cannam@89: /* crc32.c -- compute the CRC-32 of a data stream
cannam@89:  * Copyright (C) 1995-2006, 2010, 2011, 2012 Mark Adler
cannam@89:  * For conditions of distribution and use, see copyright notice in zlib.h
cannam@89:  *
cannam@89:  * Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster
cannam@89:  * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
cannam@89:  * tables for updating the shift register in one step with three exclusive-ors
cannam@89:  * instead of four steps with four exclusive-ors.  This results in about a
cannam@89:  * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
cannam@89:  */
cannam@89: 
cannam@89: /* @(#) $Id$ */
cannam@89: 
cannam@89: /*
cannam@89:   Note on the use of DYNAMIC_CRC_TABLE: there is no mutex or semaphore
cannam@89:   protection on the static variables used to control the first-use generation
cannam@89:   of the crc tables.  Therefore, if you #define DYNAMIC_CRC_TABLE, you should
cannam@89:   first call get_crc_table() to initialize the tables before allowing more than
cannam@89:   one thread to use crc32().
cannam@89: 
cannam@89:   DYNAMIC_CRC_TABLE and MAKECRCH can be #defined to write out crc32.h.
cannam@89:  */
cannam@89: 
cannam@89: #ifdef MAKECRCH
cannam@89: #  include <stdio.h>
cannam@89: #  ifndef DYNAMIC_CRC_TABLE
cannam@89: #    define DYNAMIC_CRC_TABLE
cannam@89: #  endif /* !DYNAMIC_CRC_TABLE */
cannam@89: #endif /* MAKECRCH */
cannam@89: 
cannam@89: #include "zutil.h"      /* for STDC and FAR definitions */
cannam@89: 
cannam@89: #define local static
cannam@89: 
cannam@89: /* Definitions for doing the crc four data bytes at a time. */
cannam@89: #if !defined(NOBYFOUR) && defined(Z_U4)
cannam@89: #  define BYFOUR
cannam@89: #endif
cannam@89: #ifdef BYFOUR
cannam@89:    local unsigned long crc32_little OF((unsigned long,
cannam@89:                         const unsigned char FAR *, unsigned));
cannam@89:    local unsigned long crc32_big OF((unsigned long,
cannam@89:                         const unsigned char FAR *, unsigned));
cannam@89: #  define TBLS 8
cannam@89: #else
cannam@89: #  define TBLS 1
cannam@89: #endif /* BYFOUR */
cannam@89: 
cannam@89: /* Local functions for crc concatenation */
cannam@89: local unsigned long gf2_matrix_times OF((unsigned long *mat,
cannam@89:                                          unsigned long vec));
cannam@89: local void gf2_matrix_square OF((unsigned long *square, unsigned long *mat));
cannam@89: local uLong crc32_combine_ OF((uLong crc1, uLong crc2, z_off64_t len2));
cannam@89: 
cannam@89: 
cannam@89: #ifdef DYNAMIC_CRC_TABLE
cannam@89: 
cannam@89: local volatile int crc_table_empty = 1;
cannam@89: local z_crc_t FAR crc_table[TBLS][256];
cannam@89: local void make_crc_table OF((void));
cannam@89: #ifdef MAKECRCH
cannam@89:    local void write_table OF((FILE *, const z_crc_t FAR *));
cannam@89: #endif /* MAKECRCH */
cannam@89: /*
cannam@89:   Generate tables for a byte-wise 32-bit CRC calculation on the polynomial:
cannam@89:   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.
cannam@89: 
cannam@89:   Polynomials over GF(2) are represented in binary, one bit per coefficient,
cannam@89:   with the lowest powers in the most significant bit.  Then adding polynomials
cannam@89:   is just exclusive-or, and multiplying a polynomial by x is a right shift by
cannam@89:   one.  If we call the above polynomial p, and represent a byte as the
cannam@89:   polynomial q, also with the lowest power in the most significant bit (so the
cannam@89:   byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
cannam@89:   where a mod b means the remainder after dividing a by b.
cannam@89: 
cannam@89:   This calculation is done using the shift-register method of multiplying and
cannam@89:   taking the remainder.  The register is initialized to zero, and for each
cannam@89:   incoming bit, x^32 is added mod p to the register if the bit is a one (where
cannam@89:   x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
cannam@89:   x (which is shifting right by one and adding x^32 mod p if the bit shifted
cannam@89:   out is a one).  We start with the highest power (least significant bit) of
cannam@89:   q and repeat for all eight bits of q.
cannam@89: 
cannam@89:   The first table is simply the CRC of all possible eight bit values.  This is
cannam@89:   all the information needed to generate CRCs on data a byte at a time for all
cannam@89:   combinations of CRC register values and incoming bytes.  The remaining tables
cannam@89:   allow for word-at-a-time CRC calculation for both big-endian and little-
cannam@89:   endian machines, where a word is four bytes.
cannam@89: */
cannam@89: local void make_crc_table()
cannam@89: {
cannam@89:     z_crc_t c;
cannam@89:     int n, k;
cannam@89:     z_crc_t poly;                       /* polynomial exclusive-or pattern */
cannam@89:     /* terms of polynomial defining this crc (except x^32): */
cannam@89:     static volatile int first = 1;      /* flag to limit concurrent making */
cannam@89:     static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
cannam@89: 
cannam@89:     /* See if another task is already doing this (not thread-safe, but better
cannam@89:        than nothing -- significantly reduces duration of vulnerability in
cannam@89:        case the advice about DYNAMIC_CRC_TABLE is ignored) */
cannam@89:     if (first) {
cannam@89:         first = 0;
cannam@89: 
cannam@89:         /* make exclusive-or pattern from polynomial (0xedb88320UL) */
cannam@89:         poly = 0;
cannam@89:         for (n = 0; n < (int)(sizeof(p)/sizeof(unsigned char)); n++)
cannam@89:             poly |= (z_crc_t)1 << (31 - p[n]);
cannam@89: 
cannam@89:         /* generate a crc for every 8-bit value */
cannam@89:         for (n = 0; n < 256; n++) {
cannam@89:             c = (z_crc_t)n;
cannam@89:             for (k = 0; k < 8; k++)
cannam@89:                 c = c & 1 ? poly ^ (c >> 1) : c >> 1;
cannam@89:             crc_table[0][n] = c;
cannam@89:         }
cannam@89: 
cannam@89: #ifdef BYFOUR
cannam@89:         /* generate crc for each value followed by one, two, and three zeros,
cannam@89:            and then the byte reversal of those as well as the first table */
cannam@89:         for (n = 0; n < 256; n++) {
cannam@89:             c = crc_table[0][n];
cannam@89:             crc_table[4][n] = ZSWAP32(c);
cannam@89:             for (k = 1; k < 4; k++) {
cannam@89:                 c = crc_table[0][c & 0xff] ^ (c >> 8);
cannam@89:                 crc_table[k][n] = c;
cannam@89:                 crc_table[k + 4][n] = ZSWAP32(c);
cannam@89:             }
cannam@89:         }
cannam@89: #endif /* BYFOUR */
cannam@89: 
cannam@89:         crc_table_empty = 0;
cannam@89:     }
cannam@89:     else {      /* not first */
cannam@89:         /* wait for the other guy to finish (not efficient, but rare) */
cannam@89:         while (crc_table_empty)
cannam@89:             ;
cannam@89:     }
cannam@89: 
cannam@89: #ifdef MAKECRCH
cannam@89:     /* write out CRC tables to crc32.h */
cannam@89:     {
cannam@89:         FILE *out;
cannam@89: 
cannam@89:         out = fopen("crc32.h", "w");
cannam@89:         if (out == NULL) return;
cannam@89:         fprintf(out, "/* crc32.h -- tables for rapid CRC calculation\n");
cannam@89:         fprintf(out, " * Generated automatically by crc32.c\n */\n\n");
cannam@89:         fprintf(out, "local const z_crc_t FAR ");
cannam@89:         fprintf(out, "crc_table[TBLS][256] =\n{\n  {\n");
cannam@89:         write_table(out, crc_table[0]);
cannam@89: #  ifdef BYFOUR
cannam@89:         fprintf(out, "#ifdef BYFOUR\n");
cannam@89:         for (k = 1; k < 8; k++) {
cannam@89:             fprintf(out, "  },\n  {\n");
cannam@89:             write_table(out, crc_table[k]);
cannam@89:         }
cannam@89:         fprintf(out, "#endif\n");
cannam@89: #  endif /* BYFOUR */
cannam@89:         fprintf(out, "  }\n};\n");
cannam@89:         fclose(out);
cannam@89:     }
cannam@89: #endif /* MAKECRCH */
cannam@89: }
cannam@89: 
cannam@89: #ifdef MAKECRCH
cannam@89: local void write_table(out, table)
cannam@89:     FILE *out;
cannam@89:     const z_crc_t FAR *table;
cannam@89: {
cannam@89:     int n;
cannam@89: 
cannam@89:     for (n = 0; n < 256; n++)
cannam@89:         fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : "    ",
cannam@89:                 (unsigned long)(table[n]),
cannam@89:                 n == 255 ? "\n" : (n % 5 == 4 ? ",\n" : ", "));
cannam@89: }
cannam@89: #endif /* MAKECRCH */
cannam@89: 
cannam@89: #else /* !DYNAMIC_CRC_TABLE */
cannam@89: /* ========================================================================
cannam@89:  * Tables of CRC-32s of all single-byte values, made by make_crc_table().
cannam@89:  */
cannam@89: #include "crc32.h"
cannam@89: #endif /* DYNAMIC_CRC_TABLE */
cannam@89: 
cannam@89: /* =========================================================================
cannam@89:  * This function can be used by asm versions of crc32()
cannam@89:  */
cannam@89: const z_crc_t FAR * ZEXPORT get_crc_table()
cannam@89: {
cannam@89: #ifdef DYNAMIC_CRC_TABLE
cannam@89:     if (crc_table_empty)
cannam@89:         make_crc_table();
cannam@89: #endif /* DYNAMIC_CRC_TABLE */
cannam@89:     return (const z_crc_t FAR *)crc_table;
cannam@89: }
cannam@89: 
cannam@89: /* ========================================================================= */
cannam@89: #define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8)
cannam@89: #define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1
cannam@89: 
cannam@89: /* ========================================================================= */
cannam@89: unsigned long ZEXPORT crc32(crc, buf, len)
cannam@89:     unsigned long crc;
cannam@89:     const unsigned char FAR *buf;
cannam@89:     uInt len;
cannam@89: {
cannam@89:     if (buf == Z_NULL) return 0UL;
cannam@89: 
cannam@89: #ifdef DYNAMIC_CRC_TABLE
cannam@89:     if (crc_table_empty)
cannam@89:         make_crc_table();
cannam@89: #endif /* DYNAMIC_CRC_TABLE */
cannam@89: 
cannam@89: #ifdef BYFOUR
cannam@89:     if (sizeof(void *) == sizeof(ptrdiff_t)) {
cannam@89:         z_crc_t endian;
cannam@89: 
cannam@89:         endian = 1;
cannam@89:         if (*((unsigned char *)(&endian)))
cannam@89:             return crc32_little(crc, buf, len);
cannam@89:         else
cannam@89:             return crc32_big(crc, buf, len);
cannam@89:     }
cannam@89: #endif /* BYFOUR */
cannam@89:     crc = crc ^ 0xffffffffUL;
cannam@89:     while (len >= 8) {
cannam@89:         DO8;
cannam@89:         len -= 8;
cannam@89:     }
cannam@89:     if (len) do {
cannam@89:         DO1;
cannam@89:     } while (--len);
cannam@89:     return crc ^ 0xffffffffUL;
cannam@89: }
cannam@89: 
cannam@89: #ifdef BYFOUR
cannam@89: 
cannam@89: /* ========================================================================= */
cannam@89: #define DOLIT4 c ^= *buf4++; \
cannam@89:         c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \
cannam@89:             crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24]
cannam@89: #define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4
cannam@89: 
cannam@89: /* ========================================================================= */
cannam@89: local unsigned long crc32_little(crc, buf, len)
cannam@89:     unsigned long crc;
cannam@89:     const unsigned char FAR *buf;
cannam@89:     unsigned len;
cannam@89: {
cannam@89:     register z_crc_t c;
cannam@89:     register const z_crc_t FAR *buf4;
cannam@89: 
cannam@89:     c = (z_crc_t)crc;
cannam@89:     c = ~c;
cannam@89:     while (len && ((ptrdiff_t)buf & 3)) {
cannam@89:         c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
cannam@89:         len--;
cannam@89:     }
cannam@89: 
cannam@89:     buf4 = (const z_crc_t FAR *)(const void FAR *)buf;
cannam@89:     while (len >= 32) {
cannam@89:         DOLIT32;
cannam@89:         len -= 32;
cannam@89:     }
cannam@89:     while (len >= 4) {
cannam@89:         DOLIT4;
cannam@89:         len -= 4;
cannam@89:     }
cannam@89:     buf = (const unsigned char FAR *)buf4;
cannam@89: 
cannam@89:     if (len) do {
cannam@89:         c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
cannam@89:     } while (--len);
cannam@89:     c = ~c;
cannam@89:     return (unsigned long)c;
cannam@89: }
cannam@89: 
cannam@89: /* ========================================================================= */
cannam@89: #define DOBIG4 c ^= *++buf4; \
cannam@89:         c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \
cannam@89:             crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24]
cannam@89: #define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4
cannam@89: 
cannam@89: /* ========================================================================= */
cannam@89: local unsigned long crc32_big(crc, buf, len)
cannam@89:     unsigned long crc;
cannam@89:     const unsigned char FAR *buf;
cannam@89:     unsigned len;
cannam@89: {
cannam@89:     register z_crc_t c;
cannam@89:     register const z_crc_t FAR *buf4;
cannam@89: 
cannam@89:     c = ZSWAP32((z_crc_t)crc);
cannam@89:     c = ~c;
cannam@89:     while (len && ((ptrdiff_t)buf & 3)) {
cannam@89:         c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
cannam@89:         len--;
cannam@89:     }
cannam@89: 
cannam@89:     buf4 = (const z_crc_t FAR *)(const void FAR *)buf;
cannam@89:     buf4--;
cannam@89:     while (len >= 32) {
cannam@89:         DOBIG32;
cannam@89:         len -= 32;
cannam@89:     }
cannam@89:     while (len >= 4) {
cannam@89:         DOBIG4;
cannam@89:         len -= 4;
cannam@89:     }
cannam@89:     buf4++;
cannam@89:     buf = (const unsigned char FAR *)buf4;
cannam@89: 
cannam@89:     if (len) do {
cannam@89:         c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
cannam@89:     } while (--len);
cannam@89:     c = ~c;
cannam@89:     return (unsigned long)(ZSWAP32(c));
cannam@89: }
cannam@89: 
cannam@89: #endif /* BYFOUR */
cannam@89: 
cannam@89: #define GF2_DIM 32      /* dimension of GF(2) vectors (length of CRC) */
cannam@89: 
cannam@89: /* ========================================================================= */
cannam@89: local unsigned long gf2_matrix_times(mat, vec)
cannam@89:     unsigned long *mat;
cannam@89:     unsigned long vec;
cannam@89: {
cannam@89:     unsigned long sum;
cannam@89: 
cannam@89:     sum = 0;
cannam@89:     while (vec) {
cannam@89:         if (vec & 1)
cannam@89:             sum ^= *mat;
cannam@89:         vec >>= 1;
cannam@89:         mat++;
cannam@89:     }
cannam@89:     return sum;
cannam@89: }
cannam@89: 
cannam@89: /* ========================================================================= */
cannam@89: local void gf2_matrix_square(square, mat)
cannam@89:     unsigned long *square;
cannam@89:     unsigned long *mat;
cannam@89: {
cannam@89:     int n;
cannam@89: 
cannam@89:     for (n = 0; n < GF2_DIM; n++)
cannam@89:         square[n] = gf2_matrix_times(mat, mat[n]);
cannam@89: }
cannam@89: 
cannam@89: /* ========================================================================= */
cannam@89: local uLong crc32_combine_(crc1, crc2, len2)
cannam@89:     uLong crc1;
cannam@89:     uLong crc2;
cannam@89:     z_off64_t len2;
cannam@89: {
cannam@89:     int n;
cannam@89:     unsigned long row;
cannam@89:     unsigned long even[GF2_DIM];    /* even-power-of-two zeros operator */
cannam@89:     unsigned long odd[GF2_DIM];     /* odd-power-of-two zeros operator */
cannam@89: 
cannam@89:     /* degenerate case (also disallow negative lengths) */
cannam@89:     if (len2 <= 0)
cannam@89:         return crc1;
cannam@89: 
cannam@89:     /* put operator for one zero bit in odd */
cannam@89:     odd[0] = 0xedb88320UL;          /* CRC-32 polynomial */
cannam@89:     row = 1;
cannam@89:     for (n = 1; n < GF2_DIM; n++) {
cannam@89:         odd[n] = row;
cannam@89:         row <<= 1;
cannam@89:     }
cannam@89: 
cannam@89:     /* put operator for two zero bits in even */
cannam@89:     gf2_matrix_square(even, odd);
cannam@89: 
cannam@89:     /* put operator for four zero bits in odd */
cannam@89:     gf2_matrix_square(odd, even);
cannam@89: 
cannam@89:     /* apply len2 zeros to crc1 (first square will put the operator for one
cannam@89:        zero byte, eight zero bits, in even) */
cannam@89:     do {
cannam@89:         /* apply zeros operator for this bit of len2 */
cannam@89:         gf2_matrix_square(even, odd);
cannam@89:         if (len2 & 1)
cannam@89:             crc1 = gf2_matrix_times(even, crc1);
cannam@89:         len2 >>= 1;
cannam@89: 
cannam@89:         /* if no more bits set, then done */
cannam@89:         if (len2 == 0)
cannam@89:             break;
cannam@89: 
cannam@89:         /* another iteration of the loop with odd and even swapped */
cannam@89:         gf2_matrix_square(odd, even);
cannam@89:         if (len2 & 1)
cannam@89:             crc1 = gf2_matrix_times(odd, crc1);
cannam@89:         len2 >>= 1;
cannam@89: 
cannam@89:         /* if no more bits set, then done */
cannam@89:     } while (len2 != 0);
cannam@89: 
cannam@89:     /* return combined crc */
cannam@89:     crc1 ^= crc2;
cannam@89:     return crc1;
cannam@89: }
cannam@89: 
cannam@89: /* ========================================================================= */
cannam@89: uLong ZEXPORT crc32_combine(crc1, crc2, len2)
cannam@89:     uLong crc1;
cannam@89:     uLong crc2;
cannam@89:     z_off_t len2;
cannam@89: {
cannam@89:     return crc32_combine_(crc1, crc2, len2);
cannam@89: }
cannam@89: 
cannam@89: uLong ZEXPORT crc32_combine64(crc1, crc2, len2)
cannam@89:     uLong crc1;
cannam@89:     uLong crc2;
cannam@89:     z_off64_t len2;
cannam@89: {
cannam@89:     return crc32_combine_(crc1, crc2, len2);
cannam@89: }