335 lines
10 KiB
C
335 lines
10 KiB
C
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/*
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* Copyright 2004 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef WEBRTC_BASE_THREAD_H_
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#define WEBRTC_BASE_THREAD_H_
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#include <algorithm>
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#include <list>
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#include <memory>
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#include <string>
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#include <vector>
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#if defined(WEBRTC_POSIX)
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#include <pthread.h>
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#endif
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#include "webrtc/base/constructormagic.h"
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#include "webrtc/base/event.h"
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#include "webrtc/base/messagequeue.h"
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#if defined(WEBRTC_WIN)
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#include "webrtc/base/win32.h"
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#endif
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namespace rtc {
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class Thread;
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class ThreadManager {
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public:
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static const int kForever = -1;
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ThreadManager();
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~ThreadManager();
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static ThreadManager* Instance();
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Thread* CurrentThread();
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void SetCurrentThread(Thread* thread);
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// Returns a thread object with its thread_ ivar set
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// to whatever the OS uses to represent the thread.
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// If there already *is* a Thread object corresponding to this thread,
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// this method will return that. Otherwise it creates a new Thread
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// object whose wrapped() method will return true, and whose
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// handle will, on Win32, be opened with only synchronization privileges -
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// if you need more privilegs, rather than changing this method, please
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// write additional code to adjust the privileges, or call a different
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// factory method of your own devising, because this one gets used in
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// unexpected contexts (like inside browser plugins) and it would be a
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// shame to break it. It is also conceivable on Win32 that we won't even
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// be able to get synchronization privileges, in which case the result
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// will have a NULL handle.
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Thread *WrapCurrentThread();
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void UnwrapCurrentThread();
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private:
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#if defined(WEBRTC_POSIX)
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pthread_key_t key_;
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#endif
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#if defined(WEBRTC_WIN)
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DWORD key_;
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#endif
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RTC_DISALLOW_COPY_AND_ASSIGN(ThreadManager);
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};
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struct _SendMessage {
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_SendMessage() {}
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Thread *thread;
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Message msg;
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bool *ready;
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};
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class Runnable {
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public:
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virtual ~Runnable() {}
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virtual void Run(Thread* thread) = 0;
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protected:
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Runnable() {}
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private:
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RTC_DISALLOW_COPY_AND_ASSIGN(Runnable);
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};
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// WARNING! SUBCLASSES MUST CALL Stop() IN THEIR DESTRUCTORS! See ~Thread().
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class LOCKABLE Thread : public MessageQueue {
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public:
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// Create a new Thread and optionally assign it to the passed SocketServer.
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Thread();
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explicit Thread(SocketServer* ss);
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explicit Thread(std::unique_ptr<SocketServer> ss);
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// NOTE: ALL SUBCLASSES OF Thread MUST CALL Stop() IN THEIR DESTRUCTORS (or
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// guarantee Stop() is explicitly called before the subclass is destroyed).
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// This is required to avoid a data race between the destructor modifying the
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// vtable, and the Thread::PreRun calling the virtual method Run().
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~Thread() override;
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static std::unique_ptr<Thread> CreateWithSocketServer();
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static std::unique_ptr<Thread> Create();
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static Thread* Current();
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// Used to catch performance regressions. Use this to disallow blocking calls
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// (Invoke) for a given scope. If a synchronous call is made while this is in
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// effect, an assert will be triggered.
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// Note that this is a single threaded class.
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class ScopedDisallowBlockingCalls {
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public:
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ScopedDisallowBlockingCalls();
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~ScopedDisallowBlockingCalls();
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private:
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Thread* const thread_;
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const bool previous_state_;
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};
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bool IsCurrent() const {
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return Current() == this;
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}
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// Sleeps the calling thread for the specified number of milliseconds, during
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// which time no processing is performed. Returns false if sleeping was
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// interrupted by a signal (POSIX only).
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static bool SleepMs(int millis);
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// Sets the thread's name, for debugging. Must be called before Start().
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// If |obj| is non-NULL, its value is appended to |name|.
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const std::string& name() const { return name_; }
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bool SetName(const std::string& name, const void* obj);
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// Starts the execution of the thread.
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bool Start(Runnable* runnable = NULL);
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// Tells the thread to stop and waits until it is joined.
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// Never call Stop on the current thread. Instead use the inherited Quit
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// function which will exit the base MessageQueue without terminating the
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// underlying OS thread.
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virtual void Stop();
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// By default, Thread::Run() calls ProcessMessages(kForever). To do other
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// work, override Run(). To receive and dispatch messages, call
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// ProcessMessages occasionally.
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virtual void Run();
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virtual void Send(const Location& posted_from,
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MessageHandler* phandler,
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uint32_t id = 0,
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MessageData* pdata = NULL);
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// Convenience method to invoke a functor on another thread. Caller must
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// provide the |ReturnT| template argument, which cannot (easily) be deduced.
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// Uses Send() internally, which blocks the current thread until execution
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// is complete.
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// Ex: bool result = thread.Invoke<bool>(RTC_FROM_HERE,
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// &MyFunctionReturningBool);
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// NOTE: This function can only be called when synchronous calls are allowed.
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// See ScopedDisallowBlockingCalls for details.
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template <class ReturnT, class FunctorT>
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ReturnT Invoke(const Location& posted_from, const FunctorT& functor) {
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FunctorMessageHandler<ReturnT, FunctorT> handler(functor);
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InvokeInternal(posted_from, &handler);
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return handler.result();
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}
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// From MessageQueue
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void Clear(MessageHandler* phandler,
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uint32_t id = MQID_ANY,
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MessageList* removed = NULL) override;
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void ReceiveSends() override;
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// ProcessMessages will process I/O and dispatch messages until:
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// 1) cms milliseconds have elapsed (returns true)
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// 2) Stop() is called (returns false)
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bool ProcessMessages(int cms);
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// Returns true if this is a thread that we created using the standard
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// constructor, false if it was created by a call to
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// ThreadManager::WrapCurrentThread(). The main thread of an application
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// is generally not owned, since the OS representation of the thread
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// obviously exists before we can get to it.
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// You cannot call Start on non-owned threads.
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bool IsOwned();
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#if defined(WEBRTC_WIN)
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HANDLE GetHandle() const {
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return thread_;
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}
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DWORD GetId() const {
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return thread_id_;
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}
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#elif defined(WEBRTC_POSIX)
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pthread_t GetPThread() {
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return thread_;
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}
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#endif
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// Expose private method running() for tests.
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//
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// DANGER: this is a terrible public API. Most callers that might want to
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// call this likely do not have enough control/knowledge of the Thread in
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// question to guarantee that the returned value remains true for the duration
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// of whatever code is conditionally executing because of the return value!
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bool RunningForTest() { return running(); }
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// Sets the per-thread allow-blocking-calls flag and returns the previous
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// value. Must be called on this thread.
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bool SetAllowBlockingCalls(bool allow);
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// These functions are public to avoid injecting test hooks. Don't call them
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// outside of tests.
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// This method should be called when thread is created using non standard
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// method, like derived implementation of rtc::Thread and it can not be
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// started by calling Start(). This will set started flag to true and
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// owned to false. This must be called from the current thread.
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bool WrapCurrent();
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void UnwrapCurrent();
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protected:
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// Same as WrapCurrent except that it never fails as it does not try to
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// acquire the synchronization access of the thread. The caller should never
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// call Stop() or Join() on this thread.
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void SafeWrapCurrent();
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// Blocks the calling thread until this thread has terminated.
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void Join();
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static void AssertBlockingIsAllowedOnCurrentThread();
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friend class ScopedDisallowBlockingCalls;
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private:
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static void *PreRun(void *pv);
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// ThreadManager calls this instead WrapCurrent() because
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// ThreadManager::Instance() cannot be used while ThreadManager is
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// being created.
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// The method tries to get synchronization rights of the thread on Windows if
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// |need_synchronize_access| is true.
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bool WrapCurrentWithThreadManager(ThreadManager* thread_manager,
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bool need_synchronize_access);
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// Return true if the thread was started and hasn't yet stopped.
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bool running() { return running_.Wait(0); }
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// Processes received "Send" requests. If |source| is not NULL, only requests
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// from |source| are processed, otherwise, all requests are processed.
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void ReceiveSendsFromThread(const Thread* source);
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// If |source| is not NULL, pops the first "Send" message from |source| in
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// |sendlist_|, otherwise, pops the first "Send" message of |sendlist_|.
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// The caller must lock |crit_| before calling.
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// Returns true if there is such a message.
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bool PopSendMessageFromThread(const Thread* source, _SendMessage* msg);
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void InvokeInternal(const Location& posted_from, MessageHandler* handler);
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std::list<_SendMessage> sendlist_;
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std::string name_;
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Event running_; // Signalled means running.
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#if defined(WEBRTC_POSIX)
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pthread_t thread_;
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#endif
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#if defined(WEBRTC_WIN)
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HANDLE thread_;
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DWORD thread_id_;
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#endif
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bool owned_;
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bool blocking_calls_allowed_; // By default set to |true|.
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friend class ThreadManager;
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RTC_DISALLOW_COPY_AND_ASSIGN(Thread);
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};
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// AutoThread automatically installs itself at construction
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// uninstalls at destruction, if a Thread object is
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// _not already_ associated with the current OS thread.
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class AutoThread : public Thread {
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public:
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AutoThread();
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~AutoThread() override;
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private:
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RTC_DISALLOW_COPY_AND_ASSIGN(AutoThread);
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};
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// Win32 extension for threads that need to use COM
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#if defined(WEBRTC_WIN)
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class ComThread : public Thread {
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public:
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ComThread() {}
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~ComThread() override { Stop(); }
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protected:
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void Run() override;
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private:
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RTC_DISALLOW_COPY_AND_ASSIGN(ComThread);
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};
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#endif
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// Provides an easy way to install/uninstall a socketserver on a thread.
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class SocketServerScope {
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public:
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explicit SocketServerScope(SocketServer* ss) {
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old_ss_ = Thread::Current()->socketserver();
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Thread::Current()->set_socketserver(ss);
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}
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~SocketServerScope() {
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Thread::Current()->set_socketserver(old_ss_);
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}
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private:
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SocketServer* old_ss_;
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RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(SocketServerScope);
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};
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} // namespace rtc
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#endif // WEBRTC_BASE_THREAD_H_
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