mirror of https://github.com/tidwall/tile38.git
94 lines
2.8 KiB
Go
94 lines
2.8 KiB
Go
|
// Copyright 2018 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 renameio writes files atomically by renaming temporary files.
|
||
|
|
package renameio
|
||
|
|
|
||
|
|
import (
|
||
|
|
"bytes"
|
||
|
|
"io"
|
||
|
|
"math/rand"
|
||
|
|
"os"
|
||
|
|
"path/filepath"
|
||
|
|
"strconv"
|
||
|
|
|
||
|
|
"honnef.co/go/tools/internal/robustio"
|
||
|
|
)
|
||
|
|
|
||
|
|
const patternSuffix = ".tmp"
|
||
|
|
|
||
|
|
// Pattern returns a glob pattern that matches the unrenamed temporary files
|
||
|
|
// created when writing to filename.
|
||
|
|
func Pattern(filename string) string {
|
||
|
|
return filepath.Join(filepath.Dir(filename), filepath.Base(filename)+patternSuffix)
|
||
|
|
}
|
||
|
|
|
||
|
|
// WriteFile is like ioutil.WriteFile, but first writes data to an arbitrary
|
||
|
|
// file in the same directory as filename, then renames it atomically to the
|
||
|
|
// final name.
|
||
|
|
//
|
||
|
|
// That ensures that the final location, if it exists, is always a complete file.
|
||
|
|
func WriteFile(filename string, data []byte, perm os.FileMode) (err error) {
|
||
|
|
return WriteToFile(filename, bytes.NewReader(data), perm)
|
||
|
|
}
|
||
|
|
|
||
|
|
// WriteToFile is a variant of WriteFile that accepts the data as an io.Reader
|
||
|
|
// instead of a slice.
|
||
|
|
func WriteToFile(filename string, data io.Reader, perm os.FileMode) (err error) {
|
||
|
|
f, err := tempFile(filepath.Dir(filename), filepath.Base(filename), perm)
|
||
|
|
if err != nil {
|
||
|
|
return err
|
||
|
|
}
|
||
|
|
defer func() {
|
||
|
|
// Only call os.Remove on f.Name() if we failed to rename it: otherwise,
|
||
|
|
// some other process may have created a new file with the same name after
|
||
|
|
// that.
|
||
|
|
if err != nil {
|
||
|
|
f.Close()
|
||
|
|
os.Remove(f.Name())
|
||
|
|
}
|
||
|
|
}()
|
||
|
|
|
||
|
|
if _, err := io.Copy(f, data); err != nil {
|
||
|
|
return err
|
||
|
|
}
|
||
|
|
// Sync the file before renaming it: otherwise, after a crash the reader may
|
||
|
|
// observe a 0-length file instead of the actual contents.
|
||
|
|
// See https://golang.org/issue/22397#issuecomment-380831736.
|
||
|
|
if err := f.Sync(); err != nil {
|
||
|
|
return err
|
||
|
|
}
|
||
|
|
if err := f.Close(); err != nil {
|
||
|
|
return err
|
||
|
|
}
|
||
|
|
|
||
|
|
return robustio.Rename(f.Name(), filename)
|
||
|
|
}
|
||
|
|
|
||
|
|
// tempFile creates a new temporary file with given permission bits.
|
||
|
|
func tempFile(dir, prefix string, perm os.FileMode) (f *os.File, err error) {
|
||
|
|
for i := 0; i < 10000; i++ {
|
||
|
|
name := filepath.Join(dir, prefix+strconv.Itoa(rand.Intn(1000000000))+patternSuffix)
|
||
|
|
f, err = os.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, perm)
|
||
|
|
if os.IsExist(err) {
|
||
|
|
continue
|
||
|
|
}
|
||
|
|
break
|
||
|
|
}
|
||
|
|
return
|
||
|
|
}
|
||
|
|
|
||
|
|
// ReadFile is like ioutil.ReadFile, but on Windows retries spurious errors that
|
||
|
|
// may occur if the file is concurrently replaced.
|
||
|
|
//
|
||
|
|
// Errors are classified heuristically and retries are bounded, so even this
|
||
|
|
// function may occasionally return a spurious error on Windows.
|
||
|
|
// If so, the error will likely wrap one of:
|
||
|
|
// - syscall.ERROR_ACCESS_DENIED
|
||
|
|
// - syscall.ERROR_FILE_NOT_FOUND
|
||
|
|
// - internal/syscall/windows.ERROR_SHARING_VIOLATION
|
||
|
|
func ReadFile(filename string) ([]byte, error) {
|
||
|
|
return robustio.ReadFile(filename)
|
||
|
|
}
|