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

mojo/public/dart/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 _sendQueue;
-  List _completerQueue;
+  Map<int, Completer> _completerMap;
   bool _isOpen = false;
+  int _nextId = 0;
 
   void handleResponse(MessageReader reader);
 
-  Client(this._endpoint) {
+  Client(core.MojoMessagePipeEndpoint endpoint) :
+      _sendQueue = [],
+      _completerMap = {},
+      _endpoint = endpoint,
+      _handle = new core.MojoHandle(endpoint.handle);
+
+  Client.fromHandle(int handle) {
     _sendQueue = [];
-    _completerQueue = [];
+    _completerMap = {};
+    _endpoint =
+        new core.MojoMessagePipeEndpoint(new core.RawMojoHandle(handle));
     _handle = new core.MojoHandle(_endpoint.handle);
   }
 
+  void _doRead() {
+    // 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
+      // handle watcher.
+      throw "message pipe query failed: ${result.status}";
+    }
+
+    // Read the data.
+    var bytes = new ByteData(result.bytesRead);
+    var handles = new List<core.RawMojoHandle>(result.handlesRead);
+    result = _endpoint.read(bytes, result.bytesRead, handles);
+    if (!result.status.isOk && !result.status.isResourceExhausted) {
+      throw "message pipe read failed: ${result.status}";
+    }
+    var message = new Message(bytes, handles);
+    var reader = new MessageReader(message);
+
+    handleResponse(reader);
+  }
+
+  void _doWrite() {
+    if (_sendQueue.length > 0) {
+      List messageCompleter = _sendQueue.removeAt(0);
+      Message message = messageCompleter[0];
+      Completer completer = messageCompleter[1];
+      _endpoint.write(message.buffer,
+                      message.buffer.lengthInBytes,
+                      message.handles);
+      if (!_endpoint.status.isOk) {
+        throw "message pipe write failed";
+      }
+      if (completer != null) {
+        if (!message.expectsResponse) {
+          throw "Message has a completer, but does not expect a response";
+        }
+        int requestID = message.requestID;
+        if (_completerMap[requestID] != null) {
+          throw "Request ID $requestID is already in use.";
+        }
+        _completerMap[requestID] = completer;
+      }
+    }
+  }
+
   void open() {
-    _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
-          // handle watcher.
-          throw new Exception("message pipe query failed: ${result.status}");
-        }
+    _handle.listen((List<int> event) {
+      var signalsWatched = new core.MojoHandleSignals(event[0]);
+      var signalsReceived = new core.MojoHandleSignals(event[1]);
+      if (signalsReceived.isPeerClosed) {
+        close();
+        return;
+      }
 
-        // Read the data.
-        var bytes = new ByteData(result.bytesRead);
-        var handles = new List<core.RawMojoHandle>(result.handlesRead);
-        result = _endpoint.read(bytes, result.bytesRead, handles);
-        if (!result.status.isOk && !result.status.isResourceExhausted) {
-          throw new Exception("message pipe read failed: ${result.status}");
-        }
-        var message = new Message(bytes, handles);
-        var reader = new MessageReader(message);
+      if (signalsReceived.isReadable) {
+        _doRead();
+      }
 
-        handleResponse(reader);
+      if (signalsReceived.isWritable) {
+        _doWrite();
       }
-      if (core.MojoHandleSignals.isWritable(mojoSignal)) {
-        if (_sendQueue.length > 0) {
-          List messageCompleter = _sendQueue.removeAt(0);
-          _endpoint.write(messageCompleter[0].buffer,
-                          messageCompleter[0].buffer.lengthInBytes,
-                          messageCompleter[0].handles);
-          if (!_endpoint.status.isOk) {
-            throw new Exception("message pipe write failed");
-          }
-          if (messageCompleter[1] != null) {
-            _completerQueue.add(messageCompleter[1]);
-          }
-        }
-        if ((_sendQueue.length == 0) && _handle.writeEnabled()) {
-          _handle.disableWriteEvents();
-        }
-      }
-      if (core.MojoHandleSignals.isNone(mojoSignal)) {
-        // The handle watcher will send MojoHandleSignals.NONE if the other
-        // endpoint of the pipe is closed.
-        _handle.close();
+
+      if (_sendQueue.length == 0) {
+        var withoutWritable = signalsWatched - core.MojoHandleSignals.WRITABLE;
+        _handle.enableSignals(withoutWritable);
+      } else {
+        _handle.enableSignals(signalsWatched);
       }
     });
     _isOpen = true;
   }
 
   void close() {
-    assert(isOpen);
-    _handle.close();
-    _isOpen = false;
+    if (_isOpen) {
+      _handle.close();
+      _handle = null;
+      _isOpen = false;
+    }
   }
 
   void enqueueMessage(Type t, int name, Object msg) {
     var builder = new MessageBuilder(name, align(getEncodedSize(t)));
     builder.encodeStruct(t, msg);
     var message = builder.finish();
     _sendQueue.add([message, null]);
-    if (!_handle.writeEnabled()) {
-      _handle.enableWriteEvents();
+    if (_sendQueue.length == 1) {
+      _handle.enableAllEvents();
     }
   }
 
+  int _getNextId() {
+    int next = _nextId;
+    _nextId++;
+    if (_nextId.bitLength > 64) {

[siva, 2014/12/29 23:20:44]

maybe document what this magic number 64 is.

[zra, 2014/12/30 16:29:33]

Added a comment.

+      _nextId = 1;
+    }
+    return next;
+  }
+
   Future enqueueMessageWithRequestID(
       Type t, int name, int id, int flags, Object msg) {
+    if (id == -1) {
+      id = _getNextId();
+    }
+
     var builder = new MessageWithRequestIDBuilder(
         name, align(getEncodedSize(t)), id, flags);
     builder.encodeStruct(t, msg);
     var message = builder.finish();
 
     var completer = new Completer();
     _sendQueue.add([message, completer]);
-    if (!_handle.writeEnabled()) {
-      _handle.enableWriteEvents();
+    if (_sendQueue.length == 1) {
+      _handle.enableAllEvents();
+    } else {
+      _handle.enableReadEvents();
     }
     return completer.future;
   }
 
   // Need a getter for this for access in subclasses.
-  List get completerQueue => _completerQueue;
+  Map<int, Completer> get completerMap => _completerMap;
   bool get isOpen => _isOpen;
 }