/**
 * Gets a bitmasked value in from an integer. If the shift is omitted, it will
 * be deduced from the mask.
 *
 * @arg 0 - the variable
 * @arg 1 - mask
 * @arg 2 - shift
 */
function	script	bitwise_get	{
    .@shift = getarg(2, 0);

    if (getargcount() < 3) {
        // guess the shift from the mask:
        for (.@shift = 0; .@shift < 32; ++.@shift) {
            if ((getarg(1) & (1 << .@shift)) != 0) {
                break;
            }
        }
    }

    return (getarg(0) & getarg(1)) >> .@shift;
}

/**
 * sets a bitmasked value in a variable
 *
 * @arg 0 - the target variable
 * @arg 1 - mask
 * @arg 2 - shift
 * @arg 3 - new value
 * @return a reference to the variable
 */
function	script	bitwise_set	{
    if (getargcount() < 4) {
        // guess the shift from the mask:
        for (.@shift = 0; .@shift < 32; ++.@shift) {
            if ((getarg(1) & (1 << .@shift)) != 0) {
                break;
            }
        }

        return set(getarg(0), (getarg(0) & ~(getarg(1))) | (getarg(2, 0) << .@shift));
    }

    return set(getarg(0), (getarg(0) & ~(getarg(1))) | (getarg(3, 0) << getarg(2, 0)));
}