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