@woosh/meep-engine/src/core/binary/ctz32.js

Pure JavaScript game engine. Fully featured and production ready.

/**
 * Count trailing zeroes
 * adapted from https://github.com/git/git/blob/bcd6bc478adc4951d57ec597c44b12ee74bc88fb/ewah/ewok.h#L44
 * @param {number} x expected to be an integer
 * @return {number}
 */
export function ctz32(x) {
    let _x = x;
    let n = 0;

    if ((_x & 0xffff) === 0) {
        _x >>= 16;
        n += 16;
    }

    if ((_x & 0xff) === 0) {
        _x >>= 8;
        n += 8;
    }

    if ((_x & 0xf) === 0) {
        _x >>= 4;
        n += 4;
    }

    if ((_x & 0x3) === 0) {
        _x >>= 2;
        n += 2;
    }

    if ((_x & 0x1) === 0) {
        _x >>= 1;
        n += 1;
    }

    if (_x === 0) {
        n += 1;
    }

    return n;
}