sdk/lib/html/src/Isolates.dart

// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

_serialize(var message) {
  return new _JsSerializer().traverse(message);
}

class _JsSerializer extends _Serializer {

  visitSendPortSync(SendPortSync x) {
    if (x is _JsSendPortSync) return visitJsSendPortSync(x);
    if (x is _LocalSendPortSync) return visitLocalSendPortSync(x);
    if (x is _RemoteSendPortSync) return visitRemoteSendPortSync(x);
    throw "Unknown port type $x";
  }

  visitJsSendPortSync(_JsSendPortSync x) {
    return [ 'sendport', 'nativejs', x._id ];
  }

  visitLocalSendPortSync(_LocalSendPortSync x) {
    return [ 'sendport', 'dart',
             ReceivePortSync._isolateId, x._receivePort._portId ];
  }

  visitRemoteSendPortSync(_RemoteSendPortSync x) {
    return [ 'sendport', 'dart',
             x._receivePort._isolateId, x._receivePort._portId ];
  }
}

_deserialize(var message) {
  return new _JsDeserializer().deserialize(message);
}


class _JsDeserializer extends _Deserializer {

  static const _UNSPECIFIED = const Object();

  deserializeSendPort(List x) {
    String tag = x[1];
    switch (tag) {
      case 'nativejs':
        num id = x[2];
        return new _JsSendPortSync(id);
      case 'dart':
        num isolateId = x[2];
        num portId = x[3];
        return ReceivePortSync._lookup(isolateId, portId);
      default:
        throw 'Illegal SendPortSync type: $tag';
    }
  }
}

// The receiver is JS.
class _JsSendPortSync implements SendPortSync {

  num _id;
  _JsSendPortSync(this._id);

  callSync(var message) {
    var serialized = _serialize(message);
    var result = _callPortSync(_id, serialized);
    return _deserialize(result);
  }

}

// TODO(vsm): Differentiate between Dart2Js and Dartium isolates.
// The receiver is a different Dart isolate, compiled to JS.
class _RemoteSendPortSync implements SendPortSync {

  int _isolateId;
  int _portId;
  _RemoteSendPortSync(this._isolateId, this._portId);

  callSync(var message) {
    var serialized = _serialize(message);
    var result = _call(_isolateId, _portId, serialized);
    return _deserialize(result);
  }

  static _call(int isolateId, int portId, var message) {
    var target = 'dart-port-$isolateId-$portId'; 
    // TODO(vsm): Make this re-entrant.
    // TODO(vsm): Set this up set once, on the first call.
    var source = '$target-result';
    var result = null;
    var listener = (Event e) {
      result = JSON.parse(_getPortSyncEventData(e));
    };
    window.on[source].add(listener);
    _dispatchEvent(target, [source, message]);
    window.on[source].remove(listener);
    return result;
  }
}

// The receiver is in the same Dart isolate, compiled to JS.
class _LocalSendPortSync implements SendPortSync {

  ReceivePortSync _receivePort;

  _LocalSendPortSync._internal(this._receivePort);

  callSync(var message) {
    // TODO(vsm): Do a more efficient deep copy.
    var copy = _deserialize(_serialize(message));
    var result = _receivePort._callback(copy);
    return _deserialize(_serialize(result));
  }
}

// TODO(vsm): Move this to dart:isolate.  This will take some
// refactoring as there are dependences here on the DOM.  Users
// interact with this class (or interface if we change it) directly -
// new ReceivePortSync.  I think most of the DOM logic could be
// delayed until the corresponding SendPort is registered on the
// window.

// A Dart ReceivePortSync (tagged 'dart' when serialized) is
// identifiable / resolvable by the combination of its isolateid and
// portid.  When a corresponding SendPort is used within the same
// isolate, the _portMap below can be used to obtain the
// ReceivePortSync directly.  Across isolates (or from JS), an
// EventListener can be used to communicate with the port indirectly.
class ReceivePortSync {

  static Map<int, ReceivePortSync> _portMap;
  static int _portIdCount;
  static int _cachedIsolateId;

  num _portId;
  Function _callback;
  EventListener _listener;

  ReceivePortSync() {
    if (_portIdCount == null) {
      _portIdCount = 0;
      _portMap = new Map<int, ReceivePortSync>();
    }
    _portId = _portIdCount++;
    _portMap[_portId] = this;
  }

  static int get _isolateId {
    // TODO(vsm): Make this coherent with existing isolate code.
    if (_cachedIsolateId == null) {
      _cachedIsolateId = _getNewIsolateId();      
    }
    return _cachedIsolateId;
  }

  static String _getListenerName(isolateId, portId) =>
      'dart-port-$isolateId-$portId'; 
  String get _listenerName => _getListenerName(_isolateId, _portId);

  void receive(callback(var message)) {
    _callback = callback;
    if (_listener == null) {
      _listener = (Event e) {
        var data = JSON.parse(_getPortSyncEventData(e));
        var replyTo = data[0];
        var message = _deserialize(data[1]);
        var result = _callback(message);
        _dispatchEvent(replyTo, _serialize(result));
      };
      window.on[_listenerName].add(_listener);
    }
  }

  void close() {
    _portMap.remove(_portId);
    if (_listener != null) window.on[_listenerName].remove(_listener);
  }

  SendPortSync toSendPort() {
    return new _LocalSendPortSync._internal(this);
  }

  static SendPortSync _lookup(int isolateId, int portId) {
    if (isolateId == _isolateId) {
      return _portMap[portId].toSendPort();
    } else {
      return new _RemoteSendPortSync(isolateId, portId);
    }
  }
}

get _isolateId => ReceivePortSync._isolateId;

void _dispatchEvent(String receiver, var message) {
  var event = new CustomEvent(receiver, false, false, JSON.stringify(message));
  window.$dom_dispatchEvent(event);
}

String _getPortSyncEventData(CustomEvent event) => event.detail;