Chris@102: // Copyright (C) 2013 Vicente J. Botet Escriba
Chris@102: //
Chris@102: //  Distributed under the Boost Software License, Version 1.0. (See accompanying
Chris@102: //  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@102: //
Chris@102: // 2013/11 Vicente J. Botet Escriba
Chris@102: //    first implementation of a simple serial scheduler.
Chris@102: 
Chris@102: #ifndef BOOST_THREAD_SERIAL_EXECUTOR_HPP
Chris@102: #define BOOST_THREAD_SERIAL_EXECUTOR_HPP
Chris@102: 
Chris@102: #include <boost/thread/detail/config.hpp>
Chris@102: #include <boost/thread/detail/delete.hpp>
Chris@102: #include <boost/thread/detail/move.hpp>
Chris@102: #include <boost/thread/concurrent_queues/sync_queue.hpp>
Chris@102: #include <boost/thread/executors/work.hpp>
Chris@102: #include <boost/thread/executors/generic_executor_ref.hpp>
Chris@102: #include <boost/thread/future.hpp>
Chris@102: #include <boost/thread/scoped_thread.hpp>
Chris@102: 
Chris@102: #include <boost/config/abi_prefix.hpp>
Chris@102: 
Chris@102: namespace boost
Chris@102: {
Chris@102: namespace executors
Chris@102: {
Chris@102:   class serial_executor
Chris@102:   {
Chris@102:   public:
Chris@102:     /// type-erasure to store the works to do
Chris@102:     typedef  executors::work work;
Chris@102:   private:
Chris@102:     typedef  scoped_thread<> thread_t;
Chris@102: 
Chris@102:     /// the thread safe work queue
Chris@102:     concurrent::sync_queue<work > work_queue;
Chris@102:     generic_executor_ref ex;
Chris@102:     thread_t thr;
Chris@102: 
Chris@102:     struct try_executing_one_task {
Chris@102:       work& task;
Chris@102:       boost::promise<void> &p;
Chris@102:       try_executing_one_task(work& task, boost::promise<void> &p)
Chris@102:       : task(task), p(p) {}
Chris@102:       void operator()() {
Chris@102:         try {
Chris@102:           task();
Chris@102:           p.set_value();
Chris@102:         } catch (...)
Chris@102:         {
Chris@102:           p.set_exception(current_exception());
Chris@102:         }
Chris@102:       }
Chris@102:     };
Chris@102:   public:
Chris@102:     /**
Chris@102:      * \par Returns
Chris@102:      * The underlying executor wrapped on a generic executor reference.
Chris@102:      */
Chris@102:     generic_executor_ref& underlying_executor() BOOST_NOEXCEPT { return ex; }
Chris@102: 
Chris@102:     /**
Chris@102:      * Effects: try to execute one task.
Chris@102:      * Returns: whether a task has been executed.
Chris@102:      * Throws: whatever the current task constructor throws or the task() throws.
Chris@102:      */
Chris@102:     bool try_executing_one()
Chris@102:     {
Chris@102:       work task;
Chris@102:       try
Chris@102:       {
Chris@102:         if (work_queue.try_pull(task) == queue_op_status::success)
Chris@102:         {
Chris@102:           boost::promise<void> p;
Chris@102:           try_executing_one_task tmp(task,p);
Chris@102:           ex.submit(tmp);
Chris@102:           p.get_future().wait();
Chris@102:           return true;
Chris@102:         }
Chris@102:         return false;
Chris@102:       }
Chris@102:       catch (...)
Chris@102:       {
Chris@102:         std::terminate();
Chris@102:         return false;
Chris@102:       }
Chris@102:     }
Chris@102:   private:
Chris@102:     /**
Chris@102:      * Effects: schedule one task or yields
Chris@102:      * Throws: whatever the current task constructor throws or the task() throws.
Chris@102:      */
Chris@102:     void schedule_one_or_yield()
Chris@102:     {
Chris@102:         if ( ! try_executing_one())
Chris@102:         {
Chris@102:           this_thread::yield();
Chris@102:         }
Chris@102:     }
Chris@102: 
Chris@102:     /**
Chris@102:      * The main loop of the worker thread
Chris@102:      */
Chris@102:     void worker_thread()
Chris@102:     {
Chris@102:       while (!closed())
Chris@102:       {
Chris@102:         schedule_one_or_yield();
Chris@102:       }
Chris@102:       while (try_executing_one())
Chris@102:       {
Chris@102:       }
Chris@102:     }
Chris@102: 
Chris@102:   public:
Chris@102:     /// serial_executor is not copyable.
Chris@102:     BOOST_THREAD_NO_COPYABLE(serial_executor)
Chris@102: 
Chris@102:     /**
Chris@102:      * \b Effects: creates a thread pool that runs closures using one of its closure-executing methods.
Chris@102:      *
Chris@102:      * \b Throws: Whatever exception is thrown while initializing the needed resources.
Chris@102:      */
Chris@102:     template <class Executor>
Chris@102:     serial_executor(Executor& ex)
Chris@102:     : ex(ex), thr(&serial_executor::worker_thread, this)
Chris@102:     {
Chris@102:     }
Chris@102:     /**
Chris@102:      * \b Effects: Destroys the thread pool.
Chris@102:      *
Chris@102:      * \b Synchronization: The completion of all the closures happen before the completion of the \c serial_executor destructor.
Chris@102:      */
Chris@102:     ~serial_executor()
Chris@102:     {
Chris@102:       // signal to the worker thread that there will be no more submissions.
Chris@102:       close();
Chris@102:     }
Chris@102: 
Chris@102:     /**
Chris@102:      * \b Effects: close the \c serial_executor for submissions.
Chris@102:      * The loop will work until there is no more closures to run.
Chris@102:      */
Chris@102:     void close()
Chris@102:     {
Chris@102:       work_queue.close();
Chris@102:     }
Chris@102: 
Chris@102:     /**
Chris@102:      * \b Returns: whether the pool is closed for submissions.
Chris@102:      */
Chris@102:     bool closed()
Chris@102:     {
Chris@102:       return work_queue.closed();
Chris@102:     }
Chris@102: 
Chris@102:     /**
Chris@102:      * \b Requires: \c Closure is a model of \c Callable(void()) and a model of \c CopyConstructible/MoveConstructible.
Chris@102:      *
Chris@102:      * \b Effects: The specified \c closure will be scheduled for execution at some point in the future.
Chris@102:      * If invoked closure throws an exception the \c serial_executor will call \c std::terminate, as is the case with threads.
Chris@102:      *
Chris@102:      * \b Synchronization: completion of \c closure on a particular thread happens before destruction of thread's thread local variables.
Chris@102:      *
Chris@102:      * \b Throws: \c sync_queue_is_closed if the thread pool is closed.
Chris@102:      * Whatever exception that can be throw while storing the closure.
Chris@102:      */
Chris@102: 
Chris@102: #if defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
Chris@102:     template <typename Closure>
Chris@102:     void submit(Closure & closure)
Chris@102:     {
Chris@102:       work_queue.push(work(closure));
Chris@102:     }
Chris@102: #endif
Chris@102:     void submit(void (*closure)())
Chris@102:     {
Chris@102:       work_queue.push(work(closure));
Chris@102:     }
Chris@102: 
Chris@102:     template <typename Closure>
Chris@102:     void submit(BOOST_THREAD_RV_REF(Closure) closure)
Chris@102:     {
Chris@102:       work_queue.push(work(boost::forward<Closure>(closure)));
Chris@102:     }
Chris@102: 
Chris@102:     /**
Chris@102:      * \b Requires: This must be called from an scheduled task.
Chris@102:      *
Chris@102:      * \b Effects: reschedule functions until pred()
Chris@102:      */
Chris@102:     template <typename Pred>
Chris@102:     bool reschedule_until(Pred const& pred)
Chris@102:     {
Chris@102:       do {
Chris@102:         if ( ! try_executing_one())
Chris@102:         {
Chris@102:           return false;
Chris@102:         }
Chris@102:       } while (! pred());
Chris@102:       return true;
Chris@102:     }
Chris@102: 
Chris@102:   };
Chris@102: }
Chris@102: using executors::serial_executor;
Chris@102: }
Chris@102: 
Chris@102: #include <boost/config/abi_suffix.hpp>
Chris@102: 
Chris@102: #endif