text: /*
   * Copyright (C) 2008 Apple Inc. All Rights Reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
   * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
   * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
   *
   */
  
  #pragma once
  
  #include "ActiveDOMObject.h"
  #include "EventTarget.h"
  #include "ExceptionOr.h"
  #include "MessagePortChannel.h"
  #include "MessagePortIdentifier.h"
  #include "MessageWithMessagePorts.h"
  
  namespace JSC {
  class ExecState;
  class JSObject;
  class JSValue;
  }
  
  namespace WebCore {
  
  class Frame;
  
  class MessagePort final : public ActiveDOMObject, public EventTargetWithInlineData {
  public:
      static Ref<MessagePort> create(ScriptExecutionContext&, const MessagePortIdentifier& local, const MessagePortIdentifier& remote);
      virtual ~MessagePort();
  
      ExceptionOr<void> postMessage(JSC::ExecState&, JSC::JSValue message, Vector<JSC::Strong<JSC::JSObject>>&&);
  
      void start();
      void close();
      void entangle();
  
      // Returns nullptr if the passed-in vector is empty.
      static ExceptionOr<TransferredMessagePortArray> disentanglePorts(Vector<RefPtr<MessagePort>>&&);
      static Vector<RefPtr<MessagePort>> entanglePorts(ScriptExecutionContext&, TransferredMessagePortArray&&);
  
      WEBCORE_EXPORT static bool isExistingMessagePortLocallyReachable(const MessagePortIdentifier&);
      WEBCORE_EXPORT static void notifyMessageAvailable(const MessagePortIdentifier&);
  
      WEBCORE_EXPORT void messageAvailable();
      bool started() const { return m_started; }
      bool closed() const { return m_closed; }
  
      void dispatchMessages();
  
      // Returns null if there is no entangled port, or if the entangled port is run by a different thread.
      // This is used solely to enable a GC optimization. Some platforms may not be able to determine ownership
      // of the remote port (since it may live cross-process) - those platforms may always return null.
      MessagePort* locallyEntangledPort() const;
  
      const MessagePortIdentifier& identifier() const { return m_identifier; }
      const MessagePortIdentifier& remoteIdentifier() const { return m_remoteIdentifier; }
  
      WEBCORE_EXPORT void ref() const;
      WEBCORE_EXPORT void deref() const;
  
      // ActiveDOMObject
      const char* activeDOMObjectName() const final;
      bool canSuspendForDocumentSuspension() const final;
      void contextDestroyed() final;
      void stop() final { close(); }
      bool hasPendingActivity() const final;
  
      WEBCORE_EXPORT bool isLocallyReachable() const;
  
      // EventTargetWithInlineData.
      EventTargetInterface eventTargetInterface() const final { return MessagePortEventTargetInterfaceType; }
      ScriptExecutionContext* scriptExecutionContext() const final { return ActiveDOMObject::scriptExecutionContext(); }
      void refEventTarget() final { ref(); }
      void derefEventTarget() final { deref(); }
  
  private:
      explicit MessagePort(ScriptExecutionContext&, const MessagePortIdentifier& local, const MessagePortIdentifier& remote);
  
      bool addEventListener(const AtomicString& eventType, Ref<EventListener>&&, const AddEventListenerOptions&) final;
      bool removeEventListener(const AtomicString& eventType, EventListener&, const ListenerOptions&) final;
  
      void disentangle();
  
      void registerLocalActivity();
  
      // A port starts out its life entangled, and remains entangled until it is closed or is cloned.
      bool isEntangled() const { return !m_closed && m_entangled; }
  
      bool m_started { false };
      bool m_closed { false };
      bool m_entangled { true };
  
      // Flags to manage querying the remote port for GC purposes
      mutable bool m_mightBeEligibleForGC { false };
      mutable bool m_hasHadLocalActivitySinceLastCheck { false };
      mutable bool m_isRemoteEligibleForGC { false };
      mutable bool m_isAskingRemoteAboutGC { false };
      bool m_hasMessageEventListener { false };
  
      MessagePortIdentifier m_identifier;
      MessagePortIdentifier m_remoteIdentifier;
  
      mutable std::atomic<unsigned> m_refCount { 1 };
  };
  
  } // namespace WebCore
  