boost asio 学习(二)了解boost::bind
2.了解boost::bind
使用boost::bind封装一个函数,考虑以下例子
示例2a
#include <iostream> #include <boost/bind.hpp> void F1() { std::cout << __FUNCTION__ << std::endl; } int main( int argc, char * argv[] ) { boost::bind( &F1 ); return 0; }
运行代码无输出,这是因为我们创建一个函数触发对象,但是没有实际调用。我们需要使用()操作符调用函数.
示例2b
#include <iostream> #include <boost/bind.hpp> void F1() { std::cout << __FUNCTION__ << std::endl; } int main( int argc, char * argv[] ) { boost::bind( &F1 )(); return 0; }
现在运行示例,将输出文本。下面示例介绍如何传输参数
示例2C
#include <iostream> #include <boost/bind.hpp> void F2( int i, float f ) { std::cout << "i: " << i << std::endl; std::cout << "f: " << f << std::endl; } int main( int argc, char * argv[] ) { boost::bind( &F2, 42, 3.14f )(); return 0; }
运行程序将输出预期的文本。
下个示例显示bind类成员函数
示例2d
#include <iostream> #include <boost/bind.hpp> class MyClass { public: void F3( int i, float f ) { std::cout << "i: " << i << std::endl; std::cout << "f: " << f << std::endl; } }; int main( int argc, char * argv[] ) { MyClass c; boost::bind( &MyClass::F3, &c, 42, 3.14f )(); return 0; }
我们必须传递类对象的地址以便调用。如果是在类内部调用,则调用this指针或者shared_from_this().
在多线程中,io_service作为全局对象。在实际应用中,这种做法是不推荐的。如果我们尝试应用bind io_service对象,则会发生错误,因为io_service不能被拷贝,所以我们需要使用
shred_ptr.
示例2e
#include <boost/asio.hpp> #include <boost/shared_ptr.hpp> #include <boost/thread.hpp> #include <boost/bind.hpp> #include <iostream> void WorkerThread( boost::shared_ptr< boost::asio::io_service > io_service ) { std::cout << "Thread Start\n"; io_service->run(); std::cout << "Thread Finish\n"; } 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 ) ); std::cout << "Press [return] to exit." << std::endl; boost::thread_group worker_threads; for( int x = 0; x < 4; ++x ) { worker_threads.create_thread( boost::bind( &WorkerThread, io_service ) ); } std::cin.get(); io_service->stop(); worker_threads.join_all(); return 0; }
异步程序中,需要确认全局和共享数据的同步访问。下列示例示范了mutex对象的使用方法。
示例2f
#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(); io_service->run(); global_stream_lock.lock(); std::cout << "[" << boost::this_thread::get_id() << "] Thread Finish" << 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 < 4; ++x ) { worker_threads.create_thread( boost::bind( &WorkerThread, io_service ) ); } std::cin.get(); io_service->stop(); worker_threads.join_all(); return 0; }
此类mutex对象不可递归锁定。如果递归锁定将造成死锁。
作 者: itdef
欢迎转帖 请保持文本完整并注明出处
技术博客 http://www.cnblogs.com/itdef/
B站算法视频题解
https://space.bilibili.com/18508846
qq 151435887
gitee https://gitee.com/def/
欢迎c c++ 算法爱好者 windows驱动爱好者 服务器程序员沟通交流
如果觉得不错,欢迎点赞,你的鼓励就是我的动力
欢迎转帖 请保持文本完整并注明出处
技术博客 http://www.cnblogs.com/itdef/
B站算法视频题解
https://space.bilibili.com/18508846
qq 151435887
gitee https://gitee.com/def/
欢迎c c++ 算法爱好者 windows驱动爱好者 服务器程序员沟通交流
如果觉得不错,欢迎点赞,你的鼓励就是我的动力