linux/lib/xz/xz_crc32.c
Alexander A. Klimov d89775fc92 lib/: replace HTTP links with HTTPS ones
Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Signed-off-by: Alexander A. Klimov <grandmaster@al2klimov.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Coly Li <colyli@suse.de>	[crc64.c]
Link: http://lkml.kernel.org/r/20200726112154.16510-1-grandmaster@al2klimov.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-12 10:58:00 -07:00

60 lines
1.2 KiB
C

/*
* CRC32 using the polynomial from IEEE-802.3
*
* Authors: Lasse Collin <lasse.collin@tukaani.org>
* Igor Pavlov <https://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;
}