Emulation of java.util.Random in Javascript

random.js

class UInt48 {

	constructor(n) {
		if (n instanceof UInt48) {
			Object.assign(this, n);
		} else if (typeof n === 'number') {
			let w0 = n & 0xffff;
			n /= 0x10000;
			let w1 = n & 0xffff;
			n /= 0x10000;
			let w2 = n & 0xffff;
			Object.assign(this, { w2, w1, w0 });
		}
	}

	norm() {
		if (this.w0 >= 0x10000) {
			let carry = Math.floor(this.w0 / 0x10000);
			this.w1 += carry;
			this.w0 &= 0xffff;
		}
		if (this.w1 >= 0x10000) {
			let carry = Math.floor(this.w1 / 0x10000);
			this.w2 += carry;
			this.w1 &= 0xffff;
		}
		this.w2 &= 0xffff;

		return this;
	}

	add(n) {
		let tmp = new UInt48(this);

		tmp.w0 += n.w0;
		tmp.w1 += n.w1;
		tmp.w2 += n.w2;

		return tmp.norm();
	}

	xor(n) {
		let tmp = new UInt48(this);

		tmp.w2 ^= n.w2;
		tmp.w1 ^= n.w1;
		tmp.w0 ^= n.w0;

		return tmp;
	}

	mul(n) {
		let tmp1 = new UInt48(n);
		tmp1.w2 = tmp1.w2 * this.w0;
		tmp1.w1 = tmp1.w1 * this.w0;
		tmp1.w0 = tmp1.w0 * this.w0;
		tmp1.norm();

		let tmp2 = new UInt48(n);
		tmp2.w2 = tmp2.w1 * this.w1;
		tmp2.w1 = tmp2.w0 * this.w1;
		tmp2.w0 = 0;
		tmp2.norm();

		let tmp3 = new UInt48(n);
		tmp3.w2 = tmp3.w0 * this.w2;
		tmp3.w1 = 0;
		tmp3.w0 = 0;
		tmp3.norm();

		return tmp3.add(tmp2).add(tmp1);
	}

	valueOf() {
		return 0x10000 * (0x10000 * this.w2 + this.w1) + this.w0;
	}
}

class Random {

	constructor(seed) {

		const mul = new UInt48(0x5deece66d);
		const add = new UInt48(0xb);

		if (seed === undefined) {
			seed = Math.floor(Math.random() * 0x1000000000000);
		}

		this.setSeed = (n) => {
			seed = new UInt48(n).xor(mul);
		}

		this.setSeed(seed);

		this.next = (bits) => {
			seed = seed.mul(mul).add(add);
			// return ~~(seed / Math.pow(2, 48 - bits));
			return (seed / 0x10000) >> (32 - bits);
		}

		this.nextInt = () => this.next(32);
	}
};