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 "CRCCalculator.h" |
23 | |
24 | #define CRC32_POLYNOMIAL 0xedb88320L //0x04C11DB7 |
25 | typedef unsigned char byte; |
26 | |
27 | //----------------------------------------------------------------------------- |
28 | // Static Variabels |
29 | //----------------------------------------------------------------------------- |
30 | unsigned int CRCCalculator::m_crcTable[256] = {0}; |
31 | |
32 | static unsigned int crc_table[256]; |
33 | |
34 | //----------------------------------------------------------------------------- |
35 | //! Constructor |
36 | //----------------------------------------------------------------------------- |
37 | CRCCalculator::CRCCalculator() |
38 | { |
39 | static bool hashTableInitialized = false; |
40 | |
41 | //Build hash table |
42 | //http://www.gamedev.net/reference/articles/article1941.asp |
43 | if ( !hashTableInitialized ) |
44 | { |
45 | // unsigned int crc; |
46 | |
47 | // //For each value |
48 | // for (int i=0; i<256; i++) |
49 | //{ |
50 | // crc = _reflect( i, 8 ) << 24; |
51 | |
52 | // for (int j = 0; j < 8; j++) |
53 | // { |
54 | // crc = (crc << 1) ^ (crc & (1 << 31) ? CRC32_POLYNOMIAL : 0); |
55 | // } |
56 | // |
57 | // m_crcTable[i] = _reflect( crc, 32 ); |
58 | // } |
59 | |
60 | unsigned int crc; |
61 | unsigned int poly; // polynomial exclusive-or pattern |
62 | // terms of polynomial defining this crc (except x^32): |
63 | static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26}; |
64 | |
65 | /* make exclusive-or pattern from polynomial (0xedb88320L) */ |
66 | poly = 0L; |
67 | for (unsigned int n = 0; n < sizeof(p)/sizeof(unsigned char); n++) |
68 | { |
69 | poly |= 1L << (31 - p[n]); |
70 | } |
71 | |
72 | for (int n=0; n<256; ++n) |
73 | { |
74 | crc = (unsigned int)n; |
75 | |
76 | for (int k = 0; k < 8; k++) |
77 | { |
78 | crc = (crc & 1) ? (poly ^ (crc >> 1)) : crc >> 1; |
79 | } |
80 | crc_table[n] = crc; |
81 | } |
82 | |
83 | hashTableInitialized = true; |
84 | } |
85 | } |
86 | |
87 | //----------------------------------------------------------------------------- |
88 | // CalculateCRC |
89 | //----------------------------------------------------------------------------- |
90 | #define DO1(buf) crc = crc_table[((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8); |
91 | #define DO1b(buf) crc = (crc >> 8) ^ crc_table[(crc & 0xFF) ^ *buf++] |
92 | unsigned int CRCCalculator::calcCRC(unsigned int crc, void *buffer, unsigned int count) |
93 | { |
94 | byte* p = (byte*) buffer; |
95 | //unsigned int orig = crc; |
96 | |
97 | // p = (byte*) buffer; |
98 | // while (count--) |
99 | // { |
100 | // crc = (crc >> 8) ^ m_crcTable[(crc & 0xFF) ^ *p++]; |
101 | // } |
102 | |
103 | // return crc ^ orig; |
104 | |
105 | if (buffer == 0) return 0L; |
106 | |
107 | crc = crc ^ 0xffffffffL; |
108 | while (count--) |
109 | { |
110 | crc = crc_table[((int)crc ^ (*p++)) & 0xff] ^ (crc >> 8); |
111 | } |
112 | // if (len) do { |
113 | // DO1(buf); |
114 | // } while (--len); |
115 | return crc ^ 0xffffffffL; |
116 | } |
117 | |
118 | //----------------------------------------------------------------------------- |
119 | // CalculatePaletteCRC |
120 | //----------------------------------------------------------------------------- |
121 | unsigned int CRCCalculator::calcPaletteCRC(unsigned int crc, void *buffer, unsigned int count) |
122 | { |
123 | byte *p; |
124 | unsigned int orig = crc; |
125 | |
126 | p = (byte*) buffer; |
127 | while (count--) |
128 | { |
129 | crc = (crc >> 8) ^ m_crcTable[(crc & 0xFF) ^ *p++]; |
130 | crc = (crc >> 8) ^ m_crcTable[(crc & 0xFF) ^ *p++]; |
131 | |
132 | p += 6; |
133 | } |
134 | |
135 | return crc ^ orig; |
136 | } |
137 | |
138 | //***************************************************************************** |
139 | // Private Functions |
140 | //***************************************************************************** |
141 | |
142 | //----------------------------------------------------------------------------- |
143 | //* Reflect |
144 | //! Help function when creating the CRC Table |
145 | //! Swaps bit 0 for bit 7 |
146 | //! bit 1 for bit 6 |
147 | //! bit 2 for bit 5 ... |
148 | //----------------------------------------------------------------------------- |
149 | unsigned int CRCCalculator::_reflect(unsigned int ref, char ch) |
150 | { |
151 | unsigned int value = 0; |
152 | for (int i=1; i<(ch + 1); ++i) |
153 | { |
154 | if(ref & 1) |
155 | { |
156 | value |= 1 << (ch - i); |
157 | } |
158 | ref >>= 1; |
159 | } |
160 | return value; |
161 | } |