index.js

var int8 = new Int8Array(4);
var int32 = new Int32Array(int8.buffer, 0, 1);
var float32 = new Float32Array(int8.buffer, 0, 1);

/**
 * A singleton for number utilities. 
 * @class NumberUtil
 */
var NumberUtil = function() {

};


/**
 * Returns a float representation of the given int bits. ArrayBuffer
 * is used for the conversion.
 *
 * @method  intBitsToFloat
 * @static
 * @param  {Number} i the int to cast
 * @return {Number}   the float
 */
NumberUtil.intBitsToFloat = function(i) {
	int32[0] = i;
	return float32[0];
};

/**
 * Returns the int bits from the given float. ArrayBuffer is used
 * for the conversion.
 *
 * @method  floatToIntBits
 * @static
 * @param  {Number} f the float to cast
 * @return {Number}   the int bits
 */
NumberUtil.floatToIntBits = function(f) {
	float32[0] = f;
	return int32[0];
};

/**
 * Encodes ABGR int as a float, with slight precision loss.
 *
 * @method  intToFloatColor
 * @static
 * @param {Number} value an ABGR packed integer
 */
NumberUtil.intToFloatColor = function(value) {
	return NumberUtil.intBitsToFloat( value & 0xfeffffff );
};

/**
 * Returns a float encoded ABGR value from the given RGBA
 * bytes (0 - 255). Useful for saving bandwidth in vertex data.
 *
 * @method  colorToFloat
 * @static
 * @param {Number} r the Red byte (0 - 255)
 * @param {Number} g the Green byte (0 - 255)
 * @param {Number} b the Blue byte (0 - 255)
 * @param {Number} a the Alpha byte (0 - 255)
 * @return {Float32}  a Float32 of the RGBA color
 */
NumberUtil.colorToFloat = function(r, g, b, a) {
	var bits = (a << 24 | b << 16 | g << 8 | r);
	return NumberUtil.intToFloatColor(bits);
};

/**
 * Returns true if the number is a power-of-two.
 *
 * @method  isPowerOfTwo
 * @param  {Number}  n the number to test
 * @return {Boolean}   true if power-of-two
 */
NumberUtil.isPowerOfTwo = function(n) {
	return (n & (n - 1)) === 0;
};

/**
 * Returns the next highest power-of-two from the specified number. 
 * 
 * @param  {Number} n the number to test
 * @return {Number}   the next highest power of two
 */
NumberUtil.nextPowerOfTwo = function(n) {
	n--;
	n |= n >> 1;
	n |= n >> 2;
	n |= n >> 4;
	n |= n >> 8;
	n |= n >> 16;
	return n+1;
};

module.exports = NumberUtil;