424 lines
13 KiB
C
424 lines
13 KiB
C
/* 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.
|
|
*/
|
|
|
|
/* @(#) $Id$ */
|
|
|
|
/*
|
|
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 */
|
|
|
|
#include "zutil.h" /* for STDC and FAR definitions */
|
|
|
|
#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;
|
|
}
|