本想找個好用方便簡單高效的c++ http服務器框架,看來看去也沒看到有非常合適的,後面也就懶得糾結了,用libevent自帶的http server功能吧,不過看了看接口,c語言的接口用起來還是不太方便,如果用戶是用c++,還要管理大量的c層面的指針,buffer,結構體等,於是就想着封裝成c++形式的,而且利用c++11以後的一些特性,可以完全屏蔽c的這些細節。
原博客格式更友好:http://www.straka.cn/blog/cpp-wrapped-http-server-based-on-libevent/
如下c++ http框架、庫摘自awesome-cpp: https://github.com/fffaraz/awesome-cpp#regular-expression
- ACE - An OO Network Programming Toolkit in C++. [?MIT?]
- Boost.Asio - A cross-platform C++ library for network and low-level I/O programming. [Boost]
- C++ REST SDK - C++ REST SDK (previously named Casablanca). [Apache2]
- Restbed - C++11 Asynchronous RESTful framework. [AGPL]
- Proxygen - Facebook's collection of C++ HTTP libraries including an easy to use HTTP server. [BSD]
- Muduo - A C++ non-blocking network library for multi-threaded server in Linux. [BSD]
- cpr - A modern C++ HTTP requests library with a simple but powerful interface. Modeled after the Python Requests module. [MIT] website
- Mongoose - Extremely lightweight webserver. [GPL2]
- libcurl - Multiprotocol file transfer library. [MIT/X derivate license]
- curlcpp - An object oriented C++ wrapper for CURL(libcurl). [MIT]
- Boost.Beast - HTTP and WebSocket built on Boost.Asio in C++11. [BSL-1.0] website
- Breep - Event based, high-level C++14 peer-to-peer library. [EUPL-1.1 (OSI approved)]
- libhttpserver - C++ library for creating an embedded Rest HTTP server (and more). [LGPL2.1]
- uWebSockets - µWS is one of the most lightweight, efficient & scalable WebSocket & HTTP server implementations available. [Zlib]
- restclient-cpp - Simple REST client for C++. It wraps libcurl for HTTP requests. [MIT]
- Seasocks - Simple, small, C++ embeddable webserver with WebSockets support. [BSD]
- Silicon - A high performance, middleware oriented C++14 http web framework. [MIT]
- nghttp2 - HTTP/2 C Library. [MIT] website
- Onion - HTTP server library in C designed to be lightweight and easy to use. [Apache2/GPL2]
- PicoHTTPParser - A tiny, primitive, fast HTTP request/response parser. [MIT]
- evpp - C++ high performance networking with TCP/UDP/HTTP protocols. [BSD]
- H2O - An optimized HTTP server with support for HTTP/1.x and HTTP/2. It can also be used as a library. [MIT]
- HTTP Parser - A http request/response parser for C. [MIT]
- Restinio - A header-only C++14 library that gives you an embedded HTTP/Websocket server. [BSD]
- cpp-httplib - A single file C++11 header-only HTTP/HTTPS sever library. [MIT]
- cpp-netlib - A collection of open-source libraries for high level network programming. [Boost]
我們先看下沒有封裝的,原生libevent的使用方法:
void http_handler(struct evhttp_request *req, void *arg) { //get uri const char *uri = evhttp_request_uri(req); char *decoded_uri = evhttp_decode_uri(uri); //get parameter struct evkeyvalq params; evhttp_parse_query(decoded_uri, ¶ms); evhttp_find_header(¶ms, "key"); free(decoded_uri); //get body char *post_data = (char *) EVBUFFER_DATA(req->input_buffer); ... //some other business logic ... evhttp_add_header(req->output_headers, "Content-Type", "text/plain; charset=UTF-8"); struct evbuffer *buf = evbuffer_new(); evbuffer_add_printf(buf, "Hello world!\n%s\n", output); evhttp_send_reply(req, HTTP_OK, "OK", buf); evbuffer_free(buf); } int main(){ char * serv_addr = "0.0.0.0"; short port = 80; int timeout = 10; event_init(); struct evhttp *serv = evhttp_start(serv_addr, port); evhttp_set_gencb(serv, http_handler, NULL); ... //do some setting like evhttp_set_timeout(serv, timeout); ... event_dispatch(); evhttp_free(serv); return 0; }
可以看到原生的libevent封裝的c風格的http接口,用起來不是很方便,初始化步驟比較多,服務處理句柄(http_handler)必須包含strucrt evhttp_request *,處理函數內也有大量和libevent相關的結構體和方法,也就是說要使用libevent原生的http功能,需要對libevent的結構體使用有一定程度的瞭解,而這些c風格的接口使用起來並不友好,到處是危險的指針,還要了解libevent本身對資源的管理,否則容易造成泄漏或者空指針引用,接口本身直接暴露了內部實現,而非針對用戶的使用習慣設計。
那麼我就考慮將其封裝爲c++風格,以使其方便使用,接口用戶友好,不用關心libevent的實現,而且可以完全按照c++風格編寫。
對於使用者而言,一個http的服務框架,最基礎的使用就是設置監聽地址、端口、超時時間這些基本的,然後就是註冊處理回調函數,然後編寫回調函數就ok了,回調函數中能很方便的拿到http報文中的url、header、body,這就基本滿足使用者需要,本文也致力於滿足這樣的一個需要,但不會把這個做的特別完善,對libevent已經提供的部分http功能做簡單的封裝,不會過多考慮http協議支持的完備性(如果大家覺得有必要,就慢慢改進吧)。
要把上述代碼封裝成c++風格的,總體而言沒多大難度,其中一個小障礙是註冊回調函數的c++風格化,要完全屏蔽libevent的底層實現,勢必要把回調函數的簽名給改了,那麼就存在兩種做法:
一種是在libevent中註冊默認處理回調函數,也就是evhttp_set_gencb(serv, http_handler, NULL);,然後在http_handler中自己做路由路徑的匹配,再分發到其他的處理函數中,這樣回調處理函數就可以以任意自定義方式實現,但是這給封裝帶來了額外的工作,畢竟libevent已經帶有請求路徑路由了。
另一種就是採用c++ function的一些特性,把用戶定義的回調函數轉換成libevent支持的回調函數方法,這也就是本文的實現方法。
接下來看代碼:
bool EvHttpServ::RegistHandler(std::string const &strUrl, HandlerFunc func){ if(!func){ return false; } typedef void (*handle_t)(EvHttpRequest *); //#TODO add middleware support auto TransFunc = [] (struct evhttp_request *req, void *arg) { if(NULL == req){ Utilis::LogWarn("Evhttp Request handler is NULL\n"); return; } EvHttpRequest httpReq(req); try{ handle_t f=reinterpret_cast<handle_t>(arg); f(&httpReq); }catch(EvHttpServRTEXCP rtExcp){ if(NULL != req){ /// Judge to prevent req has already been destroied httpReq.RespError(rtExcp.GetCode(),"Http hander throws error "); } }catch(std::exception e){ } }; handle_t* pph = func.target<handle_t>(); typedef void (*func_t)(struct evhttp_request *,void *); if(pph != nullptr ){ /// O SUCCESS,-1 ALREADY_EXIST,-2 FAILURE return (-2 != evhttp_set_cb(evHttp_, strUrl.c_str(), TransFunc,reinterpret_cast<void*>(*pph))); }else{ return false; } } void testHandler(EvHttpRequest *req){ ... } Serv.RegistHandler("/hi/test", testHandler);
其中利用了lambda函數完成了c++處理函數的統一,把本來用於給回調函數傳遞額外參數的void *arg用來傳遞對應的處理函數。
其餘部分的封裝結構還是比較簡單和明確的,兩個類,EvHttpServ、EvHttpRequest, 前者封裝了http服務的相關工作,比如構造函數裏的相關初始化工作,參數設置,另外提供了服務開啓停止,處理函數註冊、註銷的接口。後者封裝了請求本身相關的操作,畢竟同一個服務對應着併發存在的數個請求,所以分成兩個類去完成。
原博客地址:
http://www.straka.cn/blog/cpp-wrapped-http-server-based-on-libevent/
代碼倉庫地址:
https://github.com/atp798/EvHttp