v.hpp

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/*
 * Copyright 2018-2019, Intel Corporation
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *
 *     * 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.
 *
 *     * Neither the name of the copyright holder 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,
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef LIBPMEMOBJ_CPP_V_HPP
#define LIBPMEMOBJ_CPP_V_HPP

#include <memory>
#include <tuple>

#include <libpmemobj++/detail/common.hpp>
#include <libpmemobj++/detail/life.hpp>

namespace pmem
{

namespace obj
{

namespace experimental
{

template <typename T>
class v {
public:
    static_assert(std::is_default_constructible<T>::value,
              "Type T must be default constructible");

    v() noexcept : vlt{0}
    {
    }

    ~v()
    {
        /* Destructor of val should NOT be called */
    }

    v &
    operator=(const T &rhs)
    {
        /* make sure object is initialized */
        (void)get();

        val = rhs;

        return *this;
    }

    v &
    operator=(v &rhs)
    {
        return *this = rhs.get();
    }

    template <typename Y,
          typename = typename std::enable_if<
              std::is_convertible<Y, T>::value>::type>
    v &
    operator=(v<Y> &rhs)
    {
        return *this = rhs.get();
    }

    template <typename... Args>
    T &
    get(Args &&... args) noexcept
    {
        auto arg_pack =
            std::forward_as_tuple(std::forward<Args>(args)...);

        PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
        if (pop == NULL)
            return this->val;

        T *value = static_cast<T *>(pmemobj_volatile(
            pop, &this->vlt, &this->val, sizeof(T),
            pmem::detail::c_style_construct<T, decltype(arg_pack),
                            Args...>,
            static_cast<void *>(&arg_pack)));

        return *value;
    }

    T &
    unsafe_get()
    {
        return val;
    }

    operator T &() noexcept
    {
        return this->get();
    }

    void
    swap(v &other)
    {
        std::swap(get(), other.get());
    }

private:
    struct pmemvlt vlt;

    /*
     * Normally C++ requires all class members to be constructed during
     * enclosing type construction. Holding a value inside of a union allows
     * to bypass this requirement. val is only constructed by call to get().
     */
    union {
        T val;
    };
};

template <class T>
inline void
swap(v<T> &a, v<T> &b)
{
    a.swap(b);
}

} /* namespace experimental */

} /* namespace obj */

} /* namespace pmem */

#endif /* LIBPMEMOBJ_CPP_V_HPP */