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diff --git a/mojo/public/dart/src/interface.dart b/mojo/public/dart/src/interface.dart
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+++ b/mojo/public/dart/src/interface.dart
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+// 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 Interface {
+  core.MojoMessagePipeEndpoint _endpoint;
+  core.MojoHandle _handle;
+  List _sendQueue;
+
+  Message handleMessage(MessageReader reader, Function messageHandler);
+
+  Interface(this._endpoint) {
+    _sendQueue = [];
+    _handle = new core.MojoHandle(_endpoint.handle);
+  }
+
+  StreamSubscription<int> listen(Function messageHandler) {
+    return _handle.listen((int mojoSignal) {
+      if (core.MojoHandleSignals.isReadable(mojoSignal)) {
+        // Query how many bytes are available.
+        var result = _endpoint.query();
+        if (!result.status.isOk && !result.status.isResourceExhausted) {
+          // 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("message pipe query failed: ${result.status}");
+        }
+
+        // Read the data and view as a message.
+        var bytes = new ByteData(result.bytesRead);
+        var handles = new List<RawMojoHandle>(result.handlesRead);
+        result = _endpoint.read(bytes, result.bytesRead, handles);
+        if (!result.status.isOk && !result.status.isResourceExhausted) {
+          // 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("message pipe read failed: ${result.status}");
+        }
+        var message = new Message(bytes, handles);
+        var reader = new MessageReader(message);
+
+        // Prepare the response.
+        var response_message = handleMessage(reader, messageHandler);
+        // If there's a response, queue it up for sending.
+        if (response_message != null) {
+          _sendQueue.add(response_message);
+          if ((_sendQueue.length > 0) && !_handle.writeEnabled()) {
+            _handle.enableWriteEvents();
+          }
+        }
+      }
+      if (core.MojoHandleSignals.isWritable(mojoSignal)) {
+        if (_sendQueue.length > 0) {
+          var response_message = _sendQueue.removeAt(0);
+          _endpoint.write(response_message.buffer);
+          if (!_endpoint.status.isOk) {
+            throw new Exception("message pipe write failed");
+          }
+        }
+        if ((_sendQueue.length == 0) && _handle.writeEnabled()) {
+          _handle.disableWriteEvents();
+        }
+      }
+      if (core.MojoHandleSignals.isNone(mojoSignal)) {
+        // The handle watcher will send MojoHandleSignals.NONE when the other
+        // endpoint of the pipe is closed.
+        _handle.close();
+      }
+    });
+  }
+
+  Message buildResponse(Type t, int name, Object response) {
+    var builder = new MessageBuilder(name, align(getEncodedSize(t)));
+    builder.encodeStruct(t, response);
+    return builder.finish();
+  }
+
+  Message buildResponseWithID(Type t, int name, int id, Object response) {
+    var builder = new MessageWithRequestIDBuilder(
+        name, align(getEncodedSize(t)), id);
+    builder.encodeStruct(t, response);
+    return builder.finish();
+  }
+}