nuclear@0: /* crc32.c -- compute the CRC-32 of a data stream nuclear@0: * Copyright (C) 1995-2005 Mark Adler nuclear@0: * For conditions of distribution and use, see copyright notice in zlib.h nuclear@0: * nuclear@0: * Thanks to Rodney Brown for his contribution of faster nuclear@0: * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing nuclear@0: * tables for updating the shift register in one step with three exclusive-ors nuclear@0: * instead of four steps with four exclusive-ors. This results in about a nuclear@0: * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3. nuclear@0: */ nuclear@0: nuclear@0: /* @(#) $Id$ */ nuclear@0: nuclear@0: /* nuclear@0: Note on the use of DYNAMIC_CRC_TABLE: there is no mutex or semaphore nuclear@0: protection on the static variables used to control the first-use generation nuclear@0: of the crc tables. Therefore, if you #define DYNAMIC_CRC_TABLE, you should nuclear@0: first call get_crc_table() to initialize the tables before allowing more than nuclear@0: one thread to use crc32(). nuclear@0: */ nuclear@0: nuclear@0: #ifdef MAKECRCH nuclear@0: # include nuclear@0: # ifndef DYNAMIC_CRC_TABLE nuclear@0: # define DYNAMIC_CRC_TABLE nuclear@0: # endif /* !DYNAMIC_CRC_TABLE */ nuclear@0: #endif /* MAKECRCH */ nuclear@0: nuclear@0: #include "zutil.h" /* for STDC and FAR definitions */ nuclear@0: nuclear@0: #define local static nuclear@0: nuclear@0: /* Find a four-byte integer type for crc32_little() and crc32_big(). */ nuclear@0: #ifndef NOBYFOUR nuclear@0: # ifdef STDC /* need ANSI C limits.h to determine sizes */ nuclear@0: # include nuclear@0: # define BYFOUR nuclear@0: # if (UINT_MAX == 0xffffffffUL) nuclear@0: typedef unsigned int u4; nuclear@0: # else nuclear@0: # if (ULONG_MAX == 0xffffffffUL) nuclear@0: typedef unsigned long u4; nuclear@0: # else nuclear@0: # if (USHRT_MAX == 0xffffffffUL) nuclear@0: typedef unsigned short u4; nuclear@0: # else nuclear@0: # undef BYFOUR /* can't find a four-byte integer type! */ nuclear@0: # endif nuclear@0: # endif nuclear@0: # endif nuclear@0: # endif /* STDC */ nuclear@0: #endif /* !NOBYFOUR */ nuclear@0: nuclear@0: /* Definitions for doing the crc four data bytes at a time. */ nuclear@0: #ifdef BYFOUR nuclear@0: # define REV(w) (((w)>>24)+(((w)>>8)&0xff00)+ \ nuclear@0: (((w)&0xff00)<<8)+(((w)&0xff)<<24)) nuclear@0: local unsigned long crc32_little OF((unsigned long, nuclear@0: const unsigned char FAR *, unsigned)); nuclear@0: local unsigned long crc32_big OF((unsigned long, nuclear@0: const unsigned char FAR *, unsigned)); nuclear@0: # define TBLS 8 nuclear@0: #else nuclear@0: # define TBLS 1 nuclear@0: #endif /* BYFOUR */ nuclear@0: nuclear@0: /* Local functions for crc concatenation */ nuclear@0: local unsigned long gf2_matrix_times OF((unsigned long *mat, nuclear@0: unsigned long vec)); nuclear@0: local void gf2_matrix_square OF((unsigned long *square, unsigned long *mat)); nuclear@0: nuclear@0: #ifdef DYNAMIC_CRC_TABLE nuclear@0: nuclear@0: local volatile int crc_table_empty = 1; nuclear@0: local unsigned long FAR crc_table[TBLS][256]; nuclear@0: local void make_crc_table OF((void)); nuclear@0: #ifdef MAKECRCH nuclear@0: local void write_table OF((FILE *, const unsigned long FAR *)); nuclear@0: #endif /* MAKECRCH */ nuclear@0: /* nuclear@0: Generate tables for a byte-wise 32-bit CRC calculation on the polynomial: nuclear@0: 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@0: nuclear@0: Polynomials over GF(2) are represented in binary, one bit per coefficient, nuclear@0: with the lowest powers in the most significant bit. Then adding polynomials nuclear@0: is just exclusive-or, and multiplying a polynomial by x is a right shift by nuclear@0: one. If we call the above polynomial p, and represent a byte as the nuclear@0: polynomial q, also with the lowest power in the most significant bit (so the nuclear@0: byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p, nuclear@0: where a mod b means the remainder after dividing a by b. nuclear@0: nuclear@0: This calculation is done using the shift-register method of multiplying and nuclear@0: taking the remainder. The register is initialized to zero, and for each nuclear@0: incoming bit, x^32 is added mod p to the register if the bit is a one (where nuclear@0: x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by nuclear@0: x (which is shifting right by one and adding x^32 mod p if the bit shifted nuclear@0: out is a one). We start with the highest power (least significant bit) of nuclear@0: q and repeat for all eight bits of q. nuclear@0: nuclear@0: The first table is simply the CRC of all possible eight bit values. This is nuclear@0: all the information needed to generate CRCs on data a byte at a time for all nuclear@0: combinations of CRC register values and incoming bytes. The remaining tables nuclear@0: allow for word-at-a-time CRC calculation for both big-endian and little- nuclear@0: endian machines, where a word is four bytes. nuclear@0: */ nuclear@0: local void make_crc_table() nuclear@0: { nuclear@0: unsigned long c; nuclear@0: int n, k; nuclear@0: unsigned long poly; /* polynomial exclusive-or pattern */ nuclear@0: /* terms of polynomial defining this crc (except x^32): */ nuclear@0: static volatile int first = 1; /* flag to limit concurrent making */ nuclear@0: static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26}; nuclear@0: nuclear@0: /* See if another task is already doing this (not thread-safe, but better nuclear@0: than nothing -- significantly reduces duration of vulnerability in nuclear@0: case the advice about DYNAMIC_CRC_TABLE is ignored) */ nuclear@0: if (first) { nuclear@0: first = 0; nuclear@0: nuclear@0: /* make exclusive-or pattern from polynomial (0xedb88320UL) */ nuclear@0: poly = 0UL; nuclear@0: for (n = 0; n < sizeof(p)/sizeof(unsigned char); n++) nuclear@0: poly |= 1UL << (31 - p[n]); nuclear@0: nuclear@0: /* generate a crc for every 8-bit value */ nuclear@0: for (n = 0; n < 256; n++) { nuclear@0: c = (unsigned long)n; nuclear@0: for (k = 0; k < 8; k++) nuclear@0: c = c & 1 ? poly ^ (c >> 1) : c >> 1; nuclear@0: crc_table[0][n] = c; nuclear@0: } nuclear@0: nuclear@0: #ifdef BYFOUR nuclear@0: /* generate crc for each value followed by one, two, and three zeros, nuclear@0: and then the byte reversal of those as well as the first table */ nuclear@0: for (n = 0; n < 256; n++) { nuclear@0: c = crc_table[0][n]; nuclear@0: crc_table[4][n] = REV(c); nuclear@0: for (k = 1; k < 4; k++) { nuclear@0: c = crc_table[0][c & 0xff] ^ (c >> 8); nuclear@0: crc_table[k][n] = c; nuclear@0: crc_table[k + 4][n] = REV(c); nuclear@0: } nuclear@0: } nuclear@0: #endif /* BYFOUR */ nuclear@0: nuclear@0: crc_table_empty = 0; nuclear@0: } nuclear@0: else { /* not first */ nuclear@0: /* wait for the other guy to finish (not efficient, but rare) */ nuclear@0: while (crc_table_empty) nuclear@0: ; nuclear@0: } nuclear@0: nuclear@0: #ifdef MAKECRCH nuclear@0: /* write out CRC tables to crc32.h */ nuclear@0: { nuclear@0: FILE *out; nuclear@0: nuclear@0: out = fopen("crc32.h", "w"); nuclear@0: if (out == NULL) return; nuclear@0: fprintf(out, "/* crc32.h -- tables for rapid CRC calculation\n"); nuclear@0: fprintf(out, " * Generated automatically by crc32.c\n */\n\n"); nuclear@0: fprintf(out, "local const unsigned long FAR "); nuclear@0: fprintf(out, "crc_table[TBLS][256] =\n{\n {\n"); nuclear@0: write_table(out, crc_table[0]); nuclear@0: # ifdef BYFOUR nuclear@0: fprintf(out, "#ifdef BYFOUR\n"); nuclear@0: for (k = 1; k < 8; k++) { nuclear@0: fprintf(out, " },\n {\n"); nuclear@0: write_table(out, crc_table[k]); nuclear@0: } nuclear@0: fprintf(out, "#endif\n"); nuclear@0: # endif /* BYFOUR */ nuclear@0: fprintf(out, " }\n};\n"); nuclear@0: fclose(out); nuclear@0: } nuclear@0: #endif /* MAKECRCH */ nuclear@0: } nuclear@0: nuclear@0: #ifdef MAKECRCH nuclear@0: local void write_table(out, table) nuclear@0: FILE *out; nuclear@0: const unsigned long FAR *table; nuclear@0: { nuclear@0: int n; nuclear@0: nuclear@0: for (n = 0; n < 256; n++) nuclear@0: fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : " ", table[n], nuclear@0: n == 255 ? "\n" : (n % 5 == 4 ? ",\n" : ", ")); nuclear@0: } nuclear@0: #endif /* MAKECRCH */ nuclear@0: nuclear@0: #else /* !DYNAMIC_CRC_TABLE */ nuclear@0: /* ======================================================================== nuclear@0: * Tables of CRC-32s of all single-byte values, made by make_crc_table(). nuclear@0: */ nuclear@0: #include "crc32.h" nuclear@0: #endif /* DYNAMIC_CRC_TABLE */ nuclear@0: nuclear@0: /* ========================================================================= nuclear@0: * This function can be used by asm versions of crc32() nuclear@0: */ nuclear@0: const unsigned long FAR * ZEXPORT get_crc_table() nuclear@0: { nuclear@0: #ifdef DYNAMIC_CRC_TABLE nuclear@0: if (crc_table_empty) nuclear@0: make_crc_table(); nuclear@0: #endif /* DYNAMIC_CRC_TABLE */ nuclear@0: return (const unsigned long FAR *)crc_table; nuclear@0: } nuclear@0: nuclear@0: /* ========================================================================= */ nuclear@0: #define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8) nuclear@0: #define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1 nuclear@0: nuclear@0: /* ========================================================================= */ nuclear@0: unsigned long ZEXPORT crc32(crc, buf, len) nuclear@0: unsigned long crc; nuclear@0: const unsigned char FAR *buf; nuclear@0: unsigned len; nuclear@0: { nuclear@0: if (buf == Z_NULL) return 0UL; nuclear@0: nuclear@0: #ifdef DYNAMIC_CRC_TABLE nuclear@0: if (crc_table_empty) nuclear@0: make_crc_table(); nuclear@0: #endif /* DYNAMIC_CRC_TABLE */ nuclear@0: nuclear@0: #ifdef BYFOUR nuclear@0: if (sizeof(void *) == sizeof(ptrdiff_t)) { nuclear@0: u4 endian; nuclear@0: nuclear@0: endian = 1; nuclear@0: if (*((unsigned char *)(&endian))) nuclear@0: return crc32_little(crc, buf, len); nuclear@0: else nuclear@0: return crc32_big(crc, buf, len); nuclear@0: } nuclear@0: #endif /* BYFOUR */ nuclear@0: crc = crc ^ 0xffffffffUL; nuclear@0: while (len >= 8) { nuclear@0: DO8; nuclear@0: len -= 8; nuclear@0: } nuclear@0: if (len) do { nuclear@0: DO1; nuclear@0: } while (--len); nuclear@0: return crc ^ 0xffffffffUL; nuclear@0: } nuclear@0: nuclear@0: #ifdef BYFOUR nuclear@0: nuclear@0: /* ========================================================================= */ nuclear@0: #define DOLIT4 c ^= *buf4++; \ nuclear@0: c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \ nuclear@0: crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24] nuclear@0: #define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4 nuclear@0: nuclear@0: /* ========================================================================= */ nuclear@0: local unsigned long crc32_little(crc, buf, len) nuclear@0: unsigned long crc; nuclear@0: const unsigned char FAR *buf; nuclear@0: unsigned len; nuclear@0: { nuclear@0: register u4 c; nuclear@0: register const u4 FAR *buf4; nuclear@0: nuclear@0: c = (u4)crc; nuclear@0: c = ~c; nuclear@0: while (len && ((ptrdiff_t)buf & 3)) { nuclear@0: c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8); nuclear@0: len--; nuclear@0: } nuclear@0: nuclear@0: buf4 = (const u4 FAR *)(const void FAR *)buf; nuclear@0: while (len >= 32) { nuclear@0: DOLIT32; nuclear@0: len -= 32; nuclear@0: } nuclear@0: while (len >= 4) { nuclear@0: DOLIT4; nuclear@0: len -= 4; nuclear@0: } nuclear@0: buf = (const unsigned char FAR *)buf4; nuclear@0: nuclear@0: if (len) do { nuclear@0: c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8); nuclear@0: } while (--len); nuclear@0: c = ~c; nuclear@0: return (unsigned long)c; nuclear@0: } nuclear@0: nuclear@0: /* ========================================================================= */ nuclear@0: #define DOBIG4 c ^= *++buf4; \ nuclear@0: c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \ nuclear@0: crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24] nuclear@0: #define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4 nuclear@0: nuclear@0: /* ========================================================================= */ nuclear@0: local unsigned long crc32_big(crc, buf, len) nuclear@0: unsigned long crc; nuclear@0: const unsigned char FAR *buf; nuclear@0: unsigned len; nuclear@0: { nuclear@0: register u4 c; nuclear@0: register const u4 FAR *buf4; nuclear@0: nuclear@0: c = REV((u4)crc); nuclear@0: c = ~c; nuclear@0: while (len && ((ptrdiff_t)buf & 3)) { nuclear@0: c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8); nuclear@0: len--; nuclear@0: } nuclear@0: nuclear@0: buf4 = (const u4 FAR *)(const void FAR *)buf; nuclear@0: buf4--; nuclear@0: while (len >= 32) { nuclear@0: DOBIG32; nuclear@0: len -= 32; nuclear@0: } nuclear@0: while (len >= 4) { nuclear@0: DOBIG4; nuclear@0: len -= 4; nuclear@0: } nuclear@0: buf4++; nuclear@0: buf = (const unsigned char FAR *)buf4; nuclear@0: nuclear@0: if (len) do { nuclear@0: c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8); nuclear@0: } while (--len); nuclear@0: c = ~c; nuclear@0: return (unsigned long)(REV(c)); nuclear@0: } nuclear@0: nuclear@0: #endif /* BYFOUR */ nuclear@0: nuclear@0: #define GF2_DIM 32 /* dimension of GF(2) vectors (length of CRC) */ nuclear@0: nuclear@0: /* ========================================================================= */ nuclear@0: local unsigned long gf2_matrix_times(mat, vec) nuclear@0: unsigned long *mat; nuclear@0: unsigned long vec; nuclear@0: { nuclear@0: unsigned long sum; nuclear@0: nuclear@0: sum = 0; nuclear@0: while (vec) { nuclear@0: if (vec & 1) nuclear@0: sum ^= *mat; nuclear@0: vec >>= 1; nuclear@0: mat++; nuclear@0: } nuclear@0: return sum; nuclear@0: } nuclear@0: nuclear@0: /* ========================================================================= */ nuclear@0: local void gf2_matrix_square(square, mat) nuclear@0: unsigned long *square; nuclear@0: unsigned long *mat; nuclear@0: { nuclear@0: int n; nuclear@0: nuclear@0: for (n = 0; n < GF2_DIM; n++) nuclear@0: square[n] = gf2_matrix_times(mat, mat[n]); nuclear@0: } nuclear@0: nuclear@0: /* ========================================================================= */ nuclear@0: uLong ZEXPORT crc32_combine(crc1, crc2, len2) nuclear@0: uLong crc1; nuclear@0: uLong crc2; nuclear@0: z_off_t len2; nuclear@0: { nuclear@0: int n; nuclear@0: unsigned long row; nuclear@0: unsigned long even[GF2_DIM]; /* even-power-of-two zeros operator */ nuclear@0: unsigned long odd[GF2_DIM]; /* odd-power-of-two zeros operator */ nuclear@0: nuclear@0: /* degenerate case */ nuclear@0: if (len2 == 0) nuclear@0: return crc1; nuclear@0: nuclear@0: /* put operator for one zero bit in odd */ nuclear@0: odd[0] = 0xedb88320L; /* CRC-32 polynomial */ nuclear@0: row = 1; nuclear@0: for (n = 1; n < GF2_DIM; n++) { nuclear@0: odd[n] = row; nuclear@0: row <<= 1; nuclear@0: } nuclear@0: nuclear@0: /* put operator for two zero bits in even */ nuclear@0: gf2_matrix_square(even, odd); nuclear@0: nuclear@0: /* put operator for four zero bits in odd */ nuclear@0: gf2_matrix_square(odd, even); nuclear@0: nuclear@0: /* apply len2 zeros to crc1 (first square will put the operator for one nuclear@0: zero byte, eight zero bits, in even) */ nuclear@0: do { nuclear@0: /* apply zeros operator for this bit of len2 */ nuclear@0: gf2_matrix_square(even, odd); nuclear@0: if (len2 & 1) nuclear@0: crc1 = gf2_matrix_times(even, crc1); nuclear@0: len2 >>= 1; nuclear@0: nuclear@0: /* if no more bits set, then done */ nuclear@0: if (len2 == 0) nuclear@0: break; nuclear@0: nuclear@0: /* another iteration of the loop with odd and even swapped */ nuclear@0: gf2_matrix_square(odd, even); nuclear@0: if (len2 & 1) nuclear@0: crc1 = gf2_matrix_times(odd, crc1); nuclear@0: len2 >>= 1; nuclear@0: nuclear@0: /* if no more bits set, then done */ nuclear@0: } while (len2 != 0); nuclear@0: nuclear@0: /* return combined crc */ nuclear@0: crc1 ^= crc2; nuclear@0: return crc1; nuclear@0: }