anchor.diff:  
   (defmethod decompress ((output vector) (state decompression-state) (input vector)
                          &key (input-start 0) input-end
  -                       (output-start 0) output-end &allow-other-keys)
  +                       (output-start 0) output-end)
     (%decompress/vector-vector output state input
                                (decompress-fun-for-state state)
                                input-start (or input-end (length input))
  
positive.code:               (return-from %decompress/stream-vector output))))))
  
  (defmethod decompress ((output stream) (state decompression-state) (input vector)
                         &key (input-start 0) input-end &allow-other-keys)
    (%decompress/stream-vector output state input
                               (decompress-fun-for-state state)
                               input-start (or input-end (length input))))
  
negative.code:                    (return-from %decompress/null-stream (maybe-subseq output output-start))))))))))
  
  (defmethod decompress ((output null) (state decompression-state) (input stream)
                         &key buffer-size)
    (%decompress/null-stream state input
                             (decompress-fun-for-state state)
                             (or buffer-size +default-buffer-size+)))
  