array

/*  This file is part of the Vc library. {{{
Copyright © 2015 Matthias Kretz <kretz@kde.org>

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 names of contributing organizations 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 LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
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}}}*/
//===---------------------------- array -----------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef VC_INCLUDE_VC_ARRAY_
#define VC_INCLUDE_VC_ARRAY_

#include <type_traits>
#include <utility>
#include <iterator>
#include <algorithm>
#include <stdexcept>

#include "common/subscript.h"

namespace Vc_VERSIONED_NAMESPACE
{
/**
 * \ingroup Containers
 * This is `std::array` with additional subscript operators supporting gather and scatter operations.
 *
 * The [std::array](https://en.cppreference.com/w/cpp/container/array) documentation applies.
 *
 * Gathers from structured data (AoS: arrays of struct) are possible via a special
 * subscript operator.
 * Example:
 * \code
 * Vc::array<float, 100> data;
 * std::iota(data.begin(), data.end(), 0.f);  // fill with values 0, 1, 2, ...
 * auto indexes = float_v::IndexType::IndexesFromZero();
 * float_v gathered = data[indexes];  // gathered == [0, 1, 2, ...]
 * \endcode
 *
 * This also works for gathers into arrays of structures:
 * \code
 * struct Point { float x, y, z; };
 * Vc::array<Point, 100> points;
 * // fill points ...
 * auto indexes = float_v::IndexType::IndexesFromZero();
 * float_v xs = data[indexes][&Point::x];  // [points[0].x, points[1].x, points[2].x, ...]
 * float_v ys = data[indexes][&Point::y];  // [points[0].y, points[1].y, points[2].y, ...]
 * float_v zs = data[indexes][&Point::z];  // [points[0].z, points[1].z, points[2].z, ...]
 * \endcode
 *
 * Arrays may also be nested:
 * \code:
 * Vc::array<Vc::array<float, 3>, 100> points;
 * // fill points ...
 * auto indexes = float_v::IndexType::IndexesFromZero();
 * float_v xs = data[indexes][0];  // [points[0][0], points[1][0], points[2][0], ...]
 * float_v ys = data[indexes][1];  // [points[0][1], points[1][1], points[2][1], ...]
 * float_v zs = data[indexes][2];  // [points[0][2], points[1][2], points[2][2], ...]
 * \endcode
 */
template <class T, size_t Size> struct array {
    // types:
    typedef array self_;
    typedef T value_type;
    typedef value_type& reference;
    typedef const value_type& const_reference;
    typedef value_type* iterator;
    typedef const value_type* const_iterator;
    typedef value_type* pointer;
    typedef const value_type* const_pointer;
    typedef size_t size_type;
    typedef ptrdiff_t difference_type;
    typedef std::reverse_iterator<iterator> reverse_iterator;
    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;

    value_type elems_[Size > 0 ? Size : 1];

    // No explicit construct/copy/destroy for aggregate type
    void fill(const value_type& u_) { std::fill_n(elems_, Size, u_); }
    void swap(array& a_) noexcept(std::swap(std::declval<T &>(), std::declval<T &>()))
    {
        std::swap_ranges(elems_, elems_ + Size, a_.elems_);
    }

    // iterators:
    iterator begin() noexcept { return iterator(elems_); }
    const_iterator begin() const noexcept { return const_iterator(elems_); }
    iterator end() noexcept { return iterator(elems_ + Size); }
    const_iterator end() const noexcept { return const_iterator(elems_ + Size); }
    reverse_iterator rbegin() noexcept { return reverse_iterator(end()); }
    const_reverse_iterator rbegin() const noexcept
    {
        return const_reverse_iterator(end());
    }
    reverse_iterator rend() noexcept { return reverse_iterator(begin()); }
    const_reverse_iterator rend() const noexcept
    {
        return const_reverse_iterator(begin());
    }

    const_iterator cbegin() const noexcept { return begin(); }
    const_iterator cend() const noexcept { return end(); }
    const_reverse_iterator crbegin() const noexcept { return rbegin(); }
    const_reverse_iterator crend() const noexcept { return rend(); }
    // capacity:
    constexpr size_type size() const noexcept { return Size; }
    constexpr size_type max_size() const noexcept { return Size; }
    constexpr bool empty() const noexcept { return Size == 0; }
    // element access:
    reference operator[](size_type n_) { return elems_[n_]; }
    constexpr const_reference operator[](size_type n_) const { return elems_[n_]; }

    /**
     * \name Data-Parallel Subscripting for Gather & Scatter
     */
    ///@{
    template <typename I>
    Vc_ALWAYS_INLINE auto operator[](I&& arg_)
        -> decltype(subscript_operator(*this, std::forward<I>(arg_)))
    {
        return subscript_operator(*this, std::forward<I>(arg_));
    }

    template <typename I>
    Vc_ALWAYS_INLINE auto operator[](I&& arg_) const
        -> decltype(subscript_operator(*this, std::forward<I>(arg_)))
    {
        return subscript_operator(*this, std::forward<I>(arg_));
    }
    ///@}

    reference at(size_type n_);
    constexpr const_reference at(size_type n_) const;

    reference front() { return elems_[0]; }
    constexpr const_reference front() const { return elems_[0]; }
    reference back() { return elems_[Size > 0 ? Size - 1 : 0]; }
    constexpr const_reference back() const { return elems_[Size > 0 ? Size - 1 : 0]; }
    value_type* data() noexcept { return elems_; }
    const value_type* data() const noexcept { return elems_; }
};

template <class T, size_t Size>
typename array<T, Size>::reference array<T, Size>::at(size_type n_)
{
    if (n_ >= Size) {
        throw std::out_of_range("array::at");
    }
    return elems_[n_];
}

template <class T, size_t Size>
constexpr typename array<T, Size>::const_reference array<T, Size>::at(size_type n_) const
{
    return n_ >= Size ? (throw std::out_of_range("array::at"), elems_[0]) : elems_[n_];
}

template <class T, size_t Size>
inline bool operator==(const array<T, Size>& x_, const array<T, Size>& y_)
{
    return std::equal(x_.elems_, x_.elems_ + Size, y_.elems_);
}

template <class T, size_t Size>
inline bool operator!=(const array<T, Size>& x_, const array<T, Size>& y_)
{
    return !(x_ == y_);
}

template <class T, size_t Size>
inline bool operator<(const array<T, Size>& x_, const array<T, Size>& y_)
{
    return std::lexicographical_compare(x_.elems_, x_.elems_ + Size, y_.elems_,
                                        y_.elems_ + Size);
}

template <class T, size_t Size>
inline bool operator>(const array<T, Size>& x_, const array<T, Size>& y_)
{
    return y_ < x_;
}

template <class T, size_t Size>
inline bool operator<=(const array<T, Size>& x_, const array<T, Size>& y_)
{
    return !(y_ < x_);
}

template <class T, size_t Size>
inline bool operator>=(const array<T, Size>& x_, const array<T, Size>& y_)
{
    return !(x_ < y_);
}

/**\name non-member begin & end
 * Implement the non-member begin & end functions in the %Vc namespace so that ADL works
 * and `begin(some_vc_array)` always works.
 */
///@{
template <typename T, std::size_t N>
inline auto begin(array<T, N>& arr) -> decltype(arr.begin())
{
    return arr.begin();
}
template <typename T, std::size_t N>
inline auto begin(const array<T, N>& arr) -> decltype(arr.begin())
{
    return arr.begin();
}
template <typename T, std::size_t N>
inline auto end(array<T, N>& arr) -> decltype(arr.end())
{
    return arr.end();
}
template <typename T, std::size_t N>
inline auto end(const array<T, N>& arr) -> decltype(arr.end())
{
    return arr.end();
}
///@}

namespace Traits
{
template <typename T, std::size_t N>
struct has_no_allocated_data_impl<Vc::array<T, N>> : public std::true_type
{
};
template <typename T, std::size_t N>
struct has_contiguous_storage_impl<Vc::array<T, N>> : public std::true_type
{
};
}  // namespace Traits
}  // namespace Vc

namespace std
{
template <class T, size_t Size>
inline
#ifdef Vc_MSVC
    // MSVC fails to do SFINAE correctly and gets totally confused:
    // error C2433: 'type': 'inline' not permitted on data declarations
    // error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
    // error C2061: syntax error: identifier 'swap'
    void
#else
    typename enable_if<is_same<void, decltype(swap(declval<T&>(), declval<T&>()))>::value,
                       void>::type
#endif
    swap(const Vc::array<T, Size>& x_,
         const Vc::array<T, Size>& y_) noexcept(swap(declval<T&>(), declval<T&>()))
{
    x_.swap(y_);
}

template <class T, size_t Size>
class tuple_size<Vc::array<T, Size>> : public integral_constant<size_t, Size>
{
};

template <size_t I, class T, size_t Size> class tuple_element<I, Vc::array<T, Size>>
{
public:
    typedef T type;
};

template <size_t I, class T, size_t Size>
inline constexpr typename std::enable_if<(I < Size), T&>::type get(
    Vc::array<T, Size>& a_) noexcept
{
    return a_.elems_[I];
}

template <size_t I, class T, size_t Size>
inline constexpr typename std::enable_if<(I < Size), const T&>::type get(
    const Vc::array<T, Size>& a_) noexcept
{
    return a_.elems_[I];
}

template <size_t I, class T, size_t Size>
inline constexpr typename std::enable_if<(I < Size), T&&>::type get(
    Vc::array<T, Size>&& a_) noexcept
{
    return std::move(a_.elems_[I]);
}
}  // namespace std

#endif  // VC_INCLUDE_VC_ARRAY_

// vim: ft=cpp foldmethod=marker