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5b20cba50a
we don't want external software to include internal details like mlog. slog.Logger is/will be the standard. we still have mlog for its helper functions, and its handler that logs in concise logfmt used by mox. packages that are not meant for reuse still pass around mlog.Log for convenience. we use golang.org/x/exp/slog because we also support the previous Go toolchain version. with the next Go release, we'll switch to the builtin slog.
73 lines
2 KiB
Go
73 lines
2 KiB
Go
package moxio
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import (
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"fmt"
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"io"
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"os"
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"golang.org/x/exp/slog"
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"github.com/mjl-/mox/mlog"
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)
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// LinkOrCopy attempts to make a hardlink dst. If that fails, it will try to do a
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// regular file copy. If srcReaderOpt is not nil, it will be used for reading. If
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// sync is true and the file is copied, Sync is called on the file after writing to
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// ensure the file is written on disk. Callers should also sync the directory of
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// the destination file, but may want to do that after linking/copying multiple
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// files. If dst was created and an error occurred, it is removed.
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func LinkOrCopy(log mlog.Log, dst, src string, srcReaderOpt io.Reader, sync bool) (rerr error) {
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// Try hardlink first.
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err := os.Link(src, dst)
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if err == nil {
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return nil
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} else if os.IsNotExist(err) {
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// No point in trying with regular copy, we would fail again. Either src doesn't
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// exist or dst directory doesn't exist.
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return err
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}
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// File system may not support hardlinks, or link could be crossing file systems.
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// Do a regular file copy.
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if srcReaderOpt == nil {
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sf, err := os.Open(src)
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if err != nil {
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return fmt.Errorf("open source file: %w", err)
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}
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defer func() {
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err := sf.Close()
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log.Check(err, "closing copied source file")
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}()
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srcReaderOpt = sf
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}
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df, err := os.OpenFile(dst, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0660)
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if err != nil {
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return fmt.Errorf("create destination: %w", err)
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}
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defer func() {
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if df != nil {
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err := df.Close()
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log.Check(err, "closing partial destination file")
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err = os.Remove(dst)
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log.Check(err, "removing partial destination file", slog.String("path", dst))
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}
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}()
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if _, err := io.Copy(df, srcReaderOpt); err != nil {
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return fmt.Errorf("copy: %w", err)
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}
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if sync {
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if err := df.Sync(); err != nil {
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return fmt.Errorf("sync destination: %w", err)
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}
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}
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err = df.Close()
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df = nil
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if err != nil {
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err := os.Remove(dst)
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log.Check(err, "removing partial destination file", slog.String("path", dst))
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return err
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}
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return nil
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}
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