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 1 /******************************************************************************
 2 *
 3 * Copyright (C) 2006, The Gentee Group. All rights reserved. 
 4 * This file is part of the Gentee open source project - http://www.gentee.com. 
 5 * 
 6 * THIS FILE IS PROVIDED UNDER THE TERMS OF THE GENTEE LICENSE ("AGREEMENT"). 
 7 * ANY USE, REPRODUCTION OR DISTRIBUTION OF THIS FILE CONSTITUTES RECIPIENTS 
 8 * ACCEPTANCE OF THE AGREEMENT.
 9 *
10 * ID: crc 18.10.06 0.0.A.
11 *
12 * Author: Alexey Krivonogov
13 *
14 * Summary: This file provides calculating CRC32.
15 *
16 ******************************************************************************/
17 
18 #include "crc.h"
19 
20 uint  _crctbl[ 256 ];
21 
22 //--------------------------------------------------------------------------
23 
24 void STDCALL crc_init( void )
25 {
26    uint  reg, polinom, i, ib;
27 
28    polinom = 0xEDB88320;
29    _crctbl[ 0 ] = 0;
30 
31    for ( i = 1; i < 256; i++ )
32    {
33       reg = 0;
34       for ( ib = i | 256; ib != 1; ib >>= 1 )
35       {
36          reg = ( reg & 1 ? (reg >> 1) ^ polinom : reg >> 1 );
37          if ( ib & 1 )
38             reg ^= polinom;
39       }
40       _crctbl[ i ] = reg;
41    }
42 }
43 
44 //--------------------------------------------------------------------------
45 // seed must be 0xFFFFFFFF in the first calling
46 
47 uint STDCALL crc( pubyte data, uint size, uint seed )
48 {
49    while ( size-- )
50       seed = _crctbl[((ushort)seed ^ ( *data++ )) & 0xFF ] ^ ( seed >> 8 );
51 
52    return seed;
53 }
54 
55 //--------------------------------------------------------------------------
56