无论如何使用，都能感觉到使用boost.asio实现服务器，不仅是一件非常轻松的事，而且代码很漂亮，逻辑也相当清晰，这点上很不同于ACE。
使用io_service作为处理工作的work pool，可以看到，就是通过io_service.post投递一个Handler到io_service的队列,Handler在这个io_service.run内部得到执行，有可能你会发现，io_services.dispatch的接口也和io_service.post一样，但不同的是它是直接调用而不是经过push到队列然后在io_services.run中执行，而在这个示例当中，显然我们需要把工作交到另一个线程去完成，这样才不会影响网络接收线程池的工作以达到高效率的接收数据，这种设计与前面的netsever其实相同，这就是典型的Half Sync/Half Async。二者的区别就是netsever自己实现了工作队列，而不是直接使用io_service，这种设计实际上在win下是使用了iocp作为工作队列。
不过我更倾向于前一种设计，因为那样做，代码一切都在自己的掌握中，而io_service则是经过许多封装代码，并且本身设计只是用于处理网络完成事件的。
无论如何使用，都能感觉到使用boost.asio实现服务器，不仅是一件非常轻松的事，而且代码很漂亮，逻辑也相当清晰，这点上很不同于ACE。
[cpp] view plain copy
- #include <stdio.h>
- #include <cstdlib>
- #include <iostream>
- #include <boost/thread.hpp>
- #include <boost/aligned_storage.hpp>
- #include <boost/array.hpp>
- #include <boost/bind.hpp>
- #include <boost/enable_shared_from_this.hpp>
- #include <boost/noncopyable.hpp>
- #include <boost/shared_ptr.hpp>
- #include <boost/asio.hpp>
- using boost::asio::ip::tcp;
- class handler_allocator
- : private boost::noncopyable
- {
- public:
- handler_allocator()
- : in_use_(false)
- {
- }
- void* allocate(std::size_t size)
- {
- if (!in_use_ && size < storage_.size)
- {
- in_use_ = true;
- return storage_.address();
- }
- else
- {
- return ::operator new(size);
- }
- }
- void deallocate(void* pointer)
- {
- if (pointer == storage_.address())
- {
- in_use_ = false;
- }
- else
- {
- ::operator delete(pointer);
- }
- }
- private:
- // Storage space used for handler-based custom memory allocation.
- boost::aligned_storage<1024> storage_;
- // Whether the handler-based custom allocation storage has been used.
- bool in_use_;
- };
- template <typename Handler>
- class custom_alloc_handler
- {
- public:
- custom_alloc_handler(handler_allocator& a, Handler h)
- : allocator_(a),
- handler_(h)
- {
- }
- template <typename Arg1>
- void operator()(Arg1 arg1)
- {
- handler_(arg1);
- }
- template <typename Arg1, typename Arg2>
- void operator()(Arg1 arg1, Arg2 arg2)
- {
- handler_(arg1, arg2);
- }
- friend void* asio_handler_allocate(std::size_t size,
- custom_alloc_handler<Handler>* this_handler)
- {
- return this_handler->allocator_.allocate(size);
- }
- friend void asio_handler_deallocate(void* pointer, std::size_t /*size*/,
- custom_alloc_handler<Handler>* this_handler)
- {
- this_handler->allocator_.deallocate(pointer);
- }
- private:
- handler_allocator& allocator_;
- Handler handler_;
- };
- // Helper function to wrap a handler object to add custom allocation.
- template <typename Handler>
- inline custom_alloc_handler<Handler> make_custom_alloc_handler(
- handler_allocator& a, Handler h)
- {
- return custom_alloc_handler<Handler>(a, h);
- }
- /// A pool of io_service objects.
- class io_service_pool
- : private boost::noncopyable
- {
- public:
- /// Construct the io_service pool.
- 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");
- // Give all the io_services work to do so that their run() functions will not
- // exit until they are explicitly stopped.
- 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);
- }
- }
- // Run all io_service objects in the pool.
- void run()
- {
- // Create a pool of threads to run all of the io_services.
- 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);
- }
- // Wait for all threads in the pool to exit.
- for (std::size_t i = 0; i < threads.size(); ++i)
- threads[i]->join();
- }
- // Stop all io_service objects in the pool.
- void stop()
- {
- // Explicitly stop all io_services.
- for (std::size_t i = 0; i < io_services_.size(); ++i)
- io_services_[i]->stop();
- }
- // Get an io_service to use.
- boost::asio::io_service& get_io_service()
- {
- // Use a round-robin scheme to choose the next io_service to use.
- 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_;
- };
- class session
- : public boost::enable_shared_from_this<session>
- {
- public:
- session(boost::asio::io_service& work_service
- , boost::asio::io_service& io_service)
- : socket_(io_service)
- , io_work_service(work_service)
- {
- }
- tcp::socket& socket()
- {
- return socket_;
- }
- void start()
- {
- socket_.async_read_some(boost::asio::buffer(data_),
- make_custom_alloc_handler(allocator_,
- boost::bind(&session::handle_read,
- shared_from_this(),
- boost::asio::placeholders::error,
- boost::asio::placeholders::bytes_transferred)));
- }
- void handle_read(const boost::system::error_code& error,
- size_t bytes_transferred)
- {
- if (!error)
- {
- boost::shared_ptr<std::vector<char> > buf(new std::vector<char>);
- buf->resize(bytes_transferred);
- std::copy(data_.begin(), data_.begin() + bytes_transferred, buf->begin());
- io_work_service.post(boost::bind(&session::on_receive
- , shared_from_this(), buf, bytes_transferred));
- socket_.async_read_some(boost::asio::buffer(data_),
- make_custom_alloc_handler(allocator_,
- boost::bind(&session::handle_read,
- shared_from_this(),
- boost::asio::placeholders::error,
- boost::asio::placeholders::bytes_transferred)));
- }
- }
- void handle_write(const boost::system::error_code& error)
- {
- if (!error)
- {
- }
- }
- void on_receive(boost::shared_ptr<std::vector<char> > buffers
- , size_t bytes_transferred)
- {
- char* data_stream = &(*buffers->begin());
- // in here finish the work.
- std::cout << "receive :" << bytes_transferred << " bytes." <<
- "message :" << data_stream << std::endl;
- }
- private:
- // The io_service used to finish the work.
- boost::asio::io_service& io_work_service;
- // The socket used to communicate with the client.
- tcp::socket socket_;
- // Buffer used to store data received from the client.
- boost::array<char, 1024> data_;
- // The allocator to use for handler-based custom memory allocation.
- handler_allocator allocator_;
- };
- typedef boost::shared_ptr<session> session_ptr;
- class server
- {
- public:
- server(short port, std::size_t io_service_pool_size)
- : io_service_pool_(io_service_pool_size)
- , io_service_work_pool_(io_service_pool_size)
- , acceptor_(io_service_pool_.get_io_service(), tcp::endpoint(tcp::v4(), port))
- {
- session_ptr new_session(new session(io_service_work_pool_.get_io_service()
- , io_service_pool_.get_io_service()));
- acceptor_.async_accept(new_session->socket(),
- boost::bind(&server::handle_accept, this, new_session,
- boost::asio::placeholders::error));
- }
- void handle_accept(session_ptr new_session,
- const boost::system::error_code& error)
- {
- if (!error)
- {
- new_session->start();
- new_session.reset(new session(io_service_work_pool_.get_io_service()
- , io_service_pool_.get_io_service()));
- acceptor_.async_accept(new_session->socket(),
- boost::bind(&server::handle_accept, this, new_session,
- boost::asio::placeholders::error));
- }
- }
- void run()
- {
- io_thread_.reset(new boost::thread(boost::bind(&io_service_pool::run
- , &io_service_pool_)));
- work_thread_.reset(new boost::thread(boost::bind(&io_service_pool::run
- , &io_service_work_pool_)));
- }
- void stop()
- {
- io_service_pool_.stop();
- io_service_work_pool_.stop();
- io_thread_->join();
- work_thread_->join();
- }
- private:
- boost::shared_ptr<boost::thread> io_thread_;
- boost::shared_ptr<boost::thread> work_thread_;
- io_service_pool io_service_pool_;
- io_service_pool io_service_work_pool_;
- tcp::acceptor acceptor_;
- };
- int main(int argc, char* argv[])
- {
- try
- {
- if (argc != 2)
- {
- std::cerr << "Usage: server <port>/n";
- return 1;
- }
- using namespace std; // For atoi.
- server s(atoi(argv[1]), 10);
- s.run();
- getchar();
- s.stop();
- }
- catch (std::exception& e)
- {
- std::cerr << "Exception: " << e.what() << "/n";
- }
- return 0;
- }
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