1 /////////////////////////////////////////////////////////////////////////////// 2 // 3 /// \file crc64_small.c 4 /// \brief CRC64 calculation (size-optimized) 5 // 6 // Author: Lasse Collin 7 // 8 // This file has been put into the public domain. 9 // You can do whatever you want with this file. 10 // 11 /////////////////////////////////////////////////////////////////////////////// 12 13 #include "check.h" 14 15 16 static uint64_t crc64_table[256]; 17 18 19 static void 20 crc64_init(void) 21 { 22 static const uint64_t poly64 = UINT64_C(0xC96C5795D7870F42); 23 24 for (size_t b = 0; b < 256; ++b) { 25 uint64_t r = b; 26 for (size_t i = 0; i < 8; ++i) { 27 if (r & 1) 28 r = (r >> 1) ^ poly64; 29 else 30 r >>= 1; 31 } 32 33 crc64_table[b] = r; 34 } 35 36 return; 37 } 38 39 40 extern LZMA_API(uint64_t) 41 lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc) 42 { 43 mythread_once(crc64_init); 44 45 crc = ~crc; 46 47 while (size != 0) { 48 crc = crc64_table[*buf++ ^ (crc & 0xFF)] ^ (crc >> 8); 49 --size; 50 } 51 52 return ~crc; 53 } 54