/* crc32.c -- compute the CRC-32 of a data stream
- * Copyright (C) 1995-1998 Mark Adler
+ * Copyright (C) 1995-2003 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 about a factor
+ * of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
*/
/* @(#) $Id$ */
-#include "../zlib/zlib.h"
+/*
+ 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 */
+
#ifdef DYNAMIC_CRC_TABLE
-local int crc_table_empty = 1;
-local uLongf crc_table[256];
+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 a table for a byte-wise 32-bit CRC calculation on the polynomial:
+ 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,
out is a one). We start with the highest power (least significant bit) of
q and repeat for all eight bits of q.
- The table is simply the CRC of all possible eight bit values. This is all
- the information needed to generate CRC's on data a byte at a time for all
- combinations of CRC register values and incoming bytes.
+ 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()
{
- uLong c;
- int n, k;
- uLong poly; /* polynomial exclusive-or pattern */
- /* terms of polynomial defining this crc (except x^32): */
- static const Byte p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
-
- /* make exclusive-or pattern from polynomial (0xedb88320L) */
- poly = 0L;
- for (n = 0; n < sizeof(p)/sizeof(Byte); n++)
- poly |= 1L << (31 - p[n]);
-
- for (n = 0; n < 256; n++)
- {
- c = (uLong)n;
- for (k = 0; k < 8; k++)
- c = c & 1 ? poly ^ (c >> 1) : c >> 1;
- crc_table[n] = c;
- }
- crc_table_empty = 0;
+ 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 */
}
-#else
+
+#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 */
/* ========================================================================
- * Table of CRC-32's of all single-byte values (made by make_crc_table)
+ * Tables of CRC-32s of all single-byte values, made by make_crc_table().
*/
-local const uLongf crc_table[256] = {
- 0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
- 0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
- 0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
- 0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
- 0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
- 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
- 0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
- 0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
- 0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
- 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
- 0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
- 0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
- 0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
- 0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
- 0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
- 0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
- 0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
- 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
- 0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
- 0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
- 0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
- 0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
- 0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
- 0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
- 0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
- 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
- 0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
- 0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
- 0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
- 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
- 0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
- 0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
- 0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
- 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
- 0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
- 0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
- 0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
- 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
- 0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
- 0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
- 0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
- 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
- 0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
- 0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
- 0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
- 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
- 0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
- 0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
- 0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
- 0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
- 0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
- 0x2d02ef8dL
-};
-#endif
+#include "crc32.h"
+#endif /* DYNAMIC_CRC_TABLE */
/* =========================================================================
* This function can be used by asm versions of crc32()
*/
-const uLongf * ZEXPORT get_crc_table()
+const unsigned long FAR * ZEXPORT get_crc_table()
{
#ifdef DYNAMIC_CRC_TABLE
- if (crc_table_empty) make_crc_table();
-#endif
- return (const uLongf *)crc_table;
+ if (crc_table_empty)
+ make_crc_table();
+#endif /* DYNAMIC_CRC_TABLE */
+ return (const unsigned long FAR *)crc_table;
}
/* ========================================================================= */
-#define DO1(buf) crc = crc_table[((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8);
-#define DO2(buf) DO1(buf); DO1(buf);
-#define DO4(buf) DO2(buf); DO2(buf);
-#define DO8(buf) DO4(buf); DO4(buf);
+#define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8)
+#define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1
/* ========================================================================= */
-#if defined(__VISAGECPP__) /* Visualage can't handle this antiquated interface */
-uLong ZEXPORT crc32(uLong crc, const Bytef* buf, uInt len)
-#else
-uLong ZEXPORT crc32(crc, buf, len)
- uLong crc;
- const Bytef *buf;
- uInt len;
-#endif
+unsigned long ZEXPORT crc32(crc, buf, len)
+ unsigned long crc;
+ const unsigned char FAR *buf;
+ unsigned len;
{
- if (buf == Z_NULL) return 0L;
+ if (buf == Z_NULL) return 0UL;
+
#ifdef DYNAMIC_CRC_TABLE
if (crc_table_empty)
- make_crc_table();
-#endif
- crc = crc ^ 0xffffffffL;
- while (len >= 8)
- {
- DO8(buf);
- len -= 8;
+ 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(buf);
+ DO1;
} while (--len);
- return crc ^ 0xffffffffL;
+ 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 *)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 *)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 */
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