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+// Copyright (C) 2013,2014 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)
+//
+// 2013/11 Vicente J. Botet Escriba
+// first implementation of a simple user scheduler.
+// 2013/11 Vicente J. Botet Escriba
+// rename loop_executor.
+
+#ifndef BOOST_THREAD_EXECUTORS_LOOP_EXECUTOR_HPP
+#define BOOST_THREAD_EXECUTORS_LOOP_EXECUTOR_HPP
+
+#include <boost/thread/detail/config.hpp>
+#include <boost/thread/detail/delete.hpp>
+#include <boost/thread/detail/move.hpp>
+#include <boost/thread/sync_queue.hpp>
+#include <boost/thread/executors/work.hpp>
+
+#include <boost/config/abi_prefix.hpp>
+
+namespace boost
+{
+namespace executors
+{
+
+ class loop_executor
+ {
+ public:
+ /// type-erasure to store the works to do
+ typedef executors::work work;
+ private:
+ /// the thread safe work queue
+ sync_queue<work > work_queue;
+
+ public:
+ /**
+ * 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()
+ {
+ work task;
+ try
+ {
+ if (work_queue.try_pull_front(task) == queue_op_status::success)
+ {
+ task();
+ return true;
+ }
+ return false;
+ }
+ catch (std::exception& )
+ {
+ return false;
+ }
+ catch (...)
+ {
+ return false;
+ }
+ }
+ private:
+ /**
+ * Effects: schedule one task or yields
+ * Throws: whatever the current task constructor throws or the task() throws.
+ */
+ void schedule_one_or_yield()
+ {
+ if ( ! try_executing_one())
+ {
+ this_thread::yield();
+ }
+ }
+
+
+ /**
+ * The main loop of the worker thread
+ */
+ void worker_thread()
+ {
+ while (!closed())
+ {
+ schedule_one_or_yield();
+ }
+ while (try_executing_one())
+ {
+ }
+ }
+
+ public:
+ /// loop_executor is not copyable.
+ BOOST_THREAD_NO_COPYABLE(loop_executor)
+
+ /**
+ * \b Effects: creates a thread pool that runs closures using one of its closure-executing methods.
+ *
+ * \b Throws: Whatever exception is thrown while initializing the needed resources.
+ */
+ loop_executor()
+ {
+ }
+ /**
+ * \b Effects: Destroys the thread pool.
+ *
+ * \b Synchronization: The completion of all the closures happen before the completion of the \c loop_executor destructor.
+ */
+ ~loop_executor()
+ {
+ // signal to all the worker thread that there will be no more submissions.
+ close();
+ }
+
+ /**
+ * loop
+ */
+ void loop() { worker_thread(); }
+ /**
+ * \b Effects: close the \c loop_executor for submissions.
+ * The loop will work until there is no more closures to run.
+ */
+ void close()
+ {
+ work_queue.close();
+ }
+
+ /**
+ * \b Returns: whether the pool is closed for submissions.
+ */
+ bool closed()
+ {
+ return work_queue.closed();
+ }
+
+ /**
+ * \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 loop_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)
+ {
+ work_queue.push_back(work(closure));
+ }
+#endif
+ void submit(void (*closure)())
+ {
+ work_queue.push_back(work(closure));
+ }
+
+ template <typename Closure>
+ void submit(BOOST_THREAD_RV_REF(Closure) closure)
+ {
+ work_queue.push_back(work(boost::forward<Closure>(closure)));
+ }
+
+ /**
+ * \b Requires: This must be called from an scheduled task.
+ *
+ * \b Effects: reschedule functions until pred()
+ */
+ template <typename Pred>
+ bool reschedule_until(Pred const& pred)
+ {
+ do {
+ if ( ! try_executing_one())
+ {
+ return false;
+ }
+ } while (! pred());
+ return true;
+ }
+
+ /**
+ * run queued closures
+ */
+ void run_queued_closures()
+ {
+ sync_queue<work>::underlying_queue_type q = work_queue.underlying_queue();
+ while (! q.empty())
+ {
+ work& task = q.front();
+ task();
+ q.pop_front();
+ }
+ }
+
+ };
+}
+using executors::loop_executor;
+
+}
+
+#include <boost/config/abi_suffix.hpp>
+
+#endif