• What is SObjectizer?
• What distinguishes SObjectizer?
  • SObjectizer is not like TBB, taskflow or HPX
• Show me the code!
  • HelloWorld example
  • Ping-Pong example
  • Pub/Sub example
  • BlinkingLed example
  • CSP-like Ping-Pong example
  • Another CSP-example with Golang's like select() statement
  • Want to know more?
• There are more useful stuff in a companion project so5extra
• Limitations
• Obtaining and building
  • SObjectizer-5.8 requires Cpp-17!
  • Building via Mxx_ru
  • Building via CMake
  • Building for Android
    • Building with Android NDK
    • Building with CrystaX NDK
  • Using C Dependency Managers
    • Using via vcpkg
    • Using via Conan
      • Installing SObjectizer And Adding It To conanfile.txt
      • Adding SObjectizer To Your CMakeLists.txt
• License

Created by gh-md-toc

What is SObjectizer?

SObjectizer is one of a few cross-platform and OpenSource "actor frameworks" for C++. But SObjectizer supports not only Actor Model, but also Publish-Subscribe Model and CSP-like channels. The goal of SObjectizer is significant simplification of development of concurrent and multithreaded applications in C++.

SObjectizer allows the creation of a concurrent app as a set of agent-objects which interact with each other through asynchronous messages. It handles message dispatching and provides a working context for message processing. And allows to tune those things by supplying various ready-to-use dispatchers.

What distinguishes SObjectizer?

Maturity. SObjectizer is based on ideas that have been put forward in 1995-2000. And SObjectizer itself is being developed since 2002. SObjectizer-5 is continuously evolved since 2010.

Stability. From the very beginning SObjectizer was used for business-critical applications, and some of them are still being used in production. Breaking changes in SObjectizer are rare and we approach to them very carefully.

Cross-platform. SObjectizer runs on Windows, Linux, FreeBSD, macOS and Android.

Easy-to-use. SObjectizer provides easy to understand and easy to use API with a lot of examples in the SObjectizer's distributive and a plenty of information in the project's Wiki.

Free. SObjectizer is distributed under BSD-3-CLAUSE license, so it can be used in development of proprietary commercial software for free.

SObjectizer is not like TBB, taskflow or HPX

SObjectizer is often compared with tools like Intel Threading Building Blocks, taskflow, HPX, and similar to them. Such comparison is just useless.

All those tools are intended to be used for solving tasks from Parallel Computing area: they allow to reduce the computational time by utilizing several CPU cores. For example, you can reencode your video file from one format to another within one hour on one CPU core, by it takes only 15 minutes on four cores. That is the main goal of Parallel Computing.

SObjectizer is intended for a slightly different area: Concurrent Computing. The main goal of SObjectizer is the simplification of doing many different tasks at once. Sometimes there is no need to use more than just one CPU core for that. But if there are several CPU cores, then SObjectizer makes the handling of those tasks and the interaction between them much easier.

The tricky part is the fact that Parallel- and Concurrent Computing use the same concurrency mechanisms and primitives (like threads, mutexes, atomics, and so on) under the hood. But from the high-level point of view Parallel- and Concurrent Computing are used for very different tasks.

As examples of applications that were or could be implemented on top of SObjectizer, we can list multithreaded proxy-server, automatic control system, MQ-broker, database server, and so on.

Show me the code!

HelloWorld example

This is a classical example "Hello, World" expressed by using SObjectizer's agents:

#include <so_5/all.hpp>

class hello_actor final : public so_5::agent_t {
public:
   using so_5::agent_t::agent_t;

   void so_evt_start() override {
      std::cout << "Hello, World!" << std::endl;
      // Finish work of example.
      so_deregister_agent_coop_normally();
   }
};

int main() {
   // Launch SObjectizer.
   so_5::launch([](so_5::environment_t & env) {
         // Add a hello_actor instance in a new cooperation.
         env.register_agent_as_coop( env.make_agent<hello_actor>() );
      });

   return 0;
}

Ping-Pong example

Let's look at more interesting example with two agents and message exchange between them. It is another famous example for actor frameworks, "Ping-Pong":

#include <so_5/all.hpp>

struct ping {
   int counter_;
};

struct pong {
   int counter_;
};

class pinger final : public so_5::agent_t {
   so_5::mbox_t ponger_;

   void on_pong(mhood_t<pong> cmd) {
      if(cmd->counter_ > 0)
         so_5::send<ping>(ponger_, cmd->counter_ - 1);
      else
         so_deregister_agent_coop_normally();
   }

public:
   pinger(context_t ctx) : so_5::agent_t{std::move(ctx)} {}

   void set_ponger(const so_5::mbox_t mbox) { ponger_ = mbox; }

   void so_define_agent() override {
      so_subscribe_self().event( &pinger::on_pong );
   }

   void so_evt_start() override {
      so_5::send<ping>(ponger_, 1000);
   }
};

class ponger final : public so_5::agent_t {
   const so_5::mbox_t pinger_;
   int pings_received_{};

public:
   ponger(context_t ctx, so_5::mbox_t pinger)
      :  so_5::agent_t{std::move(ctx)}
      ,  pinger_{std::move(pinger)}
   {}

   void so_define_agent() override {
      so_subscribe_self().event(
         [this](mhood_t<ping> cmd) {
            ++pings_received_;
            so_5::send<pong>(pinger_, cmd->counter_);
         });
   }

   void so_evt_finish() override {
      std::cout << "pings received: " << pings_received_ << std::endl;
   }
};

int main() {
   so_5::launch([](so_5::environment_t & env) {
         env.introduce_coop([](so_5::coop_t & coop) {
               auto pinger_actor = coop.make_agent<pinger>();
               auto ponger_actor = coop.make_agent<ponger>(
                     pinger_actor->so_direct_mbox());

               pinger_actor->set_ponger(ponger_actor->so_direct_mbox());
            });
      });

   return 0;
}

All agents in the code above are working on the same work thread. How to bind them to different work threads?

It is very simple. Just use an appropriate dispatcher:

int main() {
   so_5::launch([](so_5::environment_t & env) {
         env.introduce_coop(
            so_5::disp::active_obj::make_dispatcher(env).binder(),
            [](so_5::coop_t & coop) {
               auto pinger_actor = coop.make_agent<pinger>();
               auto ponger_actor = coop.make_agent<ponger>(
                     pinger_actor->so_direct_mbox());

               pinger_actor->set_ponger(ponger_actor->so_direct_mbox());
            });
      });

   return 0;
}

Pub/Sub example

SObjectizer supports Pub/Sub model via multi-producer/multi-consumer message boxes. A message sent to that message box will be received by all subscribers of that message type:

#include <so_5/all.hpp>

using namespace std::literals;

struct acquired_value {
   std::chrono::steady_clock::time_point acquired_at_;
   int value_;
};

class producer final : public so_5::agent_t {
   const so_5::mbox_t board_;
   so_5::timer_id_t timer_;
   int counter_{};

   struct acquisition_time final : public so_5::signal_t {};

   void on_timer(mhood_t<acquisition_time>) {
      // Publish the next value for all consumers.
      so_5::send<acquired_value>(
            board_, std::chrono::steady_clock::now(), ++counter_);
   }

public:
   producer(context_t ctx, so_5::mbox_t board)
      :  so_5::agent_t{std::move(ctx)}
      ,  board_{std::move(board)}
   {}

   void so_define_agent() override {
      so_subscribe_self().event(&producer::on_timer);
   }

   void so_evt_start() override {
      // Agent will periodically recive acquisition_time signal
      // without initial delay and with period of 750ms.
      timer_ = so_5::send_periodic<acquisition_time>(*this, 0ms, 750ms);
   }
};

class consumer final : public so_5::agent_t {
   const so_5::mbox_t board_;
   const std::string name_;

   void on_value(mhood_t<acquired_value> cmd) {
      std::cout << name_ << ": " << cmd->value_ << std::endl;
   }

public:
   consumer(context_t ctx, so_5::mbox_t board, std::string name)
      :  so_5::agent_t{std::move(ctx)}
      ,  board_{std::move(board)}
      ,  name_{std::move(name)}
   {}

   void so_define_agent() override {
      so_subscribe(board_).event(&consumer::on_value);
   }
};

int main() {
   so_5::launch([](so_5::environment_t & env) {
         auto board = env.create_mbox();
         env.introduce_coop([board](so_5::coop_t & coop) {
               coop.make_agent<producer>(board);
               coop.make_agent<consumer>(board, "first"s);
               coop.make_agent<consumer>(board, "second"s);
            });

         std::this_thread::sleep_for(std::chrono::seconds(4));
         env.stop();
      });

   return 0;
}

BlinkingLed example

All agents in SObjectizer are finite-state machines. Almost all functionality of hierarchical finite-states machines (HSM) are supported: child states and handlers inheritance, on_enter/on_exit handlers, state timeouts, deep- and shallow state history, except orthogonal states.

Let's see how an agent that implements the following statechart can look like:

This is a very simple example that demonstrates an agent for the statechart shown above:

#include <so_5/all.hpp>

using namespace std::literals;

class blinking_led final : public so_5::agent_t {
   state_t off{ this }, blinking{ this },
      blink_on{ initial_substate_of{ blinking } },
      blink_off{ substate_of{ blinking } };

public :
   struct turn_on_off : public so_5::signal_t {};

   blinking_led(context_t ctx) : so_5::agent_t{std::move(ctx)} {
      this >>= off;

      off.just_switch_to<turn_on_off>(blinking);

      blinking.just_switch_to<turn_on_off>(off);

      blink_on
         .on_enter([]{ std::cout << "ON" << std::endl; })
         .on_exit([]{ std::cout << "off" << std::endl; })
         .time_limit(1250ms, blink_off);

      blink_off
         .time_limit(750ms, blink_on);
   }
};

int main()
{
   so_5::launch([](so_5::environment_t & env) {
      so_5::mbox_t m;
      env.introduce_coop([&](so_5::coop_t & coop) {
            auto led = coop.make_agent< blinking_led >();
            m = led->so_direct_mbox();
         });

      const auto pause = [](auto duration) {
         std::this_thread::sleep_for(duration);
      };

      std::cout << "Turn blinking on for 10s" << std::endl;
      so_5::send<blinking_led::turn_on_off>(m);
      pause(10s);

      std::cout << "Turn blinking off for 5s" << std::endl;
      so_5::send<blinking_led::turn_on_off>(m);
      pause(5s);

      std::cout << "Turn blinking on for 5s" << std::endl;
      so_5::send<blinking_led::turn_on_off>(m);
      pause(5s);

      std::cout << "Stopping..." << std::endl;
      env.stop();
   } );

   return 0;
}

CSP-like Ping-Pong example

SObjectizer allows to write concurrent applications even without agents inside. Only plain threads and CSP-like channels can be used.

This is plain-thread implementation of Ping-Pong example (please note that main() is not exception-safe):

#include <so_5/all.hpp>

struct ping {
   int counter_;
};

struct pong {
   int counter_;
};

void pinger_proc(so_5::mchain_t self_ch, so_5::mchain_t ping_ch) {
   so_5::send<ping>(ping_ch, 1000);

   // Read all message until channel will be closed.
   so_5::receive( so_5::from(self_ch).handle_all(),
      [&](so_5::mhood_t<pong> cmd) {
         if(cmd->counter_ > 0)
            so_5::send<ping>(ping_ch, cmd->counter_ - 1);
         else {
            // Channels have to be closed to break `receive` calls.
            so_5::close_drop_content(so_5::exceptions_enabled, self_ch);
            so_5::close_drop_content(so_5::exceptions_enabled, ping_ch);
         }
      });
}

void ponger_proc(so_5::mchain_t self_ch, so_5::mchain_t pong_ch) {
   int pings_received{};

   // Read all message until channel will be closed.
   so_5::receive( so_5::from(self_ch).handle_all(),
      [&](so_5::mhood_t<ping> cmd) {
         ++pings_received;
         so_5::send<pong>(pong_ch, cmd->counter_);
      });

   std::cout << "pings received: " << pings_received << std::endl;
}

int main() {
   so_5::wrapped_env_t sobj;

   auto pinger_ch = so_5::create_mchain(sobj);
   auto ponger_ch = so_5::create_mchain(sobj);

   std::thread pinger{pinger_proc, pinger_ch, ponger_ch};
   std::thread ponger{ponger_proc, ponger_ch, pinger_ch};

   ponger.join();
   pinger.join();

   return 0;
}

Another CSP-example with Golang's like select() statement

SObjectizer provides a select() function that is similar to Golang's select statement. This function allows waiting for incoming messages from several message chains. It also allows to wait for the readiness of message chains for accepting a new outg