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52 lines
1.4 KiB
Go
52 lines
1.4 KiB
Go
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// +build plan9 windows,!go1.5
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// os.Rename on Windows before Go 1.5 and Plan 9 will not overwrite existing
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// files, thus we cannot guarantee atomic saving of file by doing rename.
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// We will have to do some voodoo to minimize data loss on those systems.
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package safefile
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import (
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"os"
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"path/filepath"
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)
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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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// If newname exists ("original"), we will try renaming it to a
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// new temporary name, then renaming oldname to the newname,
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// and deleting the renamed original. If system crashes between
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// renaming and deleting, the original file will still be available
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// under the temporary name, so users can manually recover data.
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// (No automatic recovery is possible because after crash the
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// temporary name is not known.)
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var origtmp string
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for {
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origtmp, err = makeTempName(newname, filepath.Base(newname))
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if err != nil {
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return err
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}
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_, err = os.Stat(origtmp)
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if err == nil {
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continue // most likely will never happen
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}
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break
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}
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err = os.Rename(newname, origtmp)
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if err != nil {
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return err
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}
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err = os.Rename(oldname, newname)
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if err != nil {
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// Rename still fails, try to revert original rename,
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// ignoring errors.
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os.Rename(origtmp, newname)
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return err
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}
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// Rename succeeded, now delete original file.
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os.Remove(origtmp)
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}
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return nil
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}
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