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@@ -0,0 +1,137 @@
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+// Copyright 2009 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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+package osutil
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+
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+import (
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+ "os"
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+ "path/filepath"
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+ "syscall"
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+)
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+
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+// DebugSymlinkForTestsOnly is os.Symlink taken from the 1.9.2 stdlib,
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+// hacked with the SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE flag to
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+// create symlinks when not elevated.
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+//
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+// This is not and should not be used in Syncthing code, hence the
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+// cumbersome name to make it obvious if this ever leaks. Nonetheless it's
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+// useful in tests.
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+func DebugSymlinkForTestsOnly(oldname, newname string) error {
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+ // CreateSymbolicLink is not supported before Windows Vista
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+ if syscall.LoadCreateSymbolicLink() != nil {
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+ return &os.LinkError{"symlink", oldname, newname, syscall.EWINDOWS}
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+ }
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+
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+ // '/' does not work in link's content
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+ oldname = filepath.FromSlash(oldname)
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+
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+ // need the exact location of the oldname when its relative to determine if its a directory
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+ destpath := oldname
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+ if !filepath.IsAbs(oldname) {
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+ destpath = filepath.Dir(newname) + `\` + oldname
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+ }
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+
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+ fi, err := os.Lstat(destpath)
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+ isdir := err == nil && fi.IsDir()
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+
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+ n, err := syscall.UTF16PtrFromString(fixLongPath(newname))
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+ if err != nil {
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+ return &os.LinkError{"symlink", oldname, newname, err}
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+ }
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+ o, err := syscall.UTF16PtrFromString(fixLongPath(oldname))
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+ if err != nil {
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+ return &os.LinkError{"symlink", oldname, newname, err}
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+ }
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+
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+ var flags uint32
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+ if isdir {
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+ flags |= syscall.SYMBOLIC_LINK_FLAG_DIRECTORY
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+ }
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+ flags |= 0x02 // SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE
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+ err = syscall.CreateSymbolicLink(n, o, flags)
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+ if err != nil {
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+ return &os.LinkError{"symlink", oldname, newname, err}
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+ }
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+ return nil
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+}
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+
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+// fixLongPath returns the extended-length (\\?\-prefixed) form of
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+// path when needed, in order to avoid the default 260 character file
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+// path limit imposed by Windows. If path is not easily converted to
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+// the extended-length form (for example, if path is a relative path
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+// or contains .. elements), or is short enough, fixLongPath returns
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+// path unmodified.
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+//
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+// See https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx#maxpath
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+func fixLongPath(path string) string {
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+ // Do nothing (and don't allocate) if the path is "short".
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+ // Empirically (at least on the Windows Server 2013 builder),
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+ // the kernel is arbitrarily okay with < 248 bytes. That
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+ // matches what the docs above say:
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+ // "When using an API to create a directory, the specified
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+ // path cannot be so long that you cannot append an 8.3 file
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+ // name (that is, the directory name cannot exceed MAX_PATH
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+ // minus 12)." Since MAX_PATH is 260, 260 - 12 = 248.
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+ //
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+ // The MSDN docs appear to say that a normal path that is 248 bytes long
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+ // will work; empirically the path must be less then 248 bytes long.
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+ if len(path) < 248 {
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+ // Don't fix. (This is how Go 1.7 and earlier worked,
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+ // not automatically generating the \\?\ form)
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+ return path
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+ }
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+
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+ // The extended form begins with \\?\, as in
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+ // \\?\c:\windows\foo.txt or \\?\UNC\server\share\foo.txt.
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+ // The extended form disables evaluation of . and .. path
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+ // elements and disables the interpretation of / as equivalent
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+ // to \. The conversion here rewrites / to \ and elides
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+ // . elements as well as trailing or duplicate separators. For
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+ // simplicity it avoids the conversion entirely for relative
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+ // paths or paths containing .. elements. For now,
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+ // \\server\share paths are not converted to
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+ // \\?\UNC\server\share paths because the rules for doing so
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+ // are less well-specified.
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+ if len(path) >= 2 && path[:2] == `\\` {
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+ // Don't canonicalize UNC paths.
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+ return path
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+ }
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+ if !filepath.IsAbs(path) {
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+ // Relative path
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+ return path
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+ }
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+
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+ const prefix = `\\?`
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+
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+ pathbuf := make([]byte, len(prefix)+len(path)+len(`\`))
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+ copy(pathbuf, prefix)
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+ n := len(path)
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+ r, w := 0, len(prefix)
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+ for r < n {
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+ switch {
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+ case os.IsPathSeparator(path[r]):
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+ // empty block
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+ r++
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+ case path[r] == '.' && (r+1 == n || os.IsPathSeparator(path[r+1])):
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+ // /./
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+ r++
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+ case r+1 < n && path[r] == '.' && path[r+1] == '.' && (r+2 == n || os.IsPathSeparator(path[r+2])):
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+ // /../ is currently unhandled
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+ return path
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+ default:
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+ pathbuf[w] = '\\'
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+ w++
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+ for ; r < n && !os.IsPathSeparator(path[r]); r++ {
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+ pathbuf[w] = path[r]
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+ w++
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+ }
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+ }
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+ }
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+ // A drive's root directory needs a trailing \
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+ if w == len(`\\?\c:`) {
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+ pathbuf[w] = '\\'
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+ w++
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+ }
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+ return string(pathbuf[:w])
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+}
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Jakob Borg