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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
import (
"internal/syscall/windows"
"syscall"
"unsafe"
)
// Stat returns the FileInfo structure describing file.
// If there is an error, it will be of type *PathError.
func (file *File) Stat() (FileInfo, error) {
if file == nil {
return nil, ErrInvalid
}
return statHandle(file.name, file.pfd.Sysfd)
}
// stat implements both Stat and Lstat of a file.
func stat(funcname, name string, followSurrogates bool) (FileInfo, error) {
if len(name) == 0 {
return nil, &PathError{Op: funcname, Path: name, Err: syscall.Errno(syscall.ERROR_PATH_NOT_FOUND)}
}
namep, err := syscall.UTF16PtrFromString(fixLongPath(name))
if err != nil {
return nil, &PathError{Op: funcname, Path: name, Err: err}
}
// Try GetFileAttributesEx first, because it is faster than CreateFile.
// See https://golang.org/issues/19922#issuecomment-300031421 for details.
var fa syscall.Win32FileAttributeData
err = syscall.GetFileAttributesEx(namep, syscall.GetFileExInfoStandard, (*byte)(unsafe.Pointer(&fa)))
// GetFileAttributesEx fails with ERROR_SHARING_VIOLATION error for
// files like c:\pagefile.sys. Use FindFirstFile for such files.
if err == windows.ERROR_SHARING_VIOLATION {
var fd syscall.Win32finddata
sh, err := syscall.FindFirstFile(namep, &fd)
if err != nil {
return nil, &PathError{Op: "FindFirstFile", Path: name, Err: err}
}
syscall.FindClose(sh)
if fd.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT == 0 {
// Not a surrogate for another named entity. FindFirstFile is good enough.
fs := newFileStatFromWin32finddata(&fd)
if err := fs.saveInfoFromPath(name); err != nil {
return nil, err
}
return fs, nil
}
}
if err == nil && fa.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT == 0 {
// Not a surrogate for another named entity, because it isn't any kind of reparse point.
// The information we got from GetFileAttributesEx is good enough for now.
fs := &fileStat{
FileAttributes: fa.FileAttributes,
CreationTime: fa.CreationTime,
LastAccessTime: fa.LastAccessTime,
LastWriteTime: fa.LastWriteTime,
FileSizeHigh: fa.FileSizeHigh,
FileSizeLow: fa.FileSizeLow,
}
if err := fs.saveInfoFromPath(name); err != nil {
return nil, err
}
return fs, nil
}
// Use CreateFile to determine whether the file is a name surrogate and, if so,
// save information about the link target.
// Set FILE_FLAG_BACKUP_SEMANTICS so that CreateFile will create the handle
// even if name refers to a directory.
h, err := syscall.CreateFile(namep, 0, 0, nil, syscall.OPEN_EXISTING, syscall.FILE_FLAG_BACKUP_SEMANTICS|syscall.FILE_FLAG_OPEN_REPARSE_POINT, 0)
if err != nil {
// Since CreateFile failed, we can't determine whether name refers to a
// name surrogate, or some other kind of reparse point. Since we can't return a
// FileInfo with a known-accurate Mode, we must return an error.
return nil, &PathError{Op: "CreateFile", Path: name, Err: err}
}
fi, err := statHandle(name, h)
syscall.CloseHandle(h)
if err == nil && followSurrogates && fi.(*fileStat).isReparseTagNameSurrogate() {
// To obtain information about the link target, we reopen the file without
// FILE_FLAG_OPEN_REPARSE_POINT and examine the resulting handle.
// (See https://devblogs.microsoft.com/oldnewthing/20100212-00/?p=14963.)
h, err = syscall.CreateFile(namep, 0, 0, nil, syscall.OPEN_EXISTING, syscall.FILE_FLAG_BACKUP_SEMANTICS, 0)
if err != nil {
// name refers to a symlink, but we couldn't resolve the symlink target.
return nil, &PathError{Op: "CreateFile", Path: name, Err: err}
}
defer syscall.CloseHandle(h)
return statHandle(name, h)
}
return fi, err
}
func statHandle(name string, h syscall.Handle) (FileInfo, error) {
ft, err := syscall.GetFileType(h)
if err != nil {
return nil, &PathError{Op: "GetFileType", Path: name, Err: err}
}
switch ft {
case syscall.FILE_TYPE_PIPE, syscall.FILE_TYPE_CHAR:
return &fileStat{name: basename(name), filetype: ft}, nil
}
fs, err := newFileStatFromGetFileInformationByHandle(name, h)
if err != nil {
return nil, err
}
fs.filetype = ft
return fs, err
}
// statNolog implements Stat for Windows.
func statNolog(name string) (FileInfo, error) {
return stat("Stat", name, true)
}
// lstatNolog implements Lstat for Windows.
func lstatNolog(name string) (FileInfo, error) {
followSurrogates := false
if name != "" && IsPathSeparator(name[len(name)-1]) {
// We try to implement POSIX semantics for Lstat path resolution
// (per https://pubs.opengroup.org/onlinepubs/9699919799.2013edition/basedefs/V1_chap04.html#tag_04_12):
// symlinks before the last separator in the path must be resolved. Since
// the last separator in this case follows the last path element, we should
// follow symlinks in the last path element.
followSurrogates = true
}
return stat("Lstat", name, followSurrogates)
}
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