doc/html/boost_asio/example/cpp03/allocation/server.cpp
//
// server.cpp
// ~~~~~~~~~~
//
// Copyright (c) 2003-2023 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/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_memory
: private boost::noncopyable
{
public:
handler_memory()
: 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_;
};
// The allocator to be associated with the handler objects. This allocator only
// needs to satisfy the C++11 minimal allocator requirements, plus rebind when
// targeting C++03.
template <typename T>
class handler_allocator
{
public:
typedef T value_type;
explicit handler_allocator(handler_memory& mem)
: memory_(mem)
{
}
template <typename U>
handler_allocator(const handler_allocator<U>& other)
: memory_(other.memory_)
{
}
template <typename U>
struct rebind
{
typedef handler_allocator<U> other;
};
bool operator==(const handler_allocator& other) const
{
return &memory_ == &other.memory_;
}
bool operator!=(const handler_allocator& other) const
{
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:
// The underlying memory.
handler_memory& memory_;
};
class session
: public boost::enable_shared_from_this<session>
{
public:
session(boost::asio::io_context& io_context)
: socket_(io_context)
{
}
tcp::socket& socket()
{
return socket_;
}
void start()
{
socket_.async_read_some(boost::asio::buffer(data_),
boost::asio::bind_allocator(
handler_allocator<int>(handler_memory_),
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),
boost::asio::bind_allocator(
handler_allocator<int>(handler_memory_),
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_),
boost::asio::bind_allocator(
handler_allocator<int>(handler_memory_),
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 memory to use for handler-based custom memory allocation.
handler_memory handler_memory_;
};
typedef boost::shared_ptr<session> session_ptr;
class server
{
public:
server(boost::asio::io_context& io_context, short port)
: io_context_(io_context),
acceptor_(io_context, tcp::endpoint(tcp::v4(), port))
{
session_ptr new_session(new session(io_context_));
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_context_));
acceptor_.async_accept(new_session->socket(),
boost::bind(&server::handle_accept, this, new_session,
boost::asio::placeholders::error));
}
private:
boost::asio::io_context& io_context_;
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;
using namespace std; // For atoi.
server s(io_context, atoi(argv[1]));
io_context.run();
}
catch (std::exception& e)
{
std::cerr << "Exception: " << e.what() << "\n";
}
return 0;
}