How can I set up two objects to communicate with each other asynchronously?

[vincegata]

Hello,

Here is what I've got so far:

// build: 
// clang++ -g -std=c++11 -Wall main.cpp -o main
// main.cpp
#include <iostream>
#include <thread>
#include <vector>

void pt_ssleep(const int delay);

class ioes
{
public:
      virtual void on_data(int i) = 0;
      virtual void from_oes(int i) = 0;
};

class oes : public ioes
{
public:
      oes() {}
      void on_data(int i) override;
      void from_oes(int i) override { }
};

void oes::on_data(int i)
{
      std::cout << i << std::endl;
}

class oms
{
public:
      oms() = delete;
      oms(ioes& param) : ioesobj(param) {}
      void send_data(int i);

private:
      ioes& ioesobj;
      std::vector<int> numbers;
};

void oms::send_data(int i)
{
      numbers.push_back(i);
      auto j = rand();
      ioesobj.on_data(j);
}

int main()
{
      std::cout << " --- start prototype --- " << std::endl;

      oes oesobj;
      oms omsobj(oesobj);

      for (int i=0; ; ++i)
      {
            omsobj.send_data(i);
            pt_ssleep(1);
      }

      std::cout << " --- end prototype --- " << std::endl;
      return 0;
}

void pt_ssleep(const int delay)
{
      std::this_thread::sleep_for(std::chrono::seconds(delay));
}

I need oes object to send some data back to oms object asynchronously and to insert those data into numbers container.

Can someone help me with this. Thank you.

[JLBorges]

class ioes
{
public:
      virtual int on_data(int i) = 0;
      virtual void from_oes(int i) = 0;
};

#include <iostream>

class oes : public ioes
{
public:
      oes() {}
      int on_data(int i) override;
      void from_oes(int ) override { }
};

int oes::on_data(int i)
{
      std::cout << "from oes::on_data: " << (i + 100) << '\n' << std::flush;
      return i*i ;
}

class oms
{
public:
      oms() = delete;
      oms(ioes& param) : ioesobj(param) {}
      int send_data(int i);

private:
      ioes& ioesobj;
};

int oms::send_data(int i)
{
      return ioesobj.on_data(i);
}

#include <iostream>
#include <thread>
#include <future>
#include <functional>

void pt_ssleep(const int delay);

int main()
{
      std::cout << " --- start prototype --- " << std::endl;

      oes oesobj;
      oms omsobj(oesobj);

      for( int i = 0 ; i < 5 ; ++i )
      {
          std::cout << i << ". sending data aynchronously\n" << std::flush ;
          
          // http://en.cppreference.com/w/cpp/thread/async
          auto future = std::async( std::launch::async, &oms::send_data, std::addressof(omsobj), i+23 ) ;
          // omsobj.send_data(99);
          
          std::cout << "waiting for async operation to complete\n" << std::flush ;
          pt_ssleep(1);
          
          future.wait() ; // http://en.cppreference.com/w/cpp/thread/future/wait
          
          // http://en.cppreference.com/w/cpp/thread/future/get
          std::cout << "done. result: " << future.get() << "\n.................\n" << std::flush ;
      }
      std::cout << " --- end prototype --- " << std::endl;
}

void pt_ssleep(const int delay)
{
      std::this_thread::sleep_for(std::chrono::seconds(delay));
}

http://coliru.stacked-crooked.com/a/dd62d4b48318dcfc

[vincegata]

Thanks JLBorges, it looks like I should start reading on C++11 threading.

I should have been more clear on what I mean by "asynchronous" but when I call oms::send_data() I do not need to get the return value from that function (those data are actually being sent into a socket).

I updated my original post and example. oms object updates it's numbers container and sends data to oes. There should be a mechanism for oes to send data back to oms and insert those data into numbers container.

Can you help with this one -- thank you.

[JLBorges]

> it looks like I should start reading on C++11 threading.
> Can you help with this one

Code examples would help only after you have read up on C++ concurrency.
'C++ Concurrency In Action: Practical Multithreading' by Anthony Williams is a good resource.
http://www.amazon.com/C-Concurrency-Action-Practical-Multithreading/dp/1933988770

#include <iostream>
#include <vector>
#include <thread>
#include <mutex>
#include <memory>

struct ioes
{
    virtual ~ioes() = default ;
    virtual void on_data( int i ) = 0;
    virtual void from_oes( int i ) = 0;
};

std::mutex stdout_lock ;

struct cms
{
    explicit cms( ioes& oes_object ) : oes_object(oes_object) {}

    void send_data( int i )
    {
          sent_numbers.push_back(i);
          oes_object.on_data(i);
    }

    void recv_data( int i )
    {
        std::lock_guard<std::mutex> body_guard(lock) ;
        recd_numbers.push_back(i) ;
    }

    void print() const
    {
        std::cout << "sent data: " ;
        for( int v : sent_numbers ) std::cout << v << ' ' ;
        std::cout << '\n' ;

        std::cout << "recd data: " ;
        {
            std::lock_guard<std::mutex> body_guard(lock) ;
            for( int v : recd_numbers ) std::cout << v << ' ' ;
        }
        std::cout << '\n' ;
    }

    private:
        ioes& oes_object ;
        std::vector<int> sent_numbers ;
        std::vector<int> recd_numbers ;
        mutable std::mutex lock ;
};

struct oes : ioes
{
    void connect( cms* p ) { cms_object = p ; }

    void on_data( int i ) override
    {
         std::this_thread::sleep_for( std::chrono::milliseconds(100) );
         {
             std::lock_guard<std::mutex> body_guard(stdout_lock) ;
             std::cout << "oes::on_data(" << i << ")\n" << std::flush ;
         }

         from_oes( 1000 - i*i ) ;
    }

    void from_oes( int i ) override { if(cms_object) cms_object->recv_data(i) ; }

    private:
        cms* cms_object = nullptr ;
};

int main()
{
    oes oes_object ;
    cms cms_object(oes_object) ;
    auto pcms = std::addressof(cms_object) ;
    oes_object.connect(pcms) ;

    for( int i = 0 ; i < 10 ; ++i )
        std::thread( &cms::send_data, pcms, i + 10 ).detach() ;

    std::this_thread::sleep_for( std::chrono::seconds(3) );
    cms_object.print() ;
}

http://coliru.stacked-crooked.com/a/bff2e2f19f4ec3e7 (-stdlib=libc++)

[vincegata]

Thanks a lot! I sure need the reading to understand the code and adapt it.