WebRTC学习之八：函数的异步执行

WebRTC在asyncinvoker.h和asyncivoker.cpp中实现了函数的异步履行。asyncinvoker.h的注释中给出了1个小例子，本文的学习就是从这个例子开始的。但是这个例子和单元测试代码都只演示了如何让1个函数在子线程中履行，以下所示。

myclass.h

#include "webrtc/base/asyncinvoker.h"
#include <iostream>
#include <memory>

class MyClass 
{

public:
	MyClass();
	void OneTask(rtc::Thread *thread,int x);

	void AnotherAsyncTask(int x);
	
private:
	std::unique_ptr<rtc::AsyncInvoker> invoker;
};

#include "myclass.h"
MyClass::MyClass()
{
	invoker.reset(new rtc::AsyncInvoker());
	std::cout << "Main Thread ID:" << rtc::Thread::Current()->GetId() << std::endl;
}

void MyClass::OneTask(rtc::Thread *thread,int x)
{
	invoker->AsyncInvoke<void>(RTC_FROM_HERE,thread,rtc::Bind(&MyClass::AnotherAsyncTask,(MyClass*)this,x));
}
void MyClass::AnotherAsyncTask(int x)
{
	std::cout << "Worker Thread ID:" << rtc::Thread::Current()->GetId() << std::endl;
	std::cout << "Input Value Is:" << x << std::endl;
}

#include "myclass.h"
int main()
{
	std::unique_ptr<rtc::Thread> myThread = rtc::Thread::Create();
	myThread->Start();
	MyClass *myClass = new MyClass;
	myClass->OneTask(myThread.get(),10);

	Sleep(10000);

    return 0;
}

打印结果

从上图输出的线程ID可以看出，函数AnotherAsyncTask是在子线程中履行的。

但是如何在子线程中调用1个函数，并让该函数中主线程中履行呢，可以将上述代码稍作更改，以下所示。

myclass.h

#include "webrtc/base/asyncinvoker.h"
#include <iostream>
#include <memory>

class MyClass 
{

public:
	MyClass();
	void OneTask(rtc::Thread *thread,int x);

	void AnotherAsyncTask(int x);
	
	void myFunction(int x);
	
private:
	std::unique_ptr<rtc::AsyncInvoker> invoker;
	rtc::Thread *mainThread;
};

#include "myclass.h"
MyClass::MyClass()
{
	invoker.reset(new rtc::AsyncInvoker());
	std::cout << "Main Thread ID:" << rtc::Thread::Current()->GetId() << std::endl;
	mainThread = rtc::Thread::Current();
}

void MyClass::OneTask(rtc::Thread *thread,x));
}
void MyClass::AnotherAsyncTask(int x)
{
	std::cout << "Worker Thread ID:" << rtc::Thread::Current()->GetId() << std::endl;
	std::cout << "Input Value Is:" << x << std::endl;

	invoker->AsyncInvoke<void>(RTC_FROM_HERE,mainThread,rtc::Bind(&MyClass::myFunction,x));
}

void MyClass::myFunction(int x)
{
	std::cout << "myFunction Thread ID:" << rtc::Thread::Current()->GetId() << std::endl;
	std::cout << "myFunction Value Is:" << x << std::endl;
}

#include "myclass.h"
int main()
{
	std::unique_ptr<rtc::Thread> myThread = rtc::Thread::Create();
	myThread->Start();
	MyClass *myClass = new MyClass;
	myClass->OneTask(myThread.get(),10);
	
	Sleep(10000);

    return 0;
}

这里需要将main.cpp稍作修改，添加代码实现线程的消息循环，新的main.cpp以下所示。

#include "myclass.h"
int main()
{
	std::unique_ptr<rtc::Thread> myThread = rtc::Thread::Create();
	myThread->Start();
	MyClass *myClass = new MyClass;
	myClass->OneTask(myThread.get(),10);
	
	while (true)
	{
		rtc::Thread::Current()->ProcessMessages(0);
		rtc::Thread::Current()->SleepMs(1);
	}

    return 0;
}

从上图输出的线程ID可以看出，函数myFunction是在主线程中履行的。

（编辑：李大同）

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