anchor.diff:                                    :encoding (external-format-of stream))))
       (extend-vector-output-stream-buffer octets stream))
     char)
  -
  -(defun extend-vector-output-stream-buffer (extension stream &key (start 0) (end (length extension)))
  -  (declare (optimize speed)
  -           (type vector extension))
  -  (vector-extend extension (vector-stream-vector stream) :start start :end end)
  -  (incf (vector-stream-index stream) (- end start))
  -  (values))
   
   (defmethod stream-write-sequence ((stream vector-output-stream) sequence start end &key)
     "Just calls VECTOR-PUSH-EXTEND repeatedly."
  
positive.code: 
  (declaim (inline check-if-open check-if-accepts-octets
            check-if-accepts-characters stream-accepts-characters?
            stream-accepts-octets? vector-extend))
  
  (defclass in-memory-stream (trivial-gray-stream-mixin)
    ((element-type :initform :default ; which means bivalent
  
negative.code:   (incf (vector-stream-index stream))
    byte)
  
  (defun extend-vector-output-stream-buffer (extension stream &key (start 0) (end (length extension)))
    (declare (optimize speed)
             (type vector extension))
    (vector-extend extension (vector-stream-vector stream) :start start :end end)
    (incf (vector-stream-index stream) (- end start))
    (values))
  
  (defmethod stream-write-char ((stream vector-output-stream) char)
    (declare (optimize speed))
    (check-if-open stream)
  