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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/UniquePtr.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 final : public nsISupports,
public sigslot::has_slots<> {
public:
TransportFlow()
: id_("(anonymous)"),
state_(TransportLayer::TS_NONE),
layers_(new std::deque<TransportLayer *>) {}
explicit TransportFlow(const std::string id)
: id_(id),
state_(TransportLayer::TS_NONE),
layers_(new std::deque<TransportLayer *>) {}
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:
~TransportFlow();
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_;
UniquePtr<std::deque<TransportLayer *>> layers_;
nsCOMPtr<nsIEventTarget> target_;
};
} // close namespace
#endif
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