temp_value.hpp

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// SPDX-License-Identifier: BSD-3-Clause
/* Copyright 2019-2021, Intel Corporation */
 
#ifndef LIBPMEMOBJ_CPP_TEMP_VALUE_HPP
#define LIBPMEMOBJ_CPP_TEMP_VALUE_HPP
 
#include <libpmemobj++/make_persistent.hpp>
 
namespace pmem
{
 
namespace detail
{
 
#ifndef LIBPMEMOBJ_CPP_MAX_STACK_ALLOC_SIZE
#define LIBPMEMOBJ_CPP_MAX_STACK_ALLOC_SIZE 64 * (1 << 10)
#endif
 
template <typename T, bool NoExcept, typename Enable = void>
struct temp_value;
 
/*
 * Specialization for non-throwing constructors and objects smaller than
 * LIBPMEMOBJ_CPP_MAX_STACK_ALLOC_SIZE bytes. Constructs and stores value in
 * underlying field.
 */
template <typename T, bool NoExcept>
struct temp_value<
    T, NoExcept,
    typename std::enable_if<NoExcept &&
                (sizeof(T) <
                 LIBPMEMOBJ_CPP_MAX_STACK_ALLOC_SIZE)>::type> {
    template <typename... Args>
    temp_value(Args &&... args) noexcept : t(std::forward<Args>(args)...)
    {
    }
 
    T &
    get() noexcept
    {
        return t;
    }
 
    T t;
};
 
/*
 * Specialization for throwing constructors or objects greater than or equal to
 * LIBPMEMOBJ_CPP_MAX_STACK_ALLOC_SIZE bytes. Constructs and stores value in
 * underlying field in pmem.
 */
template <typename T, bool NoExcept>
struct temp_value<
    T, NoExcept,
    typename std::enable_if<!NoExcept ||
                (sizeof(T) >=
                 LIBPMEMOBJ_CPP_MAX_STACK_ALLOC_SIZE)>::type> {
    template <typename... Args>
    temp_value(Args &&... args)
    {
        ptr = pmem::obj::make_persistent<T>(
            std::forward<Args>(args)...);
    }
 
    ~temp_value()
    {
        pmem::obj::delete_persistent<T>(ptr);
    }
 
    T &
    get()
    {
        return *ptr;
    }
 
    pmem::obj::persistent_ptr<T> ptr;
};
 
} /* namespace detail */
 
} /* namespace pmem */
 
#endif /* LIBPMEMOBJ_CPP_TEMP_VALUE_HPP */