dbf-halloween2015

annotate libs/zlib/crc32.c @ 1:c3f5c32cb210

find changesets by author, revision, files, or words in the commit message
barfed all the libraries in the source tree to make porting easier
author John Tsiombikas <nuclear@member.fsf.org>
date Sun, 01 Nov 2015 00:36:56 +0200
parents
children
rev   line source
nuclear@1 1 /* crc32.c -- compute the CRC-32 of a data stream
nuclear@1 2 * Copyright (C) 1995-2005 Mark Adler
nuclear@1 3 * For conditions of distribution and use, see copyright notice in zlib.h
nuclear@1 4 *
nuclear@1 5 * Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster
nuclear@1 6 * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
nuclear@1 7 * tables for updating the shift register in one step with three exclusive-ors
nuclear@1 8 * instead of four steps with four exclusive-ors. This results in about a
nuclear@1 9 * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
nuclear@1 10 */
nuclear@1 11
nuclear@1 12 /* @(#) $Id$ */
nuclear@1 13
nuclear@1 14 /*
nuclear@1 15 Note on the use of DYNAMIC_CRC_TABLE: there is no mutex or semaphore
nuclear@1 16 protection on the static variables used to control the first-use generation
nuclear@1 17 of the crc tables. Therefore, if you #define DYNAMIC_CRC_TABLE, you should
nuclear@1 18 first call get_crc_table() to initialize the tables before allowing more than
nuclear@1 19 one thread to use crc32().
nuclear@1 20 */
nuclear@1 21
nuclear@1 22 #ifdef MAKECRCH
nuclear@1 23 # include <stdio.h>
nuclear@1 24 # ifndef DYNAMIC_CRC_TABLE
nuclear@1 25 # define DYNAMIC_CRC_TABLE
nuclear@1 26 # endif /* !DYNAMIC_CRC_TABLE */
nuclear@1 27 #endif /* MAKECRCH */
nuclear@1 28
nuclear@1 29 #include "zutil.h" /* for STDC and FAR definitions */
nuclear@1 30
nuclear@1 31 #define local static
nuclear@1 32
nuclear@1 33 /* Find a four-byte integer type for crc32_little() and crc32_big(). */
nuclear@1 34 #ifndef NOBYFOUR
nuclear@1 35 # ifdef STDC /* need ANSI C limits.h to determine sizes */
nuclear@1 36 # include <limits.h>
nuclear@1 37 # define BYFOUR
nuclear@1 38 # if (UINT_MAX == 0xffffffffUL)
nuclear@1 39 typedef unsigned int u4;
nuclear@1 40 # else
nuclear@1 41 # if (ULONG_MAX == 0xffffffffUL)
nuclear@1 42 typedef unsigned long u4;
nuclear@1 43 # else
nuclear@1 44 # if (USHRT_MAX == 0xffffffffUL)
nuclear@1 45 typedef unsigned short u4;
nuclear@1 46 # else
nuclear@1 47 # undef BYFOUR /* can't find a four-byte integer type! */
nuclear@1 48 # endif
nuclear@1 49 # endif
nuclear@1 50 # endif
nuclear@1 51 # endif /* STDC */
nuclear@1 52 #endif /* !NOBYFOUR */
nuclear@1 53
nuclear@1 54 /* Definitions for doing the crc four data bytes at a time. */
nuclear@1 55 #ifdef BYFOUR
nuclear@1 56 # define REV(w) (((w)>>24)+(((w)>>8)&0xff00)+ \
nuclear@1 57 (((w)&0xff00)<<8)+(((w)&0xff)<<24))
nuclear@1 58 local unsigned long crc32_little OF((unsigned long,
nuclear@1 59 const unsigned char FAR *, unsigned));
nuclear@1 60 local unsigned long crc32_big OF((unsigned long,
nuclear@1 61 const unsigned char FAR *, unsigned));
nuclear@1 62 # define TBLS 8
nuclear@1 63 #else
nuclear@1 64 # define TBLS 1
nuclear@1 65 #endif /* BYFOUR */
nuclear@1 66
nuclear@1 67 /* Local functions for crc concatenation */
nuclear@1 68 local unsigned long gf2_matrix_times OF((unsigned long *mat,
nuclear@1 69 unsigned long vec));
nuclear@1 70 local void gf2_matrix_square OF((unsigned long *square, unsigned long *mat));
nuclear@1 71
nuclear@1 72 #ifdef DYNAMIC_CRC_TABLE
nuclear@1 73
nuclear@1 74 local volatile int crc_table_empty = 1;
nuclear@1 75 local unsigned long FAR crc_table[TBLS][256];
nuclear@1 76 local void make_crc_table OF((void));
nuclear@1 77 #ifdef MAKECRCH
nuclear@1 78 local void write_table OF((FILE *, const unsigned long FAR *));
nuclear@1 79 #endif /* MAKECRCH */
nuclear@1 80 /*
nuclear@1 81 Generate tables for a byte-wise 32-bit CRC calculation on the polynomial:
nuclear@1 82 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.
nuclear@1 83
nuclear@1 84 Polynomials over GF(2) are represented in binary, one bit per coefficient,
nuclear@1 85 with the lowest powers in the most significant bit. Then adding polynomials
nuclear@1 86 is just exclusive-or, and multiplying a polynomial by x is a right shift by
nuclear@1 87 one. If we call the above polynomial p, and represent a byte as the
nuclear@1 88 polynomial q, also with the lowest power in the most significant bit (so the
nuclear@1 89 byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
nuclear@1 90 where a mod b means the remainder after dividing a by b.
nuclear@1 91
nuclear@1 92 This calculation is done using the shift-register method of multiplying and
nuclear@1 93 taking the remainder. The register is initialized to zero, and for each
nuclear@1 94 incoming bit, x^32 is added mod p to the register if the bit is a one (where
nuclear@1 95 x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
nuclear@1 96 x (which is shifting right by one and adding x^32 mod p if the bit shifted
nuclear@1 97 out is a one). We start with the highest power (least significant bit) of
nuclear@1 98 q and repeat for all eight bits of q.
nuclear@1 99
nuclear@1 100 The first table is simply the CRC of all possible eight bit values. This is
nuclear@1 101 all the information needed to generate CRCs on data a byte at a time for all
nuclear@1 102 combinations of CRC register values and incoming bytes. The remaining tables
nuclear@1 103 allow for word-at-a-time CRC calculation for both big-endian and little-
nuclear@1 104 endian machines, where a word is four bytes.
nuclear@1 105 */
nuclear@1 106 local void make_crc_table()
nuclear@1 107 {
nuclear@1 108 unsigned long c;
nuclear@1 109 int n, k;
nuclear@1 110 unsigned long poly; /* polynomial exclusive-or pattern */
nuclear@1 111 /* terms of polynomial defining this crc (except x^32): */
nuclear@1 112 static volatile int first = 1; /* flag to limit concurrent making */
nuclear@1 113 static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
nuclear@1 114
nuclear@1 115 /* See if another task is already doing this (not thread-safe, but better
nuclear@1 116 than nothing -- significantly reduces duration of vulnerability in
nuclear@1 117 case the advice about DYNAMIC_CRC_TABLE is ignored) */
nuclear@1 118 if (first) {
nuclear@1 119 first = 0;
nuclear@1 120
nuclear@1 121 /* make exclusive-or pattern from polynomial (0xedb88320UL) */
nuclear@1 122 poly = 0UL;
nuclear@1 123 for (n = 0; n < sizeof(p)/sizeof(unsigned char); n++)
nuclear@1 124 poly |= 1UL << (31 - p[n]);
nuclear@1 125
nuclear@1 126 /* generate a crc for every 8-bit value */
nuclear@1 127 for (n = 0; n < 256; n++) {
nuclear@1 128 c = (unsigned long)n;
nuclear@1 129 for (k = 0; k < 8; k++)
nuclear@1 130 c = c & 1 ? poly ^ (c >> 1) : c >> 1;
nuclear@1 131 crc_table[0][n] = c;
nuclear@1 132 }
nuclear@1 133
nuclear@1 134 #ifdef BYFOUR
nuclear@1 135 /* generate crc for each value followed by one, two, and three zeros,
nuclear@1 136 and then the byte reversal of those as well as the first table */
nuclear@1 137 for (n = 0; n < 256; n++) {
nuclear@1 138 c = crc_table[0][n];
nuclear@1 139 crc_table[4][n] = REV(c);
nuclear@1 140 for (k = 1; k < 4; k++) {
nuclear@1 141 c = crc_table[0][c & 0xff] ^ (c >> 8);
nuclear@1 142 crc_table[k][n] = c;
nuclear@1 143 crc_table[k + 4][n] = REV(c);
nuclear@1 144 }
nuclear@1 145 }
nuclear@1 146 #endif /* BYFOUR */
nuclear@1 147
nuclear@1 148 crc_table_empty = 0;
nuclear@1 149 }
nuclear@1 150 else { /* not first */
nuclear@1 151 /* wait for the other guy to finish (not efficient, but rare) */
nuclear@1 152 while (crc_table_empty)
nuclear@1 153 ;
nuclear@1 154 }
nuclear@1 155
nuclear@1 156 #ifdef MAKECRCH
nuclear@1 157 /* write out CRC tables to crc32.h */
nuclear@1 158 {
nuclear@1 159 FILE *out;
nuclear@1 160
nuclear@1 161 out = fopen("crc32.h", "w");
nuclear@1 162 if (out == NULL) return;
nuclear@1 163 fprintf(out, "/* crc32.h -- tables for rapid CRC calculation\n");
nuclear@1 164 fprintf(out, " * Generated automatically by crc32.c\n */\n\n");
nuclear@1 165 fprintf(out, "local const unsigned long FAR ");
nuclear@1 166 fprintf(out, "crc_table[TBLS][256] =\n{\n {\n");
nuclear@1 167 write_table(out, crc_table[0]);
nuclear@1 168 # ifdef BYFOUR
nuclear@1 169 fprintf(out, "#ifdef BYFOUR\n");
nuclear@1 170 for (k = 1; k < 8; k++) {
nuclear@1 171 fprintf(out, " },\n {\n");
nuclear@1 172 write_table(out, crc_table[k]);
nuclear@1 173 }
nuclear@1 174 fprintf(out, "#endif\n");
nuclear@1 175 # endif /* BYFOUR */
nuclear@1 176 fprintf(out, " }\n};\n");
nuclear@1 177 fclose(out);
nuclear@1 178 }
nuclear@1 179 #endif /* MAKECRCH */
nuclear@1 180 }
nuclear@1 181
nuclear@1 182 #ifdef MAKECRCH
nuclear@1 183 local void write_table(out, table)
nuclear@1 184 FILE *out;
nuclear@1 185 const unsigned long FAR *table;
nuclear@1 186 {
nuclear@1 187 int n;
nuclear@1 188
nuclear@1 189 for (n = 0; n < 256; n++)
nuclear@1 190 fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : " ", table[n],
nuclear@1 191 n == 255 ? "\n" : (n % 5 == 4 ? ",\n" : ", "));
nuclear@1 192 }
nuclear@1 193 #endif /* MAKECRCH */
nuclear@1 194
nuclear@1 195 #else /* !DYNAMIC_CRC_TABLE */
nuclear@1 196 /* ========================================================================
nuclear@1 197 * Tables of CRC-32s of all single-byte values, made by make_crc_table().
nuclear@1 198 */
nuclear@1 199 #include "crc32.h"
nuclear@1 200 #endif /* DYNAMIC_CRC_TABLE */
nuclear@1 201
nuclear@1 202 /* =========================================================================
nuclear@1 203 * This function can be used by asm versions of crc32()
nuclear@1 204 */
nuclear@1 205 const unsigned long FAR * ZEXPORT get_crc_table()
nuclear@1 206 {
nuclear@1 207 #ifdef DYNAMIC_CRC_TABLE
nuclear@1 208 if (crc_table_empty)
nuclear@1 209 make_crc_table();
nuclear@1 210 #endif /* DYNAMIC_CRC_TABLE */
nuclear@1 211 return (const unsigned long FAR *)crc_table;
nuclear@1 212 }
nuclear@1 213
nuclear@1 214 /* ========================================================================= */
nuclear@1 215 #define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8)
nuclear@1 216 #define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1
nuclear@1 217
nuclear@1 218 /* ========================================================================= */
nuclear@1 219 unsigned long ZEXPORT crc32(crc, buf, len)
nuclear@1 220 unsigned long crc;
nuclear@1 221 const unsigned char FAR *buf;
nuclear@1 222 unsigned len;
nuclear@1 223 {
nuclear@1 224 if (buf == Z_NULL) return 0UL;
nuclear@1 225
nuclear@1 226 #ifdef DYNAMIC_CRC_TABLE
nuclear@1 227 if (crc_table_empty)
nuclear@1 228 make_crc_table();
nuclear@1 229 #endif /* DYNAMIC_CRC_TABLE */
nuclear@1 230
nuclear@1 231 #ifdef BYFOUR
nuclear@1 232 if (sizeof(void *) == sizeof(ptrdiff_t)) {
nuclear@1 233 u4 endian;
nuclear@1 234
nuclear@1 235 endian = 1;
nuclear@1 236 if (*((unsigned char *)(&endian)))
nuclear@1 237 return crc32_little(crc, buf, len);
nuclear@1 238 else
nuclear@1 239 return crc32_big(crc, buf, len);
nuclear@1 240 }
nuclear@1 241 #endif /* BYFOUR */
nuclear@1 242 crc = crc ^ 0xffffffffUL;
nuclear@1 243 while (len >= 8) {
nuclear@1 244 DO8;
nuclear@1 245 len -= 8;
nuclear@1 246 }
nuclear@1 247 if (len) do {
nuclear@1 248 DO1;
nuclear@1 249 } while (--len);
nuclear@1 250 return crc ^ 0xffffffffUL;
nuclear@1 251 }
nuclear@1 252
nuclear@1 253 #ifdef BYFOUR
nuclear@1 254
nuclear@1 255 /* ========================================================================= */
nuclear@1 256 #define DOLIT4 c ^= *buf4++; \
nuclear@1 257 c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \
nuclear@1 258 crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24]
nuclear@1 259 #define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4
nuclear@1 260
nuclear@1 261 /* ========================================================================= */
nuclear@1 262 local unsigned long crc32_little(crc, buf, len)
nuclear@1 263 unsigned long crc;
nuclear@1 264 const unsigned char FAR *buf;
nuclear@1 265 unsigned len;
nuclear@1 266 {
nuclear@1 267 register u4 c;
nuclear@1 268 register const u4 FAR *buf4;
nuclear@1 269
nuclear@1 270 c = (u4)crc;
nuclear@1 271 c = ~c;
nuclear@1 272 while (len && ((ptrdiff_t)buf & 3)) {
nuclear@1 273 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
nuclear@1 274 len--;
nuclear@1 275 }
nuclear@1 276
nuclear@1 277 buf4 = (const u4 FAR *)(const void FAR *)buf;
nuclear@1 278 while (len >= 32) {
nuclear@1 279 DOLIT32;
nuclear@1 280 len -= 32;
nuclear@1 281 }
nuclear@1 282 while (len >= 4) {
nuclear@1 283 DOLIT4;
nuclear@1 284 len -= 4;
nuclear@1 285 }
nuclear@1 286 buf = (const unsigned char FAR *)buf4;
nuclear@1 287
nuclear@1 288 if (len) do {
nuclear@1 289 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
nuclear@1 290 } while (--len);
nuclear@1 291 c = ~c;
nuclear@1 292 return (unsigned long)c;
nuclear@1 293 }
nuclear@1 294
nuclear@1 295 /* ========================================================================= */
nuclear@1 296 #define DOBIG4 c ^= *++buf4; \
nuclear@1 297 c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \
nuclear@1 298 crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24]
nuclear@1 299 #define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4
nuclear@1 300
nuclear@1 301 /* ========================================================================= */
nuclear@1 302 local unsigned long crc32_big(crc, buf, len)
nuclear@1 303 unsigned long crc;
nuclear@1 304 const unsigned char FAR *buf;
nuclear@1 305 unsigned len;
nuclear@1 306 {
nuclear@1 307 register u4 c;
nuclear@1 308 register const u4 FAR *buf4;
nuclear@1 309
nuclear@1 310 c = REV((u4)crc);
nuclear@1 311 c = ~c;
nuclear@1 312 while (len && ((ptrdiff_t)buf & 3)) {
nuclear@1 313 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
nuclear@1 314 len--;
nuclear@1 315 }
nuclear@1 316
nuclear@1 317 buf4 = (const u4 FAR *)(const void FAR *)buf;
nuclear@1 318 buf4--;
nuclear@1 319 while (len >= 32) {
nuclear@1 320 DOBIG32;
nuclear@1 321 len -= 32;
nuclear@1 322 }
nuclear@1 323 while (len >= 4) {
nuclear@1 324 DOBIG4;
nuclear@1 325 len -= 4;
nuclear@1 326 }
nuclear@1 327 buf4++;
nuclear@1 328 buf = (const unsigned char FAR *)buf4;
nuclear@1 329
nuclear@1 330 if (len) do {
nuclear@1 331 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
nuclear@1 332 } while (--len);
nuclear@1 333 c = ~c;
nuclear@1 334 return (unsigned long)(REV(c));
nuclear@1 335 }
nuclear@1 336
nuclear@1 337 #endif /* BYFOUR */
nuclear@1 338
nuclear@1 339 #define GF2_DIM 32 /* dimension of GF(2) vectors (length of CRC) */
nuclear@1 340
nuclear@1 341 /* ========================================================================= */
nuclear@1 342 local unsigned long gf2_matrix_times(mat, vec)
nuclear@1 343 unsigned long *mat;
nuclear@1 344 unsigned long vec;
nuclear@1 345 {
nuclear@1 346 unsigned long sum;
nuclear@1 347
nuclear@1 348 sum = 0;
nuclear@1 349 while (vec) {
nuclear@1 350 if (vec & 1)
nuclear@1 351 sum ^= *mat;
nuclear@1 352 vec >>= 1;
nuclear@1 353 mat++;
nuclear@1 354 }
nuclear@1 355 return sum;
nuclear@1 356 }
nuclear@1 357
nuclear@1 358 /* ========================================================================= */
nuclear@1 359 local void gf2_matrix_square(square, mat)
nuclear@1 360 unsigned long *square;
nuclear@1 361 unsigned long *mat;
nuclear@1 362 {
nuclear@1 363 int n;
nuclear@1 364
nuclear@1 365 for (n = 0; n < GF2_DIM; n++)
nuclear@1 366 square[n] = gf2_matrix_times(mat, mat[n]);
nuclear@1 367 }
nuclear@1 368
nuclear@1 369 /* ========================================================================= */
nuclear@1 370 uLong ZEXPORT crc32_combine(crc1, crc2, len2)
nuclear@1 371 uLong crc1;
nuclear@1 372 uLong crc2;
nuclear@1 373 z_off_t len2;
nuclear@1 374 {
nuclear@1 375 int n;
nuclear@1 376 unsigned long row;
nuclear@1 377 unsigned long even[GF2_DIM]; /* even-power-of-two zeros operator */
nuclear@1 378 unsigned long odd[GF2_DIM]; /* odd-power-of-two zeros operator */
nuclear@1 379
nuclear@1 380 /* degenerate case */
nuclear@1 381 if (len2 == 0)
nuclear@1 382 return crc1;
nuclear@1 383
nuclear@1 384 /* put operator for one zero bit in odd */
nuclear@1 385 odd[0] = 0xedb88320L; /* CRC-32 polynomial */
nuclear@1 386 row = 1;
nuclear@1 387 for (n = 1; n < GF2_DIM; n++) {
nuclear@1 388 odd[n] = row;
nuclear@1 389 row <<= 1;
nuclear@1 390 }
nuclear@1 391
nuclear@1 392 /* put operator for two zero bits in even */
nuclear@1 393 gf2_matrix_square(even, odd);
nuclear@1 394
nuclear@1 395 /* put operator for four zero bits in odd */
nuclear@1 396 gf2_matrix_square(odd, even);
nuclear@1 397
nuclear@1 398 /* apply len2 zeros to crc1 (first square will put the operator for one
nuclear@1 399 zero byte, eight zero bits, in even) */
nuclear@1 400 do {
nuclear@1 401 /* apply zeros operator for this bit of len2 */
nuclear@1 402 gf2_matrix_square(even, odd);
nuclear@1 403 if (len2 & 1)
nuclear@1 404 crc1 = gf2_matrix_times(even, crc1);
nuclear@1 405 len2 >>= 1;
nuclear@1 406
nuclear@1 407 /* if no more bits set, then done */
nuclear@1 408 if (len2 == 0)
nuclear@1 409 break;
nuclear@1 410
nuclear@1 411 /* another iteration of the loop with odd and even swapped */
nuclear@1 412 gf2_matrix_square(odd, even);
nuclear@1 413 if (len2 & 1)
nuclear@1 414 crc1 = gf2_matrix_times(odd, crc1);
nuclear@1 415 len2 >>= 1;
nuclear@1 416
nuclear@1 417 /* if no more bits set, then done */
nuclear@1 418 } while (len2 != 0);
nuclear@1 419
nuclear@1 420 /* return combined crc */
nuclear@1 421 crc1 ^= crc2;
nuclear@1 422 return crc1;
nuclear@1 423 }