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18441///////////////////////////////////////////////////////////////////////////////
2//
3// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
4//
5// This code is licensed under the MIT License (MIT).
6//
7// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
8// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
9// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
10// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
11// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
12// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
13// THE SOFTWARE.
14//
15///////////////////////////////////////////////////////////////////////////////
16
17
18
19
20// for Expects
21// for byte
22// for span specialization of gsl::at and other span-related extensions
23// for narrow_cast
24
25// for array
26// for ptrdiff_t, size_t, nullptr_t
27// for reverse_iterator, distance, random_access_...
28// for pointer_traits
29// for enable_if_t, declval, is_convertible, inte...
30
31
32
33
34
35
36
37
38// turn off some warnings that are noisy about our Expects statements
39// conditional expression is constant
40
41 // unary minus operator applied to unsigned type, result still unsigned
42// unreachable code
43
44// Turn MSVC /analyze rules that generate too much noise. TODO: fix in the tool.
45// uninitalized member when constructor calls constructor
46// parser bug does not allow attributes on some templates
47
48// _MSC_VER
49
50// See if we have enough C++17 power to use a static constexpr data member
51// without needing an out-of-line definition
52
53
54// !(defined(__cplusplus) && (__cplusplus >= 201703L))
55
56// GCC 7 does not like the signed unsigned missmatch (size_t ptrdiff_t)
57// While there is a conversion from signed to unsigned, it happens at
58// compiletime, so the compiler wouldn't have to warn indiscriminately, but
59// could check if the source value actually doesn't fit into the target type
60// and only warn in those cases.
61
62
63
64
65
66namespace gsl
67{
68
69// implementation details
70namespace details
71{
72 template <class T>
73 struct is_span_oracle : std::false_type
74 {
75 };
76
77 template <class ElementType, std::size_t Extent>
78 struct is_span_oracle<gsl::span<ElementType, Extent>> : std::true_type
79 {
80 };
81
82 template <class T>
83 struct is_span : public is_span_oracle<std::remove_cv_t<T>>
84 {
85 };
86
87 template <class T>
88 struct is_std_array_oracle : std::false_type
89 {
90 };
91
92 template <class ElementType, std::size_t Extent>
93 struct is_std_array_oracle<std::array<ElementType, Extent>> : std::true_type
94 {
95 };
96
97 template <class T>
98 struct is_std_array : is_std_array_oracle<std::remove_cv_t<T>>
99 {
100 };
101
102 template <std::size_t From, std::size_t To>
103 struct is_allowed_extent_conversion
104 : std::integral_constant<bool, From == To || To == dynamic_extent>
105 {
106 };
107
108 template <class From, class To>
109 struct is_allowed_element_type_conversion
110 : std::integral_constant<bool, std::is_convertible<From (*)[], To (*)[]>::value>
111 {
112 };
113
114 template <class Type>
115 class span_iterator
116 {
117 public:
118
119 using iterator_concept = std::contiguous_iterator_tag;
120// __cpp_lib_ranges
121 using iterator_category = std::random_access_iterator_tag;
122 using value_type = std::remove_cv_t<Type>;
123 using difference_type = std::ptrdiff_t;
124 using pointer = Type*;
125 using reference = Type&;
126
127
128 using _Unchecked_type = pointer;
129// _MSC_VER
130 constexpr span_iterator() = default;
131
132 constexpr span_iterator(pointer begin, pointer end, pointer current)
133 : begin_(begin), end_(end), current_(current)
134 {}
135
136 constexpr operator span_iterator<const Type>() const noexcept
137 {
138 return {begin_, end_, current_};
139 }
140
141 constexpr reference operator*() const noexcept
142 {
143 Expects(begin_ && end_);
144 Expects(begin_ <= current_ && current_ < end_);
145 return *current_;
146 }
147
148 constexpr pointer operator->() const noexcept
149 {
150 Expects(begin_ && end_);
151 Expects(begin_ <= current_ && current_ < end_);
152 return current_;
153 }
154 constexpr span_iterator& operator++() noexcept
155 {
156 Expects(begin_ && current_ && end_);
157 Expects(current_ < end_);
158 // clang-format off
159 GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
160 // clang-format on
161 ++current_;
162 return *this;
163 }
164
165 constexpr span_iterator operator++(int) noexcept
166 {
167 span_iterator ret = *this;
168 ++*this;
169 return ret;
170 }
171
172 constexpr span_iterator& operator--() noexcept
173 {
174 Expects(begin_ && end_);
175 Expects(begin_ < current_);
176 --current_;
177 return *this;
178 }
179
180 constexpr span_iterator operator--(int) noexcept
181 {
182 span_iterator ret = *this;
183 --*this;
184 return ret;
185 }
186
187 constexpr span_iterator& operator+=(const difference_type n) noexcept
188 {
189 if (n != 0) Expects(begin_ && current_ && end_);
190 if (n > 0) Expects(end_ - current_ >= n);
191 if (n < 0) Expects(current_ - begin_ >= -n);
192 // clang-format off
193 GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
194 // clang-format on
195 current_ += n;
196 return *this;
197 }
198
199 constexpr span_iterator operator+(const difference_type n) const noexcept
200 {
201 span_iterator ret = *this;
202 ret += n;
203 return ret;
204 }
205
206 friend constexpr span_iterator operator+(const difference_type n,
207 const span_iterator& rhs) noexcept
208 {
209 return rhs + n;
210 }
211
212 constexpr span_iterator& operator-=(const difference_type n) noexcept
213 {
214 if (n != 0) Expects(begin_ && current_ && end_);
215 if (n > 0) Expects(current_ - begin_ >= n);
216 if (n < 0) Expects(end_ - current_ >= -n);
217 current_ -= n;
218 return *this;
219 }
220
221 constexpr span_iterator operator-(const difference_type n) const noexcept
222 {
223 span_iterator ret = *this;
224 ret -= n;
225 return ret;
226 }
227
228 template <
229 class Type2,
230 std::enable_if_t<std::is_same<std::remove_cv_t<Type2>, value_type>::value, int> = 0>
231 constexpr difference_type operator-(const span_iterator<Type2>& rhs) const noexcept
232 {
233 Expects(begin_ == rhs.begin_ && end_ == rhs.end_);
234 return current_ - rhs.current_;
235 }
236
237 constexpr reference operator[](const difference_type n) const noexcept
238 {
239 return *(*this + n);
240 }
241
242 template <
243 class Type2,
244 std::enable_if_t<std::is_same<std::remove_cv_t<Type2>, value_type>::value, int> = 0>
245 constexpr bool operator==(const span_iterator<Type2>& rhs) const noexcept
246 {
247 Expects(begin_ == rhs.begin_ && end_ == rhs.end_);
248 return current_ == rhs.current_;
249 }
250
251 template <
252 class Type2,
253 std::enable_if_t<std::is_same<std::remove_cv_t<Type2>, value_type>::value, int> = 0>
254 constexpr bool operator!=(const span_iterator<Type2>& rhs) const noexcept
255 {
256 return !(*this == rhs);
257 }
258
259 template <
260 class Type2,
261 std::enable_if_t<std::is_same<std::remove_cv_t<Type2>, value_type>::value, int> = 0>
262 constexpr bool operator<(const span_iterator<Type2>& rhs) const noexcept
263 {
264 Expects(begin_ == rhs.begin_ && end_ == rhs.end_);
265 return current_ < rhs.current_;
266 }
267
268 template <
269 class Type2,
270 std::enable_if_t<std::is_same<std::remove_cv_t<Type2>, value_type>::value, int> = 0>
271 constexpr bool operator>(const span_iterator<Type2>& rhs) const noexcept
272 {
273 return rhs < *this;
274 }
275
276 template <
277 class Type2,
278 std::enable_if_t<std::is_same<std::remove_cv_t<Type2>, value_type>::value, int> = 0>
279 constexpr bool operator<=(const span_iterator<Type2>& rhs) const noexcept
280 {
281 return !(rhs < *this);
282 }
283
284 template <
285 class Type2,
286 std::enable_if_t<std::is_same<std::remove_cv_t<Type2>, value_type>::value, int> = 0>
287 constexpr bool operator>=(const span_iterator<Type2>& rhs) const noexcept
288 {
289 return !(*this < rhs);
290 }
291
292
293 // MSVC++ iterator debugging support; allows STL algorithms in 15.8+
294 // to unwrap span_iterator to a pointer type after a range check in STL
295 // algorithm calls
296 friend constexpr void _Verify_range(span_iterator lhs, span_iterator rhs) noexcept
297 { // test that [lhs, rhs) forms a valid range inside an STL algorithm
298 Expects(lhs.begin_ == rhs.begin_ // range spans have to match
299 && lhs.end_ == rhs.end_ &&
300 lhs.current_ <= rhs.current_); // range must not be transposed
301 }
302
303 constexpr void _Verify_offset(const difference_type n) const noexcept
304 { // test that *this + n is within the range of this call
305 if (n != 0) Expects(begin_ && current_ && end_);
306 if (n > 0) Expects(end_ - current_ >= n);
307 if (n < 0) Expects(current_ - begin_ >= -n);
308 }
309
310 // clang-format off
311 GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
312 // clang-format on
313 constexpr pointer _Unwrapped() const noexcept
314 { // after seeking *this to a high water mark, or using one of the
315 // _Verify_xxx functions above, unwrap this span_iterator to a raw
316 // pointer
317 return current_;
318 }
319
320 // Tell the STL that span_iterator should not be unwrapped if it can't
321 // validate in advance, even in release / optimized builds:
322
323 static constexpr const bool _Unwrap_when_unverified = false;
324
325 static constexpr bool _Unwrap_when_unverified = false;
326
327 // clang-format off
328 GSL_SUPPRESS(con.3) // NO-FORMAT: attribute // TODO: false positive
329 // clang-format on
330 constexpr void _Seek_to(const pointer p) noexcept
331 { // adjust the position of *this to previously verified location p
332 // after _Unwrapped
333 current_ = p;
334 }
335
336
337 pointer begin_ = nullptr;
338 pointer end_ = nullptr;
339 pointer current_ = nullptr;
340
341 template <typename Ptr>
342 friend struct std::pointer_traits;
343 };
344}} // namespace gsl::details
345
346namespace std
347{
348template <class Type>
349struct pointer_traits<::gsl::details::span_iterator<Type>>
350{
351 using pointer = ::gsl::details::span_iterator<Type>;
352 using element_type = Type;
353 using difference_type = ptrdiff_t;
354
355 static constexpr element_type* to_address(const pointer i) noexcept { return i.current_; }
356};
357} // namespace std
358
359namespace gsl { namespace details {
360 template <std::size_t Ext>
361 class extent_type
362 {
363 public:
364 using size_type = std::size_t;
365
366 constexpr extent_type() noexcept = default;
367
368 constexpr explicit extent_type(extent_type<dynamic_extent>);
369
370 constexpr explicit extent_type(size_type size) { Expects(size == Ext); }
371
372 constexpr size_type size() const noexcept { return Ext; }
373
374 private:
375
376 static constexpr const size_type size_ = Ext; // static size equal to Ext
377
378 static constexpr size_type size_ = Ext; // static size equal to Ext
379
380 };
381
382 template <>
383 class extent_type<dynamic_extent>
384 {
385 public:
386 using size_type = std::size_t;
387
388 template <size_type Other>
389 constexpr explicit extent_type(extent_type<Other> ext) : size_(ext.size())
390 {}
391
392 constexpr explicit extent_type(size_type size) : size_(size)
393 {
394 Expects(size != dynamic_extent);
395 }
396
397 constexpr size_type size() const noexcept { return size_; }
398
399 private:
400 size_type size_;
401 };
402
403 template <std::size_t Ext>
404 constexpr extent_type<Ext>::extent_type(extent_type<dynamic_extent> ext)
405 {
406 Expects(ext.size() == Ext);
407 }
408
409 template <class ElementType, std::size_t Extent, std::size_t Offset, std::size_t Count>
410 struct calculate_subspan_type
411 {
412 using type = span<ElementType, Count != dynamic_extent
413 ? Count
414 : (Extent != dynamic_extent ? Extent - Offset : Extent)>;
415 };
416} // namespace details
417
418// [span], class template span
419template <class ElementType, std::size_t Extent>
420class span
421{
422public:
423 // constants and types
424 using element_type = ElementType;
425 using value_type = std::remove_cv_t<ElementType>;
426 using size_type = std::size_t;
427 using pointer = element_type*;
428 using const_pointer = const element_type*;
429 using reference = element_type&;
430 using const_reference = const element_type&;
431 using difference_type = std::ptrdiff_t;
432
433 using iterator = details::span_iterator<ElementType>;
434 using reverse_iterator = std::reverse_iterator<iterator>;
435
436
437 static constexpr const size_type extent{Extent};
438
439 static constexpr size_type extent{Extent};
440
441
442 // [span.cons], span constructors, copy, assignment, and destructor
443 template <bool Dependent = false,
444 // "Dependent" is needed to make "std::enable_if_t<Dependent || Extent == 0 || Extent
445 // == dynamic_extent>" SFINAE, since "std::enable_if_t<Extent == 0 || Extent ==
446 // dynamic_extent>" is ill-formed when Extent is greater than 0.
447 class = std::enable_if_t<(Dependent ||
448 details::is_allowed_extent_conversion<0, Extent>::value)>>
449 constexpr span() noexcept : storage_(nullptr, details::extent_type<0>())
450 {}
451
452 template <std::size_t MyExtent = Extent, std::enable_if_t<MyExtent != dynamic_extent, int> = 0>
453 constexpr explicit span(pointer ptr, size_type count) noexcept : storage_(ptr, count)
454 {
455 Expects(count == Extent);
456 }
457
458 template <std::size_t MyExtent = Extent, std::enable_if_t<MyExtent == dynamic_extent, int> = 0>
459 constexpr span(pointer ptr, size_type count) noexcept : storage_(ptr, count)
460 {}
461
462 template <std::size_t MyExtent = Extent, std::enable_if_t<MyExtent != dynamic_extent, int> = 0>
463 constexpr explicit span(pointer firstElem, pointer lastElem) noexcept
464 : storage_(firstElem, narrow_cast<std::size_t>(lastElem - firstElem))
465 {
466 Expects(lastElem - firstElem == static_cast<difference_type>(Extent));
467 }
468
469 template <std::size_t MyExtent = Extent, std::enable_if_t<MyExtent == dynamic_extent, int> = 0>
470 constexpr span(pointer firstElem, pointer lastElem) noexcept
471 : storage_(firstElem, narrow_cast<std::size_t>(lastElem - firstElem))
472 {}
473
474 template <std::size_t N,
475 std::enable_if_t<details::is_allowed_extent_conversion<N, Extent>::value, int> = 0>
476 constexpr span(element_type (&arr)[N]) noexcept
477 : storage_(KnownNotNull{arr}, details::extent_type<N>())
478 {}
479
480 template <
481 class T, std::size_t N,
482 std::enable_if_t<(details::is_allowed_extent_conversion<N, Extent>::value &&
483 details::is_allowed_element_type_conversion<T, element_type>::value),
484 int> = 0>
485 constexpr span(std::array<T, N>& arr) noexcept
486 : storage_(KnownNotNull{arr.data()}, details::extent_type<N>())
487 {}
488
489 template <class T, std::size_t N,
490 std::enable_if_t<
491 (details::is_allowed_extent_conversion<N, Extent>::value &&
492 details::is_allowed_element_type_conversion<const T, element_type>::value),
493 int> = 0>
494 constexpr span(const std::array<T, N>& arr) noexcept
495 : storage_(KnownNotNull{arr.data()}, details::extent_type<N>())
496 {}
497
498 // NB: the SFINAE on these constructors uses .data() as an incomplete/imperfect proxy for the
499 // requirement on Container to be a contiguous sequence container.
500 template <std::size_t MyExtent = Extent, class Container,
501 std::enable_if_t<
502 MyExtent != dynamic_extent && !details::is_span<Container>::value &&
503 !details::is_std_array<Container>::value &&
504 std::is_pointer<decltype(std::declval<Container&>().data())>::value &&
505 std::is_convertible<
506 std::remove_pointer_t<decltype(std::declval<Container&>().data())> (*)[],
507 element_type (*)[]>::value,
508 int> = 0>
509 constexpr explicit span(Container& cont) noexcept : span(cont.data(), cont.size())
510 {}
511
512 template <std::size_t MyExtent = Extent, class Container,
513 std::enable_if_t<
514 MyExtent == dynamic_extent && !details::is_span<Container>::value &&
515 !details::is_std_array<Container>::value &&
516 std::is_pointer<decltype(std::declval<Container&>().data())>::value &&
517 std::is_convertible<
518 std::remove_pointer_t<decltype(std::declval<Container&>().data())> (*)[],
519 element_type (*)[]>::value,
520 int> = 0>
521 constexpr span(Container& cont) noexcept : span(cont.data(), cont.size())
522 {}
523
524 template <
525 std::size_t MyExtent = Extent, class Container,
526 std::enable_if_t<
527 MyExtent != dynamic_extent && std::is_const<element_type>::value &&
528 !details::is_span<Container>::value && !details::is_std_array<Container>::value &&
529 std::is_pointer<decltype(std::declval<const Container&>().data())>::value &&
530 std::is_convertible<
531 std::remove_pointer_t<decltype(std::declval<const Container&>().data())> (*)[],
532 element_type (*)[]>::value,
533 int> = 0>
534 constexpr explicit span(const Container& cont) noexcept : span(cont.data(), cont.size())
535 {}
536
537 template <
538 std::size_t MyExtent = Extent, class Container,
539 std::enable_if_t<
540 MyExtent == dynamic_extent && std::is_const<element_type>::value &&
541 !details::is_span<Container>::value && !details::is_std_array<Container>::value &&
542 std::is_pointer<decltype(std::declval<const Container&>().data())>::value &&
543 std::is_convertible<
544 std::remove_pointer_t<decltype(std::declval<const Container&>().data())> (*)[],
545 element_type (*)[]>::value,
546 int> = 0>
547 constexpr span(const Container& cont) noexcept : span(cont.data(), cont.size())
548 {}
549
550 constexpr span(const span& other) noexcept = default;
551
552 template <class OtherElementType, std::size_t OtherExtent, std::size_t MyExtent = Extent,
553 std::enable_if_t<(MyExtent == dynamic_extent || MyExtent == OtherExtent) &&
554 details::is_allowed_element_type_conversion<OtherElementType,
555 element_type>::value,
556 int> = 0>
557 constexpr span(const span<OtherElementType, OtherExtent>& other) noexcept
558 : storage_(other.data(), details::extent_type<OtherExtent>(other.size()))
559 {}
560
561 template <class OtherElementType, std::size_t OtherExtent, std::size_t MyExtent = Extent,
562 std::enable_if_t<MyExtent != dynamic_extent && OtherExtent == dynamic_extent &&
563 details::is_allowed_element_type_conversion<OtherElementType,
564 element_type>::value,
565 int> = 0>
566 constexpr explicit span(const span<OtherElementType, OtherExtent>& other) noexcept
567 : storage_(other.data(), details::extent_type<OtherExtent>(other.size()))
568 {}
569
570 ~span() noexcept = default;
571 constexpr span& operator=(const span& other) noexcept = default;
572
573 // [span.sub], span subviews
574 template <std::size_t Count>
575 constexpr span<element_type, Count> first() const noexcept
576 {
577 Expects(Count <= size());
578 return span<element_type, Count>{data(), Count};
579 }
580
581 template <std::size_t Count>
582 // clang-format off
583 GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
584 // clang-format on
585 constexpr span<element_type, Count> last() const noexcept
586 {
587 Expects(Count <= size());
588 return span<element_type, Count>{data() + (size() - Count), Count};
589 }
590
591 template <std::size_t Offset, std::size_t Count = dynamic_extent>
592 // clang-format off
593 GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
594 // clang-format on
595 constexpr auto subspan() const noexcept ->
596 typename details::calculate_subspan_type<ElementType, Extent, Offset, Count>::type
597 {
598 Expects((size() >= Offset) && (Count == dynamic_extent || (Count <= size() - Offset)));
599 using type =
600 typename details::calculate_subspan_type<ElementType, Extent, Offset, Count>::type;
601 return type{data() + Offset, Count == dynamic_extent ? size() - Offset : Count};
602 }
603
604 constexpr span<element_type, dynamic_extent> first(size_type count) const noexcept
605 {
606 Expects(count <= size());
607 return {data(), count};
608 }
609
610 constexpr span<element_type, dynamic_extent> last(size_type count) const noexcept
611 {
612 Expects(count <= size());
613 return make_subspan(size() - count, dynamic_extent, subspan_selector<Extent>{});
614 }
615
616 constexpr span<element_type, dynamic_extent>
617 subspan(size_type offset, size_type count = dynamic_extent) const noexcept
618 {
619 return make_subspan(offset, count, subspan_selector<Extent>{});
620 }
621
622 // [span.obs], span observers
623 constexpr size_type size() const noexcept { return storage_.size(); }
624
625 constexpr size_type size_bytes() const noexcept
626 {
627 Expects(size() < dynamic_extent / sizeof(element_type));
628 return size() * sizeof(element_type);
629 }
630
631 constexpr bool empty() const noexcept { return size() == 0; }
632
633 // [span.elem], span element access
634 // clang-format off
635 GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
636 // clang-format on
637 constexpr reference operator[](size_type idx) const noexcept
638 {
639 Expects(idx < size());
640 return data()[idx];
641 }
642
643 constexpr reference front() const noexcept
644 {
645 Expects(size() > 0);
646 return data()[0];
647 }
648
649 constexpr reference back() const noexcept
650 {
651 Expects(size() > 0);
652 return data()[size() - 1];
653 }
654
655 constexpr pointer data() const noexcept { return storage_.data(); }
656
657 // [span.iter], span iterator support
658 constexpr iterator begin() const noexcept
659 {
660 const auto data = storage_.data();
661 // clang-format off
662 GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
663 // clang-format on
664 return {data, data + size(), data};
665 }
666
667 constexpr iterator end() const noexcept
668 {
669 const auto data = storage_.data();
670 // clang-format off
671 GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
672 // clang-format on
673 const auto endData = data + storage_.size();
674 return {data, endData, endData};
675 }
676
677 constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator{end()}; }
678 constexpr reverse_iterator rend() const noexcept { return reverse_iterator{begin()}; }
679
680
681 // Tell MSVC how to unwrap spans in range-based-for
682 constexpr pointer _Unchecked_begin() const noexcept { return data(); }
683 constexpr pointer _Unchecked_end() const noexcept
684 {
685 // clang-format off
686 GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
687 // clang-format on
688 return data() + size();
689 }
690// _MSC_VER
691
692private:
693 // Needed to remove unnecessary null check in subspans
694 struct KnownNotNull
695 {
696 pointer p;
697 };
698
699 // this implementation detail class lets us take advantage of the
700 // empty base class optimization to pay for only storage of a single
701 // pointer in the case of fixed-size spans
702 template <class ExtentType>
703 class storage_type : public ExtentType
704 {
705 public:
706 // KnownNotNull parameter is needed to remove unnecessary null check
707 // in subspans and constructors from arrays
708 template <class OtherExtentType>
709 constexpr storage_type(KnownNotNull data, OtherExtentType ext)
710 : ExtentType(ext), data_(data.p)
711 {}
712
713 template <class OtherExtentType>
714 constexpr storage_type(pointer data, OtherExtentType ext) : ExtentType(ext), data_(data)
715 {
716 Expects(data || ExtentType::size() == 0);
717 }
718
719 constexpr pointer data() const noexcept { return data_; }
720
721 private:
722 pointer data_;
723 };
724
725 storage_type<details::extent_type<Extent>> storage_;
726
727 // The rest is needed to remove unnecessary null check
728 // in subspans and constructors from arrays
729 constexpr span(KnownNotNull ptr, size_type count) noexcept : storage_(ptr, count) {}
730
731 template <std::size_t CallerExtent>
732 class subspan_selector
733 {
734 };
735
736 template <std::size_t CallerExtent>
737 constexpr span<element_type, dynamic_extent>
738 make_subspan(size_type offset, size_type count, subspan_selector<CallerExtent>) const noexcept
739 {
740 const span<element_type, dynamic_extent> tmp(*this);
741 return tmp.subspan(offset, count);
742 }
743
744 // clang-format off
745 GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
746 // clang-format on
747 constexpr span<element_type, dynamic_extent>
748 make_subspan(size_type offset, size_type count, subspan_selector<dynamic_extent>) const noexcept
749 {
750 Expects(size() >= offset);
751
752 if (count == dynamic_extent) { return {KnownNotNull{data() + offset}, size() - offset}; }
753
754 Expects(size() - offset >= count);
755 return {KnownNotNull{data() + offset}, count};
756 }
757};
758
759
760
761// Deduction Guides
762template <class Type, std::size_t Extent>
763span(Type (&)[Extent]) -> span<Type, Extent>;
764
765template <class Type, std::size_t Size>
766span(std::array<Type, Size>&) -> span<Type, Size>;
767
768template <class Type, std::size_t Size>
769span(const std::array<Type, Size>&) -> span<const Type, Size>;
770
771template <class Container,
772 class Element = std::remove_pointer_t<decltype(std::declval<Container&>().data())>>
773span(Container&) -> span<Element>;
774
775template <class Container,
776 class Element = std::remove_pointer_t<decltype(std::declval<const Container&>().data())>>
777span(const Container&) -> span<Element>;
778
779// ( defined(__cpp_deduction_guides) && (__cpp_deduction_guides >= 201611L) )
780
781
782template <class ElementType, std::size_t Extent>
783constexpr const typename span<ElementType, Extent>::size_type span<ElementType, Extent>::extent;
784
785
786namespace details
787{
788 // if we only supported compilers with good constexpr support then
789 // this pair of classes could collapse down to a constexpr function
790
791 // we should use a narrow_cast<> to go to std::size_t, but older compilers may not see it as
792 // constexpr
793 // and so will fail compilation of the template
794 template <class ElementType, std::size_t Extent>
795 struct calculate_byte_size : std::integral_constant<std::size_t, sizeof(ElementType) * Extent>
796 {
797 static_assert(Extent < dynamic_extent / sizeof(ElementType), "Size is too big.");
798 };
799
800 template <class ElementType>
801 struct calculate_byte_size<ElementType, dynamic_extent>
802 : std::integral_constant<std::size_t, dynamic_extent>
803 {
804 };
805} // namespace details
806
807// [span.objectrep], views of object representation
808template <class ElementType, std::size_t Extent>
809span<const byte, details::calculate_byte_size<ElementType, Extent>::value>
810as_bytes(span<ElementType, Extent> s) noexcept
811{
812 using type = span<const byte, details::calculate_byte_size<ElementType, Extent>::value>;
813
814 // clang-format off
815 GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
816 // clang-format on
817 return type{reinterpret_cast<const byte*>(s.data()), s.size_bytes()};
818}
819
820template <class ElementType, std::size_t Extent,
821 std::enable_if_t<!std::is_const<ElementType>::value, int> = 0>
822span<byte, details::calculate_byte_size<ElementType, Extent>::value>
823as_writable_bytes(span<ElementType, Extent> s) noexcept
824{
825 using type = span<byte, details::calculate_byte_size<ElementType, Extent>::value>;
826
827 // clang-format off
828 GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
829 // clang-format on
830 return type{reinterpret_cast<byte*>(s.data()), s.size_bytes()};
831}
832
833} // namespace gsl
834
835
836
837
838// _MSC_VER
839
840
841
842// __GNUC__ > 6
843
844// GSL_SPAN_H