Tone.js/test/helper/BufferTest.js

define(["Tone/core/Tone"], function (Tone) {

	var isUndef = Tone.prototype.isUndef;

	//augment the built in functions
	return function(buffer){

		buffer.isSilent = function(channelNum){
			if (isUndef(channelNum)){
				return buffer.toMono().isSilent(0);
			} else {
				var array = buffer.toArray(channelNum);
				for (var i = 0; i < array.length; i++){
					if (array[i] !== 0){
						return false;
					}
				}
				return true;
			}
		};

		/**
		 *  Get the RMS levels for the buffer, returned as an array
		 *  @param  {blockSize}  [blockSize=512]
		 */
		buffer.getRMS = function(blockSize){
			blockSize = blockSize || 512;
			var rms = [];
			var array = buffer.toMono().toArray();
			for (var j = 0; j < array.length; j++){
				var sum = 0;
				if (j >= blockSize){
					for (var k = j - blockSize; k < j; k++){
						sum += array[k] * array[k];
					}
					rms.push(Math.sqrt(sum / blockSize));
				}
			}
			return rms;
		};

		//return the time when the buffer is no longer silent
		buffer.getFirstSoundTime = function(channelNum){
			if (isUndef(channelNum)){
				return buffer.toMono().getFirstSoundTime(0);
			} else {
				var array = buffer.toArray(channelNum);
				for (var i = 0; i < array.length; i++){
					if (array[i] !== 0){
						return i / buffer.context.sampleRate;
					}
				}
				return -1;
			}
		};

		//return the time when the buffer is silent to the remainer of the buffer
		buffer.getLastSoundTime = function(channelNum){
			if (isUndef(channelNum)){
				return buffer.toMono().getLastSoundTime(0);
			} else {
				var array = buffer.toArray(channelNum);
				for (var i = array.length - 1; i >= 0; i--){
					if (array[i] !== 0){
						return i / buffer.context.sampleRate;
					}
				}
				return 0;
			}
		};

		//stops and returns value if callback does
		buffer.forEach = function(callback, start, end){
			var i, ret;
			start = start || 0;
			end = end || buffer.duration;
			start = Math.floor((start / buffer.duration) * buffer.length);
			end = Math.floor((end / buffer.duration) * buffer.length);
			if (buffer.numberOfChannels === 2){
				var arrayL = buffer.toArray(0);
				var arrayR = buffer.toArray(1);
				for (i = start; i < end; i++){
					ret = callback(arrayL[i], arrayR[i], (i/buffer.length) * buffer.duration);
					if (typeof ret !== "undefined"){
						return ret;
					}
				}
				
			} else {
				var array = buffer.toArray();
				for (i = start; i < end; i++){
					ret = callback(array[i], (i/array.length) * buffer.duration);
					if (typeof ret !== "undefined"){
						return ret;
					}
				}
			}
		};

		/**
		 *  Returns the max value in the buffer
		 *  @return  {Number}
		 */
		buffer.max = function(){
			var max = -Infinity;
			buffer.toMono().forEach(function(sample){
				max = Math.max(sample, max);
			});
			return max;
		};

		/**
		 *  Returns the min value in the buffer
		 *  @return  {Number}
		 */
		buffer.min = function(){
			var min = Infinity;
			buffer.toMono().forEach(function(sample){
				min = Math.min(sample, min);
			});
			return min;
		};

		/**
		 *  returns the value if there is a single value the entire buffer
		 */
		buffer.value = function(){
			var val;
			buffer.toMono().forEach(function(sample){
				if (typeof val === "undefined"){
					val = sample;					
				} else if (Math.abs(val - sample) > 0.0001){
					throw new Error("multiple values in buffer");
				}
			});
			return val;
		};
	};
});