The Tor Browser / file comparison
comparison: modules/zlib/src/crc32.c
modules/zlib/src/crc32.c
- branch
- TOR_BUG_3246
- changeset 7
- 129ffea94266
equal
deleted
inserted
replaced
| -1:000000000000 | 0:b4d65478f847 |
|---|---|
| 1 /* crc32.c -- compute the CRC-32 of a data stream | |
| 2 * Copyright (C) 1995-2006, 2010, 2011, 2012 Mark Adler | |
| 3 * For conditions of distribution and use, see copyright notice in zlib.h | |
| 4 * | |
| 5 * Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster | |
| 6 * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing | |
| 7 * tables for updating the shift register in one step with three exclusive-ors | |
| 8 * instead of four steps with four exclusive-ors. This results in about a | |
| 9 * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3. | |
| 10 */ | |
| 11 | |
| 12 /* @(#) $Id$ */ | |
| 13 | |
| 14 /* | |
| 15 Note on the use of DYNAMIC_CRC_TABLE: there is no mutex or semaphore | |
| 16 protection on the static variables used to control the first-use generation | |
| 17 of the crc tables. Therefore, if you #define DYNAMIC_CRC_TABLE, you should | |
| 18 first call get_crc_table() to initialize the tables before allowing more than | |
| 19 one thread to use crc32(). | |
| 20 | |
| 21 DYNAMIC_CRC_TABLE and MAKECRCH can be #defined to write out crc32.h. | |
| 22 */ | |
| 23 | |
| 24 #ifdef MAKECRCH | |
| 25 # include <stdio.h> | |
| 26 # ifndef DYNAMIC_CRC_TABLE | |
| 27 # define DYNAMIC_CRC_TABLE | |
| 28 # endif /* !DYNAMIC_CRC_TABLE */ | |
| 29 #endif /* MAKECRCH */ | |
| 30 | |
| 31 #include "zutil.h" /* for STDC and FAR definitions */ | |
| 32 | |
| 33 #define local static | |
| 34 | |
| 35 /* Definitions for doing the crc four data bytes at a time. */ | |
| 36 #if !defined(NOBYFOUR) && defined(Z_U4) | |
| 37 # define BYFOUR | |
| 38 #endif | |
| 39 #ifdef BYFOUR | |
| 40 local unsigned long crc32_little OF((unsigned long, | |
| 41 const unsigned char FAR *, unsigned)); | |
| 42 local unsigned long crc32_big OF((unsigned long, | |
| 43 const unsigned char FAR *, unsigned)); | |
| 44 # define TBLS 8 | |
| 45 #else | |
| 46 # define TBLS 1 | |
| 47 #endif /* BYFOUR */ | |
| 48 | |
| 49 /* Local functions for crc concatenation */ | |
| 50 local unsigned long gf2_matrix_times OF((unsigned long *mat, | |
| 51 unsigned long vec)); | |
| 52 local void gf2_matrix_square OF((unsigned long *square, unsigned long *mat)); | |
| 53 local uLong crc32_combine_ OF((uLong crc1, uLong crc2, z_off64_t len2)); | |
| 54 | |
| 55 | |
| 56 #ifdef DYNAMIC_CRC_TABLE | |
| 57 | |
| 58 local volatile int crc_table_empty = 1; | |
| 59 local z_crc_t FAR crc_table[TBLS][256]; | |
| 60 local void make_crc_table OF((void)); | |
| 61 #ifdef MAKECRCH | |
| 62 local void write_table OF((FILE *, const z_crc_t FAR *)); | |
| 63 #endif /* MAKECRCH */ | |
| 64 /* | |
| 65 Generate tables for a byte-wise 32-bit CRC calculation on the polynomial: | |
| 66 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. | |
| 67 | |
| 68 Polynomials over GF(2) are represented in binary, one bit per coefficient, | |
| 69 with the lowest powers in the most significant bit. Then adding polynomials | |
| 70 is just exclusive-or, and multiplying a polynomial by x is a right shift by | |
| 71 one. If we call the above polynomial p, and represent a byte as the | |
| 72 polynomial q, also with the lowest power in the most significant bit (so the | |
| 73 byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p, | |
| 74 where a mod b means the remainder after dividing a by b. | |
| 75 | |
| 76 This calculation is done using the shift-register method of multiplying and | |
| 77 taking the remainder. The register is initialized to zero, and for each | |
| 78 incoming bit, x^32 is added mod p to the register if the bit is a one (where | |
| 79 x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by | |
| 80 x (which is shifting right by one and adding x^32 mod p if the bit shifted | |
| 81 out is a one). We start with the highest power (least significant bit) of | |
| 82 q and repeat for all eight bits of q. | |
| 83 | |
| 84 The first table is simply the CRC of all possible eight bit values. This is | |
| 85 all the information needed to generate CRCs on data a byte at a time for all | |
| 86 combinations of CRC register values and incoming bytes. The remaining tables | |
| 87 allow for word-at-a-time CRC calculation for both big-endian and little- | |
| 88 endian machines, where a word is four bytes. | |
| 89 */ | |
| 90 local void make_crc_table() | |
| 91 { | |
| 92 z_crc_t c; | |
| 93 int n, k; | |
| 94 z_crc_t poly; /* polynomial exclusive-or pattern */ | |
| 95 /* terms of polynomial defining this crc (except x^32): */ | |
| 96 static volatile int first = 1; /* flag to limit concurrent making */ | |
| 97 static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26}; | |
| 98 | |
| 99 /* See if another task is already doing this (not thread-safe, but better | |
| 100 than nothing -- significantly reduces duration of vulnerability in | |
| 101 case the advice about DYNAMIC_CRC_TABLE is ignored) */ | |
| 102 if (first) { | |
| 103 first = 0; | |
| 104 | |
| 105 /* make exclusive-or pattern from polynomial (0xedb88320UL) */ | |
| 106 poly = 0; | |
| 107 for (n = 0; n < (int)(sizeof(p)/sizeof(unsigned char)); n++) | |
| 108 poly |= (z_crc_t)1 << (31 - p[n]); | |
| 109 | |
| 110 /* generate a crc for every 8-bit value */ | |
| 111 for (n = 0; n < 256; n++) { | |
| 112 c = (z_crc_t)n; | |
| 113 for (k = 0; k < 8; k++) | |
| 114 c = c & 1 ? poly ^ (c >> 1) : c >> 1; | |
| 115 crc_table[0][n] = c; | |
| 116 } | |
| 117 | |
| 118 #ifdef BYFOUR | |
| 119 /* generate crc for each value followed by one, two, and three zeros, | |
| 120 and then the byte reversal of those as well as the first table */ | |
| 121 for (n = 0; n < 256; n++) { | |
| 122 c = crc_table[0][n]; | |
| 123 crc_table[4][n] = ZSWAP32(c); | |
| 124 for (k = 1; k < 4; k++) { | |
| 125 c = crc_table[0][c & 0xff] ^ (c >> 8); | |
| 126 crc_table[k][n] = c; | |
| 127 crc_table[k + 4][n] = ZSWAP32(c); | |
| 128 } | |
| 129 } | |
| 130 #endif /* BYFOUR */ | |
| 131 | |
| 132 crc_table_empty = 0; | |
| 133 } | |
| 134 else { /* not first */ | |
| 135 /* wait for the other guy to finish (not efficient, but rare) */ | |
| 136 while (crc_table_empty) | |
| 137 ; | |
| 138 } | |
| 139 | |
| 140 #ifdef MAKECRCH | |
| 141 /* write out CRC tables to crc32.h */ | |
| 142 { | |
| 143 FILE *out; | |
| 144 | |
| 145 out = fopen("crc32.h", "w"); | |
| 146 if (out == NULL) return; | |
| 147 fprintf(out, "/* crc32.h -- tables for rapid CRC calculation\n"); | |
| 148 fprintf(out, " * Generated automatically by crc32.c\n */\n\n"); | |
| 149 fprintf(out, "local const z_crc_t FAR "); | |
| 150 fprintf(out, "crc_table[TBLS][256] =\n{\n {\n"); | |
| 151 write_table(out, crc_table[0]); | |
| 152 # ifdef BYFOUR | |
| 153 fprintf(out, "#ifdef BYFOUR\n"); | |
| 154 for (k = 1; k < 8; k++) { | |
| 155 fprintf(out, " },\n {\n"); | |
| 156 write_table(out, crc_table[k]); | |
| 157 } | |
| 158 fprintf(out, "#endif\n"); | |
| 159 # endif /* BYFOUR */ | |
| 160 fprintf(out, " }\n};\n"); | |
| 161 fclose(out); | |
| 162 } | |
| 163 #endif /* MAKECRCH */ | |
| 164 } | |
| 165 | |
| 166 #ifdef MAKECRCH | |
| 167 local void write_table(out, table) | |
| 168 FILE *out; | |
| 169 const z_crc_t FAR *table; | |
| 170 { | |
| 171 int n; | |
| 172 | |
| 173 for (n = 0; n < 256; n++) | |
| 174 fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : " ", | |
| 175 (unsigned long)(table[n]), | |
| 176 n == 255 ? "\n" : (n % 5 == 4 ? ",\n" : ", ")); | |
| 177 } | |
| 178 #endif /* MAKECRCH */ | |
| 179 | |
| 180 #else /* !DYNAMIC_CRC_TABLE */ | |
| 181 /* ======================================================================== | |
| 182 * Tables of CRC-32s of all single-byte values, made by make_crc_table(). | |
| 183 */ | |
| 184 #include "crc32.h" | |
| 185 #endif /* DYNAMIC_CRC_TABLE */ | |
| 186 | |
| 187 /* ========================================================================= | |
| 188 * This function can be used by asm versions of crc32() | |
| 189 */ | |
| 190 const z_crc_t FAR * ZEXPORT get_crc_table() | |
| 191 { | |
| 192 #ifdef DYNAMIC_CRC_TABLE | |
| 193 if (crc_table_empty) | |
| 194 make_crc_table(); | |
| 195 #endif /* DYNAMIC_CRC_TABLE */ | |
| 196 return (const z_crc_t FAR *)crc_table; | |
| 197 } | |
| 198 | |
| 199 /* ========================================================================= */ | |
| 200 #define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8) | |
| 201 #define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1 | |
| 202 | |
| 203 /* ========================================================================= */ | |
| 204 unsigned long ZEXPORT crc32(crc, buf, len) | |
| 205 unsigned long crc; | |
| 206 const unsigned char FAR *buf; | |
| 207 uInt len; | |
| 208 { | |
| 209 if (buf == Z_NULL) return 0UL; | |
| 210 | |
| 211 #ifdef DYNAMIC_CRC_TABLE | |
| 212 if (crc_table_empty) | |
| 213 make_crc_table(); | |
| 214 #endif /* DYNAMIC_CRC_TABLE */ | |
| 215 | |
| 216 #ifdef BYFOUR | |
| 217 if (sizeof(void *) == sizeof(ptrdiff_t)) { | |
| 218 z_crc_t endian; | |
| 219 | |
| 220 endian = 1; | |
| 221 if (*((unsigned char *)(&endian))) | |
| 222 return crc32_little(crc, buf, len); | |
| 223 else | |
| 224 return crc32_big(crc, buf, len); | |
| 225 } | |
| 226 #endif /* BYFOUR */ | |
| 227 crc = crc ^ 0xffffffffUL; | |
| 228 while (len >= 8) { | |
| 229 DO8; | |
| 230 len -= 8; | |
| 231 } | |
| 232 if (len) do { | |
| 233 DO1; | |
| 234 } while (--len); | |
| 235 return crc ^ 0xffffffffUL; | |
| 236 } | |
| 237 | |
| 238 #ifdef BYFOUR | |
| 239 | |
| 240 /* ========================================================================= */ | |
| 241 #define DOLIT4 c ^= *buf4++; \ | |
| 242 c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \ | |
| 243 crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24] | |
| 244 #define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4 | |
| 245 | |
| 246 /* ========================================================================= */ | |
| 247 local unsigned long crc32_little(crc, buf, len) | |
| 248 unsigned long crc; | |
| 249 const unsigned char FAR *buf; | |
| 250 unsigned len; | |
| 251 { | |
| 252 register z_crc_t c; | |
| 253 register const z_crc_t FAR *buf4; | |
| 254 | |
| 255 c = (z_crc_t)crc; | |
| 256 c = ~c; | |
| 257 while (len && ((ptrdiff_t)buf & 3)) { | |
| 258 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8); | |
| 259 len--; | |
| 260 } | |
| 261 | |
| 262 buf4 = (const z_crc_t FAR *)(const void FAR *)buf; | |
| 263 while (len >= 32) { | |
| 264 DOLIT32; | |
| 265 len -= 32; | |
| 266 } | |
| 267 while (len >= 4) { | |
| 268 DOLIT4; | |
| 269 len -= 4; | |
| 270 } | |
| 271 buf = (const unsigned char FAR *)buf4; | |
| 272 | |
| 273 if (len) do { | |
| 274 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8); | |
| 275 } while (--len); | |
| 276 c = ~c; | |
| 277 return (unsigned long)c; | |
| 278 } | |
| 279 | |
| 280 /* ========================================================================= */ | |
| 281 #define DOBIG4 c ^= *++buf4; \ | |
| 282 c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \ | |
| 283 crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24] | |
| 284 #define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4 | |
| 285 | |
| 286 /* ========================================================================= */ | |
| 287 local unsigned long crc32_big(crc, buf, len) | |
| 288 unsigned long crc; | |
| 289 const unsigned char FAR *buf; | |
| 290 unsigned len; | |
| 291 { | |
| 292 register z_crc_t c; | |
| 293 register const z_crc_t FAR *buf4; | |
| 294 | |
| 295 c = ZSWAP32((z_crc_t)crc); | |
| 296 c = ~c; | |
| 297 while (len && ((ptrdiff_t)buf & 3)) { | |
| 298 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8); | |
| 299 len--; | |
| 300 } | |
| 301 | |
| 302 buf4 = (const z_crc_t FAR *)(const void FAR *)buf; | |
| 303 buf4--; | |
| 304 while (len >= 32) { | |
| 305 DOBIG32; | |
| 306 len -= 32; | |
| 307 } | |
| 308 while (len >= 4) { | |
| 309 DOBIG4; | |
| 310 len -= 4; | |
| 311 } | |
| 312 buf4++; | |
| 313 buf = (const unsigned char FAR *)buf4; | |
| 314 | |
| 315 if (len) do { | |
| 316 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8); | |
| 317 } while (--len); | |
| 318 c = ~c; | |
| 319 return (unsigned long)(ZSWAP32(c)); | |
| 320 } | |
| 321 | |
| 322 #endif /* BYFOUR */ | |
| 323 | |
| 324 #define GF2_DIM 32 /* dimension of GF(2) vectors (length of CRC) */ | |
| 325 | |
| 326 /* ========================================================================= */ | |
| 327 local unsigned long gf2_matrix_times(mat, vec) | |
| 328 unsigned long *mat; | |
| 329 unsigned long vec; | |
| 330 { | |
| 331 unsigned long sum; | |
| 332 | |
| 333 sum = 0; | |
| 334 while (vec) { | |
| 335 if (vec & 1) | |
| 336 sum ^= *mat; | |
| 337 vec >>= 1; | |
| 338 mat++; | |
| 339 } | |
| 340 return sum; | |
| 341 } | |
| 342 | |
| 343 /* ========================================================================= */ | |
| 344 local void gf2_matrix_square(square, mat) | |
| 345 unsigned long *square; | |
| 346 unsigned long *mat; | |
| 347 { | |
| 348 int n; | |
| 349 | |
| 350 for (n = 0; n < GF2_DIM; n++) | |
| 351 square[n] = gf2_matrix_times(mat, mat[n]); | |
| 352 } | |
| 353 | |
| 354 /* ========================================================================= */ | |
| 355 local uLong crc32_combine_(crc1, crc2, len2) | |
| 356 uLong crc1; | |
| 357 uLong crc2; | |
| 358 z_off64_t len2; | |
| 359 { | |
| 360 int n; | |
| 361 unsigned long row; | |
| 362 unsigned long even[GF2_DIM]; /* even-power-of-two zeros operator */ | |
| 363 unsigned long odd[GF2_DIM]; /* odd-power-of-two zeros operator */ | |
| 364 | |
| 365 /* degenerate case (also disallow negative lengths) */ | |
| 366 if (len2 <= 0) | |
| 367 return crc1; | |
| 368 | |
| 369 /* put operator for one zero bit in odd */ | |
| 370 odd[0] = 0xedb88320UL; /* CRC-32 polynomial */ | |
| 371 row = 1; | |
| 372 for (n = 1; n < GF2_DIM; n++) { | |
| 373 odd[n] = row; | |
| 374 row <<= 1; | |
| 375 } | |
| 376 | |
| 377 /* put operator for two zero bits in even */ | |
| 378 gf2_matrix_square(even, odd); | |
| 379 | |
| 380 /* put operator for four zero bits in odd */ | |
| 381 gf2_matrix_square(odd, even); | |
| 382 | |
| 383 /* apply len2 zeros to crc1 (first square will put the operator for one | |
| 384 zero byte, eight zero bits, in even) */ | |
| 385 do { | |
| 386 /* apply zeros operator for this bit of len2 */ | |
| 387 gf2_matrix_square(even, odd); | |
| 388 if (len2 & 1) | |
| 389 crc1 = gf2_matrix_times(even, crc1); | |
| 390 len2 >>= 1; | |
| 391 | |
| 392 /* if no more bits set, then done */ | |
| 393 if (len2 == 0) | |
| 394 break; | |
| 395 | |
| 396 /* another iteration of the loop with odd and even swapped */ | |
| 397 gf2_matrix_square(odd, even); | |
| 398 if (len2 & 1) | |
| 399 crc1 = gf2_matrix_times(odd, crc1); | |
| 400 len2 >>= 1; | |
| 401 | |
| 402 /* if no more bits set, then done */ | |
| 403 } while (len2 != 0); | |
| 404 | |
| 405 /* return combined crc */ | |
| 406 crc1 ^= crc2; | |
| 407 return crc1; | |
| 408 } | |
| 409 | |
| 410 /* ========================================================================= */ | |
| 411 uLong ZEXPORT crc32_combine(crc1, crc2, len2) | |
| 412 uLong crc1; | |
| 413 uLong crc2; | |
| 414 z_off_t len2; | |
| 415 { | |
| 416 return crc32_combine_(crc1, crc2, len2); | |
| 417 } | |
| 418 | |
| 419 uLong ZEXPORT crc32_combine64(crc1, crc2, len2) | |
| 420 uLong crc1; | |
| 421 uLong crc2; | |
| 422 z_off64_t len2; | |
| 423 { | |
| 424 return crc32_combine_(crc1, crc2, len2); | |
| 425 } |
