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