project64/Source/Glide64/CRC.cpp

/*
* Glide64 - Glide video plugin for Nintendo 64 emulators.
* Copyright (c) 2002  Dave2001
* Copyright (c) 2003-2009  Sergey 'Gonetz' Lipski
*
* 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
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

//****************************************************************
//
// Glide64 - Glide Plugin for Nintendo 64 emulators
// Project started on December 29th, 2001
//
// Authors:
// Dave2001, original author, founded the project in 2001, left it in 2002
// Gugaman, joined the project in 2002, left it in 2002
// Sergey 'Gonetz' Lipski, joined the project in 2002, main author since fall of 2002
// Hiroshi 'KoolSmoky' Morii, joined the project in 2007
//
//****************************************************************
//
// To modify Glide64:
// * 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.
// * 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.
//
//****************************************************************
//
// CRC32 calculation functions
//
// Created by Gonetz, 2004
//
//****************************************************************
//*
#define CRC32_POLYNOMIAL     0x04C11DB7

unsigned int CRCTable[256];

unsigned int Reflect(unsigned int ref, char ch)
{
    unsigned int value = 0;

    // Swap bit 0 for bit 7
    // bit 1 for bit 6, etc.
    for (char i = 1; i < (ch + 1); i++)
    {
        if (ref & 1)
            value |= 1 << (ch - i);
        ref >>= 1;
    }
    return value;
}

void CRC_BuildTable()
{
    unsigned int crc;

    for (unsigned i = 0; i <= 255; i++)
    {
        crc = Reflect(i, 8) << 24;
        for (unsigned j = 0; j < 8; j++)
            crc = (crc << 1) ^ (crc & (1 << 31) ? CRC32_POLYNOMIAL : 0);

        CRCTable[i] = Reflect(crc, 32);
    }
}
//*/
//*
unsigned int CRC32(unsigned int crc, void *buffer, unsigned int count)
{
    unsigned int orig = crc;
    unsigned char * p = reinterpret_cast<unsigned char*>(buffer);
    while (count--)
        crc = (crc >> 8) ^ CRCTable[(crc & 0xFF) ^ *p++];
    return crc ^ orig;
}
//*/

/*
uint32_t CRC_Calculate( uint32_t crc, void *buffer, uint32_t count )
{
uint32_t Crc32=crc;
__asm {
mov	esi, buffer
mov	ecx, count
mov	edx, crc
xor eax, eax

loop1:
inc	esi
mov	al, dl
xor	al, byte ptr [esi]
shr	edx, 8
mov	ebx, [CRCTable+eax*4]
xor	edx, ebx

loop loop1

xor	Crc32, edx
}
return Crc32;
}
*/

/*
unsigned int CRC_Calculate( unsigned int crc, void *buffer, unsigned int count )
{
unsigned int Crc32=crc;
__asm {
mov	esi, buffer
mov	edx, count
add	edx, esi
mov	ecx, crc

loop1:
mov	bl, byte ptr [esi]
movzx	eax, cl
inc	esi
xor	al, bl
shr	ecx, 8
mov	ebx, [CRCTable+eax*4]
xor	ecx, ebx

cmp	edx, esi
jne	loop1

xor	Crc32, ecx
}
return Crc32;
}
//*/