rABS vs binary arithmetic range coder

=======================

    if ( x < (1<<32) )
    {
        x <<= 32;
        x |= *dword_in_ptr++;
    }

    uint64 xm = x & 4095;

    if ( xm < p0 )
    {
        x = p0 * (x >> 12) + xm;

        p0 += (4096 - p0) >> 5;

        return 0;
    }
    else
    {
        x = (4096 - p0) * (x>>12) + xm - p0;

        p0 -= p0 >> 5;

        return 1;
    }

=======================

    if ( range < (1<<32) )
    {
        code <<= 32; range <<= 32;
        code |= *dword_in_ptr++;
    }

    uint64 p0range = p0 * (range >> 12);

    if ( code < p0range )
    {
        range = p0range;

        p0 += (4096 - p0) >> 5;

        return 0;
    }
    else
    {
        code -= p0range;
        range -= p0range;

        p0 -= p0 >> 5;

        return 1;
    }

=======================