Initial work on Dart bindings for Mojo.

mojo/public/dart/bindings/lib/src/client.dart

+// 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.
+
+part of bindings;
+
+abstract class Client {
+  core.MojoMessagePipeEndpoint _endpoint;
+  core.MojoHandle _handle;
+  List _send_queue;
+  List _completer_queue;
+  var _subscription;
+
+  void handleResponse(MessageReader reader);
+
+  Client(this._endpoint) {
+    _send_queue = [];
+    _completer_queue = [];
+    _handle = new core.MojoHandle(_endpoint.handle);
+    _subscription = _handle.listen((int mojo_handle_signal) {
+      if (core.MojoHandleSignals.isReadable(mojo_handle_signal)) {
+        // Query how many bytes are available.
+        List result = _endpoint.query();
+        if ((result[0] != core.MojoResult.OK) && 
+            (result[0] != core.MojoResult.RESOURCE_EXHAUSTED)) {
+          // If something else happens, it means the handle wasn't really ready
+          // for reading, which indicates a bug in MojoHandle or the
+          // event listener.
+          throw new Exception("bytes query failed: ${result[0]}");
+        }
+        int size = result[1];
+
+        // Read the data.
+        ByteData bytes = new ByteData(size);
+        _endpoint.read(bytes);
+        var message = new Message(bytes, null);
+        var reader = new MessageReader(message);
+
+        // Complete _future_queue[0] with the received string.
+        handleResponse(reader);
+      }
+      if (core.MojoHandleSignals.isWritable(mojo_handle_signal)) {
+        if (_send_queue.length > 0) {
+          List message_completer = _send_queue.removeAt(0);
+          _endpoint.write(message_completer[0].buffer);
+          if (_endpoint.status != core.MojoResult.OK) {
+            throw new Exception("endpoint write failed");
+          }
+          _completer_queue.add(message_completer[1]);
+        }
+        if ((_send_queue.length == 0) && _handle.writeEnabled()) {
+          _handle.toggleWriteEvents();
+        }
+      }
+    }, onDone: () {
+      handle.close();
+    });
+  }
+
+  void close() {
+    _subscription.cancel();
+  }
+
+  Future enqueueMessage(Type t, int name, Object msg) {
+      var builder = new MessageBuilder(name, align(getEncodedSize(t)));
+      builder.encodeStruct(t, msg);
+      var message = builder.finish();
+
+      var completer = new Completer();
+      send_queue.add([message, completer]);
+      if ((send_queue.length > 0) && !handle.writeEnabled()) {
+        handle.toggleWriteEvents();
+      }
+      return completer.future;
+  }
+
+  // We need getters for these because they are abstract in the "Calls"
+  // mixin classes.
+  List get send_queue => _send_queue;
+  core.MojoHandle get handle => _handle;
+
+  // Need a getter for this for access in subclasses.
+  List get completer_queue => _completer_queue;
+}