/* crc32.c -- compute the CRC-32 of a data stream
- * Copyright (C) 1995-2006, 2010, 2011 Mark Adler
+ * Copyright (C) 1995-2006, 2010, 2011, 2012 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
#include "zutil.h" /* for STDC and FAR definitions */
-#define local static
-
-/* Find a four-byte integer type for crc32_little() and crc32_big(). */
-#ifdef Z_SOLO
-# define NOBYFOUR
-#endif
-#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. */
+#if !defined(NOBYFOUR) && defined(Z_U4)
+# define BYFOUR
+#endif
#ifdef BYFOUR
- typedef u4 crc_table_t;
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
- typedef unsigned long crc_table_t;
# define TBLS 1
#endif /* BYFOUR */
#ifdef DYNAMIC_CRC_TABLE
local volatile int crc_table_empty = 1;
-local crc_table_t FAR crc_table[TBLS][256];
+local z_crc_t FAR crc_table[TBLS][256];
local void make_crc_table OF((void));
#ifdef MAKECRCH
- local void write_table OF((FILE *, const crc_table_t FAR *));
+ local void write_table OF((FILE *, const z_crc_t FAR *));
#endif /* MAKECRCH */
/*
Generate tables for a byte-wise 32-bit CRC calculation on the polynomial:
*/
local void make_crc_table()
{
- crc_table_t c;
+ z_crc_t c;
int n, k;
- crc_table_t poly; /* polynomial exclusive-or pattern */
+ z_crc_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};
/* make exclusive-or pattern from polynomial (0xedb88320UL) */
poly = 0;
for (n = 0; n < (int)(sizeof(p)/sizeof(unsigned char)); n++)
- poly |= (crc_table_t)1 << (31 - p[n]);
+ poly |= (z_crc_t)1 << (31 - p[n]);
/* generate a crc for every 8-bit value */
for (n = 0; n < 256; n++) {
- c = (crc_table_t)n;
+ c = (z_crc_t)n;
for (k = 0; k < 8; k++)
c = c & 1 ? poly ^ (c >> 1) : c >> 1;
crc_table[0][n] = c;
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 crc_table_t FAR ");
+ fprintf(out, "local const z_crc_t FAR ");
fprintf(out, "crc_table[TBLS][256] =\n{\n {\n");
write_table(out, crc_table[0]);
# ifdef BYFOUR
#ifdef MAKECRCH
local void write_table(out, table)
FILE *out;
- const crc_table_t FAR *table;
+ const z_crc_t FAR *table;
{
int n;
/* =========================================================================
* This function can be used by asm versions of crc32()
*/
-const unsigned long FAR * ZEXPORT get_crc_table()
+const z_crc_t 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;
+ return (const z_crc_t FAR *)crc_table;
}
/* ========================================================================= */
#ifdef BYFOUR
if (sizeof(void *) == sizeof(ptrdiff_t)) {
- u4 endian;
+ z_crc_t endian;
endian = 1;
if (*((unsigned char *)(&endian)))
#ifdef BYFOUR
+/*
+ This BYFOUR code accesses the passed unsigned char * buffer with a 32-bit
+ integer pointer type. This violates the strict aliasing rule, where a
+ compiler can assume, for optimization purposes, that two pointers to
+ fundamentally different types won't ever point to the same memory. This can
+ manifest as a problem only if one of the pointers is written to. This code
+ only reads from those pointers. So long as this code remains isolated in
+ this compilation unit, there won't be a problem. For this reason, this code
+ should not be copied and pasted into a compilation unit in which other code
+ writes to the buffer that is passed to these routines.
+ */
+
/* ========================================================================= */
#define DOLIT4 c ^= *buf4++; \
c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \
const unsigned char FAR *buf;
unsigned len;
{
- register u4 c;
- register const u4 FAR *buf4;
+ register z_crc_t c;
+ register const z_crc_t FAR *buf4;
- c = (u4)crc;
+ c = (z_crc_t)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;
+ buf4 = (const z_crc_t FAR *)(const void FAR *)buf;
while (len >= 32) {
DOLIT32;
len -= 32;
}
/* ========================================================================= */
-#define DOBIG4 c ^= *++buf4; \
+#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
const unsigned char FAR *buf;
unsigned len;
{
- register u4 c;
- register const u4 FAR *buf4;
+ register z_crc_t c;
+ register const z_crc_t FAR *buf4;
- c = ZSWAP32((u4)crc);
+ c = ZSWAP32((z_crc_t)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--;
+ buf4 = (const z_crc_t FAR *)(const void FAR *)buf;
while (len >= 32) {
DOBIG32;
len -= 32;
DOBIG4;
len -= 4;
}
- buf4++;
buf = (const unsigned char FAR *)buf4;
if (len) do {
projects / zlib.git / blobdiff