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* 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 <list>
#include <memory>
#include <string>
#include <vector>
#if defined(WEBRTC_POSIX)
#include <pthread.h>
#include "webrtc/rtc_base/constructormagic.h"
#include "webrtc/rtc_base/event.h"
#include "webrtc/rtc_base/messagequeue.h"
#include "webrtc/rtc_base/platform_thread_types.h"
#if defined(WEBRTC_WIN)
#include "webrtc/rtc_base/win32.h"
namespace rtc {
class Thread;
class ThreadManager {
static const int kForever = -1;
// Singleton, constructor and destructor are private.
static ThreadManager* Instance();
Thread* CurrentThread();
void SetCurrentThread(Thread* thread);
// Returns a thread object with its thread_ ivar set
// to whatever the OS uses to represent the thread.
// If there already *is* a Thread object corresponding to this thread,
// this method will return that. Otherwise it creates a new Thread
// object whose wrapped() method will return true, and whose
// handle will, on Win32, be opened with only synchronization privileges -
// if you need more privilegs, rather than changing this method, please
// write additional code to adjust the privileges, or call a different
// factory method of your own devising, because this one gets used in
// unexpected contexts (like inside browser plugins) and it would be a
// shame to break it. It is also conceivable on Win32 that we won't even
// be able to get synchronization privileges, in which case the result
// will have a null handle.
Thread *WrapCurrentThread();
void UnwrapCurrentThread();
bool IsMainThread();
#if defined(WEBRTC_POSIX)
pthread_key_t key_;
#if defined(WEBRTC_WIN)
DWORD key_;
// The thread to potentially autowrap.
PlatformThreadRef main_thread_ref_;
struct _SendMessage {
_SendMessage() {}
Thread *thread;
Message msg;
bool *ready;
class Runnable {
virtual ~Runnable() {}
virtual void Run(Thread* thread) = 0;
Runnable() {}
class RTC_LOCKABLE Thread : public MessageQueue {
// The default constructor should not be used because it hides whether or
// not a socket server will be associated with the thread. Most instances
// of Thread do actually not need one, so please use either of the Create*
// methods to construct an instance of Thread.
explicit Thread(SocketServer* ss);
explicit Thread(std::unique_ptr<SocketServer> ss);
// guarantee Stop() is explicitly called before the subclass is destroyed).
// This is required to avoid a data race between the destructor modifying the
// vtable, and the Thread::PreRun calling the virtual method Run().
~Thread() override;
static std::unique_ptr<Thread> CreateWithSocketServer();
static std::unique_ptr<Thread> Create();
static Thread* Current();
// Used to catch performance regressions. Use this to disallow blocking calls
// (Invoke) for a given scope. If a synchronous call is made while this is in
// effect, an assert will be triggered.
// Note that this is a single threaded class.
class ScopedDisallowBlockingCalls {
Thread* const thread_;
const bool previous_state_;
bool IsCurrent() const;
// Sleeps the calling thread for the specified number of milliseconds, during
// which time no processing is performed. Returns false if sleeping was
// interrupted by a signal (POSIX only).
static bool SleepMs(int millis);
// Sets the thread's name, for debugging. Must be called before Start().
// If |obj| is non-null, its value is appended to |name|.
const std::string& name() const { return name_; }
bool SetName(const std::string& name, const void* obj);
// Starts the execution of the thread.
bool Start(Runnable* runnable = nullptr);
// Tells the thread to stop and waits until it is joined.
// Never call Stop on the current thread. Instead use the inherited Quit
// function which will exit the base MessageQueue without terminating the
// underlying OS thread.
virtual void Stop();
// By default, Thread::Run() calls ProcessMessages(kForever). To do other
// work, override Run(). To receive and dispatch messages, call
// ProcessMessages occasionally.
virtual void Run();
virtual void Send(const Location& posted_from,
MessageHandler* phandler,
uint32_t id = 0,
MessageData* pdata = nullptr);
// Convenience method to invoke a functor on another thread. Caller must
// provide the |ReturnT| template argument, which cannot (easily) be deduced.
// Uses Send() internally, which blocks the current thread until execution
// is complete.
// Ex: bool result = thread.Invoke<bool>(RTC_FROM_HERE,
// &MyFunctionReturningBool);
// NOTE: This function can only be called when synchronous calls are allowed.
// See ScopedDisallowBlockingCalls for details.
template <class ReturnT, class FunctorT>
ReturnT Invoke(const Location& posted_from, const FunctorT& functor) {
FunctorMessageHandler<ReturnT, FunctorT> handler(functor);
InvokeInternal(posted_from, &handler);
return handler.MoveResult();
// From MessageQueue
void Clear(MessageHandler* phandler,
uint32_t id = MQID_ANY,
MessageList* removed = nullptr) override;
void ReceiveSends() override;
// ProcessMessages will process I/O and dispatch messages until:
// 1) cms milliseconds have elapsed (returns true)
// 2) Stop() is called (returns false)
bool ProcessMessages(int cms);
// Returns true if this is a thread that we created using the standard
// constructor, false if it was created by a call to
// ThreadManager::WrapCurrentThread(). The main thread of an application
// is generally not owned, since the OS representation of the thread
// obviously exists before we can get to it.
// You cannot call Start on non-owned threads.
bool IsOwned();
#if defined(WEBRTC_WIN)
HANDLE GetHandle() const {
return thread_;
DWORD GetId() const {
return thread_id_;
#elif defined(WEBRTC_POSIX)
pthread_t GetPThread() {
return thread_;
// Expose private method running() for tests.
// DANGER: this is a terrible public API. Most callers that might want to
// call this likely do not have enough control/knowledge of the Thread in
// question to guarantee that the returned value remains true for the duration
// of whatever code is conditionally executing because of the return value!
bool RunningForTest() { return running(); }
// Sets the per-thread allow-blocking-calls flag and returns the previous
// value. Must be called on this thread.
bool SetAllowBlockingCalls(bool allow);
// These functions are public to avoid injecting test hooks. Don't call them
// outside of tests.
// This method should be called when thread is created using non standard
// method, like derived implementation of rtc::Thread and it can not be
// started by calling Start(). This will set started flag to true and
// owned to false. This must be called from the current thread.
bool WrapCurrent();
void UnwrapCurrent();
// Same as WrapCurrent except that it never fails as it does not try to
// acquire the synchronization access of the thread. The caller should never
// call Stop() or Join() on this thread.
void SafeWrapCurrent();
// Blocks the calling thread until this thread has terminated.
void Join();
static void AssertBlockingIsAllowedOnCurrentThread();
friend class ScopedDisallowBlockingCalls;
struct ThreadInit {
Thread* thread;
Runnable* runnable;
#if defined(WEBRTC_WIN)
static DWORD WINAPI PreRun(LPVOID context);
static void *PreRun(void *pv);
// ThreadManager calls this instead WrapCurrent() because
// ThreadManager::Instance() cannot be used while ThreadManager is
// being created.
// The method tries to get synchronization rights of the thread on Windows if
// |need_synchronize_access| is true.
bool WrapCurrentWithThreadManager(ThreadManager* thread_manager,
bool need_synchronize_access);
// Return true if the thread was started and hasn't yet stopped.
bool running() { return running_.Wait(0); }
// Processes received "Send" requests. If |source| is not null, only requests
// from |source| are processed, otherwise, all requests are processed.
void ReceiveSendsFromThread(const Thread* source);
// If |source| is not null, pops the first "Send" message from |source| in
// |sendlist_|, otherwise, pops the first "Send" message of |sendlist_|.
// The caller must lock |crit_| before calling.
// Returns true if there is such a message.
bool PopSendMessageFromThread(const Thread* source, _SendMessage* msg);
void InvokeInternal(const Location& posted_from, MessageHandler* handler);
std::list<_SendMessage> sendlist_;
std::string name_;
Event running_; // Signalled means running.
#if defined(WEBRTC_POSIX)
pthread_t thread_;
#if defined(WEBRTC_WIN)
HANDLE thread_;
DWORD thread_id_;
bool owned_;
bool blocking_calls_allowed_; // By default set to |true|.
friend class ThreadManager;
// AutoThread automatically installs itself at construction
// uninstalls at destruction, if a Thread object is
// _not already_ associated with the current OS thread.
class AutoThread : public Thread {
~AutoThread() override;
// AutoSocketServerThread automatically installs itself at
// construction and uninstalls at destruction. If a Thread object is
// already associated with the current OS thread, it is temporarily
// disassociated and restored by the destructor.
class AutoSocketServerThread : public Thread {
explicit AutoSocketServerThread(SocketServer* ss);
~AutoSocketServerThread() override;
rtc::Thread* old_thread_;
} // namespace rtc