code: func Diff(old, new io.Reader, patch io.Writer) error {
  	obuf, err := ioutil.ReadAll(old)
  	if err != nil {
  		return err
  	}
  
  	nbuf, err := ioutil.ReadAll(new)
  	if err != nil {
  		return err
  	}
  
  	pbuf, err := diffBytes(obuf, nbuf)
  	if err != nil {
  		return err
  	}
  
  	_, err = patch.Write(pbuf)
  	return err
  }
docs: // Diff computes the difference between old and new, according to the bsdiff
  // algorithm, and writes the result to patch.