cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

xz_crc32.c (1265B)

      1/*
      2 * CRC32 using the polynomial from IEEE-802.3
      3 *
      4 * Authors: Lasse Collin <lasse.collin@tukaani.org>
      5 *          Igor Pavlov <https://7-zip.org/>
      6 *
      7 * This file has been put into the public domain.
      8 * You can do whatever you want with this file.
      9 */
     10
     11/*
     12 * This is not the fastest implementation, but it is pretty compact.
     13 * The fastest versions of xz_crc32() on modern CPUs without hardware
     14 * accelerated CRC instruction are 3-5 times as fast as this version,
     15 * but they are bigger and use more memory for the lookup table.
     16 */
     17
     18#include "xz_private.h"
     19
     20/*
     21 * STATIC_RW_DATA is used in the pre-boot environment on some architectures.
     22 * See <linux/decompress/mm.h> for details.
     23 */
     24#ifndef STATIC_RW_DATA
     25#	define STATIC_RW_DATA static
     26#endif
     27
     28STATIC_RW_DATA uint32_t xz_crc32_table[256];
     29
     30XZ_EXTERN void xz_crc32_init(void)
     31{
     32	const uint32_t poly = CRC32_POLY_LE;
     33
     34	uint32_t i;
     35	uint32_t j;
     36	uint32_t r;
     37
     38	for (i = 0; i < 256; ++i) {
     39		r = i;
     40		for (j = 0; j < 8; ++j)
     41			r = (r >> 1) ^ (poly & ~((r & 1) - 1));
     42
     43		xz_crc32_table[i] = r;
     44	}
     45
     46	return;
     47}
     48
     49XZ_EXTERN uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc)
     50{
     51	crc = ~crc;
     52
     53	while (size != 0) {
     54		crc = xz_crc32_table[*buf++ ^ (crc & 0xFF)] ^ (crc >> 8);
     55		--size;
     56	}
     57
     58	return ~crc;
     59}