76 lines
1.5 KiB
Go
76 lines
1.5 KiB
Go
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package ioutils
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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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// NewAtomicFileWriter returns WriteCloser so that writing to it writes to a
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// temporary file and closing it atomically changes the temporary file to
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// destination path. Writing and closing concurrently is not allowed.
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func NewAtomicFileWriter(filename string, perm os.FileMode) (io.WriteCloser, error) {
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f, err := ioutil.TempFile(filepath.Dir(filename), ".tmp-"+filepath.Base(filename))
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if err != nil {
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return nil, err
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}
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abspath, err := filepath.Abs(filename)
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if err != nil {
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return nil, err
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}
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return &atomicFileWriter{
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f: f,
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fn: abspath,
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}, nil
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}
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// AtomicWriteFile atomically writes data to a file named by filename.
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func AtomicWriteFile(filename string, data []byte, perm os.FileMode) error {
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f, err := NewAtomicFileWriter(filename, perm)
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if err != nil {
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return err
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}
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n, err := f.Write(data)
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if err == nil && n < len(data) {
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err = io.ErrShortWrite
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}
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if err1 := f.Close(); err == nil {
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err = err1
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}
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return err
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}
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type atomicFileWriter struct {
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f *os.File
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fn string
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writeErr error
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}
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func (w *atomicFileWriter) Write(dt []byte) (int, error) {
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n, err := w.f.Write(dt)
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if err != nil {
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w.writeErr = err
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}
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return n, err
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}
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func (w *atomicFileWriter) Close() (retErr error) {
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defer func() {
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if retErr != nil {
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os.Remove(w.f.Name())
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}
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}()
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if err := w.f.Sync(); err != nil {
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w.f.Close()
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return err
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}
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if err := w.f.Close(); err != nil {
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return err
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}
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if w.writeErr == nil {
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return os.Rename(w.f.Name(), w.fn)
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}
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return nil
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}
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