crc32.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 (defun crc32-table ()
  32   (let ((table (make-array 512 :element-type '(unsigned-byte 16))))
  33     (dotimes (n 256 table)
  34       (let ((c n))
  35         (declare (type (unsigned-byte 32) c))
  36         (dotimes (k 8)
  37           (if (logbitp 0 c)
  38               (setf c (logxor #xEDB88320 (ash c -1)))
  39               (setf c (ash c -1)))
  40           (setf (aref table (ash n 1)) (ldb (byte 16 16) c)
  41                 (aref table (1+ (ash n 1))) (ldb (byte 16 0) c)))))))
  42
  43 (defvar *crc32-table* (crc32-table))
  44
  45 (defun crc32 (high low buf start count)
  46   (declare (type (unsigned-byte 16) high low)
  47            (type array-index start count)
  48            (type octet-vector buf)
  49            (optimize speed))
  50   (let ((i start)
  51         (table *crc32-table*))
  52     (declare (type array-index i)
  53              (type (simple-array (unsigned-byte 16) (*)) table))
  54     (dotimes (j count (values high low))
  55       (let ((index (logxor (logand low #xFF) (aref buf i))))
  56         (declare (type (integer 0 255) index))
  57         (let ((high-index (ash index 1))
  58               (low-index (1+ (ash index 1))))
  59           (declare (type (integer 0 511) high-index low-index))
  60           (let ((t-high (aref table high-index))
  61                 (t-low (aref table low-index)))
  62             (declare (type (unsigned-byte 16) t-high t-low))
  63             (incf i)
  64             (setf low (logxor (ash (logand high #xFF) 8)
  65                               (ash low -8)
  66                               t-low))
  67             (setf high (logxor (ash high -8) t-high))))))))
  68
  69 ;;; Class interface
  70
  71 (defclass crc32-checksum (checksum)
  72   ((low
  73     :initarg :low
  74     :accessor low)
  75    (high
  76     :initarg :high
  77     :accessor high))
  78   (:default-initargs
  79    :low #xFFFF
  80    :high #xFFFF))
  81
  82 (defmethod update ((checksum crc32-checksum) input start count)
  83   (setf (values (high checksum)
  84                 (low checksum))
  85         (crc32 (high checksum) (low checksum)
  86                input start count)))
  87
  88 (defmethod result ((checksum crc32-checksum))
  89   (+ (ash (logxor (high checksum) #xFFFF) 16)
  90      (logxor (low checksum) #xFFFF)))
  91
  92 (defmethod result-octets ((checksum crc32-checksum))
  93   (ub32-octets (result checksum)))
  94
  95 (defmethod reset ((checksum crc32-checksum))
  96   (setf (low checksum) #xFFFF
  97         (high checksum) #xFFFF))