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/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id: crc32.c 10464 2006-08-05 20:19:10Z miipekk $
*
* Copyright (C) 2007 Barry Wardell
*
* All files in this archive are subject to the GNU General Public License.
* See the file COPYING in the source tree root for full license agreement.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
/*
* We can't use the CRC32 implementation in the firmware library as it uses a
* different polynomial. The polynomial needed is 0xEDB88320L
*
* CRC32 implementation taken from:
*
* efone - Distributed internet phone system.
*
* (c) 1999,2000 Krzysztof Dabrowski
* (c) 1999,2000 ElysiuM deeZine
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
*/
/* based on implementation by Finn Yannick Jacobs */
/* crc_tab[] -- this crcTable is being build by chksum_crc32GenTab().
* so make sure, you call it before using the other
* functions!
*/
static unsigned int crc_tab[256];
/* chksum_crc() -- to a given block, this one calculates the
* crc32-checksum until the length is
* reached. the crc32-checksum will be
* the result.
*/
unsigned int chksum_crc32 (unsigned char *block, unsigned int length)
{
register unsigned long crc;
unsigned long i;
crc = 0;
for (i = 0; i < length; i++)
{
crc = ((crc >> 8) & 0x00FFFFFF) ^ crc_tab[(crc ^ *block++) & 0xFF];
}
return (crc);
}
/* chksum_crc32gentab() -- to a global crc_tab[256], this one will
* calculate the crcTable for crc32-checksums.
* it is generated to the polynom [..]
*/
void chksum_crc32gentab (void)
{
unsigned long crc, poly;
int i, j;
poly = 0xEDB88320L;
for (i = 0; i < 256; i++)
{
crc = i;
for (j = 8; j > 0; j--)
{
if (crc & 1)
{
crc = (crc >> 1) ^ poly;
}
else
{
crc >>= 1;
}
}
crc_tab[i] = crc;
}
}
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