mchapman/zlib
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

zlib 1.2.5.1

Browse Source
This commit is contained in:
Mark Adler
2011-09-11 11:04:49 -07:00
parent 9712272c78
commit 10daf0d4d7
55 changed files with 1003 additions and 521 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
crc32.c
View File

@@ -1,5 +1,5 @@
/* crc32.c -- compute the CRC-32 of a data stream
* Copyright (C) 1995-2006, 2010 Mark Adler
* Copyright (C) 1995-2006, 2010, 2011 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
@@ -17,6 +17,8 @@
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().
DYNAMIC_CRC_TABLE and MAKECRCH can be #defined to write out crc32.h.
*/
#ifdef MAKECRCH
@@ -53,6 +55,7 @@
/* Definitions for doing the crc four data bytes at a time. */
#ifdef BYFOUR
typedef u4 crc_table_t;
# define REV(w) ((((w)>>24)&0xff)+(((w)>>8)&0xff00)+ \
(((w)&0xff00)<<8)+(((w)&0xff)<<24))
local unsigned long crc32_little OF((unsigned long,
@@ -61,6 +64,7 @@
const unsigned char FAR *, unsigned));
# define TBLS 8
#else
typedef unsigned long crc_table_t;
# define TBLS 1
#endif /* BYFOUR */
@@ -68,16 +72,16 @@
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));
local uLong crc32_combine_(uLong crc1, uLong crc2, z_off64_t len2);
local uLong crc32_combine_ OF((uLong crc1, uLong crc2, z_off64_t len2));
#ifdef DYNAMIC_CRC_TABLE
local volatile int crc_table_empty = 1;
local unsigned long FAR crc_table[TBLS][256];
local crc_table_t FAR crc_table[TBLS][256];
local void make_crc_table OF((void));
#ifdef MAKECRCH
local void write_table OF((FILE *, const unsigned long FAR *));
local void write_table OF((FILE *, const crc_table_t FAR *));
#endif /* MAKECRCH */
/*
Generate tables for a byte-wise 32-bit CRC calculation on the polynomial:
@@ -107,9 +111,9 @@ local void make_crc_table OF((void));
*/
local void make_crc_table()
{
unsigned long c;
crc_table_t c;
int n, k;
unsigned long poly; /* polynomial exclusive-or pattern */
crc_table_t 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};
@@ -121,13 +125,13 @@ local void make_crc_table()
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]);
poly = 0;
for (n = 0; n < (int)(sizeof(p)/sizeof(unsigned char)); n++)
poly |= (crc_table_t)1 << (31 - p[n]);
/* generate a crc for every 8-bit value */
for (n = 0; n < 256; n++) {
c = (unsigned long)n;
c = (crc_table_t)n;
for (k = 0; k < 8; k++)
c = c & 1 ? poly ^ (c >> 1) : c >> 1;
crc_table[0][n] = c;
@@ -164,7 +168,7 @@ local void make_crc_table()
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, "local const crc_table_t FAR ");
fprintf(out, "crc_table[TBLS][256] =\n{\n {\n");
write_table(out, crc_table[0]);
# ifdef BYFOUR
@@ -184,12 +188,13 @@ local void make_crc_table()
#ifdef MAKECRCH
local void write_table(out, table)
FILE *out;
const unsigned long FAR *table;
const crc_table_t FAR *table;
{
int n;
for (n = 0; n < 256; n++)
fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : " ", table[n],
fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : " ",
(unsigned long)(table[n]),
n == 255 ? "\n" : (n % 5 == 4 ? ",\n" : ", "));
}
#endif /* MAKECRCH */