Boost C++ Libraries

boost/json/detail/shared_resource.hpp

//
// Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
//
// 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)
//
// Official repository: https://github.com/boostorg/json
//

#ifndef BOOST_JSON_DETAIL_SHARED_RESOURCE_HPP
#define BOOST_JSON_DETAIL_SHARED_RESOURCE_HPP

#include <boost/container/pmr/memory_resource.hpp>
#include <boost/json/memory_resource.hpp>
#include <atomic>
#include <utility>

namespace boost {
namespace json {
namespace detail {

#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable: 4275) // non dll-interface class used as base for dll-interface class
#endif

struct BOOST_SYMBOL_VISIBLE
    shared_resource
    : container::pmr::memory_resource
{
    BOOST_JSON_DECL
    shared_resource();

    BOOST_JSON_DECL
    ~shared_resource();

    std::atomic<std::size_t> refs{ 1 };
};

template<class T>
class shared_resource_impl final
    : public shared_resource
{
    T t;

public:
    template<class... Args>
    shared_resource_impl(
        Args&&... args)
        : t(std::forward<Args>(args)...)
    {
    }

    void*
    do_allocate(
        std::size_t n,
        std::size_t align) override
    {
        return t.allocate(n, align);
    }

    void
    do_deallocate(
        void* p,
        std::size_t n,
        std::size_t align) override
    {
        return t.deallocate(p, n, align);
    }

    bool
    do_is_equal(
        memory_resource const&) const noexcept override
    {
        // VFALCO Is always false ok?
        return false;
    }
};

#ifdef _MSC_VER
#pragma warning(pop)
#endif

} // detail
} // namespace json
} // namespace boost

#endif