97 lines
2.0 KiB
Go
97 lines
2.0 KiB
Go
|
// Package safeio provides functions to perform atomic, fsync-safe disk
|
||
|
|
// operations.
|
||
|
|
package safeio
|
||
|
|
|
||
|
|
import (
|
||
|
|
"io"
|
||
|
|
"io/ioutil"
|
||
|
|
"os"
|
||
|
|
"path/filepath"
|
||
|
|
)
|
||
|
|
|
||
|
|
// WriteToFile consumes the provided io.Reader and writes it to a temp
|
||
|
|
// file in the provided directory.
|
||
|
|
func WriteToFile(src io.Reader, path string, perm os.FileMode) (written int64, err error) {
|
||
|
|
tempName, written, err := writeToTempFile(src, path, perm)
|
||
|
|
|
||
|
|
if err == nil {
|
||
|
|
err = Rename(tempName, path)
|
||
|
|
}
|
||
|
|
|
||
|
|
return written, err
|
||
|
|
}
|
||
|
|
|
||
|
|
// writeToTempFile consumes the provided io.Reader and writes it to a
|
||
|
|
// temp file in the same directory as path.
|
||
|
|
func writeToTempFile(src io.Reader, path string, perm os.FileMode) (tempName string, written int64, err error) {
|
||
|
|
dir := filepath.Dir(path)
|
||
|
|
name := filepath.Base(path)
|
||
|
|
|
||
|
|
f, err := ioutil.TempFile(dir, name+".tmp")
|
||
|
|
if err != nil {
|
||
|
|
return "", 0, err
|
||
|
|
}
|
||
|
|
|
||
|
|
tempName = f.Name()
|
||
|
|
|
||
|
|
cleanup := func(written int64, err error) (string, int64, error) {
|
||
|
|
_ = f.Close()
|
||
|
|
_ = os.Remove(tempName)
|
||
|
|
return "", written, err
|
||
|
|
}
|
||
|
|
|
||
|
|
if err = f.Chmod(perm); err != nil {
|
||
|
|
return cleanup(0, err)
|
||
|
|
}
|
||
|
|
|
||
|
|
written, err = io.Copy(f, src)
|
||
|
|
if err != nil {
|
||
|
|
return cleanup(written, err)
|
||
|
|
}
|
||
|
|
|
||
|
|
if err := f.Sync(); err != nil {
|
||
|
|
return cleanup(written, err)
|
||
|
|
}
|
||
|
|
|
||
|
|
if err := f.Close(); err != nil {
|
||
|
|
return cleanup(written, err)
|
||
|
|
}
|
||
|
|
|
||
|
|
return tempName, written, nil
|
||
|
|
}
|
||
|
|
|
||
|
|
// Remove is just like os.Remove, except this also calls sync on the
|
||
|
|
// parent directory.
|
||
|
|
func Remove(fn string) error {
|
||
|
|
err := os.Remove(fn)
|
||
|
|
if err != nil {
|
||
|
|
return err
|
||
|
|
}
|
||
|
|
|
||
|
|
// fsync the dir
|
||
|
|
return syncParentDir(fn)
|
||
|
|
}
|
||
|
|
|
||
|
|
// Rename renames the file using os.Rename and fsyncs the NEW parent
|
||
|
|
// directory. It should only be used if both oldname and newname are in
|
||
|
|
// the same directory.
|
||
|
|
func Rename(oldname, newname string) error {
|
||
|
|
err := os.Rename(oldname, newname)
|
||
|
|
if err != nil {
|
||
|
|
return err
|
||
|
|
}
|
||
|
|
|
||
|
|
// fsync the dir
|
||
|
|
return syncParentDir(newname)
|
||
|
|
}
|
||
|
|
|
||
|
|
func syncParentDir(name string) error {
|
||
|
|
f, err := os.Open(filepath.Dir(name))
|
||
|
|
if err != nil {
|
||
|
|
return err
|
||
|
|
}
|
||
|
|
defer f.Close()
|
||
|
|
|
||
|
|
return f.Sync()
|
||
|
|
}
|