uint64_t share_to_target(double diff)
{
        int i, shift = 29;
        unsigned char targ[32];
        for (i=0; i<32; i++)
            targ[i]=0;
        double ftarg = (double)0x0000ffff / diff;
        while (ftarg < (double)0x00008000) {
            shift--;
            ftarg *= 256.0;
        }
        while (ftarg >= (double)0x00800000) {
            shift++;
            ftarg /= 256.0;
        }
        uint32_t nBits = (int)ftarg + (shift << 24);
        shift = (nBits >> 24) & 0x00ff;
        nBits &= 0x00FFFFFF;
        targ[shift - 1] = nBits >> 16;
        targ[shift - 2] = nBits >> 8;
        targ[shift - 3] = nBits;
        uint64_t starget = * (uint64_t *) &targ[24];
        return (starget);
}