71 lines
1.7 KiB
C++
71 lines
1.7 KiB
C++
/* Copyright 2003-2022 Joaquin M Lopez Munoz.
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* See http://www.boost.org/libs/multi_index for library home page.
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*/
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#ifndef BOOST_MULTI_INDEX_DETAIL_SCOPED_BILOCK_HPP
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#define BOOST_MULTI_INDEX_DETAIL_SCOPED_BILOCK_HPP
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#if defined(_MSC_VER)
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#pragma once
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#endif
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#include <boost/core/noncopyable.hpp>
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#include <boost/type_traits/aligned_storage.hpp>
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#include <boost/type_traits/alignment_of.hpp>
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#include <functional>
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#include <new>
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namespace boost{
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namespace multi_index{
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namespace detail{
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/* Locks/unlocks two RAII-lockable mutexes taking care that locking is done in
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* a deadlock-avoiding global order and no double locking happens when the two
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* mutexes are the same.
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*/
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template<typename Mutex>
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class scoped_bilock:private noncopyable
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{
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public:
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scoped_bilock(Mutex& mutex1,Mutex& mutex2):mutex_eq(&mutex1==&mutex2)
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{
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bool mutex_lt=std::less<Mutex*>()(&mutex1,&mutex2);
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::new (static_cast<void*>(&lock1)) scoped_lock(mutex_lt?mutex1:mutex2);
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if(!mutex_eq)
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::new (static_cast<void*>(&lock2)) scoped_lock(mutex_lt?mutex2:mutex1);
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}
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~scoped_bilock()
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{
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reinterpret_cast<scoped_lock*>(&lock1)->~scoped_lock();
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if(!mutex_eq)
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reinterpret_cast<scoped_lock*>(&lock2)->~scoped_lock();
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}
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private:
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typedef typename Mutex::scoped_lock scoped_lock;
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typedef typename aligned_storage<
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sizeof(scoped_lock),
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alignment_of<scoped_lock>::value
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>::type scoped_lock_space;
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bool mutex_eq;
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scoped_lock_space lock1,lock2;
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};
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} /* namespace multi_index::detail */
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} /* namespace multi_index */
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} /* namespace boost */
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#endif
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