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Telegram/ThirdParty/range-v3/include/range/v3/view/stride.hpp

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+/// \file
+// Range v3 library
+//
+//  Copyright Eric Niebler 2013-present
+//  Copyright Casey Carter 2017
+//
+//  Use, modification and distribution is subject to the
+//  Boost Software License, Version 1.0. (See accompanying
+//  file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+//
+// Project home: https://github.com/ericniebler/range-v3
+//
+
+#ifndef RANGES_V3_VIEW_STRIDE_HPP
+#define RANGES_V3_VIEW_STRIDE_HPP
+
+#include <type_traits>
+#include <utility>
+
+#include <meta/meta.hpp>
+
+#include <range/v3/range_fwd.hpp>
+
+#include <range/v3/functional/bind_back.hpp>
+#include <range/v3/iterator/operations.hpp>
+#include <range/v3/range/access.hpp>
+#include <range/v3/range/concepts.hpp>
+#include <range/v3/range/primitives.hpp>
+#include <range/v3/range/traits.hpp>
+#include <range/v3/utility/static_const.hpp>
+#include <range/v3/view/adaptor.hpp>
+#include <range/v3/view/all.hpp>
+#include <range/v3/view/view.hpp>
+
+#include <range/v3/detail/prologue.hpp>
+
+namespace ranges
+{
+    /// \cond
+    template<typename Rng>
+    struct stride_view;
+
+    namespace detail
+    {
+        template<typename Rng>
+        using stride_view_adaptor =
+            view_adaptor<stride_view<Rng>, Rng,
+                         is_finite<Rng>::value ? finite : range_cardinality<Rng>::value>;
+
+        // Bidirectional stride views need to remember the distance between
+        // the penultimate iterator and the last iterator - which may be less
+        // than the stride - so that decrementing an last iterator properly
+        // produces the penultimate iterator. stride_view_base specializes on
+        // that distinction so that only Bidirectional stride views have the
+        // data member "offset_".
+        template<typename Rng, bool BidiRange>
+        struct stride_view_base_;
+        template<typename Rng>
+        using stride_view_base = stride_view_base_<Rng, (bool)bidirectional_range<Rng>>;
+
+        template<typename Rng, bool /*= bidirectional_range<Rng>*/>
+        struct stride_view_base_ : stride_view_adaptor<Rng>
+        {
+            stride_view_base_() = default;
+            constexpr stride_view_base_(Rng && rng, range_difference_t<Rng> const stride)
+              : stride_view_adaptor<Rng>{std::move(rng)}
+              , stride_{(RANGES_EXPECT(0 < stride), stride)}
+              , offset_{calc_offset(meta::bool_<sized_range<Rng>>{})}
+            {}
+
+        protected:
+            constexpr void set_offset(range_difference_t<Rng> const delta) noexcept
+            {
+                RANGES_EXPECT(0 <= delta && delta < stride_);
+                if(0 > offset_)
+                    offset_ = delta;
+                else
+                    RANGES_EXPECT(offset_ == delta);
+            }
+            constexpr void set_offset(range_difference_t<Rng> const) const noexcept
+            {}
+            constexpr range_difference_t<Rng> get_offset(bool check = true) const noexcept
+            {
+                RANGES_EXPECT(!check || 0 <= offset_);
+                return offset_;
+            }
+
+            range_difference_t<Rng> stride_;
+            range_difference_t<Rng> offset_ = -1;
+
+        private:
+            constexpr range_difference_t<Rng> calc_offset(std::true_type)
+            {
+                if(auto const rem = ranges::distance(this->base()) % stride_)
+                    return stride_ - rem;
+                else
+                    return 0;
+            }
+            constexpr range_difference_t<Rng> calc_offset(std::false_type) const noexcept
+            {
+                return -1;
+            }
+        };
+
+        template<typename Rng>
+        struct stride_view_base_<Rng, false> : stride_view_adaptor<Rng>
+        {
+            stride_view_base_() = default;
+            constexpr stride_view_base_(Rng && rng, range_difference_t<Rng> const stride)
+              : stride_view_adaptor<Rng>{std::move(rng)}
+              , stride_{(RANGES_EXPECT(0 < stride), stride)}
+            {}
+
+        protected:
+            constexpr void set_offset(range_difference_t<Rng> const) const noexcept
+            {}
+            constexpr range_difference_t<Rng> get_offset(bool = true) const noexcept
+            {
+                return 0;
+            }
+
+            range_difference_t<Rng> stride_;
+        };
+    } // namespace detail
+    /// \endcond
+
+    /// \addtogroup group-views
+    /// @{
+    template<typename Rng>
+    struct stride_view : detail::stride_view_base<Rng>
+    {
+    private:
+        friend range_access;
+
+        // stride_view const models Range if Rng const models Range, and
+        // either (1) Rng is sized, so we can pre-calculate offset_, or (2)
+        // Rng is !Bidirectional, so it does not need offset_.
+        static constexpr bool const_iterable() noexcept
+        {
+            return range<Rng const> &&
+                   (sized_range<Rng const> || !bidirectional_range<Rng const>);
+        }
+
+        // If the underlying range doesn't model common_range, then we can't
+        // decrement the last and there's no reason to adapt the sentinel. Strictly
+        // speaking, we don't have to adapt the last iterator of input and forward
+        // ranges, but in the interests of making the resulting stride view model
+        // common_range, adapt it anyway.
+        template<bool Const>
+        static constexpr bool can_bound() noexcept
+        {
+            using CRng = meta::const_if_c<Const, Rng>;
+            return common_range<CRng> &&
+                   (sized_range<CRng> || !bidirectional_range<CRng>);
+        }
+
+        template<bool Const>
+        struct adaptor : adaptor_base
+        {
+        private:
+            friend struct adaptor<!Const>;
+            using CRng = meta::const_if_c<Const, Rng>;
+            using stride_view_t = meta::const_if_c<Const, stride_view>;
+            stride_view_t * rng_;
+
+        public:
+            adaptor() = default;
+            constexpr adaptor(stride_view_t * rng) noexcept
+              : rng_(rng)
+            {}
+            template(bool Other)(
+                requires Const AND CPP_NOT(Other)) //
+            adaptor(adaptor<Other> that)
+              : rng_(that.rng_)
+            {}
+            constexpr void next(iterator_t<CRng> & it)
+            {
+                auto const last = ranges::end(rng_->base());
+                RANGES_EXPECT(it != last);
+                auto const delta = ranges::advance(it, rng_->stride_, last);
+                if(it == last)
+                {
+                    rng_->set_offset(delta);
+                }
+            }
+            CPP_member
+            constexpr auto prev(iterator_t<CRng> & it) //
+                -> CPP_ret(void)(
+                    requires bidirectional_range<CRng>)
+            {
+                RANGES_EXPECT(it != ranges::begin(rng_->base()));
+                auto delta = -rng_->stride_;
+                if(it == ranges::end(rng_->base()))
+                {
+                    RANGES_EXPECT(rng_->get_offset() >= 0);
+                    delta += rng_->get_offset();
+                }
+                ranges::advance(it, delta);
+            }
+            template(typename Other)(
+                requires sized_sentinel_for<Other, iterator_t<CRng>>)
+            constexpr range_difference_t<Rng> distance_to(iterator_t<CRng> const & here,
+                                                          Other const & there) const
+            {
+                range_difference_t<Rng> delta = there - here;
+                if(delta < 0)
+                    delta -= rng_->stride_ - 1;
+                else
+                    delta += rng_->stride_ - 1;
+                return delta / rng_->stride_;
+            }
+            CPP_member
+            constexpr auto advance(iterator_t<CRng> & it, range_difference_t<Rng> n) //
+                -> CPP_ret(void)(
+                    requires random_access_range<CRng>)
+            {
+                if(0 == n)
+                    return;
+                n *= rng_->stride_;
+                auto const last = ranges::end(rng_->base());
+                if(it == last)
+                {
+                    RANGES_EXPECT(n < 0);
+                    RANGES_EXPECT(rng_->get_offset() >= 0);
+                    n += rng_->get_offset();
+                }
+                if(0 < n)
+                {
+                    auto delta = ranges::advance(it, n, last);
+                    if(it == last)
+                    {
+                        // advance hit the last of the base range.
+                        rng_->set_offset(delta % rng_->stride_);
+                    }
+                }
+                else if(0 > n)
+                {
+#ifdef NDEBUG
+                    ranges::advance(it, n);
+#else
+                    auto const first = ranges::begin(rng_->base());
+                    auto const delta = ranges::advance(it, n, first);
+                    RANGES_EXPECT(delta == 0);
+#endif
+                }
+            }
+        };
+        constexpr adaptor<false> begin_adaptor() noexcept
+        {
+            return adaptor<false>{this};
+        }
+        CPP_member
+        constexpr auto begin_adaptor() const noexcept
+            -> CPP_ret(adaptor<true>)(
+                requires(const_iterable()))
+        {
+            return adaptor<true>{this};
+        }
+
+        constexpr meta::if_c<can_bound<false>(), adaptor<false>, adaptor_base> //
+        end_adaptor() noexcept
+        {
+            return {this};
+        }
+        CPP_member
+        constexpr auto end_adaptor() const noexcept //
+            -> CPP_ret(meta::if_c<can_bound<true>(), adaptor<true>, adaptor_base>)(
+                requires (const_iterable()))
+        {
+            return {this};
+        }
+
+    public:
+        stride_view() = default;
+        constexpr stride_view(Rng rng, range_difference_t<Rng> const stride)
+          : detail::stride_view_base<Rng>{std::move(rng), stride}
+        {}
+        CPP_auto_member
+        constexpr auto CPP_fun(size)()(
+            requires sized_range<Rng>)
+        {
+            using size_type = range_size_t<Rng>;
+            auto const n = ranges::size(this->base());
+            return (n + static_cast<size_type>(this->stride_) - 1) /
+                   static_cast<size_type>(this->stride_);
+        }
+        CPP_auto_member
+        constexpr auto CPP_fun(size)()(const //
+            requires sized_range<Rng const>)
+        {
+            using size_type = range_size_t<Rng const>;
+            auto const n = ranges::size(this->base());
+            return (n + static_cast<size_type>(this->stride_) - 1) /
+                   static_cast<size_type>(this->stride_);
+        }
+    };
+
+#if RANGES_CXX_DEDUCTION_GUIDES >= RANGES_CXX_DEDUCTION_GUIDES_17
+    template<typename Rng>
+    stride_view(Rng &&, range_difference_t<Rng>)
+        -> stride_view<views::all_t<Rng>>;
+#endif
+
+    namespace views
+    {
+        struct stride_base_fn
+        {
+            template(typename Rng)(
+                requires viewable_range<Rng> AND input_range<Rng>)
+            constexpr stride_view<all_t<Rng>> //
+            operator()(Rng && rng, range_difference_t<Rng> step) const
+            {
+                return stride_view<all_t<Rng>>{all(static_cast<Rng &&>(rng)), step};
+            }
+        };
+
+        struct stride_fn : stride_base_fn
+        {
+            using stride_base_fn::operator();
+
+            template(typename Difference)(
+                requires detail::integer_like_<Difference>)
+            constexpr auto operator()(Difference step) const
+            {
+                return make_view_closure(bind_back(stride_base_fn{}, step));
+            }
+        };
+
+        /// \relates stride_fn
+        /// \ingroup group-views
+        RANGES_INLINE_VARIABLE(stride_fn, stride)
+    } // namespace views
+    /// @}
+} // namespace ranges
+
+#include <range/v3/detail/epilogue.hpp>
+#include <range/v3/detail/satisfy_boost_range.hpp>
+RANGES_SATISFY_BOOST_RANGE(::ranges::stride_view)
+
+#endif