123 lines
3.7 KiB
C++
123 lines
3.7 KiB
C++
/**
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* The contents of this file are based on the article posted at the
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* following location:
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*
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* http://crascit.com/2015/06/03/on-leaving-scope-part-2/
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*
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* The material in that article has some commonality with the code made
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* available as part of Facebook's folly library at:
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*
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* https://github.com/facebook/folly/blob/master/folly/ScopeGuard.h
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*
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* Furthermore, similar material is currently part of a draft proposal
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* to the C++ standards committee, referencing the same work by Andrei
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* Alexandresu that led to the folly implementation. The draft proposal
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* can be found at:
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*
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* http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4189.pdf
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*
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* With the above in mind, the content below is made available under
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* the same license terms as folly to minimize any legal concerns.
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* Should there be ambiguity over copyright ownership between Facebook
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* and myself for any material included in this file, it should be
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* interpreted that Facebook is the copyright owner for the ambiguous
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* section of code concerned.
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*
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* Craig Scott
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* 3rd June 2015
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*
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* ----------------------------------------------------------------------
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*
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* Copyright 2015 Craig Scott
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef CRASCIT_ONLEAVINGSCOPE_H
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#define CRASCIT_ONLEAVINGSCOPE_H
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#include <utility>
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#include <type_traits>
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/**
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* This class is intended to be used only to create a local object on the
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* stack. It accepts a function object in its constructor and will invoke
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* that function object in its destructor. The class provides a move
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* constructor so it can be used with the onLeavingScope factory function,
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* but it cannot be copied.
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*
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* Do no use this function directly, use the onLeavingScope() factory
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* function instead.
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*/
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template<typename Func>
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class OnLeavingScope
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{
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public:
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// Prevent copying
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OnLeavingScope(const OnLeavingScope&) = delete;
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OnLeavingScope& operator=(const OnLeavingScope&) = delete;
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// Allow moving
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OnLeavingScope(OnLeavingScope&& other) :
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m_func(std::move(other.m_func)),
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m_owner(other.m_owner)
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{
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other.m_owner = false;
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}
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OnLeavingScope(const Func& f) :
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m_func(f),
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m_owner(true)
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{
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}
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OnLeavingScope(Func&& f) :
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m_func(std::move(f)),
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m_owner(true)
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{
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}
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~OnLeavingScope()
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{
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if (m_owner)
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m_func();
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}
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private:
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Func m_func;
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bool m_owner;
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};
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/**
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* Factory function for creating an OnLeavingScope object. It is intended
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* to be used like so:
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*
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* auto cleanup = onLeavingScope(...);
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*
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* where the ... could be a lambda function, function object or pointer to
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* a free function to be invoked when the cleanup object goes out of scope.
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* The function object must take no function arguments, but can return any
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* type (the return value is ignored).
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*
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* The \a Func template parameter would rarely, if ever, be manually
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* specified. Normally, it would be deduced automatically by the compiler
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* from the object passed as the function argument.
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*/
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template<typename Func>
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OnLeavingScope<typename std::decay<Func>::type> onLeavingScope(Func&& f)
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{
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return OnLeavingScope<typename std::decay<Func>::type>(std::forward<Func>(f));
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}
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#endif // CRASCIT_ONLEAVINGSCOPE_H
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