| // |
| // server.cpp |
| // ~~~~~~~~~~ |
| // |
| // Copyright (c) 2003-2021 Christopher M. Kohlhoff (chris at kohlhoff dot com) |
| // |
| // Distributed under the Boost Software License, Version 1.0. (See accompanying |
| // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
| // |
| |
| #include <array> |
| #include <cstdlib> |
| #include <iostream> |
| #include <memory> |
| #include <type_traits> |
| #include <utility> |
| #include <boost/asio.hpp> |
| |
| using boost::asio::ip::tcp; |
| |
| // Class to manage the memory to be used for handler-based custom allocation. |
| // It contains a single block of memory which may be returned for allocation |
| // requests. If the memory is in use when an allocation request is made, the |
| // allocator delegates allocation to the global heap. |
| class handler_memory |
| { |
| public: |
| handler_memory() |
| : in_use_(false) |
| { |
| } |
| |
| handler_memory(const handler_memory&) = delete; |
| handler_memory& operator=(const handler_memory&) = delete; |
| |
| void* allocate(std::size_t size) |
| { |
| if (!in_use_ && size < sizeof(storage_)) |
| { |
| in_use_ = true; |
| return &storage_; |
| } |
| else |
| { |
| return ::operator new(size); |
| } |
| } |
| |
| void deallocate(void* pointer) |
| { |
| if (pointer == &storage_) |
| { |
| in_use_ = false; |
| } |
| else |
| { |
| ::operator delete(pointer); |
| } |
| } |
| |
| private: |
| // Storage space used for handler-based custom memory allocation. |
| typename std::aligned_storage<1024>::type storage_; |
| |
| // Whether the handler-based custom allocation storage has been used. |
| bool in_use_; |
| }; |
| |
| // The allocator to be associated with the handler objects. This allocator only |
| // needs to satisfy the C++11 minimal allocator requirements. |
| template <typename T> |
| class handler_allocator |
| { |
| public: |
| using value_type = T; |
| |
| explicit handler_allocator(handler_memory& mem) |
| : memory_(mem) |
| { |
| } |
| |
| template <typename U> |
| handler_allocator(const handler_allocator<U>& other) noexcept |
| : memory_(other.memory_) |
| { |
| } |
| |
| bool operator==(const handler_allocator& other) const noexcept |
| { |
| return &memory_ == &other.memory_; |
| } |
| |
| bool operator!=(const handler_allocator& other) const noexcept |
| { |
| return &memory_ != &other.memory_; |
| } |
| |
| T* allocate(std::size_t n) const |
| { |
| return static_cast<T*>(memory_.allocate(sizeof(T) * n)); |
| } |
| |
| void deallocate(T* p, std::size_t /*n*/) const |
| { |
| return memory_.deallocate(p); |
| } |
| |
| private: |
| template <typename> friend class handler_allocator; |
| |
| // The underlying memory. |
| handler_memory& memory_; |
| }; |
| |
| // Wrapper class template for handler objects to allow handler memory |
| // allocation to be customised. The allocator_type type and get_allocator() |
| // member function are used by the asynchronous operations to obtain the |
| // allocator. Calls to operator() are forwarded to the encapsulated handler. |
| template <typename Handler> |
| class custom_alloc_handler |
| { |
| public: |
| using allocator_type = handler_allocator<Handler>; |
| |
| custom_alloc_handler(handler_memory& m, Handler h) |
| : memory_(m), |
| handler_(h) |
| { |
| } |
| |
| allocator_type get_allocator() const noexcept |
| { |
| return allocator_type(memory_); |
| } |
| |
| template <typename ...Args> |
| void operator()(Args&&... args) |
| { |
| handler_(std::forward<Args>(args)...); |
| } |
| |
| private: |
| handler_memory& memory_; |
| 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_memory& m, Handler h) |
| { |
| return custom_alloc_handler<Handler>(m, h); |
| } |
| |
| class session |
| : public std::enable_shared_from_this<session> |
| { |
| public: |
| session(tcp::socket socket) |
| : socket_(std::move(socket)) |
| { |
| } |
| |
| void start() |
| { |
| do_read(); |
| } |
| |
| private: |
| void do_read() |
| { |
| auto self(shared_from_this()); |
| socket_.async_read_some(boost::asio::buffer(data_), |
| make_custom_alloc_handler(handler_memory_, |
| [this, self](boost::system::error_code ec, std::size_t length) |
| { |
| if (!ec) |
| { |
| do_write(length); |
| } |
| })); |
| } |
| |
| void do_write(std::size_t length) |
| { |
| auto self(shared_from_this()); |
| boost::asio::async_write(socket_, boost::asio::buffer(data_, length), |
| make_custom_alloc_handler(handler_memory_, |
| [this, self](boost::system::error_code ec, std::size_t /*length*/) |
| { |
| if (!ec) |
| { |
| do_read(); |
| } |
| })); |
| } |
| |
| // The socket used to communicate with the client. |
| tcp::socket socket_; |
| |
| // Buffer used to store data received from the client. |
| std::array<char, 1024> data_; |
| |
| // The memory to use for handler-based custom memory allocation. |
| handler_memory handler_memory_; |
| }; |
| |
| class server |
| { |
| public: |
| server(boost::asio::io_context& io_context, short port) |
| : acceptor_(io_context, tcp::endpoint(tcp::v4(), port)) |
| { |
| do_accept(); |
| } |
| |
| private: |
| void do_accept() |
| { |
| acceptor_.async_accept( |
| [this](boost::system::error_code ec, tcp::socket socket) |
| { |
| if (!ec) |
| { |
| std::make_shared<session>(std::move(socket))->start(); |
| } |
| |
| do_accept(); |
| }); |
| } |
| |
| tcp::acceptor acceptor_; |
| }; |
| |
| int main(int argc, char* argv[]) |
| { |
| try |
| { |
| if (argc != 2) |
| { |
| std::cerr << "Usage: server <port>\n"; |
| return 1; |
| } |
| |
| boost::asio::io_context io_context; |
| server s(io_context, std::atoi(argv[1])); |
| io_context.run(); |
| } |
| catch (std::exception& e) |
| { |
| std::cerr << "Exception: " << e.what() << "\n"; |
| } |
| |
| return 0; |
| } |