wehub-resource-sync
54 lines
1.2 KiB
Go
54 lines
1.2 KiB
Go
package atomicfile
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import (
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"os"
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"path/filepath"
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)
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// atomicWriteFile replaces path with data via a temp file in the same
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// directory: the temp file is chmodded (CreateTemp creates it 0600),
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// fsynced so a crash cannot leave a truncated file behind the
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// already-journaled rename, renamed over the target, and the parent
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// directory is best-effort synced so the rename itself survives a crash.
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func Write(path string, data []byte, perm os.FileMode) error {
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dir := filepath.Dir(path)
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tmp, err := os.CreateTemp(dir, "."+filepath.Base(path)+"-*.tmp")
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if err != nil {
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return err
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}
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tmpName := tmp.Name()
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defer os.Remove(tmpName)
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if err := tmp.Chmod(perm); err != nil {
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_ = tmp.Close()
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return err
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}
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if _, err := tmp.Write(data); err != nil {
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_ = tmp.Close()
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return err
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}
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if err := tmp.Sync(); err != nil {
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_ = tmp.Close()
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return err
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}
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if err := tmp.Close(); err != nil {
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return err
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}
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if err := os.Rename(tmpName, path); err != nil {
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return err
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}
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syncDir(dir)
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return nil
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}
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// syncDir best-effort flushes directory metadata so a rename survives a
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// crash. Errors are ignored: not all platforms support syncing directories.
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func syncDir(dir string) {
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d, err := os.Open(dir)
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if err != nil {
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return
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}
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_ = d.Sync()
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_ = d.Close()
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}
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