2 #include "../precompiled.h"
7 Copyright (C) 1995-1998 Mark Adler
10 #define CRC32_INIT_VALUE 0xffffffffL
11 #define CRC32_XOR_VALUE 0xffffffffL
13 #ifdef CREATE_CRC_TABLE
15 static unsigned long crctable[256];
18 Generate a table for a byte-wise 32-bit CRC calculation on the polynomial:
19 x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x^1+x^0.
21 Polynomials over GF(2) are represented in binary, one bit per coefficient,
22 with the lowest powers in the most significant bit. Then adding polynomials
23 is just exclusive-or, and multiplying a polynomial by x is a right shift by
24 one. If we call the above polynomial p, and represent a byte as the
25 polynomial q, also with the lowest power in the most significant bit (so the
26 byte 0xb1 is the polynomial x^7+x^3+x^1+x^0), then the CRC is (q*x^32) mod p,
27 where a mod b means the remainder after dividing a by b.
29 This calculation is done using the shift-register method of multiplying and
30 taking the remainder. The register is initialized to zero, and for each
31 incoming bit, x^32 is added mod p to the register if the bit is a one (where
32 x^32 mod p is p+x^32 = x^26+...+x^0), and the register is multiplied mod p by
33 x (which is shifting right by one and adding x^32 mod p if the bit shifted
34 out is a one). We start with the highest power (least significant bit) of
35 q and repeat for all eight bits of q.
37 The table is simply the CRC of all possible eight bit values. This is all
38 the information needed to generate CRC's on data a byte at a time for all
39 combinations of CRC register values and incoming bytes.
42 void make_crc_table( void ) {
44 unsigned long c, poly;
45 /* terms of polynomial defining this crc (except x^32): */
46 static const byte p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
48 /* make exclusive-or pattern from polynomial (0xedb88320L) */
50 for ( i = 0; i < sizeof( p ) / sizeof( byte ); i++ ) {
51 poly |= 1L << ( 31 - p[i] );
54 for ( i = 0; i < 256; i++ ) {
56 for ( j = 0; j < 8; j++ ) {
57 c = ( c & 1 ) ? poly ^ ( c >> 1 ) : ( c >> 1 );
66 Table of CRC-32's of all single-byte values (made by make_crc_table)
68 static unsigned long crctable[256] = {
69 0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL,
70 0x076dc419L, 0x706af48fL, 0xe963a535L, 0x9e6495a3L,
71 0x0edb8832L, 0x79dcb8a4L, 0xe0d5e91eL, 0x97d2d988L,
72 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L, 0x90bf1d91L,
73 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
74 0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L,
75 0x136c9856L, 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL,
76 0x14015c4fL, 0x63066cd9L, 0xfa0f3d63L, 0x8d080df5L,
77 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L, 0xa2677172L,
78 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
79 0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L,
80 0x32d86ce3L, 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L,
81 0x26d930acL, 0x51de003aL, 0xc8d75180L, 0xbfd06116L,
82 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L, 0xb8bda50fL,
83 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
84 0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL,
85 0x76dc4190L, 0x01db7106L, 0x98d220bcL, 0xefd5102aL,
86 0x71b18589L, 0x06b6b51fL, 0x9fbfe4a5L, 0xe8b8d433L,
87 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL, 0xe10e9818L,
88 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
89 0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL,
90 0x6c0695edL, 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L,
91 0x65b0d9c6L, 0x12b7e950L, 0x8bbeb8eaL, 0xfcb9887cL,
92 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L, 0xfbd44c65L,
93 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
94 0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL,
95 0x4369e96aL, 0x346ed9fcL, 0xad678846L, 0xda60b8d0L,
96 0x44042d73L, 0x33031de5L, 0xaa0a4c5fL, 0xdd0d7cc9L,
97 0x5005713cL, 0x270241aaL, 0xbe0b1010L, 0xc90c2086L,
98 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
99 0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L,
100 0x59b33d17L, 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL,
101 0xedb88320L, 0x9abfb3b6L, 0x03b6e20cL, 0x74b1d29aL,
102 0xead54739L, 0x9dd277afL, 0x04db2615L, 0x73dc1683L,
103 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
104 0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L,
105 0xf00f9344L, 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL,
106 0xf762575dL, 0x806567cbL, 0x196c3671L, 0x6e6b06e7L,
107 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL, 0x67dd4accL,
108 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
109 0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L,
110 0xd1bb67f1L, 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL,
111 0xd80d2bdaL, 0xaf0a1b4cL, 0x36034af6L, 0x41047a60L,
112 0xdf60efc3L, 0xa867df55L, 0x316e8eefL, 0x4669be79L,
113 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
114 0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL,
115 0xc5ba3bbeL, 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L,
116 0xc2d7ffa7L, 0xb5d0cf31L, 0x2cd99e8bL, 0x5bdeae1dL,
117 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL, 0x026d930aL,
118 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
119 0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L,
120 0x92d28e9bL, 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L,
121 0x86d3d2d4L, 0xf1d4e242L, 0x68ddb3f8L, 0x1fda836eL,
122 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L, 0x18b74777L,
123 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
124 0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L,
125 0xa00ae278L, 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L,
126 0xa7672661L, 0xd06016f7L, 0x4969474dL, 0x3e6e77dbL,
127 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L, 0x37d83bf0L,
128 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
129 0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L,
130 0xbad03605L, 0xcdd70693L, 0x54de5729L, 0x23d967bfL,
131 0xb3667a2eL, 0xc4614ab8L, 0x5d681b02L, 0x2a6f2b94L,
132 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL, 0x2d02ef8dL
137 void CRC32_InitChecksum( unsigned long &crcvalue ) {
138 crcvalue = CRC32_INIT_VALUE;
141 void CRC32_Update( unsigned long &crcvalue, const byte data ) {
142 crcvalue = crctable[ ( crcvalue ^ data ) & 0xff ] ^ ( crcvalue >> 8 );
145 void CRC32_UpdateChecksum( unsigned long &crcvalue, const void *data, int length ) {
147 const unsigned char *buf = (const unsigned char *) data;
151 crc = crctable[ ( crc ^ ( *buf++ ) ) & 0xff ] ^ ( crc >> 8 );
156 void CRC32_FinishChecksum( unsigned long &crcvalue ) {
157 crcvalue ^= CRC32_XOR_VALUE;
160 unsigned long CRC32_BlockChecksum( const void *data, int length ) {
163 CRC32_InitChecksum( crc );
164 CRC32_UpdateChecksum( crc, data, length );
165 CRC32_FinishChecksum( crc );