boost asio 学习(五) 错误处理

http://www.gamedev.net/blog/950/entry-2249317-a-guide-to-getting-started-with-boostasio?pg=6

5. Error handling

接下来我们需要注意的话题是错误处理。换句话说就是函数抛出异常时发生了什么

Boost::asio 给予用户两种选择来处理。错误通过handler传播，指出线程呼叫run或者poll系列函数的位置。用户可以能处理通过异常抛出的状态或者是接收返回的错误变量。更多关于BOOST的信息，可以参考boost 的错误与异常处理。

首先我们看看异常处理错误的方法

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#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();       try     {         io_service->run();     }     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 RaiseAnException( boost::shared_ptr< boost::asio::io_service > io_service ) {     global_stream_lock.lock();     std::cout << "[" << boost::this_thread::get_id()         << "] " << __FUNCTION__ << std::endl;     global_stream_lock.unlock();       io_service->post( boost::bind( &RaiseAnException, io_service ) );       throw( std::runtime_error( "Oops!" ) ); }   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()         << "] The program will exit when all work has finished." << 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 ) );     }       io_service->post( boost::bind( &RaiseAnException, io_service ) );       worker_threads.join_all();       return 0; }

　　

这个例子里，因为异常通过run函数释放，work线程因此退出。所有线程退出后，程序由于join_all的返回而结束。

下面看看使用错误变量返回异常的例子

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#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();       boost::system::error_code ec;     io_service->run( ec );       if( ec )     {         global_stream_lock.lock();         std::cout << "[" << boost::this_thread::get_id()             << "] Exception: " << ec << 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 RaiseAnException( boost::shared_ptr< boost::asio::io_service > io_service ) {     global_stream_lock.lock();     std::cout << "[" << boost::this_thread::get_id()         << "] " << __FUNCTION__ << std::endl;     global_stream_lock.unlock();       io_service->post( boost::bind( &RaiseAnException, io_service ) );       throw( std::runtime_error( "Oops!" ) ); }   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()         << "] The program will exit when all work has finished." << 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 ) );     }       io_service->post( boost::bind( &RaiseAnException, io_service ) );       worker_threads.join_all();       return 0; }

　　

上面这个代码将引起程序崩溃。通过调试，我们可以发现抛出的异常没有被处理

正确处理如下

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#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 RaiseAnException(boost::shared_ptr< boost::asio::io_service > io_service) {     global_stream_lock.lock();     std::cout << "[" << boost::this_thread::get_id()         << "] " << __FUNCTION__ << std::endl;     global_stream_lock.unlock();           io_service->post(boost::bind(&RaiseAnException, io_service));     throw(std::runtime_error("Oops!"));       }   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()         << "] The program will exit when all work has finished." << 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));     }       io_service->post(boost::bind(&RaiseAnException, io_service));       worker_threads.join_all();       return 0; }