/***************************************************************************
* Copyright (c) 2016, Johan Mabille and Sylvain Corlay                     *
*                                                                          *
* Distributed under the terms of the BSD 3-Clause License.                 *
*                                                                          *
* The full license is in the file LICENSE, distributed with this software. *
****************************************************************************/

#ifndef XSIMD_ALIGNED_ALLOCATOR_HPP
#define XSIMD_ALIGNED_ALLOCATOR_HPP

#include <algorithm>
#include <memory>
#include <cstddef>
#include <stdlib.h>

#include "../config/xsimd_align.hpp"

#if defined(XSIMD_ALLOCA)
#if defined(__GNUC__)
#include <alloca.h>
#elif defined(_MSC_VER)
#include <malloc.h>
#endif
#endif

namespace xsimd
{

    /**
     * @class aligned_allocator
     * @brief Allocator for aligned memory
     *
     * The aligned_allocator class template is an allocator that
     * performs memory allocation aligned by the specified value.
     *
     * @tparam T type of objects to allocate.
     * @tparam Align alignment in bytes.
     */
    template <class T, size_t Align>
    class aligned_allocator
    {
    public:

        using value_type = T;
        using pointer = T*;
        using const_pointer = const T*;
        using reference = T&;
        using const_reference = const T&;
        using size_type = size_t;
        using difference_type = ptrdiff_t;

        static constexpr size_t alignment = Align;

        template <class U>
        struct rebind
        {
            using other = aligned_allocator<U, Align>;
        };

        aligned_allocator() noexcept;
        aligned_allocator(const aligned_allocator& rhs) noexcept;

        template <class U>
        aligned_allocator(const aligned_allocator<U, Align>& rhs) noexcept;

        ~aligned_allocator();

        pointer address(reference) noexcept;
        const_pointer address(const_reference) const noexcept;

        pointer allocate(size_type n, typename std::allocator<void>::const_pointer hint = 0);
        void deallocate(pointer p, size_type n);

        size_type max_size() const noexcept;
        size_type size_max() const noexcept;

        template <class U, class... Args>
        void construct(U* p, Args&&... args);

        template <class U>
        void destroy(U* p);
    };

    template <class T1, size_t Align1, class T2, size_t Align2>
    bool operator==(const aligned_allocator<T1, Align1>& lhs,
                    const aligned_allocator<T2, Align2>& rhs) noexcept;

    template <class T1, size_t Align1, class T2, size_t Align2>
    bool operator!=(const aligned_allocator<T1, Align1>& lhs,
                    const aligned_allocator<T2, Align2>& rhs) noexcept;


    void* aligned_malloc(size_t size, size_t alignment);
    void aligned_free(void* ptr);

    template <class T>
    size_t get_alignment_offset(const T* p, size_t size, size_t block_size);


    /************************************
     * aligned_allocator implementation *
     ************************************/

    /**
     * Default constructor.
     */
    template <class T, size_t A>
    inline aligned_allocator<T, A>::aligned_allocator() noexcept
    {
    }

    /**
     * Copy constructor.
     */
    template <class T, size_t A>
    inline aligned_allocator<T, A>::aligned_allocator(const aligned_allocator&) noexcept
    {
    }

    /**
     * Extended copy constructor.
     */
    template <class T, size_t A>
    template <class U>
    inline aligned_allocator<T, A>::aligned_allocator(const aligned_allocator<U, A>&) noexcept
    {
    }

    /**
     * Destructor.
     */
    template <class T, size_t A>
    inline aligned_allocator<T, A>::~aligned_allocator()
    {
    }

    /**
     * Returns the actual address of \c r even in presence of overloaded \c operator&.
     * @param r the object to acquire address of.
     * @return the actual address of \c r.
     */
    template <class T, size_t A>
    inline auto
    aligned_allocator<T, A>::address(reference r) noexcept -> pointer
    {
        return &r;
    }

    /**
     * Returns the actual address of \c r even in presence of overloaded \c operator&.
     * @param r the object to acquire address of.
     * @return the actual address of \c r.
     */
    template <class T, size_t A>
    inline auto
    aligned_allocator<T, A>::address(const_reference r) const noexcept -> const_pointer
    {
        return &r;
    }

    /**
     * Allocates <tt>n * sizeof(T)</tt> bytes of uninitialized memory, aligned by \c A.
     * The alignment may require some extra memory allocation.
     * @param n the number of objects to allocate storage for.
     * @param hint unused parameter provided for standard compliance.
     * @return a pointer to the first byte of a memory block suitably aligned and sufficient to
     * hold an array of \c n objects of type \c T.
     */
    template <class T, size_t A>
    inline auto
    aligned_allocator<T, A>::allocate(size_type n,
            typename std::allocator<void>::const_pointer) -> pointer
    {
        pointer res = reinterpret_cast<pointer>(aligned_malloc(sizeof(T) * n, A));
        if (res == nullptr)
            throw std::bad_alloc();
        return res;
    }

    /**
     * Deallocates the storage referenced by the pointer p, which must be a pointer obtained by
     * an earlier call to allocate(). The argument \c n must be equal to the first argument of the call
     * to allocate() that originally produced \c p; otherwise, the behavior is undefined.
     * @param p pointer obtained from allocate().
     * @param n number of objects earlier passed to allocate().
     */
    template <class T, size_t A>
    inline void aligned_allocator<T, A>::deallocate(pointer p, size_type)
    {
        aligned_free(p);
    }

    /**
     * Returns the maximum theoretically possible value of \c n, for which the
     * call allocate(n, 0) could succeed.
     * @return the maximum supported allocated size.
     */
    template <class T, size_t A>
    inline auto
    aligned_allocator<T, A>::max_size() const noexcept -> size_type
    {
        return size_type(-1) / sizeof(T);
    }

    /**
     * This method is deprecated, use max_size() instead
     */
    template <class T, size_t A>
    inline auto
    aligned_allocator<T, A>::size_max() const noexcept -> size_type
    {
        return size_type(-1) / sizeof(T);
    }

    /**
     * Constructs an object of type \c T in allocated uninitialized memory
     * pointed to by \c p, using placement-new.
     * @param p pointer to allocated uninitialized memory.
     * @param args the constructor arguments to use.
     */
    template <class T, size_t A>
    template <class U, class... Args>
    inline void aligned_allocator<T, A>::construct(U* p, Args&&... args)
    {
        new ((void*)p) U(std::forward<Args>(args)...);
    }

    /**
     * Calls the destructor of the object pointed to by \c p.
     * @param p pointer to the object that is going to be destroyed.
     */
    template <class T, size_t A>
    template <class U>
    inline void aligned_allocator<T, A>::destroy(U* p)
    {
        p->~U();
    }

    /**
     * @defgroup allocator_comparison Comparison operators
     */

    /**
     * @ingroup allocator_comparison
     * Compares two aligned memory allocator for equality. Since allocators
     * are stateless, return \c true iff <tt>A1 == A2</tt>.
     * @param lhs aligned_allocator to compare.
     * @param rhs aligned_allocator to compare.
     * @return true if the allocators have the same alignment.
     */
    template <class T1, size_t A1, class T2, size_t A2>
    inline bool operator==(const aligned_allocator<T1, A1>& lhs,
                           const aligned_allocator<T2, A2>& rhs) noexcept
    {
        return lhs.alignment == rhs.alignment;
    }

    /**
    * @ingroup allocator_comparison
     * Compares two aligned memory allocator for inequality. Since allocators
     * are stateless, return \c true iff <tt>A1 != A2</tt>.
     * @param lhs aligned_allocator to compare.
     * @param rhs aligned_allocator to compare.
     * @return true if the allocators have different alignments.
     */
    template <class T1, size_t A1, class T2, size_t A2>
    inline bool operator!=(const aligned_allocator<T1, A1>& lhs,
                           const aligned_allocator<T2, A2>& rhs) noexcept
    {
        return !(lhs == rhs);
    }


    /****************************************
     * aligned malloc / free implementation *
     ****************************************/

    namespace detail
    {
        inline void* xaligned_malloc(size_t size, size_t alignment)
        {
            void* res = 0;
            void* ptr = malloc(size + alignment);
            if (ptr != 0)
            {
                res = reinterpret_cast<void*>(
                    (reinterpret_cast<size_t>(ptr) & ~(size_t(alignment - 1))) +
                    alignment);
                *(reinterpret_cast<void**>(res) - 1) = ptr;
            }
            return res;
        }

        inline void xaligned_free(void* ptr)
        {
            if (ptr != 0)
                free(*(reinterpret_cast<void**>(ptr) - 1));
        }
    }

    inline void* aligned_malloc(size_t size, size_t alignment)
    {
        return detail::xaligned_malloc(size, alignment);
    }

    inline void aligned_free(void* ptr)
    {
        detail::xaligned_free(ptr);
    }

    template <class T>
    inline size_t get_alignment_offset(const T* p, size_t size, size_t block_size)
    {
        // size_t block_size = simd_traits<T>::size;
        if (block_size == 1)
        {
            // The simd_block consists of exactly one scalar so that all
            // elements of the array
            // are "well" aligned.
            return 0;
        }
        else if (size_t(p) & (sizeof(T) - 1))
        {
            // The array is not aligned to the size of a single element, so that
            // no element
            // of the array is well aligned
            return size;
        }
        else
        {
            size_t block_mask = block_size - 1;
            return std::min<size_t>(
                (block_size - ((size_t(p) / sizeof(T)) & block_mask)) & block_mask,
                size);
        }
    }
}

#endif
