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zlib 1.2.1.2

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This commit is contained in:
Mark Adler
2011-09-09 23:23:45 -07:00
parent f0e76a6634
commit 7a6955760b
63 changed files with 2462 additions and 505 deletions
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76
crc32.c
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@@ -11,6 +11,14 @@
/* @(#) $Id$ */
/*
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 on thread
to use crc32().
*/
#ifdef MAKECRCH
# include <stdio.h>
# ifndef DYNAMIC_CRC_TABLE
@@ -58,7 +66,7 @@
#ifdef DYNAMIC_CRC_TABLE
local int crc_table_empty = 1;
local volatile int crc_table_empty = 1;
local unsigned long FAR crc_table[TBLS][256];
local void make_crc_table OF((void));
#ifdef MAKECRCH
@@ -95,38 +103,51 @@ local void make_crc_table()
{
unsigned long c;
int n, k;
unsigned long poly; /* polynomial exclusive-or pattern */
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};
/* make exclusive-or pattern from polynomial (0xedb88320UL) */
poly = 0UL;
for (n = 0; n < sizeof(p)/sizeof(unsigned char); n++)
poly |= 1UL << (31 - p[n]);
/* 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;
/* 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;
}
/* 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);
}
}
/* 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;
crc_table_empty = 0;
}
else { /* not first */
/* wait for the other guy to finish (not exactly efficient, but rare) */
while (crc_table_empty)
;
}
#ifdef MAKECRCH
/* write out CRC tables to crc32.h */
@@ -180,9 +201,10 @@ local void write_table(out, table)
const unsigned long FAR * ZEXPORT get_crc_table()
{
#ifdef DYNAMIC_CRC_TABLE
if (crc_table_empty) make_crc_table();
if (crc_table_empty)
make_crc_table();
#endif /* DYNAMIC_CRC_TABLE */
return (const unsigned long FAR *)crc_table;
return (const unsigned long FAR *)crc_table;
}
/* ========================================================================= */