1*4882a593Smuzhiyun /* 2*4882a593Smuzhiyun * CRC32 using the polynomial from IEEE-802.3 3*4882a593Smuzhiyun * 4*4882a593Smuzhiyun * Authors: Lasse Collin <lasse.collin@tukaani.org> 5*4882a593Smuzhiyun * Igor Pavlov <https://7-zip.org/> 6*4882a593Smuzhiyun * 7*4882a593Smuzhiyun * This file has been put into the public domain. 8*4882a593Smuzhiyun * You can do whatever you want with this file. 9*4882a593Smuzhiyun */ 10*4882a593Smuzhiyun 11*4882a593Smuzhiyun /* 12*4882a593Smuzhiyun * This is not the fastest implementation, but it is pretty compact. 13*4882a593Smuzhiyun * The fastest versions of xz_crc32() on modern CPUs without hardware 14*4882a593Smuzhiyun * accelerated CRC instruction are 3-5 times as fast as this version, 15*4882a593Smuzhiyun * but they are bigger and use more memory for the lookup table. 16*4882a593Smuzhiyun */ 17*4882a593Smuzhiyun 18*4882a593Smuzhiyun #include "xz_private.h" 19*4882a593Smuzhiyun 20*4882a593Smuzhiyun /* 21*4882a593Smuzhiyun * STATIC_RW_DATA is used in the pre-boot environment on some architectures. 22*4882a593Smuzhiyun * See <linux/decompress/mm.h> for details. 23*4882a593Smuzhiyun */ 24*4882a593Smuzhiyun #ifndef STATIC_RW_DATA 25*4882a593Smuzhiyun # define STATIC_RW_DATA static 26*4882a593Smuzhiyun #endif 27*4882a593Smuzhiyun 28*4882a593Smuzhiyun STATIC_RW_DATA uint32_t xz_crc32_table[256]; 29*4882a593Smuzhiyun xz_crc32_init(void)30*4882a593SmuzhiyunXZ_EXTERN void xz_crc32_init(void) 31*4882a593Smuzhiyun { 32*4882a593Smuzhiyun const uint32_t poly = CRC32_POLY_LE; 33*4882a593Smuzhiyun 34*4882a593Smuzhiyun uint32_t i; 35*4882a593Smuzhiyun uint32_t j; 36*4882a593Smuzhiyun uint32_t r; 37*4882a593Smuzhiyun 38*4882a593Smuzhiyun for (i = 0; i < 256; ++i) { 39*4882a593Smuzhiyun r = i; 40*4882a593Smuzhiyun for (j = 0; j < 8; ++j) 41*4882a593Smuzhiyun r = (r >> 1) ^ (poly & ~((r & 1) - 1)); 42*4882a593Smuzhiyun 43*4882a593Smuzhiyun xz_crc32_table[i] = r; 44*4882a593Smuzhiyun } 45*4882a593Smuzhiyun 46*4882a593Smuzhiyun return; 47*4882a593Smuzhiyun } 48*4882a593Smuzhiyun xz_crc32(const uint8_t * buf,size_t size,uint32_t crc)49*4882a593SmuzhiyunXZ_EXTERN uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc) 50*4882a593Smuzhiyun { 51*4882a593Smuzhiyun crc = ~crc; 52*4882a593Smuzhiyun 53*4882a593Smuzhiyun while (size != 0) { 54*4882a593Smuzhiyun crc = xz_crc32_table[*buf++ ^ (crc & 0xFF)] ^ (crc >> 8); 55*4882a593Smuzhiyun --size; 56*4882a593Smuzhiyun } 57*4882a593Smuzhiyun 58*4882a593Smuzhiyun return ~crc; 59*4882a593Smuzhiyun } 60