+++ /dev/null
-/* crc32.c -- compute the CRC-32 of a data stream
- * Copyright (C) 1995-2005 Mark Adler
- * For conditions of distribution and use, see copyright notice in zlib.h
- *
- * Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster
- * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
- * tables for updating the shift register in one step with three exclusive-ors
- * instead of four steps with four exclusive-ors. This results in about a
- * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
- */
-
-/* @(#) $Id$ */
-
-#include "zutil.h" /* for STDC and FAR definitions */
-
-/*
- Note on the use of DYNAMIC_CRC_TABLE: there is no mutex or semaphore
- protection on the static variables used to control the first-use generation
- of the crc tables. Therefore, if you #define DYNAMIC_CRC_TABLE, you should
- first call get_crc_table() to initialize the tables before allowing more than
- one thread to use crc32().
- */
-
-#ifdef MAKECRCH
-# include <stdio.h>
-# ifndef DYNAMIC_CRC_TABLE
-# define DYNAMIC_CRC_TABLE
-# endif /* !DYNAMIC_CRC_TABLE */
-#endif /* MAKECRCH */
-
-#define local static
-
-/* Find a four-byte integer type for crc32_little() and crc32_big(). */
-#ifndef NOBYFOUR
-# ifdef STDC /* need ANSI C limits.h to determine sizes */
-# include <limits.h>
-# define BYFOUR
-# if (UINT_MAX == 0xffffffffUL)
- typedef unsigned int u4;
-# else
-# if (ULONG_MAX == 0xffffffffUL)
- typedef unsigned long u4;
-# else
-# if (USHRT_MAX == 0xffffffffUL)
- typedef unsigned short u4;
-# else
-# undef BYFOUR /* can't find a four-byte integer type! */
-# endif
-# endif
-# endif
-# endif /* STDC */
-#endif /* !NOBYFOUR */
-
-/* Definitions for doing the crc four data bytes at a time. */
-#ifdef BYFOUR
-# define REV(w) (((w)>>24)+(((w)>>8)&0xff00)+ \
- (((w)&0xff00)<<8)+(((w)&0xff)<<24))
- local unsigned long crc32_little OF((unsigned long,
- const unsigned char FAR *, unsigned));
- local unsigned long crc32_big OF((unsigned long,
- const unsigned char FAR *, unsigned));
-# define TBLS 8
-#else
-# define TBLS 1
-#endif /* BYFOUR */
-
-/* Local functions for crc concatenation */
-local unsigned long gf2_matrix_times OF((unsigned long *mat,
- unsigned long vec));
-local void gf2_matrix_square OF((unsigned long *square, unsigned long *mat));
-
-#ifdef DYNAMIC_CRC_TABLE
-
-local volatile int crc_table_empty = 1;
-local unsigned long FAR crc_table[TBLS][256];
-local void make_crc_table OF((void));
-#ifdef MAKECRCH
- local void write_table OF((FILE *, const unsigned long FAR *));
-#endif /* MAKECRCH */
-/*
- Generate tables for a byte-wise 32-bit CRC calculation on the polynomial:
- 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.
-
- Polynomials over GF(2) are represented in binary, one bit per coefficient,
- with the lowest powers in the most significant bit. Then adding polynomials
- is just exclusive-or, and multiplying a polynomial by x is a right shift by
- one. If we call the above polynomial p, and represent a byte as the
- polynomial q, also with the lowest power in the most significant bit (so the
- byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
- where a mod b means the remainder after dividing a by b.
-
- This calculation is done using the shift-register method of multiplying and
- taking the remainder. The register is initialized to zero, and for each
- incoming bit, x^32 is added mod p to the register if the bit is a one (where
- x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
- x (which is shifting right by one and adding x^32 mod p if the bit shifted
- out is a one). We start with the highest power (least significant bit) of
- q and repeat for all eight bits of q.
-
- The first table is simply the CRC of all possible eight bit values. This is
- all the information needed to generate CRCs on data a byte at a time for all
- combinations of CRC register values and incoming bytes. The remaining tables
- allow for word-at-a-time CRC calculation for both big-endian and little-
- endian machines, where a word is four bytes.
-*/
-local void make_crc_table()
-{
- unsigned long c;
- int n, k;
- unsigned long poly; /* polynomial exclusive-or pattern */
- /* terms of polynomial defining this crc (except x^32): */
- static volatile int first = 1; /* flag to limit concurrent making */
- static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
-
- /* See if another task is already doing this (not thread-safe, but better
- than nothing -- significantly reduces duration of vulnerability in
- case the advice about DYNAMIC_CRC_TABLE is ignored) */
- if (first) {
- first = 0;
-
- /* make exclusive-or pattern from polynomial (0xedb88320UL) */
- poly = 0UL;
- for (n = 0; n < sizeof(p)/sizeof(unsigned char); n++)
- poly |= 1UL << (31 - p[n]);
-
- /* generate a crc for every 8-bit value */
- for (n = 0; n < 256; n++) {
- c = (unsigned long)n;
- for (k = 0; k < 8; k++)
- c = c & 1 ? poly ^ (c >> 1) : c >> 1;
- crc_table[0][n] = c;
- }
-
-#ifdef BYFOUR
- /* generate crc for each value followed by one, two, and three zeros,
- and then the byte reversal of those as well as the first table */
- for (n = 0; n < 256; n++) {
- c = crc_table[0][n];
- crc_table[4][n] = REV(c);
- for (k = 1; k < 4; k++) {
- c = crc_table[0][c & 0xff] ^ (c >> 8);
- crc_table[k][n] = c;
- crc_table[k + 4][n] = REV(c);
- }
- }
-#endif /* BYFOUR */
-
- crc_table_empty = 0;
- }
- else { /* not first */
- /* wait for the other guy to finish (not efficient, but rare) */
- while (crc_table_empty)
- ;
- }
-
-#ifdef MAKECRCH
- /* write out CRC tables to crc32.h */
- {
- FILE *out;
-
- out = fopen("crc32.h", "w");
- if (out == NULL) return;
- fprintf(out, "/* crc32.h -- tables for rapid CRC calculation\n");
- fprintf(out, " * Generated automatically by crc32.c\n */\n\n");
- fprintf(out, "local const unsigned long FAR ");
- fprintf(out, "crc_table[TBLS][256] =\n{\n {\n");
- write_table(out, crc_table[0]);
-# ifdef BYFOUR
- fprintf(out, "#ifdef BYFOUR\n");
- for (k = 1; k < 8; k++) {
- fprintf(out, " },\n {\n");
- write_table(out, crc_table[k]);
- }
- fprintf(out, "#endif\n");
-# endif /* BYFOUR */
- fprintf(out, " }\n};\n");
- fclose(out);
- }
-#endif /* MAKECRCH */
-}
-
-#ifdef MAKECRCH
-local void write_table(out, table)
- FILE *out;
- const unsigned long FAR *table;
-{
- int n;
-
- for (n = 0; n < 256; n++)
- fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : " ", table[n],
- n == 255 ? "\n" : (n % 5 == 4 ? ",\n" : ", "));
-}
-#endif /* MAKECRCH */
-
-#else /* !DYNAMIC_CRC_TABLE */
-/* ========================================================================
- * Tables of CRC-32s of all single-byte values, made by make_crc_table().
- */
-#include "crc32.h"
-#endif /* DYNAMIC_CRC_TABLE */
-
-/* =========================================================================
- * This function can be used by asm versions of crc32()
- */
-const unsigned long FAR * ZEXPORT get_crc_table()
-{
-#ifdef DYNAMIC_CRC_TABLE
- if (crc_table_empty)
- make_crc_table();
-#endif /* DYNAMIC_CRC_TABLE */
- return (const unsigned long FAR *)crc_table;
-}
-
-/* ========================================================================= */
-#define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8)
-#define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1
-
-/* ========================================================================= */
-unsigned long ZEXPORT crc32(crc, buf, len)
- unsigned long crc;
- const unsigned char FAR *buf;
- unsigned len;
-{
- if (buf == Z_NULL) return 0UL;
-
-#ifdef DYNAMIC_CRC_TABLE
- if (crc_table_empty)
- make_crc_table();
-#endif /* DYNAMIC_CRC_TABLE */
-
-#ifdef BYFOUR
- if (sizeof(void *) == sizeof(ptrdiff_t)) {
- u4 endian;
-
- endian = 1;
- if (*((unsigned char *)(&endian)))
- return crc32_little(crc, buf, len);
- else
- return crc32_big(crc, buf, len);
- }
-#endif /* BYFOUR */
- crc = crc ^ 0xffffffffUL;
- while (len >= 8) {
- DO8;
- len -= 8;
- }
- if (len) do {
- DO1;
- } while (--len);
- return crc ^ 0xffffffffUL;
-}
-
-#ifdef BYFOUR
-
-/* ========================================================================= */
-#define DOLIT4 c ^= *buf4++; \
- c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \
- crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24]
-#define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4
-
-/* ========================================================================= */
-local unsigned long crc32_little(crc, buf, len)
- unsigned long crc;
- const unsigned char FAR *buf;
- unsigned len;
-{
- register u4 c;
- register const u4 FAR *buf4;
-
- c = (u4)crc;
- c = ~c;
- while (len && ((ptrdiff_t)buf & 3)) {
- c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
- len--;
- }
-
- buf4 = (const u4 FAR *)(const void FAR *)buf;
- while (len >= 32) {
- DOLIT32;
- len -= 32;
- }
- while (len >= 4) {
- DOLIT4;
- len -= 4;
- }
- buf = (const unsigned char FAR *)buf4;
-
- if (len) do {
- c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
- } while (--len);
- c = ~c;
- return (unsigned long)c;
-}
-
-/* ========================================================================= */
-#define DOBIG4 c ^= *++buf4; \
- c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \
- crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24]
-#define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4
-
-/* ========================================================================= */
-local unsigned long crc32_big(crc, buf, len)
- unsigned long crc;
- const unsigned char FAR *buf;
- unsigned len;
-{
- register u4 c;
- register const u4 FAR *buf4;
-
- c = REV((u4)crc);
- c = ~c;
- while (len && ((ptrdiff_t)buf & 3)) {
- c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
- len--;
- }
-
- buf4 = (const u4 FAR *)(const void FAR *)buf;
- buf4--;
- while (len >= 32) {
- DOBIG32;
- len -= 32;
- }
- while (len >= 4) {
- DOBIG4;
- len -= 4;
- }
- buf4++;
- buf = (const unsigned char FAR *)buf4;
-
- if (len) do {
- c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
- } while (--len);
- c = ~c;
- return (unsigned long)(REV(c));
-}
-
-#endif /* BYFOUR */
-
-#define GF2_DIM 32 /* dimension of GF(2) vectors (length of CRC) */
-
-/* ========================================================================= */
-local unsigned long gf2_matrix_times(mat, vec)
- unsigned long *mat;
- unsigned long vec;
-{
- unsigned long sum;
-
- sum = 0;
- while (vec) {
- if (vec & 1)
- sum ^= *mat;
- vec >>= 1;
- mat++;
- }
- return sum;
-}
-
-/* ========================================================================= */
-local void gf2_matrix_square(square, mat)
- unsigned long *square;
- unsigned long *mat;
-{
- int n;
-
- for (n = 0; n < GF2_DIM; n++)
- square[n] = gf2_matrix_times(mat, mat[n]);
-}
-
-/* ========================================================================= */
-uLong ZEXPORT crc32_combine(crc1, crc2, len2)
- uLong crc1;
- uLong crc2;
- z_off_t len2;
-{
- int n;
- unsigned long row;
- unsigned long even[GF2_DIM]; /* even-power-of-two zeros operator */
- unsigned long odd[GF2_DIM]; /* odd-power-of-two zeros operator */
-
- /* degenerate case */
- if (len2 == 0)
- return crc1;
-
- /* put operator for one zero bit in odd */
- odd[0] = 0xedb88320L; /* CRC-32 polynomial */
- row = 1;
- for (n = 1; n < GF2_DIM; n++) {
- odd[n] = row;
- row <<= 1;
- }
-
- /* put operator for two zero bits in even */
- gf2_matrix_square(even, odd);
-
- /* put operator for four zero bits in odd */
- gf2_matrix_square(odd, even);
-
- /* apply len2 zeros to crc1 (first square will put the operator for one
- zero byte, eight zero bits, in even) */
- do {
- /* apply zeros operator for this bit of len2 */
- gf2_matrix_square(even, odd);
- if (len2 & 1)
- crc1 = gf2_matrix_times(even, crc1);
- len2 >>= 1;
-
- /* if no more bits set, then done */
- if (len2 == 0)
- break;
-
- /* another iteration of the loop with odd and even swapped */
- gf2_matrix_square(odd, even);
- if (len2 & 1)
- crc1 = gf2_matrix_times(odd, crc1);
- len2 >>= 1;
-
- /* if no more bits set, then done */
- } while (len2 != 0);
-
- /* return combined crc */
- crc1 ^= crc2;
- return crc1;
-}
git.samba.org / garming / samba-autobuild / .git / blobdiff