adler32.lisp

   1 ;;;
   2 ;;; Copyright (c) 2007 Zachary Beane, All Rights Reserved
   3 ;;;
   4 ;;; Redistribution and use in source and binary forms, with or without
   5 ;;; modification, are permitted provided that the following conditions
   6 ;;; are met:
   7 ;;;
   8 ;;;   * Redistributions of source code must retain the above copyright
   9 ;;;     notice, this list of conditions and the following disclaimer.
  10 ;;;
  11 ;;;   * Redistributions in binary form must reproduce the above
  12 ;;;     copyright notice, this list of conditions and the following
  13 ;;;     disclaimer in the documentation and/or other materials
  14 ;;;     provided with the distribution.
  15 ;;;
  16 ;;; THIS SOFTWARE IS PROVIDED BY THE AUTHOR 'AS IS' AND ANY EXPRESSED
  17 ;;; OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  18 ;;; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19 ;;; ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
  20 ;;; DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21 ;;; DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  22 ;;; GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  23 ;;; INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  24 ;;; WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  25 ;;; NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  26 ;;; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27 ;;;
  28
  29 (in-package #:salza2)
  30
  31 (defconstant +adler32-base+ 65521)
  32
  33 (defun adler32-update (adler-high adler-low buf start count)
  34   (declare (type array-index start count)
  35            (type (unsigned-byte 16) adler-high adler-low)
  36            (type octet-vector buf)
  37            (optimize speed))
  38   (cond ((zerop count)
  39          (values adler-high adler-low))
  40         (t
  41          (let ((length count)
  42                (i 0)
  43                (k 0)
  44                (s1 adler-low)
  45                (s2 adler-high))
  46            (declare (type (integer 0 32658) length)
  47                     (type (integer 0 16) i k)
  48                     (type (integer 0 65536) s1 s2))
  49            (tagbody
  50             loop
  51               (setf k (min length 16))
  52               (decf length k)
  53             sum
  54               (setf s1 (+ (aref buf (logand #xFFFF (+ start i))) s1))
  55               (setf s2 (+ s1 s2))
  56               (decf k)
  57               (incf i)
  58               (unless (zerop k)
  59                 (go sum))
  60               (setf s1 (mod s1 +adler32-base+))
  61               (setf s2 (mod s2 +adler32-base+))
  62               (unless (zerop length)
  63                 (go loop)))
  64            (values s2 s1)))))
  65
  66 ;;; Class interface
  67
  68 (defclass adler32-checksum (checksum)
  69   ((high
  70     :initarg :high
  71     :accessor high)
  72    (low
  73     :initarg :low
  74     :accessor low))
  75   (:default-initargs
  76    :high 0
  77    :low 1))
  78
  79 (defmethod result ((checksum adler32-checksum))
  80   (+ (ash (high checksum) 16)
  81      (low checksum)))
  82
  83 (defmethod result-octets ((checksum adler32-checksum))
  84   (ub32-octets (result checksum)))
  85
  86 (defmethod update ((checksum adler32-checksum) buffer start count)
  87   (setf (values (high checksum)
  88                 (low checksum))
  89         (adler32-update (high checksum)
  90                         (low checksum)
  91                         buffer
  92                         start
  93                         count)))
  94
  95 (defmethod reset ((checksum adler32-checksum))
  96   (setf (high checksum) 0
  97         (low checksum) 1))