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 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* vim: set ts=2 et sw=2 tw=80: */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this file,

  * You can obtain one at http://mozilla.org/MPL/2.0/. */

 // Original author: ekr@rtfm.com

 #ifndef transportflow_h__

 #define transportflow_h__

 #include <deque>

 #include <queue>

 #include <string>

 #include "nscore.h"

 #include "nsISupportsImpl.h"

 #include "mozilla/Scoped.h"

 #include "transportlayer.h"

 #include "m_cpp_utils.h"

 #include "nsAutoPtr.h"

 // A stack of transport layers acts as a flow.

 // Generally, one reads and writes to the top layer.

 // This code has a confusing hybrid threading model which

 // probably needs some eventual refactoring.

 // TODO(ekr@rtfm.com): Bug 844891

 //

 // TransportFlows are not inherently bound to a thread *but*

 // TransportLayers can be. If any layer in a flow is bound

 // to a given thread, then all layers in the flow MUST be

 // bound to that thread and you can only manipulate the

 // flow (push layers, write, etc.) on that thread.

 //

 // The sole official exception to this is that you are

 // allowed to *destroy* a flow off the bound thread provided

 // that there are no listeners on its signals. This exception

 // is designed to allow idioms where you create the flow

 // and then something goes wrong and you destroy it and

 // you don't want to bother with a thread dispatch.

 //

 // Eventually we hope to relax the "no listeners"

 // restriction by thread-locking the signals, but previous

 // attempts have caused deadlocks.

 //

 // Most of these invariants are enforced by hard asserts

 // (i.e., those which fire even in production builds).

 namespace mozilla {

 class TransportFlow : public nsISupports,

                       public sigslot::has_slots<> {

  public:

   TransportFlow()

     : id_("(anonymous)"),

       state_(TransportLayer::TS_NONE),

       layers_(new std::deque<TransportLayer *>) {}

   TransportFlow(const std::string id)

     : id_(id),

       state_(TransportLayer::TS_NONE),

       layers_(new std::deque<TransportLayer *>) {}

   ~TransportFlow();

   const std::string& id() const { return id_; }

   // Layer management. Note PushLayer() is not thread protected, so

   // either:

   // (a) Do it in the thread handling the I/O

   // (b) Do it before you activate the I/O system

   //

   // The flow takes ownership of the layers after a successful

   // push.

   nsresult PushLayer(TransportLayer *layer);

   // Convenience function to push multiple layers on. Layers

   // are pushed on in the order that they are in the queue.

   // Any failures cause the flow to become inoperable and

   // destroys all the layers including those already pushed.

   // TODO(ekr@rtfm.com): Change layers to be ref-counted.

   nsresult PushLayers(nsAutoPtr<std::queue<TransportLayer *> > layers);

   TransportLayer *top() const;

   TransportLayer *GetLayer(const std::string& id) const;

   // Wrappers for whatever TLayer happens to be the top layer

   // at the time. This way you don't need to do top()->Foo().

   TransportLayer::State state(); // Current state

   TransportResult SendPacket(const unsigned char *data, size_t len);

   // State has changed. Reflects the top flow.

   sigslot::signal2<TransportFlow *, TransportLayer::State>

     SignalStateChange;

   // Data received on the flow

   sigslot::signal3<TransportFlow*, const unsigned char *, size_t>

     SignalPacketReceived;

   bool Contains(TransportLayer *layer) const;

   NS_DECL_THREADSAFE_ISUPPORTS

  private:

   DISALLOW_COPY_ASSIGN(TransportFlow);

   // Check if we are on the right thread

   void CheckThread() const {

     if (!CheckThreadInt())

       MOZ_CRASH();

   }

   bool CheckThreadInt() const {

     bool on;

     if (!target_)  // OK if no thread set.

       return true;

     if (NS_FAILED(target_->IsOnCurrentThread(&on)))

       return false;

     return on;

   }

   void EnsureSameThread(TransportLayer *layer);

   void StateChange(TransportLayer *layer, TransportLayer::State state);

   void StateChangeInt(TransportLayer::State state);

   void PacketReceived(TransportLayer* layer, const unsigned char *data,

       size_t len);

   static void DestroyFinal(nsAutoPtr<std::deque<TransportLayer *> > layers);

   // Overload needed because we use deque internally and queue externally.

   static void ClearLayers(std::deque<TransportLayer *>* layers);

   static void ClearLayers(std::queue<TransportLayer *>* layers);

   std::string id_;

   TransportLayer::State state_;

   ScopedDeletePtr<std::deque<TransportLayer *> > layers_;

   nsCOMPtr<nsIEventTarget> target_;

 };

 }  // close namespace

 #endif