| 1 | /****************************************************************************** |
| 2 | * Arachnoid Graphics Plugin for Mupen64Plus |
| 3 | * http://bitbucket.org/wahrhaft/mupen64plus-video-arachnoid/ |
| 4 | * |
| 5 | * Copyright (C) 2007 Kristofer Karlsson, Rickard Niklasson |
| 6 | * |
| 7 | * This program is free software; you can redistribute it and/or |
| 8 | * modify it under the terms of the GNU General Public License |
| 9 | * as published by the Free Software Foundation; either version 2 |
| 10 | * of the License, or (at your option) any later version. |
| 11 | * |
| 12 | * This program is distributed in the hope that it will be useful, |
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | * GNU General Public License for more details. |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License |
| 18 | * along with this program; if not, write to the Free Software |
| 19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
| 20 | *****************************************************************************/ |
| 21 | |
| 22 | #include "CRCCalculator2.h" |
| 23 | |
| 24 | #define CRC32_POLYNOMIAL 0xedb88320 //0x04C11DB7 |
| 25 | typedef unsigned char byte; |
| 26 | |
| 27 | //----------------------------------------------------------------------------- |
| 28 | // Static Variabels |
| 29 | //----------------------------------------------------------------------------- |
| 30 | unsigned int CRCCalculator2::m_crcTable[256] = {0}; |
| 31 | |
| 32 | //----------------------------------------------------------------------------- |
| 33 | //! Constructor |
| 34 | //----------------------------------------------------------------------------- |
| 35 | CRCCalculator2::CRCCalculator2() |
| 36 | { |
| 37 | static bool hashTableInitialized = false; |
| 38 | |
| 39 | //Build hash table |
| 40 | //http://www.gamedev.net/reference/articles/article1941.asp |
| 41 | if ( !hashTableInitialized ) |
| 42 | { |
| 43 | unsigned int crc; |
| 44 | |
| 45 | //For each value |
| 46 | for (int i=0; i<256; i++) |
| 47 | { |
| 48 | crc = _reflect( i, 8 ) << 24; |
| 49 | |
| 50 | for (int j = 0; j < 8; j++) |
| 51 | { |
| 52 | crc = (crc << 1) ^ (crc & (1 << 31) ? CRC32_POLYNOMIAL : 0); |
| 53 | } |
| 54 | |
| 55 | m_crcTable[i] = _reflect( crc, 32 ); |
| 56 | } |
| 57 | |
| 58 | hashTableInitialized = true; |
| 59 | } |
| 60 | } |
| 61 | |
| 62 | //----------------------------------------------------------------------------- |
| 63 | // CalculateCRC |
| 64 | //----------------------------------------------------------------------------- |
| 65 | unsigned int CRCCalculator2::calcCRC(unsigned int crc, void *buffer, unsigned int count) |
| 66 | { |
| 67 | byte* p = (byte*) buffer; |
| 68 | unsigned int orig = crc; |
| 69 | |
| 70 | p = (byte*) buffer; |
| 71 | while (count--) |
| 72 | { |
| 73 | crc = (crc >> 8) ^ m_crcTable[(crc & 0xFF) ^ *p++]; |
| 74 | } |
| 75 | |
| 76 | return crc ^ orig; |
| 77 | } |
| 78 | |
| 79 | //----------------------------------------------------------------------------- |
| 80 | // CalculatePaletteCRC |
| 81 | //----------------------------------------------------------------------------- |
| 82 | unsigned int CRCCalculator2::calcPaletteCRC(unsigned int crc, void *buffer, unsigned int count) |
| 83 | { |
| 84 | byte *p; |
| 85 | unsigned int orig = crc; |
| 86 | |
| 87 | p = (byte*) buffer; |
| 88 | while (count--) |
| 89 | { |
| 90 | crc = (crc >> 8) ^ m_crcTable[(crc & 0xFF) ^ *p++]; |
| 91 | crc = (crc >> 8) ^ m_crcTable[(crc & 0xFF) ^ *p++]; |
| 92 | |
| 93 | p += 6; |
| 94 | } |
| 95 | |
| 96 | return crc ^ orig; |
| 97 | } |
| 98 | |
| 99 | //***************************************************************************** |
| 100 | // Private Functions |
| 101 | //***************************************************************************** |
| 102 | |
| 103 | //----------------------------------------------------------------------------- |
| 104 | //* Reflect |
| 105 | //! Help function when creating the CRC Table |
| 106 | //! Swaps bit 0 for bit 7 |
| 107 | //! bit 1 for bit 6 |
| 108 | //! bit 2 for bit 5 ... |
| 109 | //----------------------------------------------------------------------------- |
| 110 | unsigned int CRCCalculator2::_reflect(unsigned int ref, char ch) |
| 111 | { |
| 112 | unsigned int value = 0; |
| 113 | for (int i=1; i<(ch + 1); ++i) |
| 114 | { |
| 115 | if(ref & 1) |
| 116 | { |
| 117 | value |= 1 << (ch - i); |
| 118 | } |
| 119 | ref >>= 1; |
| 120 | } |
| 121 | return value; |
| 122 | } |