libhttpserver/examples/shared_state.cpp at master · etr/libhttpserver · GitHub

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This file is part of libhttpserver

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

// shared_state.cpp - the canonical example of when the class form is the

// right shape.

// The lambda form (see hello_world.cpp) is the recommended idiom for

// stateless endpoints. When two HTTP methods on the same path share

// mutable state, however, two independent lambdas cannot safely capture

// the same data: each handler is invoked concurrently from libmicrohttpd

// worker threads, and there is no natural object lifetime that both

// lambdas can attach to.

// An http_resource subclass solves this cleanly. The resource owns the

// shared data, every render_* override is a member function with access

// to it, and a single std::mutex guards every mutation and read.

#include <memory>

#include <mutex>

#include <string>

#include <httpserver.hpp>

class counter : public httpserver::http_resource {

public:

httpserver::http_response render_get(const httpserver::http_request&) override {

std::lock_guard<std::mutex> lk(m_);

return httpserver::http_response::string(std::to_string(n_));

}

httpserver::http_response render_post(const httpserver::http_request&) override {

std::lock_guard<std::mutex> lk(m_);

++n_;

return httpserver::http_response::string(std::to_string(n_)).with_status(201);

}

private:

std::mutex m_;

int n_ = 0;

};

int main() {

httpserver::webserver ws{httpserver::create_webserver(8080)};

ws.register_path("/counter", std::make_unique<counter>());

ws.start(true);

}

libhttpserver/examples/shared_state.cpp at master · etr/libhttpserver · GitHub

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