Description

Crow is a C++ framework for creating HTTP or Websocket web services. It uses routing similar to Python's Flask which makes it easy to use. It is also extremely fast, beating multiple existing C++ frameworks as well as non-C++ frameworks.

Features

• Easy Routing (similar to Flask).
• Type-safe handlers.
• Blazingly fast (see this benchmark and this benchmark).
• Built in JSON support.
• Mustache based templating library (crow::mustache).
• Header only library (single header file available).
• Middleware support for extensions.
• HTTP/1.1 and Websocket support.
• Multi-part request and response support.
• Uses modern C++ (11/14)

Still in development

• Async support
• HTTP/2 support

Documentation

Available here.

Warning

If you are using Crow v0.3, then you have to put #define CROW_MAIN at the top of one and only one source file.

Examples

Hello World

#include "crow.h"

int main()
{
    crow::SimpleApp app;

    CROW_ROUTE(app, "/")([](){
        return "Hello world";
    });

    app.port(18080).multithreaded().run();
}

JSON Response

CROW_ROUTE(app, "/json")
([]{
    crow::json::wvalue x({{"message", "Hello, World!"}});
    x["message2"] = "Hello, World.. Again!";
    return x;
});

Arguments

CROW_ROUTE(app,"/hello/<int>")
([](int count){
    if (count > 100)
        return crow::response(400);
    std::ostringstream os;
    os << count << " bottles of beer!";
    return crow::response(os.str());
});

Handler arguments type check at compile time

// Compile error with message "Handler type is mismatched with URL parameters"
CROW_ROUTE(app,"/another/<int>")
([](int a, int b){
    return crow::response(500);
});

Handling JSON Requests

CROW_ROUTE(app, "/add_json")
.methods("POST"_method)
([](const crow::request& req){
    auto x = crow::json::load(req.body);
    if (!x)
        return crow::response(crow::status::BAD_REQUEST); // same as crow::response(400)
    int sum = x["a"].i()+x["b"].i();
    std::ostringstream os;
    os << sum;
    return crow::response{os.str()};
});

More examples can be found here.

Setting Up / Building

Available here.

Disclaimer

CrowCpp/Crow is a project based on ipkn/crow. Neither CrowCpp, it's members, or this project have been associated with, or endorsed or supported by ipkn (Jaeseung Ha) in any way. We do use ipkn/crow's source code under the BSD-3 clause license and sometimes refer to the public comments available on the github repository. But we do not in any way claim to be associated with or in contact with ipkn (Jaeseung Ha) regarding CrowCpp or CrowCpp/Crow

Attributions

Crow has incorporated the following libraries into its source.

http-parser (used for converting http strings to crow::request objects)

https://github.com/nodejs/http-parser

http_parser.c is based on src/http/ngx_http_parse.c from NGINX copyright
Igor Sysoev.

Additional changes are licensed under the same terms as NGINX and
copyright Joyent, Inc. and other Node contributors. All rights reserved.

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to
deal in the Software without restriction, including without limitation the
rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
sell copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
IN THE SOFTWARE.

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qs_parse (used for reading query string parameters)

https://github.com/bartgrantham/qs_parse

Copyright (c) 2010 Bart Grantham
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

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TinySHA1 (used during the websocket handshake, not for security)

https://github.com/mohaps/TinySHA1

TinySHA1 - a header only implementation of the SHA1 algorithm. Based on the
implementation in boost::uuid::details

Copyright (c) 2012-22 SAURAV MOHAPATRA [email protected]
Permission to use, copy, modify, and distribute this software for any purpose
with or without fee is hereby granted, provided that the above copyright
notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.

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Catch2 (used only in unit tests, not part of the actual framework)

https://github.com/catchorg/Catch2

Boost Software License - Version 1.0 - August 17th, 2003

Permission is hereby granted, free of charge, to any person or organization
obtaining a copy of the software and accompanying documentation covered by
this license (the "Software") to use, reproduce, display, distribute,
execute, and transmit the Software, and to prepare derivative works of the
Software, and to permit third-parties to whom the Software is furnished to
do so, all subject to the following:

The copyright notices in the Software and this entire statement, including
the above license grant, this restriction and the following disclaimer,
must be included in all copies of the Software, in whole or in part, and
all derivative works of the Software, unless such copies or derivative
works are solely in the form of machine-executable object code generated by
a source language processor.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.