life.hpp

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// SPDX-License-Identifier: BSD-3-Clause
/* Copyright 2016-2020, Intel Corporation */
 
#ifndef LIBPMEMOBJ_CPP_DESTROYER_HPP
#define LIBPMEMOBJ_CPP_DESTROYER_HPP
 
#include <cstddef>
#include <type_traits>
#include <utility>
 
#include <libpmemobj++/detail/array_traits.hpp>
#include <libpmemobj++/detail/integer_sequence.hpp>
 
namespace pmem
{
 
namespace detail
{
 
/*
 * Template for checking if T is not an array.
 */
template <typename T>
struct if_not_array {
    typedef T type;
};
 
/*
 * Template for checking if T is not an array.
 */
template <typename T>
struct if_not_array<T[]>;
 
/*
 * Template for checking if T is not an array.
 */
template <typename T, size_t N>
struct if_not_array<T[N]>;
 
/*
 * Template for checking if T is an array.
 */
template <typename T>
struct if_size_array;
 
/*
 * Template for checking if T is an array.
 */
template <typename T>
struct if_size_array<T[]>;
 
/*
 * Template for checking if T is an array.
 */
template <typename T, size_t N>
struct if_size_array<T[N]> {
    typedef T type[N];
};
 
/*
 * Calls object's constructor.
 *
 * Supports aggregate initialization since C++17
 */
template <typename T, typename... Args>
void
create(typename if_not_array<T>::type *ptr, Args &&... args)
{
#if __cpp_lib_is_aggregate
    if constexpr (std::is_aggregate_v<T>)
        new (static_cast<void *>(ptr)) T{std::forward<Args>(args)...};
    else
        new (static_cast<void *>(ptr)) T(std::forward<Args>(args)...);
#else
    new (static_cast<void *>(ptr)) T(std::forward<Args>(args)...);
#endif
}
 
/*
 * Recursively calls array's elements' constructors.
 */
template <typename T, typename... Args>
void
create(typename if_size_array<T>::type *ptr, Args &&... args)
{
    typedef typename detail::pp_array_type<T>::type I;
    enum { N = pp_array_elems<T>::elems };
 
    for (std::size_t i = 0; i < N; ++i)
        create<I>(&(*ptr)[i], std::forward<Args>(args)...);
}
 
/*
 * Calls the objects constructor.
 *
 * Unpacks the tuple to get constructor's parameters.
 */
template <typename T, size_t... Indices, typename Tuple>
void
create_from_tuple(void *ptr, index_sequence<Indices...>, Tuple tuple)
{
    new (ptr) T(std::get<Indices>(std::move(tuple))...);
}
 
/*
 * C-style function which calls T constructor with arguments packed in a tuple.
 *
 * The arg is a tuple containing constructor parameters.
 */
template <typename T, typename Tuple, typename... Args>
int
c_style_construct(void *ptr, void *arg)
{
    auto *arg_pack = static_cast<Tuple *>(arg);
 
    typedef typename make_index_sequence<Args...>::type index;
    try {
        create_from_tuple<T>(ptr, index(), std::move(*arg_pack));
    } catch (...) {
        return -1;
    }
 
    return 0;
}
 
/*
 * Calls object's destructor.
 */
template <typename T,
      typename = typename std::enable_if<
          !std::is_trivially_destructible<T>::value>::type>
void
destroy(typename if_not_array<T>::type &arg)
{
    arg.~T();
}
 
/*
 * Don't call destructors for POD types.
 */
template <typename T, typename dummy = void,
      typename = typename std::enable_if<
          std::is_trivially_destructible<T>::value>::type>
void
destroy(typename if_not_array<T>::type &)
{
}
 
/*
 * Recursively calls array's elements' destructors.
 */
template <typename T>
void
destroy(typename if_size_array<T>::type &arg)
{
    typedef typename detail::pp_array_type<T>::type I;
    enum { N = pp_array_elems<T>::elems };
 
    for (std::size_t i = 0; i < N; ++i)
        destroy<I>(arg[N - 1 - i]);
}
 
} /* namespace detail */
 
} /* namespace pmem */
 
#endif /* LIBPMEMOBJ_CPP_DESTROYER_HPP */