mirror of
https://github.com/octoleo/syncthing.git
synced 2024-11-19 03:25:16 +00:00
105 lines
2.5 KiB
Go
105 lines
2.5 KiB
Go
// Copyright (C) 2015 The Syncthing Authors.
|
|
//
|
|
// This Source Code Form is subject to the terms of the Mozilla Public
|
|
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
|
|
// You can obtain one at http://mozilla.org/MPL/2.0/.
|
|
|
|
package osutil
|
|
|
|
import (
|
|
"errors"
|
|
"io/ioutil"
|
|
"os"
|
|
"path/filepath"
|
|
"runtime"
|
|
)
|
|
|
|
var (
|
|
ErrClosed = errors.New("write to closed writer")
|
|
TempPrefix = ".syncthing.tmp."
|
|
)
|
|
|
|
// An AtomicWriter is an *os.File that writes to a temporary file in the same
|
|
// directory as the final path. On successfull Close the file is renamed to
|
|
// it's final path. Any error on Write or during Close is accumulated and
|
|
// returned on Close, so a lazy user can ignore errors until Close.
|
|
type AtomicWriter struct {
|
|
path string
|
|
next *os.File
|
|
err error
|
|
}
|
|
|
|
// CreateAtomic is like os.Create with a FileMode, except a temporary file
|
|
// name is used instead of the given name.
|
|
func CreateAtomic(path string, mode os.FileMode) (*AtomicWriter, error) {
|
|
fd, err := ioutil.TempFile(filepath.Dir(path), TempPrefix)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// chmod fails on Android so don't even try
|
|
if runtime.GOOS != "android" {
|
|
if err := os.Chmod(fd.Name(), mode); err != nil {
|
|
fd.Close()
|
|
os.Remove(fd.Name())
|
|
return nil, err
|
|
}
|
|
}
|
|
|
|
w := &AtomicWriter{
|
|
path: path,
|
|
next: fd,
|
|
}
|
|
|
|
return w, nil
|
|
}
|
|
|
|
// Write is like io.Writer, but is a no-op on an already failed AtomicWriter.
|
|
func (w *AtomicWriter) Write(bs []byte) (int, error) {
|
|
if w.err != nil {
|
|
return 0, w.err
|
|
}
|
|
n, err := w.next.Write(bs)
|
|
if err != nil {
|
|
w.err = err
|
|
w.next.Close()
|
|
}
|
|
return n, err
|
|
}
|
|
|
|
// Close closes the temporary file and renames it to the final path. It is
|
|
// invalid to call Write() or Close() after Close().
|
|
func (w *AtomicWriter) Close() error {
|
|
if w.err != nil {
|
|
return w.err
|
|
}
|
|
|
|
// Try to not leave temp file around, but ignore error.
|
|
defer os.Remove(w.next.Name())
|
|
|
|
if err := w.next.Close(); err != nil {
|
|
w.err = err
|
|
return err
|
|
}
|
|
|
|
// Remove the destination file, on Windows only. If it fails, and not due
|
|
// to the file not existing, we won't be able to complete the rename
|
|
// either. Return this error because it may be more informative. On non-
|
|
// Windows we want the atomic rename behavior so we don't attempt remove.
|
|
if runtime.GOOS == "windows" {
|
|
if err := os.Remove(w.path); err != nil && !os.IsNotExist(err) {
|
|
return err
|
|
}
|
|
}
|
|
|
|
if err := os.Rename(w.next.Name(), w.path); err != nil {
|
|
w.err = err
|
|
return err
|
|
}
|
|
|
|
// Set w.err to return appropriately for any future operations.
|
|
w.err = ErrClosed
|
|
|
|
return nil
|
|
}
|