Modifying and Sending Raw Binary Data in Javascript Example

gistfile1.js

$('#saveSample').click(function () {
	$('#loading').show();
	try {
		var buffer = getFinalSampleBuffer();
	}
	catch (ex) {
		Mashup.ShowMessage(ex);
		return false;
	}

	var request = new XMLHttpRequest();
	request.open("post", "/postUrlHere/", true);
	request.onreadystatechange = function () {
		if (request.readyState == 4 && request.status == 200) {
			callback(request.responseText);
		} else if (request.readyState == 4 && request.status != 200) {
			Mashup.ShowMessage("No Way Jose", "There was a problem saving the sample");
		}
	};
	// Send the file
	request.send(buffer);
});        

//For this gist this function is cut and paste from a larger jquery widget I created, hence the this' that 
//don't quite make sense.  I try to explain the properties as I go
function getFinalSampleBuffer() {
	var startByte = this.playWaveformStart * 4; //start of user selected sample in bytes
	var endByte = this.playWaveformEnd * 4; //end of user selected sample in bytes
	
	//http://stackoverflow.com/questions/6170421/blobbuilder-ruins-binary-data
	var uint8Array = new Uint8Array(this.buffer.getChannelData(0).buffer); //Grabs the Float32Array buffer
	var byteLength = endByte - startByte;
	var sampleByteArray = new Uint8Array(byteLength);
	
	for(var i = startByte; i<endByte;i++) {
		sampleByteArray[i-startByte] = uint8Array[i]; 
	}            
	var BlobBuilderObj = new (window.BlobBuilder || window.WebKitBlobBuilder)();            
	BlobBuilderObj.append(sampleByteArray.buffer);
	var blob = BlobBuilderObj.getBlob('text/plain');
	return blob;
}