segment_vector_policies.hpp

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// SPDX-License-Identifier: BSD-3-Clause
/* Copyright 2019, Intel Corporation */
 
#ifndef LIBPMEMOBJ_SEGMENT_VECTOR_POLICIES_HPP
#define LIBPMEMOBJ_SEGMENT_VECTOR_POLICIES_HPP
 
#include <libpmemobj++/container/array.hpp>
#include <libpmemobj++/container/vector.hpp>
#include <libpmemobj++/detail/template_helpers.hpp>
#include <vector>
 
namespace pmem
{
namespace obj
{
namespace segment_vector_internal
{
template <typename T>
using array_64 = array<T, 64>;
 
template <typename Container>
using resize_method =
    decltype(std::declval<Container>().resize(std::declval<size_t>()));
 
template <typename Container>
using container_has_resize = detail::supports<Container, resize_method>;
 
template <typename Container, bool = container_has_resize<Container>::value>
struct segment_vector_resize {
    using segment_vector_type = Container;
 
    static void
    resize(segment_vector_type &c, size_t n)
    {
        c.resize(n);
    }
};
 
template <typename Container>
struct segment_vector_resize<Container, false> {
    using segment_vector_type = Container;
 
    static void
    resize(segment_vector_type &c, size_t n)
    {
    }
};
 
template <template <typename> class SegmentVectorType,
      template <typename> class SegmentType, size_t SegmentSize>
class fixed_size_policy {
public:
    /* Traits */
    template <typename T>
    using segment_vector_type = SegmentVectorType<SegmentType<T>>;
 
    template <typename T>
    using segment_type = SegmentType<T>;
 
    template <typename T>
    using value_type = typename segment_type<T>::value_type;
 
    using size_type = std::size_t;
 
    template <typename T>
    using segment_vector_resize_type =
        segment_vector_resize<segment_vector_type<T>>;
 
    static constexpr size_type Size = SegmentSize;
 
    template <typename T>
    static void
    resize(segment_vector_type<T> &c, size_type n)
    {
        segment_vector_resize_type<T>::resize(c, n);
    }
 
    static size_type
    get_segment(size_type index)
    {
        return index / Size;
    }
    static size_type
    segment_top(size_type segment_index)
    {
        return segment_index * Size;
    }
    static size_type
    segment_size(size_type segment_index)
    {
        return Size;
    }
    static size_type
    index_in_segment(size_type index)
    {
        return index % Size;
    }
 
    template <typename T>
    static size_type
    max_size(const segment_vector_type<T> &seg_storage)
    {
        return seg_storage.max_size() * SegmentSize;
    }
 
    static size_type
    capacity(size_type segment_index)
    {
        return (segment_index + 1) * Size;
    }
};
 
template <template <typename> class SegmentVectorType,
      template <typename> class SegmentType>
class exponential_size_policy {
public:
    /* Traits */
    template <typename T>
    using segment_vector_type = SegmentVectorType<SegmentType<T>>;
 
    template <typename T>
    using segment_type = SegmentType<T>;
 
    template <typename T>
    using value_type = typename segment_type<T>::value_type;
 
    using size_type = std::size_t;
 
    template <typename T>
    using segment_vector_resize_type =
        segment_vector_resize<segment_vector_type<T>>;
 
    template <typename T>
    static void
    resize(segment_vector_type<T> &c, size_type n)
    {
        segment_vector_resize_type<T>::resize(c, n);
    }
 
    static size_type
    get_segment(size_type index)
    {
        return static_cast<size_type>(detail::Log2(index | 1));
    }
    static size_type
    segment_top(size_type segment_index)
    {
        return (size_type(1) << segment_index) & ~size_type(1);
    }
    static size_type
    segment_size(size_type segment_index)
    {
        return (segment_index == 0) ? 2 : segment_top(segment_index);
    }
    static size_type
    index_in_segment(size_type index)
    {
        return index - segment_top(get_segment(index));
    }
 
    template <typename T>
    static size_t
    max_size(const segment_vector_type<T> &)
    {
        return segment_size(get_segment(PMEMOBJ_MAX_ALLOC_SIZE /
                        sizeof(value_type<T>)) +
                    1);
    }
 
    static size_type
    capacity(size_type segment_index)
    {
        if (segment_index == 0)
            return 2;
        return segment_size(segment_index) * 2;
    }
};
 
} /* segment_vector_internal namespace */
} /* namespace obj */
} /* namespace pmem */
 
#endif /* LIBPMEMOBJ_SEGMENT_VECTOR_POLICIES_HPP */