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 #ifdef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR 20 __attribute__((__constructor__)) 21 #endif 22 static void 23 crc64_init(void) 24 { 25 static const uint64_t poly64 = UINT64_C(0xC96C5795D7870F42); 26 27 for (size_t b = 0; b < 256; ++b) { 28 uint64_t r = b; 29 for (size_t i = 0; i < 8; ++i) { 30 if (r & 1) 31 r = (r >> 1) ^ poly64; 32 else 33 r >>= 1; 34 } 35 36 crc64_table[b] = r; 37 } 38 39 return; 40 } 41 42 43 extern LZMA_API(uint64_t) 44 lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc) 45 { 46 #ifndef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR 47 mythread_once(crc64_init); 48 #endif 49 50 crc = ~crc; 51 52 while (size != 0) { 53 crc = crc64_table[*buf++ ^ (crc & 0xFF)] ^ (crc >> 8); 54 --size; 55 } 56 57 return ~crc; 58 } 59