xz/src/liblzma/check/crc32_small.c

55 lines
1.1 KiB
C

///////////////////////////////////////////////////////////////////////////////
//
/// \file crc32_small.c
/// \brief CRC32 calculation (size-optimized)
//
// This code has been put into the public domain.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
//
///////////////////////////////////////////////////////////////////////////////
#include "check.h"
uint32_t lzma_crc32_table[1][256];
static void
crc32_init(void)
{
static const uint32_t poly32 = UINT32_C(0xEDB88320);
for (size_t b = 0; b < 256; ++b) {
uint32_t r = b;
for (size_t i = 0; i < 8; ++i) {
if (r & 1)
r = (r >> 1) ^ poly32;
else
r >>= 1;
}
lzma_crc32_table[0][b] = r;
}
return;
}
extern LZMA_API(uint32_t)
lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc)
{
mythread_once(crc32_init);
crc = ~crc;
while (size != 0) {
crc = lzma_crc32_table[0][*buf++ ^ (crc & 0xFF)] ^ (crc >> 8);
--size;
}
return ~crc;
}