void prepare_buffers()
        {
            //auto self = this->shared_from_this();
            res.complete_request_handler_ = nullptr;

            if (!adaptor_.is_open())
            {
                //CROW_LOG_DEBUG << this << " delete (socket is closed) " << is_reading << ' ' << is_writing;
                //delete this;
                return;
            }
            // TODO(EDev): HTTP version in status codes should be dynamic
            // Keep in sync with common.h/status
            static std::unordered_map<int, std::string> statusCodes = {
              {status::CONTINUE, "HTTP/1.1 100 Continue\r\n"},
              {status::SWITCHING_PROTOCOLS, "HTTP/1.1 101 Switching Protocols\r\n"},

              {status::OK, "HTTP/1.1 200 OK\r\n"},
              {status::CREATED, "HTTP/1.1 201 Created\r\n"},
              {status::ACCEPTED, "HTTP/1.1 202 Accepted\r\n"},
              {status::NON_AUTHORITATIVE_INFORMATION, "HTTP/1.1 203 Non-Authoritative Information\r\n"},
              {status::NO_CONTENT, "HTTP/1.1 204 No Content\r\n"},
              {status::RESET_CONTENT, "HTTP/1.1 205 Reset Content\r\n"},
              {status::PARTIAL_CONTENT, "HTTP/1.1 206 Partial Content\r\n"},

              {status::MULTIPLE_CHOICES, "HTTP/1.1 300 Multiple Choices\r\n"},
              {status::MOVED_PERMANENTLY, "HTTP/1.1 301 Moved Permanently\r\n"},
              {status::FOUND, "HTTP/1.1 302 Found\r\n"},
              {status::SEE_OTHER, "HTTP/1.1 303 See Other\r\n"},
              {status::NOT_MODIFIED, "HTTP/1.1 304 Not Modified\r\n"},
              {status::TEMPORARY_REDIRECT, "HTTP/1.1 307 Temporary Redirect\r\n"},
              {status::PERMANENT_REDIRECT, "HTTP/1.1 308 Permanent Redirect\r\n"},

              {status::BAD_REQUEST, "HTTP/1.1 400 Bad Request\r\n"},
              {status::UNAUTHORIZED, "HTTP/1.1 401 Unauthorized\r\n"},
              {status::FORBIDDEN, "HTTP/1.1 403 Forbidden\r\n"},
              {status::NOT_FOUND, "HTTP/1.1 404 Not Found\r\n"},
              {status::METHOD_NOT_ALLOWED, "HTTP/1.1 405 Method Not Allowed\r\n"},
              {status::PROXY_AUTHENTICATION_REQUIRED, "HTTP/1.1 407 Proxy Authentication Required\r\n"},
              {status::CONFLICT, "HTTP/1.1 409 Conflict\r\n"},
              {status::GONE, "HTTP/1.1 410 Gone\r\n"},
              {status::PAYLOAD_TOO_LARGE, "HTTP/1.1 413 Payload Too Large\r\n"},
              {status::UNSUPPORTED_MEDIA_TYPE, "HTTP/1.1 415 Unsupported Media Type\r\n"},
              {status::RANGE_NOT_SATISFIABLE, "HTTP/1.1 416 Range Not Satisfiable\r\n"},
              {status::EXPECTATION_FAILED, "HTTP/1.1 417 Expectation Failed\r\n"},
              {status::PRECONDITION_REQUIRED, "HTTP/1.1 428 Precondition Required\r\n"},
              {status::TOO_MANY_REQUESTS, "HTTP/1.1 429 Too Many Requests\r\n"},
              {status::UNAVAILABLE_FOR_LEGAL_REASONS, "HTTP/1.1 451 Unavailable For Legal Reasons\r\n"},

              {status::INTERNAL_SERVER_ERROR, "HTTP/1.1 500 Internal Server Error\r\n"},
              {status::NOT_IMPLEMENTED, "HTTP/1.1 501 Not Implemented\r\n"},
              {status::BAD_GATEWAY, "HTTP/1.1 502 Bad Gateway\r\n"},
              {status::SERVICE_UNAVAILABLE, "HTTP/1.1 503 Service Unavailable\r\n"},
              {status::GATEWAY_TIMEOUT, "HTTP/1.1 504 Gateway Timeout\r\n"},
              {status::VARIANT_ALSO_NEGOTIATES, "HTTP/1.1 506 Variant Also Negotiates\r\n"},
            };

            static const std::string seperator = ": ";

            buffers_.clear();
            buffers_.reserve(4 * (res.headers.size() + 5) + 3);

            if (!statusCodes.count(res.code))
            {
                CROW_LOG_WARNING << this << " status code "
                                 << "(" << res.code << ")"
                                 << " not defined, returning 500 instead";
                res.code = 500;
            }

            auto& status = statusCodes.find(res.code)->second;
            buffers_.emplace_back(status.data(), status.size());

            if (res.code >= 400 && res.body.empty())
                res.body = statusCodes[res.code].substr(9);

            for (auto& kv : res.headers)
            {
                buffers_.emplace_back(kv.first.data(), kv.first.size());
                buffers_.emplace_back(seperator.data(), seperator.size());
                buffers_.emplace_back(kv.second.data(), kv.second.size());
                buffers_.emplace_back(crlf.data(), crlf.size());
            }

            if (!res.manual_length_header && !res.headers.count("content-length"))
            {
                content_length_ = std::to_string(res.body.size());
                static std::string content_length_tag = "Content-Length: ";
                buffers_.emplace_back(content_length_tag.data(), content_length_tag.size());
                buffers_.emplace_back(content_length_.data(), content_length_.size());
                buffers_.emplace_back(crlf.data(), crlf.size());
            }
            if (!res.headers.count("server"))
            {
                static std::string server_tag = "Server: ";
                buffers_.emplace_back(server_tag.data(), server_tag.size());
                buffers_.emplace_back(server_name_.data(), server_name_.size());
                buffers_.emplace_back(crlf.data(), crlf.size());
            }
            if (!res.headers.count("date"))
            {
                static std::string date_tag = "Date: ";
                date_str_ = get_cached_date_str();
                buffers_.emplace_back(date_tag.data(), date_tag.size());
                buffers_.emplace_back(date_str_.data(), date_str_.size());
                buffers_.emplace_back(crlf.data(), crlf.size());
            }
            if (add_keep_alive_)
            {
                static std::string keep_alive_tag = "Connection: Keep-Alive";
                buffers_.emplace_back(keep_alive_tag.data(), keep_alive_tag.size());
                buffers_.emplace_back(crlf.data(), crlf.size());
            }

            buffers_.emplace_back(crlf.data(), crlf.size());
        }