io_service_pool.hpp

#pragma once
#include <boost/asio.hpp>
#include <vector>
#include <boost/noncopyable.hpp>
#include <boost/shared_ptr.hpp>
#include <stdexcept>
#include <boost/thread/thread.hpp>
#include <boost/bind.hpp>
#include <boost/shared_ptr.hpp>

/// A pool of io_service objects.
class io_service_pool
	: private boost::noncopyable
{
public:
	explicit io_service_pool(std::size_t pool_size) : next_io_service_(0)
	{
		if (pool_size == 0)
			throw std::runtime_error("io_service_pool size is 0");

		for (std::size_t i = 0; i < pool_size; ++i)
		{
			io_service_ptr io_service(new boost::asio::io_service);
			work_ptr work(new boost::asio::io_service::work(*io_service));
			io_services_.push_back(io_service);
			work_.push_back(work);
		}
	}

	~io_service_pool()
	{
		stop();
	}

	void run()
	{
		std::vector<boost::shared_ptr<boost::thread> > threads;
		for (std::size_t i = 0; i < io_services_.size(); ++i)
		{
			boost::shared_ptr<boost::thread> thread(new boost::thread(
				boost::bind(&boost::asio::io_service::run, io_services_[i])));
			threads.push_back(thread);
		}

		for (std::size_t i = 0; i < threads.size(); ++i)
			threads[i]->join();
	}

	void stop()
	{
		for (std::size_t i = 0; i < io_services_.size(); ++i)
			io_services_[i]->stop();
	}

	boost::asio::io_service& get_io_service()
	{
		boost::asio::io_service& io_service = *io_services_[next_io_service_];
		++next_io_service_;
		if (next_io_service_ == io_services_.size())
			next_io_service_ = 0;
		return io_service;
	}

private:
	typedef boost::shared_ptr<boost::asio::io_service> io_service_ptr;
	typedef boost::shared_ptr<boost::asio::io_service::work> work_ptr;

	/// The pool of io_services.
	std::vector<io_service_ptr> io_services_;

	/// The work that keeps the io_services running.
	std::vector<work_ptr> work_;

	/// The next io_service to use for a connection.
	std::size_t next_io_service_;
};