boost :: asio是否会产生过多的小堆分配，还是我错了？

Question

#include <cstdlib>
#include <iostream>
#include <boost/bind.hpp>
#include <boost/asio.hpp>

using boost::asio::ip::tcp;

class session
{
public:
    session(boost::asio::io_service& io_service)
        : socket_(io_service)
    {
    }

    tcp::socket& socket()
    {
        return socket_;
    }

    void start()
    {
        socket_.async_read_some(boost::asio::buffer(data_, max_length - 1),
            boost::bind(&session::handle_read, 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)
        {
            data_[bytes_transferred] = '\0';
            if(NULL != strstr(data_, "quit"))
            {
                this->socket().shutdown(boost::asio::ip::tcp::socket::shutdown_both);
                this->socket().close(); // how to make this dispatch "handle_read()" with a "disconnected" flag?
            }
            else
            {
                boost::asio::async_write(socket_,
                    boost::asio::buffer(data_, bytes_transferred),
                    boost::bind(&session::handle_write, this,
                    boost::asio::placeholders::error));

                socket_.async_read_some(boost::asio::buffer(data_, max_length - 1),
                    boost::bind(&session::handle_read, this,
                    boost::asio::placeholders::error,
                    boost::asio::placeholders::bytes_transferred));
            }
        }
        else
        {
            delete this;
        }
    }

    void handle_write(const boost::system::error_code& error)
    {
        if (!error)
        {
            //
        }
        else
        {
            delete this;
        }
    }

private:
    tcp::socket socket_;
    enum { max_length = 1024 };
    char data_[max_length];
};

class server
{
public:
    server(boost::asio::io_service& io_service, short port)
        : io_service_(io_service),
        acceptor_(io_service, tcp::endpoint(tcp::v4(), port))
    {
        session* new_session = new session(io_service_);
        acceptor_.async_accept(new_session->socket(),
            boost::bind(&server::handle_accept, this, new_session,
            boost::asio::placeholders::error));
    }

    void handle_accept(session* new_session,
        const boost::system::error_code& error)
    {
        if (!error)
        {
            new_session->start();
            new_session = new session(io_service_);
            acceptor_.async_accept(new_session->socket(),
                boost::bind(&server::handle_accept, this, new_session,
                boost::asio::placeholders::error));
        }
        else
        {
            delete new_session;
        }
    }

private:
    boost::asio::io_service& io_service_;
    tcp::acceptor acceptor_;
};

int main(int argc, char* argv[])
{
    try
    {
        if (argc != 2)
        {
            std::cerr << "Usage: async_tcp_echo_server <port>\n";
            return 1;
        }

        boost::asio::io_service io_service;

        using namespace std; // For atoi.
        server s(io_service, atoi(argv[1]));

        io_service.run();
    }
    catch (std::exception& e)
    {
        std::cerr << "Exception: " << e.what() << "\n";
    }

    return 0;
}

在尝试使用boost :: asio时我注意到在对async_write（）/ async_read_some（）的调用中，使用了C ++“new”关键字。

此外，当使用客户端（1个连接）强调此回显服务器时，例如发送一些数据的100,000次，该程序的内存使用量越来越高。

发生了什么事？它会为每次通话分配内存吗？还是我错了？问，因为服务器应用程序将分配任何东西似乎都不正确。我可以处理它，比如使用内存池吗？

另一个问题：

请参阅“this-＆gt; socket（）。close（）;” ？
我想要它，正如它的评论所说的那样，最后一次调度相同的函数，并发生断开连接错误。需要做一些清理工作。我该怎么做？

谢谢所有大师（：

Answer 1

希望有人能做出贡献......

此外，在我对boost :: asio的实验中，我决定在服务器应用程序启动后立即进行。运行我将在C ++的'新'代码中设置一个断点，即在“new.cpp”@ function“void * __ CRTDECL operator new（size_t size）_THROW1（_STD bad_alloc）”。请注意，我正在使用MSVC 2008。

使用上述代码：

现在BP正在进行我正在连接一个客户端 分配完成（多次）（如预期的那样）（我知道，因为调试器在我设置时停在'new'关键字），新客户端现在可以发送/接收数据了。
我从客户端向服务器发送“hi” 'new'处的BP在handle_read（）处被击中。
源的来源是对async_write（）的调用（我用MSVC堆栈跟踪） 点击F5（继续）会在'new'处生成另一个断点 - 这次async_read_some（）调用会生成它。

结论： 每次此类操作都会生成对“新”的调用 !!!!!!最糟糕的情况是真正的服务器可能有！

所以，进一步寻找某种方式来使用某种内存池，这些“新”调用将不存在，这让我得到了一个例子：“分配”。
它的路径：“....... \ boost_1_43_0 \ libs \ asio \ example \ allocation \”。

对这段新代码（如下所示）做同样的事情，给了我欢呼结果;
调用async_write（）和async_read_some（）不会生成对'new'的调用。

到目前为止，这很好，但说实话，我不能说我完全明白这是怎么做的;正如你所看到的那样，分配器分解成几个部分，这让我感到有些困惑。

make_custom_alloc_handler（）＆lt; ---究竟是做什么的？ 什么是shared_from_this（）??
我看到“session”对象的成员为“handler_allocator allocator_”。每个“会话”对象是否包含这些对象的池？！我可以在“服务器”级别进行共享或其他方式吗？

“allocator”示例代码：

//
// server.cpp
// ~~~~~~~~~~
//
// Copyright (c) 2003-2010 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 <cstdlib>
#include <iostream>
#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 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_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_;
};

// Wrapper class template for handler objects to allow handler memory
// allocation to be customised. Calls to operator() are forwarded to the
// encapsulated handler.
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);
}

class session
    : public boost::enable_shared_from_this<session>
{
public:
    session(boost::asio::io_service& io_service)
        : socket_(io_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::asio::async_write(socket_,
                boost::asio::buffer(data_, bytes_transferred),
                make_custom_alloc_handler(allocator_, boost::bind(&session::handle_write, shared_from_this(), boost::asio::placeholders::error))
                );
        }
    }

    void handle_write(const boost::system::error_code& error)
    {
        if (!error)
        {
            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)));
        }
    }

private:
    // 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(boost::asio::io_service& io_service, short port)
        : io_service_(io_service),
        acceptor_(io_service, tcp::endpoint(tcp::v4(), port))
    {
        session_ptr new_session(new session(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_));
            acceptor_.async_accept(new_session->socket(),
                boost::bind(&server::handle_accept, this, new_session,
                boost::asio::placeholders::error));
        }
    }

private:
    boost::asio::io_service& io_service_;
    tcp::acceptor acceptor_;
};

int main(int argc, char* argv[])
{
    try
    {
        if (argc != 2)
        {
            std::cerr << "Usage: server <port>\n";
            return 1;
        }

        boost::asio::io_service io_service;

        using namespace std; // For atoi.
        server s(io_service, atoi(argv[1]));

        io_service.run();
    }
    catch (std::exception& e)
    {
        std::cerr << "Exception: " << e.what() << "\n";
    }

    return 0;
}

Answer 2

要回答你的第二个问题，你可以使用io_service :: post给它一个绑定到session :: handle_read的boost :: bind参数以及你想要的任何错误代码。