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70 lines
2.5 KiB
70 lines
2.5 KiB
/***************************************************************************
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crc32.cpp - description
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-------------------
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copyright : (C) 2003 by Csaba Karai
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e-mail : krusader@users.sourceforge.net
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web site : http://krusader.sourceforge.net
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---------------------------------------------------------------------------
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Description
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***************************************************************************
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A
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db dD d8888b. db db .d8888. .d8b. d8888b. d88888b d8888b.
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88 ,8P' 88 `8D 88 88 88' YP d8' `8b 88 `8D 88' 88 `8D
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88,8P 88oobY' 88 88 `8bo. 88ooo88 88 88 88ooooo 88oobY'
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88`8b 88`8b 88 88 `Y8b. 88~~~88 88 88 88~~~~~ 88`8b
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88 `88. 88 `88. 88b d88 db 8D 88 88 88 .8D 88. 88 `88.
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YP YD 88 YD ~Y8888P' `8888Y' YP YP Y8888D' Y88888P 88 YD
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S o u r c e F i l e
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***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************/
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#include "crc32.h"
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#define MASK1 0x00FFFFFF
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#define MASK2 0xFFFFFFFF
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#define POLYNOMIAL 0xEDB88320
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bool CRC32::crc_initialized = false;
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unsigned long CRC32::crc_table[ 256 ];
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CRC32::CRC32( unsigned long initialValue )
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{
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crc_accum = initialValue;
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if( !crc_initialized )
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{
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for( int byte = 0; byte != 256; byte++ )
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{
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unsigned long data = byte;
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for( int i = 8; i > 0 ; --i )
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data = data & 1 ? ( data >> 1 ) ^ POLYNOMIAL : data >> 1;
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crc_table[ byte ] = data;
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}
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crc_initialized = true;
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}
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}
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void CRC32::update( unsigned char *buffer, int bufferLen )
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{
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while( bufferLen-- > 0 )
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crc_accum = ( (crc_accum >> 8) & MASK1 ) ^ crc_table[ (crc_accum & 0xff) ^ *buffer++ ];
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}
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unsigned long CRC32::result()
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{
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return ( ~crc_accum ) & MASK2;
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}
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