persistent_ptr_base.hpp

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/*
 * Copyright 2016-2021, 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
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 */
 
#ifndef LIBPMEMOBJ_CPP_PERSISTENT_PTR_BASE_HPP
#define LIBPMEMOBJ_CPP_PERSISTENT_PTR_BASE_HPP
 
#include <cstdint>
#include <type_traits>
 
#include <libpmemobj++/detail/common.hpp>
#include <libpmemobj++/detail/specialization.hpp>
#include <libpmemobj/base.h>
 
/* Windows has a max macro which collides with std::numeric_limits::max */
#if defined(max) && defined(_WIN32)
#undef max
#endif
 
namespace pmem
{
 
namespace detail
{
 
template <typename T>
class persistent_ptr_base {
    typedef persistent_ptr_base<T> this_type;
 
    template <typename U>
    friend class persistent_ptr_base;
 
public:
    typedef typename pmem::detail::sp_element<T>::type element_type;
 
    persistent_ptr_base() : oid(OID_NULL)
    {
        verify_type();
    }
 
    /*
     * Curly braces initialization is not used because the
     * PMEMoid is a plain C (POD) type and we can't add a default
     * constructor in there.
     */
 
    persistent_ptr_base(PMEMoid oid) noexcept : oid(oid)
    {
        verify_type();
    }
 
    persistent_ptr_base(element_type *ptr) : oid(pmemobj_oid(ptr))
    {
        verify_type();
    }
 
    template <typename U,
          typename = typename std::enable_if<
              !std::is_same<T, U>::value &&
              std::is_same<typename std::remove_cv<T>::type,
                       U>::value>::type>
    persistent_ptr_base(persistent_ptr_base<U> const &r) noexcept
        : oid(r.oid)
    {
        this->oid.off +=
            static_cast<std::uint64_t>(calculate_offset<U>());
        verify_type();
    }
 
    template <
        typename U, typename Dummy = void,
        typename = typename std::enable_if<
            !std::is_same<
                typename std::remove_cv<T>::type,
                typename std::remove_cv<U>::type>::value &&
                !std::is_void<U>::value,
            decltype(static_cast<T *>(std::declval<U *>()))>::type>
    persistent_ptr_base(persistent_ptr_base<U> const &r) noexcept
        : oid(r.oid)
    {
        this->oid.off +=
            static_cast<std::uint64_t>(calculate_offset<U>());
        verify_type();
    }
 
    template <
        typename Y,
        typename = typename std::enable_if<
            !std::is_same<
                typename std::remove_cv<T>::type,
                typename std::remove_cv<Y>::type>::value &&
                !std::is_void<Y>::value,
            decltype(static_cast<T *>(std::declval<Y *>()))>::type>
    operator persistent_ptr_base<Y>() noexcept
    {
        /*
         * The offset conversion should not be required here.
         */
        return persistent_ptr_base<Y>(this->oid);
    }
 
    /*
     * Copy constructor.
     *
     * @param r Persistent pointer to the same type.
     */
    persistent_ptr_base(persistent_ptr_base const &r) noexcept : oid(r.oid)
    {
        verify_type();
    }
 
    persistent_ptr_base(persistent_ptr_base &&r) noexcept
        : oid(std::move(r.oid))
    {
        verify_type();
    }
 
    persistent_ptr_base &
    operator=(persistent_ptr_base &&r)
    {
        detail::conditional_add_to_tx(this);
        this->oid = std::move(r.oid);
 
        return *this;
    }
 
    persistent_ptr_base &
    operator=(persistent_ptr_base const &r)
    {
        this_type(r).swap(*this);
 
        return *this;
    }
 
    persistent_ptr_base &
    operator=(std::nullptr_t &&)
    {
        detail::conditional_add_to_tx(this);
        this->oid = {0, 0};
        return *this;
    }
 
    template <typename Y,
          typename = typename std::enable_if<
              std::is_convertible<Y *, T *>::value>::type>
    persistent_ptr_base &
    operator=(persistent_ptr_base<Y> const &r)
    {
        this_type(r).swap(*this);
 
        return *this;
    }
 
    void
    swap(persistent_ptr_base &other)
    {
        detail::conditional_add_to_tx(this);
        detail::conditional_add_to_tx(&other);
        std::swap(this->oid, other.oid);
    }
 
    element_type *
    get() const noexcept
    {
        if (this->oid.pool_uuid_lo ==
            std::numeric_limits<decltype(oid.pool_uuid_lo)>::max())
            return reinterpret_cast<element_type *>(oid.off);
        else
            return static_cast<element_type *>(
                pmemobj_direct(this->oid));
    }
 
    const PMEMoid &
    raw() const noexcept
    {
        return this->oid;
    }
 
    PMEMoid *
    raw_ptr() noexcept
    {
        return &(this->oid);
    }
 
    /*
     * Bool conversion operator.
     */
    explicit operator bool() const noexcept
    {
        return get() != nullptr;
    }
 
protected:
    /* The underlying PMEMoid of the held object. */
    PMEMoid oid;
 
    void
    verify_type()
    {
        static_assert(!std::is_polymorphic<element_type>::value,
                  "Polymorphic types are not supported");
    }
 
    persistent_ptr_base(element_type *vptr, int) : persistent_ptr_base(vptr)
    {
        if (OID_IS_NULL(oid)) {
            oid.pool_uuid_lo = std::numeric_limits<decltype(
                oid.pool_uuid_lo)>::max();
            oid.off = reinterpret_cast<decltype(oid.off)>(vptr);
        }
    }
 
    template <typename U>
    inline ptrdiff_t
    calculate_offset() const
    {
        static const ptrdiff_t ptr_offset_magic = 0xF00000000000000;
 
        static_assert(ptr_offset_magic % alignof(U) == 0, "");
        static_assert(ptr_offset_magic % alignof(T) == 0, "");
 
        U *tmp{reinterpret_cast<U *>(ptr_offset_magic)};
        T *diff = static_cast<T *>(tmp);
        return reinterpret_cast<ptrdiff_t>(diff) -
            reinterpret_cast<ptrdiff_t>(tmp);
    }
};
 
} /* namespace detail */
 
} /* namespace pmem */
 
#endif /* LIBPMEMOBJ_CPP_PERSISTENT_PTR_BASE_HPP */