//

// immer: immutable data structures for C++

// Copyright (C) 2016, 2017, 2018 Juan Pedro Bolivar Puente

//

// This software is distributed under the Boost Software License, Version 1.0.

// See accompanying file LICENSE or copy at http://boost.org/LICENSE_1_0.txt

//

#pragma once

#include <immer/refcount/no_refcount_policy.hpp>

#include <atomic>

#include <cassert>

#include <utility>

namespace immer {

/*!

 * A reference counting policy implemented using an *atomic* `int`

 * count.  It is **thread-safe**.

 */

struct refcount_policy

{

    mutable std::atomic<int> refcount;

    refcount_policy()

        : refcount{1} {};

    refcount_policy(disowned)

        : refcount{0}

    {

    }

    void inc() { refcount.fetch_add(1, std::memory_order_relaxed); }

    bool dec() { return 1 == refcount.fetch_sub(1, std::memory_order_acq_rel); }

    bool unique() { return refcount == 1; }

};

} // namespace immer