first draft of serial queue

js/serial_queue.js

@@ -0,0 +1,83 @@
+'use strict';
+
+var helper = helper || {};
+
+helper.mspQueue = (function (serial, MSP) {
+
+    var publicScope = {},
+        privateScope = {};
+
+    privateScope.queue = [];
+
+    privateScope.portInUse = false;
+
+    /**
+     * This method is periodically executed and moves MSP request
+     * from a queue to serial port. This allows to throttle requests,
+     * adjust rate of new frames being sent and prohibit situation in which
+     * serial port is saturated, virtually overloaded, with outgoing data
+     *
+     * This also implements serial port sharing problem: only 1 frame can be transmitted
+     * at once
+     *
+     * MSP class no longer implements blocking, it is queue responsibility
+     */
+    publicScope.executor = function () {
+
+        if (privateScope.portInUse) {
+            return false;
+        }
+
+        var request = privateScope.get();
+
+        if (request !== undefined) {
+
+            /*
+             * Lock serial port as being in use right now
+             */
+            privateScope.portInUse = true;
+
+            /*
+             * Set receive callback here
+             */
+            MSP.putCallback(request);
+
+            //TODO implement timeout scenario
+
+            /*
+             * Send data to serial port
+             */
+            serial.send(request.requestBuffer, function (sendInfo) {
+                if (sendInfo.bytesSent == request.requestBuffer.byteLength) {
+                    /*
+                     * message has been sent, check callbacks and free resource
+                     */
+                    if (request.onSend) {
+                        request.onSend();
+                    }
+                    privateScope.portInUse = false;
+                }
+            });
+        }
+    };
+
+    privateScope.get = function () {
+        return privateScope.queue.shift();
+    };
+
+    publicScope.freeSerialPort = function () {
+        privateScope.portInUse = false;
+    };
+
+    publicScope.put = function (mspRequest) {
+        privateScope.queue.push(mspRequest);
+    };
+
+    publicScope.getLength = function () {
+        return privateScope.queue.length;
+    };
+
+    setInterval(publicScope.executor, 20);
+
+    return publicScope;
+})(serial, MSP);