_flow_graph_async_msg_impl.h

/*
    Copyright 2005-2016 Intel Corporation.  All Rights Reserved.

    This file is part of Threading Building Blocks. Threading Building Blocks is free software;
    you can redistribute it and/or modify it under the terms of the GNU General Public License
    version 2  as  published  by  the  Free Software Foundation.  Threading Building Blocks is
    distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the
    implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
    See  the GNU General Public License for more details.   You should have received a copy of
    the  GNU General Public License along with Threading Building Blocks; if not, write to the
    Free Software Foundation, Inc.,  51 Franklin St,  Fifth Floor,  Boston,  MA 02110-1301 USA

    As a special exception,  you may use this file  as part of a free software library without
    restriction.  Specifically,  if other files instantiate templates  or use macros or inline
    functions from this file, or you compile this file and link it with other files to produce
    an executable,  this file does not by itself cause the resulting executable to be covered
    by the GNU General Public License. This exception does not however invalidate any other
    reasons why the executable file might be covered by the GNU General Public License.
*/

#ifndef __TBB__flow_graph_async_msg_impl_H
#define __TBB__flow_graph_async_msg_impl_H

#ifndef __TBB_flow_graph_H
#error Do not #include this internal file directly; use public TBB headers instead.
#endif

// included in namespace tbb::flow::interfaceX (in flow_graph.h)

template< typename T > class async_msg;

namespace internal {

template< typename T, typename = void >
struct async_helpers {
    typedef async_msg<T> async_type;
    typedef T filtered_type;

    static const bool is_async_type = false;

    static const void* to_void_ptr(const T& t) {
        return static_cast<const void*>(&t);
    }

    static void* to_void_ptr(T& t) {
        return static_cast<void*>(&t);
    }

    static const T& from_void_ptr(const void* p) {
        return *static_cast<const T*>(p);
    }

    static T& from_void_ptr(void* p) {
        return *static_cast<T*>(p);
    }

    static task* try_put_task_wrapper_impl( receiver<T>* const this_recv, const void *p, bool is_async ) {
        if ( is_async ) {
            // This (T) is NOT async and incoming 'A<X> t' IS async
            // Get data from async_msg
            const async_msg<filtered_type>& msg = async_helpers< async_msg<filtered_type> >::from_void_ptr(p);
            task* const new_task = msg.my_storage->subscribe(*this_recv);
            // finalize() must be called after subscribe() because set() can be called in finalize()
            // and 'this_recv' client must be subscribed by this moment
            msg.finalize();
            return new_task;
        } else {
            // Incoming 't' is NOT async
            return this_recv->try_put_task( from_void_ptr(p) );
        }
    }
};

template< typename T >
struct async_helpers< T, typename std::enable_if< std::is_base_of<async_msg<typename T::async_msg_data_type>, T>::value >::type > {
    typedef T async_type;
    typedef typename T::async_msg_data_type filtered_type;

    static const bool is_async_type = true;

    // Receiver-classes use const interfaces
    static const void* to_void_ptr(const T& t) {
        return static_cast<const void*>( &static_cast<const async_msg<filtered_type>&>(t) );
    }

    static void* to_void_ptr(T& t) {
        return static_cast<void*>( &static_cast<async_msg<filtered_type>&>(t) );
    }

    // Sender-classes use non-const interfaces
    static const T& from_void_ptr(const void* p) {
        return *static_cast<const T*>( static_cast<const async_msg<filtered_type>*>(p) );
    }

    static T& from_void_ptr(void* p) {
        return *static_cast<T*>( static_cast<async_msg<filtered_type>*>(p) );
    }

    // Used in receiver<T> class
    static task* try_put_task_wrapper_impl(receiver<T>* const this_recv, const void *p, bool is_async) {
        if ( is_async ) {
            // Both are async
            return this_recv->try_put_task( from_void_ptr(p) );
        } else {
            // This (T) is async and incoming 'X t' is NOT async
            // Create async_msg for X
            const filtered_type& t = async_helpers<filtered_type>::from_void_ptr(p);
            const T msg(t);
            return this_recv->try_put_task(msg);
        }
    }
};

template <typename T>
class async_storage {
public:
    typedef receiver<T> async_storage_client;

    async_storage() { my_data_ready.store<tbb::relaxed>(false); }

    template<typename C>
    async_storage(C&& data) : my_data( std::forward<C>(data) ) {
        using namespace tbb::internal;
        __TBB_STATIC_ASSERT( (is_same_type<typename strip<C>::type, typename strip<T>::type>::value), "incoming type must be T" );

        my_data_ready.store<tbb::relaxed>(true);
    }

    template<typename C>
    bool set(C&& data) {
        using namespace tbb::internal;
        __TBB_STATIC_ASSERT( (is_same_type<typename strip<C>::type, typename strip<T>::type>::value), "incoming type must be T" );

        {
            tbb::spin_mutex::scoped_lock locker(my_mutex);

            if (my_data_ready.load<tbb::relaxed>()) {
                __TBB_ASSERT(false, "double set() call");
                return false;
            }

            my_data = std::forward<C>(data);
            my_data_ready.store<tbb::release>(true);
        }

        // Thread sync is on my_data_ready flag
        for (typename subscriber_list_type::iterator it = my_clients.begin(); it != my_clients.end(); ++it) {
            (*it)->try_put(my_data);
        }

        return true;
    }

    task* subscribe(async_storage_client& client) {
        if (! my_data_ready.load<tbb::acquire>())
        {
            tbb::spin_mutex::scoped_lock locker(my_mutex);

            if (! my_data_ready.load<tbb::relaxed>()) {
#if TBB_USE_ASSERT
                for (typename subscriber_list_type::iterator it = my_clients.begin(); it != my_clients.end(); ++it) {
                    __TBB_ASSERT(*it != &client, "unexpected double subscription");
                }
#endif // TBB_USE_ASSERT

                // Subscribe
                my_clients.push_back(&client);
                return SUCCESSFULLY_ENQUEUED;
            }
        }

        __TBB_ASSERT(my_data_ready.load<tbb::relaxed>(), "data is NOT ready");
        return client.try_put_task(my_data);
    }

private:
    tbb::spin_mutex my_mutex;

    tbb::atomic<bool> my_data_ready;
    T my_data;

    typedef std::vector<async_storage_client*> subscriber_list_type;
    subscriber_list_type my_clients;
};

} // namespace internal

template <typename T>
class async_msg {
    template< typename > friend class receiver;
    template< typename, typename > friend struct internal::async_helpers;
public:
    typedef T async_msg_data_type;

    async_msg() : my_storage(std::make_shared< internal::async_storage<T> >()) {}

    async_msg(const T& t) : my_storage(std::make_shared< internal::async_storage<T> >(t)) {}

    async_msg(T&& t) : my_storage(std::make_shared< internal::async_storage<T> >( std::move(t) )) {}

    virtual ~async_msg() {}

    void set(const T& t) {
        my_storage->set(t);
    }

    void set(T&& t) {
        my_storage->set( std::move(t) );
    }

protected:
    // Can be overridden in derived class to inform that 
    // async calculation chain is over
    virtual void finalize() const {}

private:
    typedef std::shared_ptr< internal::async_storage<T> > async_storage_ptr;
    async_storage_ptr my_storage;
};

#endif  // __TBB__flow_graph_async_msg_impl_H