6 #include <initializer_list>
16 constexpr auto size(const T &cont) noexcept(noexcept(cont.size())) -> decltype(cont.size())
17 { return cont.size(); }
19 template<typename T, size_t N>
20 constexpr size_t size(const T (&)[N]) noexcept
25 constexpr auto data(T &cont) noexcept(noexcept(cont.data())) -> decltype(cont.data())
26 { return cont.data(); }
29 constexpr auto data(const T &cont) noexcept(noexcept(cont.data())) -> decltype(cont.data())
30 { return cont.data(); }
32 template<typename T, size_t N>
33 constexpr T* data(T (&arr)[N]) noexcept
37 constexpr const T* data(std::initializer_list<T> list) noexcept
38 { return list.begin(); }
41 constexpr size_t dynamic_extent{static_cast<size_t>(-1)};
43 template<typename T, size_t E=dynamic_extent>
47 template<typename... Ts>
51 struct is_span_ : std::false_type { };
52 template<typename T, size_t E>
53 struct is_span_<span<T,E>> : std::true_type { };
55 constexpr bool is_span_v = is_span_<std::remove_cv_t<T>>::value;
58 struct is_std_array_ : std::false_type { };
59 template<typename T, size_t N>
60 struct is_std_array_<std::array<T,N>> : std::true_type { };
62 constexpr bool is_std_array_v = is_std_array_<std::remove_cv_t<T>>::value;
64 template<typename T, typename = void>
65 constexpr bool has_size_and_data = false;
67 constexpr bool has_size_and_data<T,
68 void_t<decltype(al::size(std::declval<T>())), decltype(al::data(std::declval<T>()))>>
71 template<typename T, typename U>
72 constexpr bool is_array_compatible = std::is_convertible<T(*)[],U(*)[]>::value;
74 template<typename C, typename T>
75 constexpr bool is_valid_container = !is_span_v<C> && !is_std_array_v<C>
76 && !std::is_array<C>::value && has_size_and_data<C>
77 && is_array_compatible<std::remove_pointer_t<decltype(al::data(std::declval<C&>()))>,T>;
78 } // namespace detail_
80 #define REQUIRES(...) std::enable_if_t<(__VA_ARGS__),bool> = true
82 template<typename T, size_t E>
85 using element_type = T;
86 using value_type = std::remove_cv_t<T>;
87 using index_type = size_t;
88 using difference_type = ptrdiff_t;
91 using const_pointer = const T*;
93 using const_reference = const T&;
95 using iterator = pointer;
96 using const_iterator = const_pointer;
97 using reverse_iterator = std::reverse_iterator<iterator>;
98 using const_reverse_iterator = std::reverse_iterator<const_iterator>;
100 static constexpr size_t extent{E};
102 template<bool is0=(extent == 0), REQUIRES(is0)>
103 constexpr span() noexcept { }
105 constexpr explicit span(U iter, index_type) : mData{to_address(iter)} { }
106 template<typename U, typename V, REQUIRES(!std::is_convertible<V,size_t>::value)>
107 constexpr explicit span(U first, V) : mData{to_address(first)} { }
109 constexpr span(type_identity_t<element_type> (&arr)[E]) noexcept
110 : span{al::data(arr), al::size(arr)}
112 constexpr span(std::array<value_type,E> &arr) noexcept : span{al::data(arr), al::size(arr)} { }
113 template<typename U=T, REQUIRES(std::is_const<U>::value)>
114 constexpr span(const std::array<value_type,E> &arr) noexcept
115 : span{al::data(arr), al::size(arr)}
118 template<typename U, REQUIRES(detail_::is_valid_container<U, element_type>)>
119 constexpr explicit span(U&& cont) : span{al::data(cont), al::size(cont)} { }
121 template<typename U, index_type N, REQUIRES(!std::is_same<element_type,U>::value
122 && detail_::is_array_compatible<U,element_type> && N == dynamic_extent)>
123 constexpr explicit span(const span<U,N> &span_) noexcept
124 : span{al::data(span_), al::size(span_)}
126 template<typename U, index_type N, REQUIRES(!std::is_same<element_type,U>::value
127 && detail_::is_array_compatible<U,element_type> && N == extent)>
128 constexpr span(const span<U,N> &span_) noexcept : span{al::data(span_), al::size(span_)} { }
129 constexpr span(const span&) noexcept = default;
131 constexpr span& operator=(const span &rhs) noexcept = default;
133 constexpr reference front() const { return *mData; }
134 constexpr reference back() const { return *(mData+E-1); }
135 constexpr reference operator[](index_type idx) const { return mData[idx]; }
136 constexpr pointer data() const noexcept { return mData; }
138 constexpr index_type size() const noexcept { return E; }
139 constexpr index_type size_bytes() const noexcept { return E * sizeof(value_type); }
140 constexpr bool empty() const noexcept { return E == 0; }
142 constexpr iterator begin() const noexcept { return mData; }
143 constexpr iterator end() const noexcept { return mData+E; }
144 constexpr const_iterator cbegin() const noexcept { return mData; }
145 constexpr const_iterator cend() const noexcept { return mData+E; }
147 constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator{end()}; }
148 constexpr reverse_iterator rend() const noexcept { return reverse_iterator{begin()}; }
149 constexpr const_reverse_iterator crbegin() const noexcept
150 { return const_reverse_iterator{cend()}; }
151 constexpr const_reverse_iterator crend() const noexcept
152 { return const_reverse_iterator{cbegin()}; }
155 constexpr span<element_type,C> first() const
157 static_assert(E >= C, "New size exceeds original capacity");
158 return span<element_type,C>{mData, C};
162 constexpr span<element_type,C> last() const
164 static_assert(E >= C, "New size exceeds original capacity");
165 return span<element_type,C>{mData+(E-C), C};
168 template<size_t O, size_t C>
169 constexpr auto subspan() const -> std::enable_if_t<C!=dynamic_extent,span<element_type,C>>
171 static_assert(E >= O, "Offset exceeds extent");
172 static_assert(E-O >= C, "New size exceeds original capacity");
173 return span<element_type,C>{mData+O, C};
176 template<size_t O, size_t C=dynamic_extent>
177 constexpr auto subspan() const -> std::enable_if_t<C==dynamic_extent,span<element_type,E-O>>
179 static_assert(E >= O, "Offset exceeds extent");
180 return span<element_type,E-O>{mData+O, E-O};
183 /* NOTE: Can't declare objects of a specialized template class prior to
184 * defining the specialization. As a result, these methods need to be
187 constexpr span<element_type,dynamic_extent> first(size_t count) const;
188 constexpr span<element_type,dynamic_extent> last(size_t count) const;
189 constexpr span<element_type,dynamic_extent> subspan(size_t offset,
190 size_t count=dynamic_extent) const;
193 pointer mData{nullptr};
197 class span<T,dynamic_extent> {
199 using element_type = T;
200 using value_type = std::remove_cv_t<T>;
201 using index_type = size_t;
202 using difference_type = ptrdiff_t;
205 using const_pointer = const T*;
206 using reference = T&;
207 using const_reference = const T&;
209 using iterator = pointer;
210 using const_iterator = const_pointer;
211 using reverse_iterator = std::reverse_iterator<iterator>;
212 using const_reverse_iterator = std::reverse_iterator<const_iterator>;
214 static constexpr size_t extent{dynamic_extent};
216 constexpr span() noexcept = default;
218 constexpr span(U iter, index_type count)
219 : mData{to_address(iter)}, mDataEnd{to_address(iter)+count}
221 template<typename U, typename V, REQUIRES(!std::is_convertible<V,size_t>::value)>
222 constexpr span(U first, V last) : span{to_address(first), static_cast<size_t>(last-first)}
226 constexpr span(type_identity_t<element_type> (&arr)[N]) noexcept
227 : span{al::data(arr), al::size(arr)}
230 constexpr span(std::array<value_type,N> &arr) noexcept : span{al::data(arr), al::size(arr)} { }
231 template<size_t N, typename U=T, REQUIRES(std::is_const<U>::value)>
232 constexpr span(const std::array<value_type,N> &arr) noexcept
233 : span{al::data(arr), al::size(arr)}
236 template<typename U, REQUIRES(detail_::is_valid_container<U, element_type>)>
237 constexpr span(U&& cont) : span{al::data(cont), al::size(cont)} { }
239 template<typename U, size_t N, REQUIRES((!std::is_same<element_type,U>::value || extent != N)
240 && detail_::is_array_compatible<U,element_type>)>
241 constexpr span(const span<U,N> &span_) noexcept : span{al::data(span_), al::size(span_)} { }
242 constexpr span(const span&) noexcept = default;
244 constexpr span& operator=(const span &rhs) noexcept = default;
246 constexpr reference front() const { return *mData; }
247 constexpr reference back() const { return *(mDataEnd-1); }
248 constexpr reference operator[](index_type idx) const { return mData[idx]; }
249 constexpr pointer data() const noexcept { return mData; }
251 constexpr index_type size() const noexcept { return static_cast<index_type>(mDataEnd-mData); }
252 constexpr index_type size_bytes() const noexcept
253 { return static_cast<index_type>(mDataEnd-mData) * sizeof(value_type); }
254 constexpr bool empty() const noexcept { return mData == mDataEnd; }
256 constexpr iterator begin() const noexcept { return mData; }
257 constexpr iterator end() const noexcept { return mDataEnd; }
258 constexpr const_iterator cbegin() const noexcept { return mData; }
259 constexpr const_iterator cend() const noexcept { return mDataEnd; }
261 constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator{end()}; }
262 constexpr reverse_iterator rend() const noexcept { return reverse_iterator{begin()}; }
263 constexpr const_reverse_iterator crbegin() const noexcept
264 { return const_reverse_iterator{cend()}; }
265 constexpr const_reverse_iterator crend() const noexcept
266 { return const_reverse_iterator{cbegin()}; }
269 constexpr span<element_type,C> first() const
270 { return span<element_type,C>{mData, C}; }
272 constexpr span first(size_t count) const
273 { return (count >= size()) ? *this : span{mData, mData+count}; }
276 constexpr span<element_type,C> last() const
277 { return span<element_type,C>{mDataEnd-C, C}; }
279 constexpr span last(size_t count) const
280 { return (count >= size()) ? *this : span{mDataEnd-count, mDataEnd}; }
282 template<size_t O, size_t C>
283 constexpr auto subspan() const -> std::enable_if_t<C!=dynamic_extent,span<element_type,C>>
284 { return span<element_type,C>{mData+O, C}; }
286 template<size_t O, size_t C=dynamic_extent>
287 constexpr auto subspan() const -> std::enable_if_t<C==dynamic_extent,span<element_type,C>>
288 { return span<element_type,C>{mData+O, mDataEnd}; }
290 constexpr span subspan(size_t offset, size_t count=dynamic_extent) const
292 return (offset > size()) ? span{} :
293 (count >= size()-offset) ? span{mData+offset, mDataEnd} :
294 span{mData+offset, mData+offset+count};
298 pointer mData{nullptr};
299 pointer mDataEnd{nullptr};
302 template<typename T, size_t E>
303 constexpr inline auto span<T,E>::first(size_t count) const -> span<element_type,dynamic_extent>
305 return (count >= size()) ? span<element_type>{mData, extent} :
306 span<element_type>{mData, count};
309 template<typename T, size_t E>
310 constexpr inline auto span<T,E>::last(size_t count) const -> span<element_type,dynamic_extent>
312 return (count >= size()) ? span<element_type>{mData, extent} :
313 span<element_type>{mData+extent-count, count};
316 template<typename T, size_t E>
317 constexpr inline auto span<T,E>::subspan(size_t offset, size_t count) const
318 -> span<element_type,dynamic_extent>
320 return (offset > size()) ? span<element_type>{} :
321 (count >= size()-offset) ? span<element_type>{mData+offset, mData+extent} :
322 span<element_type>{mData+offset, mData+offset+count};
325 /* Helpers to deal with the lack of user-defined deduction guides (C++17). */
326 template<typename T, typename U>
327 constexpr auto as_span(T ptr, U count_or_end)
329 using value_type = typename std::pointer_traits<T>::element_type;
330 return span<value_type>{ptr, count_or_end};
332 template<typename T, size_t N>
333 constexpr auto as_span(T (&arr)[N]) noexcept { return span<T,N>{al::data(arr), al::size(arr)}; }
334 template<typename T, size_t N>
335 constexpr auto as_span(std::array<T,N> &arr) noexcept
336 { return span<T,N>{al::data(arr), al::size(arr)}; }
337 template<typename T, size_t N>
338 constexpr auto as_span(const std::array<T,N> &arr) noexcept
339 { return span<std::add_const_t<T>,N>{al::data(arr), al::size(arr)}; }
340 template<typename U, REQUIRES(!detail_::is_span_v<U> && !detail_::is_std_array_v<U>
341 && !std::is_array<U>::value && detail_::has_size_and_data<U>)>
342 constexpr auto as_span(U&& cont)
344 using value_type = std::remove_pointer_t<decltype(al::data(std::declval<U&>()))>;
345 return span<value_type>{al::data(cont), al::size(cont)};
347 template<typename T, size_t N>
348 constexpr auto as_span(span<T,N> span_) noexcept { return span_; }
354 #endif /* AL_SPAN_H */