restic/internal/fs/file_windows.go

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package fs
import (
"math/rand"
"os"
"path/filepath"
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"strconv"
"strings"
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"time"
"golang.org/x/sys/windows"
)
// fixpath returns an absolute path on windows, so restic can open long file
// names.
func fixpath(name string) string {
abspath, err := filepath.Abs(name)
if err == nil {
// Check if \\?\UNC\ already exist
if strings.HasPrefix(abspath, `\\?\UNC\`) {
return abspath
}
// Check if \\?\ already exist
if strings.HasPrefix(abspath, `\\?\`) {
return abspath
}
// Check if path starts with \\
if strings.HasPrefix(abspath, `\\`) {
return strings.Replace(abspath, `\\`, `\\?\UNC\`, 1)
}
// Normal path
return `\\?\` + abspath
}
return name
}
// TempFile creates a temporary file which is marked as delete-on-close
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func TempFile(dir, prefix string) (f *os.File, err error) {
// slightly modified implementation of os.CreateTemp(dir, prefix) to allow us to add
// the FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE flags.
// These provide two large benefits:
// FILE_ATTRIBUTE_TEMPORARY tells Windows to keep the file in memory only if possible
// which reduces the amount of unnecessary disk writes.
// FILE_FLAG_DELETE_ON_CLOSE instructs Windows to automatically delete the file once
// all file descriptors are closed.
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if dir == "" {
dir = os.TempDir()
}
access := uint32(windows.GENERIC_READ | windows.GENERIC_WRITE)
creation := uint32(windows.CREATE_NEW)
share := uint32(0) // prevent other processes from accessing the file
flags := uint32(windows.FILE_ATTRIBUTE_TEMPORARY | windows.FILE_FLAG_DELETE_ON_CLOSE)
rnd := rand.New(rand.NewSource(time.Now().UnixNano()))
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for i := 0; i < 10000; i++ {
randSuffix := strconv.Itoa(int(1e9 + rnd.Intn(1e9)%1e9))[1:]
path := filepath.Join(dir, prefix+randSuffix)
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ptr, err := windows.UTF16PtrFromString(path)
if err != nil {
return nil, err
}
h, err := windows.CreateFile(ptr, access, share, nil, creation, flags, 0)
if os.IsExist(err) {
continue
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}
return os.NewFile(uintptr(h), path), err
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}
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// Proper error handling is still to do
return nil, os.ErrExist
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}
// Chmod changes the mode of the named file to mode.
func Chmod(name string, mode os.FileMode) error {
return os.Chmod(fixpath(name), mode)
}
// ClearSystem removes the system attribute from the file.
func ClearSystem(path string) error {
return ClearAttribute(path, windows.FILE_ATTRIBUTE_SYSTEM)
}
// ClearAttribute removes the specified attribute from the file.
func ClearAttribute(path string, attribute uint32) error {
ptr, err := windows.UTF16PtrFromString(path)
if err != nil {
return err
}
fileAttributes, err := windows.GetFileAttributes(ptr)
if err != nil {
return err
}
if fileAttributes&attribute != 0 {
// Clear the attribute
fileAttributes &= ^uint32(attribute)
err = windows.SetFileAttributes(ptr, fileAttributes)
if err != nil {
return err
}
}
return nil
}