Mojo: add javascript bindings for request/response

mojo/public/bindings/js/router.js

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+define("mojo/public/bindings/js/router", [
+  "mojo/public/bindings/js/codec",
+  "mojo/public/bindings/js/connector",
+], function(codec, connector) {
+
+  function Router(handle) {
+    this.connector_ = new connector.Connector(handle);
+    this.incomingReceiver_ = null;
+    this.nextRequestID_ = 0;
+    this.responders_ = {};
+
+    this.connector_.setIncomingReceiver({
+        accept: this.handleIncomingMessage_.bind(this),
+    });
+  }
+
+  Router.prototype.close = function() {
+    this.connector_.close();
+  };

[abarth-chromium, 2014/03/26 19:05:45]

Should we drop the responders_ too?

+
+  Router.prototype.accept = function(message) {
+    this.connector_.accept(message);
+  };
+
+  Router.prototype.acceptWithResponder = function(message, responder) {
+    // Reserve 0 in case we want it to convey special meaning in the future.
+    var requestID = this.nextRequestID_++;
+    if (requestID == 0)

[Matt Perry, 2014/03/26 18:19:43]

why not just start nextRequestId at 1? or are you worried about wraparound? I
think JS ints have 52 bits of precision (it's just a double), so that'd take a
while.

+      requestID = this.nextRequestID_++;
+
+    message.setRequestID(requestID);
+    this.connector_.accept(message);
+
+    this.responders_[requestID] = responder;
+  };
+
+  Router.prototype.setIncomingReceiver = function(receiver) {
+    this.incomingReceiver_ = receiver;
+  };
+
+  Router.prototype.handleIncomingMessage_ = function(message) {
+    var flags = message.getFlags();
+    if (flags & codec.kMessageExpectsResponse) {
+      if (this.incomingReceiver_) {
+        this.incomingReceiver_.acceptWithResponder(message, this);
+      } else {
+        // If we receive a request expecting a response when the client is not
+        // listening, then we have no choice but to tear down the pipe.
+        this.close();
+      }
+    } else if (flags & codec.kMessageIsResponse) {
+      var reader = new codec.MessageReader(message);
+      var requestID = reader.requestID;
+      var responder = this.responders_[requestID];
+      delete this.responders_[requestID];
+      responder.accept(message);
+    } else {
+      if (this.incomingReceiver_)
+        this.incomingReceiver_.accept(message);
+    }
+  };
+
+  var exports = {};
+  exports.Router = Router;
+  return exports;
+});