src/bin/unzip/crctab.c

   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 */