🛠️🐜 Antkeeper superbuild with dependencies included
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307 lines
12 KiB
307 lines
12 KiB
#ifndef AL_SPAN_H
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#define AL_SPAN_H
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#include <array>
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#include <cstddef>
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#include <initializer_list>
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#include <iterator>
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#include <type_traits>
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namespace al {
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template<typename T>
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constexpr auto size(const T &cont) noexcept(noexcept(cont.size())) -> decltype(cont.size())
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{ return cont.size(); }
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template<typename T, size_t N>
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constexpr size_t size(const T (&)[N]) noexcept
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{ return N; }
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template<typename T>
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constexpr auto data(T &cont) noexcept(noexcept(cont.data())) -> decltype(cont.data())
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{ return cont.data(); }
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template<typename T>
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constexpr auto data(const T &cont) noexcept(noexcept(cont.data())) -> decltype(cont.data())
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{ return cont.data(); }
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template<typename T, size_t N>
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constexpr T* data(T (&arr)[N]) noexcept
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{ return arr; }
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template<typename T>
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constexpr const T* data(std::initializer_list<T> list) noexcept
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{ return list.begin(); }
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constexpr size_t dynamic_extent{static_cast<size_t>(-1)};
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template<typename T, size_t E=dynamic_extent>
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class span;
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namespace detail_ {
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template<typename... Ts>
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struct make_void { using type = void; };
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template<typename... Ts>
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using void_t = typename make_void<Ts...>::type;
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template<typename T>
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struct is_span_ : std::false_type { };
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template<typename T, size_t E>
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struct is_span_<span<T,E>> : std::true_type { };
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template<typename T>
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using is_span = is_span_<std::remove_cv_t<T>>;
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template<typename T>
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struct is_std_array_ : std::false_type { };
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template<typename T, size_t N>
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struct is_std_array_<std::array<T,N>> : std::true_type { };
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template<typename T>
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using is_std_array = is_std_array_<std::remove_cv_t<T>>;
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template<typename T, typename = void>
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struct has_size_and_data : std::false_type { };
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template<typename T>
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struct has_size_and_data<T,
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void_t<decltype(al::size(std::declval<T>())), decltype(al::data(std::declval<T>()))>>
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: std::true_type { };
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} // namespace detail_
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#define REQUIRES(...) bool rt_=true, std::enable_if_t<rt_ && (__VA_ARGS__),bool> = true
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#define IS_VALID_CONTAINER(C) \
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!detail_::is_span<C>::value && !detail_::is_std_array<C>::value && \
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!std::is_array<C>::value && detail_::has_size_and_data<C>::value && \
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std::is_convertible<std::remove_pointer_t<decltype(al::data(std::declval<C&>()))>(*)[],element_type(*)[]>::value
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template<typename T, size_t E>
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class span {
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public:
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using element_type = T;
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using value_type = std::remove_cv_t<T>;
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using index_type = size_t;
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using difference_type = ptrdiff_t;
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using pointer = T*;
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using const_pointer = const T*;
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using reference = T&;
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using const_reference = const T&;
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using iterator = pointer;
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using const_iterator = const_pointer;
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using reverse_iterator = std::reverse_iterator<iterator>;
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using const_reverse_iterator = std::reverse_iterator<const_iterator>;
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static constexpr size_t extent{E};
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template<REQUIRES(extent==0)>
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constexpr span() noexcept { }
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constexpr span(pointer ptr, index_type /*count*/) : mData{ptr} { }
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constexpr span(pointer first, pointer /*last*/) : mData{first} { }
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constexpr span(element_type (&arr)[E]) noexcept : span{al::data(arr), al::size(arr)} { }
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constexpr span(std::array<value_type,E> &arr) noexcept : span{al::data(arr), al::size(arr)} { }
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template<REQUIRES(std::is_const<element_type>::value)>
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constexpr span(const std::array<value_type,E> &arr) noexcept
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: span{al::data(arr), al::size(arr)}
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{ }
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template<typename U, REQUIRES(IS_VALID_CONTAINER(U))>
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constexpr span(U &cont) : span{al::data(cont), al::size(cont)} { }
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template<typename U, REQUIRES(IS_VALID_CONTAINER(const U))>
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constexpr span(const U &cont) : span{al::data(cont), al::size(cont)} { }
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template<typename U, REQUIRES(!std::is_same<element_type,U>::value
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&& std::is_convertible<U(*)[],element_type(*)[]>::value)>
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constexpr span(const span<U,E> &span_) noexcept : span{al::data(span_), al::size(span_)} { }
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constexpr span(const span&) noexcept = default;
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constexpr span& operator=(const span &rhs) noexcept = default;
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constexpr reference front() const { return *mData; }
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constexpr reference back() const { return *(mData+E-1); }
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constexpr reference operator[](index_type idx) const { return mData[idx]; }
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constexpr pointer data() const noexcept { return mData; }
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constexpr index_type size() const noexcept { return E; }
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constexpr index_type size_bytes() const noexcept { return E * sizeof(value_type); }
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constexpr bool empty() const noexcept { return E == 0; }
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constexpr iterator begin() const noexcept { return mData; }
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constexpr iterator end() const noexcept { return mData+E; }
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constexpr const_iterator cbegin() const noexcept { return mData; }
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constexpr const_iterator cend() const noexcept { return mData+E; }
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constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator{end()}; }
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constexpr reverse_iterator rend() const noexcept { return reverse_iterator{begin()}; }
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constexpr const_reverse_iterator crbegin() const noexcept
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{ return const_reverse_iterator{cend()}; }
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constexpr const_reverse_iterator crend() const noexcept
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{ return const_reverse_iterator{cbegin()}; }
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template<size_t C>
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constexpr span<element_type,C> first() const
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{
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static_assert(E >= C, "New size exceeds original capacity");
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return span<element_type,C>{mData, C};
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}
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template<size_t C>
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constexpr span<element_type,C> last() const
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{
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static_assert(E >= C, "New size exceeds original capacity");
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return span<element_type,C>{mData+(E-C), C};
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}
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template<size_t O, size_t C>
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constexpr auto subspan() const -> std::enable_if_t<C!=dynamic_extent,span<element_type,C>>
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{
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static_assert(E >= O, "Offset exceeds extent");
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static_assert(E-O >= C, "New size exceeds original capacity");
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return span<element_type,C>{mData+O, C};
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}
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template<size_t O, size_t C=dynamic_extent>
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constexpr auto subspan() const -> std::enable_if_t<C==dynamic_extent,span<element_type,E-O>>
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{
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static_assert(E >= O, "Offset exceeds extent");
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return span<element_type,E-O>{mData+O, E-O};
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}
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/* NOTE: Can't declare objects of a specialized template class prior to
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* defining the specialization. As a result, these methods need to be
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* defined later.
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*/
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constexpr span<element_type,dynamic_extent> first(size_t count) const;
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constexpr span<element_type,dynamic_extent> last(size_t count) const;
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constexpr span<element_type,dynamic_extent> subspan(size_t offset,
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size_t count=dynamic_extent) const;
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private:
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pointer mData{nullptr};
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};
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template<typename T>
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class span<T,dynamic_extent> {
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public:
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using element_type = T;
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using value_type = std::remove_cv_t<T>;
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using index_type = size_t;
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using difference_type = ptrdiff_t;
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using pointer = T*;
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using const_pointer = const T*;
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using reference = T&;
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using const_reference = const T&;
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using iterator = pointer;
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using const_iterator = const_pointer;
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using reverse_iterator = std::reverse_iterator<iterator>;
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using const_reverse_iterator = std::reverse_iterator<const_iterator>;
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static constexpr size_t extent{dynamic_extent};
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constexpr span() noexcept = default;
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constexpr span(pointer ptr, index_type count) : mData{ptr}, mDataEnd{ptr+count} { }
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constexpr span(pointer first, pointer last) : mData{first}, mDataEnd{last} { }
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template<size_t N>
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constexpr span(element_type (&arr)[N]) noexcept : span{al::data(arr), al::size(arr)} { }
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template<size_t N>
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constexpr span(std::array<value_type,N> &arr) noexcept : span{al::data(arr), al::size(arr)} { }
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template<size_t N, REQUIRES(std::is_const<element_type>::value)>
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constexpr span(const std::array<value_type,N> &arr) noexcept
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: span{al::data(arr), al::size(arr)}
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{ }
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template<typename U, REQUIRES(IS_VALID_CONTAINER(U))>
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constexpr span(U &cont) : span{al::data(cont), al::size(cont)} { }
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template<typename U, REQUIRES(IS_VALID_CONTAINER(const U))>
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constexpr span(const U &cont) : span{al::data(cont), al::size(cont)} { }
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template<typename U, size_t N, REQUIRES((!std::is_same<element_type,U>::value || extent != N)
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&& std::is_convertible<U(*)[],element_type(*)[]>::value)>
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constexpr span(const span<U,N> &span_) noexcept : span{al::data(span_), al::size(span_)} { }
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constexpr span(const span&) noexcept = default;
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constexpr span& operator=(const span &rhs) noexcept = default;
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constexpr reference front() const { return *mData; }
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constexpr reference back() const { return *(mDataEnd-1); }
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constexpr reference operator[](index_type idx) const { return mData[idx]; }
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constexpr pointer data() const noexcept { return mData; }
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constexpr index_type size() const noexcept { return static_cast<index_type>(mDataEnd-mData); }
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constexpr index_type size_bytes() const noexcept
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{ return static_cast<index_type>(mDataEnd-mData) * sizeof(value_type); }
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constexpr bool empty() const noexcept { return mData == mDataEnd; }
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constexpr iterator begin() const noexcept { return mData; }
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constexpr iterator end() const noexcept { return mDataEnd; }
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constexpr const_iterator cbegin() const noexcept { return mData; }
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constexpr const_iterator cend() const noexcept { return mDataEnd; }
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constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator{end()}; }
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constexpr reverse_iterator rend() const noexcept { return reverse_iterator{begin()}; }
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constexpr const_reverse_iterator crbegin() const noexcept
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{ return const_reverse_iterator{cend()}; }
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constexpr const_reverse_iterator crend() const noexcept
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{ return const_reverse_iterator{cbegin()}; }
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template<size_t C>
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constexpr span<element_type,C> first() const
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{ return span<element_type,C>{mData, C}; }
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constexpr span first(size_t count) const
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{ return (count >= size()) ? *this : span{mData, mData+count}; }
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template<size_t C>
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constexpr span<element_type,C> last() const
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{ return span<element_type,C>{mDataEnd-C, C}; }
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constexpr span last(size_t count) const
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{ return (count >= size()) ? *this : span{mDataEnd-count, mDataEnd}; }
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template<size_t O, size_t C>
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constexpr auto subspan() const -> std::enable_if_t<C!=dynamic_extent,span<element_type,C>>
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{ return span<element_type,C>{mData+O, C}; }
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template<size_t O, size_t C=dynamic_extent>
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constexpr auto subspan() const -> std::enable_if_t<C==dynamic_extent,span<element_type,C>>
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{ return span<element_type,C>{mData+O, mDataEnd}; }
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constexpr span subspan(size_t offset, size_t count=dynamic_extent) const
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{
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return (offset > size()) ? span{} :
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(count >= size()-offset) ? span{mData+offset, mDataEnd} :
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span{mData+offset, mData+offset+count};
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}
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private:
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pointer mData{nullptr};
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pointer mDataEnd{nullptr};
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};
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template<typename T, size_t E>
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constexpr inline auto span<T,E>::first(size_t count) const -> span<element_type,dynamic_extent>
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{
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return (count >= size()) ? span<element_type>{mData, extent} :
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span<element_type>{mData, count};
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}
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template<typename T, size_t E>
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constexpr inline auto span<T,E>::last(size_t count) const -> span<element_type,dynamic_extent>
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{
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return (count >= size()) ? span<element_type>{mData, extent} :
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span<element_type>{mData+extent-count, count};
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}
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template<typename T, size_t E>
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constexpr inline auto span<T,E>::subspan(size_t offset, size_t count) const
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-> span<element_type,dynamic_extent>
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{
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return (offset > size()) ? span<element_type>{} :
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(count >= size()-offset) ? span<element_type>{mData+offset, mData+extent} :
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span<element_type>{mData+offset, mData+offset+count};
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}
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#undef IS_VALID_CONTAINER
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#undef REQUIRES
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} // namespace al
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#endif /* AL_SPAN_H */
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