mirror of
https://github.com/genuinetools/reg.git
synced 2024-08-21 14:20:23 -04:00
163 lines
3.8 KiB
Go
163 lines
3.8 KiB
Go
package ioutils // import "github.com/docker/docker/pkg/ioutils"
|
|
|
|
import (
|
|
"io"
|
|
"io/ioutil"
|
|
"os"
|
|
"path/filepath"
|
|
)
|
|
|
|
// NewAtomicFileWriter returns WriteCloser so that writing to it writes to a
|
|
// temporary file and closing it atomically changes the temporary file to
|
|
// destination path. Writing and closing concurrently is not allowed.
|
|
func NewAtomicFileWriter(filename string, perm os.FileMode) (io.WriteCloser, error) {
|
|
f, err := ioutil.TempFile(filepath.Dir(filename), ".tmp-"+filepath.Base(filename))
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
abspath, err := filepath.Abs(filename)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
return &atomicFileWriter{
|
|
f: f,
|
|
fn: abspath,
|
|
perm: perm,
|
|
}, nil
|
|
}
|
|
|
|
// AtomicWriteFile atomically writes data to a file named by filename.
|
|
func AtomicWriteFile(filename string, data []byte, perm os.FileMode) error {
|
|
f, err := NewAtomicFileWriter(filename, perm)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
n, err := f.Write(data)
|
|
if err == nil && n < len(data) {
|
|
err = io.ErrShortWrite
|
|
f.(*atomicFileWriter).writeErr = err
|
|
}
|
|
if err1 := f.Close(); err == nil {
|
|
err = err1
|
|
}
|
|
return err
|
|
}
|
|
|
|
type atomicFileWriter struct {
|
|
f *os.File
|
|
fn string
|
|
writeErr error
|
|
perm os.FileMode
|
|
}
|
|
|
|
func (w *atomicFileWriter) Write(dt []byte) (int, error) {
|
|
n, err := w.f.Write(dt)
|
|
if err != nil {
|
|
w.writeErr = err
|
|
}
|
|
return n, err
|
|
}
|
|
|
|
func (w *atomicFileWriter) Close() (retErr error) {
|
|
defer func() {
|
|
if retErr != nil || w.writeErr != nil {
|
|
os.Remove(w.f.Name())
|
|
}
|
|
}()
|
|
if err := w.f.Sync(); err != nil {
|
|
w.f.Close()
|
|
return err
|
|
}
|
|
if err := w.f.Close(); err != nil {
|
|
return err
|
|
}
|
|
if err := os.Chmod(w.f.Name(), w.perm); err != nil {
|
|
return err
|
|
}
|
|
if w.writeErr == nil {
|
|
return os.Rename(w.f.Name(), w.fn)
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// AtomicWriteSet is used to atomically write a set
|
|
// of files and ensure they are visible at the same time.
|
|
// Must be committed to a new directory.
|
|
type AtomicWriteSet struct {
|
|
root string
|
|
}
|
|
|
|
// NewAtomicWriteSet creates a new atomic write set to
|
|
// atomically create a set of files. The given directory
|
|
// is used as the base directory for storing files before
|
|
// commit. If no temporary directory is given the system
|
|
// default is used.
|
|
func NewAtomicWriteSet(tmpDir string) (*AtomicWriteSet, error) {
|
|
td, err := ioutil.TempDir(tmpDir, "write-set-")
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
return &AtomicWriteSet{
|
|
root: td,
|
|
}, nil
|
|
}
|
|
|
|
// WriteFile writes a file to the set, guaranteeing the file
|
|
// has been synced.
|
|
func (ws *AtomicWriteSet) WriteFile(filename string, data []byte, perm os.FileMode) error {
|
|
f, err := ws.FileWriter(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
n, err := f.Write(data)
|
|
if err == nil && n < len(data) {
|
|
err = io.ErrShortWrite
|
|
}
|
|
if err1 := f.Close(); err == nil {
|
|
err = err1
|
|
}
|
|
return err
|
|
}
|
|
|
|
type syncFileCloser struct {
|
|
*os.File
|
|
}
|
|
|
|
func (w syncFileCloser) Close() error {
|
|
err := w.File.Sync()
|
|
if err1 := w.File.Close(); err == nil {
|
|
err = err1
|
|
}
|
|
return err
|
|
}
|
|
|
|
// FileWriter opens a file writer inside the set. The file
|
|
// should be synced and closed before calling commit.
|
|
func (ws *AtomicWriteSet) FileWriter(name string, flag int, perm os.FileMode) (io.WriteCloser, error) {
|
|
f, err := os.OpenFile(filepath.Join(ws.root, name), flag, perm)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
return syncFileCloser{f}, nil
|
|
}
|
|
|
|
// Cancel cancels the set and removes all temporary data
|
|
// created in the set.
|
|
func (ws *AtomicWriteSet) Cancel() error {
|
|
return os.RemoveAll(ws.root)
|
|
}
|
|
|
|
// Commit moves all created files to the target directory. The
|
|
// target directory must not exist and the parent of the target
|
|
// directory must exist.
|
|
func (ws *AtomicWriteSet) Commit(target string) error {
|
|
return os.Rename(ws.root, target)
|
|
}
|
|
|
|
// String returns the location the set is writing to.
|
|
func (ws *AtomicWriteSet) String() string {
|
|
return ws.root
|
|
}
|