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// Copyright (C) 2013 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 serial scheduler.
#ifndef BOOST_THREAD_SERIAL_EXECUTOR_HPP
#define BOOST_THREAD_SERIAL_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/thread/executors/generic_executor_ref.hpp>
#include <boost/thread/future.hpp>
#include <boost/thread/scoped_thread.hpp>
#include <boost/config/abi_prefix.hpp>
namespace boost
{
namespace executors
{
class serial_executor
{
public:
/// type-erasure to store the works to do
typedef executors::work work;
private:
typedef scoped_thread<> thread_t;
/// the thread safe work queue
sync_queue<work > work_queue;
generic_executor_ref ex;
thread_t thr;
struct try_executing_one_task {
work& task;
boost::promise<void> &p;
try_executing_one_task(work& task, boost::promise<void> &p)
: task(task), p(p) {}
void operator()() {
task(); // if task() throws promise is not set but as the the program terminates and should terminate there is no need to use try-catch here.
p.set_value();
}
};
public:
/**
* \par Returns
* The underlying executor wrapped on a generic executor reference.
*/
generic_executor_ref underlying_executor() BOOST_NOEXCEPT { return ex; }
/**
* 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)
{
boost::promise<void> p;
try_executing_one_task tmp(task,p);
ex.submit(tmp);
// ex.submit([&task, &p]()
// {
// task(); // if task() throws promise is not set but as the the program terminates and should terminate there is no need to use try-catch here.
// p.set_value();
// });
p.get_future().wait();
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:
/// serial_executor is not copyable.
BOOST_THREAD_NO_COPYABLE(serial_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.
*/
template <class Executor>
serial_executor(Executor& ex)
: ex(ex), thr(&serial_executor::worker_thread, this)
{
}
/**
* \b Effects: Destroys the thread pool.
*
* \b Synchronization: The completion of all the closures happen before the completion of the \c serial_executor destructor.
*/
~serial_executor()
{
// signal to all the worker thread that there will be no more submissions.
close();
}
/**
* \b Effects: close the \c serial_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 serial_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;
}
};
}
using executors::serial_executor;
}
#include <boost/config/abi_suffix.hpp>
#endif
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