cache_aligning_allocator.hpp

/* Copyright 2009-2017 Francesco Biscani (bluescarni@gmail.com)

This file is part of the Piranha library.

The Piranha library is free software; you can redistribute it and/or modify
it under the terms of either:

  * the GNU Lesser General Public License as published by the Free
    Software Foundation; either version 3 of the License, or (at your
    option) any later version.

or

  * the GNU General Public License as published by the Free Software
    Foundation; either version 3 of the License, or (at your option) any
    later version.

or both in parallel, as here.

The Piranha library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received copies of the GNU General Public License and the
GNU Lesser General Public License along with the Piranha library.  If not,
see https://www.gnu.org/licenses/. */

#ifndef PIRANHA_CACHE_ALIGNING_ALLOCATOR_HPP
#define PIRANHA_CACHE_ALIGNING_ALLOCATOR_HPP

#include <cstddef>
#include <utility>

#include <piranha/dynamic_aligning_allocator.hpp>
#include <piranha/memory.hpp>
#include <piranha/safe_cast.hpp>
#include <piranha/settings.hpp>

namespace piranha
{


template <typename T>
class cache_aligning_allocator : public dynamic_aligning_allocator<T>
{
    using base = dynamic_aligning_allocator<T>;
    static std::size_t determine_alignment()
    {
#if !defined(PIRANHA_HAVE_MEMORY_ALIGNMENT_PRIMITIVES)
        return 0u;
#endif
        try {
            const std::size_t alignment = safe_cast<std::size_t>(settings::get_cache_line_size());
            if (!alignment_check<T>(alignment)) {
                return 0u;
            }
            return alignment;
        } catch (...) {
            return 0u;
        }
    }

public:
    // NOTE: these members (down to the default ctor) are not needed according
    // to the C++11 standard, but GCC's stdlib does not support allocator aware
    // containers yet.
    template <typename U>
    struct rebind {
        using other = cache_aligning_allocator<U>;
    };
    using pointer = T *;
    using const_pointer = T const *;
    using reference = T &;
    using const_reference = T const &;

    void destroy(pointer p)
    {
        p->~T();
    }

    // NOTE: here, according to the standard, the allocator must be
    // able to construct objects of arbitrary type:
    // http://en.cppreference.com/w/cpp/concept/Allocator
    template <typename U, typename... Args>
    void construct(U *p, Args &&... args)
    {
        ::new (static_cast<void *>(p)) U(std::forward<Args>(args)...);
    }

    cache_aligning_allocator() : base(determine_alignment())
    {
    }
    cache_aligning_allocator(const cache_aligning_allocator &) = default;
    cache_aligning_allocator(cache_aligning_allocator &&) = default;

    template <typename U>
    explicit cache_aligning_allocator(const cache_aligning_allocator<U> &other) : base(other)
    {
    }

    template <typename U>
    explicit cache_aligning_allocator(cache_aligning_allocator<U> &&other) : base(std::move(other))
    {
    }
    ~cache_aligning_allocator() = default;

    cache_aligning_allocator &operator=(const cache_aligning_allocator &other) = default;

    cache_aligning_allocator &operator=(cache_aligning_allocator &&other) = default;
};
}

#endif