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@@ -1,300 +0,0 @@
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-// Copyright 2014 The Go Authors. All rights reserved.
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-// Use of this source code is governed by a BSD-style
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-// license that can be found in the LICENSE file.
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-
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-// +build !go1.7
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-
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-package context
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-
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-import (
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- "errors"
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- "fmt"
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- "sync"
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- "time"
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-)
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-
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-// An emptyCtx is never canceled, has no values, and has no deadline. It is not
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-// struct{}, since vars of this type must have distinct addresses.
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-type emptyCtx int
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-
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-func (*emptyCtx) Deadline() (deadline time.Time, ok bool) {
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- return
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-}
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-
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-func (*emptyCtx) Done() <-chan struct{} {
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- return nil
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-}
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-
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-func (*emptyCtx) Err() error {
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- return nil
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-}
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-
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-func (*emptyCtx) Value(key interface{}) interface{} {
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- return nil
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-}
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-
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-func (e *emptyCtx) String() string {
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- switch e {
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- case background:
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- return "context.Background"
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- case todo:
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- return "context.TODO"
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- }
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- return "unknown empty Context"
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-}
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-
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-var (
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- background = new(emptyCtx)
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- todo = new(emptyCtx)
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-)
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-
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-// Canceled is the error returned by Context.Err when the context is canceled.
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-var Canceled = errors.New("context canceled")
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-
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-// DeadlineExceeded is the error returned by Context.Err when the context's
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-// deadline passes.
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-var DeadlineExceeded = errors.New("context deadline exceeded")
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-
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-// WithCancel returns a copy of parent with a new Done channel. The returned
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-// context's Done channel is closed when the returned cancel function is called
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-// or when the parent context's Done channel is closed, whichever happens first.
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-//
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-// Canceling this context releases resources associated with it, so code should
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-// call cancel as soon as the operations running in this Context complete.
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-func WithCancel(parent Context) (ctx Context, cancel CancelFunc) {
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- c := newCancelCtx(parent)
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- propagateCancel(parent, c)
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- return c, func() { c.cancel(true, Canceled) }
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-}
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-
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-// newCancelCtx returns an initialized cancelCtx.
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-func newCancelCtx(parent Context) *cancelCtx {
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- return &cancelCtx{
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- Context: parent,
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- done: make(chan struct{}),
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- }
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-}
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-
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-// propagateCancel arranges for child to be canceled when parent is.
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-func propagateCancel(parent Context, child canceler) {
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- if parent.Done() == nil {
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- return // parent is never canceled
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- }
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- if p, ok := parentCancelCtx(parent); ok {
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- p.mu.Lock()
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- if p.err != nil {
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- // parent has already been canceled
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- child.cancel(false, p.err)
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- } else {
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- if p.children == nil {
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- p.children = make(map[canceler]bool)
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- }
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- p.children[child] = true
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- }
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- p.mu.Unlock()
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- } else {
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- go func() {
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- select {
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- case <-parent.Done():
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- child.cancel(false, parent.Err())
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- case <-child.Done():
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- }
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- }()
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- }
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-}
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-
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-// parentCancelCtx follows a chain of parent references until it finds a
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-// *cancelCtx. This function understands how each of the concrete types in this
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-// package represents its parent.
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-func parentCancelCtx(parent Context) (*cancelCtx, bool) {
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- for {
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- switch c := parent.(type) {
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- case *cancelCtx:
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- return c, true
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- case *timerCtx:
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- return c.cancelCtx, true
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- case *valueCtx:
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- parent = c.Context
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- default:
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- return nil, false
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- }
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- }
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-}
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-
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-// removeChild removes a context from its parent.
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-func removeChild(parent Context, child canceler) {
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- p, ok := parentCancelCtx(parent)
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- if !ok {
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- return
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- }
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- p.mu.Lock()
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- if p.children != nil {
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- delete(p.children, child)
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- }
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- p.mu.Unlock()
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-}
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-
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-// A canceler is a context type that can be canceled directly. The
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-// implementations are *cancelCtx and *timerCtx.
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-type canceler interface {
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- cancel(removeFromParent bool, err error)
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- Done() <-chan struct{}
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-}
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-
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-// A cancelCtx can be canceled. When canceled, it also cancels any children
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-// that implement canceler.
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-type cancelCtx struct {
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- Context
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-
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- done chan struct{} // closed by the first cancel call.
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-
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- mu sync.Mutex
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- children map[canceler]bool // set to nil by the first cancel call
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- err error // set to non-nil by the first cancel call
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-}
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-
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-func (c *cancelCtx) Done() <-chan struct{} {
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- return c.done
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-}
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-
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-func (c *cancelCtx) Err() error {
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- c.mu.Lock()
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- defer c.mu.Unlock()
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- return c.err
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-}
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-
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-func (c *cancelCtx) String() string {
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- return fmt.Sprintf("%v.WithCancel", c.Context)
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-}
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-
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-// cancel closes c.done, cancels each of c's children, and, if
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-// removeFromParent is true, removes c from its parent's children.
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-func (c *cancelCtx) cancel(removeFromParent bool, err error) {
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- if err == nil {
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- panic("context: internal error: missing cancel error")
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- }
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- c.mu.Lock()
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- if c.err != nil {
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- c.mu.Unlock()
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- return // already canceled
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- }
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- c.err = err
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- close(c.done)
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- for child := range c.children {
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- // NOTE: acquiring the child's lock while holding parent's lock.
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- child.cancel(false, err)
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- }
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- c.children = nil
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- c.mu.Unlock()
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-
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- if removeFromParent {
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- removeChild(c.Context, c)
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- }
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-}
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-
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-// WithDeadline returns a copy of the parent context with the deadline adjusted
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-// to be no later than d. If the parent's deadline is already earlier than d,
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-// WithDeadline(parent, d) is semantically equivalent to parent. The returned
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-// context's Done channel is closed when the deadline expires, when the returned
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-// cancel function is called, or when the parent context's Done channel is
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-// closed, whichever happens first.
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-//
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-// Canceling this context releases resources associated with it, so code should
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-// call cancel as soon as the operations running in this Context complete.
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-func WithDeadline(parent Context, deadline time.Time) (Context, CancelFunc) {
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- if cur, ok := parent.Deadline(); ok && cur.Before(deadline) {
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- // The current deadline is already sooner than the new one.
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- return WithCancel(parent)
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- }
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- c := &timerCtx{
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- cancelCtx: newCancelCtx(parent),
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- deadline: deadline,
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- }
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- propagateCancel(parent, c)
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- d := deadline.Sub(time.Now())
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- if d <= 0 {
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- c.cancel(true, DeadlineExceeded) // deadline has already passed
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- return c, func() { c.cancel(true, Canceled) }
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- }
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- c.mu.Lock()
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- defer c.mu.Unlock()
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- if c.err == nil {
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- c.timer = time.AfterFunc(d, func() {
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- c.cancel(true, DeadlineExceeded)
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- })
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- }
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- return c, func() { c.cancel(true, Canceled) }
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-}
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-
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-// A timerCtx carries a timer and a deadline. It embeds a cancelCtx to
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-// implement Done and Err. It implements cancel by stopping its timer then
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-// delegating to cancelCtx.cancel.
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-type timerCtx struct {
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- *cancelCtx
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- timer *time.Timer // Under cancelCtx.mu.
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-
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- deadline time.Time
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-}
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-
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-func (c *timerCtx) Deadline() (deadline time.Time, ok bool) {
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- return c.deadline, true
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-}
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-
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-func (c *timerCtx) String() string {
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- return fmt.Sprintf("%v.WithDeadline(%s [%s])", c.cancelCtx.Context, c.deadline, c.deadline.Sub(time.Now()))
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-}
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-
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-func (c *timerCtx) cancel(removeFromParent bool, err error) {
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- c.cancelCtx.cancel(false, err)
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- if removeFromParent {
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- // Remove this timerCtx from its parent cancelCtx's children.
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- removeChild(c.cancelCtx.Context, c)
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- }
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- c.mu.Lock()
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- if c.timer != nil {
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- c.timer.Stop()
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- c.timer = nil
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- }
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- c.mu.Unlock()
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-}
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-
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-// WithTimeout returns WithDeadline(parent, time.Now().Add(timeout)).
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-//
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-// Canceling this context releases resources associated with it, so code should
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-// call cancel as soon as the operations running in this Context complete:
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-//
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-// func slowOperationWithTimeout(ctx context.Context) (Result, error) {
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-// ctx, cancel := context.WithTimeout(ctx, 100*time.Millisecond)
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-// defer cancel() // releases resources if slowOperation completes before timeout elapses
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-// return slowOperation(ctx)
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-// }
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-func WithTimeout(parent Context, timeout time.Duration) (Context, CancelFunc) {
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- return WithDeadline(parent, time.Now().Add(timeout))
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-}
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-
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-// WithValue returns a copy of parent in which the value associated with key is
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-// val.
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-//
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-// Use context Values only for request-scoped data that transits processes and
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-// APIs, not for passing optional parameters to functions.
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-func WithValue(parent Context, key interface{}, val interface{}) Context {
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- return &valueCtx{parent, key, val}
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-}
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-
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-// A valueCtx carries a key-value pair. It implements Value for that key and
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-// delegates all other calls to the embedded Context.
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-type valueCtx struct {
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- Context
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- key, val interface{}
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-}
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-
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-func (c *valueCtx) String() string {
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- return fmt.Sprintf("%v.WithValue(%#v, %#v)", c.Context, c.key, c.val)
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-}
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-
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-func (c *valueCtx) Value(key interface{}) interface{} {
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- if c.key == key {
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- return c.val
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- }
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- return c.Context.Value(key)
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-}
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Jakob Borg