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  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18  * KIND, either express or implied.
  19  *
  20  ****************************************************************************/
  21
  22 /*
  23  * We can't use the CRC32 implementation in the firmware library as it uses a
  24  * different polynomial. The polynomial needed is 0xEDB88320L
  25  *
  26  * CRC32 implementation taken from:
  27  *
  28  * efone - Distributed internet phone system.
  29  *
  30  * (c) 1999,2000 Krzysztof Dabrowski
  31  * (c) 1999,2000 ElysiuM deeZine
  32  *
  33  * This program is free software; you can redistribute it and/or
  34  * modify it under the terms of the GNU General Public License
  35  * as published by the Free Software Foundation; either version
  36  * 2 of the License, or (at your option) any later version.
  37  *
  38  */
  39
  40 /* based on implementation by Finn Yannick Jacobs */
  41
  42 #include "crc32-mi4.h"
  43
  44 /* crc_tab[] -- this crcTable is being build by chksum_crc32GenTab().
  45  *      so make sure, you call it before using the other
  46  *      functions!
  47  */
  48 static unsigned int crc_tab[256];
  49
  50 /* chksum_crc() -- to a given block, this one calculates the
  51  *              crc32-checksum until the length is
  52  *              reached. the crc32-checksum will be
  53  *              the result.
  54  */
  55 unsigned int chksum_crc32 (unsigned char *block, unsigned int length)
  56 {
  57    register unsigned long crc;
  58    unsigned long i;
  59
  60    crc = 0;
  61    for (i = 0; i < length; i++)
  62    {
  63       crc = ((crc >> 8) & 0x00FFFFFF) ^ crc_tab[(crc ^ *block++) & 0xFF];
  64    }
  65    return (crc);
  66 }
  67
  68 /* chksum_crc32gentab() --      to a global crc_tab[256], this one will
  69  *              calculate the crcTable for crc32-checksums.
  70  *              it is generated to the polynom [..]
  71  */
  72
  73 void chksum_crc32gentab (void)
  74 {
  75    unsigned long crc, poly;
  76    int i, j;
  77
  78    poly = 0xEDB88320L;
  79    for (i = 0; i < 256; i++)
  80    {
  81       crc = i;
  82       for (j = 8; j > 0; j--)
  83       {
  84      if (crc & 1)
  85      {
  86         crc = (crc >> 1) ^ poly;
  87      }
  88      else
  89      {
  90         crc >>= 1;
  91      }
  92       }
  93       crc_tab[i] = crc;
  94    }
  95 }