usr/src/uts/common/zmod/crc32.c

   1 /*
   2  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
   3  * Use is subject to license terms.
   4  */
   5
   6 /* crc32.c -- compute the CRC-32 of a data stream
   7  * Copyright (C) 1995-2005 Mark Adler
   8  * For conditions of distribution and use, see copyright notice in zlib.h
   9  *
  10  * Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster
  11  * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
  12  * tables for updating the shift register in one step with three exclusive-ors
  13  * instead of four steps with four exclusive-ors.  This results in about a
  14  * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
  15  */
  16
  17 #pragma ident   "%Z%%M% %I%     %E% SMI"
  18
  19 /*
  20   Note on the use of DYNAMIC_CRC_TABLE: there is no mutex or semaphore
  21   protection on the static variables used to control the first-use generation
  22   of the crc tables.  Therefore, if you #define DYNAMIC_CRC_TABLE, you should
  23   first call get_crc_table() to initialize the tables before allowing more than
  24   one thread to use crc32().
  25  */
  26
  27 #ifdef MAKECRCH
  28 #  include <stdio.h>
  29 #  ifndef DYNAMIC_CRC_TABLE
  30 #    define DYNAMIC_CRC_TABLE
  31 #  endif /* !DYNAMIC_CRC_TABLE */
  32 #endif /* MAKECRCH */
  33
  34 #include "zutil.h"      /* for STDC and FAR definitions */
  35
  36 #define local static
  37
  38 /* Find a four-byte integer type for crc32_little() and crc32_big(). */
  39 #ifndef NOBYFOUR
  40 #  ifdef STDC           /* need ANSI C limits.h to determine sizes */
  41 #    include <limits.h>
  42 #    define BYFOUR
  43 #    if (UINT_MAX == 0xffffffffUL)
  44        typedef unsigned int u4;
  45 #    else
  46 #      if (ULONG_MAX == 0xffffffffUL)
  47          typedef unsigned long u4;
  48 #      else
  49 #        if (USHRT_MAX == 0xffffffffUL)
  50            typedef unsigned short u4;
  51 #        else
  52 #          undef BYFOUR     /* can't find a four-byte integer type! */
  53 #        endif
  54 #      endif
  55 #    endif
  56 #  endif /* STDC */
  57 #endif /* !NOBYFOUR */
  58
  59 /* Definitions for doing the crc four data bytes at a time. */
  60 #ifdef BYFOUR
  61 #  define REV(w) (((w)>>24)+(((w)>>8)&0xff00)+ \
  62                 (((w)&0xff00)<<8)+(((w)&0xff)<<24))
  63    local unsigned long crc32_little OF((unsigned long,
  64                         const unsigned char FAR *, unsigned));
  65    local unsigned long crc32_big OF((unsigned long,
  66                         const unsigned char FAR *, unsigned));
  67 #  define TBLS 8
  68 #else
  69 #  define TBLS 1
  70 #endif /* BYFOUR */
  71
  72 /* Local functions for crc concatenation */
  73 local unsigned long gf2_matrix_times OF((unsigned long *mat,
  74                                          unsigned long vec));
  75 local void gf2_matrix_square OF((unsigned long *square, unsigned long *mat));
  76
  77 #ifdef DYNAMIC_CRC_TABLE
  78
  79 local volatile int crc_table_empty = 1;
  80 local unsigned long FAR crc_table[TBLS][256];
  81 local void make_crc_table OF((void));
  82 #ifdef MAKECRCH
  83    local void write_table OF((FILE *, const unsigned long FAR *));
  84 #endif /* MAKECRCH */
  85 /*
  86   Generate tables for a byte-wise 32-bit CRC calculation on the polynomial:
  87   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.
  88
  89   Polynomials over GF(2) are represented in binary, one bit per coefficient,
  90   with the lowest powers in the most significant bit.  Then adding polynomials
  91   is just exclusive-or, and multiplying a polynomial by x is a right shift by
  92   one.  If we call the above polynomial p, and represent a byte as the
  93   polynomial q, also with the lowest power in the most significant bit (so the
  94   byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
  95   where a mod b means the remainder after dividing a by b.
  96
  97   This calculation is done using the shift-register method of multiplying and
  98   taking the remainder.  The register is initialized to zero, and for each
  99   incoming bit, x^32 is added mod p to the register if the bit is a one (where
 100   x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
 101   x (which is shifting right by one and adding x^32 mod p if the bit shifted
 102   out is a one).  We start with the highest power (least significant bit) of
 103   q and repeat for all eight bits of q.
 104
 105   The first table is simply the CRC of all possible eight bit values.  This is
 106   all the information needed to generate CRCs on data a byte at a time for all
 107   combinations of CRC register values and incoming bytes.  The remaining tables
 108   allow for word-at-a-time CRC calculation for both big-endian and little-
 109   endian machines, where a word is four bytes.
 110 */
 111 local void make_crc_table()
 112 {
 113     unsigned long c;
 114     int n, k;
 115     unsigned long poly;                 /* polynomial exclusive-or pattern */
 116     /* terms of polynomial defining this crc (except x^32): */
 117     static volatile int first = 1;      /* flag to limit concurrent making */
 118     static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
 119
 120     /* See if another task is already doing this (not thread-safe, but better
 121        than nothing -- significantly reduces duration of vulnerability in
 122        case the advice about DYNAMIC_CRC_TABLE is ignored) */
 123     if (first) {
 124         first = 0;
 125
 126         /* make exclusive-or pattern from polynomial (0xedb88320UL) */
 127         poly = 0UL;
 128         for (n = 0; n < sizeof(p)/sizeof(unsigned char); n++)
 129             poly |= 1UL << (31 - p[n]);
 130
 131         /* generate a crc for every 8-bit value */
 132         for (n = 0; n < 256; n++) {
 133             c = (unsigned long)n;
 134             for (k = 0; k < 8; k++)
 135                 c = c & 1 ? poly ^ (c >> 1) : c >> 1;
 136             crc_table[0][n] = c;
 137         }
 138
 139 #ifdef BYFOUR
 140         /* generate crc for each value followed by one, two, and three zeros,
 141            and then the byte reversal of those as well as the first table */
 142         for (n = 0; n < 256; n++) {
 143             c = crc_table[0][n];
 144             crc_table[4][n] = REV(c);
 145             for (k = 1; k < 4; k++) {
 146                 c = crc_table[0][c & 0xff] ^ (c >> 8);
 147                 crc_table[k][n] = c;
 148                 crc_table[k + 4][n] = REV(c);
 149             }
 150         }
 151 #endif /* BYFOUR */
 152
 153         crc_table_empty = 0;
 154     }
 155     else {      /* not first */
 156         /* wait for the other guy to finish (not efficient, but rare) */
 157         while (crc_table_empty)
 158             ;
 159     }
 160
 161 #ifdef MAKECRCH
 162     /* write out CRC tables to crc32.h */
 163     {
 164         FILE *out;
 165
 166         out = fopen("crc32.h", "w");
 167         if (out == NULL) return;
 168         fprintf(out, "/* crc32.h -- tables for rapid CRC calculation\n");
 169         fprintf(out, " * Generated automatically by crc32.c\n */\n\n");
 170         fprintf(out, "local const unsigned long FAR ");
 171         fprintf(out, "crc_table[TBLS][256] =\n{\n  {\n");
 172         write_table(out, crc_table[0]);
 173 #  ifdef BYFOUR
 174         fprintf(out, "#ifdef BYFOUR\n");
 175         for (k = 1; k < 8; k++) {
 176             fprintf(out, "  },\n  {\n");
 177             write_table(out, crc_table[k]);
 178         }
 179         fprintf(out, "#endif\n");
 180 #  endif /* BYFOUR */
 181         fprintf(out, "  }\n};\n");
 182         fclose(out);
 183     }
 184 #endif /* MAKECRCH */
 185 }
 186
 187 #ifdef MAKECRCH
 188 local void write_table(out, table)
 189     FILE *out;
 190     const unsigned long FAR *table;
 191 {
 192     int n;
 193
 194     for (n = 0; n < 256; n++)
 195         fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : "    ", table[n],
 196                 n == 255 ? "\n" : (n % 5 == 4 ? ",\n" : ", "));
 197 }
 198 #endif /* MAKECRCH */
 199
 200 #else /* !DYNAMIC_CRC_TABLE */
 201 /* ========================================================================
 202  * Tables of CRC-32s of all single-byte values, made by make_crc_table().
 203  */
 204 #include "crc32.h"
 205 #endif /* DYNAMIC_CRC_TABLE */
 206
 207 /* =========================================================================
 208  * This function can be used by asm versions of crc32()
 209  */
 210 const unsigned long FAR * ZEXPORT get_crc_table()
 211 {
 212 #ifdef DYNAMIC_CRC_TABLE
 213     if (crc_table_empty)
 214         make_crc_table();
 215 #endif /* DYNAMIC_CRC_TABLE */
 216     return (const unsigned long FAR *)crc_table;
 217 }
 218
 219 /* ========================================================================= */
 220 #define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8)
 221 #define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1
 222
 223 /* ========================================================================= */
 224 unsigned long ZEXPORT crc32(crc, buf, len)
 225     unsigned long crc;
 226     const unsigned char FAR *buf;
 227     unsigned len;
 228 {
 229     if (buf == Z_NULL) return 0UL;
 230
 231 #ifdef DYNAMIC_CRC_TABLE
 232     if (crc_table_empty)
 233         make_crc_table();
 234 #endif /* DYNAMIC_CRC_TABLE */
 235
 236 #ifdef BYFOUR
 237     if (sizeof(void *) == sizeof(ptrdiff_t)) {
 238         u4 endian;
 239
 240         endian = 1;
 241         if (*((unsigned char *)(&endian)))
 242             return crc32_little(crc, buf, len);
 243         else
 244             return crc32_big(crc, buf, len);
 245     }
 246 #endif /* BYFOUR */
 247     crc = crc ^ 0xffffffffUL;
 248     while (len >= 8) {
 249         DO8;
 250         len -= 8;
 251     }
 252     if (len) do {
 253         DO1;
 254     } while (--len);
 255     return crc ^ 0xffffffffUL;
 256 }
 257
 258 #ifdef BYFOUR
 259
 260 /* ========================================================================= */
 261 #define DOLIT4 c ^= *buf4++; \
 262         c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \
 263             crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24]
 264 #define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4
 265
 266 /* ========================================================================= */
 267 local unsigned long crc32_little(crc, buf, len)
 268     unsigned long crc;
 269     const unsigned char FAR *buf;
 270     unsigned len;
 271 {
 272     register u4 c;
 273     register const u4 FAR *buf4;
 274
 275     c = (u4)crc;
 276     c = ~c;
 277     while (len && ((ptrdiff_t)buf & 3)) {
 278         c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
 279         len--;
 280     }
 281
 282     buf4 = (const u4 FAR *)(const void FAR *)buf;
 283     while (len >= 32) {
 284         DOLIT32;
 285         len -= 32;
 286     }
 287     while (len >= 4) {
 288         DOLIT4;
 289         len -= 4;
 290     }
 291     buf = (const unsigned char FAR *)buf4;
 292
 293     if (len) do {
 294         c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
 295     } while (--len);
 296     c = ~c;
 297     return (unsigned long)c;
 298 }
 299
 300 /* ========================================================================= */
 301 #define DOBIG4 c ^= *++buf4; \
 302         c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \
 303             crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24]
 304 #define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4
 305
 306 /* ========================================================================= */
 307 local unsigned long crc32_big(crc, buf, len)
 308     unsigned long crc;
 309     const unsigned char FAR *buf;
 310     unsigned len;
 311 {
 312     register u4 c;
 313     register const u4 FAR *buf4;
 314
 315     c = REV((u4)crc);
 316     c = ~c;
 317     while (len && ((ptrdiff_t)buf & 3)) {
 318         c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
 319         len--;
 320     }
 321
 322     buf4 = (const u4 FAR *)(const void FAR *)buf;
 323     buf4--;
 324     while (len >= 32) {
 325         DOBIG32;
 326         len -= 32;
 327     }
 328     while (len >= 4) {
 329         DOBIG4;
 330         len -= 4;
 331     }
 332     buf4++;
 333     buf = (const unsigned char FAR *)buf4;
 334
 335     if (len) do {
 336         c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
 337     } while (--len);
 338     c = ~c;
 339     return (unsigned long)(REV(c));
 340 }
 341
 342 #endif /* BYFOUR */
 343
 344 #define GF2_DIM 32      /* dimension of GF(2) vectors (length of CRC) */
 345
 346 /* ========================================================================= */
 347 local unsigned long gf2_matrix_times(mat, vec)
 348     unsigned long *mat;
 349     unsigned long vec;
 350 {
 351     unsigned long sum;
 352
 353     sum = 0;
 354     while (vec) {
 355         if (vec & 1)
 356             sum ^= *mat;
 357         vec >>= 1;
 358         mat++;
 359     }
 360     return sum;
 361 }
 362
 363 /* ========================================================================= */
 364 local void gf2_matrix_square(square, mat)
 365     unsigned long *square;
 366     unsigned long *mat;
 367 {
 368     int n;
 369
 370     for (n = 0; n < GF2_DIM; n++)
 371         square[n] = gf2_matrix_times(mat, mat[n]);
 372 }
 373
 374 /* ========================================================================= */
 375 uLong ZEXPORT crc32_combine(crc1, crc2, len2)
 376     uLong crc1;
 377     uLong crc2;
 378     z_off_t len2;
 379 {
 380     int n;
 381     unsigned long row;
 382     unsigned long even[GF2_DIM];    /* even-power-of-two zeros operator */
 383     unsigned long odd[GF2_DIM];     /* odd-power-of-two zeros operator */
 384
 385     /* degenerate case */
 386     if (len2 == 0)
 387         return crc1;
 388
 389     /* put operator for one zero bit in odd */
 390     odd[0] = 0xedb88320UL;          /* CRC-32 polynomial */
 391     row = 1;
 392     for (n = 1; n < GF2_DIM; n++) {
 393         odd[n] = row;
 394         row <<= 1;
 395     }
 396
 397     /* put operator for two zero bits in even */
 398     gf2_matrix_square(even, odd);
 399
 400     /* put operator for four zero bits in odd */
 401     gf2_matrix_square(odd, even);
 402
 403     /* apply len2 zeros to crc1 (first square will put the operator for one
 404        zero byte, eight zero bits, in even) */
 405     do {
 406         /* apply zeros operator for this bit of len2 */
 407         gf2_matrix_square(even, odd);
 408         if (len2 & 1)
 409             crc1 = gf2_matrix_times(even, crc1);
 410         len2 >>= 1;
 411
 412         /* if no more bits set, then done */
 413         if (len2 == 0)
 414             break;
 415
 416         /* another iteration of the loop with odd and even swapped */
 417         gf2_matrix_square(odd, even);
 418         if (len2 & 1)
 419             crc1 = gf2_matrix_times(odd, crc1);
 420         len2 >>= 1;
 421
 422         /* if no more bits set, then done */
 423     } while (len2 != 0);
 424
 425     /* return combined crc */
 426     crc1 ^= crc2;
 427     return crc1;
 428 }