1 /////////////////////////////////////////////////////////////////////////////// 2 // 3 /// \file crc32_small.c 4 /// \brief CRC32 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 uint32_t lzma_crc32_table[1][256]; 17 18 19 static void 20 crc32_init(void) 21 { 22 static const uint32_t poly32 = UINT32_C(0xEDB88320); 23 24 for (size_t b = 0; b < 256; ++b) { 25 uint32_t r = b; 26 for (size_t i = 0; i < 8; ++i) { 27 if (r & 1) 28 r = (r >> 1) ^ poly32; 29 else 30 r >>= 1; 31 } 32 33 lzma_crc32_table[0][b] = r; 34 } 35 36 return; 37 } 38 39 40 extern void 41 lzma_crc32_init(void) 42 { 43 mythread_once(crc32_init); 44 return; 45 } 46 47 48 extern LZMA_API(uint32_t) 49 lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc) 50 { 51 lzma_crc32_init(); 52 53 crc = ~crc; 54 55 while (size != 0) { 56 crc = lzma_crc32_table[0][*buf++ ^ (crc & 0xFF)] ^ (crc >> 8); 57 --size; 58 } 59 60 return ~crc; 61 } 62