diff --git a/include/dsn/utility/defer.h b/include/dsn/utility/defer.h new file mode 100644 index 0000000000..e8c253b4d7 --- /dev/null +++ b/include/dsn/utility/defer.h @@ -0,0 +1,69 @@ +/* + * The MIT License (MIT) + * + * Copyright (c) 2015 Microsoft Corporation + * + * -=- Robust Distributed System Nucleus (rDSN) -=- + * + * 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. + */ + +namespace dsn { + +// `defer` is an useful util to implement RAII in golang, much alike +// `try...finally...` in java. In C++ we used to implement an RAII class +// wrapping around the resource: +// +// ```cpp +// struct object_raii +// { +// object_raii() { +// _obj = c_object_new(); +// } +// ~object_raii() { +// c_object_free(_obj); +// } +// private: +// c_object *_obj; +// }; +// ``` +// +// Now with `defer`, things will be simplified: +// +// ```cpp +// c_object *obj = c_object_new(); +// auto cleanup = dsn::defer([obj]() { c_object_free(obj); }); +// ``` + +template +struct deferred_action +{ + explicit deferred_action(Func &&func) noexcept : _func(std::move(func)) {} + ~deferred_action() { _func(); } +private: + Func _func; +}; + +template +inline deferred_action defer(Func &&func) +{ + return deferred_action(std::forward(func)); +} + +} // namespace dsn