60 lines
1.2 KiB
C
Executable file
60 lines
1.2 KiB
C
Executable file
/*
|
|
* CRC32 using the polynomial from IEEE-802.3
|
|
*
|
|
* Authors: Lasse Collin <lasse.collin@tukaani.org>
|
|
* Igor Pavlov <http://7-zip.org/>
|
|
*
|
|
* This file has been put into the public domain.
|
|
* You can do whatever you want with this file.
|
|
*/
|
|
|
|
/*
|
|
* This is not the fastest implementation, but it is pretty compact.
|
|
* The fastest versions of xz_crc32() on modern CPUs without hardware
|
|
* accelerated CRC instruction are 3-5 times as fast as this version,
|
|
* but they are bigger and use more memory for the lookup table.
|
|
*/
|
|
|
|
#include "xz_private.h"
|
|
|
|
/*
|
|
* STATIC_RW_DATA is used in the pre-boot environment on some architectures.
|
|
* See <linux/decompress/mm.h> for details.
|
|
*/
|
|
#ifndef STATIC_RW_DATA
|
|
# define STATIC_RW_DATA static
|
|
#endif
|
|
|
|
STATIC_RW_DATA uint32_t xz_crc32_table[256];
|
|
|
|
XZ_EXTERN void xz_crc32_init(void)
|
|
{
|
|
const uint32_t poly = CRC32_POLY_LE;
|
|
|
|
uint32_t i;
|
|
uint32_t j;
|
|
uint32_t r;
|
|
|
|
for (i = 0; i < 256; ++i) {
|
|
r = i;
|
|
for (j = 0; j < 8; ++j)
|
|
r = (r >> 1) ^ (poly & ~((r & 1) - 1));
|
|
|
|
xz_crc32_table[i] = r;
|
|
}
|
|
|
|
return;
|
|
}
|
|
|
|
XZ_EXTERN uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc)
|
|
{
|
|
crc = ~crc;
|
|
|
|
while (size != 0) {
|
|
crc = xz_crc32_table[*buf++ ^ (crc & 0xFF)] ^ (crc >> 8);
|
|
--size;
|
|
}
|
|
|
|
return ~crc;
|
|
}
|