_AUTO\fR" 4
|
|
|
+.IX Item "EVFLAG_AUTO"
|
|
|
+The default flags value. Use this if you have no clue (it's the right
|
|
|
+thing, believe me).
|
|
|
+.ie n .IP """EVFLAG_NOENV""" 4
|
|
|
+.el .IP "\f(CWEVFLAG_NOENV\fR" 4
|
|
|
+.IX Item "EVFLAG_NOENV"
|
|
|
+If this flag bit is or'ed into the flag value (or the program runs setuid
|
|
|
+or setgid) then libev will \fInot\fR look at the environment variable
|
|
|
+\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
|
|
|
+override the flags completely if it is found in the environment. This is
|
|
|
+useful to try out specific backends to test their performance, to work
|
|
|
+around bugs, or to make libev threadsafe (accessing environment variables
|
|
|
+cannot be done in a threadsafe way, but usually it works if no other
|
|
|
+thread modifies them).
|
|
|
+.ie n .IP """EVFLAG_FORKCHECK""" 4
|
|
|
+.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
|
|
|
+.IX Item "EVFLAG_FORKCHECK"
|
|
|
+Instead of calling \f(CW\*(C`ev_loop_fork\*(C'\fR manually after a fork, you can also
|
|
|
+make libev check for a fork in each iteration by enabling this flag.
|
|
|
+.Sp
|
|
|
+This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
|
|
|
+and thus this might slow down your event loop if you do a lot of loop
|
|
|
+iterations and little real work, but is usually not noticeable (on my
|
|
|
+GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
|
|
|
+without a system call and thus \fIvery\fR fast, but my GNU/Linux system also has
|
|
|
+\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
|
|
|
+.Sp
|
|
|
+The big advantage of this flag is that you can forget about fork (and
|
|
|
+forget about forgetting to tell libev about forking, although you still
|
|
|
+have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR) when you use this flag.
|
|
|
+.Sp
|
|
|
+This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
|
|
|
+environment variable.
|
|
|
+.ie n .IP """EVFLAG_NOINOTIFY""" 4
|
|
|
+.el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4
|
|
|
+.IX Item "EVFLAG_NOINOTIFY"
|
|
|
+When this flag is specified, then libev will not attempt to use the
|
|
|
+\&\fIinotify\fR \s-1API\s0 for its \f(CW\*(C`ev_stat\*(C'\fR watchers. Apart from debugging and
|
|
|
+testing, this flag can be useful to conserve inotify file descriptors, as
|
|
|
+otherwise each loop using \f(CW\*(C`ev_stat\*(C'\fR watchers consumes one inotify handle.
|
|
|
+.ie n .IP """EVFLAG_SIGNALFD""" 4
|
|
|
+.el .IP "\f(CWEVFLAG_SIGNALFD\fR" 4
|
|
|
+.IX Item "EVFLAG_SIGNALFD"
|
|
|
+When this flag is specified, then libev will attempt to use the
|
|
|
+\&\fIsignalfd\fR \s-1API\s0 for its \f(CW\*(C`ev_signal\*(C'\fR (and \f(CW\*(C`ev_child\*(C'\fR) watchers. This \s-1API\s0
|
|
|
+delivers signals synchronously, which makes it both faster and might make
|
|
|
+it possible to get the queued signal data. It can also simplify signal
|
|
|
+handling with threads, as long as you properly block signals in your
|
|
|
+threads that are not interested in handling them.
|
|
|
+.Sp
|
|
|
+Signalfd will not be used by default as this changes your signal mask, and
|
|
|
+there are a lot of shoddy libraries and programs (glib's threadpool for
|
|
|
+example) that can't properly initialise their signal masks.
|
|
|
+.ie n .IP """EVFLAG_NOSIGMASK""" 4
|
|
|
+.el .IP "\f(CWEVFLAG_NOSIGMASK\fR" 4
|
|
|
+.IX Item "EVFLAG_NOSIGMASK"
|
|
|
+When this flag is specified, then libev will avoid to modify the signal
|
|
|
+mask. Specifically, this means you have to make sure signals are unblocked
|
|
|
+when you want to receive them.
|
|
|
+.Sp
|
|
|
+This behaviour is useful when you want to do your own signal handling, or
|
|
|
+want to handle signals only in specific threads and want to avoid libev
|
|
|
+unblocking the signals.
|
|
|
+.Sp
|
|
|
+It's also required by \s-1POSIX\s0 in a threaded program, as libev calls
|
|
|
+\&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified.
|
|
|
+.Sp
|
|
|
+This flag's behaviour will become the default in future versions of libev.
|
|
|
+.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
|
|
|
+.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
|
|
|
+.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
|
|
|
+This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
|
|
|
+libev tries to roll its own fd_set with no limits on the number of fds,
|
|
|
+but if that fails, expect a fairly low limit on the number of fds when
|
|
|
+using this backend. It doesn't scale too well (O(highest_fd)), but its
|
|
|
+usually the fastest backend for a low number of (low-numbered :) fds.
|
|
|
+.Sp
|
|
|
+To get good performance out of this backend you need a high amount of
|
|
|
+parallelism (most of the file descriptors should be busy). If you are
|
|
|
+writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many
|
|
|
+connections as possible during one iteration. You might also want to have
|
|
|
+a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of
|
|
|
+readiness notifications you get per iteration.
|
|
|
+.Sp
|
|
|
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR to the \f(CW\*(C`readfds\*(C'\fR set and \f(CW\*(C`EV_WRITE\*(C'\fR to the
|
|
|
+\&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the
|
|
|
+\&\f(CW\*(C`exceptfds\*(C'\fR set on that platform).
|
|
|
+.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
|
|
|
+.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
|
|
|
+.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
|
|
|
+And this is your standard \fIpoll\fR\|(2) backend. It's more complicated
|
|
|
+than select, but handles sparse fds better and has no artificial
|
|
|
+limit on the number of fds you can use (except it will slow down
|
|
|
+considerably with a lot of inactive fds). It scales similarly to select,
|
|
|
+i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for
|
|
|
+performance tips.
|
|
|
+.Sp
|
|
|
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and
|
|
|
+\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR.
|
|
|
+.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
|
|
|
+.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
|
|
|
+.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
|
|
|
+Use the linux-specific \fIepoll\fR\|(7) interface (for both pre\- and post\-2.6.9
|
|
|
+kernels).
|
|
|
+.Sp
|
|
|
+For few fds, this backend is a bit little slower than poll and select, but
|
|
|
+it scales phenomenally better. While poll and select usually scale like
|
|
|
+O(total_fds) where total_fds is the total number of fds (or the highest
|
|
|
+fd), epoll scales either O(1) or O(active_fds).
|
|
|
+.Sp
|
|
|
+The epoll mechanism deserves honorable mention as the most misdesigned
|
|
|
+of the more advanced event mechanisms: mere annoyances include silently
|
|
|
+dropping file descriptors, requiring a system call per change per file
|
|
|
+descriptor (and unnecessary guessing of parameters), problems with dup,
|
|
|
+returning before the timeout value, resulting in additional iterations
|
|
|
+(and only giving 5ms accuracy while select on the same platform gives
|
|
|
+0.1ms) and so on. The biggest issue is fork races, however \- if a program
|
|
|
+forks then \fIboth\fR parent and child process have to recreate the epoll
|
|
|
+set, which can take considerable time (one syscall per file descriptor)
|
|
|
+and is of course hard to detect.
|
|
|
+.Sp
|
|
|
+Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work,
|
|
|
+but of course \fIdoesn't\fR, and epoll just loves to report events for
|
|
|
+totally \fIdifferent\fR file descriptors (even already closed ones, so
|
|
|
+one cannot even remove them from the set) than registered in the set
|
|
|
+(especially on \s-1SMP\s0 systems). Libev tries to counter these spurious
|
|
|
+notifications by employing an additional generation counter and comparing
|
|
|
+that against the events to filter out spurious ones, recreating the set
|
|
|
+when required. Epoll also erroneously rounds down timeouts, but gives you
|
|
|
+no way to know when and by how much, so sometimes you have to busy-wait
|
|
|
+because epoll returns immediately despite a nonzero timeout. And last
|
|
|
+not least, it also refuses to work with some file descriptors which work
|
|
|
+perfectly fine with \f(CW\*(C`select\*(C'\fR (files, many character devices...).
|
|
|
+.Sp
|
|
|
+Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
|
|
|
+cobbled together in a hurry, no thought to design or interaction with
|
|
|
+others. Oh, the pain, will it ever stop...
|
|
|
+.Sp
|
|
|
+While stopping, setting and starting an I/O watcher in the same iteration
|
|
|
+will result in some caching, there is still a system call per such
|
|
|
+incident (because the same \fIfile descriptor\fR could point to a different
|
|
|
+\&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed
|
|
|
+file descriptors might not work very well if you register events for both
|
|
|
+file descriptors.
|
|
|
+.Sp
|
|
|
+Best performance from this backend is achieved by not unregistering all
|
|
|
+watchers for a file descriptor until it has been closed, if possible,
|
|
|
+i.e. keep at least one watcher active per fd at all times. Stopping and
|
|
|
+starting a watcher (without re-setting it) also usually doesn't cause
|
|
|
+extra overhead. A fork can both result in spurious notifications as well
|
|
|
+as in libev having to destroy and recreate the epoll object, which can
|
|
|
+take considerable time and thus should be avoided.
|
|
|
+.Sp
|
|
|
+All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or
|
|
|
+faster than epoll for maybe up to a hundred file descriptors, depending on
|
|
|
+the usage. So sad.
|
|
|
+.Sp
|
|
|
+While nominally embeddable in other event loops, this feature is broken in
|
|
|
+all kernel versions tested so far.
|
|
|
+.Sp
|
|
|
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
|
|
|
+\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
|
|
|
+.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
|
|
|
+.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
|
|
|
+.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
|
|
|
+Kqueue deserves special mention, as at the time of this writing, it
|
|
|
+was broken on all BSDs except NetBSD (usually it doesn't work reliably
|
|
|
+with anything but sockets and pipes, except on Darwin, where of course
|
|
|
+it's completely useless). Unlike epoll, however, whose brokenness
|
|
|
+is by design, these kqueue bugs can (and eventually will) be fixed
|
|
|
+without \s-1API\s0 changes to existing programs. For this reason it's not being
|
|
|
+\&\*(L"auto-detected\*(R" unless you explicitly specify it in the flags (i.e. using
|
|
|
+\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough)
|
|
|
+system like NetBSD.
|
|
|
+.Sp
|
|
|
+You still can embed kqueue into a normal poll or select backend and use it
|
|
|
+only for sockets (after having made sure that sockets work with kqueue on
|
|
|
+the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
|
|
|
+.Sp
|
|
|
+It scales in the same way as the epoll backend, but the interface to the
|
|
|
+kernel is more efficient (which says nothing about its actual speed, of
|
|
|
+course). While stopping, setting and starting an I/O watcher does never
|
|
|
+cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
|
|
|
+two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you
|
|
|
+might have to leak fd's on fork, but it's more sane than epoll) and it
|
|
|
+drops fds silently in similarly hard-to-detect cases.
|
|
|
+.Sp
|
|
|
+This backend usually performs well under most conditions.
|
|
|
+.Sp
|
|
|
+While nominally embeddable in other event loops, this doesn't work
|
|
|
+everywhere, so you might need to test for this. And since it is broken
|
|
|
+almost everywhere, you should only use it when you have a lot of sockets
|
|
|
+(for which it usually works), by embedding it into another event loop
|
|
|
+(e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR (but \f(CW\*(C`poll\*(C'\fR is of course
|
|
|
+also broken on \s-1OS X\s0)) and, did I mention it, using it only for sockets.
|
|
|
+.Sp
|
|
|
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with
|
|
|
+\&\f(CW\*(C`NOTE_EOF\*(C'\fR, and \f(CW\*(C`EV_WRITE\*(C'\fR into an \f(CW\*(C`EVFILT_WRITE\*(C'\fR kevent with
|
|
|
+\&\f(CW\*(C`NOTE_EOF\*(C'\fR.
|
|
|
+.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
|
|
|
+.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
|
|
|
+.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
|
|
|
+This is not implemented yet (and might never be, unless you send me an
|
|
|
+implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets
|
|
|
+and is not embeddable, which would limit the usefulness of this backend
|
|
|
+immensely.
|
|
|
+.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
|
|
|
+.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
|
|
|
+.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
|
|
|
+This uses the Solaris 10 event port mechanism. As with everything on Solaris,
|
|
|
+it's really slow, but it still scales very well (O(active_fds)).
|
|
|
+.Sp
|
|
|
+While this backend scales well, it requires one system call per active
|
|
|
+file descriptor per loop iteration. For small and medium numbers of file
|
|
|
+descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend
|
|
|
+might perform better.
|
|
|
+.Sp
|
|
|
+On the positive side, this backend actually performed fully to
|
|
|
+specification in all tests and is fully embeddable, which is a rare feat
|
|
|
+among the OS-specific backends (I vastly prefer correctness over speed
|
|
|
+hacks).
|
|
|
+.Sp
|
|
|
+On the negative side, the interface is \fIbizarre\fR \- so bizarre that
|
|
|
+even sun itself gets it wrong in their code examples: The event polling
|
|
|
+function sometimes returns events to the caller even though an error
|
|
|
+occurred, but with no indication whether it has done so or not (yes, it's
|
|
|
+even documented that way) \- deadly for edge-triggered interfaces where you
|
|
|
+absolutely have to know whether an event occurred or not because you have
|
|
|
+to re-arm the watcher.
|
|
|
+.Sp
|
|
|
+Fortunately libev seems to be able to work around these idiocies.
|
|
|
+.Sp
|
|
|
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
|
|
|
+\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
|
|
|
+.ie n .IP """EVBACKEND_ALL""" 4
|
|
|
+.el .IP "\f(CWEVBACKEND_ALL\fR" 4
|
|
|
+.IX Item "EVBACKEND_ALL"
|
|
|
+Try all backends (even potentially broken ones that wouldn't be tried
|
|
|
+with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
|
|
|
+\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.
|
|
|
+.Sp
|
|
|
+It is definitely not recommended to use this flag, use whatever
|
|
|
+\&\f(CW\*(C`ev_recommended_backends ()\*(C'\fR returns, or simply do not specify a backend
|
|
|
+at all.
|
|
|
+.ie n .IP """EVBACKEND_MASK""" 4
|
|
|
+.el .IP "\f(CWEVBACKEND_MASK\fR" 4
|
|
|
+.IX Item "EVBACKEND_MASK"
|
|
|
+Not a backend at all, but a mask to select all backend bits from a
|
|
|
+\&\f(CW\*(C`flags\*(C'\fR value, in case you want to mask out any backends from a flags
|
|
|
+value (e.g. when modifying the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR environment variable).
|
|
|
+.RE
|
|
|
+.RS 4
|
|
|
+.Sp
|
|
|
+If one or more of the backend flags are or'ed into the flags value,
|
|
|
+then only these backends will be tried (in the reverse order as listed
|
|
|
+here). If none are specified, all backends in \f(CW\*(C`ev_recommended_backends
|
|
|
+()\*(C'\fR will be tried.
|
|
|
+.Sp
|
|
|
+Example: Try to create a event loop that uses epoll and nothing else.
|
|
|
+.Sp
|
|
|
+.Vb 3
|
|
|
+\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
|
|
|
+\& if (!epoller)
|
|
|
+\& fatal ("no epoll found here, maybe it hides under your chair");
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+Example: Use whatever libev has to offer, but make sure that kqueue is
|
|
|
+used if available.
|
|
|
+.Sp
|
|
|
+.Vb 1
|
|
|
+\& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
|
|
|
+.Ve
|
|
|
+.RE
|
|
|
+.IP "ev_loop_destroy (loop)" 4
|
|
|
+.IX Item "ev_loop_destroy (loop)"
|
|
|
+Destroys an event loop object (frees all memory and kernel state
|
|
|
+etc.). None of the active event watchers will be stopped in the normal
|
|
|
+sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
|
|
|
+responsibility to either stop all watchers cleanly yourself \fIbefore\fR
|
|
|
+calling this function, or cope with the fact afterwards (which is usually
|
|
|
+the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
|
|
|
+for example).
|
|
|
+.Sp
|
|
|
+Note that certain global state, such as signal state (and installed signal
|
|
|
+handlers), will not be freed by this function, and related watchers (such
|
|
|
+as signal and child watchers) would need to be stopped manually.
|
|
|
+.Sp
|
|
|
+This function is normally used on loop objects allocated by
|
|
|
+\&\f(CW\*(C`ev_loop_new\*(C'\fR, but it can also be used on the default loop returned by
|
|
|
+\&\f(CW\*(C`ev_default_loop\*(C'\fR, in which case it is not thread-safe.
|
|
|
+.Sp
|
|
|
+Note that it is not advisable to call this function on the default loop
|
|
|
+except in the rare occasion where you really need to free its resources.
|
|
|
+If you need dynamically allocated loops it is better to use \f(CW\*(C`ev_loop_new\*(C'\fR
|
|
|
+and \f(CW\*(C`ev_loop_destroy\*(C'\fR.
|
|
|
+.IP "ev_loop_fork (loop)" 4
|
|
|
+.IX Item "ev_loop_fork (loop)"
|
|
|
+This function sets a flag that causes subsequent \f(CW\*(C`ev_run\*(C'\fR iterations
|
|
|
+to reinitialise the kernel state for backends that have one. Despite
|
|
|
+the name, you can call it anytime you are allowed to start or stop
|
|
|
+watchers (except inside an \f(CW\*(C`ev_prepare\*(C'\fR callback), but it makes most
|
|
|
+sense after forking, in the child process. You \fImust\fR call it (or use
|
|
|
+\&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR) in the child before resuming or calling \f(CW\*(C`ev_run\*(C'\fR.
|
|
|
+.Sp
|
|
|
+In addition, if you want to reuse a loop (via this function or
|
|
|
+\&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR), you \fIalso\fR have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR.
|
|
|
+.Sp
|
|
|
+Again, you \fIhave\fR to call it on \fIany\fR loop that you want to re-use after
|
|
|
+a fork, \fIeven if you do not plan to use the loop in the parent\fR. This is
|
|
|
+because some kernel interfaces *cough* \fIkqueue\fR *cough* do funny things
|
|
|
+during fork.
|
|
|
+.Sp
|
|
|
+On the other hand, you only need to call this function in the child
|
|
|
+process if and only if you want to use the event loop in the child. If
|
|
|
+you just fork+exec or create a new loop in the child, you don't have to
|
|
|
+call it at all (in fact, \f(CW\*(C`epoll\*(C'\fR is so badly broken that it makes a
|
|
|
+difference, but libev will usually detect this case on its own and do a
|
|
|
+costly reset of the backend).
|
|
|
+.Sp
|
|
|
+The function itself is quite fast and it's usually not a problem to call
|
|
|
+it just in case after a fork.
|
|
|
+.Sp
|
|
|
+Example: Automate calling \f(CW\*(C`ev_loop_fork\*(C'\fR on the default loop when
|
|
|
+using pthreads.
|
|
|
+.Sp
|
|
|
+.Vb 5
|
|
|
+\& static void
|
|
|
+\& post_fork_child (void)
|
|
|
+\& {
|
|
|
+\& ev_loop_fork (EV_DEFAULT);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ...
|
|
|
+\& pthread_atfork (0, 0, post_fork_child);
|
|
|
+.Ve
|
|
|
+.IP "int ev_is_default_loop (loop)" 4
|
|
|
+.IX Item "int ev_is_default_loop (loop)"
|
|
|
+Returns true when the given loop is, in fact, the default loop, and false
|
|
|
+otherwise.
|
|
|
+.IP "unsigned int ev_iteration (loop)" 4
|
|
|
+.IX Item "unsigned int ev_iteration (loop)"
|
|
|
+Returns the current iteration count for the event loop, which is identical
|
|
|
+to the number of times libev did poll for new events. It starts at \f(CW0\fR
|
|
|
+and happily wraps around with enough iterations.
|
|
|
+.Sp
|
|
|
+This value can sometimes be useful as a generation counter of sorts (it
|
|
|
+\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
|
|
|
+\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls \- and is incremented between the
|
|
|
+prepare and check phases.
|
|
|
+.IP "unsigned int ev_depth (loop)" 4
|
|
|
+.IX Item "unsigned int ev_depth (loop)"
|
|
|
+Returns the number of times \f(CW\*(C`ev_run\*(C'\fR was entered minus the number of
|
|
|
+times \f(CW\*(C`ev_run\*(C'\fR was exited normally, in other words, the recursion depth.
|
|
|
+.Sp
|
|
|
+Outside \f(CW\*(C`ev_run\*(C'\fR, this number is zero. In a callback, this number is
|
|
|
+\&\f(CW1\fR, unless \f(CW\*(C`ev_run\*(C'\fR was invoked recursively (or from another thread),
|
|
|
+in which case it is higher.
|
|
|
+.Sp
|
|
|
+Leaving \f(CW\*(C`ev_run\*(C'\fR abnormally (setjmp/longjmp, cancelling the thread,
|
|
|
+throwing an exception etc.), doesn't count as \*(L"exit\*(R" \- consider this
|
|
|
+as a hint to avoid such ungentleman-like behaviour unless it's really
|
|
|
+convenient, in which case it is fully supported.
|
|
|
+.IP "unsigned int ev_backend (loop)" 4
|
|
|
+.IX Item "unsigned int ev_backend (loop)"
|
|
|
+Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
|
|
|
+use.
|
|
|
+.IP "ev_tstamp ev_now (loop)" 4
|
|
|
+.IX Item "ev_tstamp ev_now (loop)"
|
|
|
+Returns the current \*(L"event loop time\*(R", which is the time the event loop
|
|
|
+received events and started processing them. This timestamp does not
|
|
|
+change as long as callbacks are being processed, and this is also the base
|
|
|
+time used for relative timers. You can treat it as the timestamp of the
|
|
|
+event occurring (or more correctly, libev finding out about it).
|
|
|
+.IP "ev_now_update (loop)" 4
|
|
|
+.IX Item "ev_now_update (loop)"
|
|
|
+Establishes the current time by querying the kernel, updating the time
|
|
|
+returned by \f(CW\*(C`ev_now ()\*(C'\fR in the progress. This is a costly operation and
|
|
|
+is usually done automatically within \f(CW\*(C`ev_run ()\*(C'\fR.
|
|
|
+.Sp
|
|
|
+This function is rarely useful, but when some event callback runs for a
|
|
|
+very long time without entering the event loop, updating libev's idea of
|
|
|
+the current time is a good idea.
|
|
|
+.Sp
|
|
|
+See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section.
|
|
|
+.IP "ev_suspend (loop)" 4
|
|
|
+.IX Item "ev_suspend (loop)"
|
|
|
+.PD 0
|
|
|
+.IP "ev_resume (loop)" 4
|
|
|
+.IX Item "ev_resume (loop)"
|
|
|
+.PD
|
|
|
+These two functions suspend and resume an event loop, for use when the
|
|
|
+loop is not used for a while and timeouts should not be processed.
|
|
|
+.Sp
|
|
|
+A typical use case would be an interactive program such as a game: When
|
|
|
+the user presses \f(CW\*(C`^Z\*(C'\fR to suspend the game and resumes it an hour later it
|
|
|
+would be best to handle timeouts as if no time had actually passed while
|
|
|
+the program was suspended. This can be achieved by calling \f(CW\*(C`ev_suspend\*(C'\fR
|
|
|
+in your \f(CW\*(C`SIGTSTP\*(C'\fR handler, sending yourself a \f(CW\*(C`SIGSTOP\*(C'\fR and calling
|
|
|
+\&\f(CW\*(C`ev_resume\*(C'\fR directly afterwards to resume timer processing.
|
|
|
+.Sp
|
|
|
+Effectively, all \f(CW\*(C`ev_timer\*(C'\fR watchers will be delayed by the time spend
|
|
|
+between \f(CW\*(C`ev_suspend\*(C'\fR and \f(CW\*(C`ev_resume\*(C'\fR, and all \f(CW\*(C`ev_periodic\*(C'\fR watchers
|
|
|
+will be rescheduled (that is, they will lose any events that would have
|
|
|
+occurred while suspended).
|
|
|
+.Sp
|
|
|
+After calling \f(CW\*(C`ev_suspend\*(C'\fR you \fBmust not\fR call \fIany\fR function on the
|
|
|
+given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR
|
|
|
+without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR.
|
|
|
+.Sp
|
|
|
+Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the
|
|
|
+event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR).
|
|
|
+.IP "bool ev_run (loop, int flags)" 4
|
|
|
+.IX Item "bool ev_run (loop, int flags)"
|
|
|
+Finally, this is it, the event handler. This function usually is called
|
|
|
+after you have initialised all your watchers and you want to start
|
|
|
+handling events. It will ask the operating system for any new events, call
|
|
|
+the watcher callbacks, and then repeat the whole process indefinitely: This
|
|
|
+is why event loops are called \fIloops\fR.
|
|
|
+.Sp
|
|
|
+If the flags argument is specified as \f(CW0\fR, it will keep handling events
|
|
|
+until either no event watchers are active anymore or \f(CW\*(C`ev_break\*(C'\fR was
|
|
|
+called.
|
|
|
+.Sp
|
|
|
+The return value is false if there are no more active watchers (which
|
|
|
+usually means \*(L"all jobs done\*(R" or \*(L"deadlock\*(R"), and true in all other cases
|
|
|
+(which usually means " you should call \f(CW\*(C`ev_run\*(C'\fR again").
|
|
|
+.Sp
|
|
|
+Please note that an explicit \f(CW\*(C`ev_break\*(C'\fR is usually better than
|
|
|
+relying on all watchers to be stopped when deciding when a program has
|
|
|
+finished (especially in interactive programs), but having a program
|
|
|
+that automatically loops as long as it has to and no longer by virtue
|
|
|
+of relying on its watchers stopping correctly, that is truly a thing of
|
|
|
+beauty.
|
|
|
+.Sp
|
|
|
+This function is \fImostly\fR exception-safe \- you can break out of a
|
|
|
+\&\f(CW\*(C`ev_run\*(C'\fR call by calling \f(CW\*(C`longjmp\*(C'\fR in a callback, throwing a \*(C+
|
|
|
+exception and so on. This does not decrement the \f(CW\*(C`ev_depth\*(C'\fR value, nor
|
|
|
+will it clear any outstanding \f(CW\*(C`EVBREAK_ONE\*(C'\fR breaks.
|
|
|
+.Sp
|
|
|
+A flags value of \f(CW\*(C`EVRUN_NOWAIT\*(C'\fR will look for new events, will handle
|
|
|
+those events and any already outstanding ones, but will not wait and
|
|
|
+block your process in case there are no events and will return after one
|
|
|
+iteration of the loop. This is sometimes useful to poll and handle new
|
|
|
+events while doing lengthy calculations, to keep the program responsive.
|
|
|
+.Sp
|
|
|
+A flags value of \f(CW\*(C`EVRUN_ONCE\*(C'\fR will look for new events (waiting if
|
|
|
+necessary) and will handle those and any already outstanding ones. It
|
|
|
+will block your process until at least one new event arrives (which could
|
|
|
+be an event internal to libev itself, so there is no guarantee that a
|
|
|
+user-registered callback will be called), and will return after one
|
|
|
+iteration of the loop.
|
|
|
+.Sp
|
|
|
+This is useful if you are waiting for some external event in conjunction
|
|
|
+with something not expressible using other libev watchers (i.e. "roll your
|
|
|
+own \f(CW\*(C`ev_run\*(C'\fR"). However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
|
|
|
+usually a better approach for this kind of thing.
|
|
|
+.Sp
|
|
|
+Here are the gory details of what \f(CW\*(C`ev_run\*(C'\fR does (this is for your
|
|
|
+understanding, not a guarantee that things will work exactly like this in
|
|
|
+future versions):
|
|
|
+.Sp
|
|
|
+.Vb 10
|
|
|
+\& \- Increment loop depth.
|
|
|
+\& \- Reset the ev_break status.
|
|
|
+\& \- Before the first iteration, call any pending watchers.
|
|
|
+\& LOOP:
|
|
|
+\& \- If EVFLAG_FORKCHECK was used, check for a fork.
|
|
|
+\& \- If a fork was detected (by any means), queue and call all fork watchers.
|
|
|
+\& \- Queue and call all prepare watchers.
|
|
|
+\& \- If ev_break was called, goto FINISH.
|
|
|
+\& \- If we have been forked, detach and recreate the kernel state
|
|
|
+\& as to not disturb the other process.
|
|
|
+\& \- Update the kernel state with all outstanding changes.
|
|
|
+\& \- Update the "event loop time" (ev_now ()).
|
|
|
+\& \- Calculate for how long to sleep or block, if at all
|
|
|
+\& (active idle watchers, EVRUN_NOWAIT or not having
|
|
|
+\& any active watchers at all will result in not sleeping).
|
|
|
+\& \- Sleep if the I/O and timer collect interval say so.
|
|
|
+\& \- Increment loop iteration counter.
|
|
|
+\& \- Block the process, waiting for any events.
|
|
|
+\& \- Queue all outstanding I/O (fd) events.
|
|
|
+\& \- Update the "event loop time" (ev_now ()), and do time jump adjustments.
|
|
|
+\& \- Queue all expired timers.
|
|
|
+\& \- Queue all expired periodics.
|
|
|
+\& \- Queue all idle watchers with priority higher than that of pending events.
|
|
|
+\& \- Queue all check watchers.
|
|
|
+\& \- Call all queued watchers in reverse order (i.e. check watchers first).
|
|
|
+\& Signals and child watchers are implemented as I/O watchers, and will
|
|
|
+\& be handled here by queueing them when their watcher gets executed.
|
|
|
+\& \- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
|
|
|
+\& were used, or there are no active watchers, goto FINISH, otherwise
|
|
|
+\& continue with step LOOP.
|
|
|
+\& FINISH:
|
|
|
+\& \- Reset the ev_break status iff it was EVBREAK_ONE.
|
|
|
+\& \- Decrement the loop depth.
|
|
|
+\& \- Return.
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+Example: Queue some jobs and then loop until no events are outstanding
|
|
|
+anymore.
|
|
|
+.Sp
|
|
|
+.Vb 4
|
|
|
+\& ... queue jobs here, make sure they register event watchers as long
|
|
|
+\& ... as they still have work to do (even an idle watcher will do..)
|
|
|
+\& ev_run (my_loop, 0);
|
|
|
+\& ... jobs done or somebody called break. yeah!
|
|
|
+.Ve
|
|
|
+.IP "ev_break (loop, how)" 4
|
|
|
+.IX Item "ev_break (loop, how)"
|
|
|
+Can be used to make a call to \f(CW\*(C`ev_run\*(C'\fR return early (but only after it
|
|
|
+has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
|
|
|
+\&\f(CW\*(C`EVBREAK_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_run\*(C'\fR call return, or
|
|
|
+\&\f(CW\*(C`EVBREAK_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_run\*(C'\fR calls return.
|
|
|
+.Sp
|
|
|
+This \*(L"break state\*(R" will be cleared on the next call to \f(CW\*(C`ev_run\*(C'\fR.
|
|
|
+.Sp
|
|
|
+It is safe to call \f(CW\*(C`ev_break\*(C'\fR from outside any \f(CW\*(C`ev_run\*(C'\fR calls, too, in
|
|
|
+which case it will have no effect.
|
|
|
+.IP "ev_ref (loop)" 4
|
|
|
+.IX Item "ev_ref (loop)"
|
|
|
+.PD 0
|
|
|
+.IP "ev_unref (loop)" 4
|
|
|
+.IX Item "ev_unref (loop)"
|
|
|
+.PD
|
|
|
+Ref/unref can be used to add or remove a reference count on the event
|
|
|
+loop: Every watcher keeps one reference, and as long as the reference
|
|
|
+count is nonzero, \f(CW\*(C`ev_run\*(C'\fR will not return on its own.
|
|
|
+.Sp
|
|
|
+This is useful when you have a watcher that you never intend to
|
|
|
+unregister, but that nevertheless should not keep \f(CW\*(C`ev_run\*(C'\fR from
|
|
|
+returning. In such a case, call \f(CW\*(C`ev_unref\*(C'\fR after starting, and \f(CW\*(C`ev_ref\*(C'\fR
|
|
|
+before stopping it.
|
|
|
+.Sp
|
|
|
+As an example, libev itself uses this for its internal signal pipe: It
|
|
|
+is not visible to the libev user and should not keep \f(CW\*(C`ev_run\*(C'\fR from
|
|
|
+exiting if no event watchers registered by it are active. It is also an
|
|
|
+excellent way to do this for generic recurring timers or from within
|
|
|
+third-party libraries. Just remember to \fIunref after start\fR and \fIref
|
|
|
+before stop\fR (but only if the watcher wasn't active before, or was active
|
|
|
+before, respectively. Note also that libev might stop watchers itself
|
|
|
+(e.g. non-repeating timers) in which case you have to \f(CW\*(C`ev_ref\*(C'\fR
|
|
|
+in the callback).
|
|
|
+.Sp
|
|
|
+Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_run\*(C'\fR
|
|
|
+running when nothing else is active.
|
|
|
+.Sp
|
|
|
+.Vb 4
|
|
|
+\& ev_signal exitsig;
|
|
|
+\& ev_signal_init (&exitsig, sig_cb, SIGINT);
|
|
|
+\& ev_signal_start (loop, &exitsig);
|
|
|
+\& ev_unref (loop);
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+Example: For some weird reason, unregister the above signal handler again.
|
|
|
+.Sp
|
|
|
+.Vb 2
|
|
|
+\& ev_ref (loop);
|
|
|
+\& ev_signal_stop (loop, &exitsig);
|
|
|
+.Ve
|
|
|
+.IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4
|
|
|
+.IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)"
|
|
|
+.PD 0
|
|
|
+.IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4
|
|
|
+.IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)"
|
|
|
+.PD
|
|
|
+These advanced functions influence the time that libev will spend waiting
|
|
|
+for events. Both time intervals are by default \f(CW0\fR, meaning that libev
|
|
|
+will try to invoke timer/periodic callbacks and I/O callbacks with minimum
|
|
|
+latency.
|
|
|
+.Sp
|
|
|
+Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR)
|
|
|
+allows libev to delay invocation of I/O and timer/periodic callbacks
|
|
|
+to increase efficiency of loop iterations (or to increase power-saving
|
|
|
+opportunities).
|
|
|
+.Sp
|
|
|
+The idea is that sometimes your program runs just fast enough to handle
|
|
|
+one (or very few) event(s) per loop iteration. While this makes the
|
|
|
+program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
|
|
|
+events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high
|
|
|
+overhead for the actual polling but can deliver many events at once.
|
|
|
+.Sp
|
|
|
+By setting a higher \fIio collect interval\fR you allow libev to spend more
|
|
|
+time collecting I/O events, so you can handle more events per iteration,
|
|
|
+at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and
|
|
|
+\&\f(CW\*(C`ev_timer\*(C'\fR) will not be affected. Setting this to a non-null value will
|
|
|
+introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. The
|
|
|
+sleep time ensures that libev will not poll for I/O events more often then
|
|
|
+once per this interval, on average (as long as the host time resolution is
|
|
|
+good enough).
|
|
|
+.Sp
|
|
|
+Likewise, by setting a higher \fItimeout collect interval\fR you allow libev
|
|
|
+to spend more time collecting timeouts, at the expense of increased
|
|
|
+latency/jitter/inexactness (the watcher callback will be called
|
|
|
+later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null
|
|
|
+value will not introduce any overhead in libev.
|
|
|
+.Sp
|
|
|
+Many (busy) programs can usually benefit by setting the I/O collect
|
|
|
+interval to a value near \f(CW0.1\fR or so, which is often enough for
|
|
|
+interactive servers (of course not for games), likewise for timeouts. It
|
|
|
+usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR,
|
|
|
+as this approaches the timing granularity of most systems. Note that if
|
|
|
+you do transactions with the outside world and you can't increase the
|
|
|
+parallelity, then this setting will limit your transaction rate (if you
|
|
|
+need to poll once per transaction and the I/O collect interval is 0.01,
|
|
|
+then you can't do more than 100 transactions per second).
|
|
|
+.Sp
|
|
|
+Setting the \fItimeout collect interval\fR can improve the opportunity for
|
|
|
+saving power, as the program will \*(L"bundle\*(R" timer callback invocations that
|
|
|
+are \*(L"near\*(R" in time together, by delaying some, thus reducing the number of
|
|
|
+times the process sleeps and wakes up again. Another useful technique to
|
|
|
+reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure
|
|
|
+they fire on, say, one-second boundaries only.
|
|
|
+.Sp
|
|
|
+Example: we only need 0.1s timeout granularity, and we wish not to poll
|
|
|
+more often than 100 times per second:
|
|
|
+.Sp
|
|
|
+.Vb 2
|
|
|
+\& ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
|
|
|
+\& ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
|
|
|
+.Ve
|
|
|
+.IP "ev_invoke_pending (loop)" 4
|
|
|
+.IX Item "ev_invoke_pending (loop)"
|
|
|
+This call will simply invoke all pending watchers while resetting their
|
|
|
+pending state. Normally, \f(CW\*(C`ev_run\*(C'\fR does this automatically when required,
|
|
|
+but when overriding the invoke callback this call comes handy. This
|
|
|
+function can be invoked from a watcher \- this can be useful for example
|
|
|
+when you want to do some lengthy calculation and want to pass further
|
|
|
+event handling to another thread (you still have to make sure only one
|
|
|
+thread executes within \f(CW\*(C`ev_invoke_pending\*(C'\fR or \f(CW\*(C`ev_run\*(C'\fR of course).
|
|
|
+.IP "int ev_pending_count (loop)" 4
|
|
|
+.IX Item "int ev_pending_count (loop)"
|
|
|
+Returns the number of pending watchers \- zero indicates that no watchers
|
|
|
+are pending.
|
|
|
+.IP "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(\s-1EV_P\s0))" 4
|
|
|
+.IX Item "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))"
|
|
|
+This overrides the invoke pending functionality of the loop: Instead of
|
|
|
+invoking all pending watchers when there are any, \f(CW\*(C`ev_run\*(C'\fR will call
|
|
|
+this callback instead. This is useful, for example, when you want to
|
|
|
+invoke the actual watchers inside another context (another thread etc.).
|
|
|
+.Sp
|
|
|
+If you want to reset the callback, use \f(CW\*(C`ev_invoke_pending\*(C'\fR as new
|
|
|
+callback.
|
|
|
+.IP "ev_set_loop_release_cb (loop, void (*release)(\s-1EV_P\s0) throw (), void (*acquire)(\s-1EV_P\s0) throw ())" 4
|
|
|
+.IX Item "ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())"
|
|
|
+Sometimes you want to share the same loop between multiple threads. This
|
|
|
+can be done relatively simply by putting mutex_lock/unlock calls around
|
|
|
+each call to a libev function.
|
|
|
+.Sp
|
|
|
+However, \f(CW\*(C`ev_run\*(C'\fR can run an indefinite time, so it is not feasible
|
|
|
+to wait for it to return. One way around this is to wake up the event
|
|
|
+loop via \f(CW\*(C`ev_break\*(C'\fR and \f(CW\*(C`ev_async_send\*(C'\fR, another way is to set these
|
|
|
+\&\fIrelease\fR and \fIacquire\fR callbacks on the loop.
|
|
|
+.Sp
|
|
|
+When set, then \f(CW\*(C`release\*(C'\fR will be called just before the thread is
|
|
|
+suspended waiting for new events, and \f(CW\*(C`acquire\*(C'\fR is called just
|
|
|
+afterwards.
|
|
|
+.Sp
|
|
|
+Ideally, \f(CW\*(C`release\*(C'\fR will just call your mutex_unlock function, and
|
|
|
+\&\f(CW\*(C`acquire\*(C'\fR will just call the mutex_lock function again.
|
|
|
+.Sp
|
|
|
+While event loop modifications are allowed between invocations of
|
|
|
+\&\f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR (that's their only purpose after all), no
|
|
|
+modifications done will affect the event loop, i.e. adding watchers will
|
|
|
+have no effect on the set of file descriptors being watched, or the time
|
|
|
+waited. Use an \f(CW\*(C`ev_async\*(C'\fR watcher to wake up \f(CW\*(C`ev_run\*(C'\fR when you want it
|
|
|
+to take note of any changes you made.
|
|
|
+.Sp
|
|
|
+In theory, threads executing \f(CW\*(C`ev_run\*(C'\fR will be async-cancel safe between
|
|
|
+invocations of \f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR.
|
|
|
+.Sp
|
|
|
+See also the locking example in the \f(CW\*(C`THREADS\*(C'\fR section later in this
|
|
|
+document.
|
|
|
+.IP "ev_set_userdata (loop, void *data)" 4
|
|
|
+.IX Item "ev_set_userdata (loop, void *data)"
|
|
|
+.PD 0
|
|
|
+.IP "void *ev_userdata (loop)" 4
|
|
|
+.IX Item "void *ev_userdata (loop)"
|
|
|
+.PD
|
|
|
+Set and retrieve a single \f(CW\*(C`void *\*(C'\fR associated with a loop. When
|
|
|
+\&\f(CW\*(C`ev_set_userdata\*(C'\fR has never been called, then \f(CW\*(C`ev_userdata\*(C'\fR returns
|
|
|
+\&\f(CW0\fR.
|
|
|
+.Sp
|
|
|
+These two functions can be used to associate arbitrary data with a loop,
|
|
|
+and are intended solely for the \f(CW\*(C`invoke_pending_cb\*(C'\fR, \f(CW\*(C`release\*(C'\fR and
|
|
|
+\&\f(CW\*(C`acquire\*(C'\fR callbacks described above, but of course can be (ab\-)used for
|
|
|
+any other purpose as well.
|
|
|
+.IP "ev_verify (loop)" 4
|
|
|
+.IX Item "ev_verify (loop)"
|
|
|
+This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been
|
|
|
+compiled in, which is the default for non-minimal builds. It tries to go
|
|
|
+through all internal structures and checks them for validity. If anything
|
|
|
+is found to be inconsistent, it will print an error message to standard
|
|
|
+error and call \f(CW\*(C`abort ()\*(C'\fR.
|
|
|
+.Sp
|
|
|
+This can be used to catch bugs inside libev itself: under normal
|
|
|
+circumstances, this function will never abort as of course libev keeps its
|
|
|
+data structures consistent.
|
|
|
+.SH "ANATOMY OF A WATCHER"
|
|
|
+.IX Header "ANATOMY OF A WATCHER"
|
|
|
+In the following description, uppercase \f(CW\*(C`TYPE\*(C'\fR in names stands for the
|
|
|
+watcher type, e.g. \f(CW\*(C`ev_TYPE_start\*(C'\fR can mean \f(CW\*(C`ev_timer_start\*(C'\fR for timer
|
|
|
+watchers and \f(CW\*(C`ev_io_start\*(C'\fR for I/O watchers.
|
|
|
+.PP
|
|
|
+A watcher is an opaque structure that you allocate and register to record
|
|
|
+your interest in some event. To make a concrete example, imagine you want
|
|
|
+to wait for \s-1STDIN\s0 to become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher
|
|
|
+for that:
|
|
|
+.PP
|
|
|
+.Vb 5
|
|
|
+\& static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
|
|
|
+\& {
|
|
|
+\& ev_io_stop (w);
|
|
|
+\& ev_break (loop, EVBREAK_ALL);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& struct ev_loop *loop = ev_default_loop (0);
|
|
|
+\&
|
|
|
+\& ev_io stdin_watcher;
|
|
|
+\&
|
|
|
+\& ev_init (&stdin_watcher, my_cb);
|
|
|
+\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
|
|
|
+\& ev_io_start (loop, &stdin_watcher);
|
|
|
+\&
|
|
|
+\& ev_run (loop, 0);
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+As you can see, you are responsible for allocating the memory for your
|
|
|
+watcher structures (and it is \fIusually\fR a bad idea to do this on the
|
|
|
+stack).
|
|
|
+.PP
|
|
|
+Each watcher has an associated watcher structure (called \f(CW\*(C`struct ev_TYPE\*(C'\fR
|
|
|
+or simply \f(CW\*(C`ev_TYPE\*(C'\fR, as typedefs are provided for all watcher structs).
|
|
|
+.PP
|
|
|
+Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init (watcher
|
|
|
+*, callback)\*(C'\fR, which expects a callback to be provided. This callback is
|
|
|
+invoked each time the event occurs (or, in the case of I/O watchers, each
|
|
|
+time the event loop detects that the file descriptor given is readable
|
|
|
+and/or writable).
|
|
|
+.PP
|
|
|
+Each watcher type further has its own \f(CW\*(C`ev_TYPE_set (watcher *, ...)\*(C'\fR
|
|
|
+macro to configure it, with arguments specific to the watcher type. There
|
|
|
+is also a macro to combine initialisation and setting in one call: \f(CW\*(C`ev_TYPE_init (watcher *, callback, ...)\*(C'\fR.
|
|
|
+.PP
|
|
|
+To make the watcher actually watch out for events, you have to start it
|
|
|
+with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher
|
|
|
+*)\*(C'\fR), and you can stop watching for events at any time by calling the
|
|
|
+corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR.
|
|
|
+.PP
|
|
|
+As long as your watcher is active (has been started but not stopped) you
|
|
|
+must not touch the values stored in it. Most specifically you must never
|
|
|
+reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro.
|
|
|
+.PP
|
|
|
+Each and every callback receives the event loop pointer as first, the
|
|
|
+registered watcher structure as second, and a bitset of received events as
|
|
|
+third argument.
|
|
|
+.PP
|
|
|
+The received events usually include a single bit per event type received
|
|
|
+(you can receive multiple events at the same time). The possible bit masks
|
|
|
+are:
|
|
|
+.ie n .IP """EV_READ""" 4
|
|
|
+.el .IP "\f(CWEV_READ\fR" 4
|
|
|
+.IX Item "EV_READ"
|
|
|
+.PD 0
|
|
|
+.ie n .IP """EV_WRITE""" 4
|
|
|
+.el .IP "\f(CWEV_WRITE\fR" 4
|
|
|
+.IX Item "EV_WRITE"
|
|
|
+.PD
|
|
|
+The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or
|
|
|
+writable.
|
|
|
+.ie n .IP """EV_TIMER""" 4
|
|
|
+.el .IP "\f(CWEV_TIMER\fR" 4
|
|
|
+.IX Item "EV_TIMER"
|
|
|
+The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out.
|
|
|
+.ie n .IP """EV_PERIODIC""" 4
|
|
|
+.el .IP "\f(CWEV_PERIODIC\fR" 4
|
|
|
+.IX Item "EV_PERIODIC"
|
|
|
+The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out.
|
|
|
+.ie n .IP """EV_SIGNAL""" 4
|
|
|
+.el .IP "\f(CWEV_SIGNAL\fR" 4
|
|
|
+.IX Item "EV_SIGNAL"
|
|
|
+The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
|
|
|
+.ie n .IP """EV_CHILD""" 4
|
|
|
+.el .IP "\f(CWEV_CHILD\fR" 4
|
|
|
+.IX Item "EV_CHILD"
|
|
|
+The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
|
|
|
+.ie n .IP """EV_STAT""" 4
|
|
|
+.el .IP "\f(CWEV_STAT\fR" 4
|
|
|
+.IX Item "EV_STAT"
|
|
|
+The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
|
|
|
+.ie n .IP """EV_IDLE""" 4
|
|
|
+.el .IP "\f(CWEV_IDLE\fR" 4
|
|
|
+.IX Item "EV_IDLE"
|
|
|
+The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
|
|
|
+.ie n .IP """EV_PREPARE""" 4
|
|
|
+.el .IP "\f(CWEV_PREPARE\fR" 4
|
|
|
+.IX Item "EV_PREPARE"
|
|
|
+.PD 0
|
|
|
+.ie n .IP """EV_CHECK""" 4
|
|
|
+.el .IP "\f(CWEV_CHECK\fR" 4
|
|
|
+.IX Item "EV_CHECK"
|
|
|
+.PD
|
|
|
+All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_run\*(C'\fR starts to
|
|
|
+gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are queued (not invoked)
|
|
|
+just after \f(CW\*(C`ev_run\*(C'\fR has gathered them, but before it queues any callbacks
|
|
|
+for any received events. That means \f(CW\*(C`ev_prepare\*(C'\fR watchers are the last
|
|
|
+watchers invoked before the event loop sleeps or polls for new events, and
|
|
|
+\&\f(CW\*(C`ev_check\*(C'\fR watchers will be invoked before any other watchers of the same
|
|
|
+or lower priority within an event loop iteration.
|
|
|
+.Sp
|
|
|
+Callbacks of both watcher types can start and stop as many watchers as
|
|
|
+they want, and all of them will be taken into account (for example, a
|
|
|
+\&\f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep \f(CW\*(C`ev_run\*(C'\fR from
|
|
|
+blocking).
|
|
|
+.ie n .IP """EV_EMBED""" 4
|
|
|
+.el .IP "\f(CWEV_EMBED\fR" 4
|
|
|
+.IX Item "EV_EMBED"
|
|
|
+The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
|
|
|
+.ie n .IP """EV_FORK""" 4
|
|
|
+.el .IP "\f(CWEV_FORK\fR" 4
|
|
|
+.IX Item "EV_FORK"
|
|
|
+The event loop has been resumed in the child process after fork (see
|
|
|
+\&\f(CW\*(C`ev_fork\*(C'\fR).
|
|
|
+.ie n .IP """EV_CLEANUP""" 4
|
|
|
+.el .IP "\f(CWEV_CLEANUP\fR" 4
|
|
|
+.IX Item "EV_CLEANUP"
|
|
|
+The event loop is about to be destroyed (see \f(CW\*(C`ev_cleanup\*(C'\fR).
|
|
|
+.ie n .IP """EV_ASYNC""" 4
|
|
|
+.el .IP "\f(CWEV_ASYNC\fR" 4
|
|
|
+.IX Item "EV_ASYNC"
|
|
|
+The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR).
|
|
|
+.ie n .IP """EV_CUSTOM""" 4
|
|
|
+.el .IP "\f(CWEV_CUSTOM\fR" 4
|
|
|
+.IX Item "EV_CUSTOM"
|
|
|
+Not ever sent (or otherwise used) by libev itself, but can be freely used
|
|
|
+by libev users to signal watchers (e.g. via \f(CW\*(C`ev_feed_event\*(C'\fR).
|
|
|
+.ie n .IP """EV_ERROR""" 4
|
|
|
+.el .IP "\f(CWEV_ERROR\fR" 4
|
|
|
+.IX Item "EV_ERROR"
|
|
|
+An unspecified error has occurred, the watcher has been stopped. This might
|
|
|
+happen because the watcher could not be properly started because libev
|
|
|
+ran out of memory, a file descriptor was found to be closed or any other
|
|
|
+problem. Libev considers these application bugs.
|
|
|
+.Sp
|
|
|
+You best act on it by reporting the problem and somehow coping with the
|
|
|
+watcher being stopped. Note that well-written programs should not receive
|
|
|
+an error ever, so when your watcher receives it, this usually indicates a
|
|
|
+bug in your program.
|
|
|
+.Sp
|
|
|
+Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for
|
|
|
+example it might indicate that a fd is readable or writable, and if your
|
|
|
+callbacks is well-written it can just attempt the operation and cope with
|
|
|
+the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded
|
|
|
+programs, though, as the fd could already be closed and reused for another
|
|
|
+thing, so beware.
|
|
|
+.SS "\s-1GENERIC WATCHER FUNCTIONS\s0"
|
|
|
+.IX Subsection "GENERIC WATCHER FUNCTIONS"
|
|
|
+.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
|
|
|
+.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
|
|
|
+.IX Item "ev_init (ev_TYPE *watcher, callback)"
|
|
|
+This macro initialises the generic portion of a watcher. The contents
|
|
|
+of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
|
|
|
+the generic parts of the watcher are initialised, you \fIneed\fR to call
|
|
|
+the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
|
|
|
+type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
|
|
|
+which rolls both calls into one.
|
|
|
+.Sp
|
|
|
+You can reinitialise a watcher at any time as long as it has been stopped
|
|
|
+(or never started) and there are no pending events outstanding.
|
|
|
+.Sp
|
|
|
+The callback is always of type \f(CW\*(C`void (*)(struct ev_loop *loop, ev_TYPE *watcher,
|
|
|
+int revents)\*(C'\fR.
|
|
|
+.Sp
|
|
|
+Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps.
|
|
|
+.Sp
|
|
|
+.Vb 3
|
|
|
+\& ev_io w;
|
|
|
+\& ev_init (&w, my_cb);
|
|
|
+\& ev_io_set (&w, STDIN_FILENO, EV_READ);
|
|
|
+.Ve
|
|
|
+.ie n .IP """ev_TYPE_set"" (ev_TYPE *watcher, [args])" 4
|
|
|
+.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *watcher, [args])" 4
|
|
|
+.IX Item "ev_TYPE_set (ev_TYPE *watcher, [args])"
|
|
|
+This macro initialises the type-specific parts of a watcher. You need to
|
|
|
+call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
|
|
|
+call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
|
|
|
+macro on a watcher that is active (it can be pending, however, which is a
|
|
|
+difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
|
|
|
+.Sp
|
|
|
+Although some watcher types do not have type-specific arguments
|
|
|
+(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
|
|
|
+.Sp
|
|
|
+See \f(CW\*(C`ev_init\*(C'\fR, above, for an example.
|
|
|
+.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
|
|
|
+.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
|
|
|
+.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
|
|
|
+This convenience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
|
|
|
+calls into a single call. This is the most convenient method to initialise
|
|
|
+a watcher. The same limitations apply, of course.
|
|
|
+.Sp
|
|
|
+Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step.
|
|
|
+.Sp
|
|
|
+.Vb 1
|
|
|
+\& ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
|
|
|
+.Ve
|
|
|
+.ie n .IP """ev_TYPE_start"" (loop, ev_TYPE *watcher)" 4
|
|
|
+.el .IP "\f(CWev_TYPE_start\fR (loop, ev_TYPE *watcher)" 4
|
|
|
+.IX Item "ev_TYPE_start (loop, ev_TYPE *watcher)"
|
|
|
+Starts (activates) the given watcher. Only active watchers will receive
|
|
|
+events. If the watcher is already active nothing will happen.
|
|
|
+.Sp
|
|
|
+Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this
|
|
|
+whole section.
|
|
|
+.Sp
|
|
|
+.Vb 1
|
|
|
+\& ev_io_start (EV_DEFAULT_UC, &w);
|
|
|
+.Ve
|
|
|
+.ie n .IP """ev_TYPE_stop"" (loop, ev_TYPE *watcher)" 4
|
|
|
+.el .IP "\f(CWev_TYPE_stop\fR (loop, ev_TYPE *watcher)" 4
|
|
|
+.IX Item "ev_TYPE_stop (loop, ev_TYPE *watcher)"
|
|
|
+Stops the given watcher if active, and clears the pending status (whether
|
|
|
+the watcher was active or not).
|
|
|
+.Sp
|
|
|
+It is possible that stopped watchers are pending \- for example,
|
|
|
+non-repeating timers are being stopped when they become pending \- but
|
|
|
+calling \f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor
|
|
|
+pending. If you want to free or reuse the memory used by the watcher it is
|
|
|
+therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
|
|
|
+.IP "bool ev_is_active (ev_TYPE *watcher)" 4
|
|
|
+.IX Item "bool ev_is_active (ev_TYPE *watcher)"
|
|
|
+Returns a true value iff the watcher is active (i.e. it has been started
|
|
|
+and not yet been stopped). As long as a watcher is active you must not modify
|
|
|
+it.
|
|
|
+.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
|
|
|
+.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
|
|
|
+Returns a true value iff the watcher is pending, (i.e. it has outstanding
|
|
|
+events but its callback has not yet been invoked). As long as a watcher
|
|
|
+is pending (but not active) you must not call an init function on it (but
|
|
|
+\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
|
|
|
+make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
|
|
|
+it).
|
|
|
+.IP "callback ev_cb (ev_TYPE *watcher)" 4
|
|
|
+.IX Item "callback ev_cb (ev_TYPE *watcher)"
|
|
|
+Returns the callback currently set on the watcher.
|
|
|
+.IP "ev_set_cb (ev_TYPE *watcher, callback)" 4
|
|
|
+.IX Item "ev_set_cb (ev_TYPE *watcher, callback)"
|
|
|
+Change the callback. You can change the callback at virtually any time
|
|
|
+(modulo threads).
|
|
|
+.IP "ev_set_priority (ev_TYPE *watcher, int priority)" 4
|
|
|
+.IX Item "ev_set_priority (ev_TYPE *watcher, int priority)"
|
|
|
+.PD 0
|
|
|
+.IP "int ev_priority (ev_TYPE *watcher)" 4
|
|
|
+.IX Item "int ev_priority (ev_TYPE *watcher)"
|
|
|
+.PD
|
|
|
+Set and query the priority of the watcher. The priority is a small
|
|
|
+integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
|
|
|
+(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
|
|
|
+before watchers with lower priority, but priority will not keep watchers
|
|
|
+from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
|
|
|
+.Sp
|
|
|
+If you need to suppress invocation when higher priority events are pending
|
|
|
+you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
|
|
|
+.Sp
|
|
|
+You \fImust not\fR change the priority of a watcher as long as it is active or
|
|
|
+pending.
|
|
|
+.Sp
|
|
|
+Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
|
|
|
+fine, as long as you do not mind that the priority value you query might
|
|
|
+or might not have been clamped to the valid range.
|
|
|
+.Sp
|
|
|
+The default priority used by watchers when no priority has been set is
|
|
|
+always \f(CW0\fR, which is supposed to not be too high and not be too low :).
|
|
|
+.Sp
|
|
|
+See \*(L"\s-1WATCHER PRIORITY MODELS\*(R"\s0, below, for a more thorough treatment of
|
|
|
+priorities.
|
|
|
+.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
|
|
|
+.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
|
|
|
+Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
|
|
|
+\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
|
|
|
+can deal with that fact, as both are simply passed through to the
|
|
|
+callback.
|
|
|
+.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
|
|
|
+.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
|
|
|
+If the watcher is pending, this function clears its pending status and
|
|
|
+returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
|
|
|
+watcher isn't pending it does nothing and returns \f(CW0\fR.
|
|
|
+.Sp
|
|
|
+Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its
|
|
|
+callback to be invoked, which can be accomplished with this function.
|
|
|
+.IP "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 4
|
|
|
+.IX Item "ev_feed_event (loop, ev_TYPE *watcher, int revents)"
|
|
|
+Feeds the given event set into the event loop, as if the specified event
|
|
|
+had happened for the specified watcher (which must be a pointer to an
|
|
|
+initialised but not necessarily started event watcher). Obviously you must
|
|
|
+not free the watcher as long as it has pending events.
|
|
|
+.Sp
|
|
|
+Stopping the watcher, letting libev invoke it, or calling
|
|
|
+\&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was
|
|
|
+not started in the first place.
|
|
|
+.Sp
|
|
|
+See also \f(CW\*(C`ev_feed_fd_event\*(C'\fR and \f(CW\*(C`ev_feed_signal_event\*(C'\fR for related
|
|
|
+functions that do not need a watcher.
|
|
|
+.PP
|
|
|
+See also the \*(L"\s-1ASSOCIATING CUSTOM DATA WITH A WATCHER\*(R"\s0 and \*(L"\s-1BUILDING YOUR
|
|
|
+OWN COMPOSITE WATCHERS\*(R"\s0 idioms.
|
|
|
+.SS "\s-1WATCHER STATES\s0"
|
|
|
+.IX Subsection "WATCHER STATES"
|
|
|
+There are various watcher states mentioned throughout this manual \-
|
|
|
+active, pending and so on. In this section these states and the rules to
|
|
|
+transition between them will be described in more detail \- and while these
|
|
|
+rules might look complicated, they usually do \*(L"the right thing\*(R".
|
|
|
+.IP "initialised" 4
|
|
|
+.IX Item "initialised"
|
|
|
+Before a watcher can be registered with the event loop it has to be
|
|
|
+initialised. This can be done with a call to \f(CW\*(C`ev_TYPE_init\*(C'\fR, or calls to
|
|
|
+\&\f(CW\*(C`ev_init\*(C'\fR followed by the watcher-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR function.
|
|
|
+.Sp
|
|
|
+In this state it is simply some block of memory that is suitable for
|
|
|
+use in an event loop. It can be moved around, freed, reused etc. at
|
|
|
+will \- as long as you either keep the memory contents intact, or call
|
|
|
+\&\f(CW\*(C`ev_TYPE_init\*(C'\fR again.
|
|
|
+.IP "started/running/active" 4
|
|
|
+.IX Item "started/running/active"
|
|
|
+Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes
|
|
|
+property of the event loop, and is actively waiting for events. While in
|
|
|
+this state it cannot be accessed (except in a few documented ways), moved,
|
|
|
+freed or anything else \- the only legal thing is to keep a pointer to it,
|
|
|
+and call libev functions on it that are documented to work on active watchers.
|
|
|
+.IP "pending" 4
|
|
|
+.IX Item "pending"
|
|
|
+If a watcher is active and libev determines that an event it is interested
|
|
|
+in has occurred (such as a timer expiring), it will become pending. It will
|
|
|
+stay in this pending state until either it is stopped or its callback is
|
|
|
+about to be invoked, so it is not normally pending inside the watcher
|
|
|
+callback.
|
|
|
+.Sp
|
|
|
+The watcher might or might not be active while it is pending (for example,
|
|
|
+an expired non-repeating timer can be pending but no longer active). If it
|
|
|
+is stopped, it can be freely accessed (e.g. by calling \f(CW\*(C`ev_TYPE_set\*(C'\fR),
|
|
|
+but it is still property of the event loop at this time, so cannot be
|
|
|
+moved, freed or reused. And if it is active the rules described in the
|
|
|
+previous item still apply.
|
|
|
+.Sp
|
|
|
+It is also possible to feed an event on a watcher that is not active (e.g.
|
|
|
+via \f(CW\*(C`ev_feed_event\*(C'\fR), in which case it becomes pending without being
|
|
|
+active.
|
|
|
+.IP "stopped" 4
|
|
|
+.IX Item "stopped"
|
|
|
+A watcher can be stopped implicitly by libev (in which case it might still
|
|
|
+be pending), or explicitly by calling its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. The
|
|
|
+latter will clear any pending state the watcher might be in, regardless
|
|
|
+of whether it was active or not, so stopping a watcher explicitly before
|
|
|
+freeing it is often a good idea.
|
|
|
+.Sp
|
|
|
+While stopped (and not pending) the watcher is essentially in the
|
|
|
+initialised state, that is, it can be reused, moved, modified in any way
|
|
|
+you wish (but when you trash the memory block, you need to \f(CW\*(C`ev_TYPE_init\*(C'\fR
|
|
|
+it again).
|
|
|
+.SS "\s-1WATCHER PRIORITY MODELS\s0"
|
|
|
+.IX Subsection "WATCHER PRIORITY MODELS"
|
|
|
+Many event loops support \fIwatcher priorities\fR, which are usually small
|
|
|
+integers that influence the ordering of event callback invocation
|
|
|
+between watchers in some way, all else being equal.
|
|
|
+.PP
|
|
|
+In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its
|
|
|
+description for the more technical details such as the actual priority
|
|
|
+range.
|
|
|
+.PP
|
|
|
+There are two common ways how these these priorities are being interpreted
|
|
|
+by event loops:
|
|
|
+.PP
|
|
|
+In the more common lock-out model, higher priorities \*(L"lock out\*(R" invocation
|
|
|
+of lower priority watchers, which means as long as higher priority
|
|
|
+watchers receive events, lower priority watchers are not being invoked.
|
|
|
+.PP
|
|
|
+The less common only-for-ordering model uses priorities solely to order
|
|
|
+callback invocation within a single event loop iteration: Higher priority
|
|
|
+watchers are invoked before lower priority ones, but they all get invoked
|
|
|
+before polling for new events.
|
|
|
+.PP
|
|
|
+Libev uses the second (only-for-ordering) model for all its watchers
|
|
|
+except for idle watchers (which use the lock-out model).
|
|
|
+.PP
|
|
|
+The rationale behind this is that implementing the lock-out model for
|
|
|
+watchers is not well supported by most kernel interfaces, and most event
|
|
|
+libraries will just poll for the same events again and again as long as
|
|
|
+their callbacks have not been executed, which is very inefficient in the
|
|
|
+common case of one high-priority watcher locking out a mass of lower
|
|
|
+priority ones.
|
|
|
+.PP
|
|
|
+Static (ordering) priorities are most useful when you have two or more
|
|
|
+watchers handling the same resource: a typical usage example is having an
|
|
|
+\&\f(CW\*(C`ev_io\*(C'\fR watcher to receive data, and an associated \f(CW\*(C`ev_timer\*(C'\fR to handle
|
|
|
+timeouts. Under load, data might be received while the program handles
|
|
|
+other jobs, but since timers normally get invoked first, the timeout
|
|
|
+handler will be executed before checking for data. In that case, giving
|
|
|
+the timer a lower priority than the I/O watcher ensures that I/O will be
|
|
|
+handled first even under adverse conditions (which is usually, but not
|
|
|
+always, what you want).
|
|
|
+.PP
|
|
|
+Since idle watchers use the \*(L"lock-out\*(R" model, meaning that idle watchers
|
|
|
+will only be executed when no same or higher priority watchers have
|
|
|
+received events, they can be used to implement the \*(L"lock-out\*(R" model when
|
|
|
+required.
|
|
|
+.PP
|
|
|
+For example, to emulate how many other event libraries handle priorities,
|
|
|
+you can associate an \f(CW\*(C`ev_idle\*(C'\fR watcher to each such watcher, and in
|
|
|
+the normal watcher callback, you just start the idle watcher. The real
|
|
|
+processing is done in the idle watcher callback. This causes libev to
|
|
|
+continuously poll and process kernel event data for the watcher, but when
|
|
|
+the lock-out case is known to be rare (which in turn is rare :), this is
|
|
|
+workable.
|
|
|
+.PP
|
|
|
+Usually, however, the lock-out model implemented that way will perform
|
|
|
+miserably under the type of load it was designed to handle. In that case,
|
|
|
+it might be preferable to stop the real watcher before starting the
|
|
|
+idle watcher, so the kernel will not have to process the event in case
|
|
|
+the actual processing will be delayed for considerable time.
|
|
|
+.PP
|
|
|
+Here is an example of an I/O watcher that should run at a strictly lower
|
|
|
+priority than the default, and which should only process data when no
|
|
|
+other events are pending:
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& ev_idle idle; // actual processing watcher
|
|
|
+\& ev_io io; // actual event watcher
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& io_cb (EV_P_ ev_io *w, int revents)
|
|
|
+\& {
|
|
|
+\& // stop the I/O watcher, we received the event, but
|
|
|
+\& // are not yet ready to handle it.
|
|
|
+\& ev_io_stop (EV_A_ w);
|
|
|
+\&
|
|
|
+\& // start the idle watcher to handle the actual event.
|
|
|
+\& // it will not be executed as long as other watchers
|
|
|
+\& // with the default priority are receiving events.
|
|
|
+\& ev_idle_start (EV_A_ &idle);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& idle_cb (EV_P_ ev_idle *w, int revents)
|
|
|
+\& {
|
|
|
+\& // actual processing
|
|
|
+\& read (STDIN_FILENO, ...);
|
|
|
+\&
|
|
|
+\& // have to start the I/O watcher again, as
|
|
|
+\& // we have handled the event
|
|
|
+\& ev_io_start (EV_P_ &io);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& // initialisation
|
|
|
+\& ev_idle_init (&idle, idle_cb);
|
|
|
+\& ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
|
|
|
+\& ev_io_start (EV_DEFAULT_ &io);
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+In the \*(L"real\*(R" world, it might also be beneficial to start a timer, so that
|
|
|
+low-priority connections can not be locked out forever under load. This
|
|
|
+enables your program to keep a lower latency for important connections
|
|
|
+during short periods of high load, while not completely locking out less
|
|
|
+important ones.
|
|
|
+.SH "WATCHER TYPES"
|
|
|
+.IX Header "WATCHER TYPES"
|
|
|
+This section describes each watcher in detail, but will not repeat
|
|
|
+information given in the last section. Any initialisation/set macros,
|
|
|
+functions and members specific to the watcher type are explained.
|
|
|
+.PP
|
|
|
+Members are additionally marked with either \fI[read\-only]\fR, meaning that,
|
|
|
+while the watcher is active, you can look at the member and expect some
|
|
|
+sensible content, but you must not modify it (you can modify it while the
|
|
|
+watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
|
|
|
+means you can expect it to have some sensible content while the watcher
|
|
|
+is active, but you can also modify it. Modifying it may not do something
|
|
|
+sensible or take immediate effect (or do anything at all), but libev will
|
|
|
+not crash or malfunction in any way.
|
|
|
+.ie n .SS """ev_io"" \- is this file descriptor readable or writable?"
|
|
|
+.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?"
|
|
|
+.IX Subsection "ev_io - is this file descriptor readable or writable?"
|
|
|
+I/O watchers check whether a file descriptor is readable or writable
|
|
|
+in each iteration of the event loop, or, more precisely, when reading
|
|
|
+would not block the process and writing would at least be able to write
|
|
|
+some data. This behaviour is called level-triggering because you keep
|
|
|
+receiving events as long as the condition persists. Remember you can stop
|
|
|
+the watcher if you don't want to act on the event and neither want to
|
|
|
+receive future events.
|
|
|
+.PP
|
|
|
+In general you can register as many read and/or write event watchers per
|
|
|
+fd as you want (as long as you don't confuse yourself). Setting all file
|
|
|
+descriptors to non-blocking mode is also usually a good idea (but not
|
|
|
+required if you know what you are doing).
|
|
|
+.PP
|
|
|
+Another thing you have to watch out for is that it is quite easy to
|
|
|
+receive \*(L"spurious\*(R" readiness notifications, that is, your callback might
|
|
|
+be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
|
|
|
+because there is no data. It is very easy to get into this situation even
|
|
|
+with a relatively standard program structure. Thus it is best to always
|
|
|
+use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning \f(CW\*(C`EAGAIN\*(C'\fR is far
|
|
|
+preferable to a program hanging until some data arrives.
|
|
|
+.PP
|
|
|
+If you cannot run the fd in non-blocking mode (for example you should
|
|
|
+not play around with an Xlib connection), then you have to separately
|
|
|
+re-test whether a file descriptor is really ready with a known-to-be good
|
|
|
+interface such as poll (fortunately in the case of Xlib, it already does
|
|
|
+this on its own, so its quite safe to use). Some people additionally
|
|
|
+use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block
|
|
|
+indefinitely.
|
|
|
+.PP
|
|
|
+But really, best use non-blocking mode.
|
|
|
+.PP
|
|
|
+\fIThe special problem of disappearing file descriptors\fR
|
|
|
+.IX Subsection "The special problem of disappearing file descriptors"
|
|
|
+.PP
|
|
|
+Some backends (e.g. kqueue, epoll) need to be told about closing a file
|
|
|
+descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means,
|
|
|
+such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file
|
|
|
+descriptor, but when it goes away, the operating system will silently drop
|
|
|
+this interest. If another file descriptor with the same number then is
|
|
|
+registered with libev, there is no efficient way to see that this is, in
|
|
|
+fact, a different file descriptor.
|
|
|
+.PP
|
|
|
+To avoid having to explicitly tell libev about such cases, libev follows
|
|
|
+the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
|
|
|
+will assume that this is potentially a new file descriptor, otherwise
|
|
|
+it is assumed that the file descriptor stays the same. That means that
|
|
|
+you \fIhave\fR to call \f(CW\*(C`ev_io_set\*(C'\fR (or \f(CW\*(C`ev_io_init\*(C'\fR) when you change the
|
|
|
+descriptor even if the file descriptor number itself did not change.
|
|
|
+.PP
|
|
|
+This is how one would do it normally anyway, the important point is that
|
|
|
+the libev application should not optimise around libev but should leave
|
|
|
+optimisations to libev.
|
|
|
+.PP
|
|
|
+\fIThe special problem of dup'ed file descriptors\fR
|
|
|
+.IX Subsection "The special problem of dup'ed file descriptors"
|
|
|
+.PP
|
|
|
+Some backends (e.g. epoll), cannot register events for file descriptors,
|
|
|
+but only events for the underlying file descriptions. That means when you
|
|
|
+have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or weirder constellations, and register
|
|
|
+events for them, only one file descriptor might actually receive events.
|
|
|
+.PP
|
|
|
+There is no workaround possible except not registering events
|
|
|
+for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to
|
|
|
+\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
|
|
|
+.PP
|
|
|
+\fIThe special problem of files\fR
|
|
|
+.IX Subsection "The special problem of files"
|
|
|
+.PP
|
|
|
+Many people try to use \f(CW\*(C`select\*(C'\fR (or libev) on file descriptors
|
|
|
+representing files, and expect it to become ready when their program
|
|
|
+doesn't block on disk accesses (which can take a long time on their own).
|
|
|
+.PP
|
|
|
+However, this cannot ever work in the \*(L"expected\*(R" way \- you get a readiness
|
|
|
+notification as soon as the kernel knows whether and how much data is
|
|
|
+there, and in the case of open files, that's always the case, so you
|
|
|
+always get a readiness notification instantly, and your read (or possibly
|
|
|
+write) will still block on the disk I/O.
|
|
|
+.PP
|
|
|
+Another way to view it is that in the case of sockets, pipes, character
|
|
|
+devices and so on, there is another party (the sender) that delivers data
|
|
|
+on its own, but in the case of files, there is no such thing: the disk
|
|
|
+will not send data on its own, simply because it doesn't know what you
|
|
|
+wish to read \- you would first have to request some data.
|
|
|
+.PP
|
|
|
+Since files are typically not-so-well supported by advanced notification
|
|
|
+mechanism, libev tries hard to emulate \s-1POSIX\s0 behaviour with respect
|
|
|
+to files, even though you should not use it. The reason for this is
|
|
|
+convenience: sometimes you want to watch \s-1STDIN\s0 or \s-1STDOUT,\s0 which is
|
|
|
+usually a tty, often a pipe, but also sometimes files or special devices
|
|
|
+(for example, \f(CW\*(C`epoll\*(C'\fR on Linux works with \fI/dev/random\fR but not with
|
|
|
+\&\fI/dev/urandom\fR), and even though the file might better be served with
|
|
|
+asynchronous I/O instead of with non-blocking I/O, it is still useful when
|
|
|
+it \*(L"just works\*(R" instead of freezing.
|
|
|
+.PP
|
|
|
+So avoid file descriptors pointing to files when you know it (e.g. use
|
|
|
+libeio), but use them when it is convenient, e.g. for \s-1STDIN/STDOUT,\s0 or
|
|
|
+when you rarely read from a file instead of from a socket, and want to
|
|
|
+reuse the same code path.
|
|
|
+.PP
|
|
|
+\fIThe special problem of fork\fR
|
|
|
+.IX Subsection "The special problem of fork"
|
|
|
+.PP
|
|
|
+Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit
|
|
|
+useless behaviour. Libev fully supports fork, but needs to be told about
|
|
|
+it in the child if you want to continue to use it in the child.
|
|
|
+.PP
|
|
|
+To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork
|
|
|
+()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to
|
|
|
+\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
|
|
|
+.PP
|
|
|
+\fIThe special problem of \s-1SIGPIPE\s0\fR
|
|
|
+.IX Subsection "The special problem of SIGPIPE"
|
|
|
+.PP
|
|
|
+While not really specific to libev, it is easy to forget about \f(CW\*(C`SIGPIPE\*(C'\fR:
|
|
|
+when writing to a pipe whose other end has been closed, your program gets
|
|
|
+sent a \s-1SIGPIPE,\s0 which, by default, aborts your program. For most programs
|
|
|
+this is sensible behaviour, for daemons, this is usually undesirable.
|
|
|
+.PP
|
|
|
+So when you encounter spurious, unexplained daemon exits, make sure you
|
|
|
+ignore \s-1SIGPIPE \s0(and maybe make sure you log the exit status of your daemon
|
|
|
+somewhere, as that would have given you a big clue).
|
|
|
+.PP
|
|
|
+\fIThe special problem of \fIaccept()\fIing when you can't\fR
|
|
|
+.IX Subsection "The special problem of accept()ing when you can't"
|
|
|
+.PP
|
|
|
+Many implementations of the \s-1POSIX \s0\f(CW\*(C`accept\*(C'\fR function (for example,
|
|
|
+found in post\-2004 Linux) have the peculiar behaviour of not removing a
|
|
|
+connection from the pending queue in all error cases.
|
|
|
+.PP
|
|
|
+For example, larger servers often run out of file descriptors (because
|
|
|
+of resource limits), causing \f(CW\*(C`accept\*(C'\fR to fail with \f(CW\*(C`ENFILE\*(C'\fR but not
|
|
|
+rejecting the connection, leading to libev signalling readiness on
|
|
|
+the next iteration again (the connection still exists after all), and
|
|
|
+typically causing the program to loop at 100% \s-1CPU\s0 usage.
|
|
|
+.PP
|
|
|
+Unfortunately, the set of errors that cause this issue differs between
|
|
|
+operating systems, there is usually little the app can do to remedy the
|
|
|
+situation, and no known thread-safe method of removing the connection to
|
|
|
+cope with overload is known (to me).
|
|
|
+.PP
|
|
|
+One of the easiest ways to handle this situation is to just ignore it
|
|
|
+\&\- when the program encounters an overload, it will just loop until the
|
|
|
+situation is over. While this is a form of busy waiting, no \s-1OS\s0 offers an
|
|
|
+event-based way to handle this situation, so it's the best one can do.
|
|
|
+.PP
|
|
|
+A better way to handle the situation is to log any errors other than
|
|
|
+\&\f(CW\*(C`EAGAIN\*(C'\fR and \f(CW\*(C`EWOULDBLOCK\*(C'\fR, making sure not to flood the log with such
|
|
|
+messages, and continue as usual, which at least gives the user an idea of
|
|
|
+what could be wrong (\*(L"raise the ulimit!\*(R"). For extra points one could stop
|
|
|
+the \f(CW\*(C`ev_io\*(C'\fR watcher on the listening fd \*(L"for a while\*(R", which reduces \s-1CPU\s0
|
|
|
+usage.
|
|
|
+.PP
|
|
|
+If your program is single-threaded, then you could also keep a dummy file
|
|
|
+descriptor for overload situations (e.g. by opening \fI/dev/null\fR), and
|
|
|
+when you run into \f(CW\*(C`ENFILE\*(C'\fR or \f(CW\*(C`EMFILE\*(C'\fR, close it, run \f(CW\*(C`accept\*(C'\fR,
|
|
|
+close that fd, and create a new dummy fd. This will gracefully refuse
|
|
|
+clients under typical overload conditions.
|
|
|
+.PP
|
|
|
+The last way to handle it is to simply log the error and \f(CW\*(C`exit\*(C'\fR, as
|
|
|
+is often done with \f(CW\*(C`malloc\*(C'\fR failures, but this results in an easy
|
|
|
+opportunity for a DoS attack.
|
|
|
+.PP
|
|
|
+\fIWatcher-Specific Functions\fR
|
|
|
+.IX Subsection "Watcher-Specific Functions"
|
|
|
+.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
|
|
|
+.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
|
|
|
+.PD 0
|
|
|
+.IP "ev_io_set (ev_io *, int fd, int events)" 4
|
|
|
+.IX Item "ev_io_set (ev_io *, int fd, int events)"
|
|
|
+.PD
|
|
|
+Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
|
|
|
+receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
|
|
|
+\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events.
|
|
|
+.IP "int fd [read\-only]" 4
|
|
|
+.IX Item "int fd [read-only]"
|
|
|
+The file descriptor being watched.
|
|
|
+.IP "int events [read\-only]" 4
|
|
|
+.IX Item "int events [read-only]"
|
|
|
+The events being watched.
|
|
|
+.PP
|
|
|
+\fIExamples\fR
|
|
|
+.IX Subsection "Examples"
|
|
|
+.PP
|
|
|
+Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
|
|
|
+readable, but only once. Since it is likely line-buffered, you could
|
|
|
+attempt to read a whole line in the callback.
|
|
|
+.PP
|
|
|
+.Vb 6
|
|
|
+\& static void
|
|
|
+\& stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
|
|
|
+\& {
|
|
|
+\& ev_io_stop (loop, w);
|
|
|
+\& .. read from stdin here (or from w\->fd) and handle any I/O errors
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ...
|
|
|
+\& struct ev_loop *loop = ev_default_init (0);
|
|
|
+\& ev_io stdin_readable;
|
|
|
+\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
|
|
|
+\& ev_io_start (loop, &stdin_readable);
|
|
|
+\& ev_run (loop, 0);
|
|
|
+.Ve
|
|
|
+.ie n .SS """ev_timer"" \- relative and optionally repeating timeouts"
|
|
|
+.el .SS "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
|
|
|
+.IX Subsection "ev_timer - relative and optionally repeating timeouts"
|
|
|
+Timer watchers are simple relative timers that generate an event after a
|
|
|
+given time, and optionally repeating in regular intervals after that.
|
|
|
+.PP
|
|
|
+The timers are based on real time, that is, if you register an event that
|
|
|
+times out after an hour and you reset your system clock to January last
|
|
|
+year, it will still time out after (roughly) one hour. \*(L"Roughly\*(R" because
|
|
|
+detecting time jumps is hard, and some inaccuracies are unavoidable (the
|
|
|
+monotonic clock option helps a lot here).
|
|
|
+.PP
|
|
|
+The callback is guaranteed to be invoked only \fIafter\fR its timeout has
|
|
|
+passed (not \fIat\fR, so on systems with very low-resolution clocks this
|
|
|
+might introduce a small delay, see \*(L"the special problem of being too
|
|
|
+early\*(R", below). If multiple timers become ready during the same loop
|
|
|
+iteration then the ones with earlier time-out values are invoked before
|
|
|
+ones of the same priority with later time-out values (but this is no
|
|
|
+longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively).
|
|
|
+.PP
|
|
|
+\fIBe smart about timeouts\fR
|
|
|
+.IX Subsection "Be smart about timeouts"
|
|
|
+.PP
|
|
|
+Many real-world problems involve some kind of timeout, usually for error
|
|
|
+recovery. A typical example is an \s-1HTTP\s0 request \- if the other side hangs,
|
|
|
+you want to raise some error after a while.
|
|
|
+.PP
|
|
|
+What follows are some ways to handle this problem, from obvious and
|
|
|
+inefficient to smart and efficient.
|
|
|
+.PP
|
|
|
+In the following, a 60 second activity timeout is assumed \- a timeout that
|
|
|
+gets reset to 60 seconds each time there is activity (e.g. each time some
|
|
|
+data or other life sign was received).
|
|
|
+.IP "1. Use a timer and stop, reinitialise and start it on activity." 4
|
|
|
+.IX Item "1. Use a timer and stop, reinitialise and start it on activity."
|
|
|
+This is the most obvious, but not the most simple way: In the beginning,
|
|
|
+start the watcher:
|
|
|
+.Sp
|
|
|
+.Vb 2
|
|
|
+\& ev_timer_init (timer, callback, 60., 0.);
|
|
|
+\& ev_timer_start (loop, timer);
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+Then, each time there is some activity, \f(CW\*(C`ev_timer_stop\*(C'\fR it, initialise it
|
|
|
+and start it again:
|
|
|
+.Sp
|
|
|
+.Vb 3
|
|
|
+\& ev_timer_stop (loop, timer);
|
|
|
+\& ev_timer_set (timer, 60., 0.);
|
|
|
+\& ev_timer_start (loop, timer);
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+This is relatively simple to implement, but means that each time there is
|
|
|
+some activity, libev will first have to remove the timer from its internal
|
|
|
+data structure and then add it again. Libev tries to be fast, but it's
|
|
|
+still not a constant-time operation.
|
|
|
+.ie n .IP "2. Use a timer and re-start it with ""ev_timer_again"" inactivity." 4
|
|
|
+.el .IP "2. Use a timer and re-start it with \f(CWev_timer_again\fR inactivity." 4
|
|
|
+.IX Item "2. Use a timer and re-start it with ev_timer_again inactivity."
|
|
|
+This is the easiest way, and involves using \f(CW\*(C`ev_timer_again\*(C'\fR instead of
|
|
|
+\&\f(CW\*(C`ev_timer_start\*(C'\fR.
|
|
|
+.Sp
|
|
|
+To implement this, configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value
|
|
|
+of \f(CW60\fR and then call \f(CW\*(C`ev_timer_again\*(C'\fR at start and each time you
|
|
|
+successfully read or write some data. If you go into an idle state where
|
|
|
+you do not expect data to travel on the socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR
|
|
|
+the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will automatically restart it if need be.
|
|
|
+.Sp
|
|
|
+That means you can ignore both the \f(CW\*(C`ev_timer_start\*(C'\fR function and the
|
|
|
+\&\f(CW\*(C`after\*(C'\fR argument to \f(CW\*(C`ev_timer_set\*(C'\fR, and only ever use the \f(CW\*(C`repeat\*(C'\fR
|
|
|
+member and \f(CW\*(C`ev_timer_again\*(C'\fR.
|
|
|
+.Sp
|
|
|
+At start:
|
|
|
+.Sp
|
|
|
+.Vb 3
|
|
|
+\& ev_init (timer, callback);
|
|
|
+\& timer\->repeat = 60.;
|
|
|
+\& ev_timer_again (loop, timer);
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+Each time there is some activity:
|
|
|
+.Sp
|
|
|
+.Vb 1
|
|
|
+\& ev_timer_again (loop, timer);
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+It is even possible to change the time-out on the fly, regardless of
|
|
|
+whether the watcher is active or not:
|
|
|
+.Sp
|
|
|
+.Vb 2
|
|
|
+\& timer\->repeat = 30.;
|
|
|
+\& ev_timer_again (loop, timer);
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+This is slightly more efficient then stopping/starting the timer each time
|
|
|
+you want to modify its timeout value, as libev does not have to completely
|
|
|
+remove and re-insert the timer from/into its internal data structure.
|
|
|
+.Sp
|
|
|
+It is, however, even simpler than the \*(L"obvious\*(R" way to do it.
|
|
|
+.IP "3. Let the timer time out, but then re-arm it as required." 4
|
|
|
+.IX Item "3. Let the timer time out, but then re-arm it as required."
|
|
|
+This method is more tricky, but usually most efficient: Most timeouts are
|
|
|
+relatively long compared to the intervals between other activity \- in
|
|
|
+our example, within 60 seconds, there are usually many I/O events with
|
|
|
+associated activity resets.
|
|
|
+.Sp
|
|
|
+In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone,
|
|
|
+but remember the time of last activity, and check for a real timeout only
|
|
|
+within the callback:
|
|
|
+.Sp
|
|
|
+.Vb 3
|
|
|
+\& ev_tstamp timeout = 60.;
|
|
|
+\& ev_tstamp last_activity; // time of last activity
|
|
|
+\& ev_timer timer;
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& callback (EV_P_ ev_timer *w, int revents)
|
|
|
+\& {
|
|
|
+\& // calculate when the timeout would happen
|
|
|
+\& ev_tstamp after = last_activity \- ev_now (EV_A) + timeout;
|
|
|
+\&
|
|
|
+\& // if negative, it means we the timeout already occurred
|
|
|
+\& if (after < 0.)
|
|
|
+\& {
|
|
|
+\& // timeout occurred, take action
|
|
|
+\& }
|
|
|
+\& else
|
|
|
+\& {
|
|
|
+\& // callback was invoked, but there was some recent
|
|
|
+\& // activity. simply restart the timer to time out
|
|
|
+\& // after "after" seconds, which is the earliest time
|
|
|
+\& // the timeout can occur.
|
|
|
+\& ev_timer_set (w, after, 0.);
|
|
|
+\& ev_timer_start (EV_A_ w);
|
|
|
+\& }
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+To summarise the callback: first calculate in how many seconds the
|
|
|
+timeout will occur (by calculating the absolute time when it would occur,
|
|
|
+\&\f(CW\*(C`last_activity + timeout\*(C'\fR, and subtracting the current time, \f(CW\*(C`ev_now
|
|
|
+(EV_A)\*(C'\fR from that).
|
|
|
+.Sp
|
|
|
+If this value is negative, then we are already past the timeout, i.e. we
|
|
|
+timed out, and need to do whatever is needed in this case.
|
|
|
+.Sp
|
|
|
+Otherwise, we now the earliest time at which the timeout would trigger,
|
|
|
+and simply start the timer with this timeout value.
|
|
|
+.Sp
|
|
|
+In other words, each time the callback is invoked it will check whether
|
|
|
+the timeout occurred. If not, it will simply reschedule itself to check
|
|
|
+again at the earliest time it could time out. Rinse. Repeat.
|
|
|
+.Sp
|
|
|
+This scheme causes more callback invocations (about one every 60 seconds
|
|
|
+minus half the average time between activity), but virtually no calls to
|
|
|
+libev to change the timeout.
|
|
|
+.Sp
|
|
|
+To start the machinery, simply initialise the watcher and set
|
|
|
+\&\f(CW\*(C`last_activity\*(C'\fR to the current time (meaning there was some activity just
|
|
|
+now), then call the callback, which will \*(L"do the right thing\*(R" and start
|
|
|
+the timer:
|
|
|
+.Sp
|
|
|
+.Vb 3
|
|
|
+\& last_activity = ev_now (EV_A);
|
|
|
+\& ev_init (&timer, callback);
|
|
|
+\& callback (EV_A_ &timer, 0);
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+When there is some activity, simply store the current time in
|
|
|
+\&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all:
|
|
|
+.Sp
|
|
|
+.Vb 2
|
|
|
+\& if (activity detected)
|
|
|
+\& last_activity = ev_now (EV_A);
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+When your timeout value changes, then the timeout can be changed by simply
|
|
|
+providing a new value, stopping the timer and calling the callback, which
|
|
|
+will again do the right thing (for example, time out immediately :).
|
|
|
+.Sp
|
|
|
+.Vb 3
|
|
|
+\& timeout = new_value;
|
|
|
+\& ev_timer_stop (EV_A_ &timer);
|
|
|
+\& callback (EV_A_ &timer, 0);
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+This technique is slightly more complex, but in most cases where the
|
|
|
+time-out is unlikely to be triggered, much more efficient.
|
|
|
+.IP "4. Wee, just use a double-linked list for your timeouts." 4
|
|
|
+.IX Item "4. Wee, just use a double-linked list for your timeouts."
|
|
|
+If there is not one request, but many thousands (millions...), all
|
|
|
+employing some kind of timeout with the same timeout value, then one can
|
|
|
+do even better:
|
|
|
+.Sp
|
|
|
+When starting the timeout, calculate the timeout value and put the timeout
|
|
|
+at the \fIend\fR of the list.
|
|
|
+.Sp
|
|
|
+Then use an \f(CW\*(C`ev_timer\*(C'\fR to fire when the timeout at the \fIbeginning\fR of
|
|
|
+the list is expected to fire (for example, using the technique #3).
|
|
|
+.Sp
|
|
|
+When there is some activity, remove the timer from the list, recalculate
|
|
|
+the timeout, append it to the end of the list again, and make sure to
|
|
|
+update the \f(CW\*(C`ev_timer\*(C'\fR if it was taken from the beginning of the list.
|
|
|
+.Sp
|
|
|
+This way, one can manage an unlimited number of timeouts in O(1) time for
|
|
|
+starting, stopping and updating the timers, at the expense of a major
|
|
|
+complication, and having to use a constant timeout. The constant timeout
|
|
|
+ensures that the list stays sorted.
|
|
|
+.PP
|
|
|
+So which method the best?
|
|
|
+.PP
|
|
|
+Method #2 is a simple no-brain-required solution that is adequate in most
|
|
|
+situations. Method #3 requires a bit more thinking, but handles many cases
|
|
|
+better, and isn't very complicated either. In most case, choosing either
|
|
|
+one is fine, with #3 being better in typical situations.
|
|
|
+.PP
|
|
|
+Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
|
|
|
+rather complicated, but extremely efficient, something that really pays
|
|
|
+off after the first million or so of active timers, i.e. it's usually
|
|
|
+overkill :)
|
|
|
+.PP
|
|
|
+\fIThe special problem of being too early\fR
|
|
|
+.IX Subsection "The special problem of being too early"
|
|
|
+.PP
|
|
|
+If you ask a timer to call your callback after three seconds, then
|
|
|
+you expect it to be invoked after three seconds \- but of course, this
|
|
|
+cannot be guaranteed to infinite precision. Less obviously, it cannot be
|
|
|
+guaranteed to any precision by libev \- imagine somebody suspending the
|
|
|
+process with a \s-1STOP\s0 signal for a few hours for example.
|
|
|
+.PP
|
|
|
+So, libev tries to invoke your callback as soon as possible \fIafter\fR the
|
|
|
+delay has occurred, but cannot guarantee this.
|
|
|
+.PP
|
|
|
+A less obvious failure mode is calling your callback too early: many event
|
|
|
+loops compare timestamps with a \*(L"elapsed delay >= requested delay\*(R", but
|
|
|
+this can cause your callback to be invoked much earlier than you would
|
|
|
+expect.
|
|
|
+.PP
|
|
|
+To see why, imagine a system with a clock that only offers full second
|
|
|
+resolution (think windows if you can't come up with a broken enough \s-1OS\s0
|
|
|
+yourself). If you schedule a one-second timer at the time 500.9, then the
|
|
|
+event loop will schedule your timeout to elapse at a system time of 500
|
|
|
+(500.9 truncated to the resolution) + 1, or 501.
|
|
|
+.PP
|
|
|
+If an event library looks at the timeout 0.1s later, it will see \*(L"501 >=
|
|
|
+501\*(R" and invoke the callback 0.1s after it was started, even though a
|
|
|
+one-second delay was requested \- this is being \*(L"too early\*(R", despite best
|
|
|
+intentions.
|
|
|
+.PP
|
|
|
+This is the reason why libev will never invoke the callback if the elapsed
|
|
|
+delay equals the requested delay, but only when the elapsed delay is
|
|
|
+larger than the requested delay. In the example above, libev would only invoke
|
|
|
+the callback at system time 502, or 1.1s after the timer was started.
|
|
|
+.PP
|
|
|
+So, while libev cannot guarantee that your callback will be invoked
|
|
|
+exactly when requested, it \fIcan\fR and \fIdoes\fR guarantee that the requested
|
|
|
+delay has actually elapsed, or in other words, it always errs on the \*(L"too
|
|
|
+late\*(R" side of things.
|
|
|
+.PP
|
|
|
+\fIThe special problem of time updates\fR
|
|
|
+.IX Subsection "The special problem of time updates"
|
|
|
+.PP
|
|
|
+Establishing the current time is a costly operation (it usually takes
|
|
|
+at least one system call): \s-1EV\s0 therefore updates its idea of the current
|
|
|
+time only before and after \f(CW\*(C`ev_run\*(C'\fR collects new events, which causes a
|
|
|
+growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling
|
|
|
+lots of events in one iteration.
|
|
|
+.PP
|
|
|
+The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR
|
|
|
+time. This is usually the right thing as this timestamp refers to the time
|
|
|
+of the event triggering whatever timeout you are modifying/starting. If
|
|
|
+you suspect event processing to be delayed and you \fIneed\fR to base the
|
|
|
+timeout on the current time, use something like the following to adjust
|
|
|
+for it:
|
|
|
+.PP
|
|
|
+.Vb 1
|
|
|
+\& ev_timer_set (&timer, after + (ev_time () \- ev_now ()), 0.);
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+If the event loop is suspended for a long time, you can also force an
|
|
|
+update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update
|
|
|
+()\*(C'\fR, although that will push the event time of all outstanding events
|
|
|
+further into the future.
|
|
|
+.PP
|
|
|
+\fIThe special problem of unsynchronised clocks\fR
|
|
|
+.IX Subsection "The special problem of unsynchronised clocks"
|
|
|
+.PP
|
|
|
+Modern systems have a variety of clocks \- libev itself uses the normal
|
|
|
+\&\*(L"wall clock\*(R" clock and, if available, the monotonic clock (to avoid time
|
|
|
+jumps).
|
|
|
+.PP
|
|
|
+Neither of these clocks is synchronised with each other or any other clock
|
|
|
+on the system, so \f(CW\*(C`ev_time ()\*(C'\fR might return a considerably different time
|
|
|
+than \f(CW\*(C`gettimeofday ()\*(C'\fR or \f(CW\*(C`time ()\*(C'\fR. On a GNU/Linux system, for example,
|
|
|
+a call to \f(CW\*(C`gettimeofday\*(C'\fR might return a second count that is one higher
|
|
|
+than a directly following call to \f(CW\*(C`time\*(C'\fR.
|
|
|
+.PP
|
|
|
+The moral of this is to only compare libev-related timestamps with
|
|
|
+\&\f(CW\*(C`ev_time ()\*(C'\fR and \f(CW\*(C`ev_now ()\*(C'\fR, at least if you want better precision than
|
|
|
+a second or so.
|
|
|
+.PP
|
|
|
+One more problem arises due to this lack of synchronisation: if libev uses
|
|
|
+the system monotonic clock and you compare timestamps from \f(CW\*(C`ev_time\*(C'\fR
|
|
|
+or \f(CW\*(C`ev_now\*(C'\fR from when you started your timer and when your callback is
|
|
|
+invoked, you will find that sometimes the callback is a bit \*(L"early\*(R".
|
|
|
+.PP
|
|
|
+This is because \f(CW\*(C`ev_timer\*(C'\fRs work in real time, not wall clock time, so
|
|
|
+libev makes sure your callback is not invoked before the delay happened,
|
|
|
+\&\fImeasured according to the real time\fR, not the system clock.
|
|
|
+.PP
|
|
|
+If your timeouts are based on a physical timescale (e.g. \*(L"time out this
|
|
|
+connection after 100 seconds\*(R") then this shouldn't bother you as it is
|
|
|
+exactly the right behaviour.
|
|
|
+.PP
|
|
|
+If you want to compare wall clock/system timestamps to your timers, then
|
|
|
+you need to use \f(CW\*(C`ev_periodic\*(C'\fRs, as these are based on the wall clock
|
|
|
+time, where your comparisons will always generate correct results.
|
|
|
+.PP
|
|
|
+\fIThe special problems of suspended animation\fR
|
|
|
+.IX Subsection "The special problems of suspended animation"
|
|
|
+.PP
|
|
|
+When you leave the server world it is quite customary to hit machines that
|
|
|
+can suspend/hibernate \- what happens to the clocks during such a suspend?
|
|
|
+.PP
|
|
|
+Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
|
|
|
+all processes, while the clocks (\f(CW\*(C`times\*(C'\fR, \f(CW\*(C`CLOCK_MONOTONIC\*(C'\fR) continue
|
|
|
+to run until the system is suspended, but they will not advance while the
|
|
|
+system is suspended. That means, on resume, it will be as if the program
|
|
|
+was frozen for a few seconds, but the suspend time will not be counted
|
|
|
+towards \f(CW\*(C`ev_timer\*(C'\fR when a monotonic clock source is used. The real time
|
|
|
+clock advanced as expected, but if it is used as sole clocksource, then a
|
|
|
+long suspend would be detected as a time jump by libev, and timers would
|
|
|
+be adjusted accordingly.
|
|
|
+.PP
|
|
|
+I would not be surprised to see different behaviour in different between
|
|
|
+operating systems, \s-1OS\s0 versions or even different hardware.
|
|
|
+.PP
|
|
|
+The other form of suspend (job control, or sending a \s-1SIGSTOP\s0) will see a
|
|
|
+time jump in the monotonic clocks and the realtime clock. If the program
|
|
|
+is suspended for a very long time, and monotonic clock sources are in use,
|
|
|
+then you can expect \f(CW\*(C`ev_timer\*(C'\fRs to expire as the full suspension time
|
|
|
+will be counted towards the timers. When no monotonic clock source is in
|
|
|
+use, then libev will again assume a timejump and adjust accordingly.
|
|
|
+.PP
|
|
|
+It might be beneficial for this latter case to call \f(CW\*(C`ev_suspend\*(C'\fR
|
|
|
+and \f(CW\*(C`ev_resume\*(C'\fR in code that handles \f(CW\*(C`SIGTSTP\*(C'\fR, to at least get
|
|
|
+deterministic behaviour in this case (you can do nothing against
|
|
|
+\&\f(CW\*(C`SIGSTOP\*(C'\fR).
|
|
|
+.PP
|
|
|
+\fIWatcher-Specific Functions and Data Members\fR
|
|
|
+.IX Subsection "Watcher-Specific Functions and Data Members"
|
|
|
+.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
|
|
|
+.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
|
|
|
+.PD 0
|
|
|
+.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
|
|
|
+.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
|
|
|
+.PD
|
|
|
+Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR
|
|
|
+is \f(CW0.\fR, then it will automatically be stopped once the timeout is
|
|
|
+reached. If it is positive, then the timer will automatically be
|
|
|
+configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds later, again, and again,
|
|
|
+until stopped manually.
|
|
|
+.Sp
|
|
|
+The timer itself will do a best-effort at avoiding drift, that is, if
|
|
|
+you configure a timer to trigger every 10 seconds, then it will normally
|
|
|
+trigger at exactly 10 second intervals. If, however, your program cannot
|
|
|
+keep up with the timer (because it takes longer than those 10 seconds to
|
|
|
+do stuff) the timer will not fire more than once per event loop iteration.
|
|
|
+.IP "ev_timer_again (loop, ev_timer *)" 4
|
|
|
+.IX Item "ev_timer_again (loop, ev_timer *)"
|
|
|
+This will act as if the timer timed out, and restarts it again if it is
|
|
|
+repeating. It basically works like calling \f(CW\*(C`ev_timer_stop\*(C'\fR, updating the
|
|
|
+timeout to the \f(CW\*(C`repeat\*(C'\fR value and calling \f(CW\*(C`ev_timer_start\*(C'\fR.
|
|
|
+.Sp
|
|
|
+The exact semantics are as in the following rules, all of which will be
|
|
|
+applied to the watcher:
|
|
|
+.RS 4
|
|
|
+.IP "If the timer is pending, the pending status is always cleared." 4
|
|
|
+.IX Item "If the timer is pending, the pending status is always cleared."
|
|
|
+.PD 0
|
|
|
+.IP "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)." 4
|
|
|
+.IX Item "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)."
|
|
|
+.ie n .IP "If the timer is repeating, make the ""repeat"" value the new timeout and start the timer, if necessary." 4
|
|
|
+.el .IP "If the timer is repeating, make the \f(CWrepeat\fR value the new timeout and start the timer, if necessary." 4
|
|
|
+.IX Item "If the timer is repeating, make the repeat value the new timeout and start the timer, if necessary."
|
|
|
+.RE
|
|
|
+.RS 4
|
|
|
+.PD
|
|
|
+.Sp
|
|
|
+This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a
|
|
|
+usage example.
|
|
|
+.RE
|
|
|
+.IP "ev_tstamp ev_timer_remaining (loop, ev_timer *)" 4
|
|
|
+.IX Item "ev_tstamp ev_timer_remaining (loop, ev_timer *)"
|
|
|
+Returns the remaining time until a timer fires. If the timer is active,
|
|
|
+then this time is relative to the current event loop time, otherwise it's
|
|
|
+the timeout value currently configured.
|
|
|
+.Sp
|
|
|
+That is, after an \f(CW\*(C`ev_timer_set (w, 5, 7)\*(C'\fR, \f(CW\*(C`ev_timer_remaining\*(C'\fR returns
|
|
|
+\&\f(CW5\fR. When the timer is started and one second passes, \f(CW\*(C`ev_timer_remaining\*(C'\fR
|
|
|
+will return \f(CW4\fR. When the timer expires and is restarted, it will return
|
|
|
+roughly \f(CW7\fR (likely slightly less as callback invocation takes some time,
|
|
|
+too), and so on.
|
|
|
+.IP "ev_tstamp repeat [read\-write]" 4
|
|
|
+.IX Item "ev_tstamp repeat [read-write]"
|
|
|
+The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
|
|
|
+or \f(CW\*(C`ev_timer_again\*(C'\fR is called, and determines the next timeout (if any),
|
|
|
+which is also when any modifications are taken into account.
|
|
|
+.PP
|
|
|
+\fIExamples\fR
|
|
|
+.IX Subsection "Examples"
|
|
|
+.PP
|
|
|
+Example: Create a timer that fires after 60 seconds.
|
|
|
+.PP
|
|
|
+.Vb 5
|
|
|
+\& static void
|
|
|
+\& one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
|
|
|
+\& {
|
|
|
+\& .. one minute over, w is actually stopped right here
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ev_timer mytimer;
|
|
|
+\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
|
|
|
+\& ev_timer_start (loop, &mytimer);
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Example: Create a timeout timer that times out after 10 seconds of
|
|
|
+inactivity.
|
|
|
+.PP
|
|
|
+.Vb 5
|
|
|
+\& static void
|
|
|
+\& timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
|
|
|
+\& {
|
|
|
+\& .. ten seconds without any activity
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ev_timer mytimer;
|
|
|
+\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
|
|
|
+\& ev_timer_again (&mytimer); /* start timer */
|
|
|
+\& ev_run (loop, 0);
|
|
|
+\&
|
|
|
+\& // and in some piece of code that gets executed on any "activity":
|
|
|
+\& // reset the timeout to start ticking again at 10 seconds
|
|
|
+\& ev_timer_again (&mytimer);
|
|
|
+.Ve
|
|
|
+.ie n .SS """ev_periodic"" \- to cron or not to cron?"
|
|
|
+.el .SS "\f(CWev_periodic\fP \- to cron or not to cron?"
|
|
|
+.IX Subsection "ev_periodic - to cron or not to cron?"
|
|
|
+Periodic watchers are also timers of a kind, but they are very versatile
|
|
|
+(and unfortunately a bit complex).
|
|
|
+.PP
|
|
|
+Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or
|
|
|
+relative time, the physical time that passes) but on wall clock time
|
|
|
+(absolute time, the thing you can read on your calendar or clock). The
|
|
|
+difference is that wall clock time can run faster or slower than real
|
|
|
+time, and time jumps are not uncommon (e.g. when you adjust your
|
|
|
+wrist-watch).
|
|
|
+.PP
|
|
|
+You can tell a periodic watcher to trigger after some specific point
|
|
|
+in time: for example, if you tell a periodic watcher to trigger \*(L"in 10
|
|
|
+seconds\*(R" (by specifying e.g. \f(CW\*(C`ev_now () + 10.\*(C'\fR, that is, an absolute time
|
|
|
+not a delay) and then reset your system clock to January of the previous
|
|
|
+year, then it will take a year or more to trigger the event (unlike an
|
|
|
+\&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting
|
|
|
+it, as it uses a relative timeout).
|
|
|
+.PP
|
|
|
+\&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex
|
|
|
+timers, such as triggering an event on each \*(L"midnight, local time\*(R", or
|
|
|
+other complicated rules. This cannot be done with \f(CW\*(C`ev_timer\*(C'\fR watchers, as
|
|
|
+those cannot react to time jumps.
|
|
|
+.PP
|
|
|
+As with timers, the callback is guaranteed to be invoked only when the
|
|
|
+point in time where it is supposed to trigger has passed. If multiple
|
|
|
+timers become ready during the same loop iteration then the ones with
|
|
|
+earlier time-out values are invoked before ones with later time-out values
|
|
|
+(but this is no longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively).
|
|
|
+.PP
|
|
|
+\fIWatcher-Specific Functions and Data Members\fR
|
|
|
+.IX Subsection "Watcher-Specific Functions and Data Members"
|
|
|
+.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
|
|
|
+.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
|
|
|
+.PD 0
|
|
|
+.IP "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
|
|
|
+.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
|
|
|
+.PD
|
|
|
+Lots of arguments, let's sort it out... There are basically three modes of
|
|
|
+operation, and we will explain them from simplest to most complex:
|
|
|
+.RS 4
|
|
|
+.IP "\(bu" 4
|
|
|
+absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
|
|
|
+.Sp
|
|
|
+In this configuration the watcher triggers an event after the wall clock
|
|
|
+time \f(CW\*(C`offset\*(C'\fR has passed. It will not repeat and will not adjust when a
|
|
|
+time jump occurs, that is, if it is to be run at January 1st 2011 then it
|
|
|
+will be stopped and invoked when the system clock reaches or surpasses
|
|
|
+this point in time.
|
|
|
+.IP "\(bu" 4
|
|
|
+repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
|
|
|
+.Sp
|
|
|
+In this mode the watcher will always be scheduled to time out at the next
|
|
|
+\&\f(CW\*(C`offset + N * interval\*(C'\fR time (for some integer N, which can also be
|
|
|
+negative) and then repeat, regardless of any time jumps. The \f(CW\*(C`offset\*(C'\fR
|
|
|
+argument is merely an offset into the \f(CW\*(C`interval\*(C'\fR periods.
|
|
|
+.Sp
|
|
|
+This can be used to create timers that do not drift with respect to the
|
|
|
+system clock, for example, here is an \f(CW\*(C`ev_periodic\*(C'\fR that triggers each
|
|
|
+hour, on the hour (with respect to \s-1UTC\s0):
|
|
|
+.Sp
|
|
|
+.Vb 1
|
|
|
+\& ev_periodic_set (&periodic, 0., 3600., 0);
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+This doesn't mean there will always be 3600 seconds in between triggers,
|
|
|
+but only that the callback will be called when the system time shows a
|
|
|
+full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible
|
|
|
+by 3600.
|
|
|
+.Sp
|
|
|
+Another way to think about it (for the mathematically inclined) is that
|
|
|
+\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
|
|
|
+time where \f(CW\*(C`time = offset (mod interval)\*(C'\fR, regardless of any time jumps.
|
|
|
+.Sp
|
|
|
+The \f(CW\*(C`interval\*(C'\fR \fI\s-1MUST\s0\fR be positive, and for numerical stability, the
|
|
|
+interval value should be higher than \f(CW\*(C`1/8192\*(C'\fR (which is around 100
|
|
|
+microseconds) and \f(CW\*(C`offset\*(C'\fR should be higher than \f(CW0\fR and should have
|
|
|
+at most a similar magnitude as the current time (say, within a factor of
|
|
|
+ten). Typical values for offset are, in fact, \f(CW0\fR or something between
|
|
|
+\&\f(CW0\fR and \f(CW\*(C`interval\*(C'\fR, which is also the recommended range.
|
|
|
+.Sp
|
|
|
+Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0
|
|
|
+speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability
|
|
|
+will of course deteriorate. Libev itself tries to be exact to be about one
|
|
|
+millisecond (if the \s-1OS\s0 supports it and the machine is fast enough).
|
|
|
+.IP "\(bu" 4
|
|
|
+manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
|
|
|
+.Sp
|
|
|
+In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being
|
|
|
+ignored. Instead, each time the periodic watcher gets scheduled, the
|
|
|
+reschedule callback will be called with the watcher as first, and the
|
|
|
+current time as second argument.
|
|
|
+.Sp
|
|
|
+\&\s-1NOTE: \s0\fIThis callback \s-1MUST NOT\s0 stop or destroy any periodic watcher, ever,
|
|
|
+or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly
|
|
|
+allowed by documentation here\fR.
|
|
|
+.Sp
|
|
|
+If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop
|
|
|
+it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the
|
|
|
+only event loop modification you are allowed to do).
|
|
|
+.Sp
|
|
|
+The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(ev_periodic
|
|
|
+*w, ev_tstamp now)\*(C'\fR, e.g.:
|
|
|
+.Sp
|
|
|
+.Vb 5
|
|
|
+\& static ev_tstamp
|
|
|
+\& my_rescheduler (ev_periodic *w, ev_tstamp now)
|
|
|
+\& {
|
|
|
+\& return now + 60.;
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+It must return the next time to trigger, based on the passed time value
|
|
|
+(that is, the lowest time value larger than to the second argument). It
|
|
|
+will usually be called just before the callback will be triggered, but
|
|
|
+might be called at other times, too.
|
|
|
+.Sp
|
|
|
+\&\s-1NOTE: \s0\fIThis callback must always return a time that is higher than or
|
|
|
+equal to the passed \f(CI\*(C`now\*(C'\fI value\fR.
|
|
|
+.Sp
|
|
|
+This can be used to create very complex timers, such as a timer that
|
|
|
+triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate the
|
|
|
+next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How
|
|
|
+you do this is, again, up to you (but it is not trivial, which is the main
|
|
|
+reason I omitted it as an example).
|
|
|
+.RE
|
|
|
+.RS 4
|
|
|
+.RE
|
|
|
+.IP "ev_periodic_again (loop, ev_periodic *)" 4
|
|
|
+.IX Item "ev_periodic_again (loop, ev_periodic *)"
|
|
|
+Simply stops and restarts the periodic watcher again. This is only useful
|
|
|
+when you changed some parameters or the reschedule callback would return
|
|
|
+a different time than the last time it was called (e.g. in a crond like
|
|
|
+program when the crontabs have changed).
|
|
|
+.IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4
|
|
|
+.IX Item "ev_tstamp ev_periodic_at (ev_periodic *)"
|
|
|
+When active, returns the absolute time that the watcher is supposed
|
|
|
+to trigger next. This is not the same as the \f(CW\*(C`offset\*(C'\fR argument to
|
|
|
+\&\f(CW\*(C`ev_periodic_set\*(C'\fR, but indeed works even in interval and manual
|
|
|
+rescheduling modes.
|
|
|
+.IP "ev_tstamp offset [read\-write]" 4
|
|
|
+.IX Item "ev_tstamp offset [read-write]"
|
|
|
+When repeating, this contains the offset value, otherwise this is the
|
|
|
+absolute point in time (the \f(CW\*(C`offset\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR,
|
|
|
+although libev might modify this value for better numerical stability).
|
|
|
+.Sp
|
|
|
+Can be modified any time, but changes only take effect when the periodic
|
|
|
+timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
|
|
|
+.IP "ev_tstamp interval [read\-write]" 4
|
|
|
+.IX Item "ev_tstamp interval [read-write]"
|
|
|
+The current interval value. Can be modified any time, but changes only
|
|
|
+take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
|
|
|
+called.
|
|
|
+.IP "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read\-write]" 4
|
|
|
+.IX Item "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]"
|
|
|
+The current reschedule callback, or \f(CW0\fR, if this functionality is
|
|
|
+switched off. Can be changed any time, but changes only take effect when
|
|
|
+the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
|
|
|
+.PP
|
|
|
+\fIExamples\fR
|
|
|
+.IX Subsection "Examples"
|
|
|
+.PP
|
|
|
+Example: Call a callback every hour, or, more precisely, whenever the
|
|
|
+system time is divisible by 3600. The callback invocation times have
|
|
|
+potentially a lot of jitter, but good long-term stability.
|
|
|
+.PP
|
|
|
+.Vb 5
|
|
|
+\& static void
|
|
|
+\& clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
|
|
|
+\& {
|
|
|
+\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ev_periodic hourly_tick;
|
|
|
+\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
|
|
|
+\& ev_periodic_start (loop, &hourly_tick);
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Example: The same as above, but use a reschedule callback to do it:
|
|
|
+.PP
|
|
|
+.Vb 1
|
|
|
+\& #include <math.h>
|
|
|
+\&
|
|
|
+\& static ev_tstamp
|
|
|
+\& my_scheduler_cb (ev_periodic *w, ev_tstamp now)
|
|
|
+\& {
|
|
|
+\& return now + (3600. \- fmod (now, 3600.));
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Example: Call a callback every hour, starting now:
|
|
|
+.PP
|
|
|
+.Vb 4
|
|
|
+\& ev_periodic hourly_tick;
|
|
|
+\& ev_periodic_init (&hourly_tick, clock_cb,
|
|
|
+\& fmod (ev_now (loop), 3600.), 3600., 0);
|
|
|
+\& ev_periodic_start (loop, &hourly_tick);
|
|
|
+.Ve
|
|
|
+.ie n .SS """ev_signal"" \- signal me when a signal gets signalled!"
|
|
|
+.el .SS "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
|
|
|
+.IX Subsection "ev_signal - signal me when a signal gets signalled!"
|
|
|
+Signal watchers will trigger an event when the process receives a specific
|
|
|
+signal one or more times. Even though signals are very asynchronous, libev
|
|
|
+will try its best to deliver signals synchronously, i.e. as part of the
|
|
|
+normal event processing, like any other event.
|
|
|
+.PP
|
|
|
+If you want signals to be delivered truly asynchronously, just use
|
|
|
+\&\f(CW\*(C`sigaction\*(C'\fR as you would do without libev and forget about sharing
|
|
|
+the signal. You can even use \f(CW\*(C`ev_async\*(C'\fR from a signal handler to
|
|
|
+synchronously wake up an event loop.
|
|
|
+.PP
|
|
|
+You can configure as many watchers as you like for the same signal, but
|
|
|
+only within the same loop, i.e. you can watch for \f(CW\*(C`SIGINT\*(C'\fR in your
|
|
|
+default loop and for \f(CW\*(C`SIGIO\*(C'\fR in another loop, but you cannot watch for
|
|
|
+\&\f(CW\*(C`SIGINT\*(C'\fR in both the default loop and another loop at the same time. At
|
|
|
+the moment, \f(CW\*(C`SIGCHLD\*(C'\fR is permanently tied to the default loop.
|
|
|
+.PP
|
|
|
+Only after the first watcher for a signal is started will libev actually
|
|
|
+register something with the kernel. It thus coexists with your own signal
|
|
|
+handlers as long as you don't register any with libev for the same signal.
|
|
|
+.PP
|
|
|
+If possible and supported, libev will install its handlers with
|
|
|
+\&\f(CW\*(C`SA_RESTART\*(C'\fR (or equivalent) behaviour enabled, so system calls should
|
|
|
+not be unduly interrupted. If you have a problem with system calls getting
|
|
|
+interrupted by signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher
|
|
|
+and unblock them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher.
|
|
|
+.PP
|
|
|
+\fIThe special problem of inheritance over fork/execve/pthread_create\fR
|
|
|
+.IX Subsection "The special problem of inheritance over fork/execve/pthread_create"
|
|
|
+.PP
|
|
|
+Both the signal mask (\f(CW\*(C`sigprocmask\*(C'\fR) and the signal disposition
|
|
|
+(\f(CW\*(C`sigaction\*(C'\fR) are unspecified after starting a signal watcher (and after
|
|
|
+stopping it again), that is, libev might or might not block the signal,
|
|
|
+and might or might not set or restore the installed signal handler (but
|
|
|
+see \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR).
|
|
|
+.PP
|
|
|
+While this does not matter for the signal disposition (libev never
|
|
|
+sets signals to \f(CW\*(C`SIG_IGN\*(C'\fR, so handlers will be reset to \f(CW\*(C`SIG_DFL\*(C'\fR on
|
|
|
+\&\f(CW\*(C`execve\*(C'\fR), this matters for the signal mask: many programs do not expect
|
|
|
+certain signals to be blocked.
|
|
|
+.PP
|
|
|
+This means that before calling \f(CW\*(C`exec\*(C'\fR (from the child) you should reset
|
|
|
+the signal mask to whatever \*(L"default\*(R" you expect (all clear is a good
|
|
|
+choice usually).
|
|
|
+.PP
|
|
|
+The simplest way to ensure that the signal mask is reset in the child is
|
|
|
+to install a fork handler with \f(CW\*(C`pthread_atfork\*(C'\fR that resets it. That will
|
|
|
+catch fork calls done by libraries (such as the libc) as well.
|
|
|
+.PP
|
|
|
+In current versions of libev, the signal will not be blocked indefinitely
|
|
|
+unless you use the \f(CW\*(C`signalfd\*(C'\fR \s-1API \s0(\f(CW\*(C`EV_SIGNALFD\*(C'\fR). While this reduces
|
|
|
+the window of opportunity for problems, it will not go away, as libev
|
|
|
+\&\fIhas\fR to modify the signal mask, at least temporarily.
|
|
|
+.PP
|
|
|
+So I can't stress this enough: \fIIf you do not reset your signal mask when
|
|
|
+you expect it to be empty, you have a race condition in your code\fR. This
|
|
|
+is not a libev-specific thing, this is true for most event libraries.
|
|
|
+.PP
|
|
|
+\fIThe special problem of threads signal handling\fR
|
|
|
+.IX Subsection "The special problem of threads signal handling"
|
|
|
+.PP
|
|
|
+\&\s-1POSIX\s0 threads has problematic signal handling semantics, specifically,
|
|
|
+a lot of functionality (sigfd, sigwait etc.) only really works if all
|
|
|
+threads in a process block signals, which is hard to achieve.
|
|
|
+.PP
|
|
|
+When you want to use sigwait (or mix libev signal handling with your own
|
|
|
+for the same signals), you can tackle this problem by globally blocking
|
|
|
+all signals before creating any threads (or creating them with a fully set
|
|
|
+sigprocmask) and also specifying the \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when creating
|
|
|
+loops. Then designate one thread as \*(L"signal receiver thread\*(R" which handles
|
|
|
+these signals. You can pass on any signals that libev might be interested
|
|
|
+in by calling \f(CW\*(C`ev_feed_signal\*(C'\fR.
|
|
|
+.PP
|
|
|
+\fIWatcher-Specific Functions and Data Members\fR
|
|
|
+.IX Subsection "Watcher-Specific Functions and Data Members"
|
|
|
+.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
|
|
|
+.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
|
|
|
+.PD 0
|
|
|
+.IP "ev_signal_set (ev_signal *, int signum)" 4
|
|
|
+.IX Item "ev_signal_set (ev_signal *, int signum)"
|
|
|
+.PD
|
|
|
+Configures the watcher to trigger on the given signal number (usually one
|
|
|
+of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
|
|
|
+.IP "int signum [read\-only]" 4
|
|
|
+.IX Item "int signum [read-only]"
|
|
|
+The signal the watcher watches out for.
|
|
|
+.PP
|
|
|
+\fIExamples\fR
|
|
|
+.IX Subsection "Examples"
|
|
|
+.PP
|
|
|
+Example: Try to exit cleanly on \s-1SIGINT.\s0
|
|
|
+.PP
|
|
|
+.Vb 5
|
|
|
+\& static void
|
|
|
+\& sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
|
|
|
+\& {
|
|
|
+\& ev_break (loop, EVBREAK_ALL);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ev_signal signal_watcher;
|
|
|
+\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
|
|
|
+\& ev_signal_start (loop, &signal_watcher);
|
|
|
+.Ve
|
|
|
+.ie n .SS """ev_child"" \- watch out for process status changes"
|
|
|
+.el .SS "\f(CWev_child\fP \- watch out for process status changes"
|
|
|
+.IX Subsection "ev_child - watch out for process status changes"
|
|
|
+Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
|
|
|
+some child status changes (most typically when a child of yours dies or
|
|
|
+exits). It is permissible to install a child watcher \fIafter\fR the child
|
|
|
+has been forked (which implies it might have already exited), as long
|
|
|
+as the event loop isn't entered (or is continued from a watcher), i.e.,
|
|
|
+forking and then immediately registering a watcher for the child is fine,
|
|
|
+but forking and registering a watcher a few event loop iterations later or
|
|
|
+in the next callback invocation is not.
|
|
|
+.PP
|
|
|
+Only the default event loop is capable of handling signals, and therefore
|
|
|
+you can only register child watchers in the default event loop.
|
|
|
+.PP
|
|
|
+Due to some design glitches inside libev, child watchers will always be
|
|
|
+handled at maximum priority (their priority is set to \f(CW\*(C`EV_MAXPRI\*(C'\fR by
|
|
|
+libev)
|
|
|
+.PP
|
|
|
+\fIProcess Interaction\fR
|
|
|
+.IX Subsection "Process Interaction"
|
|
|
+.PP
|
|
|
+Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is
|
|
|
+initialised. This is necessary to guarantee proper behaviour even if the
|
|
|
+first child watcher is started after the child exits. The occurrence
|
|
|
+of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done
|
|
|
+synchronously as part of the event loop processing. Libev always reaps all
|
|
|
+children, even ones not watched.
|
|
|
+.PP
|
|
|
+\fIOverriding the Built-In Processing\fR
|
|
|
+.IX Subsection "Overriding the Built-In Processing"
|
|
|
+.PP
|
|
|
+Libev offers no special support for overriding the built-in child
|
|
|
+processing, but if your application collides with libev's default child
|
|
|
+handler, you can override it easily by installing your own handler for
|
|
|
+\&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the
|
|
|
+default loop never gets destroyed. You are encouraged, however, to use an
|
|
|
+event-based approach to child reaping and thus use libev's support for
|
|
|
+that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely.
|
|
|
+.PP
|
|
|
+\fIStopping the Child Watcher\fR
|
|
|
+.IX Subsection "Stopping the Child Watcher"
|
|
|
+.PP
|
|
|
+Currently, the child watcher never gets stopped, even when the
|
|
|
+child terminates, so normally one needs to stop the watcher in the
|
|
|
+callback. Future versions of libev might stop the watcher automatically
|
|
|
+when a child exit is detected (calling \f(CW\*(C`ev_child_stop\*(C'\fR twice is not a
|
|
|
+problem).
|
|
|
+.PP
|
|
|
+\fIWatcher-Specific Functions and Data Members\fR
|
|
|
+.IX Subsection "Watcher-Specific Functions and Data Members"
|
|
|
+.IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4
|
|
|
+.IX Item "ev_child_init (ev_child *, callback, int pid, int trace)"
|
|
|
+.PD 0
|
|
|
+.IP "ev_child_set (ev_child *, int pid, int trace)" 4
|
|
|
+.IX Item "ev_child_set (ev_child *, int pid, int trace)"
|
|
|
+.PD
|
|
|
+Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or
|
|
|
+\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
|
|
|
+at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
|
|
|
+the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
|
|
|
+\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
|
|
|
+process causing the status change. \f(CW\*(C`trace\*(C'\fR must be either \f(CW0\fR (only
|
|
|
+activate the watcher when the process terminates) or \f(CW1\fR (additionally
|
|
|
+activate the watcher when the process is stopped or continued).
|
|
|
+.IP "int pid [read\-only]" 4
|
|
|
+.IX Item "int pid [read-only]"
|
|
|
+The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
|
|
|
+.IP "int rpid [read\-write]" 4
|
|
|
+.IX Item "int rpid [read-write]"
|
|
|
+The process id that detected a status change.
|
|
|
+.IP "int rstatus [read\-write]" 4
|
|
|
+.IX Item "int rstatus [read-write]"
|
|
|
+The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
|
|
|
+\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
|
|
|
+.PP
|
|
|
+\fIExamples\fR
|
|
|
+.IX Subsection "Examples"
|
|
|
+.PP
|
|
|
+Example: \f(CW\*(C`fork()\*(C'\fR a new process and install a child handler to wait for
|
|
|
+its completion.
|
|
|
+.PP
|
|
|
+.Vb 1
|
|
|
+\& ev_child cw;
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& child_cb (EV_P_ ev_child *w, int revents)
|
|
|
+\& {
|
|
|
+\& ev_child_stop (EV_A_ w);
|
|
|
+\& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& pid_t pid = fork ();
|
|
|
+\&
|
|
|
+\& if (pid < 0)
|
|
|
+\& // error
|
|
|
+\& else if (pid == 0)
|
|
|
+\& {
|
|
|
+\& // the forked child executes here
|
|
|
+\& exit (1);
|
|
|
+\& }
|
|
|
+\& else
|
|
|
+\& {
|
|
|
+\& ev_child_init (&cw, child_cb, pid, 0);
|
|
|
+\& ev_child_start (EV_DEFAULT_ &cw);
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.ie n .SS """ev_stat"" \- did the file attributes just change?"
|
|
|
+.el .SS "\f(CWev_stat\fP \- did the file attributes just change?"
|
|
|
+.IX Subsection "ev_stat - did the file attributes just change?"
|
|
|
+This watches a file system path for attribute changes. That is, it calls
|
|
|
+\&\f(CW\*(C`stat\*(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed)
|
|
|
+and sees if it changed compared to the last time, invoking the callback
|
|
|
+if it did. Starting the watcher \f(CW\*(C`stat\*(C'\fR's the file, so only changes that
|
|
|
+happen after the watcher has been started will be reported.
|
|
|
+.PP
|
|
|
+The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
|
|
|
+not exist\*(R" is a status change like any other. The condition \*(L"path does not
|
|
|
+exist\*(R" (or more correctly \*(L"path cannot be stat'ed\*(R") is signified by the
|
|
|
+\&\f(CW\*(C`st_nlink\*(C'\fR field being zero (which is otherwise always forced to be at
|
|
|
+least one) and all the other fields of the stat buffer having unspecified
|
|
|
+contents.
|
|
|
+.PP
|
|
|
+The path \fImust not\fR end in a slash or contain special components such as
|
|
|
+\&\f(CW\*(C`.\*(C'\fR or \f(CW\*(C`..\*(C'\fR. The path \fIshould\fR be absolute: If it is relative and
|
|
|
+your working directory changes, then the behaviour is undefined.
|
|
|
+.PP
|
|
|
+Since there is no portable change notification interface available, the
|
|
|
+portable implementation simply calls \f(CWstat(2)\fR regularly on the path
|
|
|
+to see if it changed somehow. You can specify a recommended polling
|
|
|
+interval for this case. If you specify a polling interval of \f(CW0\fR (highly
|
|
|
+recommended!) then a \fIsuitable, unspecified default\fR value will be used
|
|
|
+(which you can expect to be around five seconds, although this might
|
|
|
+change dynamically). Libev will also impose a minimum interval which is
|
|
|
+currently around \f(CW0.1\fR, but that's usually overkill.
|
|
|
+.PP
|
|
|
+This watcher type is not meant for massive numbers of stat watchers,
|
|
|
+as even with OS-supported change notifications, this can be
|
|
|
+resource-intensive.
|
|
|
+.PP
|
|
|
+At the time of this writing, the only OS-specific interface implemented
|
|
|
+is the Linux inotify interface (implementing kqueue support is left as an
|
|
|
+exercise for the reader. Note, however, that the author sees no way of
|
|
|
+implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue, except as a hint).
|
|
|
+.PP
|
|
|
+\fI\s-1ABI\s0 Issues (Largefile Support)\fR
|
|
|
+.IX Subsection "ABI Issues (Largefile Support)"
|
|
|
+.PP
|
|
|
+Libev by default (unless the user overrides this) uses the default
|
|
|
+compilation environment, which means that on systems with large file
|
|
|
+support disabled by default, you get the 32 bit version of the stat
|
|
|
+structure. When using the library from programs that change the \s-1ABI\s0 to
|
|
|
+use 64 bit file offsets the programs will fail. In that case you have to
|
|
|
+compile libev with the same flags to get binary compatibility. This is
|
|
|
+obviously the case with any flags that change the \s-1ABI,\s0 but the problem is
|
|
|
+most noticeably displayed with ev_stat and large file support.
|
|
|
+.PP
|
|
|
+The solution for this is to lobby your distribution maker to make large
|
|
|
+file interfaces available by default (as e.g. FreeBSD does) and not
|
|
|
+optional. Libev cannot simply switch on large file support because it has
|
|
|
+to exchange stat structures with application programs compiled using the
|
|
|
+default compilation environment.
|
|
|
+.PP
|
|
|
+\fIInotify and Kqueue\fR
|
|
|
+.IX Subsection "Inotify and Kqueue"
|
|
|
+.PP
|
|
|
+When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev and present at
|
|
|
+runtime, it will be used to speed up change detection where possible. The
|
|
|
+inotify descriptor will be created lazily when the first \f(CW\*(C`ev_stat\*(C'\fR
|
|
|
+watcher is being started.
|
|
|
+.PP
|
|
|
+Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers
|
|
|
+except that changes might be detected earlier, and in some cases, to avoid
|
|
|
+making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support
|
|
|
+there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling,
|
|
|
+but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
|
|
|
+many bugs), the path exists (i.e. stat succeeds), and the path resides on
|
|
|
+a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
|
|
|
+xfs are fully working) libev usually gets away without polling.
|
|
|
+.PP
|
|
|
+There is no support for kqueue, as apparently it cannot be used to
|
|
|
+implement this functionality, due to the requirement of having a file
|
|
|
+descriptor open on the object at all times, and detecting renames, unlinks
|
|
|
+etc. is difficult.
|
|
|
+.PP
|
|
|
+\fI\f(CI\*(C`stat ()\*(C'\fI is a synchronous operation\fR
|
|
|
+.IX Subsection "stat () is a synchronous operation"
|
|
|
+.PP
|
|
|
+Libev doesn't normally do any kind of I/O itself, and so is not blocking
|
|
|
+the process. The exception are \f(CW\*(C`ev_stat\*(C'\fR watchers \- those call \f(CW\*(C`stat
|
|
|
+()\*(C'\fR, which is a synchronous operation.
|
|
|
+.PP
|
|
|
+For local paths, this usually doesn't matter: unless the system is very
|
|
|
+busy or the intervals between stat's are large, a stat call will be fast,
|
|
|
+as the path data is usually in memory already (except when starting the
|
|
|
+watcher).
|
|
|
+.PP
|
|
|
+For networked file systems, calling \f(CW\*(C`stat ()\*(C'\fR can block an indefinite
|
|
|
+time due to network issues, and even under good conditions, a stat call
|
|
|
+often takes multiple milliseconds.
|
|
|
+.PP
|
|
|
+Therefore, it is best to avoid using \f(CW\*(C`ev_stat\*(C'\fR watchers on networked
|
|
|
+paths, although this is fully supported by libev.
|
|
|
+.PP
|
|
|
+\fIThe special problem of stat time resolution\fR
|
|
|
+.IX Subsection "The special problem of stat time resolution"
|
|
|
+.PP
|
|
|
+The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably,
|
|
|
+and even on systems where the resolution is higher, most file systems
|
|
|
+still only support whole seconds.
|
|
|
+.PP
|
|
|
+That means that, if the time is the only thing that changes, you can
|
|
|
+easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and
|
|
|
+calls your callback, which does something. When there is another update
|
|
|
+within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the
|
|
|
+stat data does change in other ways (e.g. file size).
|
|
|
+.PP
|
|
|
+The solution to this is to delay acting on a change for slightly more
|
|
|
+than a second (or till slightly after the next full second boundary), using
|
|
|
+a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02);
|
|
|
+ev_timer_again (loop, w)\*(C'\fR).
|
|
|
+.PP
|
|
|
+The \f(CW.02\fR offset is added to work around small timing inconsistencies
|
|
|
+of some operating systems (where the second counter of the current time
|
|
|
+might be be delayed. One such system is the Linux kernel, where a call to
|
|
|
+\&\f(CW\*(C`gettimeofday\*(C'\fR might return a timestamp with a full second later than
|
|
|
+a subsequent \f(CW\*(C`time\*(C'\fR call \- if the equivalent of \f(CW\*(C`time ()\*(C'\fR is used to
|
|
|
+update file times then there will be a small window where the kernel uses
|
|
|
+the previous second to update file times but libev might already execute
|
|
|
+the timer callback).
|
|
|
+.PP
|
|
|
+\fIWatcher-Specific Functions and Data Members\fR
|
|
|
+.IX Subsection "Watcher-Specific Functions and Data Members"
|
|
|
+.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
|
|
|
+.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
|
|
|
+.PD 0
|
|
|
+.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
|
|
|
+.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
|
|
|
+.PD
|
|
|
+Configures the watcher to wait for status changes of the given
|
|
|
+\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
|
|
|
+be detected and should normally be specified as \f(CW0\fR to let libev choose
|
|
|
+a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
|
|
|
+path for as long as the watcher is active.
|
|
|
+.Sp
|
|
|
+The callback will receive an \f(CW\*(C`EV_STAT\*(C'\fR event when a change was detected,
|
|
|
+relative to the attributes at the time the watcher was started (or the
|
|
|
+last change was detected).
|
|
|
+.IP "ev_stat_stat (loop, ev_stat *)" 4
|
|
|
+.IX Item "ev_stat_stat (loop, ev_stat *)"
|
|
|
+Updates the stat buffer immediately with new values. If you change the
|
|
|
+watched path in your callback, you could call this function to avoid
|
|
|
+detecting this change (while introducing a race condition if you are not
|
|
|
+the only one changing the path). Can also be useful simply to find out the
|
|
|
+new values.
|
|
|
+.IP "ev_statdata attr [read\-only]" 4
|
|
|
+.IX Item "ev_statdata attr [read-only]"
|
|
|
+The most-recently detected attributes of the file. Although the type is
|
|
|
+\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
|
|
|
+suitable for your system, but you can only rely on the POSIX-standardised
|
|
|
+members to be present. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there was
|
|
|
+some error while \f(CW\*(C`stat\*(C'\fRing the file.
|
|
|
+.IP "ev_statdata prev [read\-only]" 4
|
|
|
+.IX Item "ev_statdata prev [read-only]"
|
|
|
+The previous attributes of the file. The callback gets invoked whenever
|
|
|
+\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR, or, more precisely, one or more of these members
|
|
|
+differ: \f(CW\*(C`st_dev\*(C'\fR, \f(CW\*(C`st_ino\*(C'\fR, \f(CW\*(C`st_mode\*(C'\fR, \f(CW\*(C`st_nlink\*(C'\fR, \f(CW\*(C`st_uid\*(C'\fR,
|
|
|
+\&\f(CW\*(C`st_gid\*(C'\fR, \f(CW\*(C`st_rdev\*(C'\fR, \f(CW\*(C`st_size\*(C'\fR, \f(CW\*(C`st_atime\*(C'\fR, \f(CW\*(C`st_mtime\*(C'\fR, \f(CW\*(C`st_ctime\*(C'\fR.
|
|
|
+.IP "ev_tstamp interval [read\-only]" 4
|
|
|
+.IX Item "ev_tstamp interval [read-only]"
|
|
|
+The specified interval.
|
|
|
+.IP "const char *path [read\-only]" 4
|
|
|
+.IX Item "const char *path [read-only]"
|
|
|
+The file system path that is being watched.
|
|
|
+.PP
|
|
|
+\fIExamples\fR
|
|
|
+.IX Subsection "Examples"
|
|
|
+.PP
|
|
|
+Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
|
|
|
+.PP
|
|
|
+.Vb 10
|
|
|
+\& static void
|
|
|
+\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
|
|
|
+\& {
|
|
|
+\& /* /etc/passwd changed in some way */
|
|
|
+\& if (w\->attr.st_nlink)
|
|
|
+\& {
|
|
|
+\& printf ("passwd current size %ld\en", (long)w\->attr.st_size);
|
|
|
+\& printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime);
|
|
|
+\& printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime);
|
|
|
+\& }
|
|
|
+\& else
|
|
|
+\& /* you shalt not abuse printf for puts */
|
|
|
+\& puts ("wow, /etc/passwd is not there, expect problems. "
|
|
|
+\& "if this is windows, they already arrived\en");
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ...
|
|
|
+\& ev_stat passwd;
|
|
|
+\&
|
|
|
+\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
|
|
|
+\& ev_stat_start (loop, &passwd);
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Example: Like above, but additionally use a one-second delay so we do not
|
|
|
+miss updates (however, frequent updates will delay processing, too, so
|
|
|
+one might do the work both on \f(CW\*(C`ev_stat\*(C'\fR callback invocation \fIand\fR on
|
|
|
+\&\f(CW\*(C`ev_timer\*(C'\fR callback invocation).
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& static ev_stat passwd;
|
|
|
+\& static ev_timer timer;
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& timer_cb (EV_P_ ev_timer *w, int revents)
|
|
|
+\& {
|
|
|
+\& ev_timer_stop (EV_A_ w);
|
|
|
+\&
|
|
|
+\& /* now it\*(Aqs one second after the most recent passwd change */
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& stat_cb (EV_P_ ev_stat *w, int revents)
|
|
|
+\& {
|
|
|
+\& /* reset the one\-second timer */
|
|
|
+\& ev_timer_again (EV_A_ &timer);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ...
|
|
|
+\& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
|
|
|
+\& ev_stat_start (loop, &passwd);
|
|
|
+\& ev_timer_init (&timer, timer_cb, 0., 1.02);
|
|
|
+.Ve
|
|
|
+.ie n .SS """ev_idle"" \- when you've got nothing better to do..."
|
|
|
+.el .SS "\f(CWev_idle\fP \- when you've got nothing better to do..."
|
|
|
+.IX Subsection "ev_idle - when you've got nothing better to do..."
|
|
|
+Idle watchers trigger events when no other events of the same or higher
|
|
|
+priority are pending (prepare, check and other idle watchers do not count
|
|
|
+as receiving \*(L"events\*(R").
|
|
|
+.PP
|
|
|
+That is, as long as your process is busy handling sockets or timeouts
|
|
|
+(or even signals, imagine) of the same or higher priority it will not be
|
|
|
+triggered. But when your process is idle (or only lower-priority watchers
|
|
|
+are pending), the idle watchers are being called once per event loop
|
|
|
+iteration \- until stopped, that is, or your process receives more events
|
|
|
+and becomes busy again with higher priority stuff.
|
|
|
+.PP
|
|
|
+The most noteworthy effect is that as long as any idle watchers are
|
|
|
+active, the process will not block when waiting for new events.
|
|
|
+.PP
|
|
|
+Apart from keeping your process non-blocking (which is a useful
|
|
|
+effect on its own sometimes), idle watchers are a good place to do
|
|
|
+\&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the
|
|
|
+event loop has handled all outstanding events.
|
|
|
+.PP
|
|
|
+\fIAbusing an \f(CI\*(C`ev_idle\*(C'\fI watcher for its side-effect\fR
|
|
|
+.IX Subsection "Abusing an ev_idle watcher for its side-effect"
|
|
|
+.PP
|
|
|
+As long as there is at least one active idle watcher, libev will never
|
|
|
+sleep unnecessarily. Or in other words, it will loop as fast as possible.
|
|
|
+For this to work, the idle watcher doesn't need to be invoked at all \- the
|
|
|
+lowest priority will do.
|
|
|
+.PP
|
|
|
+This mode of operation can be useful together with an \f(CW\*(C`ev_check\*(C'\fR watcher,
|
|
|
+to do something on each event loop iteration \- for example to balance load
|
|
|
+between different connections.
|
|
|
+.PP
|
|
|
+See \*(L"Abusing an ev_check watcher for its side-effect\*(R" for a longer
|
|
|
+example.
|
|
|
+.PP
|
|
|
+\fIWatcher-Specific Functions and Data Members\fR
|
|
|
+.IX Subsection "Watcher-Specific Functions and Data Members"
|
|
|
+.IP "ev_idle_init (ev_idle *, callback)" 4
|
|
|
+.IX Item "ev_idle_init (ev_idle *, callback)"
|
|
|
+Initialises and configures the idle watcher \- it has no parameters of any
|
|
|
+kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
|
|
|
+believe me.
|
|
|
+.PP
|
|
|
+\fIExamples\fR
|
|
|
+.IX Subsection "Examples"
|
|
|
+.PP
|
|
|
+Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
|
|
|
+callback, free it. Also, use no error checking, as usual.
|
|
|
+.PP
|
|
|
+.Vb 5
|
|
|
+\& static void
|
|
|
+\& idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
|
|
|
+\& {
|
|
|
+\& // stop the watcher
|
|
|
+\& ev_idle_stop (loop, w);
|
|
|
+\&
|
|
|
+\& // now we can free it
|
|
|
+\& free (w);
|
|
|
+\&
|
|
|
+\& // now do something you wanted to do when the program has
|
|
|
+\& // no longer anything immediate to do.
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ev_idle *idle_watcher = malloc (sizeof (ev_idle));
|
|
|
+\& ev_idle_init (idle_watcher, idle_cb);
|
|
|
+\& ev_idle_start (loop, idle_watcher);
|
|
|
+.Ve
|
|
|
+.ie n .SS """ev_prepare"" and ""ev_check"" \- customise your event loop!"
|
|
|
+.el .SS "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
|
|
|
+.IX Subsection "ev_prepare and ev_check - customise your event loop!"
|
|
|
+Prepare and check watchers are often (but not always) used in pairs:
|
|
|
+prepare watchers get invoked before the process blocks and check watchers
|
|
|
+afterwards.
|
|
|
+.PP
|
|
|
+You \fImust not\fR call \f(CW\*(C`ev_run\*(C'\fR (or similar functions that enter the
|
|
|
+current event loop) or \f(CW\*(C`ev_loop_fork\*(C'\fR from either \f(CW\*(C`ev_prepare\*(C'\fR or
|
|
|
+\&\f(CW\*(C`ev_check\*(C'\fR watchers. Other loops than the current one are fine,
|
|
|
+however. The rationale behind this is that you do not need to check
|
|
|
+for recursion in those watchers, i.e. the sequence will always be
|
|
|
+\&\f(CW\*(C`ev_prepare\*(C'\fR, blocking, \f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each
|
|
|
+kind they will always be called in pairs bracketing the blocking call.
|
|
|
+.PP
|
|
|
+Their main purpose is to integrate other event mechanisms into libev and
|
|
|
+their use is somewhat advanced. They could be used, for example, to track
|
|
|
+variable changes, implement your own watchers, integrate net-snmp or a
|
|
|
+coroutine library and lots more. They are also occasionally useful if
|
|
|
+you cache some data and want to flush it before blocking (for example,
|
|
|
+in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
|
|
|
+watcher).
|
|
|
+.PP
|
|
|
+This is done by examining in each prepare call which file descriptors
|
|
|
+need to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers
|
|
|
+for them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many
|
|
|
+libraries provide exactly this functionality). Then, in the check watcher,
|
|
|
+you check for any events that occurred (by checking the pending status
|
|
|
+of all watchers and stopping them) and call back into the library. The
|
|
|
+I/O and timer callbacks will never actually be called (but must be valid
|
|
|
+nevertheless, because you never know, you know?).
|
|
|
+.PP
|
|
|
+As another example, the Perl Coro module uses these hooks to integrate
|
|
|
+coroutines into libev programs, by yielding to other active coroutines
|
|
|
+during each prepare and only letting the process block if no coroutines
|
|
|
+are ready to run (it's actually more complicated: it only runs coroutines
|
|
|
+with priority higher than or equal to the event loop and one coroutine
|
|
|
+of lower priority, but only once, using idle watchers to keep the event
|
|
|
+loop from blocking if lower-priority coroutines are active, thus mapping
|
|
|
+low-priority coroutines to idle/background tasks).
|
|
|
+.PP
|
|
|
+When used for this purpose, it is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers
|
|
|
+highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) priority, to ensure that they are being run before
|
|
|
+any other watchers after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR
|
|
|
+watchers).
|
|
|
+.PP
|
|
|
+Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not
|
|
|
+activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they
|
|
|
+might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As
|
|
|
+\&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event
|
|
|
+loops those other event loops might be in an unusable state until their
|
|
|
+\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
|
|
|
+others).
|
|
|
+.PP
|
|
|
+\fIAbusing an \f(CI\*(C`ev_check\*(C'\fI watcher for its side-effect\fR
|
|
|
+.IX Subsection "Abusing an ev_check watcher for its side-effect"
|
|
|
+.PP
|
|
|
+\&\f(CW\*(C`ev_check\*(C'\fR (and less often also \f(CW\*(C`ev_prepare\*(C'\fR) watchers can also be
|
|
|
+useful because they are called once per event loop iteration. For
|
|
|
+example, if you want to handle a large number of connections fairly, you
|
|
|
+normally only do a bit of work for each active connection, and if there
|
|
|
+is more work to do, you wait for the next event loop iteration, so other
|
|
|
+connections have a chance of making progress.
|
|
|
+.PP
|
|
|
+Using an \f(CW\*(C`ev_check\*(C'\fR watcher is almost enough: it will be called on the
|
|
|
+next event loop iteration. However, that isn't as soon as possible \-
|
|
|
+without external events, your \f(CW\*(C`ev_check\*(C'\fR watcher will not be invoked.
|
|
|
+.PP
|
|
|
+This is where \f(CW\*(C`ev_idle\*(C'\fR watchers come in handy \- all you need is a
|
|
|
+single global idle watcher that is active as long as you have one active
|
|
|
+\&\f(CW\*(C`ev_check\*(C'\fR watcher. The \f(CW\*(C`ev_idle\*(C'\fR watcher makes sure the event loop
|
|
|
+will not sleep, and the \f(CW\*(C`ev_check\*(C'\fR watcher makes sure a callback gets
|
|
|
+invoked. Neither watcher alone can do that.
|
|
|
+.PP
|
|
|
+\fIWatcher-Specific Functions and Data Members\fR
|
|
|
+.IX Subsection "Watcher-Specific Functions and Data Members"
|
|
|
+.IP "ev_prepare_init (ev_prepare *, callback)" 4
|
|
|
+.IX Item "ev_prepare_init (ev_prepare *, callback)"
|
|
|
+.PD 0
|
|
|
+.IP "ev_check_init (ev_check *, callback)" 4
|
|
|
+.IX Item "ev_check_init (ev_check *, callback)"
|
|
|
+.PD
|
|
|
+Initialises and configures the prepare or check watcher \- they have no
|
|
|
+parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
|
|
|
+macros, but using them is utterly, utterly, utterly and completely
|
|
|
+pointless.
|
|
|
+.PP
|
|
|
+\fIExamples\fR
|
|
|
+.IX Subsection "Examples"
|
|
|
+.PP
|
|
|
+There are a number of principal ways to embed other event loops or modules
|
|
|
+into libev. Here are some ideas on how to include libadns into libev
|
|
|
+(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
|
|
|
+use as a working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR embeds a
|
|
|
+Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 into the
|
|
|
+Glib event loop).
|
|
|
+.PP
|
|
|
+Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
|
|
|
+and in a check watcher, destroy them and call into libadns. What follows
|
|
|
+is pseudo-code only of course. This requires you to either use a low
|
|
|
+priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
|
|
|
+the callbacks for the IO/timeout watchers might not have been called yet.
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& static ev_io iow [nfd];
|
|
|
+\& static ev_timer tw;
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& io_cb (struct ev_loop *loop, ev_io *w, int revents)
|
|
|
+\& {
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& // create io watchers for each fd and a timer before blocking
|
|
|
+\& static void
|
|
|
+\& adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
|
|
|
+\& {
|
|
|
+\& int timeout = 3600000;
|
|
|
+\& struct pollfd fds [nfd];
|
|
|
+\& // actual code will need to loop here and realloc etc.
|
|
|
+\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
|
|
|
+\&
|
|
|
+\& /* the callback is illegal, but won\*(Aqt be called as we stop during check */
|
|
|
+\& ev_timer_init (&tw, 0, timeout * 1e\-3, 0.);
|
|
|
+\& ev_timer_start (loop, &tw);
|
|
|
+\&
|
|
|
+\& // create one ev_io per pollfd
|
|
|
+\& for (int i = 0; i < nfd; ++i)
|
|
|
+\& {
|
|
|
+\& ev_io_init (iow + i, io_cb, fds [i].fd,
|
|
|
+\& ((fds [i].events & POLLIN ? EV_READ : 0)
|
|
|
+\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
|
|
|
+\&
|
|
|
+\& fds [i].revents = 0;
|
|
|
+\& ev_io_start (loop, iow + i);
|
|
|
+\& }
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& // stop all watchers after blocking
|
|
|
+\& static void
|
|
|
+\& adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
|
|
|
+\& {
|
|
|
+\& ev_timer_stop (loop, &tw);
|
|
|
+\&
|
|
|
+\& for (int i = 0; i < nfd; ++i)
|
|
|
+\& {
|
|
|
+\& // set the relevant poll flags
|
|
|
+\& // could also call adns_processreadable etc. here
|
|
|
+\& struct pollfd *fd = fds + i;
|
|
|
+\& int revents = ev_clear_pending (iow + i);
|
|
|
+\& if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN;
|
|
|
+\& if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT;
|
|
|
+\&
|
|
|
+\& // now stop the watcher
|
|
|
+\& ev_io_stop (loop, iow + i);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
|
|
|
+in the prepare watcher and would dispose of the check watcher.
|
|
|
+.PP
|
|
|
+Method 3: If the module to be embedded supports explicit event
|
|
|
+notification (libadns does), you can also make use of the actual watcher
|
|
|
+callbacks, and only destroy/create the watchers in the prepare watcher.
|
|
|
+.PP
|
|
|
+.Vb 5
|
|
|
+\& static void
|
|
|
+\& timer_cb (EV_P_ ev_timer *w, int revents)
|
|
|
+\& {
|
|
|
+\& adns_state ads = (adns_state)w\->data;
|
|
|
+\& update_now (EV_A);
|
|
|
+\&
|
|
|
+\& adns_processtimeouts (ads, &tv_now);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& io_cb (EV_P_ ev_io *w, int revents)
|
|
|
+\& {
|
|
|
+\& adns_state ads = (adns_state)w\->data;
|
|
|
+\& update_now (EV_A);
|
|
|
+\&
|
|
|
+\& if (revents & EV_READ ) adns_processreadable (ads, w\->fd, &tv_now);
|
|
|
+\& if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& // do not ever call adns_afterpoll
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Method 4: Do not use a prepare or check watcher because the module you
|
|
|
+want to embed is not flexible enough to support it. Instead, you can
|
|
|
+override their poll function. The drawback with this solution is that the
|
|
|
+main loop is now no longer controllable by \s-1EV.\s0 The \f(CW\*(C`Glib::EV\*(C'\fR module uses
|
|
|
+this approach, effectively embedding \s-1EV\s0 as a client into the horrible
|
|
|
+libglib event loop.
|
|
|
+.PP
|
|
|
+.Vb 4
|
|
|
+\& static gint
|
|
|
+\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
|
|
|
+\& {
|
|
|
+\& int got_events = 0;
|
|
|
+\&
|
|
|
+\& for (n = 0; n < nfds; ++n)
|
|
|
+\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
|
|
|
+\&
|
|
|
+\& if (timeout >= 0)
|
|
|
+\& // create/start timer
|
|
|
+\&
|
|
|
+\& // poll
|
|
|
+\& ev_run (EV_A_ 0);
|
|
|
+\&
|
|
|
+\& // stop timer again
|
|
|
+\& if (timeout >= 0)
|
|
|
+\& ev_timer_stop (EV_A_ &to);
|
|
|
+\&
|
|
|
+\& // stop io watchers again \- their callbacks should have set
|
|
|
+\& for (n = 0; n < nfds; ++n)
|
|
|
+\& ev_io_stop (EV_A_ iow [n]);
|
|
|
+\&
|
|
|
+\& return got_events;
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.ie n .SS """ev_embed"" \- when one backend isn't enough..."
|
|
|
+.el .SS "\f(CWev_embed\fP \- when one backend isn't enough..."
|
|
|
+.IX Subsection "ev_embed - when one backend isn't enough..."
|
|
|
+This is a rather advanced watcher type that lets you embed one event loop
|
|
|
+into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
|
|
|
+loop, other types of watchers might be handled in a delayed or incorrect
|
|
|
+fashion and must not be used).
|
|
|
+.PP
|
|
|
+There are primarily two reasons you would want that: work around bugs and
|
|
|
+prioritise I/O.
|
|
|
+.PP
|
|
|
+As an example for a bug workaround, the kqueue backend might only support
|
|
|
+sockets on some platform, so it is unusable as generic backend, but you
|
|
|
+still want to make use of it because you have many sockets and it scales
|
|
|
+so nicely. In this case, you would create a kqueue-based loop and embed
|
|
|
+it into your default loop (which might use e.g. poll). Overall operation
|
|
|
+will be a bit slower because first libev has to call \f(CW\*(C`poll\*(C'\fR and then
|
|
|
+\&\f(CW\*(C`kevent\*(C'\fR, but at least you can use both mechanisms for what they are
|
|
|
+best: \f(CW\*(C`kqueue\*(C'\fR for scalable sockets and \f(CW\*(C`poll\*(C'\fR if you want it to work :)
|
|
|
+.PP
|
|
|
+As for prioritising I/O: under rare circumstances you have the case where
|
|
|
+some fds have to be watched and handled very quickly (with low latency),
|
|
|
+and even priorities and idle watchers might have too much overhead. In
|
|
|
+this case you would put all the high priority stuff in one loop and all
|
|
|
+the rest in a second one, and embed the second one in the first.
|
|
|
+.PP
|
|
|
+As long as the watcher is active, the callback will be invoked every
|
|
|
+time there might be events pending in the embedded loop. The callback
|
|
|
+must then call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single
|
|
|
+sweep and invoke their callbacks (the callback doesn't need to invoke the
|
|
|
+\&\f(CW\*(C`ev_embed_sweep\*(C'\fR function directly, it could also start an idle watcher
|
|
|
+to give the embedded loop strictly lower priority for example).
|
|
|
+.PP
|
|
|
+You can also set the callback to \f(CW0\fR, in which case the embed watcher
|
|
|
+will automatically execute the embedded loop sweep whenever necessary.
|
|
|
+.PP
|
|
|
+Fork detection will be handled transparently while the \f(CW\*(C`ev_embed\*(C'\fR watcher
|
|
|
+is active, i.e., the embedded loop will automatically be forked when the
|
|
|
+embedding loop forks. In other cases, the user is responsible for calling
|
|
|
+\&\f(CW\*(C`ev_loop_fork\*(C'\fR on the embedded loop.
|
|
|
+.PP
|
|
|
+Unfortunately, not all backends are embeddable: only the ones returned by
|
|
|
+\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
|
|
|
+portable one.
|
|
|
+.PP
|
|
|
+So when you want to use this feature you will always have to be prepared
|
|
|
+that you cannot get an embeddable loop. The recommended way to get around
|
|
|
+this is to have a separate variables for your embeddable loop, try to
|
|
|
+create it, and if that fails, use the normal loop for everything.
|
|
|
+.PP
|
|
|
+\fI\f(CI\*(C`ev_embed\*(C'\fI and fork\fR
|
|
|
+.IX Subsection "ev_embed and fork"
|
|
|
+.PP
|
|
|
+While the \f(CW\*(C`ev_embed\*(C'\fR watcher is running, forks in the embedding loop will
|
|
|
+automatically be applied to the embedded loop as well, so no special
|
|
|
+fork handling is required in that case. When the watcher is not running,
|
|
|
+however, it is still the task of the libev user to call \f(CW\*(C`ev_loop_fork ()\*(C'\fR
|
|
|
+as applicable.
|
|
|
+.PP
|
|
|
+\fIWatcher-Specific Functions and Data Members\fR
|
|
|
+.IX Subsection "Watcher-Specific Functions and Data Members"
|
|
|
+.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
|
|
|
+.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
|
|
|
+.PD 0
|
|
|
+.IP "ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)" 4
|
|
|
+.IX Item "ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)"
|
|
|
+.PD
|
|
|
+Configures the watcher to embed the given loop, which must be
|
|
|
+embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
|
|
|
+invoked automatically, otherwise it is the responsibility of the callback
|
|
|
+to invoke it (it will continue to be called until the sweep has been done,
|
|
|
+if you do not want that, you need to temporarily stop the embed watcher).
|
|
|
+.IP "ev_embed_sweep (loop, ev_embed *)" 4
|
|
|
+.IX Item "ev_embed_sweep (loop, ev_embed *)"
|
|
|
+Make a single, non-blocking sweep over the embedded loop. This works
|
|
|
+similarly to \f(CW\*(C`ev_run (embedded_loop, EVRUN_NOWAIT)\*(C'\fR, but in the most
|
|
|
+appropriate way for embedded loops.
|
|
|
+.IP "struct ev_loop *other [read\-only]" 4
|
|
|
+.IX Item "struct ev_loop *other [read-only]"
|
|
|
+The embedded event loop.
|
|
|
+.PP
|
|
|
+\fIExamples\fR
|
|
|
+.IX Subsection "Examples"
|
|
|
+.PP
|
|
|
+Example: Try to get an embeddable event loop and embed it into the default
|
|
|
+event loop. If that is not possible, use the default loop. The default
|
|
|
+loop is stored in \f(CW\*(C`loop_hi\*(C'\fR, while the embeddable loop is stored in
|
|
|
+\&\f(CW\*(C`loop_lo\*(C'\fR (which is \f(CW\*(C`loop_hi\*(C'\fR in the case no embeddable loop can be
|
|
|
+used).
|
|
|
+.PP
|
|
|
+.Vb 3
|
|
|
+\& struct ev_loop *loop_hi = ev_default_init (0);
|
|
|
+\& struct ev_loop *loop_lo = 0;
|
|
|
+\& ev_embed embed;
|
|
|
+\&
|
|
|
+\& // see if there is a chance of getting one that works
|
|
|
+\& // (remember that a flags value of 0 means autodetection)
|
|
|
+\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
|
|
|
+\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
|
|
|
+\& : 0;
|
|
|
+\&
|
|
|
+\& // if we got one, then embed it, otherwise default to loop_hi
|
|
|
+\& if (loop_lo)
|
|
|
+\& {
|
|
|
+\& ev_embed_init (&embed, 0, loop_lo);
|
|
|
+\& ev_embed_start (loop_hi, &embed);
|
|
|
+\& }
|
|
|
+\& else
|
|
|
+\& loop_lo = loop_hi;
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Example: Check if kqueue is available but not recommended and create
|
|
|
+a kqueue backend for use with sockets (which usually work with any
|
|
|
+kqueue implementation). Store the kqueue/socket\-only event loop in
|
|
|
+\&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too).
|
|
|
+.PP
|
|
|
+.Vb 3
|
|
|
+\& struct ev_loop *loop = ev_default_init (0);
|
|
|
+\& struct ev_loop *loop_socket = 0;
|
|
|
+\& ev_embed embed;
|
|
|
+\&
|
|
|
+\& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
|
|
|
+\& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
|
|
|
+\& {
|
|
|
+\& ev_embed_init (&embed, 0, loop_socket);
|
|
|
+\& ev_embed_start (loop, &embed);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& if (!loop_socket)
|
|
|
+\& loop_socket = loop;
|
|
|
+\&
|
|
|
+\& // now use loop_socket for all sockets, and loop for everything else
|
|
|
+.Ve
|
|
|
+.ie n .SS """ev_fork"" \- the audacity to resume the event loop after a fork"
|
|
|
+.el .SS "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
|
|
|
+.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
|
|
|
+Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
|
|
|
+whoever is a good citizen cared to tell libev about it by calling
|
|
|
+\&\f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the event loop blocks next
|
|
|
+and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, and only in the child
|
|
|
+after the fork. If whoever good citizen calling \f(CW\*(C`ev_default_fork\*(C'\fR cheats
|
|
|
+and calls it in the wrong process, the fork handlers will be invoked, too,
|
|
|
+of course.
|
|
|
+.PP
|
|
|
+\fIThe special problem of life after fork \- how is it possible?\fR
|
|
|
+.IX Subsection "The special problem of life after fork - how is it possible?"
|
|
|
+.PP
|
|
|
+Most uses of \f(CW\*(C`fork ()\*(C'\fR consist of forking, then some simple calls to set
|
|
|
+up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This
|
|
|
+sequence should be handled by libev without any problems.
|
|
|
+.PP
|
|
|
+This changes when the application actually wants to do event handling
|
|
|
+in the child, or both parent in child, in effect \*(L"continuing\*(R" after the
|
|
|
+fork.
|
|
|
+.PP
|
|
|
+The default mode of operation (for libev, with application help to detect
|
|
|
+forks) is to duplicate all the state in the child, as would be expected
|
|
|
+when \fIeither\fR the parent \fIor\fR the child process continues.
|
|
|
+.PP
|
|
|
+When both processes want to continue using libev, then this is usually the
|
|
|
+wrong result. In that case, usually one process (typically the parent) is
|
|
|
+supposed to continue with all watchers in place as before, while the other
|
|
|
+process typically wants to start fresh, i.e. without any active watchers.
|
|
|
+.PP
|
|
|
+The cleanest and most efficient way to achieve that with libev is to
|
|
|
+simply create a new event loop, which of course will be \*(L"empty\*(R", and
|
|
|
+use that for new watchers. This has the advantage of not touching more
|
|
|
+memory than necessary, and thus avoiding the copy-on-write, and the
|
|
|
+disadvantage of having to use multiple event loops (which do not support
|
|
|
+signal watchers).
|
|
|
+.PP
|
|
|
+When this is not possible, or you want to use the default loop for
|
|
|
+other reasons, then in the process that wants to start \*(L"fresh\*(R", call
|
|
|
+\&\f(CW\*(C`ev_loop_destroy (EV_DEFAULT)\*(C'\fR followed by \f(CW\*(C`ev_default_loop (...)\*(C'\fR.
|
|
|
+Destroying the default loop will \*(L"orphan\*(R" (not stop) all registered
|
|
|
+watchers, so you have to be careful not to execute code that modifies
|
|
|
+those watchers. Note also that in that case, you have to re-register any
|
|
|
+signal watchers.
|
|
|
+.PP
|
|
|
+\fIWatcher-Specific Functions and Data Members\fR
|
|
|
+.IX Subsection "Watcher-Specific Functions and Data Members"
|
|
|
+.IP "ev_fork_init (ev_fork *, callback)" 4
|
|
|
+.IX Item "ev_fork_init (ev_fork *, callback)"
|
|
|
+Initialises and configures the fork watcher \- it has no parameters of any
|
|
|
+kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
|
|
|
+really.
|
|
|
+.ie n .SS """ev_cleanup"" \- even the best things end"
|
|
|
+.el .SS "\f(CWev_cleanup\fP \- even the best things end"
|
|
|
+.IX Subsection "ev_cleanup - even the best things end"
|
|
|
+Cleanup watchers are called just before the event loop is being destroyed
|
|
|
+by a call to \f(CW\*(C`ev_loop_destroy\*(C'\fR.
|
|
|
+.PP
|
|
|
+While there is no guarantee that the event loop gets destroyed, cleanup
|
|
|
+watchers provide a convenient method to install cleanup hooks for your
|
|
|
+program, worker threads and so on \- you just to make sure to destroy the
|
|
|
+loop when you want them to be invoked.
|
|
|
+.PP
|
|
|
+Cleanup watchers are invoked in the same way as any other watcher. Unlike
|
|
|
+all other watchers, they do not keep a reference to the event loop (which
|
|
|
+makes a lot of sense if you think about it). Like all other watchers, you
|
|
|
+can call libev functions in the callback, except \f(CW\*(C`ev_cleanup_start\*(C'\fR.
|
|
|
+.PP
|
|
|
+\fIWatcher-Specific Functions and Data Members\fR
|
|
|
+.IX Subsection "Watcher-Specific Functions and Data Members"
|
|
|
+.IP "ev_cleanup_init (ev_cleanup *, callback)" 4
|
|
|
+.IX Item "ev_cleanup_init (ev_cleanup *, callback)"
|
|
|
+Initialises and configures the cleanup watcher \- it has no parameters of
|
|
|
+any kind. There is a \f(CW\*(C`ev_cleanup_set\*(C'\fR macro, but using it is utterly
|
|
|
+pointless, I assure you.
|
|
|
+.PP
|
|
|
+Example: Register an atexit handler to destroy the default loop, so any
|
|
|
+cleanup functions are called.
|
|
|
+.PP
|
|
|
+.Vb 5
|
|
|
+\& static void
|
|
|
+\& program_exits (void)
|
|
|
+\& {
|
|
|
+\& ev_loop_destroy (EV_DEFAULT_UC);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ...
|
|
|
+\& atexit (program_exits);
|
|
|
+.Ve
|
|
|
+.ie n .SS """ev_async"" \- how to wake up an event loop"
|
|
|
+.el .SS "\f(CWev_async\fP \- how to wake up an event loop"
|
|
|
+.IX Subsection "ev_async - how to wake up an event loop"
|
|
|
+In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other
|
|
|
+asynchronous sources such as signal handlers (as opposed to multiple event
|
|
|
+loops \- those are of course safe to use in different threads).
|
|
|
+.PP
|
|
|
+Sometimes, however, you need to wake up an event loop you do not control,
|
|
|
+for example because it belongs to another thread. This is what \f(CW\*(C`ev_async\*(C'\fR
|
|
|
+watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you can signal
|
|
|
+it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal safe.
|
|
|
+.PP
|
|
|
+This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals,
|
|
|
+too, are asynchronous in nature, and signals, too, will be compressed
|
|
|
+(i.e. the number of callback invocations may be less than the number of
|
|
|
+\&\f(CW\*(C`ev_async_send\*(C'\fR calls). In fact, you could use signal watchers as a kind
|
|
|
+of \*(L"global async watchers\*(R" by using a watcher on an otherwise unused
|
|
|
+signal, and \f(CW\*(C`ev_feed_signal\*(C'\fR to signal this watcher from another thread,
|
|
|
+even without knowing which loop owns the signal.
|
|
|
+.PP
|
|
|
+\fIQueueing\fR
|
|
|
+.IX Subsection "Queueing"
|
|
|
+.PP
|
|
|
+\&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason
|
|
|
+is that the author does not know of a simple (or any) algorithm for a
|
|
|
+multiple-writer-single-reader queue that works in all cases and doesn't
|
|
|
+need elaborate support such as pthreads or unportable memory access
|
|
|
+semantics.
|
|
|
+.PP
|
|
|
+That means that if you want to queue data, you have to provide your own
|
|
|
+queue. But at least I can tell you how to implement locking around your
|
|
|
+queue:
|
|
|
+.IP "queueing from a signal handler context" 4
|
|
|
+.IX Item "queueing from a signal handler context"
|
|
|
+To implement race-free queueing, you simply add to the queue in the signal
|
|
|
+handler but you block the signal handler in the watcher callback. Here is
|
|
|
+an example that does that for some fictitious \s-1SIGUSR1\s0 handler:
|
|
|
+.Sp
|
|
|
+.Vb 1
|
|
|
+\& static ev_async mysig;
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& sigusr1_handler (void)
|
|
|
+\& {
|
|
|
+\& sometype data;
|
|
|
+\&
|
|
|
+\& // no locking etc.
|
|
|
+\& queue_put (data);
|
|
|
+\& ev_async_send (EV_DEFAULT_ &mysig);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& mysig_cb (EV_P_ ev_async *w, int revents)
|
|
|
+\& {
|
|
|
+\& sometype data;
|
|
|
+\& sigset_t block, prev;
|
|
|
+\&
|
|
|
+\& sigemptyset (&block);
|
|
|
+\& sigaddset (&block, SIGUSR1);
|
|
|
+\& sigprocmask (SIG_BLOCK, &block, &prev);
|
|
|
+\&
|
|
|
+\& while (queue_get (&data))
|
|
|
+\& process (data);
|
|
|
+\&
|
|
|
+\& if (sigismember (&prev, SIGUSR1)
|
|
|
+\& sigprocmask (SIG_UNBLOCK, &block, 0);
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+(Note: pthreads in theory requires you to use \f(CW\*(C`pthread_setmask\*(C'\fR
|
|
|
+instead of \f(CW\*(C`sigprocmask\*(C'\fR when you use threads, but libev doesn't do it
|
|
|
+either...).
|
|
|
+.IP "queueing from a thread context" 4
|
|
|
+.IX Item "queueing from a thread context"
|
|
|
+The strategy for threads is different, as you cannot (easily) block
|
|
|
+threads but you can easily preempt them, so to queue safely you need to
|
|
|
+employ a traditional mutex lock, such as in this pthread example:
|
|
|
+.Sp
|
|
|
+.Vb 2
|
|
|
+\& static ev_async mysig;
|
|
|
+\& static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& otherthread (void)
|
|
|
+\& {
|
|
|
+\& // only need to lock the actual queueing operation
|
|
|
+\& pthread_mutex_lock (&mymutex);
|
|
|
+\& queue_put (data);
|
|
|
+\& pthread_mutex_unlock (&mymutex);
|
|
|
+\&
|
|
|
+\& ev_async_send (EV_DEFAULT_ &mysig);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& mysig_cb (EV_P_ ev_async *w, int revents)
|
|
|
+\& {
|
|
|
+\& pthread_mutex_lock (&mymutex);
|
|
|
+\&
|
|
|
+\& while (queue_get (&data))
|
|
|
+\& process (data);
|
|
|
+\&
|
|
|
+\& pthread_mutex_unlock (&mymutex);
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+\fIWatcher-Specific Functions and Data Members\fR
|
|
|
+.IX Subsection "Watcher-Specific Functions and Data Members"
|
|
|
+.IP "ev_async_init (ev_async *, callback)" 4
|
|
|
+.IX Item "ev_async_init (ev_async *, callback)"
|
|
|
+Initialises and configures the async watcher \- it has no parameters of any
|
|
|
+kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless,
|
|
|
+trust me.
|
|
|
+.IP "ev_async_send (loop, ev_async *)" 4
|
|
|
+.IX Item "ev_async_send (loop, ev_async *)"
|
|
|
+Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds
|
|
|
+an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop, and instantly
|
|
|
+returns.
|
|
|
+.Sp
|
|
|
+Unlike \f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads,
|
|
|
+signal or similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the
|
|
|
+embedding section below on what exactly this means).
|
|
|
+.Sp
|
|
|
+Note that, as with other watchers in libev, multiple events might get
|
|
|
+compressed into a single callback invocation (another way to look at
|
|
|
+this is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered: they are set on
|
|
|
+\&\f(CW\*(C`ev_async_send\*(C'\fR, reset when the event loop detects that).
|
|
|
+.Sp
|
|
|
+This call incurs the overhead of at most one extra system call per event
|
|
|
+loop iteration, if the event loop is blocked, and no syscall at all if
|
|
|
+the event loop (or your program) is processing events. That means that
|
|
|
+repeated calls are basically free (there is no need to avoid calls for
|
|
|
+performance reasons) and that the overhead becomes smaller (typically
|
|
|
+zero) under load.
|
|
|
+.IP "bool = ev_async_pending (ev_async *)" 4
|
|
|
+.IX Item "bool = ev_async_pending (ev_async *)"
|
|
|
+Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the
|
|
|
+watcher but the event has not yet been processed (or even noted) by the
|
|
|
+event loop.
|
|
|
+.Sp
|
|
|
+\&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When
|
|
|
+the loop iterates next and checks for the watcher to have become active,
|
|
|
+it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very
|
|
|
+quickly check whether invoking the loop might be a good idea.
|
|
|
+.Sp
|
|
|
+Not that this does \fInot\fR check whether the watcher itself is pending,
|
|
|
+only whether it has been requested to make this watcher pending: there
|
|
|
+is a time window between the event loop checking and resetting the async
|
|
|
+notification, and the callback being invoked.
|
|
|
+.SH "OTHER FUNCTIONS"
|
|
|
+.IX Header "OTHER FUNCTIONS"
|
|
|
+There are some other functions of possible interest. Described. Here. Now.
|
|
|
+.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
|
|
|
+.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
|
|
|
+This function combines a simple timer and an I/O watcher, calls your
|
|
|
+callback on whichever event happens first and automatically stops both
|
|
|
+watchers. This is useful if you want to wait for a single event on an fd
|
|
|
+or timeout without having to allocate/configure/start/stop/free one or
|
|
|
+more watchers yourself.
|
|
|
+.Sp
|
|
|
+If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and the
|
|
|
+\&\f(CW\*(C`events\*(C'\fR argument is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for
|
|
|
+the given \f(CW\*(C`fd\*(C'\fR and \f(CW\*(C`events\*(C'\fR set will be created and started.
|
|
|
+.Sp
|
|
|
+If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be
|
|
|
+started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and
|
|
|
+repeat = 0) will be started. \f(CW0\fR is a valid timeout.
|
|
|
+.Sp
|
|
|
+The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and is
|
|
|
+passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of
|
|
|
+\&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMER\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR
|
|
|
+value passed to \f(CW\*(C`ev_once\*(C'\fR. Note that it is possible to receive \fIboth\fR
|
|
|
+a timeout and an io event at the same time \- you probably should give io
|
|
|
+events precedence.
|
|
|
+.Sp
|
|
|
+Example: wait up to ten seconds for data to appear on \s-1STDIN_FILENO.\s0
|
|
|
+.Sp
|
|
|
+.Vb 7
|
|
|
+\& static void stdin_ready (int revents, void *arg)
|
|
|
+\& {
|
|
|
+\& if (revents & EV_READ)
|
|
|
+\& /* stdin might have data for us, joy! */;
|
|
|
+\& else if (revents & EV_TIMER)
|
|
|
+\& /* doh, nothing entered */;
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
|
|
|
+.Ve
|
|
|
+.IP "ev_feed_fd_event (loop, int fd, int revents)" 4
|
|
|
+.IX Item "ev_feed_fd_event (loop, int fd, int revents)"
|
|
|
+Feed an event on the given fd, as if a file descriptor backend detected
|
|
|
+the given events.
|
|
|
+.IP "ev_feed_signal_event (loop, int signum)" 4
|
|
|
+.IX Item "ev_feed_signal_event (loop, int signum)"
|
|
|
+Feed an event as if the given signal occurred. See also \f(CW\*(C`ev_feed_signal\*(C'\fR,
|
|
|
+which is async-safe.
|
|
|
+.SH "COMMON OR USEFUL IDIOMS (OR BOTH)"
|
|
|
+.IX Header "COMMON OR USEFUL IDIOMS (OR BOTH)"
|
|
|
+This section explains some common idioms that are not immediately
|
|
|
+obvious. Note that examples are sprinkled over the whole manual, and this
|
|
|
+section only contains stuff that wouldn't fit anywhere else.
|
|
|
+.SS "\s-1ASSOCIATING CUSTOM DATA WITH A WATCHER\s0"
|
|
|
+.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
|
|
|
+Each watcher has, by default, a \f(CW\*(C`void *data\*(C'\fR member that you can read
|
|
|
+or modify at any time: libev will completely ignore it. This can be used
|
|
|
+to associate arbitrary data with your watcher. If you need more data and
|
|
|
+don't want to allocate memory separately and store a pointer to it in that
|
|
|
+data member, you can also \*(L"subclass\*(R" the watcher type and provide your own
|
|
|
+data:
|
|
|
+.PP
|
|
|
+.Vb 7
|
|
|
+\& struct my_io
|
|
|
+\& {
|
|
|
+\& ev_io io;
|
|
|
+\& int otherfd;
|
|
|
+\& void *somedata;
|
|
|
+\& struct whatever *mostinteresting;
|
|
|
+\& };
|
|
|
+\&
|
|
|
+\& ...
|
|
|
+\& struct my_io w;
|
|
|
+\& ev_io_init (&w.io, my_cb, fd, EV_READ);
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+And since your callback will be called with a pointer to the watcher, you
|
|
|
+can cast it back to your own type:
|
|
|
+.PP
|
|
|
+.Vb 5
|
|
|
+\& static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
|
|
|
+\& {
|
|
|
+\& struct my_io *w = (struct my_io *)w_;
|
|
|
+\& ...
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+More interesting and less C\-conformant ways of casting your callback
|
|
|
+function type instead have been omitted.
|
|
|
+.SS "\s-1BUILDING YOUR OWN COMPOSITE WATCHERS\s0"
|
|
|
+.IX Subsection "BUILDING YOUR OWN COMPOSITE WATCHERS"
|
|
|
+Another common scenario is to use some data structure with multiple
|
|
|
+embedded watchers, in effect creating your own watcher that combines
|
|
|
+multiple libev event sources into one \*(L"super-watcher\*(R":
|
|
|
+.PP
|
|
|
+.Vb 6
|
|
|
+\& struct my_biggy
|
|
|
+\& {
|
|
|
+\& int some_data;
|
|
|
+\& ev_timer t1;
|
|
|
+\& ev_timer t2;
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more
|
|
|
+complicated: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct in
|
|
|
+the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies or \*(C+ coders), or you need
|
|
|
+to use some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for
|
|
|
+real programmers):
|
|
|
+.PP
|
|
|
+.Vb 1
|
|
|
+\& #include <stddef.h>
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& t1_cb (EV_P_ ev_timer *w, int revents)
|
|
|
+\& {
|
|
|
+\& struct my_biggy big = (struct my_biggy *)
|
|
|
+\& (((char *)w) \- offsetof (struct my_biggy, t1));
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& t2_cb (EV_P_ ev_timer *w, int revents)
|
|
|
+\& {
|
|
|
+\& struct my_biggy big = (struct my_biggy *)
|
|
|
+\& (((char *)w) \- offsetof (struct my_biggy, t2));
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.SS "\s-1AVOIDING FINISHING BEFORE RETURNING\s0"
|
|
|
+.IX Subsection "AVOIDING FINISHING BEFORE RETURNING"
|
|
|
+Often you have structures like this in event-based programs:
|
|
|
+.PP
|
|
|
+.Vb 4
|
|
|
+\& callback ()
|
|
|
+\& {
|
|
|
+\& free (request);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& request = start_new_request (..., callback);
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+The intent is to start some \*(L"lengthy\*(R" operation. The \f(CW\*(C`request\*(C'\fR could be
|
|
|
+used to cancel the operation, or do other things with it.
|
|
|
+.PP
|
|
|
+It's not uncommon to have code paths in \f(CW\*(C`start_new_request\*(C'\fR that
|
|
|
+immediately invoke the callback, for example, to report errors. Or you add
|
|
|
+some caching layer that finds that it can skip the lengthy aspects of the
|
|
|
+operation and simply invoke the callback with the result.
|
|
|
+.PP
|
|
|
+The problem here is that this will happen \fIbefore\fR \f(CW\*(C`start_new_request\*(C'\fR
|
|
|
+has returned, so \f(CW\*(C`request\*(C'\fR is not set.
|
|
|
+.PP
|
|
|
+Even if you pass the request by some safer means to the callback, you
|
|
|
+might want to do something to the request after starting it, such as
|
|
|
+canceling it, which probably isn't working so well when the callback has
|
|
|
+already been invoked.
|
|
|
+.PP
|
|
|
+A common way around all these issues is to make sure that
|
|
|
+\&\f(CW\*(C`start_new_request\*(C'\fR \fIalways\fR returns before the callback is invoked. If
|
|
|
+\&\f(CW\*(C`start_new_request\*(C'\fR immediately knows the result, it can artificially
|
|
|
+delay invoking the callback by using a \f(CW\*(C`prepare\*(C'\fR or \f(CW\*(C`idle\*(C'\fR watcher for
|
|
|
+example, or more sneakily, by reusing an existing (stopped) watcher and
|
|
|
+pushing it into the pending queue:
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& ev_set_cb (watcher, callback);
|
|
|
+\& ev_feed_event (EV_A_ watcher, 0);
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+This way, \f(CW\*(C`start_new_request\*(C'\fR can safely return before the callback is
|
|
|
+invoked, while not delaying callback invocation too much.
|
|
|
+.SS "\s-1MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS\s0"
|
|
|
+.IX Subsection "MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS"
|
|
|
+Often (especially in \s-1GUI\s0 toolkits) there are places where you have
|
|
|
+\&\fImodal\fR interaction, which is most easily implemented by recursively
|
|
|
+invoking \f(CW\*(C`ev_run\*(C'\fR.
|
|
|
+.PP
|
|
|
+This brings the problem of exiting \- a callback might want to finish the
|
|
|
+main \f(CW\*(C`ev_run\*(C'\fR call, but not the nested one (e.g. user clicked \*(L"Quit\*(R", but
|
|
|
+a modal \*(L"Are you sure?\*(R" dialog is still waiting), or just the nested one
|
|
|
+and not the main one (e.g. user clocked \*(L"Ok\*(R" in a modal dialog), or some
|
|
|
+other combination: In these cases, a simple \f(CW\*(C`ev_break\*(C'\fR will not work.
|
|
|
+.PP
|
|
|
+The solution is to maintain \*(L"break this loop\*(R" variable for each \f(CW\*(C`ev_run\*(C'\fR
|
|
|
+invocation, and use a loop around \f(CW\*(C`ev_run\*(C'\fR until the condition is
|
|
|
+triggered, using \f(CW\*(C`EVRUN_ONCE\*(C'\fR:
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& // main loop
|
|
|
+\& int exit_main_loop = 0;
|
|
|
+\&
|
|
|
+\& while (!exit_main_loop)
|
|
|
+\& ev_run (EV_DEFAULT_ EVRUN_ONCE);
|
|
|
+\&
|
|
|
+\& // in a modal watcher
|
|
|
+\& int exit_nested_loop = 0;
|
|
|
+\&
|
|
|
+\& while (!exit_nested_loop)
|
|
|
+\& ev_run (EV_A_ EVRUN_ONCE);
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+To exit from any of these loops, just set the corresponding exit variable:
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& // exit modal loop
|
|
|
+\& exit_nested_loop = 1;
|
|
|
+\&
|
|
|
+\& // exit main program, after modal loop is finished
|
|
|
+\& exit_main_loop = 1;
|
|
|
+\&
|
|
|
+\& // exit both
|
|
|
+\& exit_main_loop = exit_nested_loop = 1;
|
|
|
+.Ve
|
|
|
+.SS "\s-1THREAD LOCKING EXAMPLE\s0"
|
|
|
+.IX Subsection "THREAD LOCKING EXAMPLE"
|
|
|
+Here is a fictitious example of how to run an event loop in a different
|
|
|
+thread from where callbacks are being invoked and watchers are
|
|
|
+created/added/removed.
|
|
|
+.PP
|
|
|
+For a real-world example, see the \f(CW\*(C`EV::Loop::Async\*(C'\fR perl module,
|
|
|
+which uses exactly this technique (which is suited for many high-level
|
|
|
+languages).
|
|
|
+.PP
|
|
|
+The example uses a pthread mutex to protect the loop data, a condition
|
|
|
+variable to wait for callback invocations, an async watcher to notify the
|
|
|
+event loop thread and an unspecified mechanism to wake up the main thread.
|
|
|
+.PP
|
|
|
+First, you need to associate some data with the event loop:
|
|
|
+.PP
|
|
|
+.Vb 6
|
|
|
+\& typedef struct {
|
|
|
+\& mutex_t lock; /* global loop lock */
|
|
|
+\& ev_async async_w;
|
|
|
+\& thread_t tid;
|
|
|
+\& cond_t invoke_cv;
|
|
|
+\& } userdata;
|
|
|
+\&
|
|
|
+\& void prepare_loop (EV_P)
|
|
|
+\& {
|
|
|
+\& // for simplicity, we use a static userdata struct.
|
|
|
+\& static userdata u;
|
|
|
+\&
|
|
|
+\& ev_async_init (&u\->async_w, async_cb);
|
|
|
+\& ev_async_start (EV_A_ &u\->async_w);
|
|
|
+\&
|
|
|
+\& pthread_mutex_init (&u\->lock, 0);
|
|
|
+\& pthread_cond_init (&u\->invoke_cv, 0);
|
|
|
+\&
|
|
|
+\& // now associate this with the loop
|
|
|
+\& ev_set_userdata (EV_A_ u);
|
|
|
+\& ev_set_invoke_pending_cb (EV_A_ l_invoke);
|
|
|
+\& ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
|
|
|
+\&
|
|
|
+\& // then create the thread running ev_run
|
|
|
+\& pthread_create (&u\->tid, 0, l_run, EV_A);
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used
|
|
|
+solely to wake up the event loop so it takes notice of any new watchers
|
|
|
+that might have been added:
|
|
|
+.PP
|
|
|
+.Vb 5
|
|
|
+\& static void
|
|
|
+\& async_cb (EV_P_ ev_async *w, int revents)
|
|
|
+\& {
|
|
|
+\& // just used for the side effects
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+The \f(CW\*(C`l_release\*(C'\fR and \f(CW\*(C`l_acquire\*(C'\fR callbacks simply unlock/lock the mutex
|
|
|
+protecting the loop data, respectively.
|
|
|
+.PP
|
|
|
+.Vb 6
|
|
|
+\& static void
|
|
|
+\& l_release (EV_P)
|
|
|
+\& {
|
|
|
+\& userdata *u = ev_userdata (EV_A);
|
|
|
+\& pthread_mutex_unlock (&u\->lock);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& static void
|
|
|
+\& l_acquire (EV_P)
|
|
|
+\& {
|
|
|
+\& userdata *u = ev_userdata (EV_A);
|
|
|
+\& pthread_mutex_lock (&u\->lock);
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+The event loop thread first acquires the mutex, and then jumps straight
|
|
|
+into \f(CW\*(C`ev_run\*(C'\fR:
|
|
|
+.PP
|
|
|
+.Vb 4
|
|
|
+\& void *
|
|
|
+\& l_run (void *thr_arg)
|
|
|
+\& {
|
|
|
+\& struct ev_loop *loop = (struct ev_loop *)thr_arg;
|
|
|
+\&
|
|
|
+\& l_acquire (EV_A);
|
|
|
+\& pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
|
|
|
+\& ev_run (EV_A_ 0);
|
|
|
+\& l_release (EV_A);
|
|
|
+\&
|
|
|
+\& return 0;
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Instead of invoking all pending watchers, the \f(CW\*(C`l_invoke\*(C'\fR callback will
|
|
|
+signal the main thread via some unspecified mechanism (signals? pipe
|
|
|
+writes? \f(CW\*(C`Async::Interrupt\*(C'\fR?) and then waits until all pending watchers
|
|
|
+have been called (in a while loop because a) spurious wakeups are possible
|
|
|
+and b) skipping inter-thread-communication when there are no pending
|
|
|
+watchers is very beneficial):
|
|
|
+.PP
|
|
|
+.Vb 4
|
|
|
+\& static void
|
|
|
+\& l_invoke (EV_P)
|
|
|
+\& {
|
|
|
+\& userdata *u = ev_userdata (EV_A);
|
|
|
+\&
|
|
|
+\& while (ev_pending_count (EV_A))
|
|
|
+\& {
|
|
|
+\& wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
|
|
|
+\& pthread_cond_wait (&u\->invoke_cv, &u\->lock);
|
|
|
+\& }
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Now, whenever the main thread gets told to invoke pending watchers, it
|
|
|
+will grab the lock, call \f(CW\*(C`ev_invoke_pending\*(C'\fR and then signal the loop
|
|
|
+thread to continue:
|
|
|
+.PP
|
|
|
+.Vb 4
|
|
|
+\& static void
|
|
|
+\& real_invoke_pending (EV_P)
|
|
|
+\& {
|
|
|
+\& userdata *u = ev_userdata (EV_A);
|
|
|
+\&
|
|
|
+\& pthread_mutex_lock (&u\->lock);
|
|
|
+\& ev_invoke_pending (EV_A);
|
|
|
+\& pthread_cond_signal (&u\->invoke_cv);
|
|
|
+\& pthread_mutex_unlock (&u\->lock);
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Whenever you want to start/stop a watcher or do other modifications to an
|
|
|
+event loop, you will now have to lock:
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& ev_timer timeout_watcher;
|
|
|
+\& userdata *u = ev_userdata (EV_A);
|
|
|
+\&
|
|
|
+\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
|
|
|
+\&
|
|
|
+\& pthread_mutex_lock (&u\->lock);
|
|
|
+\& ev_timer_start (EV_A_ &timeout_watcher);
|
|
|
+\& ev_async_send (EV_A_ &u\->async_w);
|
|
|
+\& pthread_mutex_unlock (&u\->lock);
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Note that sending the \f(CW\*(C`ev_async\*(C'\fR watcher is required because otherwise
|
|
|
+an event loop currently blocking in the kernel will have no knowledge
|
|
|
+about the newly added timer. By waking up the loop it will pick up any new
|
|
|
+watchers in the next event loop iteration.
|
|
|
+.SS "\s-1THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS\s0"
|
|
|
+.IX Subsection "THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS"
|
|
|
+While the overhead of a callback that e.g. schedules a thread is small, it
|
|
|
+is still an overhead. If you embed libev, and your main usage is with some
|
|
|
+kind of threads or coroutines, you might want to customise libev so that
|
|
|
+doesn't need callbacks anymore.
|
|
|
+.PP
|
|
|
+Imagine you have coroutines that you can switch to using a function
|
|
|
+\&\f(CW\*(C`switch_to (coro)\*(C'\fR, that libev runs in a coroutine called \f(CW\*(C`libev_coro\*(C'\fR
|
|
|
+and that due to some magic, the currently active coroutine is stored in a
|
|
|
+global called \f(CW\*(C`current_coro\*(C'\fR. Then you can build your own \*(L"wait for libev
|
|
|
+event\*(R" primitive by changing \f(CW\*(C`EV_CB_DECLARE\*(C'\fR and \f(CW\*(C`EV_CB_INVOKE\*(C'\fR (note
|
|
|
+the differing \f(CW\*(C`;\*(C'\fR conventions):
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& #define EV_CB_DECLARE(type) struct my_coro *cb;
|
|
|
+\& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb)
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+That means instead of having a C callback function, you store the
|
|
|
+coroutine to switch to in each watcher, and instead of having libev call
|
|
|
+your callback, you instead have it switch to that coroutine.
|
|
|
+.PP
|
|
|
+A coroutine might now wait for an event with a function called
|
|
|
+\&\f(CW\*(C`wait_for_event\*(C'\fR. (the watcher needs to be started, as always, but it doesn't
|
|
|
+matter when, or whether the watcher is active or not when this function is
|
|
|
+called):
|
|
|
+.PP
|
|
|
+.Vb 6
|
|
|
+\& void
|
|
|
+\& wait_for_event (ev_watcher *w)
|
|
|
+\& {
|
|
|
+\& ev_set_cb (w, current_coro);
|
|
|
+\& switch_to (libev_coro);
|
|
|
+\& }
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+That basically suspends the coroutine inside \f(CW\*(C`wait_for_event\*(C'\fR and
|
|
|
+continues the libev coroutine, which, when appropriate, switches back to
|
|
|
+this or any other coroutine.
|
|
|
+.PP
|
|
|
+You can do similar tricks if you have, say, threads with an event queue \-
|
|
|
+instead of storing a coroutine, you store the queue object and instead of
|
|
|
+switching to a coroutine, you push the watcher onto the queue and notify
|
|
|
+any waiters.
|
|
|
+.PP
|
|
|
+To embed libev, see \*(L"\s-1EMBEDDING\*(R"\s0, but in short, it's easiest to create two
|
|
|
+files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files:
|
|
|
+.PP
|
|
|
+.Vb 4
|
|
|
+\& // my_ev.h
|
|
|
+\& #define EV_CB_DECLARE(type) struct my_coro *cb;
|
|
|
+\& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb)
|
|
|
+\& #include "../libev/ev.h"
|
|
|
+\&
|
|
|
+\& // my_ev.c
|
|
|
+\& #define EV_H "my_ev.h"
|
|
|
+\& #include "../libev/ev.c"
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+And then use \fImy_ev.h\fR when you would normally use \fIev.h\fR, and compile
|
|
|
+\&\fImy_ev.c\fR into your project. When properly specifying include paths, you
|
|
|
+can even use \fIev.h\fR as header file name directly.
|
|
|
+.SH "LIBEVENT EMULATION"
|
|
|
+.IX Header "LIBEVENT EMULATION"
|
|
|
+Libev offers a compatibility emulation layer for libevent. It cannot
|
|
|
+emulate the internals of libevent, so here are some usage hints:
|
|
|
+.IP "\(bu" 4
|
|
|
+Only the libevent\-1.4.1\-beta \s-1API\s0 is being emulated.
|
|
|
+.Sp
|
|
|
+This was the newest libevent version available when libev was implemented,
|
|
|
+and is still mostly unchanged in 2010.
|
|
|
+.IP "\(bu" 4
|
|
|
+Use it by including <event.h>, as usual.
|
|
|
+.IP "\(bu" 4
|
|
|
+The following members are fully supported: ev_base, ev_callback,
|
|
|
+ev_arg, ev_fd, ev_res, ev_events.
|
|
|
+.IP "\(bu" 4
|
|
|
+Avoid using ev_flags and the EVLIST_*\-macros, while it is
|
|
|
+maintained by libev, it does not work exactly the same way as in libevent (consider
|
|
|
+it a private \s-1API\s0).
|
|
|
+.IP "\(bu" 4
|
|
|
+Priorities are not currently supported. Initialising priorities
|
|
|
+will fail and all watchers will have the same priority, even though there
|
|
|
+is an ev_pri field.
|
|
|
+.IP "\(bu" 4
|
|
|
+In libevent, the last base created gets the signals, in libev, the
|
|
|
+base that registered the signal gets the signals.
|
|
|
+.IP "\(bu" 4
|
|
|
+Other members are not supported.
|
|
|
+.IP "\(bu" 4
|
|
|
+The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need
|
|
|
+to use the libev header file and library.
|
|
|
+.SH "\*(C+ SUPPORT"
|
|
|
+.IX Header " SUPPORT"
|
|
|
+.SS "C \s-1API\s0"
|
|
|
+.IX Subsection "C API"
|
|
|
+The normal C \s-1API\s0 should work fine when used from \*(C+: both ev.h and the
|
|
|
+libev sources can be compiled as \*(C+. Therefore, code that uses the C \s-1API\s0
|
|
|
+will work fine.
|
|
|
+.PP
|
|
|
+Proper exception specifications might have to be added to callbacks passed
|
|
|
+to libev: exceptions may be thrown only from watcher callbacks, all
|
|
|
+other callbacks (allocator, syserr, loop acquire/release and periodic
|
|
|
+reschedule callbacks) must not throw exceptions, and might need a \f(CW\*(C`throw
|
|
|
+()\*(C'\fR specification. If you have code that needs to be compiled as both C
|
|
|
+and \*(C+ you can use the \f(CW\*(C`EV_THROW\*(C'\fR macro for this:
|
|
|
+.PP
|
|
|
+.Vb 6
|
|
|
+\& static void
|
|
|
+\& fatal_error (const char *msg) EV_THROW
|
|
|
+\& {
|
|
|
+\& perror (msg);
|
|
|
+\& abort ();
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ...
|
|
|
+\& ev_set_syserr_cb (fatal_error);
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+The only \s-1API\s0 functions that can currently throw exceptions are \f(CW\*(C`ev_run\*(C'\fR,
|
|
|
+\&\f(CW\*(C`ev_invoke\*(C'\fR, \f(CW\*(C`ev_invoke_pending\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR (the latter
|
|
|
+because it runs cleanup watchers).
|
|
|
+.PP
|
|
|
+Throwing exceptions in watcher callbacks is only supported if libev itself
|
|
|
+is compiled with a \*(C+ compiler or your C and \*(C+ environments allow
|
|
|
+throwing exceptions through C libraries (most do).
|
|
|
+.SS "\*(C+ \s-1API\s0"
|
|
|
+.IX Subsection " API"
|
|
|
+Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
|
|
|
+you to use some convenience methods to start/stop watchers and also change
|
|
|
+the callback model to a model using method callbacks on objects.
|
|
|
+.PP
|
|
|
+To use it,
|
|
|
+.PP
|
|
|
+.Vb 1
|
|
|
+\& #include <ev++.h>
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+This automatically includes \fIev.h\fR and puts all of its definitions (many
|
|
|
+of them macros) into the global namespace. All \*(C+ specific things are
|
|
|
+put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
|
|
|
+options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
|
|
|
+.PP
|
|
|
+Care has been taken to keep the overhead low. The only data member the \*(C+
|
|
|
+classes add (compared to plain C\-style watchers) is the event loop pointer
|
|
|
+that the watcher is associated with (or no additional members at all if
|
|
|
+you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
|
|
|
+.PP
|
|
|
+Currently, functions, static and non-static member functions and classes
|
|
|
+with \f(CW\*(C`operator ()\*(C'\fR can be used as callbacks. Other types should be easy
|
|
|
+to add as long as they only need one additional pointer for context. If
|
|
|
+you need support for other types of functors please contact the author
|
|
|
+(preferably after implementing it).
|
|
|
+.PP
|
|
|
+For all this to work, your \*(C+ compiler either has to use the same calling
|
|
|
+conventions as your C compiler (for static member functions), or you have
|
|
|
+to embed libev and compile libev itself as \*(C+.
|
|
|
+.PP
|
|
|
+Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
|
|
|
+.ie n .IP """ev::READ"", ""ev::WRITE"" etc." 4
|
|
|
+.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
|
|
|
+.IX Item "ev::READ, ev::WRITE etc."
|
|
|
+These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
|
|
|
+macros from \fIev.h\fR.
|
|
|
+.ie n .IP """ev::tstamp"", ""ev::now""" 4
|
|
|
+.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
|
|
|
+.IX Item "ev::tstamp, ev::now"
|
|
|
+Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
|
|
|
+.ie n .IP """ev::io"", ""ev::timer"", ""ev::periodic"", ""ev::idle"", ""ev::sig"" etc." 4
|
|
|
+.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
|
|
|
+.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
|
|
|
+For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
|
|
|
+the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
|
|
|
+which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
|
|
|
+defined by many implementations.
|
|
|
+.Sp
|
|
|
+All of those classes have these methods:
|
|
|
+.RS 4
|
|
|
+.IP "ev::TYPE::TYPE ()" 4
|
|
|
+.IX Item "ev::TYPE::TYPE ()"
|
|
|
+.PD 0
|
|
|
+.IP "ev::TYPE::TYPE (loop)" 4
|
|
|
+.IX Item "ev::TYPE::TYPE (loop)"
|
|
|
+.IP "ev::TYPE::~TYPE" 4
|
|
|
+.IX Item "ev::TYPE::~TYPE"
|
|
|
+.PD
|
|
|
+The constructor (optionally) takes an event loop to associate the watcher
|
|
|
+with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
|
|
|
+.Sp
|
|
|
+The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
|
|
|
+\&\f(CW\*(C`set\*(C'\fR method before starting it.
|
|
|
+.Sp
|
|
|
+It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
|
|
|
+method to set a callback before you can start the watcher.
|
|
|
+.Sp
|
|
|
+(The reason why you have to use a method is a limitation in \*(C+ which does
|
|
|
+not allow explicit template arguments for constructors).
|
|
|
+.Sp
|
|
|
+The destructor automatically stops the watcher if it is active.
|
|
|
+.IP "w\->set<class, &class::method> (object *)" 4
|
|
|
+.IX Item "w->set<class, &class::method> (object *)"
|
|
|
+This method sets the callback method to call. The method has to have a
|
|
|
+signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
|
|
|
+first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
|
|
|
+parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
|
|
|
+.Sp
|
|
|
+This method synthesizes efficient thunking code to call your method from
|
|
|
+the C callback that libev requires. If your compiler can inline your
|
|
|
+callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
|
|
|
+your compiler is good :), then the method will be fully inlined into the
|
|
|
+thunking function, making it as fast as a direct C callback.
|
|
|
+.Sp
|
|
|
+Example: simple class declaration and watcher initialisation
|
|
|
+.Sp
|
|
|
+.Vb 4
|
|
|
+\& struct myclass
|
|
|
+\& {
|
|
|
+\& void io_cb (ev::io &w, int revents) { }
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& myclass obj;
|
|
|
+\& ev::io iow;
|
|
|
+\& iow.set <myclass, &myclass::io_cb> (&obj);
|
|
|
+.Ve
|
|
|
+.IP "w\->set (object *)" 4
|
|
|
+.IX Item "w->set (object *)"
|
|
|
+This is a variation of a method callback \- leaving out the method to call
|
|
|
+will default the method to \f(CW\*(C`operator ()\*(C'\fR, which makes it possible to use
|
|
|
+functor objects without having to manually specify the \f(CW\*(C`operator ()\*(C'\fR all
|
|
|
+the time. Incidentally, you can then also leave out the template argument
|
|
|
+list.
|
|
|
+.Sp
|
|
|
+The \f(CW\*(C`operator ()\*(C'\fR method prototype must be \f(CW\*(C`void operator ()(watcher &w,
|
|
|
+int revents)\*(C'\fR.
|
|
|
+.Sp
|
|
|
+See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
|
|
|
+.Sp
|
|
|
+Example: use a functor object as callback.
|
|
|
+.Sp
|
|
|
+.Vb 7
|
|
|
+\& struct myfunctor
|
|
|
+\& {
|
|
|
+\& void operator() (ev::io &w, int revents)
|
|
|
+\& {
|
|
|
+\& ...
|
|
|
+\& }
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& myfunctor f;
|
|
|
+\&
|
|
|
+\& ev::io w;
|
|
|
+\& w.set (&f);
|
|
|
+.Ve
|
|
|
+.IP "w\->set<function> (void *data = 0)" 4
|
|
|
+.IX Item "w->set<function> (void *data = 0)"
|
|
|
+Also sets a callback, but uses a static method or plain function as
|
|
|
+callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
|
|
|
+\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
|
|
|
+.Sp
|
|
|
+The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
|
|
|
+.Sp
|
|
|
+See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
|
|
|
+.Sp
|
|
|
+Example: Use a plain function as callback.
|
|
|
+.Sp
|
|
|
+.Vb 2
|
|
|
+\& static void io_cb (ev::io &w, int revents) { }
|
|
|
+\& iow.set <io_cb> ();
|
|
|
+.Ve
|
|
|
+.IP "w\->set (loop)" 4
|
|
|
+.IX Item "w->set (loop)"
|
|
|
+Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
|
|
|
+do this when the watcher is inactive (and not pending either).
|
|
|
+.IP "w\->set ([arguments])" 4
|
|
|
+.IX Item "w->set ([arguments])"
|
|
|
+Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR (except for \f(CW\*(C`ev::embed\*(C'\fR watchers>),
|
|
|
+with the same arguments. Either this method or a suitable start method
|
|
|
+must be called at least once. Unlike the C counterpart, an active watcher
|
|
|
+gets automatically stopped and restarted when reconfiguring it with this
|
|
|
+method.
|
|
|
+.Sp
|
|
|
+For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid
|
|
|
+clashing with the \f(CW\*(C`set (loop)\*(C'\fR method.
|
|
|
+.IP "w\->start ()" 4
|
|
|
+.IX Item "w->start ()"
|
|
|
+Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
|
|
|
+constructor already stores the event loop.
|
|
|
+.IP "w\->start ([arguments])" 4
|
|
|
+.IX Item "w->start ([arguments])"
|
|
|
+Instead of calling \f(CW\*(C`set\*(C'\fR and \f(CW\*(C`start\*(C'\fR methods separately, it is often
|
|
|
+convenient to wrap them in one call. Uses the same type of arguments as
|
|
|
+the configure \f(CW\*(C`set\*(C'\fR method of the watcher.
|
|
|
+.IP "w\->stop ()" 4
|
|
|
+.IX Item "w->stop ()"
|
|
|
+Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
|
|
|
+.ie n .IP "w\->again () (""ev::timer"", ""ev::periodic"" only)" 4
|
|
|
+.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
|
|
|
+.IX Item "w->again () (ev::timer, ev::periodic only)"
|
|
|
+For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
|
|
|
+\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
|
|
|
+.ie n .IP "w\->sweep () (""ev::embed"" only)" 4
|
|
|
+.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4
|
|
|
+.IX Item "w->sweep () (ev::embed only)"
|
|
|
+Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
|
|
|
+.ie n .IP "w\->update () (""ev::stat"" only)" 4
|
|
|
+.el .IP "w\->update () (\f(CWev::stat\fR only)" 4
|
|
|
+.IX Item "w->update () (ev::stat only)"
|
|
|
+Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
|
|
|
+.RE
|
|
|
+.RS 4
|
|
|
+.RE
|
|
|
+.PP
|
|
|
+Example: Define a class with two I/O and idle watchers, start the I/O
|
|
|
+watchers in the constructor.
|
|
|
+.PP
|
|
|
+.Vb 5
|
|
|
+\& class myclass
|
|
|
+\& {
|
|
|
+\& ev::io io ; void io_cb (ev::io &w, int revents);
|
|
|
+\& ev::io io2 ; void io2_cb (ev::io &w, int revents);
|
|
|
+\& ev::idle idle; void idle_cb (ev::idle &w, int revents);
|
|
|
+\&
|
|
|
+\& myclass (int fd)
|
|
|
+\& {
|
|
|
+\& io .set <myclass, &myclass::io_cb > (this);
|
|
|
+\& io2 .set <myclass, &myclass::io2_cb > (this);
|
|
|
+\& idle.set <myclass, &myclass::idle_cb> (this);
|
|
|
+\&
|
|
|
+\& io.set (fd, ev::WRITE); // configure the watcher
|
|
|
+\& io.start (); // start it whenever convenient
|
|
|
+\&
|
|
|
+\& io2.start (fd, ev::READ); // set + start in one call
|
|
|
+\& }
|
|
|
+\& };
|
|
|
+.Ve
|
|
|
+.SH "OTHER LANGUAGE BINDINGS"
|
|
|
+.IX Header "OTHER LANGUAGE BINDINGS"
|
|
|
+Libev does not offer other language bindings itself, but bindings for a
|
|
|
+number of languages exist in the form of third-party packages. If you know
|
|
|
+any interesting language binding in addition to the ones listed here, drop
|
|
|
+me a note.
|
|
|
+.IP "Perl" 4
|
|
|
+.IX Item "Perl"
|
|
|
+The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test
|
|
|
+libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module,
|
|
|
+there are additional modules that implement libev-compatible interfaces
|
|
|
+to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR, but \f(CW\*(C`AnyEvent::DNS\*(C'\fR is preferred nowadays),
|
|
|
+\&\f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the \f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR
|
|
|
+and \f(CW\*(C`EV::Glib\*(C'\fR).
|
|
|
+.Sp
|
|
|
+It can be found and installed via \s-1CPAN,\s0 its homepage is at
|
|
|
+<http://software.schmorp.de/pkg/EV>.
|
|
|
+.IP "Python" 4
|
|
|
+.IX Item "Python"
|
|
|
+Python bindings can be found at <http://code.google.com/p/pyev/>. It
|
|
|
+seems to be quite complete and well-documented.
|
|
|
+.IP "Ruby" 4
|
|
|
+.IX Item "Ruby"
|
|
|
+Tony Arcieri has written a ruby extension that offers access to a subset
|
|
|
+of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and
|
|
|
+more on top of it. It can be found via gem servers. Its homepage is at
|
|
|
+<http://rev.rubyforge.org/>.
|
|
|
+.Sp
|
|
|
+Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR
|
|
|
+makes rev work even on mingw.
|
|
|
+.IP "Haskell" 4
|
|
|
+.IX Item "Haskell"
|
|
|
+A haskell binding to libev is available at
|
|
|
+<http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev>.
|
|
|
+.IP "D" 4
|
|
|
+.IX Item "D"
|
|
|
+Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to
|
|
|
+be found at <http://www.llucax.com.ar/proj/ev.d/index.html>.
|
|
|
+.IP "Ocaml" 4
|
|
|
+.IX Item "Ocaml"
|
|
|
+Erkki Seppala has written Ocaml bindings for libev, to be found at
|
|
|
+<http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>.
|
|
|
+.IP "Lua" 4
|
|
|
+.IX Item "Lua"
|
|
|
+Brian Maher has written a partial interface to libev for lua (at the
|
|
|
+time of this writing, only \f(CW\*(C`ev_io\*(C'\fR and \f(CW\*(C`ev_timer\*(C'\fR), to be found at
|
|
|
+<http://github.com/brimworks/lua\-ev>.
|
|
|
+.IP "Javascript" 4
|
|
|
+.IX Item "Javascript"
|
|
|
+Node.js (<http://nodejs.org>) uses libev as the underlying event library.
|
|
|
+.IP "Others" 4
|
|
|
+.IX Item "Others"
|
|
|
+There are others, and I stopped counting.
|
|
|
+.SH "MACRO MAGIC"
|
|
|
+.IX Header "MACRO MAGIC"
|
|
|
+Libev can be compiled with a variety of options, the most fundamental
|
|
|
+of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
|
|
|
+functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
|
|
|
+.PP
|
|
|
+To make it easier to write programs that cope with either variant, the
|
|
|
+following macros are defined:
|
|
|
+.ie n .IP """EV_A"", ""EV_A_""" 4
|
|
|
+.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
|
|
|
+.IX Item "EV_A, EV_A_"
|
|
|
+This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
|
|
|
+loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
|
|
|
+\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
|
|
|
+.Sp
|
|
|
+.Vb 3
|
|
|
+\& ev_unref (EV_A);
|
|
|
+\& ev_timer_add (EV_A_ watcher);
|
|
|
+\& ev_run (EV_A_ 0);
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
|
|
|
+which is often provided by the following macro.
|
|
|
+.ie n .IP """EV_P"", ""EV_P_""" 4
|
|
|
+.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
|
|
|
+.IX Item "EV_P, EV_P_"
|
|
|
+This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
|
|
|
+loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
|
|
|
+\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
|
|
|
+.Sp
|
|
|
+.Vb 2
|
|
|
+\& // this is how ev_unref is being declared
|
|
|
+\& static void ev_unref (EV_P);
|
|
|
+\&
|
|
|
+\& // this is how you can declare your typical callback
|
|
|
+\& static void cb (EV_P_ ev_timer *w, int revents)
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
|
|
|
+suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
|
|
|
+.ie n .IP """EV_DEFAULT"", ""EV_DEFAULT_""" 4
|
|
|
+.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
|
|
|
+.IX Item "EV_DEFAULT, EV_DEFAULT_"
|
|
|
+Similar to the other two macros, this gives you the value of the default
|
|
|
+loop, if multiple loops are supported (\*(L"ev loop default\*(R"). The default loop
|
|
|
+will be initialised if it isn't already initialised.
|
|
|
+.Sp
|
|
|
+For non-multiplicity builds, these macros do nothing, so you always have
|
|
|
+to initialise the loop somewhere.
|
|
|
+.ie n .IP """EV_DEFAULT_UC"", ""EV_DEFAULT_UC_""" 4
|
|
|
+.el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4
|
|
|
+.IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_"
|
|
|
+Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the
|
|
|
+default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour
|
|
|
+is undefined when the default loop has not been initialised by a previous
|
|
|
+execution of \f(CW\*(C`EV_DEFAULT\*(C'\fR, \f(CW\*(C`EV_DEFAULT_\*(C'\fR or \f(CW\*(C`ev_default_init (...)\*(C'\fR.
|
|
|
+.Sp
|
|
|
+It is often prudent to use \f(CW\*(C`EV_DEFAULT\*(C'\fR when initialising the first
|
|
|
+watcher in a function but use \f(CW\*(C`EV_DEFAULT_UC\*(C'\fR afterwards.
|
|
|
+.PP
|
|
|
+Example: Declare and initialise a check watcher, utilising the above
|
|
|
+macros so it will work regardless of whether multiple loops are supported
|
|
|
+or not.
|
|
|
+.PP
|
|
|
+.Vb 5
|
|
|
+\& static void
|
|
|
+\& check_cb (EV_P_ ev_timer *w, int revents)
|
|
|
+\& {
|
|
|
+\& ev_check_stop (EV_A_ w);
|
|
|
+\& }
|
|
|
+\&
|
|
|
+\& ev_check check;
|
|
|
+\& ev_check_init (&check, check_cb);
|
|
|
+\& ev_check_start (EV_DEFAULT_ &check);
|
|
|
+\& ev_run (EV_DEFAULT_ 0);
|
|
|
+.Ve
|
|
|
+.SH "EMBEDDING"
|
|
|
+.IX Header "EMBEDDING"
|
|
|
+Libev can (and often is) directly embedded into host
|
|
|
+applications. Examples of applications that embed it include the Deliantra
|
|
|
+Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
|
|
|
+and rxvt-unicode.
|
|
|
+.PP
|
|
|
+The goal is to enable you to just copy the necessary files into your
|
|
|
+source directory without having to change even a single line in them, so
|
|
|
+you can easily upgrade by simply copying (or having a checked-out copy of
|
|
|
+libev somewhere in your source tree).
|
|
|
+.SS "\s-1FILESETS\s0"
|
|
|
+.IX Subsection "FILESETS"
|
|
|
+Depending on what features you need you need to include one or more sets of files
|
|
|
+in your application.
|
|
|
+.PP
|
|
|
+\fI\s-1CORE EVENT LOOP\s0\fR
|
|
|
+.IX Subsection "CORE EVENT LOOP"
|
|
|
+.PP
|
|
|
+To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
|
|
|
+configuration (no autoconf):
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& #define EV_STANDALONE 1
|
|
|
+\& #include "ev.c"
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+This will automatically include \fIev.h\fR, too, and should be done in a
|
|
|
+single C source file only to provide the function implementations. To use
|
|
|
+it, do the same for \fIev.h\fR in all files wishing to use this \s-1API \s0(best
|
|
|
+done by writing a wrapper around \fIev.h\fR that you can include instead and
|
|
|
+where you can put other configuration options):
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& #define EV_STANDALONE 1
|
|
|
+\& #include "ev.h"
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Both header files and implementation files can be compiled with a \*(C+
|
|
|
+compiler (at least, that's a stated goal, and breakage will be treated
|
|
|
+as a bug).
|
|
|
+.PP
|
|
|
+You need the following files in your source tree, or in a directory
|
|
|
+in your include path (e.g. in libev/ when using \-Ilibev):
|
|
|
+.PP
|
|
|
+.Vb 4
|
|
|
+\& ev.h
|
|
|
+\& ev.c
|
|
|
+\& ev_vars.h
|
|
|
+\& ev_wrap.h
|
|
|
+\&
|
|
|
+\& ev_win32.c required on win32 platforms only
|
|
|
+\&
|
|
|
+\& ev_select.c only when select backend is enabled
|
|
|
+\& ev_poll.c only when poll backend is enabled
|
|
|
+\& ev_epoll.c only when the epoll backend is enabled
|
|
|
+\& ev_kqueue.c only when the kqueue backend is enabled
|
|
|
+\& ev_port.c only when the solaris port backend is enabled
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+\&\fIev.c\fR includes the backend files directly when enabled, so you only need
|
|
|
+to compile this single file.
|
|
|
+.PP
|
|
|
+\fI\s-1LIBEVENT COMPATIBILITY API\s0\fR
|
|
|
+.IX Subsection "LIBEVENT COMPATIBILITY API"
|
|
|
+.PP
|
|
|
+To include the libevent compatibility \s-1API,\s0 also include:
|
|
|
+.PP
|
|
|
+.Vb 1
|
|
|
+\& #include "event.c"
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+in the file including \fIev.c\fR, and:
|
|
|
+.PP
|
|
|
+.Vb 1
|
|
|
+\& #include "event.h"
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+in the files that want to use the libevent \s-1API.\s0 This also includes \fIev.h\fR.
|
|
|
+.PP
|
|
|
+You need the following additional files for this:
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& event.h
|
|
|
+\& event.c
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+\fI\s-1AUTOCONF SUPPORT\s0\fR
|
|
|
+.IX Subsection "AUTOCONF SUPPORT"
|
|
|
+.PP
|
|
|
+Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your configuration in
|
|
|
+whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
|
|
|
+\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
|
|
|
+include \fIconfig.h\fR and configure itself accordingly.
|
|
|
+.PP
|
|
|
+For this of course you need the m4 file:
|
|
|
+.PP
|
|
|
+.Vb 1
|
|
|
+\& libev.m4
|
|
|
+.Ve
|
|
|
+.SS "\s-1PREPROCESSOR SYMBOLS/MACROS\s0"
|
|
|
+.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
|
|
|
+Libev can be configured via a variety of preprocessor symbols you have to
|
|
|
+define before including (or compiling) any of its files. The default in
|
|
|
+the absence of autoconf is documented for every option.
|
|
|
+.PP
|
|
|
+Symbols marked with \*(L"(h)\*(R" do not change the \s-1ABI,\s0 and can have different
|
|
|
+values when compiling libev vs. including \fIev.h\fR, so it is permissible
|
|
|
+to redefine them before including \fIev.h\fR without breaking compatibility
|
|
|
+to a compiled library. All other symbols change the \s-1ABI,\s0 which means all
|
|
|
+users of libev and the libev code itself must be compiled with compatible
|
|
|
+settings.
|
|
|
+.IP "\s-1EV_COMPAT3 \s0(h)" 4
|
|
|
+.IX Item "EV_COMPAT3 (h)"
|
|
|
+Backwards compatibility is a major concern for libev. This is why this
|
|
|
+release of libev comes with wrappers for the functions and symbols that
|
|
|
+have been renamed between libev version 3 and 4.
|
|
|
+.Sp
|
|
|
+You can disable these wrappers (to test compatibility with future
|
|
|
+versions) by defining \f(CW\*(C`EV_COMPAT3\*(C'\fR to \f(CW0\fR when compiling your
|
|
|
+sources. This has the additional advantage that you can drop the \f(CW\*(C`struct\*(C'\fR
|
|
|
+from \f(CW\*(C`struct ev_loop\*(C'\fR declarations, as libev will provide an \f(CW\*(C`ev_loop\*(C'\fR
|
|
|
+typedef in that case.
|
|
|
+.Sp
|
|
|
+In some future version, the default for \f(CW\*(C`EV_COMPAT3\*(C'\fR will become \f(CW0\fR,
|
|
|
+and in some even more future version the compatibility code will be
|
|
|
+removed completely.
|
|
|
+.IP "\s-1EV_STANDALONE \s0(h)" 4
|
|
|
+.IX Item "EV_STANDALONE (h)"
|
|
|
+Must always be \f(CW1\fR if you do not use autoconf configuration, which
|
|
|
+keeps libev from including \fIconfig.h\fR, and it also defines dummy
|
|
|
+implementations for some libevent functions (such as logging, which is not
|
|
|
+supported). It will also not define any of the structs usually found in
|
|
|
+\&\fIevent.h\fR that are not directly supported by the libev core alone.
|
|
|
+.Sp
|
|
|
+In standalone mode, libev will still try to automatically deduce the
|
|
|
+configuration, but has to be more conservative.
|
|
|
+.IP "\s-1EV_USE_FLOOR\s0" 4
|
|
|
+.IX Item "EV_USE_FLOOR"
|
|
|
+If defined to be \f(CW1\fR, libev will use the \f(CW\*(C`floor ()\*(C'\fR function for its
|
|
|
+periodic reschedule calculations, otherwise libev will fall back on a
|
|
|
+portable (slower) implementation. If you enable this, you usually have to
|
|
|
+link against libm or something equivalent. Enabling this when the \f(CW\*(C`floor\*(C'\fR
|
|
|
+function is not available will fail, so the safe default is to not enable
|
|
|
+this.
|
|
|
+.IP "\s-1EV_USE_MONOTONIC\s0" 4
|
|
|
+.IX Item "EV_USE_MONOTONIC"
|
|
|
+If defined to be \f(CW1\fR, libev will try to detect the availability of the
|
|
|
+monotonic clock option at both compile time and runtime. Otherwise no
|
|
|
+use of the monotonic clock option will be attempted. If you enable this,
|
|
|
+you usually have to link against librt or something similar. Enabling it
|
|
|
+when the functionality isn't available is safe, though, although you have
|
|
|
+to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
|
|
|
+function is hiding in (often \fI\-lrt\fR). See also \f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR.
|
|
|
+.IP "\s-1EV_USE_REALTIME\s0" 4
|
|
|
+.IX Item "EV_USE_REALTIME"
|
|
|
+If defined to be \f(CW1\fR, libev will try to detect the availability of the
|
|
|
+real-time clock option at compile time (and assume its availability
|
|
|
+at runtime if successful). Otherwise no use of the real-time clock
|
|
|
+option will be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR
|
|
|
+by \f(CW\*(C`clock_get (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect
|
|
|
+correctness. See the note about libraries in the description of
|
|
|
+\&\f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. Defaults to the opposite value of
|
|
|
+\&\f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR.
|
|
|
+.IP "\s-1EV_USE_CLOCK_SYSCALL\s0" 4
|
|
|
+.IX Item "EV_USE_CLOCK_SYSCALL"
|
|
|
+If defined to be \f(CW1\fR, libev will try to use a direct syscall instead
|
|
|
+of calling the system-provided \f(CW\*(C`clock_gettime\*(C'\fR function. This option
|
|
|
+exists because on GNU/Linux, \f(CW\*(C`clock_gettime\*(C'\fR is in \f(CW\*(C`librt\*(C'\fR, but \f(CW\*(C`librt\*(C'\fR
|
|
|
+unconditionally pulls in \f(CW\*(C`libpthread\*(C'\fR, slowing down single-threaded
|
|
|
+programs needlessly. Using a direct syscall is slightly slower (in
|
|
|
+theory), because no optimised vdso implementation can be used, but avoids
|
|
|
+the pthread dependency. Defaults to \f(CW1\fR on GNU/Linux with glibc 2.x or
|
|
|
+higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR).
|
|
|
+.IP "\s-1EV_USE_NANOSLEEP\s0" 4
|
|
|
+.IX Item "EV_USE_NANOSLEEP"
|
|
|
+If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
|
|
|
+and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
|
|
|
+.IP "\s-1EV_USE_EVENTFD\s0" 4
|
|
|
+.IX Item "EV_USE_EVENTFD"
|
|
|
+If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is
|
|
|
+available and will probe for kernel support at runtime. This will improve
|
|
|
+\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption.
|
|
|
+If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
|
|
|
+2.7 or newer, otherwise disabled.
|
|
|
+.IP "\s-1EV_USE_SELECT\s0" 4
|
|
|
+.IX Item "EV_USE_SELECT"
|
|
|
+If undefined or defined to be \f(CW1\fR, libev will compile in support for the
|
|
|
+\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at auto-detection will be done: if no
|
|
|
+other method takes over, select will be it. Otherwise the select backend
|
|
|
+will not be compiled in.
|
|
|
+.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
|
|
|
+.IX Item "EV_SELECT_USE_FD_SET"
|
|
|
+If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
|
|
|
+structure. This is useful if libev doesn't compile due to a missing
|
|
|
+\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout
|
|
|
+on exotic systems. This usually limits the range of file descriptors to
|
|
|
+some low limit such as 1024 or might have other limitations (winsocket
|
|
|
+only allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation,
|
|
|
+configures the maximum size of the \f(CW\*(C`fd_set\*(C'\fR.
|
|
|
+.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
|
|
|
+.IX Item "EV_SELECT_IS_WINSOCKET"
|
|
|
+When defined to \f(CW1\fR, the select backend will assume that
|
|
|
+select/socket/connect etc. don't understand file descriptors but
|
|
|
+wants osf handles on win32 (this is the case when the select to
|
|
|
+be used is the winsock select). This means that it will call
|
|
|
+\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
|
|
|
+it is assumed that all these functions actually work on fds, even
|
|
|
+on win32. Should not be defined on non\-win32 platforms.
|
|
|
+.IP "\s-1EV_FD_TO_WIN32_HANDLE\s0(fd)" 4
|
|
|
+.IX Item "EV_FD_TO_WIN32_HANDLE(fd)"
|
|
|
+If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map
|
|
|
+file descriptors to socket handles. When not defining this symbol (the
|
|
|
+default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually
|
|
|
+correct. In some cases, programs use their own file descriptor management,
|
|
|
+in which case they can provide this function to map fds to socket handles.
|
|
|
+.IP "\s-1EV_WIN32_HANDLE_TO_FD\s0(handle)" 4
|
|
|
+.IX Item "EV_WIN32_HANDLE_TO_FD(handle)"
|
|
|
+If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR then libev maps handles to file descriptors
|
|
|
+using the standard \f(CW\*(C`_open_osfhandle\*(C'\fR function. For programs implementing
|
|
|
+their own fd to handle mapping, overwriting this function makes it easier
|
|
|
+to do so. This can be done by defining this macro to an appropriate value.
|
|
|
+.IP "\s-1EV_WIN32_CLOSE_FD\s0(fd)" 4
|
|
|
+.IX Item "EV_WIN32_CLOSE_FD(fd)"
|
|
|
+If programs implement their own fd to handle mapping on win32, then this
|
|
|
+macro can be used to override the \f(CW\*(C`close\*(C'\fR function, useful to unregister
|
|
|
+file descriptors again. Note that the replacement function has to close
|
|
|
+the underlying \s-1OS\s0 handle.
|
|
|
+.IP "\s-1EV_USE_WSASOCKET\s0" 4
|
|
|
+.IX Item "EV_USE_WSASOCKET"
|
|
|
+If defined to be \f(CW1\fR, libev will use \f(CW\*(C`WSASocket\*(C'\fR to create its internal
|
|
|
+communication socket, which works better in some environments. Otherwise,
|
|
|
+the normal \f(CW\*(C`socket\*(C'\fR function will be used, which works better in other
|
|
|
+environments.
|
|
|
+.IP "\s-1EV_USE_POLL\s0" 4
|
|
|
+.IX Item "EV_USE_POLL"
|
|
|
+If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
|
|
|
+backend. Otherwise it will be enabled on non\-win32 platforms. It
|
|
|
+takes precedence over select.
|
|
|
+.IP "\s-1EV_USE_EPOLL\s0" 4
|
|
|
+.IX Item "EV_USE_EPOLL"
|
|
|
+If defined to be \f(CW1\fR, libev will compile in support for the Linux
|
|
|
+\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
|
|
|
+otherwise another method will be used as fallback. This is the preferred
|
|
|
+backend for GNU/Linux systems. If undefined, it will be enabled if the
|
|
|
+headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
|
|
|
+.IP "\s-1EV_USE_KQUEUE\s0" 4
|
|
|
+.IX Item "EV_USE_KQUEUE"
|
|
|
+If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
|
|
|
+\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
|
|
|
+otherwise another method will be used as fallback. This is the preferred
|
|
|
+backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
|
|
|
+supports some types of fds correctly (the only platform we found that
|
|
|
+supports ptys for example was NetBSD), so kqueue might be compiled in, but
|
|
|
+not be used unless explicitly requested. The best way to use it is to find
|
|
|
+out whether kqueue supports your type of fd properly and use an embedded
|
|
|
+kqueue loop.
|
|
|
+.IP "\s-1EV_USE_PORT\s0" 4
|
|
|
+.IX Item "EV_USE_PORT"
|
|
|
+If defined to be \f(CW1\fR, libev will compile in support for the Solaris
|
|
|
+10 port style backend. Its availability will be detected at runtime,
|
|
|
+otherwise another method will be used as fallback. This is the preferred
|
|
|
+backend for Solaris 10 systems.
|
|
|
+.IP "\s-1EV_USE_DEVPOLL\s0" 4
|
|
|
+.IX Item "EV_USE_DEVPOLL"
|
|
|
+Reserved for future expansion, works like the \s-1USE\s0 symbols above.
|
|
|
+.IP "\s-1EV_USE_INOTIFY\s0" 4
|
|
|
+.IX Item "EV_USE_INOTIFY"
|
|
|
+If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
|
|
|
+interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
|
|
|
+be detected at runtime. If undefined, it will be enabled if the headers
|
|
|
+indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
|
|
|
+.IP "\s-1EV_NO_SMP\s0" 4
|
|
|
+.IX Item "EV_NO_SMP"
|
|
|
+If defined to be \f(CW1\fR, libev will assume that memory is always coherent
|
|
|
+between threads, that is, threads can be used, but threads never run on
|
|
|
+different cpus (or different cpu cores). This reduces dependencies
|
|
|
+and makes libev faster.
|
|
|
+.IP "\s-1EV_NO_THREADS\s0" 4
|
|
|
+.IX Item "EV_NO_THREADS"
|
|
|
+If defined to be \f(CW1\fR, libev will assume that it will never be called from
|
|
|
+different threads (that includes signal handlers), which is a stronger
|
|
|
+assumption than \f(CW\*(C`EV_NO_SMP\*(C'\fR, above. This reduces dependencies and makes
|
|
|
+libev faster.
|
|
|
+.IP "\s-1EV_ATOMIC_T\s0" 4
|
|
|
+.IX Item "EV_ATOMIC_T"
|
|
|
+Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose
|
|
|
+access is atomic with respect to other threads or signal contexts. No
|
|
|
+such type is easily found in the C language, so you can provide your own
|
|
|
+type that you know is safe for your purposes. It is used both for signal
|
|
|
+handler \*(L"locking\*(R" as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR
|
|
|
+watchers.
|
|
|
+.Sp
|
|
|
+In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR
|
|
|
+(from \fIsignal.h\fR), which is usually good enough on most platforms.
|
|
|
+.IP "\s-1EV_H \s0(h)" 4
|
|
|
+.IX Item "EV_H (h)"
|
|
|
+The name of the \fIev.h\fR header file used to include it. The default if
|
|
|
+undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be
|
|
|
+used to virtually rename the \fIev.h\fR header file in case of conflicts.
|
|
|
+.IP "\s-1EV_CONFIG_H \s0(h)" 4
|
|
|
+.IX Item "EV_CONFIG_H (h)"
|
|
|
+If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
|
|
|
+\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
|
|
|
+\&\f(CW\*(C`EV_H\*(C'\fR, above.
|
|
|
+.IP "\s-1EV_EVENT_H \s0(h)" 4
|
|
|
+.IX Item "EV_EVENT_H (h)"
|
|
|
+Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
|
|
|
+of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR.
|
|
|
+.IP "\s-1EV_PROTOTYPES \s0(h)" 4
|
|
|
+.IX Item "EV_PROTOTYPES (h)"
|
|
|
+If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
|
|
|
+prototypes, but still define all the structs and other symbols. This is
|
|
|
+occasionally useful if you want to provide your own wrapper functions
|
|
|
+around libev functions.
|
|
|
+.IP "\s-1EV_MULTIPLICITY\s0" 4
|
|
|
+.IX Item "EV_MULTIPLICITY"
|
|
|
+If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
|
|
|
+will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
|
|
|
+additional independent event loops. Otherwise there will be no support
|
|
|
+for multiple event loops and there is no first event loop pointer
|
|
|
+argument. Instead, all functions act on the single default loop.
|
|
|
+.Sp
|
|
|
+Note that \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR will no longer provide a
|
|
|
+default loop when multiplicity is switched off \- you always have to
|
|
|
+initialise the loop manually in this case.
|
|
|
+.IP "\s-1EV_MINPRI\s0" 4
|
|
|
+.IX Item "EV_MINPRI"
|
|
|
+.PD 0
|
|
|
+.IP "\s-1EV_MAXPRI\s0" 4
|
|
|
+.IX Item "EV_MAXPRI"
|
|
|
+.PD
|
|
|
+The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
|
|
|
+\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
|
|
|
+provide for more priorities by overriding those symbols (usually defined
|
|
|
+to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
|
|
|
+.Sp
|
|
|
+When doing priority-based operations, libev usually has to linearly search
|
|
|
+all the priorities, so having many of them (hundreds) uses a lot of space
|
|
|
+and time, so using the defaults of five priorities (\-2 .. +2) is usually
|
|
|
+fine.
|
|
|
+.Sp
|
|
|
+If your embedding application does not need any priorities, defining these
|
|
|
+both to \f(CW0\fR will save some memory and \s-1CPU.\s0
|
|
|
+.IP "\s-1EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, EV_ASYNC_ENABLE, EV_CHILD_ENABLE.\s0" 4
|
|
|
+.IX Item "EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, EV_ASYNC_ENABLE, EV_CHILD_ENABLE."
|
|
|
+If undefined or defined to be \f(CW1\fR (and the platform supports it), then
|
|
|
+the respective watcher type is supported. If defined to be \f(CW0\fR, then it
|
|
|
+is not. Disabling watcher types mainly saves code size.
|
|
|
+.IP "\s-1EV_FEATURES\s0" 4
|
|
|
+.IX Item "EV_FEATURES"
|
|
|
+If you need to shave off some kilobytes of code at the expense of some
|
|
|
+speed (but with the full \s-1API\s0), you can define this symbol to request
|
|
|
+certain subsets of functionality. The default is to enable all features
|
|
|
+that can be enabled on the platform.
|
|
|
+.Sp
|
|
|
+A typical way to use this symbol is to define it to \f(CW0\fR (or to a bitset
|
|
|
+with some broad features you want) and then selectively re-enable
|
|
|
+additional parts you want, for example if you want everything minimal,
|
|
|
+but multiple event loop support, async and child watchers and the poll
|
|
|
+backend, use this:
|
|
|
+.Sp
|
|
|
+.Vb 5
|
|
|
+\& #define EV_FEATURES 0
|
|
|
+\& #define EV_MULTIPLICITY 1
|
|
|
+\& #define EV_USE_POLL 1
|
|
|
+\& #define EV_CHILD_ENABLE 1
|
|
|
+\& #define EV_ASYNC_ENABLE 1
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+The actual value is a bitset, it can be a combination of the following
|
|
|
+values (by default, all of these are enabled):
|
|
|
+.RS 4
|
|
|
+.ie n .IP "1 \- faster/larger code" 4
|
|
|
+.el .IP "\f(CW1\fR \- faster/larger code" 4
|
|
|
+.IX Item "1 - faster/larger code"
|
|
|
+Use larger code to speed up some operations.
|
|
|
+.Sp
|
|
|
+Currently this is used to override some inlining decisions (enlarging the
|
|
|
+code size by roughly 30% on amd64).
|
|
|
+.Sp
|
|
|
+When optimising for size, use of compiler flags such as \f(CW\*(C`\-Os\*(C'\fR with
|
|
|
+gcc is recommended, as well as \f(CW\*(C`\-DNDEBUG\*(C'\fR, as libev contains a number of
|
|
|
+assertions.
|
|
|
+.Sp
|
|
|
+The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler
|
|
|
+(e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR).
|
|
|
+.ie n .IP "2 \- faster/larger data structures" 4
|
|
|
+.el .IP "\f(CW2\fR \- faster/larger data structures" 4
|
|
|
+.IX Item "2 - faster/larger data structures"
|
|
|
+Replaces the small 2\-heap for timer management by a faster 4\-heap, larger
|
|
|
+hash table sizes and so on. This will usually further increase code size
|
|
|
+and can additionally have an effect on the size of data structures at
|
|
|
+runtime.
|
|
|
+.Sp
|
|
|
+The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler
|
|
|
+(e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR).
|
|
|
+.ie n .IP "4 \- full \s-1API\s0 configuration" 4
|
|
|
+.el .IP "\f(CW4\fR \- full \s-1API\s0 configuration" 4
|
|
|
+.IX Item "4 - full API configuration"
|
|
|
+This enables priorities (sets \f(CW\*(C`EV_MAXPRI\*(C'\fR=2 and \f(CW\*(C`EV_MINPRI\*(C'\fR=\-2), and
|
|
|
+enables multiplicity (\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR=1).
|
|
|
+.ie n .IP "8 \- full \s-1API\s0" 4
|
|
|
+.el .IP "\f(CW8\fR \- full \s-1API\s0" 4
|
|
|
+.IX Item "8 - full API"
|
|
|
+This enables a lot of the \*(L"lesser used\*(R" \s-1API\s0 functions. See \f(CW\*(C`ev.h\*(C'\fR for
|
|
|
+details on which parts of the \s-1API\s0 are still available without this
|
|
|
+feature, and do not complain if this subset changes over time.
|
|
|
+.ie n .IP "16 \- enable all optional watcher types" 4
|
|
|
+.el .IP "\f(CW16\fR \- enable all optional watcher types" 4
|
|
|
+.IX Item "16 - enable all optional watcher types"
|
|
|
+Enables all optional watcher types. If you want to selectively enable
|
|
|
+only some watcher types other than I/O and timers (e.g. prepare,
|
|
|
+embed, async, child...) you can enable them manually by defining
|
|
|
+\&\f(CW\*(C`EV_watchertype_ENABLE\*(C'\fR to \f(CW1\fR instead.
|
|
|
+.ie n .IP "32 \- enable all backends" 4
|
|
|
+.el .IP "\f(CW32\fR \- enable all backends" 4
|
|
|
+.IX Item "32 - enable all backends"
|
|
|
+This enables all backends \- without this feature, you need to enable at
|
|
|
+least one backend manually (\f(CW\*(C`EV_USE_SELECT\*(C'\fR is a good choice).
|
|
|
+.ie n .IP "64 \- enable OS-specific ""helper"" APIs" 4
|
|
|
+.el .IP "\f(CW64\fR \- enable OS-specific ``helper'' APIs" 4
|
|
|
+.IX Item "64 - enable OS-specific helper APIs"
|
|
|
+Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
|
|
|
+default.
|
|
|
+.RE
|
|
|
+.RS 4
|
|
|
+.Sp
|
|
|
+Compiling with \f(CW\*(C`gcc \-Os \-DEV_STANDALONE \-DEV_USE_EPOLL=1 \-DEV_FEATURES=0\*(C'\fR
|
|
|
+reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
|
|
|
+code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
|
|
|
+watchers, timers and monotonic clock support.
|
|
|
+.Sp
|
|
|
+With an intelligent-enough linker (gcc+binutils are intelligent enough
|
|
|
+when you use \f(CW\*(C`\-Wl,\-\-gc\-sections \-ffunction\-sections\*(C'\fR) functions unused by
|
|
|
+your program might be left out as well \- a binary starting a timer and an
|
|
|
+I/O watcher then might come out at only 5Kb.
|
|
|
+.RE
|
|
|
+.IP "\s-1EV_API_STATIC\s0" 4
|
|
|
+.IX Item "EV_API_STATIC"
|
|
|
+If this symbol is defined (by default it is not), then all identifiers
|
|
|
+will have static linkage. This means that libev will not export any
|
|
|
+identifiers, and you cannot link against libev anymore. This can be useful
|
|
|
+when you embed libev, only want to use libev functions in a single file,
|
|
|
+and do not want its identifiers to be visible.
|
|
|
+.Sp
|
|
|
+To use this, define \f(CW\*(C`EV_API_STATIC\*(C'\fR and include \fIev.c\fR in the file that
|
|
|
+wants to use libev.
|
|
|
+.Sp
|
|
|
+This option only works when libev is compiled with a C compiler, as \*(C+
|
|
|
+doesn't support the required declaration syntax.
|
|
|
+.IP "\s-1EV_AVOID_STDIO\s0" 4
|
|
|
+.IX Item "EV_AVOID_STDIO"
|
|
|
+If this is set to \f(CW1\fR at compiletime, then libev will avoid using stdio
|
|
|
+functions (printf, scanf, perror etc.). This will increase the code size
|
|
|
+somewhat, but if your program doesn't otherwise depend on stdio and your
|
|
|
+libc allows it, this avoids linking in the stdio library which is quite
|
|
|
+big.
|
|
|
+.Sp
|
|
|
+Note that error messages might become less precise when this option is
|
|
|
+enabled.
|
|
|
+.IP "\s-1EV_NSIG\s0" 4
|
|
|
+.IX Item "EV_NSIG"
|
|
|
+The highest supported signal number, +1 (or, the number of
|
|
|
+signals): Normally, libev tries to deduce the maximum number of signals
|
|
|
+automatically, but sometimes this fails, in which case it can be
|
|
|
+specified. Also, using a lower number than detected (\f(CW32\fR should be
|
|
|
+good for about any system in existence) can save some memory, as libev
|
|
|
+statically allocates some 12\-24 bytes per signal number.
|
|
|
+.IP "\s-1EV_PID_HASHSIZE\s0" 4
|
|
|
+.IX Item "EV_PID_HASHSIZE"
|
|
|
+\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
|
|
|
+pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR disabled),
|
|
|
+usually more than enough. If you need to manage thousands of children you
|
|
|
+might want to increase this value (\fImust\fR be a power of two).
|
|
|
+.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
|
|
|
+.IX Item "EV_INOTIFY_HASHSIZE"
|
|
|
+\&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by
|
|
|
+inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR
|
|
|
+disabled), usually more than enough. If you need to manage thousands of
|
|
|
+\&\f(CW\*(C`ev_stat\*(C'\fR watchers you might want to increase this value (\fImust\fR be a
|
|
|
+power of two).
|
|
|
+.IP "\s-1EV_USE_4HEAP\s0" 4
|
|
|
+.IX Item "EV_USE_4HEAP"
|
|
|
+Heaps are not very cache-efficient. To improve the cache-efficiency of the
|
|
|
+timer and periodics heaps, libev uses a 4\-heap when this symbol is defined
|
|
|
+to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has noticeably
|
|
|
+faster performance with many (thousands) of watchers.
|
|
|
+.Sp
|
|
|
+The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
|
|
|
+will be \f(CW0\fR.
|
|
|
+.IP "\s-1EV_HEAP_CACHE_AT\s0" 4
|
|
|
+.IX Item "EV_HEAP_CACHE_AT"
|
|
|
+Heaps are not very cache-efficient. To improve the cache-efficiency of the
|
|
|
+timer and periodics heaps, libev can cache the timestamp (\fIat\fR) within
|
|
|
+the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR),
|
|
|
+which uses 8\-12 bytes more per watcher and a few hundred bytes more code,
|
|
|
+but avoids random read accesses on heap changes. This improves performance
|
|
|
+noticeably with many (hundreds) of watchers.
|
|
|
+.Sp
|
|
|
+The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
|
|
|
+will be \f(CW0\fR.
|
|
|
+.IP "\s-1EV_VERIFY\s0" 4
|
|
|
+.IX Item "EV_VERIFY"
|
|
|
+Controls how much internal verification (see \f(CW\*(C`ev_verify ()\*(C'\fR) will
|
|
|
+be done: If set to \f(CW0\fR, no internal verification code will be compiled
|
|
|
+in. If set to \f(CW1\fR, then verification code will be compiled in, but not
|
|
|
+called. If set to \f(CW2\fR, then the internal verification code will be
|
|
|
+called once per loop, which can slow down libev. If set to \f(CW3\fR, then the
|
|
|
+verification code will be called very frequently, which will slow down
|
|
|
+libev considerably.
|
|
|
+.Sp
|
|
|
+The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
|
|
|
+will be \f(CW0\fR.
|
|
|
+.IP "\s-1EV_COMMON\s0" 4
|
|
|
+.IX Item "EV_COMMON"
|
|
|
+By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
|
|
|
+this macro to something else you can include more and other types of
|
|
|
+members. You have to define it each time you include one of the files,
|
|
|
+though, and it must be identical each time.
|
|
|
+.Sp
|
|
|
+For example, the perl \s-1EV\s0 module uses something like this:
|
|
|
+.Sp
|
|
|
+.Vb 3
|
|
|
+\& #define EV_COMMON \e
|
|
|
+\& SV *self; /* contains this struct */ \e
|
|
|
+\& SV *cb_sv, *fh /* note no trailing ";" */
|
|
|
+.Ve
|
|
|
+.IP "\s-1EV_CB_DECLARE \s0(type)" 4
|
|
|
+.IX Item "EV_CB_DECLARE (type)"
|
|
|
+.PD 0
|
|
|
+.IP "\s-1EV_CB_INVOKE \s0(watcher, revents)" 4
|
|
|
+.IX Item "EV_CB_INVOKE (watcher, revents)"
|
|
|
+.IP "ev_set_cb (ev, cb)" 4
|
|
|
+.IX Item "ev_set_cb (ev, cb)"
|
|
|
+.PD
|
|
|
+Can be used to change the callback member declaration in each watcher,
|
|
|
+and the way callbacks are invoked and set. Must expand to a struct member
|
|
|
+definition and a statement, respectively. See the \fIev.h\fR header file for
|
|
|
+their default definitions. One possible use for overriding these is to
|
|
|
+avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
|
|
|
+method calls instead of plain function calls in \*(C+.
|
|
|
+.SS "\s-1EXPORTED API SYMBOLS\s0"
|
|
|
+.IX Subsection "EXPORTED API SYMBOLS"
|
|
|
+If you need to re-export the \s-1API \s0(e.g. via a \s-1DLL\s0) and you need a list of
|
|
|
+exported symbols, you can use the provided \fISymbol.*\fR files which list
|
|
|
+all public symbols, one per line:
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& Symbols.ev for libev proper
|
|
|
+\& Symbols.event for the libevent emulation
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+This can also be used to rename all public symbols to avoid clashes with
|
|
|
+multiple versions of libev linked together (which is obviously bad in
|
|
|
+itself, but sometimes it is inconvenient to avoid this).
|
|
|
+.PP
|
|
|
+A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to
|
|
|
+include before including \fIev.h\fR:
|
|
|
+.PP
|
|
|
+.Vb 1
|
|
|
+\& <Symbols.ev sed \-e "s/.*/#define & myprefix_&/" >wrap.h
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+This would create a file \fIwrap.h\fR which essentially looks like this:
|
|
|
+.PP
|
|
|
+.Vb 4
|
|
|
+\& #define ev_backend myprefix_ev_backend
|
|
|
+\& #define ev_check_start myprefix_ev_check_start
|
|
|
+\& #define ev_check_stop myprefix_ev_check_stop
|
|
|
+\& ...
|
|
|
+.Ve
|
|
|
+.SS "\s-1EXAMPLES\s0"
|
|
|
+.IX Subsection "EXAMPLES"
|
|
|
+For a real-world example of a program the includes libev
|
|
|
+verbatim, you can have a look at the \s-1EV\s0 perl module
|
|
|
+(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
|
|
|
+the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
|
|
|
+interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
|
|
|
+will be compiled. It is pretty complex because it provides its own header
|
|
|
+file.
|
|
|
+.PP
|
|
|
+The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
|
|
|
+that everybody includes and which overrides some configure choices:
|
|
|
+.PP
|
|
|
+.Vb 8
|
|
|
+\& #define EV_FEATURES 8
|
|
|
+\& #define EV_USE_SELECT 1
|
|
|
+\& #define EV_PREPARE_ENABLE 1
|
|
|
+\& #define EV_IDLE_ENABLE 1
|
|
|
+\& #define EV_SIGNAL_ENABLE 1
|
|
|
+\& #define EV_CHILD_ENABLE 1
|
|
|
+\& #define EV_USE_STDEXCEPT 0
|
|
|
+\& #define EV_CONFIG_H <config.h>
|
|
|
+\&
|
|
|
+\& #include "ev++.h"
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& #include "ev_cpp.h"
|
|
|
+\& #include "ev.c"
|
|
|
+.Ve
|
|
|
+.SH "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT"
|
|
|
+.IX Header "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT"
|
|
|
+.SS "\s-1THREADS AND COROUTINES\s0"
|
|
|
+.IX Subsection "THREADS AND COROUTINES"
|
|
|
+\fI\s-1THREADS\s0\fR
|
|
|
+.IX Subsection "THREADS"
|
|
|
+.PP
|
|
|
+All libev functions are reentrant and thread-safe unless explicitly
|
|
|
+documented otherwise, but libev implements no locking itself. This means
|
|
|
+that you can use as many loops as you want in parallel, as long as there
|
|
|
+are no concurrent calls into any libev function with the same loop
|
|
|
+parameter (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter,
|
|
|
+of course): libev guarantees that different event loops share no data
|
|
|
+structures that need any locking.
|
|
|
+.PP
|
|
|
+Or to put it differently: calls with different loop parameters can be done
|
|
|
+concurrently from multiple threads, calls with the same loop parameter
|
|
|
+must be done serially (but can be done from different threads, as long as
|
|
|
+only one thread ever is inside a call at any point in time, e.g. by using
|
|
|
+a mutex per loop).
|
|
|
+.PP
|
|
|
+Specifically to support threads (and signal handlers), libev implements
|
|
|
+so-called \f(CW\*(C`ev_async\*(C'\fR watchers, which allow some limited form of
|
|
|
+concurrency on the same event loop, namely waking it up \*(L"from the
|
|
|
+outside\*(R".
|
|
|
+.PP
|
|
|
+If you want to know which design (one loop, locking, or multiple loops
|
|
|
+without or something else still) is best for your problem, then I cannot
|
|
|
+help you, but here is some generic advice:
|
|
|
+.IP "\(bu" 4
|
|
|
+most applications have a main thread: use the default libev loop
|
|
|
+in that thread, or create a separate thread running only the default loop.
|
|
|
+.Sp
|
|
|
+This helps integrating other libraries or software modules that use libev
|
|
|
+themselves and don't care/know about threading.
|
|
|
+.IP "\(bu" 4
|
|
|
+one loop per thread is usually a good model.
|
|
|
+.Sp
|
|
|
+Doing this is almost never wrong, sometimes a better-performance model
|
|
|
+exists, but it is always a good start.
|
|
|
+.IP "\(bu" 4
|
|
|
+other models exist, such as the leader/follower pattern, where one
|
|
|
+loop is handed through multiple threads in a kind of round-robin fashion.
|
|
|
+.Sp
|
|
|
+Choosing a model is hard \- look around, learn, know that usually you can do
|
|
|
+better than you currently do :\-)
|
|
|
+.IP "\(bu" 4
|
|
|
+often you need to talk to some other thread which blocks in the
|
|
|
+event loop.
|
|
|
+.Sp
|
|
|
+\&\f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other threads safely
|
|
|
+(or from signal contexts...).
|
|
|
+.Sp
|
|
|
+An example use would be to communicate signals or other events that only
|
|
|
+work in the default loop by registering the signal watcher with the
|
|
|
+default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop
|
|
|
+watcher callback into the event loop interested in the signal.
|
|
|
+.PP
|
|
|
+See also \*(L"\s-1THREAD LOCKING EXAMPLE\*(R"\s0.
|
|
|
+.PP
|
|
|
+\fI\s-1COROUTINES\s0\fR
|
|
|
+.IX Subsection "COROUTINES"
|
|
|
+.PP
|
|
|
+Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"):
|
|
|
+libev fully supports nesting calls to its functions from different
|
|
|
+coroutines (e.g. you can call \f(CW\*(C`ev_run\*(C'\fR on the same loop from two
|
|
|
+different coroutines, and switch freely between both coroutines running
|
|
|
+the loop, as long as you don't confuse yourself). The only exception is
|
|
|
+that you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks.
|
|
|
+.PP
|
|
|
+Care has been taken to ensure that libev does not keep local state inside
|
|
|
+\&\f(CW\*(C`ev_run\*(C'\fR, and other calls do not usually allow for coroutine switches as
|
|
|
+they do not call any callbacks.
|
|
|
+.SS "\s-1COMPILER WARNINGS\s0"
|
|
|
+.IX Subsection "COMPILER WARNINGS"
|
|
|
+Depending on your compiler and compiler settings, you might get no or a
|
|
|
+lot of warnings when compiling libev code. Some people are apparently
|
|
|
+scared by this.
|
|
|
+.PP
|
|
|
+However, these are unavoidable for many reasons. For one, each compiler
|
|
|
+has different warnings, and each user has different tastes regarding
|
|
|
+warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when
|
|
|
+targeting a specific compiler and compiler-version.
|
|
|
+.PP
|
|
|
+Another reason is that some compiler warnings require elaborate
|
|
|
+workarounds, or other changes to the code that make it less clear and less
|
|
|
+maintainable.
|
|
|
+.PP
|
|
|
+And of course, some compiler warnings are just plain stupid, or simply
|
|
|
+wrong (because they don't actually warn about the condition their message
|
|
|
+seems to warn about). For example, certain older gcc versions had some
|
|
|
+warnings that resulted in an extreme number of false positives. These have
|
|
|
+been fixed, but some people still insist on making code warn-free with
|
|
|
+such buggy versions.
|
|
|
+.PP
|
|
|
+While libev is written to generate as few warnings as possible,
|
|
|
+\&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev
|
|
|
+with any compiler warnings enabled unless you are prepared to cope with
|
|
|
+them (e.g. by ignoring them). Remember that warnings are just that:
|
|
|
+warnings, not errors, or proof of bugs.
|
|
|
+.SS "\s-1VALGRIND\s0"
|
|
|
+.IX Subsection "VALGRIND"
|
|
|
+Valgrind has a special section here because it is a popular tool that is
|
|
|
+highly useful. Unfortunately, valgrind reports are very hard to interpret.
|
|
|
+.PP
|
|
|
+If you think you found a bug (memory leak, uninitialised data access etc.)
|
|
|
+in libev, then check twice: If valgrind reports something like:
|
|
|
+.PP
|
|
|
+.Vb 3
|
|
|
+\& ==2274== definitely lost: 0 bytes in 0 blocks.
|
|
|
+\& ==2274== possibly lost: 0 bytes in 0 blocks.
|
|
|
+\& ==2274== still reachable: 256 bytes in 1 blocks.
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Then there is no memory leak, just as memory accounted to global variables
|
|
|
+is not a memleak \- the memory is still being referenced, and didn't leak.
|
|
|
+.PP
|
|
|
+Similarly, under some circumstances, valgrind might report kernel bugs
|
|
|
+as if it were a bug in libev (e.g. in realloc or in the poll backend,
|
|
|
+although an acceptable workaround has been found here), or it might be
|
|
|
+confused.
|
|
|
+.PP
|
|
|
+Keep in mind that valgrind is a very good tool, but only a tool. Don't
|
|
|
+make it into some kind of religion.
|
|
|
+.PP
|
|
|
+If you are unsure about something, feel free to contact the mailing list
|
|
|
+with the full valgrind report and an explanation on why you think this
|
|
|
+is a bug in libev (best check the archives, too :). However, don't be
|
|
|
+annoyed when you get a brisk \*(L"this is no bug\*(R" answer and take the chance
|
|
|
+of learning how to interpret valgrind properly.
|
|
|
+.PP
|
|
|
+If you need, for some reason, empty reports from valgrind for your project
|
|
|
+I suggest using suppression lists.
|
|
|
+.SH "PORTABILITY NOTES"
|
|
|
+.IX Header "PORTABILITY NOTES"
|
|
|
+.SS "\s-1GNU/LINUX 32 BIT LIMITATIONS\s0"
|
|
|
+.IX Subsection "GNU/LINUX 32 BIT LIMITATIONS"
|
|
|
+GNU/Linux is the only common platform that supports 64 bit file/large file
|
|
|
+interfaces but \fIdisables\fR them by default.
|
|
|
+.PP
|
|
|
+That means that libev compiled in the default environment doesn't support
|
|
|
+files larger than 2GiB or so, which mainly affects \f(CW\*(C`ev_stat\*(C'\fR watchers.
|
|
|
+.PP
|
|
|
+Unfortunately, many programs try to work around this GNU/Linux issue
|
|
|
+by enabling the large file \s-1API,\s0 which makes them incompatible with the
|
|
|
+standard libev compiled for their system.
|
|
|
+.PP
|
|
|
+Likewise, libev cannot enable the large file \s-1API\s0 itself as this would
|
|
|
+suddenly make it incompatible to the default compile time environment,
|
|
|
+i.e. all programs not using special compile switches.
|
|
|
+.SS "\s-1OS/X AND DARWIN BUGS\s0"
|
|
|
+.IX Subsection "OS/X AND DARWIN BUGS"
|
|
|
+The whole thing is a bug if you ask me \- basically any system interface
|
|
|
+you touch is broken, whether it is locales, poll, kqueue or even the
|
|
|
+OpenGL drivers.
|
|
|
+.PP
|
|
|
+\fI\f(CI\*(C`kqueue\*(C'\fI is buggy\fR
|
|
|
+.IX Subsection "kqueue is buggy"
|
|
|
+.PP
|
|
|
+The kqueue syscall is broken in all known versions \- most versions support
|
|
|
+only sockets, many support pipes.
|
|
|
+.PP
|
|
|
+Libev tries to work around this by not using \f(CW\*(C`kqueue\*(C'\fR by default on this
|
|
|
+rotten platform, but of course you can still ask for it when creating a
|
|
|
+loop \- embedding a socket-only kqueue loop into a select-based one is
|
|
|
+probably going to work well.
|
|
|
+.PP
|
|
|
+\fI\f(CI\*(C`poll\*(C'\fI is buggy\fR
|
|
|
+.IX Subsection "poll is buggy"
|
|
|
+.PP
|
|
|
+Instead of fixing \f(CW\*(C`kqueue\*(C'\fR, Apple replaced their (working) \f(CW\*(C`poll\*(C'\fR
|
|
|
+implementation by something calling \f(CW\*(C`kqueue\*(C'\fR internally around the 10.5.6
|
|
|
+release, so now \f(CW\*(C`kqueue\*(C'\fR \fIand\fR \f(CW\*(C`poll\*(C'\fR are broken.
|
|
|
+.PP
|
|
|
+Libev tries to work around this by not using \f(CW\*(C`poll\*(C'\fR by default on
|
|
|
+this rotten platform, but of course you can still ask for it when creating
|
|
|
+a loop.
|
|
|
+.PP
|
|
|
+\fI\f(CI\*(C`select\*(C'\fI is buggy\fR
|
|
|
+.IX Subsection "select is buggy"
|
|
|
+.PP
|
|
|
+All that's left is \f(CW\*(C`select\*(C'\fR, and of course Apple found a way to fuck this
|
|
|
+one up as well: On \s-1OS/X, \s0\f(CW\*(C`select\*(C'\fR actively limits the number of file
|
|
|
+descriptors you can pass in to 1024 \- your program suddenly crashes when
|
|
|
+you use more.
|
|
|
+.PP
|
|
|
+There is an undocumented \*(L"workaround\*(R" for this \- defining
|
|
|
+\&\f(CW\*(C`_DARWIN_UNLIMITED_SELECT\*(C'\fR, which libev tries to use, so select \fIshould\fR
|
|
|
+work on \s-1OS/X.\s0
|
|
|
+.SS "\s-1SOLARIS PROBLEMS AND WORKAROUNDS\s0"
|
|
|
+.IX Subsection "SOLARIS PROBLEMS AND WORKAROUNDS"
|
|
|
+\fI\f(CI\*(C`errno\*(C'\fI reentrancy\fR
|
|
|
+.IX Subsection "errno reentrancy"
|
|
|
+.PP
|
|
|
+The default compile environment on Solaris is unfortunately so
|
|
|
+thread-unsafe that you can't even use components/libraries compiled
|
|
|
+without \f(CW\*(C`\-D_REENTRANT\*(C'\fR in a threaded program, which, of course, isn't
|
|
|
+defined by default. A valid, if stupid, implementation choice.
|
|
|
+.PP
|
|
|
+If you want to use libev in threaded environments you have to make sure
|
|
|
+it's compiled with \f(CW\*(C`_REENTRANT\*(C'\fR defined.
|
|
|
+.PP
|
|
|
+\fIEvent port backend\fR
|
|
|
+.IX Subsection "Event port backend"
|
|
|
+.PP
|
|
|
+The scalable event interface for Solaris is called \*(L"event
|
|
|
+ports\*(R". Unfortunately, this mechanism is very buggy in all major
|
|
|
+releases. If you run into high \s-1CPU\s0 usage, your program freezes or you get
|
|
|
+a large number of spurious wakeups, make sure you have all the relevant
|
|
|
+and latest kernel patches applied. No, I don't know which ones, but there
|
|
|
+are multiple ones to apply, and afterwards, event ports actually work
|
|
|
+great.
|
|
|
+.PP
|
|
|
+If you can't get it to work, you can try running the program by setting
|
|
|
+the environment variable \f(CW\*(C`LIBEV_FLAGS=3\*(C'\fR to only allow \f(CW\*(C`poll\*(C'\fR and
|
|
|
+\&\f(CW\*(C`select\*(C'\fR backends.
|
|
|
+.SS "\s-1AIX POLL BUG\s0"
|
|
|
+.IX Subsection "AIX POLL BUG"
|
|
|
+\&\s-1AIX\s0 unfortunately has a broken \f(CW\*(C`poll.h\*(C'\fR header. Libev works around
|
|
|
+this by trying to avoid the poll backend altogether (i.e. it's not even
|
|
|
+compiled in), which normally isn't a big problem as \f(CW\*(C`select\*(C'\fR works fine
|
|
|
+with large bitsets on \s-1AIX,\s0 and \s-1AIX\s0 is dead anyway.
|
|
|
+.SS "\s-1WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS\s0"
|
|
|
+.IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS"
|
|
|
+\fIGeneral issues\fR
|
|
|
+.IX Subsection "General issues"
|
|
|
+.PP
|
|
|
+Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev
|
|
|
+requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0
|
|
|
+model. Libev still offers limited functionality on this platform in
|
|
|
+the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket
|
|
|
+descriptors. This only applies when using Win32 natively, not when using
|
|
|
+e.g. cygwin. Actually, it only applies to the microsofts own compilers,
|
|
|
+as every compiler comes with a slightly differently broken/incompatible
|
|
|
+environment.
|
|
|
+.PP
|
|
|
+Lifting these limitations would basically require the full
|
|
|
+re-implementation of the I/O system. If you are into this kind of thing,
|
|
|
+then note that glib does exactly that for you in a very portable way (note
|
|
|
+also that glib is the slowest event library known to man).
|
|
|
+.PP
|
|
|
+There is no supported compilation method available on windows except
|
|
|
+embedding it into other applications.
|
|
|
+.PP
|
|
|
+Sensible signal handling is officially unsupported by Microsoft \- libev
|
|
|
+tries its best, but under most conditions, signals will simply not work.
|
|
|
+.PP
|
|
|
+Not a libev limitation but worth mentioning: windows apparently doesn't
|
|
|
+accept large writes: instead of resulting in a partial write, windows will
|
|
|
+either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large,
|
|
|
+so make sure you only write small amounts into your sockets (less than a
|
|
|
+megabyte seems safe, but this apparently depends on the amount of memory
|
|
|
+available).
|
|
|
+.PP
|
|
|
+Due to the many, low, and arbitrary limits on the win32 platform and
|
|
|
+the abysmal performance of winsockets, using a large number of sockets
|
|
|
+is not recommended (and not reasonable). If your program needs to use
|
|
|
+more than a hundred or so sockets, then likely it needs to use a totally
|
|
|
+different implementation for windows, as libev offers the \s-1POSIX\s0 readiness
|
|
|
+notification model, which cannot be implemented efficiently on windows
|
|
|
+(due to Microsoft monopoly games).
|
|
|
+.PP
|
|
|
+A typical way to use libev under windows is to embed it (see the embedding
|
|
|
+section for details) and use the following \fIevwrap.h\fR header file instead
|
|
|
+of \fIev.h\fR:
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& #define EV_STANDALONE /* keeps ev from requiring config.h */
|
|
|
+\& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
|
|
|
+\&
|
|
|
+\& #include "ev.h"
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+And compile the following \fIevwrap.c\fR file into your project (make sure
|
|
|
+you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!):
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& #include "evwrap.h"
|
|
|
+\& #include "ev.c"
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+\fIThe winsocket \f(CI\*(C`select\*(C'\fI function\fR
|
|
|
+.IX Subsection "The winsocket select function"
|
|
|
+.PP
|
|
|
+The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it
|
|
|
+requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is
|
|
|
+also extremely buggy). This makes select very inefficient, and also
|
|
|
+requires a mapping from file descriptors to socket handles (the Microsoft
|
|
|
+C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the
|
|
|
+discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and
|
|
|
+\&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info.
|
|
|
+.PP
|
|
|
+The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime
|
|
|
+libraries and raw winsocket select is:
|
|
|
+.PP
|
|
|
+.Vb 2
|
|
|
+\& #define EV_USE_SELECT 1
|
|
|
+\& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
|
|
|
+.Ve
|
|
|
+.PP
|
|
|
+Note that winsockets handling of fd sets is O(n), so you can easily get a
|
|
|
+complexity in the O(nX) range when using win32.
|
|
|
+.PP
|
|
|
+\fILimited number of file descriptors\fR
|
|
|
+.IX Subsection "Limited number of file descriptors"
|
|
|
+.PP
|
|
|
+Windows has numerous arbitrary (and low) limits on things.
|
|
|
+.PP
|
|
|
+Early versions of winsocket's select only supported waiting for a maximum
|
|
|
+of \f(CW64\fR handles (probably owning to the fact that all windows kernels
|
|
|
+can only wait for \f(CW64\fR things at the same time internally; Microsoft
|
|
|
+recommends spawning a chain of threads and wait for 63 handles and the
|
|
|
+previous thread in each. Sounds great!).
|
|
|
+.PP
|
|
|
+Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR
|
|
|
+to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select
|
|
|
+call (which might be in libev or elsewhere, for example, perl and many
|
|
|
+other interpreters do their own select emulation on windows).
|
|
|
+.PP
|
|
|
+Another limit is the number of file descriptors in the Microsoft runtime
|
|
|
+libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR
|
|
|
+fetish or something like this inside Microsoft). You can increase this
|
|
|
+by calling \f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR
|
|
|
+(another arbitrary limit), but is broken in many versions of the Microsoft
|
|
|
+runtime libraries. This might get you to about \f(CW512\fR or \f(CW2048\fR sockets
|
|
|
+(depending on windows version and/or the phase of the moon). To get more,
|
|
|
+you need to wrap all I/O functions and provide your own fd management, but
|
|
|
+the cost of calling select (O(nX)) will likely make this unworkable.
|
|
|
+.SS "\s-1PORTABILITY REQUIREMENTS\s0"
|
|
|
+.IX Subsection "PORTABILITY REQUIREMENTS"
|
|
|
+In addition to a working ISO-C implementation and of course the
|
|
|
+backend-specific APIs, libev relies on a few additional extensions:
|
|
|
+.ie n .IP """void (*)(ev_watcher_type *, int revents)"" must have compatible calling conventions regardless of ""ev_watcher_type *""." 4
|
|
|
+.el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4
|
|
|
+.IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *."
|
|
|
+Libev assumes not only that all watcher pointers have the same internal
|
|
|
+structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO C\s0 for example), but it also
|
|
|
+assumes that the same (machine) code can be used to call any watcher
|
|
|
+callback: The watcher callbacks have different type signatures, but libev
|
|
|
+calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally.
|
|
|
+.IP "null pointers and integer zero are represented by 0 bytes" 4
|
|
|
+.IX Item "null pointers and integer zero are represented by 0 bytes"
|
|
|
+Libev uses \f(CW\*(C`memset\*(C'\fR to initialise structs and arrays to \f(CW0\fR bytes, and
|
|
|
+relies on this setting pointers and integers to null.
|
|
|
+.IP "pointer accesses must be thread-atomic" 4
|
|
|
+.IX Item "pointer accesses must be thread-atomic"
|
|
|
+Accessing a pointer value must be atomic, it must both be readable and
|
|
|
+writable in one piece \- this is the case on all current architectures.
|
|
|
+.ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4
|
|
|
+.el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4
|
|
|
+.IX Item "sig_atomic_t volatile must be thread-atomic as well"
|
|
|
+The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as
|
|
|
+\&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic with respect to accesses from different
|
|
|
+threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is
|
|
|
+believed to be sufficiently portable.
|
|
|
+.ie n .IP """sigprocmask"" must work in a threaded environment" 4
|
|
|
+.el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4
|
|
|
+.IX Item "sigprocmask must work in a threaded environment"
|
|
|
+Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not
|
|
|
+allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical
|
|
|
+pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main
|
|
|
+thread\*(R" or will block signals process-wide, both behaviours would
|
|
|
+be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and
|
|
|
+\&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however.
|
|
|
+.Sp
|
|
|
+The most portable way to handle signals is to block signals in all threads
|
|
|
+except the initial one, and run the signal handling loop in the initial
|
|
|
+thread as well.
|
|
|
+.ie n .IP """long"" must be large enough for common memory allocation sizes" 4
|
|
|
+.el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4
|
|
|
+.IX Item "long must be large enough for common memory allocation sizes"
|
|
|
+To improve portability and simplify its \s-1API,\s0 libev uses \f(CW\*(C`long\*(C'\fR internally
|
|
|
+instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On non-POSIX
|
|
|
+systems (Microsoft...) this might be unexpectedly low, but is still at
|
|
|
+least 31 bits everywhere, which is enough for hundreds of millions of
|
|
|
+watchers.
|
|
|
+.ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4
|
|
|
+.el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4
|
|
|
+.IX Item "double must hold a time value in seconds with enough accuracy"
|
|
|
+The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to
|
|
|
+have at least 51 bits of mantissa (and 9 bits of exponent), which is
|
|
|
+good enough for at least into the year 4000 with millisecond accuracy
|
|
|
+(the design goal for libev). This requirement is overfulfilled by
|
|
|
+implementations using \s-1IEEE 754,\s0 which is basically all existing ones.
|
|
|
+.Sp
|
|
|
+With \s-1IEEE 754\s0 doubles, you get microsecond accuracy until at least the
|
|
|
+year 2255 (and millisecond accuracy till the year 287396 \- by then, libev
|
|
|
+is either obsolete or somebody patched it to use \f(CW\*(C`long double\*(C'\fR or
|
|
|
+something like that, just kidding).
|
|
|
+.PP
|
|
|
+If you know of other additional requirements drop me a note.
|
|
|
+.SH "ALGORITHMIC COMPLEXITIES"
|
|
|
+.IX Header "ALGORITHMIC COMPLEXITIES"
|
|
|
+In this section the complexities of (many of) the algorithms used inside
|
|
|
+libev will be documented. For complexity discussions about backends see
|
|
|
+the documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
|
|
|
+.PP
|
|
|
+All of the following are about amortised time: If an array needs to be
|
|
|
+extended, libev needs to realloc and move the whole array, but this
|
|
|
+happens asymptotically rarer with higher number of elements, so O(1) might
|
|
|
+mean that libev does a lengthy realloc operation in rare cases, but on
|
|
|
+average it is much faster and asymptotically approaches constant time.
|
|
|
+.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
|
|
|
+.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
|
|
|
+This means that, when you have a watcher that triggers in one hour and
|
|
|
+there are 100 watchers that would trigger before that, then inserting will
|
|
|
+have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers.
|
|
|
+.IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4
|
|
|
+.IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)"
|
|
|
+That means that changing a timer costs less than removing/adding them,
|
|
|
+as only the relative motion in the event queue has to be paid for.
|
|
|
+.IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4
|
|
|
+.IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)"
|
|
|
+These just add the watcher into an array or at the head of a list.
|
|
|
+.IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4
|
|
|
+.IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)"
|
|
|
+.PD 0
|
|
|
+.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
|
|
|
+.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
|
|
|
+.PD
|
|
|
+These watchers are stored in lists, so they need to be walked to find the
|
|
|
+correct watcher to remove. The lists are usually short (you don't usually
|
|
|
+have many watchers waiting for the same fd or signal: one is typical, two
|
|
|
+is rare).
|
|
|
+.IP "Finding the next timer in each loop iteration: O(1)" 4
|
|
|
+.IX Item "Finding the next timer in each loop iteration: O(1)"
|
|
|
+By virtue of using a binary or 4\-heap, the next timer is always found at a
|
|
|
+fixed position in the storage array.
|
|
|
+.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
|
|
|
+.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
|
|
|
+A change means an I/O watcher gets started or stopped, which requires
|
|
|
+libev to recalculate its status (and possibly tell the kernel, depending
|
|
|
+on backend and whether \f(CW\*(C`ev_io_set\*(C'\fR was used).
|
|
|
+.IP "Activating one watcher (putting it into the pending state): O(1)" 4
|
|
|
+.IX Item "Activating one watcher (putting it into the pending state): O(1)"
|
|
|
+.PD 0
|
|
|
+.IP "Priority handling: O(number_of_priorities)" 4
|
|
|
+.IX Item "Priority handling: O(number_of_priorities)"
|
|
|
+.PD
|
|
|
+Priorities are implemented by allocating some space for each
|
|
|
+priority. When doing priority-based operations, libev usually has to
|
|
|
+linearly search all the priorities, but starting/stopping and activating
|
|
|
+watchers becomes O(1) with respect to priority handling.
|
|
|
+.IP "Sending an ev_async: O(1)" 4
|
|
|
+.IX Item "Sending an ev_async: O(1)"
|
|
|
+.PD 0
|
|
|
+.IP "Processing ev_async_send: O(number_of_async_watchers)" 4
|
|
|
+.IX Item "Processing ev_async_send: O(number_of_async_watchers)"
|
|
|
+.IP "Processing signals: O(max_signal_number)" 4
|
|
|
+.IX Item "Processing signals: O(max_signal_number)"
|
|
|
+.PD
|
|
|
+Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR
|
|
|
+calls in the current loop iteration and the loop is currently
|
|
|
+blocked. Checking for async and signal events involves iterating over all
|
|
|
+running async watchers or all signal numbers.
|
|
|
+.SH "PORTING FROM LIBEV 3.X TO 4.X"
|
|
|
+.IX Header "PORTING FROM LIBEV 3.X TO 4.X"
|
|
|
+The major version 4 introduced some incompatible changes to the \s-1API.\s0
|
|
|
+.PP
|
|
|
+At the moment, the \f(CW\*(C`ev.h\*(C'\fR header file provides compatibility definitions
|
|
|
+for all changes, so most programs should still compile. The compatibility
|
|
|
+layer might be removed in later versions of libev, so better update to the
|
|
|
+new \s-1API\s0 early than late.
|
|
|
+.ie n .IP """EV_COMPAT3"" backwards compatibility mechanism" 4
|
|
|
+.el .IP "\f(CWEV_COMPAT3\fR backwards compatibility mechanism" 4
|
|
|
+.IX Item "EV_COMPAT3 backwards compatibility mechanism"
|
|
|
+The backward compatibility mechanism can be controlled by
|
|
|
+\&\f(CW\*(C`EV_COMPAT3\*(C'\fR. See \*(L"\s-1PREPROCESSOR SYMBOLS/MACROS\*(R"\s0 in the \*(L"\s-1EMBEDDING\*(R"\s0
|
|
|
+section.
|
|
|
+.ie n .IP """ev_default_destroy"" and ""ev_default_fork"" have been removed" 4
|
|
|
+.el .IP "\f(CWev_default_destroy\fR and \f(CWev_default_fork\fR have been removed" 4
|
|
|
+.IX Item "ev_default_destroy and ev_default_fork have been removed"
|
|
|
+These calls can be replaced easily by their \f(CW\*(C`ev_loop_xxx\*(C'\fR counterparts:
|
|
|
+.Sp
|
|
|
+.Vb 2
|
|
|
+\& ev_loop_destroy (EV_DEFAULT_UC);
|
|
|
+\& ev_loop_fork (EV_DEFAULT);
|
|
|
+.Ve
|
|
|
+.IP "function/symbol renames" 4
|
|
|
+.IX Item "function/symbol renames"
|
|
|
+A number of functions and symbols have been renamed:
|
|
|
+.Sp
|
|
|
+.Vb 3
|
|
|
+\& ev_loop => ev_run
|
|
|
+\& EVLOOP_NONBLOCK => EVRUN_NOWAIT
|
|
|
+\& EVLOOP_ONESHOT => EVRUN_ONCE
|
|
|
+\&
|
|
|
+\& ev_unloop => ev_break
|
|
|
+\& EVUNLOOP_CANCEL => EVBREAK_CANCEL
|
|
|
+\& EVUNLOOP_ONE => EVBREAK_ONE
|
|
|
+\& EVUNLOOP_ALL => EVBREAK_ALL
|
|
|
+\&
|
|
|
+\& EV_TIMEOUT => EV_TIMER
|
|
|
+\&
|
|
|
+\& ev_loop_count => ev_iteration
|
|
|
+\& ev_loop_depth => ev_depth
|
|
|
+\& ev_loop_verify => ev_verify
|
|
|
+.Ve
|
|
|
+.Sp
|
|
|
+Most functions working on \f(CW\*(C`struct ev_loop\*(C'\fR objects don't have an
|
|
|
+\&\f(CW\*(C`ev_loop_\*(C'\fR prefix, so it was removed; \f(CW\*(C`ev_loop\*(C'\fR, \f(CW\*(C`ev_unloop\*(C'\fR and
|
|
|
+associated constants have been renamed to not collide with the \f(CW\*(C`struct
|
|
|
+ev_loop\*(C'\fR anymore and \f(CW\*(C`EV_TIMER\*(C'\fR now follows the same naming scheme
|
|
|
+as all other watcher types. Note that \f(CW\*(C`ev_loop_fork\*(C'\fR is still called
|
|
|
+\&\f(CW\*(C`ev_loop_fork\*(C'\fR because it would otherwise clash with the \f(CW\*(C`ev_fork\*(C'\fR
|
|
|
+typedef.
|
|
|
+.ie n .IP """EV_MINIMAL"" mechanism replaced by ""EV_FEATURES""" 4
|
|
|
+.el .IP "\f(CWEV_MINIMAL\fR mechanism replaced by \f(CWEV_FEATURES\fR" 4
|
|
|
+.IX Item "EV_MINIMAL mechanism replaced by EV_FEATURES"
|
|
|
+The preprocessor symbol \f(CW\*(C`EV_MINIMAL\*(C'\fR has been replaced by a different
|
|
|
+mechanism, \f(CW\*(C`EV_FEATURES\*(C'\fR. Programs using \f(CW\*(C`EV_MINIMAL\*(C'\fR usually compile
|
|
|
+and work, but the library code will of course be larger.
|
|
|
+.SH "GLOSSARY"
|
|
|
+.IX Header "GLOSSARY"
|
|
|
+.IP "active" 4
|
|
|
+.IX Item "active"
|
|
|
+A watcher is active as long as it has been started and not yet stopped.
|
|
|
+See \*(L"\s-1WATCHER STATES\*(R"\s0 for details.
|
|
|
+.IP "application" 4
|
|
|
+.IX Item "application"
|
|
|
+In this document, an application is whatever is using libev.
|
|
|
+.IP "backend" 4
|
|
|
+.IX Item "backend"
|
|
|
+The part of the code dealing with the operating system interfaces.
|
|
|
+.IP "callback" 4
|
|
|
+.IX Item "callback"
|
|
|
+The address of a function that is called when some event has been
|
|
|
+detected. Callbacks are being passed the event loop, the watcher that
|
|
|
+received the event, and the actual event bitset.
|
|
|
+.IP "callback/watcher invocation" 4
|
|
|
+.IX Item "callback/watcher invocation"
|
|
|
+The act of calling the callback associated with a watcher.
|
|
|
+.IP "event" 4
|
|
|
+.IX Item "event"
|
|
|
+A change of state of some external event, such as data now being available
|
|
|
+for reading on a file descriptor, time having passed or simply not having
|
|
|
+any other events happening anymore.
|
|
|
+.Sp
|
|
|
+In libev, events are represented as single bits (such as \f(CW\*(C`EV_READ\*(C'\fR or
|
|
|
+\&\f(CW\*(C`EV_TIMER\*(C'\fR).
|
|
|
+.IP "event library" 4
|
|
|
+.IX Item "event library"
|
|
|
+A software package implementing an event model and loop.
|
|
|
+.IP "event loop" 4
|
|
|
+.IX Item "event loop"
|
|
|
+An entity that handles and processes external events and converts them
|
|
|
+into callback invocations.
|
|
|
+.IP "event model" 4
|
|
|
+.IX Item "event model"
|
|
|
+The model used to describe how an event loop handles and processes
|
|
|
+watchers and events.
|
|
|
+.IP "pending" 4
|
|
|
+.IX Item "pending"
|
|
|
+A watcher is pending as soon as the corresponding event has been
|
|
|
+detected. See \*(L"\s-1WATCHER STATES\*(R"\s0 for details.
|
|
|
+.IP "real time" 4
|
|
|
+.IX Item "real time"
|
|
|
+The physical time that is observed. It is apparently strictly monotonic :)
|
|
|
+.IP "wall-clock time" 4
|
|
|
+.IX Item "wall-clock time"
|
|
|
+The time and date as shown on clocks. Unlike real time, it can actually
|
|
|
+be wrong and jump forwards and backwards, e.g. when you adjust your
|
|
|
+clock.
|
|
|
+.IP "watcher" 4
|
|
|
+.IX Item "watcher"
|
|
|
+A data structure that describes interest in certain events. Watchers need
|
|
|
+to be started (attached to an event loop) before they can receive events.
|
|
|
+.SH "AUTHOR"
|
|
|
+.IX Header "AUTHOR"
|
|
|
+Marc Lehmann <[email protected]>, with repeated corrections by Mikael
|
|
|
+Magnusson and Emanuele Giaquinta, and minor corrections by many others.
|
wangyu-