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Diffstat (limited to 'src/zlib/crc32.c')
| -rw-r--r-- | src/zlib/crc32.c | 333 |
1 files changed, 0 insertions, 333 deletions
diff --git a/src/zlib/crc32.c b/src/zlib/crc32.c deleted file mode 100644 index b39c7e125..000000000 --- a/src/zlib/crc32.c +++ /dev/null @@ -1,333 +0,0 @@ -/* crc32.c -- compute the CRC-32 of a data stream - * 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. - */ - -/* @(#) $Id$ */ - -/* - 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 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 *)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 */ |