Initial work on Dart bindings for Mojo.

mojo/public/dart/system/lib/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 control_handle, int mojo_handle, SendPort port, int data)
+      native "MojoHandleWatcher_SendControlData";
+  static List recvControlData(int control_handle)
+      native "MojoHandleWatcher_RecvControlData";
+  static int setControlHandle(int control_handle)
+      native "MojoHandleWatcher_SetControlHandle";
+  static int getControlHandle()
+      native "MojoHandleWatcher_GetControlHandle";
+}
+
+
+class MojoHandleWatcher {
+  static const int ADD = 0;
+  static const int REMOVE = 1;
+  static const int TOGGLE_WRITE = 2;
+  static const int CLOSE = 3;
+  static const int SHUTDOWN = 4;
+
+  RawMojoHandle _dummy_handle;
+  int _control_handle;
+  bool _shutdown;
+  List<int> _handles;
+  List<SendPort> _ports;
+  List<int> _signals;
+  int _handle_count;
+  Map<int, int> _handle_indices;
+
+  MojoHandleWatcher(this._control_handle) :
+      _shutdown = false,
+      _ports = [null],
+      _signals = [MojoHandleSignals.READABLE],
+      _handle_count = 1 {
+    _handles = [_control_handle];
+    _handle_indices = new Map();
+    _handle_indices[_control_handle] = 0;
+    _dummy_handle = new RawMojoHandle(RawMojoHandle.INVALID);
+  }
+
+  static void _handleWatcherIsolate(MojoHandleWatcher eh) {
+    while (!eh._shutdown) {
+      int res = RawMojoHandle.waitMany(eh._handles,
+                                       eh._signals,
+                                       RawMojoHandle.DEADLINE_INDEFINITE);
+      if (res == 0) {
+        eh._handleControlMessage();
+      } else if (res > 0) {
+        int handle = eh._handles[res];
+        // Route event.
+        eh._routeEvent(res);
+        // Remove the handle from the list.
+        eh._removeHandle(handle);
+      } else if (res == MojoResult.FAILED_PRECONDITION) {
+        // None of the handles can ever be satisfied, including the control
+        // handle. This probably means we are going down. Clean up and
+        // shutdown.
+        eh._pruneClosedHandles();
+        eh._shutdown = true;
+      } else {
+        // Some handle is closed. We have to go through the list and find it.
+        eh._pruneClosedHandles();
+      }
+    }
+  }
+
+  void _routeEvent(int idx) {
+    int client_handle = _handles[idx];
+    int signals = _signals[idx];
+    SendPort port = _ports[idx];
+
+    _dummy_handle.h = client_handle;
+    bool readyWrite =
+        MojoHandleSignals.isWritable(signals) && _dummy_handle.readyWrite();
+    bool readyRead =
+        MojoHandleSignals.isReadable(signals) && _dummy_handle.readyRead();
+    if (readyRead && readyWrite) {
+      //print("routing READWRITE for handle $client_handle");
+      port.send(MojoHandleSignals.READWRITE);
+    } else if (readyWrite) {
+      //print("routing WRITABLE for handle $client_handle");
+      port.send(MojoHandleSignals.WRITABLE);
+    } else if (readyRead) {
+      //print("routing READABLE for handle $client_handle");
+      port.send(MojoHandleSignals.READABLE);
+    }
+    _dummy_handle.h = RawMojoHandle.INVALID;
+  }
+
+  void _handleControlMessage() {
+    List result = _MojoHandleWatcherNatives.recvControlData(_control_handle);
+    // result[0] = mojo handle if any
+    // result[1] = SendPort if any
+    // result[2] = command << 2 | WRITABLE | READABLE
+
+    int signals = result[2] & MojoHandleSignals.READWRITE;
+    switch (result[2] >> 2) {
+      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 SHUTDOWN:
+        _shutdown = true;
+        break;
+      default:
+        break;
+    }
+  }
+
+  void _addHandle(int mojo_handle, SendPort port, int signals) {
+    _handles.add(mojo_handle);
+    _ports.add(port);
+    _signals.add(signals & MojoHandleSignals.READWRITE);
+    _handle_indices[mojo_handle] = _handle_count;
+    _handle_count++;
+  }
+
+  void _removeHandle(int mojo_handle) {
+    int idx = _handle_indices[mojo_handle];
+    if (idx == null) {
+      return;
+    }
+    if (idx == 0) {
+      // Cannot remove control handle.
+      return;
+    }
+    if (idx == _handle_count - 1) {
+      int handle = _handles[idx];
+      _handle_indices[handle] = null;
+      _handles.removeLast();
+      _signals.removeLast();
+      _ports.removeLast();
+      _handle_count--;
+    } else {
+      int last = _handle_count - 1;
+      _handles[idx] = _handles[last];
+      _signals[idx] = _signals[last];
+      _ports[idx] = _ports[last];
+      _handles.removeLast();
+      _signals.removeLast();
+      _ports.removeLast();
+      _handle_indices[_handles[idx]] = idx;
+      _handle_count--;
+    }
+  }
+
+  void _close(int mojo_handle) {
+    int idx = _handle_indices[mojo_handle];
+    if (idx == null) {
+      return;
+    }
+    if (idx == 0) {
+      // Cannot remove control handle.
+      return;
+    }
+    _dummy_handle.h = _handles[idx];
+    _dummy_handle.close();
+    _dummy_handle.h = RawMojoHandle.INVALID;
+    _removeHandle(mojo_handle);
+  }
+
+  void _toggleWrite(int mojo_handle) {
+    int idx = _handle_indices[mojo_handle];
+    if (idx == null) {
+      return;
+    }
+    if (idx == 0) {
+      // Cannot toggle the control handle.
+      return;
+    }
+    _signals[idx] = MojoHandleSignals.toggleWrite(_signals[idx]);
+  }
+
+  void _pruneClosedHandles() {
+    List<int> closed = new List();
+    for (var h in _handles) {
+      int res = 0;
+      _dummy_handle.h = h;
+      res = _dummy_handle.wait(MojoHandleSignals.READWRITE, 0);
+      if ((res != MojoResult.OK) && (res != MojoResult.DEADLINE_EXCEEDED)) {
+        closed.add(h);
+      }
+      _dummy_handle.h = RawMojoHandle.INVALID;
+    }
+
+    for (var h in closed) {
+      _close(h);
+    }
+  }
+
+  static Future<bool> Start() {
+    // 1. make control message pipe,
+    // 2. make MojoHandleWatcher with one end,
+    // 3. setControlHandle with the other end.
+    // 4. spawn isolate with MojoHandleWatcher,
+    // 5. return Future<bool> giving true on success.
+    MojoMessagePipe pipe = new MojoMessagePipe();
+    int consumer_handle = pipe.endpoints[0].handle.h;
+    int producer_handle = pipe.endpoints[1].handle.h;
+    MojoHandleWatcher eh = new MojoHandleWatcher(consumer_handle);
+    _MojoHandleWatcherNatives.setControlHandle(producer_handle);
+    return Isolate.spawn(_handleWatcherIsolate, eh).then((isolate) {
+      return true;
+    });
+  }
+
+  static void Stop() {
+    sendControlData(RawMojoHandle.INVALID, null, SHUTDOWN << 2);
+  }
+
+  static int sendControlData(int mojo_handle, SendPort port, int data) {
+    int control_handle = _MojoHandleWatcherNatives.getControlHandle();
+    if (control_handle == RawMojoHandle.INVALID) {
+      throw new Exception("Found invalid control handle");
+    }
+    return _MojoHandleWatcherNatives.sendControlData(
+        control_handle, mojo_handle, port, data);
+  }
+
+  static int close(int mojo_handle) {
+    return sendControlData(mojo_handle, null, CLOSE << 2);
+  }
+
+  static int toggleWrite(int mojo_handle) {
+    return sendControlData(mojo_handle, null, TOGGLE_WRITE << 2);
+  }
+
+  static int add(int mojo_handle, SendPort port, int signals) {
+    return sendControlData(
+        mojo_handle,
+        port,
+        (ADD << 2) | (signals & MojoHandleSignals.READWRITE));
+  }
+}