e.cpp

//
// Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail 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)
//
// Official repository: https://github.com/boostorg/beast
//

//------------------------------------------------------------------------------
//
// Example: HTTP server, synchronous
//
//------------------------------------------------------------------------------

#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/version.hpp>
#include <boost/asio/ip/tcp.hpp>
#include <boost/config.hpp>
#include <cstdlib>
#include <iostream>
#include <memory>
#include <string>
#include <thread>

using tcp = boost::asio::ip::tcp;       // from <boost/asio/ip/tcp.hpp>
namespace http = boost::beast::http;    // from <boost/beast/http.hpp>

//------------------------------------------------------------------------------

// This function produces an HTTP response for the given
// request. The type of the response object depends on the
// contents of the request, so the interface requires the
// caller to pass a generic lambda for receiving the response.
template<
    class Body, class Allocator,
    class Send>
void
handle_request(
    boost::beast::string_view doc_root,
    http::request<Body, http::basic_fields<Allocator>>&& req,
    Send&& send)
{
    http::response<http::string_body> res {http::status::ok, req.version()};
    res.set(http::field::server, BOOST_BEAST_VERSION_STRING);
    res.body() = "hello world";
    res.keep_alive(req.keep_alive());
    return send(std::move(res));
}

//------------------------------------------------------------------------------

// Report a failure
void
fail(boost::system::error_code ec, char const* what)
{
    std::cerr << what << ": " << ec.message() << "\n";
}

// This is the C++11 equivalent of a generic lambda.
// The function object is used to send an HTTP message.
template<class Stream>
struct send_lambda
{
    Stream& stream_;
    bool& close_;
    boost::system::error_code& ec_;

    explicit
    send_lambda(
        Stream& stream,
        bool& close,
        boost::system::error_code& ec)
        : stream_(stream)
        , close_(close)
        , ec_(ec)
    {
    }

    template<bool isRequest, class Body, class Fields>
    void
    operator()(http::message<isRequest, Body, Fields>&& msg) const
    {
        // Determine if we should close the connection after
        close_ = msg.need_eof();

        // We need the serializer here because the serializer requires
        // a non-const file_body, and the message oriented version of
        // http::write only works with const messages.
        http::serializer<isRequest, Body, Fields> sr{msg};
        http::write(stream_, sr, ec_);
    }
};

// Handles an HTTP server connection
void
do_session(
    tcp::socket& socket,
    std::shared_ptr<std::string const> const& doc_root)
{
    bool close = false;
    boost::system::error_code ec;

    // This buffer is required to persist across reads
    boost::beast::flat_buffer buffer;

    // This lambda is used to send messages
    send_lambda<tcp::socket> lambda{socket, close, ec};

    for(;;)
    {
        // Read a request
        http::request<http::string_body> req;
        http::read(socket, buffer, req, ec);
        if(ec == http::error::end_of_stream)
            break;
        if(ec)
            return fail(ec, "read");

        // Send the response
        handle_request(*doc_root, std::move(req), lambda);
        if(ec)
            return fail(ec, "write");
        if(close)
        {
            // This means we should close the connection, usually because
            // the response indicated the "Connection: close" semantic.
            break;
        }
    }

    // Send a TCP shutdown
    socket.shutdown(tcp::socket::shutdown_send, ec);

    // At this point the connection is closed gracefully
}

//------------------------------------------------------------------------------

int main(int argc, char* argv[])
{
    try
    {
        // Check command line arguments.
        if (argc != 4)
        {
            std::cerr <<
                "Usage: http-server-sync <address> <port> <doc_root>\n" <<
                "Example:\n" <<
                "    http-server-sync 0.0.0.0 8080 .\n";
            return EXIT_FAILURE;
        }
        auto const address = boost::asio::ip::make_address(argv[1]);
        auto const port = static_cast<unsigned short>(std::atoi(argv[2]));
        auto const doc_root = std::make_shared<std::string>(argv[3]);

        // The io_context is required for all I/O
        boost::asio::io_context ioc{1};

        // The acceptor receives incoming connections
        tcp::acceptor acceptor{ioc, {address, port}};
        for(;;)
        {
            // This will receive the new connection
            tcp::socket socket{ioc};

            // Block until we get a connection
            acceptor.accept(socket);

            // Launch the session, transferring ownership of the socket
            std::thread{std::bind(
                &do_session,
                std::move(socket),
                doc_root)}.detach();
        }
    }
    catch (const std::exception& e)
    {
        std::cerr << "Error: " << e.what() << std::endl;
        return EXIT_FAILURE;
    }
}