firmware/common/crc32-mi4.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id: crc32.c 10464 2006-08-05 20:19:10Z miipekk $
   9  *
  10  * Copyright (C) 2007 Barry Wardell
  11  *
  12  * All files in this archive are subject to the GNU General Public License.
  13  * See the file COPYING in the source tree root for full license agreement.
  14  *
  15  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  16  * KIND, either express or implied.
  17  *
  18  ****************************************************************************/
  19
  20 /*
  21  * We can't use the CRC32 implementation in the firmware library as it uses a
  22  * different polynomial. The polynomial needed is 0xEDB88320L
  23  *
  24  * CRC32 implementation taken from:
  25  *
  26  * efone - Distributed internet phone system.
  27  *
  28  * (c) 1999,2000 Krzysztof Dabrowski
  29  * (c) 1999,2000 ElysiuM deeZine
  30  *
  31  * This program is free software; you can redistribute it and/or
  32  * modify it under the terms of the GNU General Public License
  33  * as published by the Free Software Foundation; either version
  34  * 2 of the License, or (at your option) any later version.
  35  *
  36  */
  37
  38 /* based on implementation by Finn Yannick Jacobs */
  39
  40
  41
  42 /* crc_tab[] -- this crcTable is being build by chksum_crc32GenTab().
  43  *      so make sure, you call it before using the other
  44  *      functions!
  45  */
  46 static unsigned int crc_tab[256];
  47
  48 /* chksum_crc() -- to a given block, this one calculates the
  49  *              crc32-checksum until the length is
  50  *              reached. the crc32-checksum will be
  51  *              the result.
  52  */
  53 unsigned int chksum_crc32 (unsigned char *block, unsigned int length)
  54 {
  55    register unsigned long crc;
  56    unsigned long i;
  57
  58    crc = 0;
  59    for (i = 0; i < length; i++)
  60    {
  61       crc = ((crc >> 8) & 0x00FFFFFF) ^ crc_tab[(crc ^ *block++) & 0xFF];
  62    }
  63    return (crc);
  64 }
  65
  66 /* chksum_crc32gentab() --      to a global crc_tab[256], this one will
  67  *              calculate the crcTable for crc32-checksums.
  68  *              it is generated to the polynom [..]
  69  */
  70
  71 void chksum_crc32gentab (void)
  72 {
  73    unsigned long crc, poly;
  74    int i, j;
  75
  76    poly = 0xEDB88320L;
  77    for (i = 0; i < 256; i++)
  78    {
  79       crc = i;
  80       for (j = 8; j > 0; j--)
  81       {
  82      if (crc & 1)
  83      {
  84         crc = (crc >> 1) ^ poly;
  85      }
  86      else
  87      {
  88         crc >>= 1;
  89      }
  90       }
  91       crc_tab[i] = crc;
  92    }
  93 }