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MDEV-22438 add a function similar to std::make_scope_exit()
The idea was borrowed from http://wg21.link/p0052 scope_exit class is a helper, its name is hidden from user in the namespace detail. Alternative implementation of scope_exit with std::function looks slower on goldbolt.org as it may require allocation, etc. scope_exit doesn't need to own a callable, so beeing a pointer is enough. And std::decay produces such a pointer from callable.
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/* | ||
Copyright (c) 2020, MariaDB | ||
This program is free software; you can redistribute it and/or | ||
modify it under the terms of the GNU General Public License | ||
as published by the Free Software Foundation; version 2 of | ||
the License. | ||
This program 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 General Public License for more details. | ||
You should have received a copy of the GNU General Public License | ||
along with this program; if not, write to the Free Software | ||
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA | ||
*/ | ||
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#pragma once | ||
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#include <type_traits> | ||
#include <utility> | ||
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namespace detail | ||
{ | ||
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template <typename Callable> class scope_exit | ||
{ | ||
public: | ||
template <typename F> | ||
explicit scope_exit(F &&f) : function_(std::forward<F>(f)) | ||
{ | ||
} | ||
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scope_exit(scope_exit &&rhs) | ||
: function_(std::move(rhs.function_)), engaged_(rhs.engaged_) | ||
{ | ||
rhs.release(); | ||
} | ||
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scope_exit(const scope_exit &)= delete; | ||
scope_exit &operator=(scope_exit &&)= delete; | ||
scope_exit &operator=(const scope_exit &)= delete; | ||
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void release() { engaged_= false; } | ||
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~scope_exit() | ||
{ | ||
if (engaged_) | ||
function_(); | ||
} | ||
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private: | ||
Callable function_; | ||
bool engaged_= true; | ||
}; | ||
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} // end namespace detail | ||
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template <typename Callable> | ||
detail::scope_exit<typename std::decay<Callable>::type> | ||
make_scope_exit(Callable &&f) | ||
{ | ||
return detail::scope_exit<typename std::decay<Callable>::type>( | ||
std::forward<Callable>(f)); | ||
} |
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