Dart: Simplifies the handle watcher. Various cleanups and bugfixes.

mojo/public/dart/src/handle_watcher.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 core;
 
 class _MojoHandleWatcherNatives {
   static int sendControlData(
       int controlHandle, int mojoHandle, SendPort port, int data)
       native "MojoHandleWatcher_SendControlData";
@@ skipping 15 matching lines @@
 //
 // add(handle, port, signals) - Instructs the MojoHandleWatcher isolate to add
 //     'handle' to the set of handles it watches, and to notify the calling
 //     isolate only for the events specified by 'signals' using the send port
 //     'port'
 //
 // remove(handle) - Instructs the MojoHandleWatcher isolate to remove 'handle'
 //     from the set of handles it watches. This allows the application isolate
 //     to, e.g., pause the stream of events.
 //
-// toggleWrite(handle) - Modifies the set of signals that an application isolate
-//     wishes to be notified about. Whether the application isolate should be
-//     be notified about a handle ready for writing is made the opposite.
-//
 // close(handle) - Notifies the HandleWatcherIsolate that a handle it is
 //     watching should be removed from its set and closed.
 class MojoHandleWatcher {
   // Control commands.
   static const int ADD = 0;
   static const int REMOVE = 1;
-  static const int TOGGLE_WRITE = 2;
-  static const int CLOSE = 3;
-  static const int TIMER = 4;
-  static const int SHUTDOWN = 5;
+  static const int CLOSE = 2;
+  static const int TIMER = 3;
+  static const int SHUTDOWN = 4;
 
   static int _encodeCommand(int cmd, [int signals = 0]) =>
-      (cmd << 2) | (signals & MojoHandleSignals.READWRITE);
+      (cmd << 2) | (signals & MojoHandleSignals.kReadWrite);
   static int _decodeCommand(int cmd) => cmd >> 2;
 
   // The Mojo handle over which control messages are sent.
   int _controlHandle;
 
   // Whether the handle watcher should shut down.
   bool _shutdown;
 
   // The list of handles being watched.
   List<int> _handles;
@@ skipping 21 matching lines @@
       _handles = new List<int>(),
       _ports = new List<SendPort>(),
       _signals = new List<int>(),
       _handleIndices = new Map<int, int>(),
       _handleCount = 1,
       _tempHandle = new RawMojoHandle(RawMojoHandle.INVALID),
       _timerQueue = new TimerQueue() {
     // Setup control handle.
     _handles.add(_controlHandle);
     _ports.add(null);  // There is no port for the control handle.
-    _signals.add(MojoHandleSignals.READABLE);
+    _signals.add(MojoHandleSignals.kReadable);
     _handleIndices[_controlHandle] = 0;
   }
 
   static void _handleWatcherIsolate(int consumerHandle) {
     MojoHandleWatcher watcher = new MojoHandleWatcher(consumerHandle);
     while (!watcher._shutdown) {
       int deadline = watcher._processTimerDeadlines();
       int res = RawMojoHandle.waitMany(watcher._handles,
                                        watcher._signals,
                                        deadline);
       if (res == 0) {
         watcher._handleControlMessage();
       } else if (res > 0) {
         int handle = watcher._handles[res];
         // Route event.
         watcher._routeEvent(res);
         // Remove the handle from the list.
         watcher._removeHandle(handle);
       } else if (res != MojoResult.kDeadlineExceeded) {
+        var result = new MojoResult(res);
         // Some handle was closed, but not by us.
         // We have to go through the list and find it.
         watcher._pruneClosedHandles();
       }
     }
   }
 
   void _routeEvent(int idx) {
     int client_handle = _handles[idx];
-    int signals = _signals[idx];
+    var signals = new MojoHandleSignals(_signals[idx]);
     SendPort port = _ports[idx];
 
     _tempHandle.h = client_handle;
-    bool readyWrite =
-        MojoHandleSignals.isWritable(signals) && _tempHandle.readyWrite();
-    bool readyRead =
-        MojoHandleSignals.isReadable(signals) && _tempHandle.readyRead();
-    if (readyRead && readyWrite) {
-      port.send(MojoHandleSignals.READWRITE);
-    } else if (readyWrite) {
-      port.send(MojoHandleSignals.WRITABLE);
-    } else if (readyRead) {
-      port.send(MojoHandleSignals.READABLE);
-    }
+    bool readyWrite = signals.isWritable && _tempHandle.readyWrite;
+    bool readyRead = signals.isReadable && _tempHandle.readyRead;
     _tempHandle.h = RawMojoHandle.INVALID;
+
+    var event = MojoHandleSignals.NONE;
+    event += readyRead ? MojoHandleSignals.READABLE : MojoHandleSignals.NONE;
+    event += readyWrite ? MojoHandleSignals.WRITABLE : MojoHandleSignals.NONE;
+    port.send([signals.value, event.value]);
   }
 
   void _handleControlMessage() {
     List result = _MojoHandleWatcherNatives.recvControlData(_controlHandle);
     // result[0] = mojo handle if any, or a timer deadline in milliseconds.
     // result[1] = SendPort if any.
     // result[2] = command << 2 | WRITABLE | READABLE
 
-    int signals = result[2] & MojoHandleSignals.READWRITE;
+    var signals = new MojoHandleSignals(
+        result[2] & MojoHandleSignals.kReadWrite);
     int command = _decodeCommand(result[2]);
     switch (command) {
       case ADD:
         _addHandle(result[0], result[1], signals);
         break;
       case REMOVE:
         _removeHandle(result[0]);
         break;
-      case TOGGLE_WRITE:
-        _toggleWrite(result[0]);
-        break;
       case CLOSE:
         _close(result[0]);
         break;
       case TIMER:
         _timer(result[1], result[0]);
         break;
       case SHUTDOWN:
-        _shutdownHandleWatcher();
+        _shutdownHandleWatcher(result[1]);
         break;
       default:
-        throw new Exception("Invalid Command: $command");
+        throw "Invalid Command: $command";
         break;
     }
   }
 
-  void _addHandle(int mojoHandle, SendPort port, int signals) {
-    _handles.add(mojoHandle);
-    _ports.add(port);
-    _signals.add(signals & MojoHandleSignals.READWRITE);
-    _handleIndices[mojoHandle] = _handleCount;
-    _handleCount++;
+  void _addHandle(int mojoHandle, SendPort port, MojoHandleSignals signals) {
+    int idx = _handleIndices[mojoHandle];
+    if (idx == null) {
+      _handles.add(mojoHandle);
+      _ports.add(port);
+      _signals.add(signals.value);
+      _handleIndices[mojoHandle] = _handleCount;
+      _handleCount++;
+    } else {
+      assert(_ports[idx] == port);
+      assert(_handles[idx] == mojoHandle);
+      _signals[idx] |= signals.value;
+    }
   }
 
   void _removeHandle(int mojoHandle) {
     int idx = _handleIndices[mojoHandle];
     if (idx == null) {
-      throw new Exception("Remove on a non-existent handle: idx = $idx.");
+      throw "Remove on a non-existent handle: idx = $idx.";
     }
     if (idx == 0) {
-      throw new Exception("The control handle (idx = 0) cannot be removed.");
+      throw "The control handle (idx = 0) cannot be removed.";
     }
     // We don't use List.removeAt so that we know how to fix-up _handleIndices.
     if (idx == _handleCount - 1) {
       int handle = _handles[idx];
       _handleIndices[handle] = null;
       _handles.removeLast();
       _signals.removeLast();
       _ports.removeLast();
       _handleCount--;
     } else {
       int last = _handleCount - 1;
+      _handleIndices[_handles[idx]] = null;
       _handles[idx] = _handles[last];
       _signals[idx] = _signals[last];
       _ports[idx] = _ports[last];
       _handles.removeLast();
       _signals.removeLast();
       _ports.removeLast();
       _handleIndices[_handles[idx]] = idx;
       _handleCount--;
     }
   }
 
   void _close(int mojoHandle, {bool pruning : false}) {
     int idx = _handleIndices[mojoHandle];
     if (idx == null) {
-      throw new Exception("Close on a non-existent handle: idx = $idx.");
+      // A client may request to close a handle that has already been closed on
+      // the other side and pruned, but before receiving notification from the
+      // handle watcher.
+      return;
     }
     if (idx == 0) {
-      throw new Exception("The control handle (idx = 0) cannot be closed.");
+      throw "The control handle (idx = 0) cannot be closed.";
     }
     _tempHandle.h = _handles[idx];
     _tempHandle.close();
     _tempHandle.h = RawMojoHandle.INVALID;
     if (pruning) {
       // If this handle is being pruned, notify the application isolate
-      // by sending MojoHandleSignals.NONE.
-      _ports[idx].send(MojoHandleSignals.NONE);
+      // by sending MojoHandleSignals.PEER_CLOSED.
+      _ports[idx].send([_signals[idx], MojoHandleSignals.kPeerClosed]);
     }
     _removeHandle(mojoHandle);
   }
 
   // Returns the next timer deadline in units of microseconds from 'now'.
   int _processTimerDeadlines() {
     int now = (new DateTime.now()).millisecondsSinceEpoch;
     while (_timerQueue.hasTimer && (now >= _timerQueue.currentTimeout)) {
       _timerQueue.currentPort.send(null);
       _timerQueue.removeCurrent();
       now = (new DateTime.now()).millisecondsSinceEpoch;
     }
     return _timerQueue.hasTimer ? (_timerQueue.currentTimeout - now) * 1000
                                 : RawMojoHandle.DEADLINE_INDEFINITE;
   }
 
   void _timer(SendPort port, int deadline) {
     _timerQueue.updateTimer(port, deadline);
   }
 
-  void _toggleWrite(int mojoHandle) {
-    int idx = _handleIndices[mojoHandle];
-    if (idx == null) {
-      throw new Exception(
-          "Toggle write on a non-existent handle: $mojoHandle.");
-    }
-    if (idx == 0) {
-      throw new Exception("The control handle (idx = 0) cannot be toggled.");
-    }
-    _signals[idx] = MojoHandleSignals.toggleWrite(_signals[idx]);
-  }
-
   void _pruneClosedHandles() {
     List<int> closed = new List();
     for (var h in _handles) {
       _tempHandle.h = h;
-      MojoResult res = _tempHandle.wait(MojoHandleSignals.READWRITE, 0);
+      MojoResult res = _tempHandle.wait(MojoHandleSignals.kReadWrite, 0);
       if ((!res.isOk) && (!res.isDeadlineExceeded)) {
         closed.add(h);
       }
       _tempHandle.h = RawMojoHandle.INVALID;
     }
     for (var h in closed) {
       _close(h, pruning: true);
     }
   }
 
-  void _shutdownHandleWatcher() {
+  void _shutdownHandleWatcher(SendPort shutdownSendPort) {
     _shutdown = true;
     _tempHandle.h = _controlHandle;
     _tempHandle.close();
     _tempHandle.h = RawMojoHandle.INVALID;
+    shutdownSendPort.send(null);
   }
 
   static MojoResult _sendControlData(RawMojoHandle mojoHandle,
                                      SendPort port,
                                      int data) {
     int controlHandle = _MojoHandleWatcherNatives.getControlHandle();
     if (controlHandle == RawMojoHandle.INVALID) {
-      throw new Exception("Found invalid control handle");
+      return MojoResult.FAILED_PRECONDITION;
     }
 
     int rawHandle = RawMojoHandle.INVALID;
     if (mojoHandle != null) {
       rawHandle = mojoHandle.h;
     }
     var result = _MojoHandleWatcherNatives.sendControlData(
         controlHandle, rawHandle, port, data);
     return new MojoResult(result);
   }
 
   static Future<Isolate> Start() {
     // Make a control message pipe,
     MojoMessagePipe pipe = new MojoMessagePipe();
     int consumerHandle = pipe.endpoints[0].handle.h;
     int producerHandle = pipe.endpoints[1].handle.h;
 
     // Call setControlHandle with the other end.
+    assert(producerHandle != RawMojoHandle.INVALID);
     _MojoHandleWatcherNatives.setControlHandle(producerHandle);
 
     // Spawn the handle watcher isolate with the MojoHandleWatcher,
     return Isolate.spawn(_handleWatcherIsolate, consumerHandle);
   }
 
   static void Stop() {
+    // Create a port for notification that the handle watcher has shutdown.
+    var shutdownReceivePort = new ReceivePort();
+    var shutdownSendPort = shutdownReceivePort.sendPort;
+
     // Send the shutdown command.
-    _sendControlData(null, null, _encodeCommand(SHUTDOWN));
+    _sendControlData(null, shutdownSendPort, _encodeCommand(SHUTDOWN));
 
     // Close the control handle.
     int controlHandle = _MojoHandleWatcherNatives.getControlHandle();
     var handle = new RawMojoHandle(controlHandle);
     handle.close();
 
     // Invalidate the control handle.
     _MojoHandleWatcherNatives.setControlHandle(RawMojoHandle.INVALID);
+
+    // Wait for the handle watcher isolate to exit.
+    shutdownReceivePort.first.then((_) {
+      shutdownReceivePort.close();
+    });
   }
 
   static MojoResult close(RawMojoHandle mojoHandle) {
     return _sendControlData(mojoHandle, null, _encodeCommand(CLOSE));
   }
 
-  static MojoResult toggleWrite(RawMojoHandle mojoHandle) {
-    return _sendControlData(mojoHandle, null, _encodeCommand(TOGGLE_WRITE));
-  }
-
   static MojoResult add(RawMojoHandle mojoHandle, SendPort port, int signals) {
     return _sendControlData(mojoHandle, port, _encodeCommand(ADD, signals));
   }
 
   static MojoResult remove(RawMojoHandle mojoHandle) {
     return _sendControlData(mojoHandle, null, _encodeCommand(REMOVE));
   }
 
   static MojoResult timer(SendPort port, int deadline) {
     // The deadline will be unwrapped before sending to the handle watcher.
     return _sendControlData(
         new RawMojoHandle(deadline), port, _encodeCommand(TIMER));
   }
 }