Dart: Use a RawReceivePort to receive events for Mojo handles.

mojo/public/dart/mojo/lib/src/event_stream.dart

Index: mojo/public/dart/mojo/lib/src/event_stream.dart
diff --git a/mojo/public/dart/mojo/lib/src/event_stream.dart b/mojo/public/dart/mojo/lib/src/event_stream.dart
index 0ff091ee571c34f31e256879970b417ce9fa797d..5b816fa05603f4279fce54cd3e93cd626e9996a9 100644
--- a/mojo/public/dart/mojo/lib/src/event_stream.dart
+++ b/mojo/public/dart/mojo/lib/src/event_stream.dart
@@ -4,33 +4,29 @@
 
 part of core;
 
-class MojoEventStream extends Stream<List<int>> {
+class MojoEventSubscription {

[Cutch, 2015/11/11 19:08:16]

Consider 'MojoHandleEventSubscription'

[zra, 2015/11/11 20:43:26]

Since Handles are the only source of events, and since
MojoHandleEventSubscription is a bit verbose, I'd like to stick with
MojoEventSubscription.

   // The underlying Mojo handle.
   MojoHandle _handle;
 
-  // Providing our own stream controller allows us to take custom actions when
-  // listeners pause/resume/etc. their StreamSubscription.
-  StreamController _controller;
-
   // The send port that we give to the handle watcher to notify us of handle
   // events.
   SendPort _sendPort;
 
   // The receive port on which we listen and receive events from the handle
   // watcher.
-  ReceivePort _receivePort;
+  RawReceivePort _receivePort;
 
   // The signals on this handle that we're interested in.
   MojoHandleSignals _signals;
 
   // Whether listen has been called.

[Cutch, 2015/11/11 19:08:15]

s/listen/subscribe

[zra, 2015/11/11 20:43:26]

Done.

-  bool _isListening;
+  bool _isSubscribed;
 
-  MojoEventStream(MojoHandle handle,
+  MojoEventSubscription(MojoHandle handle,
       [MojoHandleSignals signals = MojoHandleSignals.PEER_CLOSED_READABLE])
       : _handle = handle,
         _signals = signals,
-        _isListening = false {
+        _isSubscribed = false {
     MojoResult result = MojoHandle.registerFinalizer(this);
     if (!result.isOk) {
       throw new MojoInternalError(
@@ -40,35 +36,26 @@ class MojoEventStream extends Stream<List<int>> {
 
   Future close({bool immediate: false}) => _close(immediate: immediate);
 
-  StreamSubscription<List<int>> listen(void onData(List event),
-      {Function onError, void onDone(), bool cancelOnError}) {
-    if (_isListening) {
-      throw new MojoApiError("Listen has already been called: $_handle.");
+  void subscribe(void handler(List<int> event)) {
+    if (_isSubscribed) {
+      throw new MojoApiError("subscribe() has already been called: $this.");
     }
-    _receivePort = new ReceivePort();
+    _receivePort = new RawReceivePort(handler);
     _sendPort = _receivePort.sendPort;
-    _controller = new StreamController(
-        sync: true,
-        onPause: _onPauseStateChange,
-        onResume: _onPauseStateChange);
-    _controller.addStream(_receivePort).whenComplete(_controller.close);
 
     if (_signals != MojoHandleSignals.NONE) {
-      var res = new MojoResult(
-          MojoHandleWatcher.add(_handle.h, _sendPort, _signals.value));
-      if (!res.isOk) {
+      int res = MojoHandleWatcher.add(_handle.h, _sendPort, _signals.value);
+      if (res != MojoResult.kOk) {
         throw new MojoInternalError("MojoHandleWatcher add failed: $res");
       }
     }
 
-    _isListening = true;
-    return _controller.stream.listen(onData,
-        onError: onError, onDone: onDone, cancelOnError: cancelOnError);
+    _isSubscribed = true;
   }
 
   bool enableSignals(MojoHandleSignals signals) {
     _signals = signals;
-    if (_isListening) {
+    if (_isSubscribed) {
       return MojoHandleWatcher.add(_handle.h, _sendPort, signals.value) ==
           MojoResult.kOk;
     }
@@ -82,7 +69,7 @@ class MojoEventStream extends Stream<List<int>> {
 
   Future _close({bool immediate: false, bool local: false}) {
     if (_handle != null) {
-      if (_isListening && !local) {
+      if (_isSubscribed && !local) {
         return _handleWatcherClose(immediate: immediate).then((result) {
           // If the handle watcher is gone, then close the handle ourselves.
           if (!result.isOk) {
@@ -117,59 +104,44 @@ class MojoEventStream extends Stream<List<int>> {
     }
   }
 
-  void _onPauseStateChange() {
-    if (_controller.isPaused) {
-      var res = new MojoResult(MojoHandleWatcher.remove(_handle.h));
-      if (!res.isOk) {
-        throw new MojoInternalError("MojoHandleWatcher add failed: $res");
-      }
-    } else {
-      var res = new MojoResult(
-          MojoHandleWatcher.add(_handle.h, _sendPort, _signals.value));
-      if (!res.isOk) {
-        throw new MojoInternalError("MojoHandleWatcher add failed: $res");
-      }
-    }
-  }
-
   bool get readyRead => _handle.readyRead;
   bool get readyWrite => _handle.readyWrite;
+  MojoHandleSignals get signals => _signals;
 
   String toString() => "$_handle";
 }
 
-typedef void ErrorHandler();
+typedef void ErrorHandler(Object e);
 
-class MojoEventStreamListener {
-  StreamSubscription subscription;
+class MojoEventHandler {

[Cutch, 2015/11/11 19:08:16]

Consider 'MojoHandleEventHandler'

[zra, 2015/11/11 20:43:26]

Like above, my feeling is that this is too verbose.

   ErrorHandler onError;
 
   MojoMessagePipeEndpoint _endpoint;
-  MojoEventStream _eventStream;
+  MojoEventSubscription _eventSubscription;
   bool _isOpen = false;
   bool _isInHandler = false;
   bool _isPeerClosed = false;
 
-  MojoEventStreamListener.fromEndpoint(MojoMessagePipeEndpoint endpoint)
+  MojoEventHandler.fromEndpoint(MojoMessagePipeEndpoint endpoint)
       : _endpoint = endpoint,
-        _eventStream = new MojoEventStream(endpoint.handle) {
-    listen();
+        _eventSubscription = new MojoEventSubscription(endpoint.handle) {
+    handleEvents();
   }
 
-  MojoEventStreamListener.fromHandle(MojoHandle handle) {
+  MojoEventHandler.fromHandle(MojoHandle handle) {
     _endpoint = new MojoMessagePipeEndpoint(handle);
-    _eventStream = new MojoEventStream(handle);
-    listen();
+    _eventSubscription = new MojoEventSubscription(handle);
+    handleEvents();
   }
 
-  MojoEventStreamListener.unbound();
+  MojoEventHandler.unbound();
 
   void bind(MojoMessagePipeEndpoint endpoint) {
     if (isBound) {
       throw new MojoApiError("MojoEventStreamListener is already bound.");
     }
     _endpoint = endpoint;
-    _eventStream = new MojoEventStream(endpoint.handle);
+    _eventSubscription = new MojoEventSubscription(endpoint.handle);
     _isOpen = false;
     _isInHandler = false;
     _isPeerClosed = false;
@@ -180,67 +152,74 @@ class MojoEventStreamListener {
       throw new MojoApiError("MojoEventStreamListener is already bound.");
     }
     _endpoint = new MojoMessagePipeEndpoint(handle);
-    _eventStream = new MojoEventStream(handle);
+    _eventSubscription = new MojoEventSubscription(handle);
     _isOpen = false;
     _isInHandler = false;
     _isPeerClosed = false;
   }
 
-  StreamSubscription<List<int>> listen() {
+  void handleEvents() {

[Cutch, 2015/11/11 19:08:16]

handleEvents -> beginHandlingEvents()

[zra, 2015/11/11 20:43:26]

Done.

     if (!isBound) {
       throw new MojoApiError("MojoEventStreamListener is unbound.");
     }
-    if (subscription != null) {
-      throw new MojoApiError("Listen has already been called.");
-    }
     _isOpen = true;
-    subscription = _eventStream.listen((List<int> event) {
-      if (!_isOpen) {
-        // The actual close of the underlying stream happens asynchronously
-        // after the call to close. However, we start to ignore incoming events
-        // immediately.
-        return;
-      }
-      var signalsWatched = new MojoHandleSignals(event[0]);
-      var signalsReceived = new MojoHandleSignals(event[1]);
-      _isInHandler = true;
-      if (signalsReceived.isReadable) {
-        assert(_eventStream.readyRead);
-        handleRead();
-      }
-      if (signalsReceived.isWritable) {
-        assert(_eventStream.readyWrite);
-        handleWrite();
-      }
-      _isPeerClosed = signalsReceived.isPeerClosed ||
-          !_eventStream.enableSignals(signalsWatched);
-      _isInHandler = false;
-      if (_isPeerClosed) {
-        close().then((_) {
+    _eventSubscription.subscribe((List<int> event) {
+      try {
+        _handleEvent(event);
+      } catch (e) {
+        close(immediate: true).then((_) {
           if (onError != null) {
-            onError();
+            onError(e);
           }
         });
       }
-    }, onDone: close);
-    return subscription;
+    });
   }
 
   Future close({bool immediate: false}) {
     var result;
     _isOpen = false;
     _endpoint = null;
-    subscription = null;
-    if (_eventStream != null) {
-      result = _eventStream
+    if (_eventSubscription != null) {
+      result = _eventSubscription
           ._close(immediate: immediate, local: _isPeerClosed)
           .then((_) {
-        _eventStream = null;
+        _eventSubscription = null;
       });
     }
     return result != null ? result : new Future.value(null);
   }
 
+  void _handleEvent(List<int> event) {
+    if (!_isOpen) {
+      // The actual close of the underlying stream happens asynchronously
+      // after the call to close. However, we start to ignore incoming events
+      // immediately.
+      return;
+    }
+    var signalsWatched = new MojoHandleSignals(event[0]);
+    var signalsReceived = new MojoHandleSignals(event[1]);
+    _isInHandler = true;
+    if (signalsReceived.isReadable) {
+      assert(_eventSubscription.readyRead);
+      handleRead();
+    }
+    if (signalsReceived.isWritable) {
+      assert(_eventSubscription.readyWrite);
+      handleWrite();
+    }
+    _isPeerClosed = signalsReceived.isPeerClosed ||
+        !_eventSubscription.enableSignals(signalsWatched);
+    _isInHandler = false;
+    if (_isPeerClosed) {
+      close().then((_) {
+        if (onError != null) {
+          onError(null);
+        }
+      });
+    }
+  }
+
   void handleRead() {}
   void handleWrite() {}
 
@@ -250,6 +229,6 @@ class MojoEventStreamListener {
   bool get isBound => _endpoint != null;
   bool get isPeerClosed => _isPeerClosed;
 
-  String toString() => "MojoEventStreamListener("
+  String toString() => "MojoEventHandler("
       "isOpen: $isOpen, isBound: $isBound, endpoint: $_endpoint)";
 }