我目前正在试验 boost beast 库,现在对它的内存占用感到非常惊讶。我发现通过使用三种不同的响应类型(字符串、文件、动态),程序大小会增长到 6Mb。
为了更接近原因,我从库中获取了小型服务器示例并将其简化为以下步骤:
class http_connection : public std::enable_shared_from_this<http_connection>
{
public:
http_connection(tcp::socket socket) : socket_(std::move(socket)) { }
void start() {
read_request();
}
private:
tcp::socket socket_;
beast::flat_buffer buffer_{8192};
http::request<http::dynamic_body> request_;
void read_request() {
auto self = shared_from_this();
http::async_read(
socket_, buffer_, request_,
[self](beast::error_code ec,
std::size_t bytes_transferred)
{
self->write_response(std::make_shared<http::response<http::dynamic_body>>());
self->write_response(std::make_shared<http::response<http::file_body>>());
self->write_response(std::make_shared<http::response<http::string_body>>(), true);
});
}
template <class T>
void write_response(std::shared_ptr<T> response, bool dostop=false) {
auto self = shared_from_this();
http::async_write(
socket_,
*response,
[self,response,dostop](beast::error_code ec, std::size_t)
{
if (dostop)
self->socket_.shutdown(tcp::socket::shutdown_send, ec);
});
}
};
当我注释掉三个 self->write_response 行并编译程序并对结果执行 size 命令时,我得到:
text data bss dec hex filename
343474 1680 7408 352562 56132 small
当我删除第一次写的评论时,我得到:
864740 1714 7408 873862 d5586 small
text data bss dec hex filename
删除所有注释后,最终大小变为:
text data bss dec hex filename
1333510 1730 7408 1342648 147cb8 small
4,8M Feb 16 22:13 small*
现在的问题是:
难道我做错了什么?
有没有办法减小尺寸?
更新
真正的 process_request 看起来像:
void process_request() {
auto it = router.find(request.method(), request.target());
if (it != router.end()) {
auto response = it->getHandler()(doc_root_, request);
if (boost::apply_visitor(dsa::type::handler(), response) == TypeCode::dynamic_r) {
auto r = boost::get<std::shared_ptr<dynamic_response>>(response);
send(r);
return;
}
if (boost::apply_visitor(dsa::type::handler(), response) == TypeCode::file_r) {
auto r = boost::get<std::shared_ptr<file_response>>(response);
send(r);
return;
}
if (boost::apply_visitor(dsa::type::handler(), response) == TypeCode::string_r) {
auto r = boost::get<std::shared_ptr<string_response>>(response);
send(r);
return;
}
}
send(boost::get<std::shared_ptr<string_response>>(send_bad_response(
http::status::bad_request,
"Invalid request-method '" + std::string(req.method_string()) + "'\r\n")));
}
提前致谢