Initial work on Dart bindings for Mojo.

mojo/public/dart/system/lib/src/handle.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 _MojoHandleNatives {
+  static int close(int handle) native "MojoHandle_Close";
+  static int wait(int handle, int signals, int deadline)
+      native "MojoHandle_Wait";
+  static int waitMany(
+      List handles, List signals, int num_handles, int deadline)
+      native "MojoHandle_WaitMany";
+}
+
+
+class RawMojoHandle {
+  static final int INVALID = 0;
+  static final int DEADLINE_INDEFINITE = -1;
+
+  RawMojoHandle(this.h);
+
+  int close() {
+    int result = _MojoHandleNatives.close(h);
+    h = INVALID;
+    return result;
+  }
+
+  int wait(int signals, int deadline) {
+    return _MojoHandleNatives.wait(h, signals, deadline);
+  }
+
+  bool _ready(int signal) {
+    int res = wait(signal, 0);
+    switch (res) {
+      case MojoResult.OK:
+        return true;
+      case MojoResult.DEADLINE_EXCEEDED:
+      case MojoResult.CANCELLED:
+      case MojoResult.INVALID_ARGUMENT:
+      case MojoResult.FAILED_PRECONDITION:
+        return false;
+      default:
+        // Should be unreachable.
+        throw new Exception("Unreachable");
+    }
+  }
+
+  bool readyRead() => _ready(MojoHandleSignals.READABLE);
+  bool readyWrite() => _ready(MojoHandleSignals.WRITABLE);
+
+  static int waitMany(
+      List<int> handles, List signals, int deadline) {
+    if (handles.length != signals.length) {
+      return MojoResult.INVALID_ARGUMENT;
+    }
+    return _MojoHandleNatives.waitMany(
+        handles, signals, handles.length, deadline);
+  }
+
+  static bool isValid(RawMojoHandle h) => (h.h != INVALID);
+
+  int h;
+}
+
+
+class MojoHandle extends Stream<int> {
+  RawMojoHandle _handle;
+  StreamController _controller;
+  SendPort _send_port;
+  int _signals;
+  bool _eventHandlerAdded;
+
+  MojoHandle(this._handle) : 
+      _signals = MojoHandleSignals.READABLE,
+      _eventHandlerAdded = false {
+    ReceivePort rp = new ReceivePort();
+    _send_port = rp.sendPort;
+    _controller = new StreamController(sync: true,
+        onListen: _onSubscriptionStateChange,
+        onCancel: _onSubscriptionStateChange,
+        onPause: _onPauseStateChange,
+        onResume: _onPauseStateChange);
+    _controller.addStream(rp);
+  }
+
+  void close() {
+    MojoHandleWatcher.close(_handle.h);
+    _controller.close();
+  }
+
+  _onDataClosure(origOnData) {
+    return ((int event) {
+      // The event handler removes this handle.
+      _eventHandlerAdded = false;
+      origOnData(event);
+      int res = MojoHandleWatcher.add(_handle.h, _send_port, _signals);
+      _eventHandlerAdded = true;
+      if (res != MojoResult.OK) {
+        throw new Exception("Failed to re-add handle: ${_handle.h}");
+      }
+    });
+  }
+
+  StreamSubscription<int> listen(
+      void onData(int event),
+      {Function onError, void onDone(), bool cancelOnError}) {
+
+    int res = MojoHandleWatcher.add(_handle.h, _send_port, _signals);
+    _eventHandlerAdded = true;
+    if (res != MojoResult.OK) {
+      throw new Exception("MojoHandleWatcher add failed: $res");
+    }
+
+    return _controller.stream.listen(
+        _onDataClosure(onData),
+        onError: onError,
+        onDone: onDone,
+        cancelOnError: cancelOnError);
+  }
+
+  bool writeEnabled() => MojoHandleSignals.isWritable(_signals);
+
+  void toggleWriteEvents() {
+    //print("handle: ${_handle.h} toggle write");
+    _signals = MojoHandleSignals.toggleWrite(_signals);
+    if (_eventHandlerAdded) {
+      int res = MojoHandleWatcher.toggleWrite(_handle.h);
+      if (res != MojoResult.OK) {
+        throw new Exception("MojoHandleWatcher failed to toggle write: $res");
+      }
+    }
+  }
+
+  void _onSubscriptionStateChange() {
+    if (!_controller.hasListener) {
+      close();
+    }
+  }
+
+  void _onPauseStateChange() {
+    if (_controller.isPaused) {
+      MojoHandleWatcher.remove(_handle.h);
+      _eventHandlerAdded = false;
+    } else {
+      int res = MojoHandleWatcher.add(_handle.h, _send_port, _signals);
+      if (res != MojoResult.OK) {
+        throw new Exception("MojoHandleWatcher add failed: $res");
+      }
+      _eventHandlerAdded = true;
+    }
+  }
+}