source: vbox/trunk/src/libs/liblzma-5.4.1/check/crc64_small.c

///////////////////////////////////////////////////////////////////////////////
//
/// \file       crc64_small.c
/// \brief      CRC64 calculation (size-optimized)
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "check.h"


static uint64_t crc64_table[256];


#ifdef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
__attribute__((__constructor__))
#endif
static void
crc64_init(void)
{
        static const uint64_t poly64 = UINT64_C(0xC96C5795D7870F42);

        for (size_t b = 0; b < 256; ++b) {
                uint64_t r = b;
                for (size_t i = 0; i < 8; ++i) {
                        if (r & 1)
                                r = (r >> 1) ^ poly64;
                        else
                                r >>= 1;
                }

                crc64_table[b] = r;
        }

        return;
}


extern LZMA_API(uint64_t)
lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc)
{
#ifndef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
        mythread_once(crc64_init);
#endif

        crc = ~crc;

        while (size != 0) {
                crc = crc64_table[*buf++ ^ (crc & 0xFF)] ^ (crc >> 8);
                --size;
        }

        return ~crc;
}