Re: [Boost-users] [beast] help with http::dynamic_body and http::buffer_body

26 Apr 2021

      Hello,
...
Would you mind sharing your code (perhaps in a git repo) so that I can reproduce, debug and advise?
No problem, the code is just a slightly modified version of the example:

//
// Copyright (c) 2016-2019 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, asynchronous
//
//------------------------------------------------------------------------------

#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/version.hpp>
#include <boost/asio/dispatch.hpp>
#include <boost/asio/strand.hpp>
#include <boost/asio/buffers_iterator.hpp>
#include <boost/config.hpp>
#include <algorithm>
#include <cstdlib>
#include <functional>
#include <iostream>
#include <memory>
#include <string>
#include <thread>
#include <vector>

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

// Return a reasonable mime type based on the extension of a file.
beast::string_view
mime_type(beast::string_view path)
{
                using beast::iequals;
                auto const ext = [&path]
                {
                               auto const pos = path.rfind(".");
                               if(pos == beast::string_view::npos)
                                               return beast::string_view{};
                               return path.substr(pos);
                }();
                if(iequals(ext, ".htm"))  return "text/html";
                if(iequals(ext, ".html")) return "text/html";
                if(iequals(ext, ".php"))  return "text/html";
                if(iequals(ext, ".css"))  return "text/css";
                if(iequals(ext, ".txt"))  return "text/plain";
                if(iequals(ext, ".js"))   return "application/javascript";
                if(iequals(ext, ".json")) return "application/json";
                if(iequals(ext, ".xml"))  return "application/xml";
                if(iequals(ext, ".swf"))  return "application/x-shockwave-flash";
                if(iequals(ext, ".flv"))  return "video/x-flv";
                if(iequals(ext, ".png"))  return "image/png";
                if(iequals(ext, ".jpe"))  return "image/jpeg";
                if(iequals(ext, ".jpeg")) return "image/jpeg";
                if(iequals(ext, ".jpg"))  return "image/jpeg";
                if(iequals(ext, ".gif"))  return "image/gif";
                if(iequals(ext, ".bmp"))  return "image/bmp";
                if(iequals(ext, ".ico"))  return "image/vnd.microsoft.icon";
                if(iequals(ext, ".tiff")) return "image/tiff";
                if(iequals(ext, ".tif"))  return "image/tiff";
                if(iequals(ext, ".svg"))  return "image/svg+xml";
                if(iequals(ext, ".svgz")) return "image/svg+xml";
                return "application/text";
}

// Append an HTTP rel-path to a local filesystem path.
// The returned path is normalized for the platform.
std::string
path_cat(
                beast::string_view base,
                beast::string_view path)
{
                if(base.empty())
                               return std::string(path);
                std::string result(base);
#ifdef BOOST_MSVC
                char constexpr path_separator = '\\';
                if(result.back() == path_separator)
                               result.resize(result.size() - 1);
                result.append(path.data(), path.size());
                for(auto& c : result)
                               if(c == '/')
                                               c = path_separator;
#else
                char constexpr path_separator = '/';
                if(result.back() == path_separator)
                               result.resize(result.size() - 1);
                result.append(path.data(), path.size());
#endif
                return result;
}

// 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(
                beast::string_view doc_root,
                http::request<Body, http::basic_fields<Allocator>>&& req,
                Send&& send)
{
                // Returns a bad request response
                auto const bad_request =
                [&req](beast::string_view why)
                {
                               http::response<http::string_body> res{http::status::bad_request, req.version()};
                               res.set(http::field::server, BOOST_BEAST_VERSION_STRING);
                               res.set(http::field::content_type, "text/html");
                               res.keep_alive(req.keep_alive());
                               res.body() = std::string(why);
                               res.prepare_payload();
                               return res;
                };

                // Returns a not found response
                auto const not_found =
                [&req](beast::string_view target)
                {
                               http::response<http::string_body> res{http::status::not_found, req.version()};
                               res.set(http::field::server, BOOST_BEAST_VERSION_STRING);
                               res.set(http::field::content_type, "text/html");
                               res.keep_alive(req.keep_alive());
                               res.body() = "The resource '" + std::string(target) + "' was not found.";
                               res.prepare_payload();
                               return res;
                };

                // Returns a server error response
                auto const server_error =
                [&req](beast::string_view what)
                {
                               http::response<http::string_body> res{http::status::internal_server_error, req.version()};
                               res.set(http::field::server, BOOST_BEAST_VERSION_STRING);
                               res.set(http::field::content_type, "text/html");
                               res.keep_alive(req.keep_alive());
                               res.body() = "An error occurred: '" + std::string(what) + "'";
                               res.prepare_payload();
                               return res;
                };

                if (req.method() == http::verb::post && req.target()=="/xxx" )
                {
                               for (const auto &h:req)
                                               printf("heder: %s=%s\n", std::string(h.name_string()).c_str(), std::string(h.value()).c_str());
                               printf("body as string:\n");
                               std::string body{ boost::asio::buffers_begin(req.body().data()),
                                                 boost::asio::buffers_end(req.body().data()) };
                               printf("%s", body.c_str());
                               printf("end of body as string\n");
                               printf("body with iterator:\n");
                               const auto begin = boost::asio::buffers_begin(req.body().data());
                               const auto end   = boost::asio::buffers_end(req.body().data());
                               unsigned x=0;
                               for (auto it = begin; it != end; it++)
                                               putchar(*it);
                               printf("end of body with iterator\n");
                }

                // Make sure we can handle the method
                if( req.method() != http::verb::get &&
                               req.method() != http::verb::head)
                               return send(bad_request("Unknown HTTP-method"));

                // Request path must be absolute and not contain "..".
                if( req.target().empty() ||
                               req.target()[0] != '/' ||
                               req.target().find("..") != beast::string_view::npos)
                               return send(bad_request("Illegal request-target"));

                // Build the path to the requested file
                std::string path = path_cat(doc_root, req.target());
                if(req.target().back() == '/')
                               path.append("index.html");

                // Attempt to open the file
                beast::error_code ec;
                http::file_body::value_type body;
                body.open(path.c_str(), beast::file_mode::scan, ec);

                // Handle the case where the file doesn't exist
                if(ec == beast::errc::no_such_file_or_directory)
                               return send(not_found(req.target()));

                // Handle an unknown error
                if(ec)
                               return send(server_error(ec.message()));

                // Cache the size since we need it after the move
                auto const size = body.size();

                // Respond to HEAD request
                if(req.method() == http::verb::head)
                {
                               http::response<http::empty_body> res{http::status::ok, req.version()};
                               res.set(http::field::server, BOOST_BEAST_VERSION_STRING);
                               res.set(http::field::content_type, mime_type(path));
                               res.content_length(size);
                               res.keep_alive(req.keep_alive());
                               return send(std::move(res));
                }

                // Respond to GET request
                http::response<http::file_body> res{
                               std::piecewise_construct,
                               std::make_tuple(std::move(body)),
                               std::make_tuple(http::status::ok, req.version())};
                res.set(http::field::server, BOOST_BEAST_VERSION_STRING);
                res.set(http::field::content_type, mime_type(path));
                res.content_length(size);
                res.keep_alive(req.keep_alive());
                return send(std::move(res));
}

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

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

// Handles an HTTP server connection
class session : public std::enable_shared_from_this<session>
{
                // This is the C++11 equivalent of a generic lambda.
                // The function object is used to send an HTTP message.
                struct send_lambda
                {
                               session& self_;

                               explicit
                               send_lambda(session& self)
                                               : self_(self)
                               {
                               }

                               template<bool isRequest, class Body, class Fields>
                               void
                               operator()(http::message<isRequest, Body, Fields>&& msg) const
                               {
                                               // The lifetime of the message has to extend
                                               // for the duration of the async operation so
                                               // we use a shared_ptr to manage it.
                                               auto sp = std::make_shared<
                                                               http::message<isRequest, Body, Fields>>(std::move(msg));

                                               // Store a type-erased version of the shared
                                               // pointer in the class to keep it alive.
                                               self_.res_ = sp;

                                               // Write the response
                                               http::async_write(
                                                               self_.stream_,
                                                               *sp,
                                                               beast::bind_front_handler(
                                                                               &session::on_write,
                                                                               self_.shared_from_this(),
                                                                               sp->need_eof()));
                               }
                };

                beast::tcp_stream stream_;
                beast::flat_buffer buffer_;
                std::shared_ptr<std::string const> doc_root_;
//            http::request<http::string_body> req_;
                http::request<http::dynamic_body> req_;
                std::shared_ptr<void> res_;
                send_lambda lambda_;

public:
                // Take ownership of the stream
                session(
                               tcp::socket&& socket,
                               std::shared_ptr<std::string const> const& doc_root)
                               : stream_(std::move(socket))
                               , doc_root_(doc_root)
                               , lambda_(*this)
                {
                }

                // Start the asynchronous operation
                void
                run()
                {
                               // We need to be executing within a strand to perform async operations
                               // on the I/O objects in this session. Although not strictly necessary
                               // for single-threaded contexts, this example code is written to be
                               // thread-safe by default.
                               net::dispatch(stream_.get_executor(),
                                                                                              beast::bind_front_handler(
                                                                                                              &session::do_read,
                                                                                                              shared_from_this()));
                }

                void
                do_read()
                {
                               // Make the request empty before reading,
                               // otherwise the operation behavior is undefined.
                               req_ = {};

                               // Set the timeout.
                               stream_.expires_after(std::chrono::seconds(30));

                               // Read a request
                               http::async_read(stream_, buffer_, req_,
                                               beast::bind_front_handler(
                                                               &session::on_read,
                                                               shared_from_this()));
                }

                void
                on_read(
                               beast::error_code ec,
                               std::size_t bytes_transferred)
                {
                               boost::ignore_unused(bytes_transferred);

                               // This means they closed the connection
                               if(ec == http::error::end_of_stream)
                                                return do_close();

                               if(ec)
                                               return fail(ec, "read");

                               // Send the response
                               handle_request(*doc_root_, std::move(req_), lambda_);
                }

                void
                on_write(
                               bool close,
                               beast::error_code ec,
                               std::size_t bytes_transferred)
                {
                               boost::ignore_unused(bytes_transferred);

                               if(ec)
                                               return fail(ec, "write");

                               if(close)
                               {
                                               // This means we should close the connection, usually because
                                               // the response indicated the "Connection: close" semantic.
                                               return do_close();
                               }

                               // We're done with the response so delete it
                               res_ = nullptr;

                               // Read another request
                               do_read();
                }

                void
                do_close()
                {
                               // Send a TCP shutdown
                               beast::error_code ec;
                               stream_.socket().shutdown(tcp::socket::shutdown_send, ec);

                               // At this point the connection is closed gracefully
                }
};

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

// Accepts incoming connections and launches the sessions
class listener : public std::enable_shared_from_this<listener>
{
                net::io_context& ioc_;
                tcp::acceptor acceptor_;
                std::shared_ptr<std::string const> doc_root_;

public:
                listener(
                               net::io_context& ioc,
                               tcp::endpoint endpoint,
                               std::shared_ptr<std::string const> const& doc_root)
                               : ioc_(ioc)
                               , acceptor_(net::make_strand(ioc))
                               , doc_root_(doc_root)
                {
                               beast::error_code ec;

                               // Open the acceptor
                               acceptor_.open(endpoint.protocol(), ec);
                               if(ec)
                               {
                                               fail(ec, "open");
                                               return;
                               }

                               // Allow address reuse
                               acceptor_.set_option(net::socket_base::reuse_address(true), ec);
                               if(ec)
                               {
                                               fail(ec, "set_option");
                                               return;
                               }

                               // Bind to the server address
                               acceptor_.bind(endpoint, ec);
                               if(ec)
                               {
                                               fail(ec, "bind");
                                               return;
                               }

                               // Start listening for connections
                               acceptor_.listen(
                                               net::socket_base::max_listen_connections, ec);
                               if(ec)
                               {
                                               fail(ec, "listen");
                                               return;
                               }
                }

                // Start accepting incoming connections
                void
                run()
                {
                               do_accept();
                }

private:
                void
                do_accept()
                {
                               // The new connection gets its own strand
                               acceptor_.async_accept(
                                               net::make_strand(ioc_),
                                               beast::bind_front_handler(
                                                               &listener::on_accept,
                                                               shared_from_this()));
                }

                void
                on_accept(beast::error_code ec, tcp::socket socket)
                {
                               if(ec)
                               {
                                               fail(ec, "accept");
                               }
                               else
                               {
                                               // Create the session and run it
                                               std::make_shared<session>(
                                                               std::move(socket),
                                                               doc_root_)->run();
                               }

                               // Accept another connection
                               do_accept();
                }
};

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

int main(int argc, char* argv[])
{
                // Check command line arguments.
                if (argc != 4)
                {
                               std::cerr <<
                                               "Usage: http-server-async <address> <port> <doc_root>\n" <<
                                               "Example:\n" <<
                                               "    http-server-async 0.0.0.0 8080 .\n";
                               return EXIT_FAILURE;
                }
                auto const address = net::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
                net::io_context ioc;

                // Create and launch a listening port
                std::make_shared<listener>(
                               ioc,
                               tcp::endpoint{address, port},
                               doc_root)->run();

                // Run the I/O service
                printf("running\n");
                ioc.run();

                return EXIT_SUCCESS;
}

And this is my index.html:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd>
<html xmlns=http://www.w3.org/1999/xhtml>
        <body>

                <form action="xxx" method="post" accept-charset="utf-8" enctype="multipart/form-data">
                        <label for="field0">field 0:</label><input type="text" id="field0" name="field0"/><br/><br/>
                        <label for="field1">field 1:</label><input type="password" id="field1" name="field1"/><br/><br/>
                        <label for="field2">field 2:</label><input type="text" id="field2" name="field2"/><br/><br/>
                        <label for="field3">field 3:</label><input type="text" id="field3" name="field3"/><br/><br/>
                        <label for="field4">field 4:</label><input type="file" id="field4" name="field4"/><br/><br/>
                        <input type="submit" value="Submit"/>
                </form>
        </body>
</html>

Klebsch Mario
Funktion | R&D

Tel: +49 (0) 531 38 701 718
Raum: Braunschweig, E20

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Re: [Boost-users] [beast] help with http::dynamic_body and http::buffer_body

Klebsch, Mario