arnesi

vector/array utilities 

(defun vector-push-extend* (vector &rest items)
  (let ((element-type (array-element-type vector)))
    (dolist (item items)[...]
      (cond
        ((typep item element-type) ;; item can be put directly into the 
         (vector-push-extend item vector))
        ((typep item `(vector ,element-type)) ;; item should be a vector
         (loop
            for i across item
            do (vector-push-extend i vector)))
        (t
         (error "Bad type for item ~S." item))))
    vector))

(defun string-from-array (array &key (start 0) (end (1- (length array))))
  "Assuming ARRAY is an array of ASCII chars encoded as bytes return
the corresponding string. Respect the C convention of null terminating[...]
strings. START and END specify the zero indexed offsets of a sub range
of ARRAY."
  ;; This is almost always the case
  (assert (<= 0 start (1- (length array)))
          (start)
          "START must be a valid offset of ARRAY.")
  (assert (<= 0 end (1- (length array)))
          (end)
          "END must be a valid offset of ARRAY.")
  (assert (<= start end)
          (start end)
          "START must be less than or equal to END.")
  (assert (every (lambda (element) (<= 0 element 255)) array)
	  (array)
	  "Some element of ~S was not > 0 and < 255" array)
  (let* ((working-array (make-array (1+ (- end start))
                                    :element-type (array-element-type array)
                                    :displaced-to array
                                    :displaced-index-offset start))
	  (length (if-bind pos (position 0 working-array)
		      pos
		      (length working-array))))
    (map-into (make-array length :element-type 'character)
	      #'code-char
	      working-array)))