FPGC6/BCC/BDOS/lib/math.c

/*
* Math library
* Contains functions math operation that are not directly supported by the hardware
*/

// Signed Division and Modulo without / and %
word MATH_divmod(word dividend, word divisor, word* rem)
{
    word quotient = 1;

    word neg = 1;
    if ((dividend>0 &&divisor<0)||(dividend<0 && divisor>0))
        neg = -1;

    // Convert to positive
    word tempdividend = (dividend < 0) ? -dividend : dividend;
    word tempdivisor = (divisor < 0) ? -divisor : divisor;

    if (tempdivisor == tempdividend) {
        *rem = 0;
        return 1*neg;
    }
    else if (tempdividend < tempdivisor) {
        if (dividend < 0)
            *rem = tempdividend*neg;
        else
            *rem = tempdividend;
        return 0;
    }
    while (tempdivisor<<1 <= tempdividend)
    {
        tempdivisor = tempdivisor << 1;
        quotient = quotient << 1;
    }

    // Call division recursively
    if(dividend < 0)
        quotient = quotient*neg + MATH_divmod(-(tempdividend-tempdivisor), divisor, rem);
    else
        quotient = quotient*neg + MATH_divmod(tempdividend-tempdivisor, divisor, rem);
     return quotient;
}

word MATH_div(word dividend, word divisor)
{
    word rem = 0;
    return MATH_divmod(dividend, divisor, &rem);
}

word MATH_mod(word dividend, word divisor)
{
    word rem = 0;
    MATH_divmod(dividend, divisor, &rem);
    return rem;
}


// Unsigned Division and Modulo without / and %
word MATH_divmodU(word dividend, word divisor, word mod)
{
    word quotient = 0;
    word remainder = 0;

    if(divisor == 0) 
        return 0;

    word i;
    for(i = 31 ; i >= 0 ; i--)
    {
        quotient = quotient << 1;
        remainder = remainder << 1;
        remainder = remainder | ((dividend & (1 << i)) >> i);

        if((unsigned int) remainder >= (unsigned int) divisor)
        {
            remainder = remainder - divisor;
            quotient = quotient | 1;
        }

        if (i == 0)
            if (mod == 1)
                return remainder;
            else
                return quotient;
    }

    return 0;
}

// Unsigned positive integer division
word MATH_divU(word dividend, word divisor) 
{
    return MATH_divmodU(dividend, divisor, 0);
}

// Unsigned positive integer modulo
word MATH_modU(word dividend, word divisor) 
{
    return MATH_divmodU(dividend, divisor, 1);
}