area51/lib/random/random-java.js

Experimental prototypes of alien things built in JavaScript. The bits may end up living in a different package.

//https://android.googlesource.com/platform/libcore/+/184d077ac4e1e008b8ef8a4cf0af60c4d87cfccb/luni/src/main/java/java/util/Random.java
"use strict";

Object.defineProperty(exports, "__esModule", {
	value: true
});
exports["default"] = Random;

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { "default": obj }; }

var _es6SymbolJs = require("../es6/symbol.js");

var _es6SymbolJs2 = _interopRequireDefault(_es6SymbolJs);

var _long = require("long");

var _long2 = _interopRequireDefault(_long);

var serialVersionUID = 3905348978240129500;
var multiplier = 25214903917;

var haveNextNextGaussian = (0, _es6SymbolJs2["default"])();
var nextNextGaussian = (0, _es6SymbolJs2["default"])();
var next = _es6SymbolJs2["default"]["for"]("next");

var seedBase = 0;

function castIntToByte(intValue) {
	var arr = new ArrayBuffer(4);
	var view = new DataView(arr);
	view.setUint8(0, intValue, true);
	return view.getInt8(0);
}

function Random(seed) {
	this[next] = Random.prototype[next];

	if (!seed) {
		this.setSeed(new Date().getTime() + seedBase);
		++seedBase;
	} else {
		this.setSeed(seed);
	}
}

;

Random.prototype = {

	nextBoolean: function nextBoolean() {
		return this[next](1) != 0;
	},
	nextBytes: function nextBytes(buffer) {
		var rand = 0,
		    count = 0,
		    loop = 0;
		while (count < buffer.length) {
			if (loop == 0) {
				rand = this[next](32);
				loop = 3;
			} else {
				loop--;
			}

			buffer[count++] = castIntToByte(rand);
			rand = rand >> 8;
		}
	},
	nextInt: function nextInt(maxValue) {
		var next = _es6SymbolJs2["default"]["for"]("next");
		if (arguments.length == 0) {
			return this[next](32);
		}

		if (arguments.length == 1) {
			var n = maxValue;
			if ((n & -n) === n) {
				// return (int) ( (n * (long)next(31)) >> 31 )
				var next2 = _long2["default"].fromInt(this[next](31));
				return next2.multiply(n).shiftRight(31).toInt();
			}
			var bits, val;
			do {
				bits = this[next](31);
				val = bits % n;
			} while (bits = val + (n - 1) < 0);

			return val;
		}
	},

	nextDouble: function nextDouble() {
		// return ((((long) next(26) << 27) + next(27)) / (double) (1L << 53));

		var long = _long2["default"].fromInt(this[next](26));

		long = long.shiftLeft(27).add(this[next](27)).toNumber();

		return long / 9007199254740992;
	},
	nextFloat: function nextFloat() {
		// (next(24) / 16777216f);
		return this[next](24) / 16777216;
	},
	nextGaussian: function nextGaussian() {
		if (this[haveNextNextGaussian]) {
			this[haveNextNextGaussian] = false;
			return this[nextNextGaussian];
		}

		var v1, v2, s;

		do {
			v1 = 2 * this.nextDouble() - 1;
			v2 = 2 * this.nextDouble() - 1;
			s = v1 * v1 + v2 * v2;
		} while (s >= 1 || s == 0);

		var multiplier = Math.sqrt(-2 * Math.log(s) / s);
		this[nextNextGaussian] = v2 * multiplier;
		return v1 * multiplier;
	},
	nextLong: function nextLong() {
		//  ((long) next(32) << 32) + next(32);
		return _long2["default"].fromInt(this[next](32)).shiftLeft(32).add(this[next](32));
	},
	setSeed: function setSeed(seed) {
		seed = _long2["default"].fromString(seed.toString());
		// 281474976710655 = (1L << 48 - 1)
		this.seed = seed.xor(multiplier).and(281474976710655);
		this[haveNextNextGaussian] = false;
	}
};

Random.prototype[next] = function (bits) {
	var seed = this.seed = this.seed.multiply(multiplier).add(11).and(281474976710655);

	return seed.shiftRight(48 - bits).toInt();
};
module.exports = exports["default"];