text: // Copyright (C) 2014 Vicente J. Botet Escriba
  //
  //  Distributed under the Boost Software License, Version 1.0. (See accompanying
  //  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  //
  // 2014/01 Vicente J. Botet Escriba
  //    first implementation of a thread_executor.
  
  #ifndef BOOST_THREAD_THREAD_EXECUTOR_HPP
  #define BOOST_THREAD_THREAD_EXECUTOR_HPP
  
  #include <boost/thread/detail/config.hpp>
  #if defined BOOST_THREAD_PROVIDES_FUTURE_CONTINUATION && defined BOOST_THREAD_PROVIDES_EXECUTORS && defined BOOST_THREAD_USES_MOVE
  
  #include <boost/throw_exception.hpp>
  #include <boost/thread/detail/delete.hpp>
  #include <boost/thread/detail/move.hpp>
  #include <boost/thread/executors/work.hpp>
  #include <boost/thread/executors/executor.hpp>
  #include <boost/thread/mutex.hpp>
  #include <boost/thread/lock_guard.hpp>
  #include <boost/thread/thread_only.hpp>
  #include <boost/thread/scoped_thread.hpp>
  #include <boost/thread/csbl/vector.hpp>
  #include <boost/thread/concurrent_queues/queue_op_status.hpp>
  
  #include <boost/config/abi_prefix.hpp>
  
  namespace boost
  {
  namespace executors
  {
    class thread_executor
    {
    public:
      /// type-erasure to store the works to do
      typedef  executors::work work;
      bool closed_;
      typedef scoped_thread<> thread_t;
      typedef csbl::vector<thread_t> threads_type;
      threads_type threads_;
      mutable mutex mtx_;
  
      /**
       * Effects: try to execute one task.
       * Returns: whether a task has been executed.
       * Throws: whatever the current task constructor throws or the task() throws.
       */
      bool try_executing_one()
      {
        return false;
      }
  
    public:
      /// thread_executor is not copyable.
      BOOST_THREAD_NO_COPYABLE(thread_executor)
  
      /**
       * \b Effects: creates a inline executor that runs closures immediately.
       *
       * \b Throws: Nothing.
       */
      thread_executor()
      : closed_(false)
      {
      }
      /**
       * \b Effects: Waits for closures (if any) to complete, then joins and destroys the threads.
       *
       * \b Synchronization: The completion of all the closures happen before the completion of the \c thread_executor destructor.
       */
      ~thread_executor()
      {
        // signal to all the worker thread that there will be no more submissions.
        close();
        // all the scoped threads will join before destroying
      }
  
      /**
       * \b Effects: close the \c thread_executor for submissions.
       * The loop will work until there is no more closures to run.
       */
      void close()
      {
        lock_guard<mutex> lk(mtx_);
        closed_ = true;
      }
  
      /**
       * \b Returns: whether the pool is closed for submissions.
       */
      bool closed(lock_guard<mutex>& )
      {
        return closed_;
      }
      bool closed()
      {
        lock_guard<mutex> lk(mtx_);
        return closed(lk);
      }
  
      /**
       * \b Requires: \c Closure is a model of \c Callable(void()) and a model of \c CopyConstructible/MoveConstructible.
       *
       * \b Effects: The specified \c closure will be scheduled for execution at some point in the future.
       * If invoked closure throws an exception the \c thread_executor will call \c std::terminate, as is the case with threads.
       *
       * \b Synchronization: completion of \c closure on a particular thread happens before destruction of thread's thread local variables.
       *
       * \b Throws: \c sync_queue_is_closed if the thread pool is closed.
       * Whatever exception that can be throw while storing the closure.
       */
  
  #if defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
      template <typename Closure>
      void submit(Closure & closure)
      {
        lock_guard<mutex> lk(mtx_);
        if (closed(lk))  BOOST_THROW_EXCEPTION( sync_queue_is_closed() );
        threads_.reserve(threads_.size() + 1);
        thread th(closure);
        threads_.push_back(thread_t(boost::move(th)));
      }
  #endif
      void submit(void (*closure)())
      {
        lock_guard<mutex> lk(mtx_);
        if (closed(lk))  BOOST_THROW_EXCEPTION( sync_queue_is_closed() );
        threads_.reserve(threads_.size() + 1);
        thread th(closure);
        threads_.push_back(thread_t(boost::move(th)));
      }
  
      template <typename Closure>
      void submit(BOOST_THREAD_FWD_REF(Closure) closure)
      {
        lock_guard<mutex> lk(mtx_);
        if (closed(lk))  BOOST_THROW_EXCEPTION( sync_queue_is_closed() );
        threads_.reserve(threads_.size() + 1);
        thread th(boost::forward<Closure>(closure));
        threads_.push_back(thread_t(boost::move(th)));
      }
  
      /**
       * \b Requires: This must be called from an scheduled task.
       *
       * \b Effects: reschedule functions until pred()
       */
      template <typename Pred>
      bool reschedule_until(Pred const&)
      {
        return false;
      }
  
    };
  }
  using executors::thread_executor;
  }
  
  #include <boost/config/abi_suffix.hpp>
  
  #endif
  #endif
  