File: compress.lisp

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cl-salza2 2.0.9-1
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;;;
;;; Copyright (c) 2007 Zachary Beane, All Rights Reserved
;;;
;;; Redistribution and use in source and binary forms, with or without
;;; modification, are permitted provided that the following conditions
;;; are met:
;;;
;;;   * Redistributions of source code must retain the above copyright
;;;     notice, this list of conditions and the following disclaimer.
;;;
;;;   * Redistributions in binary form must reproduce the above
;;;     copyright notice, this list of conditions and the following
;;;     disclaimer in the documentation and/or other materials
;;;     provided with the distribution.
;;;
;;; THIS SOFTWARE IS PROVIDED BY THE AUTHOR 'AS IS' AND ANY EXPRESSED
;;; OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
;;; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
;;; ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
;;; DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
;;; DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
;;; GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
;;; INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
;;; WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
;;; NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
;;; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;;;

(in-package #:salza2)

(defun compress (input chains start end
                 literal-fun length-fun distance-fun)
  (declare (type input-buffer input)
           (type chains-buffer chains)
           (type input-index start end)
           (type function literal-fun length-fun distance-fun)
           (optimize speed))
  (let ((p start))
    (loop
     (when (= p end)
       (return))
     (multiple-value-bind (length distance)
         (longest-match p input chains end 4)
       (declare (type (integer 0 258) length)
                (type (integer 0 32768) distance))
       (cond ((zerop length)
              (funcall literal-fun (aref input p))
              (setf p (logand (+ p 1) #xFFFF)))
             (t
              (funcall length-fun length)
              (funcall distance-fun distance)
              (setf p (logand (+ p length) #xFFFF))))))))