u_template_historybuf_const_iterator.inl

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// Copyright 2021-2022, Collabora, Ltd.
//
// SPDX-License-Identifier: BSL-1.0
/*!
 * @file
 * @brief const_iterator details for ring buffer
 * @author Rylie Pavlik <rylie.pavlik@collabora.com>
 * @ingroup aux_util
 */
#pragma once
 
// IWYU pragma: private, include "util/u_template_historybuf.hpp"
 
#include <stddef.h>
#include <type_traits>
 
namespace xrt::auxiliary::util {
template <typename T, size_t MaxSize> class HistoryBuffer;
 
namespace detail {
        /**
         * @brief Class template for const_iterator for HistoryBuffer
         *
         * @tparam T Container element type - must match HistoryBuffer
         * @tparam MaxSize Maximum number of elements - must match HistoryBuffer
         */
        template <typename T, size_t MaxSize>
        class HistoryBufConstIterator : public RandomAccessIteratorBase<const RingBufferHelper>
        {
                using base = RandomAccessIteratorBase<const RingBufferHelper>;
                friend class HistoryBuffer<T, MaxSize>;
                friend class HistoryBufIterator<T, MaxSize>;
 
        public:
                using Self = HistoryBufConstIterator<T, MaxSize>;
                using container_type = const HistoryBuffer<T, MaxSize>;
                using typename base::difference_type;
                using typename base::iterator_category;
                using value_type = const T;
                using pointer = const T *;
                using reference = const T &;
 
                //! Default-construct an (invalid) iterator.
                HistoryBufConstIterator() = default;
 
                // copy and move as you wish
                HistoryBufConstIterator(HistoryBufConstIterator const &) = default;
                HistoryBufConstIterator(HistoryBufConstIterator &&) noexcept = default;
                HistoryBufConstIterator &
                operator=(HistoryBufConstIterator const &) = default;
                HistoryBufConstIterator &
                operator=(HistoryBufConstIterator &&) noexcept = default;
 
                //! Implicit conversion from a non-const iterator
                HistoryBufConstIterator(const HistoryBufIterator<T, MaxSize> &other);
 
                //! Is this iterator valid?
                bool
                valid() const noexcept
                {
                        return container_ != nullptr && base::valid();
                }
 
                //! Is this iterator valid?
                explicit operator bool() const noexcept
                {
                        return valid();
                }
 
                //! Get the inner container: for internal use
                container_type *
                container() const noexcept
                {
                        return container_;
                }
 
                //! Dereference operator: throws std::out_of_range if invalid
                reference
                operator*() const;
 
                //! Smart pointer operator: returns nullptr if invalid
                pointer
                operator->() const noexcept;
 
                //! Pre-increment: Advance, then return self.
                Self &
                operator++();
 
                //! Post-increment: return a copy of initial state after incrementing self
                // NOLINTNEXTLINE(cert-dcl21-cpp)
                Self
                operator++(int) &
                {
                        Self tmp = *this;
                        this->increment_n(1);
                        return tmp;
                }
 
                //! Pre-decrement: Subtract, then return self.
                Self &
                operator--();
 
                //! Post-decrement: return a copy of initial state after decrementing self
                // NOLINTNEXTLINE(cert-dcl21-cpp)
                Self
                operator--(int) &
                {
                        Self tmp = *this;
                        this->decrement_n(1);
                        return tmp;
                }
 
                // Use the base class implementation of subtracting one iterator from another
                using base::operator-;
 
                //! Increment by an arbitrary amount.
                Self &
                operator+=(std::ptrdiff_t n) noexcept;
 
                //! Decrement by an arbitrary amount.
                Self &
                operator-=(std::ptrdiff_t n) noexcept;
 
                //! Increment a copy of the iterator by an arbitrary amount.
                Self
                operator+(std::ptrdiff_t n) const noexcept;
 
                //! Decrement a copy of the iterator by an arbitrary amount.
                Self
                operator-(std::ptrdiff_t n) const noexcept;
 
        private:
                //! Factory for a "begin" iterator from a container and its helper: mostly for internal use.
                static Self
                begin(container_type &container, const RingBufferHelper &helper)
                {
                        return {&container, base::begin(helper)};
                }
 
                //! Construct the "past the end" iterator that can be decremented safely
                static Self
                end(container_type &container, const RingBufferHelper &helper)
                {
                        return {&container, base::end(helper)};
                }
 
                // for use internally
                HistoryBufConstIterator(container_type *container, base &&iter_base)
                    : base(iter_base), container_(container)
                {}
                container_type *container_{nullptr};
        };
 
        template <typename T, size_t MaxSize>
        inline typename HistoryBufConstIterator<T, MaxSize>::reference
        HistoryBufConstIterator<T, MaxSize>::operator*() const
        {
                auto *ptr = container_->get_at_index(base::index());
                if (ptr == nullptr) {
                        throw std::out_of_range("Iterator index out of range");
                }
                return *ptr;
        }
 
        template <typename T, size_t MaxSize>
        inline typename HistoryBufConstIterator<T, MaxSize>::pointer
        HistoryBufConstIterator<T, MaxSize>::operator->() const noexcept
        {
                return container_->get_at_index(base::index());
        }
 
        template <typename T, size_t MaxSize>
        inline HistoryBufConstIterator<T, MaxSize> &
        HistoryBufConstIterator<T, MaxSize>::operator++()
        {
                this->increment_n(1);
                return *this;
        }
 
        template <typename T, size_t MaxSize>
        inline HistoryBufConstIterator<T, MaxSize> &
        HistoryBufConstIterator<T, MaxSize>::operator--()
        {
                this->decrement_n(1);
                return *this;
        }
 
        template <typename T, size_t MaxSize>
        inline HistoryBufConstIterator<T, MaxSize> &
        HistoryBufConstIterator<T, MaxSize>::operator+=(std::ptrdiff_t n) noexcept
        {
                static_cast<base &>(*this) += n;
                return *this;
        }
 
        template <typename T, size_t MaxSize>
        inline HistoryBufConstIterator<T, MaxSize> &
        HistoryBufConstIterator<T, MaxSize>::operator-=(std::ptrdiff_t n) noexcept
        {
                static_cast<base &>(*this) -= n;
                return *this;
        }
 
        template <typename T, size_t MaxSize>
        inline HistoryBufConstIterator<T, MaxSize>
        HistoryBufConstIterator<T, MaxSize>::operator+(std::ptrdiff_t n) const noexcept
        {
                Self ret(*this);
                ret += n;
                return ret;
        }
 
        template <typename T, size_t MaxSize>
        inline HistoryBufConstIterator<T, MaxSize>
        HistoryBufConstIterator<T, MaxSize>::operator-(std::ptrdiff_t n) const noexcept
        {
                Self ret(*this);
                ret -= n;
                return ret;
        }
} // namespace detail
 
// HistoryBuffer method implementations that depend on const_iterator availability
 
template <typename T, size_t MaxSize>
inline typename HistoryBuffer<T, MaxSize>::const_iterator
HistoryBuffer<T, MaxSize>::cbegin() const noexcept
{
        static_assert(std::is_same<typename std::iterator_traits<const_iterator>::iterator_category,
                                   std::random_access_iterator_tag>::value,
                      "Iterator should be random access");
        return const_iterator::begin(*this, helper_);
}
 
template <typename T, size_t MaxSize>
inline typename HistoryBuffer<T, MaxSize>::const_iterator
HistoryBuffer<T, MaxSize>::cend() const noexcept
{
        return const_iterator::end(*this, helper_);
}
 
template <typename T, size_t MaxSize>
inline typename HistoryBuffer<T, MaxSize>::const_iterator
HistoryBuffer<T, MaxSize>::begin() const noexcept
{
        return cbegin();
}
 
template <typename T, size_t MaxSize>
inline typename HistoryBuffer<T, MaxSize>::const_iterator
HistoryBuffer<T, MaxSize>::end() const noexcept
{
        return cend();
}
 
} // namespace xrt::auxiliary::util