boost asio 学习 定时器
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http://www.gamedev.net/blog/950/entry-2249317-a-guide-to-getting-
started-with-boostasio?pg=7
6 定时器
boost::asio 提供了一个 deadline_timer class来提供同步与异步的接口。
BOOST文档提供了一组优秀示例。
第一个例子,将创建一个间隔5秒的定时器。
#include <boost/asio.hpp> #include <boost/shared_ptr.hpp> #include <boost/thread.hpp> #include <boost/thread/mutex.hpp> #include <boost/bind.hpp> #include <iostream> boost::mutex global_stream_lock; void WorkerThread(boost::shared_ptr< boost::asio::io_service > io_service) { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Thread Start" << std::endl; global_stream_lock.unlock(); while (true) { try { boost::system::error_code ec; io_service->run(ec); if (ec) { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Error: " << ec << std::endl; global_stream_lock.unlock(); } break; } catch (std::exception & ex) { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Exception: " << ex.what() << std::endl; global_stream_lock.unlock(); } } global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Thread Finish" << std::endl; global_stream_lock.unlock(); } void TimerHandler(const boost::system::error_code & error) { if (error) { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Error: " << error << std::endl; global_stream_lock.unlock(); } else { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] TimerHandler " << std::endl; global_stream_lock.unlock(); } } int main(int argc, char * argv[]) { boost::shared_ptr< boost::asio::io_service > io_service( new boost::asio::io_service ); boost::shared_ptr< boost::asio::io_service::work > work( new boost::asio::io_service::work(*io_service) ); global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Press [return] to exit." << std::endl; global_stream_lock.unlock(); boost::thread_group worker_threads; for (int x = 0; x < 2; ++x) { worker_threads.create_thread(boost::bind (&WorkerThread, io_service)); } boost::asio::deadline_timer timer(*io_service); timer.expires_from_now(boost::posix_time::seconds(5)); timer.async_wait(TimerHandler); std::cin.get(); io_service->stop(); worker_threads.join_all(); return 0; }
如果我们想创建一个可冲用的定时器.我们将定时器对象设置为全局,但是可能
导致共享对象不是线程安全的。boost::bind能解决这个问题。使用定时器对象
的shared_ptr指针,我们能使用bind并且传递定时器到指定的handler,保持定
时器可重用。
#include <boost/asio.hpp> #include <boost/shared_ptr.hpp> #include <boost/thread.hpp> #include <boost/thread/mutex.hpp> #include <boost/bind.hpp> #include <iostream> boost::mutex global_stream_lock; void WorkerThread(boost::shared_ptr< boost::asio::io_service > io_service) { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Thread Start" << std::endl; global_stream_lock.unlock(); while (true) { try { boost::system::error_code ec; io_service->run(ec); if (ec) { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Error: " << ec << std::endl; global_stream_lock.unlock(); } break; } catch (std::exception & ex) { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Exception: " << ex.what() << std::endl; global_stream_lock.unlock(); } } global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Thread Finish" << std::endl; global_stream_lock.unlock(); } void TimerHandler( const boost::system::error_code & error, boost::shared_ptr< boost::asio::deadline_timer > timer ) { if (error) { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Error: " << error << std::endl; global_stream_lock.unlock(); } else { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] TimerHandler " << std::endl; global_stream_lock.unlock(); timer->expires_from_now(boost::posix_time::seconds (5)); timer->async_wait(boost::bind(&TimerHandler, _1, timer)); } } int main(int argc, char * argv[]) { boost::shared_ptr< boost::asio::io_service > io_service( new boost::asio::io_service ); boost::shared_ptr< boost::asio::io_service::work > work( new boost::asio::io_service::work(*io_service) ); global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Press [return] to exit." << std::endl; global_stream_lock.unlock(); boost::thread_group worker_threads; for (int x = 0; x < 2; ++x) { worker_threads.create_thread(boost::bind (&WorkerThread, io_service)); } boost::shared_ptr< boost::asio::deadline_timer > timer( new boost::asio::deadline_timer(*io_service) ); timer->expires_from_now(boost::posix_time::seconds(5)); timer->async_wait(boost::bind(&TimerHandler, _1, timer)); std::cin.get(); io_service->stop(); worker_threads.join_all(); return 0; }
使用bind可以做许多有趣的事情,_1参数是一个占位符。因为TimerHandler 函
数需要一个参数用于回调,我们需要引用这个bind调用。_1意味着第一个参数,
我们稍后提供。
运行上面例子,我们将获得一个每五秒激活一次的定时器。
如果想保证定时器不和work处理器同时运行,我们可以使用strand。
代码如下
#include <boost/asio.hpp> #include <boost/shared_ptr.hpp> #include <boost/thread.hpp> #include <boost/thread/mutex.hpp> #include <boost/bind.hpp> #include <iostream> boost::mutex global_stream_lock; void WorkerThread(boost::shared_ptr< boost::asio::io_service > io_service) { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Thread Start" << std::endl; global_stream_lock.unlock(); while (true) { try { boost::system::error_code ec; io_service->run(ec); if (ec) { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Error: " << ec << std::endl; global_stream_lock.unlock(); } break; } catch (std::exception & ex) { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Exception: " << ex.what() << std::endl; global_stream_lock.unlock(); } } global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Thread Finish" << std::endl; global_stream_lock.unlock(); } void TimerHandler( const boost::system::error_code & error, boost::shared_ptr< boost::asio::deadline_timer > timer, boost::shared_ptr< boost::asio::io_service::strand > strand ) { if (error) { global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Error: " << error << std::endl; global_stream_lock.unlock(); } else { std::cout << "[" << boost::this_thread::get_id() << "] TimerHandler " << std::endl; timer->expires_from_now(boost::posix_time::seconds(1)); timer->async_wait( strand->wrap(boost::bind(&TimerHandler, _1, timer, strand)) ); } } void PrintNum(int x) { std::cout << "[" << boost::this_thread::get_id() << "] x: " << x << std::endl; boost::this_thread::sleep(boost::posix_time::milliseconds(1000)); } int main(int argc, char * argv[]) { boost::shared_ptr< boost::asio::io_service > io_service( new boost::asio::io_service ); boost::shared_ptr< boost::asio::io_service::work > work( new boost::asio::io_service::work(*io_service) ); boost::shared_ptr< boost::asio::io_service::strand > strand( new boost::asio::io_service::strand(*io_service) ); global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Press [return] to exit." << std::endl; global_stream_lock.unlock(); boost::thread_group worker_threads; for (int x = 0; x < 2; ++x) { worker_threads.create_thread(boost::bind(&WorkerThread, io_service)); } boost::this_thread::sleep(boost::posix_time::seconds(1)); strand->post(boost::bind(&PrintNum, 1)); strand->post(boost::bind(&PrintNum, 2)); strand->post(boost::bind(&PrintNum, 3)); strand->post(boost::bind(&PrintNum, 4)); strand->post(boost::bind(&PrintNum, 5)); boost::shared_ptr< boost::asio::deadline_timer > timer( new boost::asio::deadline_timer(*io_service) ); timer->expires_from_now(boost::posix_time::seconds(1)); timer->async_wait( strand->wrap(boost::bind(&TimerHandler, _1, timer, strand)) ); std::cin.get(); io_service->stop(); worker_threads.join_all(); return 0; }
我们需要使用strand封装定时器处理器,strand能确保工作对象先运行而后定时器线程后运行。
本章节我们学习如何使用bind strand shard_ptr来获取灵活性和实现功能。在后面的网络系统中我们将使用这些组件。
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