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offload crc table handling

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This commit is contained in:
Connor Olding 2012-08-05 19:58:43 -07:00
parent a215f38d6d
commit 4e0f09e57f
3 changed files with 26 additions and 38 deletions
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45
crc32.c
View file

@ -5,10 +5,7 @@
* copy of the license along with this program; see the file LICENSE.
*/
#include <stdlib.h>
typedef unsigned long ulong;
#include "crc32.h"
int crc_big_endian = 0;
@ -17,8 +14,6 @@ ulong crc_polynomial = 0x04C11DB7;
enum {
TABLE_SIZE = 0x100
};
static ulong crc_be_table[TABLE_SIZE]; /* big endian */
static ulong crc_le_table[TABLE_SIZE]; /* little endian */
ulong crc_reflect(ulong input)
{
@ -32,47 +27,35 @@ ulong crc_reflect(ulong input)
return reflected;
}
static void crc_fill_table(int big)
/* TODO: test returning array */
void crc_fill_table(ulong *table, int big, ulong polynomial)
{
ulong lsb = (big) ? 1 << 31 : 1; /* least significant bit */
ulong poly = (big) ? crc_polynomial : crc_reflect(crc_polynomial);
ulong *tc = (big) ? crc_be_table : crc_le_table;
ulong poly = (big) ? polynomial : crc_reflect(polynomial);
int c, i;
for (c = 0; c < TABLE_SIZE; c++, tc++) {
*tc = (big) ? c << 24 : c;
for (c = 0; c < TABLE_SIZE; c++, table++) {
*table = (big) ? c << 24 : c;
for (i = 0; i < 8; i++) {
if (*tc & lsb) {
*tc = (big) ? *tc << 1 : *tc >> 1;
*tc ^= poly;
if (*table & lsb) {
*table = (big) ? *table << 1 : *table >> 1;
*table ^= poly;
} else {
*tc = (big) ? *tc << 1 : *tc >> 1;
*table = (big) ? *table << 1 : *table >> 1;
}
*tc &= 0xFFFFFFFF;
*table &= 0xFFFFFFFF;
}
}
}
void crc_be_cycle(ulong *remainder, char c)
void crc_be_cycle(ulong *table, ulong *remainder, char c)
{
static char filled = 0;
ulong byte;
if (!filled) {
crc_fill_table(1);
filled = 1;
}
byte = crc_be_table[((*remainder) >> 24) ^ c];
ulong byte = table[((*remainder) >> 24) ^ c];
*remainder = (((*remainder) << 8) ^ byte) & 0xFFFFFFFF;
}
void crc_le_cycle(ulong *remainder, char c)
void crc_le_cycle(ulong *table, ulong *remainder, char c)
{
static char filled = 0;
ulong byte;
if (!filled) {
crc_fill_table(0);
filled = 1;
}
byte = crc_le_table[((*remainder) ^ c) & 0xFF];
ulong byte = table[((*remainder) ^ c) & 0xFF];
*remainder = ((*remainder) >> 8) ^ byte;
}

7
crc32.h
View file

@ -5,8 +5,9 @@
* copy of the license along with this program; see the file LICENSE.
*/
ulong crc_polynomial;
enum { CRC_TABLE_SIZE = 0x100 };
void crc_be_cycle(ulong *remainder, char c);
void crc_le_cycle(ulong *remainder, char c);
void crc_fill_table(ulong *table, int big, ulong polynomial);
void crc_be_cycle(ulong *table, ulong *remainder, char c);
void crc_le_cycle(ulong *table, ulong *remainder, char c);
ulong crc_reflect(ulong input);

12
main.c
View file

@ -35,6 +35,7 @@ static string_node *input_node = NULL;
static ulong starting = 0xFFFFFFFF;
static char big_endian = 0;
static ulong polynomial = 0x04C11DB7;
static char print_binary = 0;
static char xor_output = 1;
static char reflect_output = 0;
@ -90,7 +91,7 @@ static void handle_flag(char flag, char *(*nextarg)())
break;
case 'p':
next = check_next(flag, nextarg());
crc_polynomial = strtoul(next, NULL, 0);
polynomial = strtoul(next, NULL, 0);
break;
default:
fprintf(stderr, "Unknown flag: -%c\n", flag);
@ -130,9 +131,12 @@ static FILE *open_stream(char *filename)
static ulong cycle_file(FILE *stream)
{
ulong remainder = starting;
void (*cycle)(ulong*, char) = (big_endian) ? crc_be_cycle : crc_le_cycle;
void (*cycle)(ulong*, ulong*, char) =
(big_endian) ? crc_be_cycle : crc_le_cycle;
ulong table[CRC_TABLE_SIZE];
int i, len;
crc_fill_table(table, big_endian, polynomial);
do {
len = fread(buff, 1, BUFFER_SIZE, stream);
if (ferror(stream)) {
@ -141,7 +145,7 @@ static ulong cycle_file(FILE *stream)
}
for (i = 0; i < len; i++)
cycle(&remainder, buff[i]);
cycle(table, &remainder, buff[i]);
} while (!feof(stream));
if (xor_output)