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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
}
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