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Diffstat (limited to 'dep/src/zlib/crc32.c')
-rw-r--r--dep/src/zlib/crc32.c56
1 files changed, 56 insertions, 0 deletions
diff --git a/dep/src/zlib/crc32.c b/dep/src/zlib/crc32.c
index 8838c354a4e..f658a9ef55e 100644
--- a/dep/src/zlib/crc32.c
+++ b/dep/src/zlib/crc32.c
@@ -8,7 +8,9 @@
* instead of four steps with four exclusive-ors. This results in 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
@@ -16,14 +18,18 @@
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 */
@@ -44,6 +50,7 @@
# 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)+ \
@@ -56,11 +63,14 @@
#else
# define TBLS 1
#endif /* BYFOUR */
+
/* Local functions for crc concatenation */
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));
+
#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));
@@ -70,6 +80,7 @@ local void make_crc_table OF((void));
/*
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
@@ -77,6 +88,7 @@ local void make_crc_table OF((void));
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
@@ -84,6 +96,7 @@ local void make_crc_table OF((void));
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
@@ -98,15 +111,18 @@ local void make_crc_table()
/* 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;
@@ -114,6 +130,7 @@ local void make_crc_table()
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 */
@@ -127,6 +144,7 @@ local void make_crc_table()
}
}
#endif /* BYFOUR */
+
crc_table_empty = 0;
}
else { /* not first */
@@ -134,10 +152,12 @@ local void make_crc_table()
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");
@@ -158,23 +178,27 @@ local void make_crc_table()
}
#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()
*/
@@ -186,9 +210,11 @@ const unsigned long FAR * ZEXPORT get_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;
@@ -196,13 +222,16 @@ unsigned long ZEXPORT crc32(crc, buf, len)
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);
@@ -220,12 +249,15 @@ unsigned long ZEXPORT crc32(crc, buf, len)
} 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;
@@ -234,12 +266,14 @@ local unsigned long crc32_little(crc, buf, 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 *)(const void FAR *)buf;
while (len >= 32) {
DOLIT32;
@@ -250,17 +284,20 @@ local unsigned long crc32_little(crc, buf, len)
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;
@@ -269,12 +306,14 @@ local unsigned long crc32_big(crc, buf, 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 *)(const void FAR *)buf;
buf4--;
while (len >= 32) {
@@ -287,20 +326,25 @@ local unsigned long crc32_big(crc, buf, len)
}
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 */
+
#define GF2_DIM 32 /* dimension of GF(2) vectors (length of CRC) */
+
/* ========================================================================= */
local unsigned long gf2_matrix_times(mat, vec)
unsigned long *mat;
unsigned long vec;
{
unsigned long sum;
+
sum = 0;
while (vec) {
if (vec & 1)
@@ -310,15 +354,18 @@ local unsigned long gf2_matrix_times(mat, vec)
}
return sum;
}
+
/* ========================================================================= */
local void gf2_matrix_square(square, mat)
unsigned long *square;
unsigned long *mat;
{
int n;
+
for (n = 0; n < GF2_DIM; n++)
square[n] = gf2_matrix_times(mat, mat[n]);
}
+
/* ========================================================================= */
uLong ZEXPORT crc32_combine(crc1, crc2, len2)
uLong crc1;
@@ -329,9 +376,11 @@ uLong ZEXPORT crc32_combine(crc1, crc2, len2)
unsigned long row;
unsigned long even[GF2_DIM]; /* even-power-of-two zeros operator */
unsigned long odd[GF2_DIM]; /* odd-power-of-two zeros operator */
+
/* degenerate case */
if (len2 == 0)
return crc1;
+
/* put operator for one zero bit in odd */
odd[0] = 0xedb88320L; /* CRC-32 polynomial */
row = 1;
@@ -339,10 +388,13 @@ uLong ZEXPORT crc32_combine(crc1, crc2, len2)
odd[n] = row;
row <<= 1;
}
+
/* put operator for two zero bits in even */
gf2_matrix_square(even, odd);
+
/* put operator for four zero bits in odd */
gf2_matrix_square(odd, even);
+
/* apply len2 zeros to crc1 (first square will put the operator for one
zero byte, eight zero bits, in even) */
do {
@@ -351,16 +403,20 @@ uLong ZEXPORT crc32_combine(crc1, crc2, len2)
if (len2 & 1)
crc1 = gf2_matrix_times(even, crc1);
len2 >>= 1;
+
/* if no more bits set, then done */
if (len2 == 0)
break;
+
/* another iteration of the loop with odd and even swapped */
gf2_matrix_square(odd, even);
if (len2 & 1)
crc1 = gf2_matrix_times(odd, crc1);
len2 >>= 1;
+
/* if no more bits set, then done */
} while (len2 != 0);
+
/* return combined crc */
crc1 ^= crc2;
return crc1;