// Copyright (C) 2019 T. Zachary Laine
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_STL_INTERFACES_VIEW_INTERFACE_HPP
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#define BOOST_STL_INTERFACES_VIEW_INTERFACE_HPP
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#include <boost/stl_interfaces/fwd.hpp>
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namespace boost { namespace stl_interfaces { inline namespace v1 {
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/** A CRTP template that one may derive from to make it easier to define
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`std::ranges::view`-like types with a container-like interface. This
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is a pre-C++20 version of C++20's `view_interface` (see
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[view.interface] in the C++ standard).
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The template parameter `D` for `view_interface` may be an incomplete
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type. Before any member of the resulting specialization of
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`view_interface` other than special member functions is referenced,
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`D` shall be complete, and model both
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`std::derived_from<view_interface<D>>` and `std::view`. */
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template<
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typename Derived,
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element_layout Contiguity = element_layout::discontiguous
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#ifndef BOOST_STL_INTERFACES_DOXYGEN
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,
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typename E = std::enable_if_t<
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std::is_class<Derived>::value &&
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std::is_same<Derived, std::remove_cv_t<Derived>>::value>
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#endif
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>
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struct view_interface;
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namespace v1_dtl {
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template<typename D, element_layout Contiguity>
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void derived_view(view_interface<D, Contiguity> const &);
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}
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template<
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typename Derived,
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element_layout Contiguity
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#ifndef BOOST_STL_INTERFACES_DOXYGEN
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,
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typename E
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#endif
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>
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struct view_interface
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{
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#ifndef BOOST_STL_INTERFACES_DOXYGEN
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private:
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constexpr Derived & derived() noexcept
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{
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return static_cast<Derived &>(*this);
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}
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constexpr const Derived & derived() const noexcept
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{
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return static_cast<Derived const &>(*this);
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}
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#endif
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public:
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template<typename D = Derived>
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constexpr auto empty() noexcept(
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noexcept(std::declval<D &>().begin() == std::declval<D &>().end()))
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-> decltype(
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std::declval<D &>().begin() == std::declval<D &>().end())
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{
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return derived().begin() == derived().end();
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}
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template<typename D = Derived>
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constexpr auto empty() const noexcept(noexcept(
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std::declval<D const &>().begin() ==
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std::declval<D const &>().end()))
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-> decltype(
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std::declval<D const &>().begin() ==
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std::declval<D const &>().end())
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{
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return derived().begin() == derived().end();
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}
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template<
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typename D = Derived,
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typename R = decltype(std::declval<D &>().empty())>
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constexpr explicit
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operator bool() noexcept(noexcept(std::declval<D &>().empty()))
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{
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return !derived().empty();
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}
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template<
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typename D = Derived,
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typename R = decltype(std::declval<D const &>().empty())>
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constexpr explicit operator bool() const
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noexcept(noexcept(std::declval<D const &>().empty()))
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{
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return !derived().empty();
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}
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template<
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typename D = Derived,
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element_layout C = Contiguity,
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typename Enable = std::enable_if_t<C == element_layout::contiguous>>
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constexpr auto data() noexcept(noexcept(std::declval<D &>().begin()))
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-> decltype(std::addressof(*std::declval<D &>().begin()))
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{
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return std::addressof(*derived().begin());
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}
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template<
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typename D = Derived,
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element_layout C = Contiguity,
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typename Enable = std::enable_if_t<C == element_layout::contiguous>>
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constexpr auto data() const
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noexcept(noexcept(std::declval<D const &>().begin()))
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-> decltype(std::addressof(*std::declval<D const &>().begin()))
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{
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return std::addressof(*derived().begin());
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}
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template<typename D = Derived>
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constexpr auto size() noexcept(
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noexcept(std::declval<D &>().end() - std::declval<D &>().begin()))
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-> decltype(std::declval<D &>().end() - std::declval<D &>().begin())
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{
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return derived().end() - derived().begin();
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}
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template<typename D = Derived>
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constexpr auto size() const noexcept(noexcept(
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std::declval<D const &>().end() -
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std::declval<D const &>().begin()))
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-> decltype(
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std::declval<D const &>().end() -
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std::declval<D const &>().begin())
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{
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return derived().end() - derived().begin();
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}
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template<typename D = Derived>
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constexpr auto front() noexcept(noexcept(*std::declval<D &>().begin()))
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-> decltype(*std::declval<D &>().begin())
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{
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return *derived().begin();
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}
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template<typename D = Derived>
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constexpr auto front() const
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noexcept(noexcept(*std::declval<D const &>().begin()))
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-> decltype(*std::declval<D const &>().begin())
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{
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return *derived().begin();
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}
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template<
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typename D = Derived,
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typename Enable = std::enable_if_t<
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v1_dtl::decrementable_sentinel<D>::value &&
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v1_dtl::common_range<D>::value>>
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constexpr auto
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back() noexcept(noexcept(*std::prev(std::declval<D &>().end())))
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-> decltype(*std::prev(std::declval<D &>().end()))
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{
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return *std::prev(derived().end());
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}
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template<
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typename D = Derived,
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typename Enable = std::enable_if_t<
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v1_dtl::decrementable_sentinel<D>::value &&
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v1_dtl::common_range<D>::value>>
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constexpr auto back() const
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noexcept(noexcept(*std::prev(std::declval<D const &>().end())))
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-> decltype(*std::prev(std::declval<D const &>().end()))
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{
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return *std::prev(derived().end());
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}
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template<typename D = Derived>
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constexpr auto operator[](v1_dtl::range_difference_t<D> n) noexcept(
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noexcept(std::declval<D &>().begin()[n]))
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-> decltype(std::declval<D &>().begin()[n])
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{
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return derived().begin()[n];
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}
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template<typename D = Derived>
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constexpr auto operator[](v1_dtl::range_difference_t<D> n) const
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noexcept(noexcept(std::declval<D const &>().begin()[n]))
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-> decltype(std::declval<D const &>().begin()[n])
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{
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return derived().begin()[n];
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}
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};
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/** Implementation of `operator!=()` for all views derived from
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`view_interface`. */
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template<typename ViewInterface>
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constexpr auto operator!=(ViewInterface lhs, ViewInterface rhs) noexcept(
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noexcept(lhs == rhs))
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-> decltype(v1_dtl::derived_view(lhs), !(lhs == rhs))
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{
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return !(lhs == rhs);
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}
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}}}
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#if 201703L < __cplusplus && defined(__cpp_lib_concepts) || \
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defined(BOOST_STL_INTERFACES_DOXYGEN)
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#include <ranges>
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namespace boost { namespace stl_interfaces { namespace v2 {
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/** A template alias for `std::view_interface`. This only exists to make
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migration from Boost.STLInterfaces to C++20 easier; switch to the one
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in `std` as soon as you can. */
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template<typename D, bool = false>
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using view_interface = std::ranges::view_interface<D>;
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}}}
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#endif
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#endif
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