deferred_response.hpp

/*
     This file is part of libhttpserver
     Copyright (C) 2011-2019 Sebastiano Merlino

     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Lesser General Public
     License as published by the Free Software Foundation; either
     version 2.1 of the License, or (at your option) any later version.

     This library is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Lesser General Public License for more details.

     You should have received a copy of the GNU Lesser General Public
     License along with this library; if not, write to the Free Software
     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301
     USA
*/

#if !defined (_HTTPSERVER_HPP_INSIDE_) && !defined (HTTPSERVER_COMPILATION)
#error "Only <httpserver.hpp> or <httpserverpp> can be included directly."
#endif

#ifndef _DEFERRED_RESPONSE_HPP_
#define _DEFERRED_RESPONSE_HPP_

#include <memory>
#include "httpserver/string_response.hpp"

namespace httpserver
{

namespace details
{
    MHD_Response* get_raw_response_helper(void* cls, bool completed, ssize_t (*cb)(void*, uint64_t, char*, size_t));
}

template <class T>
class deferred_response : public string_response
{
    public:
        explicit deferred_response(
                ssize_t(*cycle_callback)(std::shared_ptr<T>, char*, size_t),
                std::shared_ptr<T> closure_data,
                const std::string& content = "",
                int response_code = http::http_utils::http_ok,
                const std::string& content_type = http::http_utils::text_plain
        ):
            string_response(content, response_code, content_type),
            cycle_callback(cycle_callback),
            closure_data(closure_data),
            completed(false)
        {
        }

        deferred_response(const deferred_response& other):
            string_response(other),
            cycle_callback(other.cycle_callback),
            closure_data(other.closure_data),
            completed(other.completed)
        {
        }

        deferred_response(deferred_response&& other) noexcept:
            string_response(std::move(other)),
            cycle_callback(std::move(other.cycle_callback)),
            closure_data(std::move(other.closure_data)),
            completed(other.completed)
        {
        }

        deferred_response& operator=(const deferred_response& b)
        {
            if (this == &b) return *this;

            (string_response&) (*this) = b;
            this->cycle_callback = b.cycle_callback;
            this->closure_data = b.closure_data;
            this->completed = b.completed;

            return *this;
        }

        deferred_response& operator=(deferred_response&& b)
        {
            if (this == &b) return *this;

            (string_response&) (*this) = std::move(b);
            this->cycle_callback = std::move(b.cycle_callback);
            this->closure_data = std::move(b.closure_data);
            this->completed = b.completed;

            return *this;
        }

        ~deferred_response()
        {
        }

        MHD_Response* get_raw_response()
        {
            return details::get_raw_response_helper((void*) this, completed, &(this->cb));
        }

        void decorate_response(MHD_Response* response)
        {
            if(completed)
            {
                static_cast<string_response*>(this)->decorate_response(response);
            }
        }

    private:
        ssize_t (*cycle_callback)(std::shared_ptr<T>, char*, size_t);
        std::shared_ptr<T> closure_data;
        bool completed;

        static ssize_t cb(void* cls, uint64_t pos, char* buf, size_t max)
        {
            deferred_response<T>* dfr = static_cast<deferred_response<T>*>(cls);
            ssize_t val = dfr->cycle_callback(dfr->closure_data, buf, max);
            if(val == -1)
            {
                dfr->completed = true;
            }

            return val;
        }
};

}
#endif // _DEFERRED_RESPONSE_HPP_