Creating a thread pool library in C++.

This blog is a continuation of the previous blog , which showed you how to create a Thread class in c++.

Simple threads implementation in C++.

I was looking for a simple thread library implementation in C++, something like Java's Thread class. I could not find anything ready and easy to use. I have come up with a simple implementation of a Thread class in C++. Please note that I do not claim to have implemented threads, i have just modelled an abstraction called Thread, which can be sub classed by your classes.
POSIX pthreads are used for threading. This library is just a wrapper around it.

I was actually trying to build a ThreadPool library using C++. So, I had to model a Thread Class so that the Thread Pool implementation will be easier (i thought) to conceptualise.

So this is how the Thread class looks like.

#ifndef __VTHREAD_H__
#define __VTHREAD_H__

#include

/* Abstract base class for Thread */

class Thread
{
        public:
                        Thread();
                        int start();
                        virtual void execute()=0;
        private:
                        static void *threadExecFunc(void *pData);
                        pthread_t mThreadId;
};
#endif

As it appears from the code, this is an abstract class which is sub-classed by other classes which want to run as a thread. All sub-classes will implement void execute() ,  to get their work done in a thread. 

Following is the implementation of the Thread class:
 

#include
#include
#include

using namespace std;

Thread::Thread()
{
}

int Thread::start()
{
        int ret = pthread_create(&mThreadId, NULL, threadExecFunc, this);
        return ret;
}

void *Thread::threadExecFunc(void *pData)
{
        Thread *lThread = (Thread *) pData;
        lThread->execute();
        return NULL;
}
 


As you can see, all you have to do is sub-class Thread class and implement the execute() function in the class. Following is an example of how to implement the Thread class in your programs.


class MyThread: public Thread
{
     public:
                    MyThread(/* Get some data to work on */) 
                   {}

                    void execute()
                    {
                            while( bHasWorkToDo == true )
                            {
                                    doSomeWork();
                            }

                    }

}
                 

int main()
{
           Thread *lMyThread  = new MyThread(/* Pass some data to work on */);
            lMyThread->start();
}      

        
 
First, I create an instance of MyThread and then i call start() on the object. 
This results in MyThread::execute() being executed.  Note that all the calls to the pthread library have been encapsulated within the Thread class.


There are many features missing though , for example there is no way to join, destroy , yield etc. I have not even thought about how to implement those methods on this Thread class. 


Please take a look at the Java's Thread class here to get an idea of what else can be added to this class here -  http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Thread.html