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/***************************************************************************
crc32.cpp - description
-------------------
copyright : (C) 2003 by Csaba Karai
e-mail : krusader@users.sourceforge.net
web site : http://krusader.sourceforge.net
---------------------------------------------------------------------------
Description
***************************************************************************
A
db dD d8888b. db db .d8888. .d8b. d8888b. d88888b d8888b.
88 ,8P' 88 `8D 88 88 88' YP d8' `8b 88 `8D 88' 88 `8D
88,8P 88oobY' 88 88 `8bo. 88ooo88 88 88 88ooooo 88oobY'
88`8b 88`8b 88 88 `Y8b. 88~~~88 88 88 88~~~~~ 88`8b
88 `88. 88 `88. 88b d88 db 8D 88 88 88 .8D 88. 88 `88.
YP YD 88 YD ~Y8888P' `8888Y' YP YP Y8888D' Y88888P 88 YD
S o u r c e F i l e
***************************************************************************
* *
* 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. *
* *
***************************************************************************/
#include "crc32.h"
#define MASK1 0x00FFFFFF
#define MASK2 0xFFFFFFFF
#define POLYNOMIAL 0xEDB88320
bool CRC32::crc_initialized = false;
unsigned long CRC32::crc_table[ 256 ];
CRC32::CRC32( unsigned long initialValue )
{
crc_accum = initialValue;
if( !crc_initialized )
{
for( int byte = 0; byte != 256; byte++ )
{
unsigned long data = byte;
for( int i = 8; i > 0 ; --i )
data = data & 1 ? ( data >> 1 ) ^ POLYNOMIAL : data >> 1;
crc_table[ byte ] = data;
}
crc_initialized = true;
}
}
void CRC32::update( unsigned char *buffer, int bufferLen )
{
while( bufferLen-- > 0 )
crc_accum = ( (crc_accum >> 8) & MASK1 ) ^ crc_table[ (crc_accum & 0xff) ^ *buffer++ ];
}
unsigned long CRC32::result()
{
return ( ~crc_accum ) & MASK2;
}
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