22726e4d |
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 | } |