rtc_base/messagequeue.cc - src/webrtc - Git at Google

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 #include <algorithm>

 #include "webrtc/rtc_base/atomicops.h"
 #include "webrtc/rtc_base/checks.h"
 #include "webrtc/rtc_base/logging.h"
 #include "webrtc/rtc_base/messagequeue.h"
 #include "webrtc/rtc_base/stringencode.h"
 #include "webrtc/rtc_base/thread.h"
 #include "webrtc/rtc_base/trace_event.h"

 namespace rtc {
 namespace {

 const int kMaxMsgLatency = 150;  // 150 ms
 const int kSlowDispatchLoggingThreshold = 50;  // 50 ms

 class RTC_SCOPED_LOCKABLE MarkProcessingCritScope {
  public:
   MarkProcessingCritScope(const CriticalSection* cs, size_t* processing)
       RTC_EXCLUSIVE_LOCK_FUNCTION(cs)
       : cs_(cs), processing_(processing) {
     cs_->Enter();
     *processing_ += 1;
   }

   ~MarkProcessingCritScope() RTC_UNLOCK_FUNCTION() {
     *processing_ -= 1;
     cs_->Leave();
   }

  private:
   const CriticalSection* const cs_;
   size_t* processing_;

   RTC_DISALLOW_COPY_AND_ASSIGN(MarkProcessingCritScope);
 };
 }  // namespace

 //------------------------------------------------------------------
 // MessageQueueManager

 MessageQueueManager* MessageQueueManager::instance_ = nullptr;

 MessageQueueManager* MessageQueueManager::Instance() {
   // Note: This is not thread safe, but it is first called before threads are
   // spawned.
   if (!instance_)
     instance_ = new MessageQueueManager;
   return instance_;
 }

 bool MessageQueueManager::IsInitialized() {
   return instance_ != nullptr;
 }

 MessageQueueManager::MessageQueueManager() : processing_(0) {}

 MessageQueueManager::~MessageQueueManager() {
 }

 void MessageQueueManager::Add(MessageQueue *message_queue) {
   return Instance()->AddInternal(message_queue);
 }
 void MessageQueueManager::AddInternal(MessageQueue *message_queue) {
   CritScope cs(&crit_);
   // Prevent changes while the list of message queues is processed.
   RTC_DCHECK_EQ(processing_, 0);
   message_queues_.push_back(message_queue);
 }

 void MessageQueueManager::Remove(MessageQueue *message_queue) {
   // If there isn't a message queue manager instance, then there isn't a queue
   // to remove.
   if (!instance_) return;
   return Instance()->RemoveInternal(message_queue);
 }
 void MessageQueueManager::RemoveInternal(MessageQueue *message_queue) {
   // If this is the last MessageQueue, destroy the manager as well so that
   // we don't leak this object at program shutdown. As mentioned above, this is
   // not thread-safe, but this should only happen at program termination (when
   // the ThreadManager is destroyed, and threads are no longer active).
   bool destroy = false;
   {
     CritScope cs(&crit_);
     // Prevent changes while the list of message queues is processed.
     RTC_DCHECK_EQ(processing_, 0);
     std::vector<MessageQueue *>::iterator iter;
     iter = std::find(message_queues_.begin(), message_queues_.end(),
                      message_queue);
     if (iter != message_queues_.end()) {
       message_queues_.erase(iter);
     }
     destroy = message_queues_.empty();
   }
   if (destroy) {
     instance_ = nullptr;
     delete this;
   }
 }

 void MessageQueueManager::Clear(MessageHandler *handler) {
   // If there isn't a message queue manager instance, then there aren't any
   // queues to remove this handler from.
   if (!instance_) return;
   return Instance()->ClearInternal(handler);
 }
 void MessageQueueManager::ClearInternal(MessageHandler *handler) {
   // Deleted objects may cause re-entrant calls to ClearInternal. This is
   // allowed as the list of message queues does not change while queues are
   // cleared.
   MarkProcessingCritScope cs(&crit_, &processing_);
   std::vector<MessageQueue *>::iterator iter;
   for (MessageQueue* queue : message_queues_) {
     queue->Clear(handler);
   }
 }

 void MessageQueueManager::ProcessAllMessageQueues() {
   if (!instance_) {
     return;
   }
   return Instance()->ProcessAllMessageQueuesInternal();
 }

 void MessageQueueManager::ProcessAllMessageQueuesInternal() {
   // This works by posting a delayed message at the current time and waiting
   // for it to be dispatched on all queues, which will ensure that all messages
   // that came before it were also dispatched.
   volatile int queues_not_done = 0;

   // This class is used so that whether the posted message is processed, or the
   // message queue is simply cleared, queues_not_done gets decremented.
   class ScopedIncrement : public MessageData {
    public:
     ScopedIncrement(volatile int* value) : value_(value) {
       AtomicOps::Increment(value_);
     }
     ~ScopedIncrement() override { AtomicOps::Decrement(value_); }

    private:
     volatile int* value_;
   };

   {
     MarkProcessingCritScope cs(&crit_, &processing_);
     for (MessageQueue* queue : message_queues_) {
       if (!queue->IsProcessingMessages()) {
         // If the queue is not processing messages, it can
         // be ignored. If we tried to post a message to it, it would be dropped
         // or ignored.
         continue;
       }
       queue->PostDelayed(RTC_FROM_HERE, 0, nullptr, MQID_DISPOSE,
                          new ScopedIncrement(&queues_not_done));
     }
   }
   // Note: One of the message queues may have been on this thread, which is why
   // we can't synchronously wait for queues_not_done to go to 0; we need to
   // process messages as well.
   while (AtomicOps::AcquireLoad(&queues_not_done) > 0) {
     rtc::Thread::Current()->ProcessMessages(0);
   }
 }

 //------------------------------------------------------------------
 // MessageQueue
 MessageQueue::MessageQueue(SocketServer* ss, bool init_queue)
     : fPeekKeep_(false),
       dmsgq_next_num_(0),
       fInitialized_(false),
       fDestroyed_(false),
       stop_(0),
       ss_(ss) {
   RTC_DCHECK(ss);
   // Currently, MessageQueue holds a socket server, and is the base class for
   // Thread.  It seems like it makes more sense for Thread to hold the socket
   // server, and provide it to the MessageQueue, since the Thread controls
   // the I/O model, and MQ is agnostic to those details.  Anyway, this causes
   // messagequeue_unittest to depend on network libraries... yuck.
   ss_->SetMessageQueue(this);
   if (init_queue) {
     DoInit();
   }
 }

 MessageQueue::MessageQueue(std::unique_ptr<SocketServer> ss, bool init_queue)
     : MessageQueue(ss.get(), init_queue) {
   own_ss_ = std::move(ss);
 }

 MessageQueue::~MessageQueue() {
   DoDestroy();
 }

 void MessageQueue::DoInit() {
   if (fInitialized_) {
     return;
   }

   fInitialized_ = true;
   MessageQueueManager::Add(this);
 }

 void MessageQueue::DoDestroy() {
   if (fDestroyed_) {
     return;
   }

   fDestroyed_ = true;
   // The signal is done from here to ensure
   // that it always gets called when the queue
   // is going away.
   SignalQueueDestroyed();
   MessageQueueManager::Remove(this);
   Clear(nullptr);

   if (ss_) {
     ss_->SetMessageQueue(nullptr);
   }
 }

 SocketServer* MessageQueue::socketserver() {
   return ss_;
 }

 void MessageQueue::WakeUpSocketServer() {
   ss_->WakeUp();
 }

 void MessageQueue::Quit() {
   AtomicOps::ReleaseStore(&stop_, 1);
   WakeUpSocketServer();
 }

 bool MessageQueue::IsQuitting() {
   return AtomicOps::AcquireLoad(&stop_) != 0;
 }

 bool MessageQueue::IsProcessingMessages() {
   return !IsQuitting();
 }

 void MessageQueue::Restart() {
   AtomicOps::ReleaseStore(&stop_, 0);
 }

 bool MessageQueue::Peek(Message *pmsg, int cmsWait) {
   if (fPeekKeep_) {
     *pmsg = msgPeek_;
     return true;
   }
   if (!Get(pmsg, cmsWait))
     return false;
   msgPeek_ = *pmsg;
   fPeekKeep_ = true;
   return true;
 }

 bool MessageQueue::Get(Message *pmsg, int cmsWait, bool process_io) {
   // Return and clear peek if present
   // Always return the peek if it exists so there is Peek/Get symmetry

   if (fPeekKeep_) {
     *pmsg = msgPeek_;
     fPeekKeep_ = false;
     return true;
   }

   // Get w/wait + timer scan / dispatch + socket / event multiplexer dispatch

   int64_t cmsTotal = cmsWait;
   int64_t cmsElapsed = 0;
   int64_t msStart = TimeMillis();
   int64_t msCurrent = msStart;
   while (true) {
     // Check for sent messages
     ReceiveSends();

     // Check for posted events
     int64_t cmsDelayNext = kForever;
     bool first_pass = true;
     while (true) {
       // All queue operations need to be locked, but nothing else in this loop
       // (specifically handling disposed message) can happen inside the crit.
       // Otherwise, disposed MessageHandlers will cause deadlocks.
       {
         CritScope cs(&crit_);
         // On the first pass, check for delayed messages that have been
         // triggered and calculate the next trigger time.
         if (first_pass) {
           first_pass = false;
           while (!dmsgq_.empty()) {
             if (msCurrent < dmsgq_.top().msTrigger_) {
               cmsDelayNext = TimeDiff(dmsgq_.top().msTrigger_, msCurrent);
               break;
             }
             msgq_.push_back(dmsgq_.top().msg_);
             dmsgq_.pop();
           }
         }
         // Pull a message off the message queue, if available.
         if (msgq_.empty()) {
           break;
         } else {
           *pmsg = msgq_.front();
           msgq_.pop_front();
         }
       }  // crit_ is released here.

       // Log a warning for time-sensitive messages that we're late to deliver.
       if (pmsg->ts_sensitive) {
         int64_t delay = TimeDiff(msCurrent, pmsg->ts_sensitive);
         if (delay > 0) {
           LOG_F(LS_WARNING) << "id: " << pmsg->message_id << "  delay: "
                             << (delay + kMaxMsgLatency) << "ms";
         }
       }
       // If this was a dispose message, delete it and skip it.
       if (MQID_DISPOSE == pmsg->message_id) {
         RTC_DCHECK(nullptr == pmsg->phandler);
         delete pmsg->pdata;
         *pmsg = Message();
         continue;
       }
       return true;
     }

     if (IsQuitting())
       break;

     // Which is shorter, the delay wait or the asked wait?

     int64_t cmsNext;
     if (cmsWait == kForever) {
       cmsNext = cmsDelayNext;
     } else {
       cmsNext = std::max<int64_t>(0, cmsTotal - cmsElapsed);
       if ((cmsDelayNext != kForever) && (cmsDelayNext < cmsNext))
         cmsNext = cmsDelayNext;
     }

     {
       // Wait and multiplex in the meantime
       if (!ss_->Wait(static_cast<int>(cmsNext), process_io))
         return false;
     }

     // If the specified timeout expired, return

     msCurrent = TimeMillis();
     cmsElapsed = TimeDiff(msCurrent, msStart);
     if (cmsWait != kForever) {
       if (cmsElapsed >= cmsWait)
         return false;
     }
   }
   return false;
 }

 void MessageQueue::ReceiveSends() {
 }

 void MessageQueue::Post(const Location& posted_from,
                         MessageHandler* phandler,
                         uint32_t id,
                         MessageData* pdata,
                         bool time_sensitive) {
   if (IsQuitting())
     return;

   // Keep thread safe
   // Add the message to the end of the queue
   // Signal for the multiplexer to return

   {
     CritScope cs(&crit_);
     Message msg;
     msg.posted_from = posted_from;
     msg.phandler = phandler;
     msg.message_id = id;
     msg.pdata = pdata;
     if (time_sensitive) {
       msg.ts_sensitive = TimeMillis() + kMaxMsgLatency;
     }
     msgq_.push_back(msg);
   }
   WakeUpSocketServer();
 }

 void MessageQueue::PostDelayed(const Location& posted_from,
                                int cmsDelay,
                                MessageHandler* phandler,
                                uint32_t id,
                                MessageData* pdata) {
   return DoDelayPost(posted_from, cmsDelay, TimeAfter(cmsDelay), phandler, id,
                      pdata);
 }

 void MessageQueue::PostAt(const Location& posted_from,
                           uint32_t tstamp,
                           MessageHandler* phandler,
                           uint32_t id,
                           MessageData* pdata) {
   // This should work even if it is used (unexpectedly).
   int64_t delay = static_cast<uint32_t>(TimeMillis()) - tstamp;
   return DoDelayPost(posted_from, delay, tstamp, phandler, id, pdata);
 }

 void MessageQueue::PostAt(const Location& posted_from,
                           int64_t tstamp,
                           MessageHandler* phandler,
                           uint32_t id,
                           MessageData* pdata) {
   return DoDelayPost(posted_from, TimeUntil(tstamp), tstamp, phandler, id,
                      pdata);
 }

 void MessageQueue::DoDelayPost(const Location& posted_from,
                                int64_t cmsDelay,
                                int64_t tstamp,
                                MessageHandler* phandler,
                                uint32_t id,
                                MessageData* pdata) {
   if (IsQuitting()) {
     return;
   }

   // Keep thread safe
   // Add to the priority queue. Gets sorted soonest first.
   // Signal for the multiplexer to return.

   {
     CritScope cs(&crit_);
     Message msg;
     msg.posted_from = posted_from;
     msg.phandler = phandler;
     msg.message_id = id;
     msg.pdata = pdata;
     DelayedMessage dmsg(cmsDelay, tstamp, dmsgq_next_num_, msg);
     dmsgq_.push(dmsg);
     // If this message queue processes 1 message every millisecond for 50 days,
     // we will wrap this number.  Even then, only messages with identical times
     // will be misordered, and then only briefly.  This is probably ok.
     ++dmsgq_next_num_;
     RTC_DCHECK_NE(0, dmsgq_next_num_);
   }
   WakeUpSocketServer();
 }

 int MessageQueue::GetDelay() {
   CritScope cs(&crit_);

   if (!msgq_.empty())
     return 0;

   if (!dmsgq_.empty()) {
     int delay = TimeUntil(dmsgq_.top().msTrigger_);
     if (delay < 0)
       delay = 0;
     return delay;
   }

   return kForever;
 }

 void MessageQueue::Clear(MessageHandler* phandler,
                          uint32_t id,
                          MessageList* removed) {
   CritScope cs(&crit_);

   // Remove messages with phandler

   if (fPeekKeep_ && msgPeek_.Match(phandler, id)) {
     if (removed) {
       removed->push_back(msgPeek_);
     } else {
       delete msgPeek_.pdata;
     }
     fPeekKeep_ = false;
   }

   // Remove from ordered message queue

   for (MessageList::iterator it = msgq_.begin(); it != msgq_.end();) {
     if (it->Match(phandler, id)) {
       if (removed) {
         removed->push_back(*it);
       } else {
         delete it->pdata;
       }
       it = msgq_.erase(it);
     } else {
       ++it;
     }
   }

   // Remove from priority queue. Not directly iterable, so use this approach

   PriorityQueue::container_type::iterator new_end = dmsgq_.container().begin();
   for (PriorityQueue::container_type::iterator it = new_end;
        it != dmsgq_.container().end(); ++it) {
     if (it->msg_.Match(phandler, id)) {
       if (removed) {
         removed->push_back(it->msg_);
       } else {
         delete it->msg_.pdata;
       }
     } else {
       *new_end++ = *it;
     }
   }
   dmsgq_.container().erase(new_end, dmsgq_.container().end());
   dmsgq_.reheap();
 }

 void MessageQueue::Dispatch(Message *pmsg) {
   TRACE_EVENT2("webrtc", "MessageQueue::Dispatch", "src_file_and_line",
                pmsg->posted_from.file_and_line(), "src_func",
                pmsg->posted_from.function_name());
   int64_t start_time = TimeMillis();
   pmsg->phandler->OnMessage(pmsg);
   int64_t end_time = TimeMillis();
   int64_t diff = TimeDiff(end_time, start_time);
   if (diff >= kSlowDispatchLoggingThreshold) {
     LOG(LS_INFO) << "Message took " << diff << "ms to dispatch. Posted from: "
                  << pmsg->posted_from.ToString();
   }
 }

 }  // namespace rtc
	/*
	* Copyright 2004 The WebRTC Project Authors. All rights reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/
	#include <algorithm>

	#include "webrtc/rtc_base/atomicops.h"
	#include "webrtc/rtc_base/checks.h"
	#include "webrtc/rtc_base/logging.h"
	#include "webrtc/rtc_base/messagequeue.h"
	#include "webrtc/rtc_base/stringencode.h"
	#include "webrtc/rtc_base/thread.h"
	#include "webrtc/rtc_base/trace_event.h"

	namespace rtc {
	namespace {

	const int kMaxMsgLatency = 150; // 150 ms
	const int kSlowDispatchLoggingThreshold = 50; // 50 ms

	class RTC_SCOPED_LOCKABLE MarkProcessingCritScope {
	public:
	MarkProcessingCritScope(const CriticalSection* cs, size_t* processing)
	RTC_EXCLUSIVE_LOCK_FUNCTION(cs)
	: cs_(cs), processing_(processing) {
	cs_->Enter();
	*processing_ += 1;
	}

	~MarkProcessingCritScope() RTC_UNLOCK_FUNCTION() {
	*processing_ -= 1;
	cs_->Leave();
	}

	private:
	const CriticalSection* const cs_;
	size_t* processing_;

	RTC_DISALLOW_COPY_AND_ASSIGN(MarkProcessingCritScope);
	};
	} // namespace

	//------------------------------------------------------------------
	// MessageQueueManager

	MessageQueueManager* MessageQueueManager::instance_ = nullptr;

	MessageQueueManager* MessageQueueManager::Instance() {
	// Note: This is not thread safe, but it is first called before threads are
	// spawned.
	if (!instance_)
	instance_ = new MessageQueueManager;
	return instance_;
	}

	bool MessageQueueManager::IsInitialized() {
	return instance_ != nullptr;
	}

	MessageQueueManager::MessageQueueManager() : processing_(0) {}

	MessageQueueManager::~MessageQueueManager() {
	}

	void MessageQueueManager::Add(MessageQueue *message_queue) {
	return Instance()->AddInternal(message_queue);
	}
	void MessageQueueManager::AddInternal(MessageQueue *message_queue) {
	CritScope cs(&crit_);
	// Prevent changes while the list of message queues is processed.
	RTC_DCHECK_EQ(processing_, 0);
	message_queues_.push_back(message_queue);
	}

	void MessageQueueManager::Remove(MessageQueue *message_queue) {
	// If there isn't a message queue manager instance, then there isn't a queue
	// to remove.
	if (!instance_) return;
	return Instance()->RemoveInternal(message_queue);
	}
	void MessageQueueManager::RemoveInternal(MessageQueue *message_queue) {
	// If this is the last MessageQueue, destroy the manager as well so that
	// we don't leak this object at program shutdown. As mentioned above, this is
	// not thread-safe, but this should only happen at program termination (when
	// the ThreadManager is destroyed, and threads are no longer active).
	bool destroy = false;
	{
	CritScope cs(&crit_);
	// Prevent changes while the list of message queues is processed.
	RTC_DCHECK_EQ(processing_, 0);
	std::vector<MessageQueue *>::iterator iter;
	iter = std::find(message_queues_.begin(), message_queues_.end(),
	message_queue);
	if (iter != message_queues_.end()) {
	message_queues_.erase(iter);
	}
	destroy = message_queues_.empty();
	}
	if (destroy) {
	instance_ = nullptr;
	delete this;
	}
	}

	void MessageQueueManager::Clear(MessageHandler *handler) {
	// If there isn't a message queue manager instance, then there aren't any
	// queues to remove this handler from.
	if (!instance_) return;
	return Instance()->ClearInternal(handler);
	}
	void MessageQueueManager::ClearInternal(MessageHandler *handler) {
	// Deleted objects may cause re-entrant calls to ClearInternal. This is
	// allowed as the list of message queues does not change while queues are
	// cleared.
	MarkProcessingCritScope cs(&crit_, &processing_);
	std::vector<MessageQueue *>::iterator iter;
	for (MessageQueue* queue : message_queues_) {
	queue->Clear(handler);
	}
	}

	void MessageQueueManager::ProcessAllMessageQueues() {
	if (!instance_) {
	return;
	}
	return Instance()->ProcessAllMessageQueuesInternal();
	}

	void MessageQueueManager::ProcessAllMessageQueuesInternal() {
	// This works by posting a delayed message at the current time and waiting
	// for it to be dispatched on all queues, which will ensure that all messages
	// that came before it were also dispatched.
	volatile int queues_not_done = 0;

	// This class is used so that whether the posted message is processed, or the
	// message queue is simply cleared, queues_not_done gets decremented.
	class ScopedIncrement : public MessageData {
	public:
	ScopedIncrement(volatile int* value) : value_(value) {
	AtomicOps::Increment(value_);
	}
	~ScopedIncrement() override { AtomicOps::Decrement(value_); }

	private:
	volatile int* value_;
	};

	{
	MarkProcessingCritScope cs(&crit_, &processing_);
	for (MessageQueue* queue : message_queues_) {
	if (!queue->IsProcessingMessages()) {
	// If the queue is not processing messages, it can
	// be ignored. If we tried to post a message to it, it would be dropped
	// or ignored.
	continue;
	}
	queue->PostDelayed(RTC_FROM_HERE, 0, nullptr, MQID_DISPOSE,
	new ScopedIncrement(&queues_not_done));
	}
	}
	// Note: One of the message queues may have been on this thread, which is why
	// we can't synchronously wait for queues_not_done to go to 0; we need to
	// process messages as well.
	while (AtomicOps::AcquireLoad(&queues_not_done) > 0) {
	rtc::Thread::Current()->ProcessMessages(0);
	}
	}

	//------------------------------------------------------------------
	// MessageQueue
	MessageQueue::MessageQueue(SocketServer* ss, bool init_queue)
	: fPeekKeep_(false),
	dmsgq_next_num_(0),
	fInitialized_(false),
	fDestroyed_(false),
	stop_(0),
	ss_(ss) {
	RTC_DCHECK(ss);
	// Currently, MessageQueue holds a socket server, and is the base class for
	// Thread. It seems like it makes more sense for Thread to hold the socket
	// server, and provide it to the MessageQueue, since the Thread controls
	// the I/O model, and MQ is agnostic to those details. Anyway, this causes
	// messagequeue_unittest to depend on network libraries... yuck.
	ss_->SetMessageQueue(this);
	if (init_queue) {
	DoInit();
	}
	}

	MessageQueue::MessageQueue(std::unique_ptr<SocketServer> ss, bool init_queue)
	: MessageQueue(ss.get(), init_queue) {
	own_ss_ = std::move(ss);
	}

	MessageQueue::~MessageQueue() {
	DoDestroy();
	}

	void MessageQueue::DoInit() {
	if (fInitialized_) {
	return;
	}

	fInitialized_ = true;
	MessageQueueManager::Add(this);
	}

	void MessageQueue::DoDestroy() {
	if (fDestroyed_) {
	return;
	}

	fDestroyed_ = true;
	// The signal is done from here to ensure
	// that it always gets called when the queue
	// is going away.
	SignalQueueDestroyed();
	MessageQueueManager::Remove(this);
	Clear(nullptr);

	if (ss_) {
	ss_->SetMessageQueue(nullptr);
	}
	}

	SocketServer* MessageQueue::socketserver() {
	return ss_;
	}

	void MessageQueue::WakeUpSocketServer() {
	ss_->WakeUp();
	}

	void MessageQueue::Quit() {
	AtomicOps::ReleaseStore(&stop_, 1);
	WakeUpSocketServer();
	}

	bool MessageQueue::IsQuitting() {
	return AtomicOps::AcquireLoad(&stop_) != 0;
	}

	bool MessageQueue::IsProcessingMessages() {
	return !IsQuitting();
	}

	void MessageQueue::Restart() {
	AtomicOps::ReleaseStore(&stop_, 0);
	}

	bool MessageQueue::Peek(Message *pmsg, int cmsWait) {
	if (fPeekKeep_) {
	*pmsg = msgPeek_;
	return true;
	}
	if (!Get(pmsg, cmsWait))
	return false;
	msgPeek_ = *pmsg;
	fPeekKeep_ = true;
	return true;
	}

	bool MessageQueue::Get(Message *pmsg, int cmsWait, bool process_io) {
	// Return and clear peek if present
	// Always return the peek if it exists so there is Peek/Get symmetry

	if (fPeekKeep_) {
	*pmsg = msgPeek_;
	fPeekKeep_ = false;
	return true;
	}

	// Get w/wait + timer scan / dispatch + socket / event multiplexer dispatch

	int64_t cmsTotal = cmsWait;
	int64_t cmsElapsed = 0;
	int64_t msStart = TimeMillis();
	int64_t msCurrent = msStart;
	while (true) {
	// Check for sent messages
	ReceiveSends();

	// Check for posted events
	int64_t cmsDelayNext = kForever;
	bool first_pass = true;
	while (true) {
	// All queue operations need to be locked, but nothing else in this loop
	// (specifically handling disposed message) can happen inside the crit.
	// Otherwise, disposed MessageHandlers will cause deadlocks.
	{
	CritScope cs(&crit_);
	// On the first pass, check for delayed messages that have been
	// triggered and calculate the next trigger time.
	if (first_pass) {
	first_pass = false;
	while (!dmsgq_.empty()) {
	if (msCurrent < dmsgq_.top().msTrigger_) {
	cmsDelayNext = TimeDiff(dmsgq_.top().msTrigger_, msCurrent);
	break;
	}
	msgq_.push_back(dmsgq_.top().msg_);
	dmsgq_.pop();
	}
	}
	// Pull a message off the message queue, if available.
	if (msgq_.empty()) {
	break;
	} else {
	*pmsg = msgq_.front();
	msgq_.pop_front();
	}
	} // crit_ is released here.

	// Log a warning for time-sensitive messages that we're late to deliver.
	if (pmsg->ts_sensitive) {
	int64_t delay = TimeDiff(msCurrent, pmsg->ts_sensitive);
	if (delay > 0) {
	LOG_F(LS_WARNING) << "id: " << pmsg->message_id << " delay: "
	<< (delay + kMaxMsgLatency) << "ms";
	}
	}
	// If this was a dispose message, delete it and skip it.
	if (MQID_DISPOSE == pmsg->message_id) {
	RTC_DCHECK(nullptr == pmsg->phandler);
	delete pmsg->pdata;
	*pmsg = Message();
	continue;
	}
	return true;
	}

	if (IsQuitting())
	break;

	// Which is shorter, the delay wait or the asked wait?

	int64_t cmsNext;
	if (cmsWait == kForever) {
	cmsNext = cmsDelayNext;
	} else {
	cmsNext = std::max<int64_t>(0, cmsTotal - cmsElapsed);
	if ((cmsDelayNext != kForever) && (cmsDelayNext < cmsNext))
	cmsNext = cmsDelayNext;
	}

	{
	// Wait and multiplex in the meantime
	if (!ss_->Wait(static_cast<int>(cmsNext), process_io))
	return false;
	}

	// If the specified timeout expired, return

	msCurrent = TimeMillis();
	cmsElapsed = TimeDiff(msCurrent, msStart);
	if (cmsWait != kForever) {
	if (cmsElapsed >= cmsWait)
	return false;
	}
	}
	return false;
	}

	void MessageQueue::ReceiveSends() {
	}

	void MessageQueue::Post(const Location& posted_from,
	MessageHandler* phandler,
	uint32_t id,
	MessageData* pdata,
	bool time_sensitive) {
	if (IsQuitting())
	return;

	// Keep thread safe
	// Add the message to the end of the queue
	// Signal for the multiplexer to return

	{
	CritScope cs(&crit_);
	Message msg;
	msg.posted_from = posted_from;
	msg.phandler = phandler;
	msg.message_id = id;
	msg.pdata = pdata;
	if (time_sensitive) {
	msg.ts_sensitive = TimeMillis() + kMaxMsgLatency;
	}
	msgq_.push_back(msg);
	}
	WakeUpSocketServer();
	}

	void MessageQueue::PostDelayed(const Location& posted_from,
	int cmsDelay,
	MessageHandler* phandler,
	uint32_t id,
	MessageData* pdata) {
	return DoDelayPost(posted_from, cmsDelay, TimeAfter(cmsDelay), phandler, id,
	pdata);
	}

	void MessageQueue::PostAt(const Location& posted_from,
	uint32_t tstamp,
	MessageHandler* phandler,
	uint32_t id,
	MessageData* pdata) {
	// This should work even if it is used (unexpectedly).
	int64_t delay = static_cast<uint32_t>(TimeMillis()) - tstamp;
	return DoDelayPost(posted_from, delay, tstamp, phandler, id, pdata);
	}

	void MessageQueue::PostAt(const Location& posted_from,
	int64_t tstamp,
	MessageHandler* phandler,
	uint32_t id,
	MessageData* pdata) {
	return DoDelayPost(posted_from, TimeUntil(tstamp), tstamp, phandler, id,
	pdata);
	}

	void MessageQueue::DoDelayPost(const Location& posted_from,
	int64_t cmsDelay,
	int64_t tstamp,
	MessageHandler* phandler,
	uint32_t id,
	MessageData* pdata) {
	if (IsQuitting()) {
	return;
	}

	// Keep thread safe
	// Add to the priority queue. Gets sorted soonest first.
	// Signal for the multiplexer to return.

	{
	CritScope cs(&crit_);
	Message msg;
	msg.posted_from = posted_from;
	msg.phandler = phandler;
	msg.message_id = id;
	msg.pdata = pdata;
	DelayedMessage dmsg(cmsDelay, tstamp, dmsgq_next_num_, msg);
	dmsgq_.push(dmsg);
	// If this message queue processes 1 message every millisecond for 50 days,
	// we will wrap this number. Even then, only messages with identical times
	// will be misordered, and then only briefly. This is probably ok.
	++dmsgq_next_num_;
	RTC_DCHECK_NE(0, dmsgq_next_num_);
	}
	WakeUpSocketServer();
	}

	int MessageQueue::GetDelay() {
	CritScope cs(&crit_);

	if (!msgq_.empty())
	return 0;

	if (!dmsgq_.empty()) {
	int delay = TimeUntil(dmsgq_.top().msTrigger_);
	if (delay < 0)
	delay = 0;
	return delay;
	}

	return kForever;
	}

	void MessageQueue::Clear(MessageHandler* phandler,
	uint32_t id,
	MessageList* removed) {
	CritScope cs(&crit_);

	// Remove messages with phandler

	if (fPeekKeep_ && msgPeek_.Match(phandler, id)) {
	if (removed) {
	removed->push_back(msgPeek_);
	} else {
	delete msgPeek_.pdata;
	}
	fPeekKeep_ = false;
	}

	// Remove from ordered message queue

	for (MessageList::iterator it = msgq_.begin(); it != msgq_.end();) {
	if (it->Match(phandler, id)) {
	if (removed) {
	removed->push_back(*it);
	} else {
	delete it->pdata;
	}
	it = msgq_.erase(it);
	} else {
	++it;
	}
	}

	// Remove from priority queue. Not directly iterable, so use this approach

	PriorityQueue::container_type::iterator new_end = dmsgq_.container().begin();
	for (PriorityQueue::container_type::iterator it = new_end;
	it != dmsgq_.container().end(); ++it) {
	if (it->msg_.Match(phandler, id)) {
	if (removed) {
	removed->push_back(it->msg_);
	} else {
	delete it->msg_.pdata;
	}
	} else {
	new_end++ = it;
	}
	}
	dmsgq_.container().erase(new_end, dmsgq_.container().end());
	dmsgq_.reheap();
	}

	void MessageQueue::Dispatch(Message *pmsg) {
	TRACE_EVENT2("webrtc", "MessageQueue::Dispatch", "src_file_and_line",
	pmsg->posted_from.file_and_line(), "src_func",
	pmsg->posted_from.function_name());
	int64_t start_time = TimeMillis();
	pmsg->phandler->OnMessage(pmsg);
	int64_t end_time = TimeMillis();
	int64_t diff = TimeDiff(end_time, start_time);
	if (diff >= kSlowDispatchLoggingThreshold) {
	LOG(LS_INFO) << "Message took " << diff << "ms to dispatch. Posted from: "
	<< pmsg->posted_from.ToString();
	}
	}

	} // namespace rtc