VTIL-Core/VTIL-Common/util/conditional_lock.hpp
2020-07-09 02:43:51 +02:00

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// Copyright (c) 2020 Can Boluk and contributors of the VTIL Project
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// 3. Neither the name of VTIL Project nor the names of its contributors
// may be used to endorse or promote products derived from this software
// without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//
#pragma once
#include <mutex>
#include <shared_mutex>
namespace vtil
{
// This type behaves exactly the same as the original lock type, with the
// exception of constructing it empty if the condition bool is false.
//
template<typename lock_type, typename mutex_type>
struct cnd_variant_lock : lock_type
{
// Default constructors
//
cnd_variant_lock() {}
cnd_variant_lock( mutex_type& mtx ) : lock_type{ mtx } {}
// Construct from mutex and condition.
//
cnd_variant_lock( mutex_type& mtx, bool condition )
{
// If condition is passed:
//
if ( condition )
{
// Create a secondary lock with the mutex being actually
// acquired and swap states with the current empty instance.
//
lock_type lock{ mtx };
this->swap( lock );
}
}
};
// Declare shortcuts for unique_lock, shared_lock and lock_guard and their deduction guides.
//
template<typename T>
struct cnd_unique_lock : cnd_variant_lock<std::unique_lock<T>, T> { using cnd_variant_lock<std::unique_lock<T>, T>::cnd_variant_lock; };
template<typename T>
cnd_unique_lock( T&, bool )->cnd_unique_lock<T>;
template<typename T>
struct cnd_shared_lock : cnd_variant_lock<std::shared_lock<T>, T> { using cnd_variant_lock<std::shared_lock<T>, T>::cnd_variant_lock; };
template<typename T>
cnd_shared_lock( T&, bool )->cnd_shared_lock<T>;
template<typename T>
struct cnd_lock_guard : cnd_variant_lock<std::lock_guard<T>, T> { using cnd_variant_lock<std::lock_guard<T>, T>::cnd_variant_lock; };
template<typename T>
cnd_lock_guard( T&, bool )->cnd_lock_guard<T>;
};