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- // Copyright 2009 The Go Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style
- // license that can be found in the LICENSE file.
- package os_overloads
- import (
- "os"
- "syscall"
- "golang.org/x/sys/windows"
- )
- func isAbs(path string) (b bool) {
- v := volumeName(path)
- if v == "" {
- return false
- }
- path = path[len(v):]
- if path == "" {
- return false
- }
- return os.IsPathSeparator(path[0])
- }
- func volumeName(path string) (v string) {
- if len(path) < 2 {
- return ""
- }
- // with drive letter
- c := path[0]
- if path[1] == ':' &&
- ('0' <= c && c <= '9' || 'a' <= c && c <= 'z' ||
- 'A' <= c && c <= 'Z') {
- return path[:2]
- }
- // is it UNC
- if l := len(path); l >= 5 && os.IsPathSeparator(path[0]) && os.IsPathSeparator(path[1]) &&
- !os.IsPathSeparator(path[2]) && path[2] != '.' {
- // first, leading `\\` and next shouldn't be `\`. its server name.
- for n := 3; n < l-1; n++ {
- // second, next '\' shouldn't be repeated.
- if os.IsPathSeparator(path[n]) {
- n++
- // third, following something characters. its share name.
- if !os.IsPathSeparator(path[n]) {
- if path[n] == '.' {
- break
- }
- for ; n < l; n++ {
- if os.IsPathSeparator(path[n]) {
- break
- }
- }
- return path[:n]
- }
- break
- }
- }
- }
- return ""
- }
- // fixLongPath returns the extended-length (\\?\-prefixed) form of
- // path when needed, in order to avoid the default 260 character file
- // path limit imposed by Windows. If path is not easily converted to
- // the extended-length form (for example, if path is a relative path
- // or contains .. elements), or is short enough, fixLongPath returns
- // path unmodified.
- //
- // See https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx#maxpath
- func fixLongPath(path string) string {
- // Do nothing (and don't allocate) if the path is "short".
- // Empirically (at least on the Windows Server 2013 builder),
- // the kernel is arbitrarily okay with < 248 bytes. That
- // matches what the docs above say:
- // "When using an API to create a directory, the specified
- // path cannot be so long that you cannot append an 8.3 file
- // name (that is, the directory name cannot exceed MAX_PATH
- // minus 12)." Since MAX_PATH is 260, 260 - 12 = 248.
- //
- // The MSDN docs appear to say that a normal path that is 248 bytes long
- // will work; empirically the path must be less then 248 bytes long.
- if len(path) < 248 {
- // Don't fix. (This is how Go 1.7 and earlier worked,
- // not automatically generating the \\?\ form)
- return path
- }
- // The extended form begins with \\?\, as in
- // \\?\c:\windows\foo.txt or \\?\UNC\server\share\foo.txt.
- // The extended form disables evaluation of . and .. path
- // elements and disables the interpretation of / as equivalent
- // to \. The conversion here rewrites / to \ and elides
- // . elements as well as trailing or duplicate separators. For
- // simplicity it avoids the conversion entirely for relative
- // paths or paths containing .. elements. For now,
- // \\server\share paths are not converted to
- // \\?\UNC\server\share paths because the rules for doing so
- // are less well-specified.
- if len(path) >= 2 && path[:2] == `\\` {
- // Don't canonicalize UNC paths.
- return path
- }
- if !isAbs(path) {
- // Relative path
- return path
- }
- const prefix = `\\?`
- pathbuf := make([]byte, len(prefix)+len(path)+len(`\`))
- copy(pathbuf, prefix)
- n := len(path)
- r, w := 0, len(prefix)
- for r < n {
- switch {
- case os.IsPathSeparator(path[r]):
- // empty block
- r++
- case path[r] == '.' && (r+1 == n || os.IsPathSeparator(path[r+1])):
- // /./
- r++
- case r+1 < n && path[r] == '.' && path[r+1] == '.' && (r+2 == n || os.IsPathSeparator(path[r+2])):
- // /../ is currently unhandled
- return path
- default:
- pathbuf[w] = '\\'
- w++
- for ; r < n && !os.IsPathSeparator(path[r]); r++ {
- pathbuf[w] = path[r]
- w++
- }
- }
- }
- // A drive's root directory needs a trailing \
- if w == len(`\\?\c:`) {
- pathbuf[w] = '\\'
- w++
- }
- return string(pathbuf[:w])
- }
- // syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
- func syscallMode(i os.FileMode) (o uint32) {
- o |= uint32(i.Perm())
- if i&os.ModeSetuid != 0 {
- o |= syscall.S_ISUID
- }
- if i&os.ModeSetgid != 0 {
- o |= syscall.S_ISGID
- }
- if i&os.ModeSticky != 0 {
- o |= syscall.S_ISVTX
- }
- // No mapping for Go's ModeTemporary (plan9 only).
- return
- }
- //If the bool is set to true then the file is opened with the parameters FILE_ATTRIBUTE_TEMPORARY and
- // FILE_FLAG_DELETE_ON_CLOSE
- func OpenFile(name string, flag int, perm os.FileMode, setToTempAndDelete bool) (file *os.File, err error) {
- r, e := Open(fixLongPath(name), flag|windows.O_CLOEXEC, syscallMode(perm), setToTempAndDelete)
- if e != nil {
- return nil, e
- }
- return os.NewFile(uintptr(r), name), nil
- }
|