1 /* 2 Copyright (c) 1990-2000 Info-ZIP. All rights reserved. 3 4 See the accompanying file LICENSE, version 2000-Apr-09 or later 5 (the contents of which are also included in zip.h) for terms of use. 6 If, for some reason, all these files are missing, the Info-ZIP license 7 also may be found at: ftp://ftp.info-zip.org/pub/infozip/license.html 8 */ 9 /* crctab.c -- supply the CRC table needed for CRC-32 calculations. 10 * Copyright (C) 1995 Mark Adler 11 * For conditions of distribution and use, see copyright notice in zlib.h 12 */ 13 14 /* $Id: crctab.c 1101 2002-09-21 14:54:45Z darkwyrm $ */ 15 16 /* 17 Generate a table for a byte-wise 32-bit CRC calculation on the polynomial: 18 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. 19 20 Polynomials over GF(2) are represented in binary, one bit per coefficient, 21 with the lowest powers in the most significant bit. Then adding polynomials 22 is just exclusive-or, and multiplying a polynomial by x is a right shift by 23 one. If we call the above polynomial p, and represent a byte as the 24 polynomial q, also with the lowest power in the most significant bit (so the 25 byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p, 26 where a mod b means the remainder after dividing a by b. 27 28 This calculation is done using the shift-register method of multiplying and 29 taking the remainder. The register is initialized to zero, and for each 30 incoming bit, x^32 is added mod p to the register if the bit is a one (where 31 x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by 32 x (which is shifting right by one and adding x^32 mod p if the bit shifted 33 out is a one). We start with the highest power (least significant bit) of 34 q and repeat for all eight bits of q. 35 36 The table is simply the CRC of all possible eight bit values. This is all 37 the information needed to generate CRC's on data a byte at a time for all 38 combinations of CRC register values and incoming bytes. 39 */ 40 41 #define __CRCTAB_C /* identifies this source module */ 42 43 #include "zip.h" 44 45 #if (!defined(USE_ZLIB) || defined(USE_OWN_CRCTAB)) 46 47 #ifndef ZCONST 48 # define ZCONST const 49 #endif 50 51 #ifdef DYNAMIC_CRC_TABLE 52 53 /* ========================================================================= 54 * Make the crc table. This function is needed only if you want to compute 55 * the table dynamically. 56 */ 57 58 local void make_crc_table OF((void)); 59 60 #if (defined(DYNALLOC_CRCTAB) && defined(REENTRANT)) 61 error: Dynamic allocation of CRC table not safe with reentrant code. 62 #endif /* DYNALLOC_CRCTAB && REENTRANT */ 63 64 #ifdef DYNALLOC_CRCTAB 65 local ulg near *crc_table = NULL; 66 # if 0 /* not used, since sizeof("near *") <= sizeof(int) */ 67 /* Use this section when access to a "local int" is faster than access to 68 a "local pointer" (e.g.: i86 16bit code with far pointers). */ 69 local int crc_table_empty = 1; 70 # define CRC_TABLE_IS_EMPTY (crc_table_empty != 0) 71 # define MARK_CRCTAB_FILLED crc_table_empty = 0 72 # define MARK_CRCTAB_EMPTY crc_table_empty = 1 73 # else 74 /* Use this section on systems where the size of pointers and ints is 75 equal (e.g.: all 32bit systems). */ 76 # define CRC_TABLE_IS_EMPTY (crc_table == NULL) 77 # define MARK_CRCTAB_FILLED crc_table = crctab_p 78 # define MARK_CRCTAB_EMPTY crc_table = NULL 79 # endif 80 #else /* !DYNALLOC_CRCTAB */ 81 local ulg near crc_table[256]; 82 local int crc_table_empty = 1; 83 # define CRC_TABLE_IS_EMPTY (crc_table_empty != 0) 84 # define MARK_CRCTAB_FILLED crc_table_empty = 0 85 #endif /* ?DYNALLOC_CRCTAB */ 86 87 88 local void make_crc_table() 89 { 90 ulg c; /* crc shift register */ 91 int n; /* counter for all possible eight bit values */ 92 int k; /* byte being shifted into crc apparatus */ 93 #ifdef DYNALLOC_CRCTAB 94 ulg near *crctab_p; /* temporary pointer to allocated crc_table area */ 95 #else /* !DYNALLOC_CRCTAB */ 96 # define crctab_p crc_table 97 #endif /* DYNALLOC_CRCTAB */ 98 99 #ifdef COMPUTE_XOR_PATTERN 100 /* This piece of code has been left here to explain how the XOR pattern 101 * used in the creation of the crc_table values can be recomputed. 102 * For production versions of this function, it is more efficient to 103 * supply the resultant pattern at compile time. 104 */ 105 ulg xor; /* polynomial exclusive-or pattern */ 106 /* terms of polynomial defining this crc (except x^32): */ 107 static uch p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26}; 108 109 /* make exclusive-or pattern from polynomial (0xedb88320L) */ 110 xor = 0L; 111 for (i = 0; i < sizeof(p)/sizeof(uch); i++) 112 xor |= 1L << (31 - p[i]); 113 #else 114 # define xor 0xedb88320L 115 #endif 116 117 #ifdef DYNALLOC_CRCTAB 118 crctab_p = (ulg near *) nearmalloc (256*sizeof(ulg)); 119 if (crctab_p == NULL) { 120 ziperr(ZE_MEM, "crc_table allocation"); 121 } 122 #endif /* DYNALLOC_CRCTAB */ 123 124 for (n = 0; n < 256; n++) { 125 c = (ulg)n; 126 for (k = 8; k; k--) 127 c = c & 1 ? xor ^ (c >> 1) : c >> 1; 128 crctab_p[n] = c; 129 } 130 MARK_CRCTAB_FILLED; 131 } 132 133 #else /* !DYNAMIC_CRC_TABLE */ 134 135 #ifdef DYNALLOC_CRCTAB 136 error: Inconsistent flags, DYNALLOC_CRCTAB without DYNAMIC_CRC_TABLE. 137 #endif 138 139 /* ======================================================================== 140 * Table of CRC-32's of all single-byte values (made by make_crc_table) 141 */ 142 local ZCONST ulg near crc_table[256] = { 143 0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L, 144 0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L, 145 0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L, 146 0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL, 147 0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L, 148 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L, 149 0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L, 150 0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL, 151 0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L, 152 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL, 153 0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L, 154 0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L, 155 0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L, 156 0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL, 157 0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL, 158 0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L, 159 0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL, 160 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L, 161 0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L, 162 0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L, 163 0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL, 164 0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L, 165 0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L, 166 0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL, 167 0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L, 168 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L, 169 0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L, 170 0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L, 171 0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L, 172 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL, 173 0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL, 174 0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L, 175 0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L, 176 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL, 177 0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL, 178 0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L, 179 0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL, 180 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L, 181 0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL, 182 0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L, 183 0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL, 184 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L, 185 0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L, 186 0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL, 187 0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L, 188 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L, 189 0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L, 190 0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L, 191 0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L, 192 0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L, 193 0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL, 194 0x2d02ef8dL 195 }; 196 #endif /* ?DYNAMIC_CRC_TABLE */ 197 198 /* use "OF((void))" here to work around a Borland TC++ 1.0 problem */ 199 #ifdef USE_ZLIB 200 ZCONST uLongf *get_crc_table OF((void)) 201 #else 202 ZCONST ulg near *get_crc_table OF((void)) 203 #endif 204 { 205 #ifdef DYNAMIC_CRC_TABLE 206 if (CRC_TABLE_IS_EMPTY) 207 make_crc_table(); 208 #endif 209 #ifdef USE_ZLIB 210 return (ZCONST uLongf *)crc_table; 211 #else 212 return (ZCONST ulg near *)crc_table; 213 #endif 214 } 215 216 #ifdef DYNALLOC_CRCTAB 217 void free_crc_table() 218 { 219 if (!CRC_TABLE_IS_EMPTY) 220 { 221 nearfree((ulg near *)crc_table); 222 MARK_CRCTAB_EMPTY; 223 } 224 } 225 #endif 226 227 #endif /* !USE_ZLIB || USE_OWN_CRCTAB */ 228