package
{
    import flash.display.Sprite;
    import flash.text.TextField;
    import flash.utils.getTimer;

    public class TestLogarithm extends Sprite
    {
        private static const LOG2:Number = Math.log(2);

        private static const MAX_POW2:int = 1 << 31;

        private var field:TextField = new TextField();

        public function TestLogarithm()
        {
            super();
            test();
        }

        /**
         * Logarithm
         * Average per 1000 iterations: 0.574
         * Loop
         * Average per 1000 iterations: 0.516
         * Switch
         * Average per 1000 iterations: 0.491
         */
        private function test():void
        {
            var numbers:Vector.<int> = new Vector.<int>(1000);
            var timer:int, i:int, average:int, number:int;
            for (; i < 1000; i++)
                numbers[i] = int(Math.random() * int.MAX_VALUE);
            super.addChild(field);
            field.width = 300;
            field.appendText("Logarithm\n");

            for (i = 0; i < 1000; i++)
            {
                timer = getTimer();
                for each (number in numbers)
                {
                    nextPower2Log(number);
                }
                average += getTimer() - timer;
            }

            field.appendText(
                "Average per 1000 iterations: " +
                (average / 1000) + "\n");

            field.appendText("Loop\n");
            average = 0;
            for (i = 0; i < 1000; i++)
            {
                timer = getTimer();
                for each (number in numbers)
                {
                    getNextPowerOfTwo(number);
                }
                average += getTimer() - timer;
            }

            field.appendText(
                "Average per 1000 iterations: " +
                (average / 1000) + "\n");

            field.appendText("Switch\n");
            average = 0;
            for (i = 0; i < 1000; i++)
            {
                timer = getTimer();
                for each (number in numbers)
                {
                    roundToNextPowerTwo(number);
                }
                average += getTimer() - timer;
            }

            field.appendText(
                "Average per 1000 iterations: " +
                (average / 1000) + "\n");
        }

        private static function nextPower2Log(number:int):int
        {
            return 1 << Math.ceil(Math.log(number) / LOG2);
        }

        private static function getNextPowerOfTwo(number:int):int
        {
            if (number > 0 && (number & (number - 1)) == 0)
                return number;
            else
            {
                var result:int = 1;
                while (result < number && result < MAX_POW2)
                    result <<= 1;
                return result;
            }
        }

        private static function roundToNextPowerTwo(number:int):int
        {
            if (2147483648 & number) return 2147483648;
            else if (1073741824 & number) return 1073741824;
            else if (536870912 & number) return 536870912;
            else if (268435456 & number) return 268435456;
            else if (134217728 & number) return 134217728;
            else if (67108864 & number) return 67108864;
            else if (33554432 & number) return 33554432;
            else if (16777216 & number) return 16777216;
            else if (8388608 & number) return 8388608;
            else if (4194304 & number) return 4194304;
            else if (2097152 & number) return 2097152;
            else if (1048576 & number) return 1048576;
            else if (524288 & number) return 524288;
            else if (262144 & number) return 262144;
            else if (131072 & number) return 131072;
            else if (65536 & number) return 65536;
            else if (32768 & number) return 32768;
            else if (16384 & number) return 16384;
            else if (8192 & number) return 8192;
            else if (4096 & number) return 4096;
            else if (2048 & number) return 2048;
            else if (1024 & number) return 1024;
            else if (512 & number) return 512;
            else if (256 & number) return 256;
            else if (128 & number) return 124;
            else if (64 & number) return 64;
            else if (32 & number) return 32;
            else if (16 & number) return 16;
            else if (8 & number) return 8;
            else if (4 & number) return 4;
            else if (2 & number) return 2;
            else if (number > -1) return 1;
            throw "Negative!";
        }
    }
}