• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 252
  • Last Modified:

making thread body as member function

In C++ how to create a thread, whose thread body is member function (not static ) of the
class, so that when class object is created, that particular thread should
access only its member variables, which may be the case with as many class
objects created.
0
havman56
Asked:
havman56
1 Solution
 
MichaelSCommented:
I am afraid you can't do it. What is the problem with static functions?
0
 
KangaRooCommented:
struct A
{
   void Realwork();
   static void Run(void*)
}

void A::Run(void* parm)
{
   reinterpret_cast<A*>(parm)->Realwork();
}

A object;
makethread(&A::Run, reinterpret_cast<void*>(&A))
0
 
MichaelSCommented:
>KangaRoo
Actually the question is how to do it without "static"
0
Cloud Class® Course: Amazon Web Services - Basic

Are you thinking about creating an Amazon Web Services account for your business? Not sure where to start? In this course you’ll get an overview of the history of AWS and take a tour of their user interface.

 
KangaRooCommented:
make-thread functions generally tke parameters of the form

make_thread(FuncPtrType, void*)
and possible a few others. The function pointer type is usually a C funtion, like void (*FuncPtrType)(void*) or int (*FuncPtrType)(void*). There is no way to fit a non-static funtion pointer into this.
But we can use a static meber and the obvious thing to do is pass the object as the void*. The static can then cast the void* parameter back into an object.

For safety you might consider making the static thread function private and provide a public interface:

class A
{
     void Realwork();
     static void Run(void*)
  public:
     void RunThreaded();
}
void A::Run(void* parm)
{
  reinterpret_cast<A*>(parm)->Realwork();
}

void A::RunThreaded()
{
   makethread(&A::Run, reinterpret_cast<void*>(this));
}

A object;
object.RunThreaded();
0
 
KangaRooCommented:
And that is without statics, well, not in the interface. The use of a static member is now a hidden implementation detail :)
0
 
makerpCommented:
void __cdecl run_thread(void *p)
{
  Class *c = (Class*)p;
  p->run();
  delete r;
}

class Class
{
  void run()
  {
     printf("RUN");
  }
};


the latter on

Class *c = new Class
_beginthread(run_thread,0,(void*)c);

this would/should work on windows compilers
0
 
AssafLavieCommented:
Consider the following more object oriented approach:

1. Define an interface for performing thread actions:

struct Action
{
     virtual void operator() = 0;
     virtual void ~Action() { };
};

2. Define a general thread creating function and ThreadProc which invoke a functor:

HANDLE CreateThreadObject(Action* pAction)
{
     return CreateThread(0, 0, GeneralThreadProc, pAction, 0, 0);
};
static void GeneralThreadProc(void * prm)
{
     reinterpret_cast<Action*>(prm)->();
};

3. Each time you want to do some task in another thread simply derive from Action:
struct SomeWorkerAction : public Action
{
     void operator()
     {
          MessageBox(0, "This is done on another thread", 0, 0);
          delete this;
     };
};

-- or --

struct SomeWorkerActionWithParams : public Action
{
     string data_;
     SomeWorkerActionWithParams(const string& data) : data_(data) { };
     void operator()
     {
          MessageBox(0, "This is done on another thread", data_.c_str(), 0);
          delete this;
     };
};

And spawn a thread to run it:
     CreateThreadObject(new SomeWorkerAction);
     CreateThreadObject(new SomeWorkerActionWithParams("use this param"));

This approach is a lot nicer. It's easier to pass parameters to the thread and it's also easier to use when implementing more complicated MT applications. (For instance, you can store a queue of Action* and invoke them from a pool of threads.)

btw, the code is just a thought. I didn't compile it or anything so don't be suprised if it has errors. I *do* happen to have a private Thread Pool library which uses a similar idiom.
0
 
xutaoCommented:
I think this is what exactly you want:
http://www.codeproject.com/useritems/callback_adapter.asp

Almost a perfect solution.
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Featured Post

Cloud Class® Course: C++ 11 Fundamentals

This course will introduce you to C++ 11 and teach you about syntax fundamentals.

Tackle projects and never again get stuck behind a technical roadblock.
Join Now