experimental/view/shared.hpp

0001 /// \file
0002 // Range v3 library
0003 //
0004 //  Copyright Filip Matzner 2017
0005 //
0006 //  Use, modification and distribution is subject to the
0007 //  Boost Software License, Version 1.0. (See accompanying
0008 //  file LICENSE_1_0.txt or copy at
0009 //  http://www.boost.org/LICENSE_1_0.txt)
0010 //
0011 // Project home: https://github.com/ericniebler/range-v3
0012 //
0013 #ifndef RANGES_V3_EXPERIMENTAL_VIEW_SHARED_HPP
0014 #define RANGES_V3_EXPERIMENTAL_VIEW_SHARED_HPP
0015
0016 #include <memory>
0017 #include <type_traits>
0018
0019 #include <meta/meta.hpp>
0020
0021 #include <range/v3/functional/compose.hpp>
0022 #include <range/v3/range/access.hpp>
0023 #include <range/v3/range/concepts.hpp>
0024 #include <range/v3/range/primitives.hpp>
0025 #include <range/v3/view/all.hpp>
0026
0027 #include <range/v3/detail/prologue.hpp>
0028
0029 namespace ranges
0030 {
0031     /// \addtogroup group-views
0032     /// @{
0033     namespace experimental
0034     {
0035         template<typename Rng>
0036         struct shared_view
0037           : view_interface<shared_view<Rng>, range_cardinality<Rng>::value>
0038         {
0039         private:
0040             // shared storage
0041             std::shared_ptr<Rng> rng_ptr_;
0042
0043         public:
0044             shared_view() = default;
0045
0046             // construct from a range rvalue
0047             explicit shared_view(Rng rng)
0048               : rng_ptr_{std::make_shared<Rng>(std::move(rng))}
0049             {}
0050
0051             // use the stored range's begin and end
0052             iterator_t<Rng> begin() const
0053             {
0054                 return ranges::begin(*rng_ptr_);
0055             }
0056             sentinel_t<Rng> end() const
0057             {
0058                 return ranges::end(*rng_ptr_);
0059             }
0060
0061             CPP_auto_member
0062             auto CPP_fun(size)()(const
0063                 requires sized_range<Rng>)
0064             {
0065                 return ranges::size(*rng_ptr_);
0066             }
0067         };
0068
0069         template<typename SharedFn>
0070         struct shared_closure;
0071
0072         struct RANGES_STRUCT_WITH_ADL_BARRIER(shared_closure_base)
0073         {
0074             // Piping requires viewable_ranges.
0075             template(typename Rng, typename SharedFn)(
0076                 requires range<Rng> AND (!viewable_range<Rng>) AND
0077                     constructible_from<detail::decay_t<Rng>, Rng>)
0078             friend constexpr auto operator|(Rng && rng, shared_closure<SharedFn> vw)
0079             {
0080                 return static_cast<SharedFn &&>(vw)(static_cast<Rng &&>(rng));
0081             }
0082
0083             template<typename SharedFn, typename Pipeable>
0084             friend constexpr auto operator|(shared_closure<SharedFn> sh, Pipeable pipe)
0085                 -> CPP_broken_friend_ret(shared_closure<composed<Pipeable, SharedFn>>)(
0086                     requires (is_pipeable_v<Pipeable>))
0087             {
0088                 return shared_closure<composed<Pipeable, SharedFn>>{compose(
0089                     static_cast<Pipeable &&>(pipe), static_cast<SharedFn &&>(sh))};
0090             }
0091         };
0092
0093         template<typename SharedFn>
0094         struct shared_closure
0095           : shared_closure_base
0096           , SharedFn
0097         {
0098             shared_closure() = default;
0099             constexpr explicit shared_closure(SharedFn fn)
0100               : SharedFn(static_cast<SharedFn &&>(fn))
0101             {}
0102         };
0103
0104         namespace views
0105         {
0106             struct shared_fn
0107             {
0108                 template(typename Rng)(
0109                     requires range<Rng> AND (!viewable_range<Rng>)AND
0110                         constructible_from<detail::decay_t<Rng>, Rng>)
0111                 shared_view<detail::decay_t<Rng>> operator()(Rng && rng) const
0112                 {
0113                     return shared_view<detail::decay_t<Rng>>{static_cast<Rng &&>(rng)};
0114                 }
0115             };
0116
0117             /// \relates shared_fn
0118             /// \ingroup group-views
0119             RANGES_INLINE_VARIABLE(shared_closure<shared_fn>, shared)
0120         } // namespace views
0121     }     // namespace experimental
0122
0123     template<typename SharedFn>
0124     RANGES_INLINE_VAR constexpr bool
0125         is_pipeable_v<experimental::shared_closure<SharedFn>> = true;
0126     /// @}
0127 } // namespace ranges
0128
0129 #include <range/v3/detail/epilogue.hpp>
0130
0131 #endif