/* * 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; }