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