forked from TrueCloudLab/restic
78 lines
2.1 KiB
Go
78 lines
2.1 KiB
Go
package fs
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import (
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"io"
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"os/exec"
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"github.com/restic/restic/internal/errors"
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)
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// CommandReader wraps an exec.Cmd and its standard output to provide an
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// io.ReadCloser that waits for the command to terminate on Close(), reporting
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// any error in the command.Wait() function back to the Close() caller.
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type CommandReader struct {
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cmd *exec.Cmd
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stdout io.ReadCloser
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// We should call exec.Wait() once. waitHandled is taking care of storing
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// whether we already called that function in Read() to avoid calling it
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// again in Close().
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waitHandled bool
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// alreadyClosedReadErr is the error that we should return if we try to
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// read the pipe again after closing. This works around a Read() call that
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// is issued after a previous Read() with `io.EOF` (but some bytes were
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// read in the past).
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alreadyClosedReadErr error
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}
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func NewCommandReader(cmd *exec.Cmd, stdout io.ReadCloser) *CommandReader {
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return &CommandReader{
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cmd: cmd,
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stdout: stdout,
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}
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}
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// Read populate the array with data from the process stdout.
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func (fp *CommandReader) Read(p []byte) (int, error) {
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if fp.alreadyClosedReadErr != nil {
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return 0, fp.alreadyClosedReadErr
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}
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b, err := fp.stdout.Read(p)
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// If the error is io.EOF, the program terminated. We need to check the
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// exit code here because, if the program terminated with no output, the
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// error in `Close()` is ignored.
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if errors.Is(err, io.EOF) {
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fp.waitHandled = true
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// check if the command terminated successfully, If not return the error.
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if errw := fp.wait(); errw != nil {
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err = errw
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}
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}
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fp.alreadyClosedReadErr = err
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return b, err
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}
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func (fp *CommandReader) wait() error {
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err := fp.cmd.Wait()
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if err != nil {
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// If we have information about the exit code, let's use it in the
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// error message. Otherwise, send the error message along.
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// In any case, use a fatal error to abort the snapshot.
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var err2 *exec.ExitError
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if errors.As(err, &err2) {
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return errors.Fatalf("command terminated with exit code %d", err2.ExitCode())
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}
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return errors.Fatal(err.Error())
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}
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return nil
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}
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func (fp *CommandReader) Close() error {
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if fp.waitHandled {
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return nil
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}
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return fp.wait()
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}
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