bzip2.go
func newBzip2Writer(w io.Writer) (wc io.WriteCloser, err error) {
	var bw bzip2Writer
	bw.c = exec.Command("bzip2", "-c")
	bw.c.Stdout = w

	if bw.w, err = bw.c.StdinPipe(); err != nil {
		return nil, err
	}

	if err = bw.c.Start(); err != nil {
		return nil, err
	}

	return bw, nil
}
func newBzip2Writer(w io.Writer) (wc io.WriteCloser, err error) {
	var bw bzip2Writer
	bw.c = exec.Command("bzip2", "-c")
	bw.c.Stdout = w

	if bw.w, err = bw.c.StdinPipe(); err != nil {
		return nil, err
	}

	if err = bw.c.Start(); err != nil {
		return nil, err
	}

	return bw, nil
}
// Package compress/bzip2 implements only decompression,
// so we'll fake it by running bzip2 in another process.