aligned_allocator.hpp

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// SPDX-FileCopyrightText: 2006-2025 Knut Reinert & Freie Universität Berlin
// SPDX-FileCopyrightText: 2016-2025 Knut Reinert & MPI für molekulare Genetik
// SPDX-License-Identifier: BSD-3-Clause

 
#pragma once
 
#include <algorithm>
#include <limits>
#include <memory>
#include <type_traits>
 
#include <seqan3/core/platform.hpp>
 
namespace seqan3
{

template <typename value_t, size_t alignment_v = __STDCPP_DEFAULT_NEW_ALIGNMENT__>
class aligned_allocator
{
public:
    static constexpr size_t alignment = alignment_v;

    using value_type = value_t;
    using pointer = value_type *;
    using difference_type = typename std::pointer_traits<pointer>::difference_type;
    using size_type = std::make_unsigned_t<difference_type>;

    using is_always_equal = std::true_type;

    aligned_allocator() = default;                                      
    aligned_allocator(aligned_allocator const &) = default;             
    aligned_allocator(aligned_allocator &&) = default;                  
    aligned_allocator & operator=(aligned_allocator const &) = default; 
    aligned_allocator & operator=(aligned_allocator &&) = default;      
    ~aligned_allocator() = default;                                     

    template <class other_value_type, size_t other_alignment>
    constexpr aligned_allocator(aligned_allocator<other_value_type, other_alignment> const &) noexcept
    {}


    [[nodiscard]] pointer allocate(size_type const n) const
    {
        constexpr size_type max_size = std::numeric_limits<size_type>::max() / sizeof(value_type);
        if (n > max_size)
            throw std::bad_alloc{};
 
        size_t bytes_to_allocate = n * sizeof(value_type);
        if constexpr (alignment <= __STDCPP_DEFAULT_NEW_ALIGNMENT__)
            return static_cast<pointer>(::operator new(bytes_to_allocate));
        else // Use alignment aware allocator function.
            return static_cast<pointer>(::operator new(bytes_to_allocate, static_cast<std::align_val_t>(alignment)));
    }

    void deallocate(pointer const p, size_type const n) const noexcept
    {
        size_t bytes_to_deallocate = n * sizeof(value_type);
 
        if constexpr (alignment <= __STDCPP_DEFAULT_NEW_ALIGNMENT__)
            ::operator delete(p, bytes_to_deallocate);
        else // Use alignment aware deallocator function.
            ::operator delete(p, bytes_to_deallocate, static_cast<std::align_val_t>(alignment));
    }

    template <typename new_value_type>
    struct rebind
    {
        static constexpr size_t other_alignment = std::max(alignof(new_value_type), alignment);
        using other = aligned_allocator<new_value_type, other_alignment>;
    };

    template <class value_type2, size_t alignment2>
    constexpr bool operator==(aligned_allocator<value_type2, alignment2> const &) noexcept
    {
        return alignment == alignment2;
    }

    template <class value_type2, size_t alignment2>
    constexpr bool operator!=(aligned_allocator<value_type2, alignment2> const &) noexcept
    {
        return alignment != alignment2;
    }

};
 
} // namespace seqan3