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Sequence numbers for requests #16

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Sequence numbers for requests #16

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50 changes: 23 additions & 27 deletions public/script/main.js
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,9 @@ var reqCorrelationQuery = null;
var curRecords = null;
var curOverlay = null;

var inFlightRequest = null;
var nextSeqNum = 1;
var displayingSeqNum = 0;


// http://stackoverflow.com/questions/149055/how-can-i-format-numbers-as-money-in-javascript
Number.prototype.formatNice = function(c, d, t){
Expand Down Expand Up @@ -308,49 +310,43 @@ function clearCorr() {

// ==== Fetching requested data

function handleNewData(oEvent) {
function handleNewData(oEvent, seqNum) {
// ignore out of order responses
if(seqNum <= displayingSeqNum) return;
displayingSeqNum = seqNum;

var arrayBuffer = oEvent.target.response; // Note: not oReq.responseText
if (arrayBuffer) {
curRecords = readBtsfFile(arrayBuffer);
redisplay();
} else {
console.log("Couldn't fetch file " + url);
}

// TODO: maybe instead of cancelling in flight requests when new ones are sent out
// perhaps we can just always prefer results from requests that were *sent* more recently
// even if they arrive earlier due to weird networking things.
inFlightRequest = null;
}

function fetchCorrelationData(corrBuffer, filter) {
if(inFlightRequest !== null) inFlightRequest.abort();
var xhr = new XMLHttpRequest();
xhr.open("POST", "/find?"+encodeURIComponent(filter), true);
xhr.responseType = "arraybuffer";
xhr.onload = handleNewData;
xhr.send(new DataView(corrBuffer));
inFlightRequest = xhr;
}
function fetchData(filter, corrBuffer) {
var thisRequest = nextSeqNum;
nextSeqNum += 1;

function fetchRawData(filter) {
if(inFlightRequest !== null) inFlightRequest.abort();
var xhr = new XMLHttpRequest();
xhr.open("GET", "/raw?"+encodeURIComponent(filter), true);
var endpoint = (corrBuffer !== null) ? "/find?" : "/raw?";
xhr.open("POST", endpoint+encodeURIComponent(filter), true);
xhr.responseType = "arraybuffer";
xhr.onload = handleNewData;
xhr.send(null);
inFlightRequest = xhr;
}
xhr.onload = function(oEvent) {
handleNewData(oEvent, thisRequest);
}

function updateFromServer() {
if(reqCorrelationQuery !== null) {
fetchCorrelationData(reqCorrelationQuery, reqFilter);
if(corrBuffer !== null) {
xhr.send(new DataView(corrBuffer));
} else {
fetchRawData(reqFilter);
xhr.send(null);
}
}

function updateFromServer() {
fetchData(reqFilter, reqCorrelationQuery);
}

function init() {
updateFromServer();
document.getElementById("filter-box").focus();
Expand Down