163dab8eeSAdrian Chadd /* 263dab8eeSAdrian Chadd * CRC32 using the polynomial from IEEE-802.3 363dab8eeSAdrian Chadd * 463dab8eeSAdrian Chadd * Authors: Lasse Collin <lasse.collin@tukaani.org> 5*cd3a777bSXin LI * Igor Pavlov <https://7-zip.org/> 663dab8eeSAdrian Chadd * 763dab8eeSAdrian Chadd * This file has been put into the public domain. 863dab8eeSAdrian Chadd * You can do whatever you want with this file. 963dab8eeSAdrian Chadd */ 1063dab8eeSAdrian Chadd 1163dab8eeSAdrian Chadd /* 1263dab8eeSAdrian Chadd * This is not the fastest implementation, but it is pretty compact. 1363dab8eeSAdrian Chadd * The fastest versions of xz_crc32() on modern CPUs without hardware 1463dab8eeSAdrian Chadd * accelerated CRC instruction are 3-5 times as fast as this version, 1563dab8eeSAdrian Chadd * but they are bigger and use more memory for the lookup table. 1663dab8eeSAdrian Chadd */ 1763dab8eeSAdrian Chadd 1863dab8eeSAdrian Chadd #include "xz_private.h" 1963dab8eeSAdrian Chadd 2063dab8eeSAdrian Chadd /* 2163dab8eeSAdrian Chadd * STATIC_RW_DATA is used in the pre-boot environment on some architectures. 2263dab8eeSAdrian Chadd * See <linux/decompress/mm.h> for details. 2363dab8eeSAdrian Chadd */ 2463dab8eeSAdrian Chadd #ifndef STATIC_RW_DATA 2563dab8eeSAdrian Chadd # define STATIC_RW_DATA static 2663dab8eeSAdrian Chadd #endif 2763dab8eeSAdrian Chadd 2863dab8eeSAdrian Chadd STATIC_RW_DATA uint32_t xz_crc32_table[256]; 2963dab8eeSAdrian Chadd xz_crc32_init(void)3063dab8eeSAdrian ChaddXZ_EXTERN void xz_crc32_init(void) 3163dab8eeSAdrian Chadd { 3263dab8eeSAdrian Chadd const uint32_t poly = 0xEDB88320; 3363dab8eeSAdrian Chadd 3463dab8eeSAdrian Chadd uint32_t i; 3563dab8eeSAdrian Chadd uint32_t j; 3663dab8eeSAdrian Chadd uint32_t r; 3763dab8eeSAdrian Chadd 3863dab8eeSAdrian Chadd for (i = 0; i < 256; ++i) { 3963dab8eeSAdrian Chadd r = i; 4063dab8eeSAdrian Chadd for (j = 0; j < 8; ++j) 4163dab8eeSAdrian Chadd r = (r >> 1) ^ (poly & ~((r & 1) - 1)); 4263dab8eeSAdrian Chadd 4363dab8eeSAdrian Chadd xz_crc32_table[i] = r; 4463dab8eeSAdrian Chadd } 4563dab8eeSAdrian Chadd 4663dab8eeSAdrian Chadd return; 4763dab8eeSAdrian Chadd } 4863dab8eeSAdrian Chadd xz_crc32(const uint8_t * buf,size_t size,uint32_t crc)4963dab8eeSAdrian ChaddXZ_EXTERN uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc) 5063dab8eeSAdrian Chadd { 5163dab8eeSAdrian Chadd crc = ~crc; 5263dab8eeSAdrian Chadd 5363dab8eeSAdrian Chadd while (size != 0) { 5463dab8eeSAdrian Chadd crc = xz_crc32_table[*buf++ ^ (crc & 0xFF)] ^ (crc >> 8); 5563dab8eeSAdrian Chadd --size; 5663dab8eeSAdrian Chadd } 5763dab8eeSAdrian Chadd 5863dab8eeSAdrian Chadd return ~crc; 5963dab8eeSAdrian Chadd } 60