1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* crc32.c -- compute the CRC-32 of a data stream
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync * Copyright (C) 1995-2006, 2010, 2011 Mark Adler
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync * For conditions of distribution and use, see copyright notice in zlib.h
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync * Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync * tables for updating the shift register in one step with three exclusive-ors
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync * instead of four steps with four exclusive-ors. This results in about a
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* @(#) $Id$ */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync Note on the use of DYNAMIC_CRC_TABLE: there is no mutex or semaphore
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync protection on the static variables used to control the first-use generation
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync of the crc tables. Therefore, if you #define DYNAMIC_CRC_TABLE, you should
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync first call get_crc_table() to initialize the tables before allowing more than
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync one thread to use crc32().
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync DYNAMIC_CRC_TABLE and MAKECRCH can be #defined to write out crc32.h.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync# endif /* !DYNAMIC_CRC_TABLE */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#endif /* MAKECRCH */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#include "zutil.h" /* for STDC and FAR definitions */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* Find a four-byte integer type for crc32_little() and crc32_big(). */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync# ifdef STDC /* need ANSI C limits.h to determine sizes */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync# undef BYFOUR /* can't find a four-byte integer type! */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync# endif /* STDC */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#endif /* !NOBYFOUR */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* Definitions for doing the crc four data bytes at a time. */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync# define REV(w) ((((w)>>24)&0xff)+(((w)>>8)&0xff00)+ \
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync local unsigned long crc32_little OF((unsigned long,
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync const unsigned char FAR *, unsigned));
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync const unsigned char FAR *, unsigned));
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#endif /* BYFOUR */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* Local functions for crc concatenation */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsynclocal unsigned long gf2_matrix_times OF((unsigned long *mat,
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync unsigned long vec));
1b33c96954667ba382fa595baf7b31290bfdd517vboxsynclocal void gf2_matrix_square OF((unsigned long *square, unsigned long *mat));
1b33c96954667ba382fa595baf7b31290bfdd517vboxsynclocal uLong crc32_combine_ OF((uLong crc1, uLong crc2, z_off64_t len2));
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync local void write_table OF((FILE *, const crc_table_t FAR *));
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#endif /* MAKECRCH */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync Generate tables for a byte-wise 32-bit CRC calculation on the polynomial:
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync 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.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync Polynomials over GF(2) are represented in binary, one bit per coefficient,
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync with the lowest powers in the most significant bit. Then adding polynomials
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync is just exclusive-or, and multiplying a polynomial by x is a right shift by
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync one. If we call the above polynomial p, and represent a byte as the
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync polynomial q, also with the lowest power in the most significant bit (so the
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync where a mod b means the remainder after dividing a by b.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync This calculation is done using the shift-register method of multiplying and
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync taking the remainder. The register is initialized to zero, and for each
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync incoming bit, x^32 is added mod p to the register if the bit is a one (where
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync x (which is shifting right by one and adding x^32 mod p if the bit shifted
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync out is a one). We start with the highest power (least significant bit) of
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync q and repeat for all eight bits of q.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync The first table is simply the CRC of all possible eight bit values. This is
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync all the information needed to generate CRCs on data a byte at a time for all
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync combinations of CRC register values and incoming bytes. The remaining tables
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync allow for word-at-a-time CRC calculation for both big-endian and little-
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync endian machines, where a word is four bytes.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync crc_table_t poly; /* polynomial exclusive-or pattern */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* terms of polynomial defining this crc (except x^32): */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync static volatile int first = 1; /* flag to limit concurrent making */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* See if another task is already doing this (not thread-safe, but better
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync than nothing -- significantly reduces duration of vulnerability in
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync case the advice about DYNAMIC_CRC_TABLE is ignored) */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* make exclusive-or pattern from polynomial (0xedb88320UL) */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync for (n = 0; n < (int)(sizeof(p)/sizeof(unsigned char)); n++)
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* generate a crc for every 8-bit value */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync for (n = 0; n < 256; n++) {
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync for (k = 0; k < 8; k++)
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* generate crc for each value followed by one, two, and three zeros,
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync and then the byte reversal of those as well as the first table */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync for (n = 0; n < 256; n++) {
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#endif /* BYFOUR */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync else { /* not first */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* wait for the other guy to finish (not efficient, but rare) */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* write out CRC tables to crc32.h */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync fprintf(out, "/* crc32.h -- tables for rapid CRC calculation\n");
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync fprintf(out, " * Generated automatically by crc32.c\n */\n\n");
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync# endif /* BYFOUR */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#endif /* MAKECRCH */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync for (n = 0; n < 256; n++)
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync (unsigned long)(table[n]),
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#endif /* MAKECRCH */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#else /* !DYNAMIC_CRC_TABLE */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* ========================================================================
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync * Tables of CRC-32s of all single-byte values, made by make_crc_table().
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#endif /* DYNAMIC_CRC_TABLE */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* =========================================================================
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync * This function can be used by asm versions of crc32()
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#endif /* DYNAMIC_CRC_TABLE */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* ========================================================================= */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8)
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* ========================================================================= */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync unsigned long crc;
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#endif /* DYNAMIC_CRC_TABLE */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync if (sizeof(void *) == sizeof(ptrdiff_t)) {
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync if (*((unsigned char *)(&endian)))
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#endif /* BYFOUR */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync } while (--len);
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* ========================================================================= */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24]
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* ========================================================================= */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync unsigned long crc;
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync register u4 c;
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync } while (--len);
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync return (unsigned long)c;
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* ========================================================================= */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24]
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* ========================================================================= */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync unsigned long crc;
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync register u4 c;
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync } while (--len);
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync return (unsigned long)(REV(c));
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#endif /* BYFOUR */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync#define GF2_DIM 32 /* dimension of GF(2) vectors (length of CRC) */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* ========================================================================= */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync unsigned long *mat;
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync unsigned long vec;
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* ========================================================================= */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync unsigned long *square;
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync unsigned long *mat;
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync for (n = 0; n < GF2_DIM; n++)
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* ========================================================================= */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync unsigned long even[GF2_DIM]; /* even-power-of-two zeros operator */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync unsigned long odd[GF2_DIM]; /* odd-power-of-two zeros operator */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* degenerate case (also disallow negative lengths) */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* put operator for one zero bit in odd */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* put operator for two zero bits in even */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* put operator for four zero bits in odd */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* apply len2 zeros to crc1 (first square will put the operator for one
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync zero byte, eight zero bits, in even) */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* apply zeros operator for this bit of len2 */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* if no more bits set, then done */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* another iteration of the loop with odd and even swapped */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* if no more bits set, then done */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync } while (len2 != 0);
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync /* return combined crc */
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync/* ========================================================================= */