CRC.cpp

   1 /*
   2 *       Glide64 - Glide video plugin for Nintendo 64 emulators.
   3 *       Copyright (c) 2002  Dave2001
   4 *
   5 *       This program is free software; you can redistribute it and/or modify
   6 *       it under the terms of the GNU General Public License as published by
   7 *       the Free Software Foundation; either version 2 of the License, or
   8 *       any later version.
   9 *
  10 *       This program is distributed in the hope that it will be useful,
  11 *       but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 *       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 *       GNU General Public License for more details.
  14 *
  15 *       You should have received a copy of the GNU General Public License
  16 *       along with this program; if not, write to the Free Software
  17 *       Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18 */
  19
  20 //****************************************************************
  21 //
  22 // Glide64 - Glide Plugin for Nintendo 64 emulators (tested mostly with Project64)
  23 // Project started on December 29th, 2001
  24 //
  25 // To modify Glide64:
  26 // * Write your name and (optional)email, commented by your work, so I know who did it, and so that you can find which parts you modified when it comes time to send it to me.
  27 // * Do NOT send me the whole project or file that you modified.  Take out your modified code sections, and tell me where to put them.  If people sent the whole thing, I would have many different versions, but no idea how to combine them all.
  28 //
  29 // Official Glide64 development channel: #Glide64 on EFnet
  30 //
  31 // Original author: Dave2001 (Dave2999@hotmail.com)
  32 // Other authors: Gonetz, Gugaman
  33 //
  34 //****************************************************************
  35 //
  36 // CRC32 calculation functions
  37 //
  38 // Created by Gonetz, 2004
  39 //
  40 //****************************************************************
  41
  42 #include "CRC.h"
  43
  44 #define CRC32_POLYNOMIAL     0x04C11DB7
  45
  46 unsigned int CRCTable[ 256 ];
  47
  48 unsigned int Reflect( unsigned long ref, char ch )
  49 {
  50      unsigned int value = 0;
  51
  52      // Swap bit 0 for bit 7
  53      // bit 1 for bit 6, etc.
  54      for (char i = 1; i < (ch + 1); i++)
  55      {
  56           if(ref & 1)
  57                value |= 1 << (ch - i);
  58           ref >>= 1;
  59      }
  60      return value;
  61 }
  62
  63 void CRC_BuildTable()
  64 {
  65     unsigned int crc;
  66
  67     for (unsigned i = 0; i <= 255; i++)
  68         {
  69         crc = Reflect( i, 8 ) << 24;
  70         for (unsigned j = 0; j < 8; j++)
  71                         crc = (crc << 1) ^ (crc & (1 << 31) ? CRC32_POLYNOMIAL : 0);
  72
  73         CRCTable[i] = Reflect( crc, 32 );
  74     }
  75 }
  76
  77 /*
  78 DWORD CRC_Calculate( DWORD crc, void *buffer, DWORD count )
  79 {
  80     BYTE *p;
  81         DWORD orig = crc;
  82
  83     p = (BYTE*) buffer;
  84     while (count--)
  85                 crc = (crc >> 8) ^ CRCTable[(crc & 0xFF) ^ *p++];
  86
  87     return crc ^ orig;
  88 }
  89 //*/
  90
  91 /*
  92 DWORD CRC_Calculate( DWORD crc, void *buffer, DWORD count )
  93 {
  94   DWORD Crc32=crc;
  95   __asm {
  96                         mov     esi, buffer
  97                         mov     ecx, count
  98                         mov     edx, crc
  99                         xor eax, eax
 100
 101 loop1:
 102                         inc     esi
 103                         mov     al, dl
 104                         xor     al, byte ptr [esi]
 105                         shr     edx, 8
 106                         mov     ebx, [CRCTable+eax*4]
 107                         xor     edx, ebx
 108
 109                         loop loop1
 110
 111                         xor     Crc32, edx
 112    }
 113    return Crc32;
 114 }
 115 */
 116
 117 /*
 118 inline DWORD CRC_Calculate( DWORD crc, void *buffer, DWORD count )
 119 {
 120   DWORD Crc32=crc;
 121   __asm {
 122                         mov     esi, buffer
 123                         mov     edx, count
 124                         add     edx, esi
 125                         mov     ecx, crc
 126
 127 loop1:
 128                         mov     bl, byte ptr [esi]
 129                         movzx   eax, cl
 130                         inc     esi
 131                         xor     al, bl
 132                         shr     ecx, 8
 133                         mov     ebx, [CRCTable+eax*4]
 134                         xor     ecx, ebx
 135
 136                         cmp     edx, esi
 137                         jne     loop1
 138
 139                         xor     Crc32, ecx
 140    }
 141    return Crc32;
 142 }
 143 //*/