libstdc++
string_view
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1 // Components for manipulating non-owning sequences of characters -*- C++ -*-
2 
3 // Copyright (C) 2013-2021 Free Software Foundation, Inc.
4 //
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10 
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16 // Under Section 7 of GPL version 3, you are granted additional
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24 
25 /** @file include/string_view
26  * This is a Standard C++ Library header.
27  */
28 
29 //
30 // N3762 basic_string_view library
31 //
32 
33 #ifndef _GLIBCXX_STRING_VIEW
34 #define _GLIBCXX_STRING_VIEW 1
35 
36 #pragma GCC system_header
37 
38 #if __cplusplus >= 201703L
39 
40 #include <iosfwd>
41 #include <bits/char_traits.h>
42 #include <bits/functional_hash.h>
43 #include <bits/range_access.h>
44 #include <bits/ostream_insert.h>
45 #include <ext/numeric_traits.h>
46 
47 #if __cplusplus >= 202002L
48 # include <bits/ranges_base.h>
49 #endif
50 
51 namespace std _GLIBCXX_VISIBILITY(default)
52 {
53 _GLIBCXX_BEGIN_NAMESPACE_VERSION
54 
55 # define __cpp_lib_string_view 201803L
56 #if __cplusplus > 201703L
57 # define __cpp_lib_constexpr_string_view 201811L
58 #endif
59 
60  // Helper for basic_string and basic_string_view members.
61  constexpr size_t
62  __sv_check(size_t __size, size_t __pos, const char* __s)
63  {
64  if (__pos > __size)
65  __throw_out_of_range_fmt(__N("%s: __pos (which is %zu) > __size "
66  "(which is %zu)"), __s, __pos, __size);
67  return __pos;
68  }
69 
70  // Helper for basic_string members.
71  // NB: __sv_limit doesn't check for a bad __pos value.
72  constexpr size_t
73  __sv_limit(size_t __size, size_t __pos, size_t __off) noexcept
74  {
75  const bool __testoff = __off < __size - __pos;
76  return __testoff ? __off : __size - __pos;
77  }
78 
79  /**
80  * @class basic_string_view <string_view>
81  * @brief A non-owning reference to a string.
82  *
83  * @ingroup strings
84  * @ingroup sequences
85  *
86  * @tparam _CharT Type of character
87  * @tparam _Traits Traits for character type, defaults to
88  * char_traits<_CharT>.
89  *
90  * A basic_string_view looks like this:
91  *
92  * @code
93  * _CharT* _M_str
94  * size_t _M_len
95  * @endcode
96  */
97  template<typename _CharT, typename _Traits = std::char_traits<_CharT>>
98  class basic_string_view
99  {
100  static_assert(!is_array_v<_CharT>);
101  static_assert(is_trivial_v<_CharT> && is_standard_layout_v<_CharT>);
102  static_assert(is_same_v<_CharT, typename _Traits::char_type>);
103 
104  public:
105 
106  // types
107  using traits_type = _Traits;
108  using value_type = _CharT;
109  using pointer = value_type*;
110  using const_pointer = const value_type*;
111  using reference = value_type&;
112  using const_reference = const value_type&;
113  using const_iterator = const value_type*;
114  using iterator = const_iterator;
115  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
116  using reverse_iterator = const_reverse_iterator;
117  using size_type = size_t;
118  using difference_type = ptrdiff_t;
119  static constexpr size_type npos = size_type(-1);
120 
121  // [string.view.cons], construction and assignment
122 
123  constexpr
124  basic_string_view() noexcept
125  : _M_len{0}, _M_str{nullptr}
126  { }
127 
128  constexpr basic_string_view(const basic_string_view&) noexcept = default;
129 
130  __attribute__((__nonnull__)) constexpr
131  basic_string_view(const _CharT* __str) noexcept
132  : _M_len{traits_type::length(__str)},
133  _M_str{__str}
134  { }
135 
136  constexpr
137  basic_string_view(const _CharT* __str, size_type __len) noexcept
138  : _M_len{__len}, _M_str{__str}
139  { }
140 
141 #if __cplusplus >= 202002L && __cpp_lib_concepts
142  template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
143  requires same_as<iter_value_t<_It>, _CharT>
144  && (!convertible_to<_End, size_type>)
145  constexpr
146  basic_string_view(_It __first, _End __last)
147  noexcept(noexcept(__last - __first))
148  : _M_len(__last - __first), _M_str(std::to_address(__first))
149  { }
150 
151 #if __cplusplus > 202002L
152  template<typename _Range, typename _DRange = remove_cvref_t<_Range>>
153  requires (!is_same_v<_DRange, basic_string_view>)
154  && ranges::contiguous_range<_Range>
155  && ranges::sized_range<_Range>
156  && is_same_v<ranges::range_value_t<_Range>, _CharT>
157  && (!is_convertible_v<_Range, const _CharT*>)
158  && (!requires (_DRange& __d) {
159  __d.operator ::std::basic_string_view<_CharT, _Traits>();
160  })
161  && (!requires { typename _DRange::traits_type; }
162  || is_same_v<typename _DRange::traits_type, _Traits>)
163  constexpr
164  basic_string_view(_Range&& __r)
165  noexcept(noexcept(ranges::size(__r)) && noexcept(ranges::data(__r)))
166  : _M_len(ranges::size(__r)), _M_str(ranges::data(__r))
167  { }
168 #endif // C++23
169 #endif // C++20
170 
171  constexpr basic_string_view&
172  operator=(const basic_string_view&) noexcept = default;
173 
174  // [string.view.iterators], iterator support
175 
176  constexpr const_iterator
177  begin() const noexcept
178  { return this->_M_str; }
179 
180  constexpr const_iterator
181  end() const noexcept
182  { return this->_M_str + this->_M_len; }
183 
184  constexpr const_iterator
185  cbegin() const noexcept
186  { return this->_M_str; }
187 
188  constexpr const_iterator
189  cend() const noexcept
190  { return this->_M_str + this->_M_len; }
191 
192  constexpr const_reverse_iterator
193  rbegin() const noexcept
194  { return const_reverse_iterator(this->end()); }
195 
196  constexpr const_reverse_iterator
197  rend() const noexcept
198  { return const_reverse_iterator(this->begin()); }
199 
200  constexpr const_reverse_iterator
201  crbegin() const noexcept
202  { return const_reverse_iterator(this->end()); }
203 
204  constexpr const_reverse_iterator
205  crend() const noexcept
206  { return const_reverse_iterator(this->begin()); }
207 
208  // [string.view.capacity], capacity
209 
210  constexpr size_type
211  size() const noexcept
212  { return this->_M_len; }
213 
214  constexpr size_type
215  length() const noexcept
216  { return _M_len; }
217 
218  constexpr size_type
219  max_size() const noexcept
220  {
221  return (npos - sizeof(size_type) - sizeof(void*))
222  / sizeof(value_type) / 4;
223  }
224 
225  [[nodiscard]] constexpr bool
226  empty() const noexcept
227  { return this->_M_len == 0; }
228 
229  // [string.view.access], element access
230 
231  constexpr const_reference
232  operator[](size_type __pos) const noexcept
233  {
234  __glibcxx_assert(__pos < this->_M_len);
235  return *(this->_M_str + __pos);
236  }
237 
238  constexpr const_reference
239  at(size_type __pos) const
240  {
241  if (__pos >= _M_len)
242  __throw_out_of_range_fmt(__N("basic_string_view::at: __pos "
243  "(which is %zu) >= this->size() "
244  "(which is %zu)"), __pos, this->size());
245  return *(this->_M_str + __pos);
246  }
247 
248  constexpr const_reference
249  front() const noexcept
250  {
251  __glibcxx_assert(this->_M_len > 0);
252  return *this->_M_str;
253  }
254 
255  constexpr const_reference
256  back() const noexcept
257  {
258  __glibcxx_assert(this->_M_len > 0);
259  return *(this->_M_str + this->_M_len - 1);
260  }
261 
262  constexpr const_pointer
263  data() const noexcept
264  { return this->_M_str; }
265 
266  // [string.view.modifiers], modifiers:
267 
268  constexpr void
269  remove_prefix(size_type __n) noexcept
270  {
271  __glibcxx_assert(this->_M_len >= __n);
272  this->_M_str += __n;
273  this->_M_len -= __n;
274  }
275 
276  constexpr void
277  remove_suffix(size_type __n) noexcept
278  { this->_M_len -= __n; }
279 
280  constexpr void
281  swap(basic_string_view& __sv) noexcept
282  {
283  auto __tmp = *this;
284  *this = __sv;
285  __sv = __tmp;
286  }
287 
288  // [string.view.ops], string operations:
289 
290  _GLIBCXX20_CONSTEXPR
291  size_type
292  copy(_CharT* __str, size_type __n, size_type __pos = 0) const
293  {
294  __glibcxx_requires_string_len(__str, __n);
295  __pos = std::__sv_check(size(), __pos, "basic_string_view::copy");
296  const size_type __rlen = std::min(__n, _M_len - __pos);
297  // _GLIBCXX_RESOLVE_LIB_DEFECTS
298  // 2777. basic_string_view::copy should use char_traits::copy
299  traits_type::copy(__str, data() + __pos, __rlen);
300  return __rlen;
301  }
302 
303  constexpr basic_string_view
304  substr(size_type __pos = 0, size_type __n = npos) const noexcept(false)
305  {
306  __pos = std::__sv_check(size(), __pos, "basic_string_view::substr");
307  const size_type __rlen = std::min(__n, _M_len - __pos);
308  return basic_string_view{_M_str + __pos, __rlen};
309  }
310 
311  constexpr int
312  compare(basic_string_view __str) const noexcept
313  {
314  const size_type __rlen = std::min(this->_M_len, __str._M_len);
315  int __ret = traits_type::compare(this->_M_str, __str._M_str, __rlen);
316  if (__ret == 0)
317  __ret = _S_compare(this->_M_len, __str._M_len);
318  return __ret;
319  }
320 
321  constexpr int
322  compare(size_type __pos1, size_type __n1, basic_string_view __str) const
323  { return this->substr(__pos1, __n1).compare(__str); }
324 
325  constexpr int
326  compare(size_type __pos1, size_type __n1,
327  basic_string_view __str, size_type __pos2, size_type __n2) const
328  {
329  return this->substr(__pos1, __n1).compare(__str.substr(__pos2, __n2));
330  }
331 
332  __attribute__((__nonnull__)) constexpr int
333  compare(const _CharT* __str) const noexcept
334  { return this->compare(basic_string_view{__str}); }
335 
336  __attribute__((__nonnull__)) constexpr int
337  compare(size_type __pos1, size_type __n1, const _CharT* __str) const
338  { return this->substr(__pos1, __n1).compare(basic_string_view{__str}); }
339 
340  constexpr int
341  compare(size_type __pos1, size_type __n1,
342  const _CharT* __str, size_type __n2) const noexcept(false)
343  {
344  return this->substr(__pos1, __n1)
345  .compare(basic_string_view(__str, __n2));
346  }
347 
348 #if __cplusplus > 201703L
349 #define __cpp_lib_starts_ends_with 201711L
350  constexpr bool
351  starts_with(basic_string_view __x) const noexcept
352  { return this->substr(0, __x.size()) == __x; }
353 
354  constexpr bool
355  starts_with(_CharT __x) const noexcept
356  { return !this->empty() && traits_type::eq(this->front(), __x); }
357 
358  constexpr bool
359  starts_with(const _CharT* __x) const noexcept
360  { return this->starts_with(basic_string_view(__x)); }
361 
362  constexpr bool
363  ends_with(basic_string_view __x) const noexcept
364  {
365  const auto __len = this->size();
366  const auto __xlen = __x.size();
367  return __len >= __xlen
368  && traits_type::compare(end() - __xlen, __x.data(), __xlen) == 0;
369  }
370 
371  constexpr bool
372  ends_with(_CharT __x) const noexcept
373  { return !this->empty() && traits_type::eq(this->back(), __x); }
374 
375  constexpr bool
376  ends_with(const _CharT* __x) const noexcept
377  { return this->ends_with(basic_string_view(__x)); }
378 #endif // C++20
379 
380 #if __cplusplus > 202002L
381 #define __cpp_lib_string_contains 202011L
382  constexpr bool
383  contains(basic_string_view __x) const noexcept
384  { return this->find(__x) != npos; }
385 
386  constexpr bool
387  contains(_CharT __x) const noexcept
388  { return this->find(__x) != npos; }
389 
390  constexpr bool
391  contains(const _CharT* __x) const noexcept
392  { return this->find(__x) != npos; }
393 #endif // C++23
394 
395  // [string.view.find], searching
396 
397  constexpr size_type
398  find(basic_string_view __str, size_type __pos = 0) const noexcept
399  { return this->find(__str._M_str, __pos, __str._M_len); }
400 
401  constexpr size_type
402  find(_CharT __c, size_type __pos = 0) const noexcept;
403 
404  constexpr size_type
405  find(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
406 
407  __attribute__((__nonnull__)) constexpr size_type
408  find(const _CharT* __str, size_type __pos = 0) const noexcept
409  { return this->find(__str, __pos, traits_type::length(__str)); }
410 
411  constexpr size_type
412  rfind(basic_string_view __str, size_type __pos = npos) const noexcept
413  { return this->rfind(__str._M_str, __pos, __str._M_len); }
414 
415  constexpr size_type
416  rfind(_CharT __c, size_type __pos = npos) const noexcept;
417 
418  constexpr size_type
419  rfind(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
420 
421  __attribute__((__nonnull__)) constexpr size_type
422  rfind(const _CharT* __str, size_type __pos = npos) const noexcept
423  { return this->rfind(__str, __pos, traits_type::length(__str)); }
424 
425  constexpr size_type
426  find_first_of(basic_string_view __str, size_type __pos = 0) const noexcept
427  { return this->find_first_of(__str._M_str, __pos, __str._M_len); }
428 
429  constexpr size_type
430  find_first_of(_CharT __c, size_type __pos = 0) const noexcept
431  { return this->find(__c, __pos); }
432 
433  constexpr size_type
434  find_first_of(const _CharT* __str, size_type __pos,
435  size_type __n) const noexcept;
436 
437  __attribute__((__nonnull__)) constexpr size_type
438  find_first_of(const _CharT* __str, size_type __pos = 0) const noexcept
439  { return this->find_first_of(__str, __pos, traits_type::length(__str)); }
440 
441  constexpr size_type
442  find_last_of(basic_string_view __str,
443  size_type __pos = npos) const noexcept
444  { return this->find_last_of(__str._M_str, __pos, __str._M_len); }
445 
446  constexpr size_type
447  find_last_of(_CharT __c, size_type __pos=npos) const noexcept
448  { return this->rfind(__c, __pos); }
449 
450  constexpr size_type
451  find_last_of(const _CharT* __str, size_type __pos,
452  size_type __n) const noexcept;
453 
454  __attribute__((__nonnull__)) constexpr size_type
455  find_last_of(const _CharT* __str, size_type __pos = npos) const noexcept
456  { return this->find_last_of(__str, __pos, traits_type::length(__str)); }
457 
458  constexpr size_type
459  find_first_not_of(basic_string_view __str,
460  size_type __pos = 0) const noexcept
461  { return this->find_first_not_of(__str._M_str, __pos, __str._M_len); }
462 
463  constexpr size_type
464  find_first_not_of(_CharT __c, size_type __pos = 0) const noexcept;
465 
466  constexpr size_type
467  find_first_not_of(const _CharT* __str,
468  size_type __pos, size_type __n) const noexcept;
469 
470  __attribute__((__nonnull__)) constexpr size_type
471  find_first_not_of(const _CharT* __str, size_type __pos = 0) const noexcept
472  {
473  return this->find_first_not_of(__str, __pos,
474  traits_type::length(__str));
475  }
476 
477  constexpr size_type
478  find_last_not_of(basic_string_view __str,
479  size_type __pos = npos) const noexcept
480  { return this->find_last_not_of(__str._M_str, __pos, __str._M_len); }
481 
482  constexpr size_type
483  find_last_not_of(_CharT __c, size_type __pos = npos) const noexcept;
484 
485  constexpr size_type
486  find_last_not_of(const _CharT* __str,
487  size_type __pos, size_type __n) const noexcept;
488 
489  __attribute__((__nonnull__)) constexpr size_type
490  find_last_not_of(const _CharT* __str,
491  size_type __pos = npos) const noexcept
492  {
493  return this->find_last_not_of(__str, __pos,
494  traits_type::length(__str));
495  }
496 
497  private:
498 
499  static constexpr int
500  _S_compare(size_type __n1, size_type __n2) noexcept
501  {
502  using __limits = __gnu_cxx::__int_traits<int>;
503  const difference_type __diff = __n1 - __n2;
504  if (__diff > __limits::__max)
505  return __limits::__max;
506  if (__diff < __limits::__min)
507  return __limits::__min;
508  return static_cast<int>(__diff);
509  }
510 
511  size_t _M_len;
512  const _CharT* _M_str;
513  };
514 
515 #if __cplusplus > 201703L && __cpp_lib_concepts && __cpp_deduction_guides
516  template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
517  basic_string_view(_It, _End) -> basic_string_view<iter_value_t<_It>>;
518 
519 #if __cplusplus > 202002L
520  template<ranges::contiguous_range _Range>
521  basic_string_view(_Range&&)
522  -> basic_string_view<ranges::range_value_t<_Range>>;
523 #endif
524 #endif
525 
526  // [string.view.comparison], non-member basic_string_view comparison function
527 
528  // Several of these functions use type_identity_t to create a non-deduced
529  // context, so that only one argument participates in template argument
530  // deduction and the other argument gets implicitly converted to the deduced
531  // type (see N3766).
532 
533  template<typename _CharT, typename _Traits>
534  constexpr bool
535  operator==(basic_string_view<_CharT, _Traits> __x,
536  basic_string_view<_CharT, _Traits> __y) noexcept
537  { return __x.size() == __y.size() && __x.compare(__y) == 0; }
538 
539  template<typename _CharT, typename _Traits>
540  constexpr bool
541  operator==(basic_string_view<_CharT, _Traits> __x,
542  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
543  noexcept
544  { return __x.size() == __y.size() && __x.compare(__y) == 0; }
545 
546 #if __cpp_lib_three_way_comparison
547  template<typename _CharT, typename _Traits>
548  constexpr auto
549  operator<=>(basic_string_view<_CharT, _Traits> __x,
550  basic_string_view<_CharT, _Traits> __y) noexcept
551  -> decltype(__detail::__char_traits_cmp_cat<_Traits>(0))
552  { return __detail::__char_traits_cmp_cat<_Traits>(__x.compare(__y)); }
553 
554  template<typename _CharT, typename _Traits>
555  constexpr auto
556  operator<=>(basic_string_view<_CharT, _Traits> __x,
557  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
558  noexcept
559  -> decltype(__detail::__char_traits_cmp_cat<_Traits>(0))
560  { return __detail::__char_traits_cmp_cat<_Traits>(__x.compare(__y)); }
561 #else
562  template<typename _CharT, typename _Traits>
563  constexpr bool
564  operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
565  basic_string_view<_CharT, _Traits> __y) noexcept
566  { return __x.size() == __y.size() && __x.compare(__y) == 0; }
567 
568  template<typename _CharT, typename _Traits>
569  constexpr bool
570  operator!=(basic_string_view<_CharT, _Traits> __x,
571  basic_string_view<_CharT, _Traits> __y) noexcept
572  { return !(__x == __y); }
573 
574  template<typename _CharT, typename _Traits>
575  constexpr bool
576  operator!=(basic_string_view<_CharT, _Traits> __x,
577  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
578  noexcept
579  { return !(__x == __y); }
580 
581  template<typename _CharT, typename _Traits>
582  constexpr bool
583  operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
584  basic_string_view<_CharT, _Traits> __y) noexcept
585  { return !(__x == __y); }
586 
587  template<typename _CharT, typename _Traits>
588  constexpr bool
589  operator< (basic_string_view<_CharT, _Traits> __x,
590  basic_string_view<_CharT, _Traits> __y) noexcept
591  { return __x.compare(__y) < 0; }
592 
593  template<typename _CharT, typename _Traits>
594  constexpr bool
595  operator< (basic_string_view<_CharT, _Traits> __x,
596  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
597  noexcept
598  { return __x.compare(__y) < 0; }
599 
600  template<typename _CharT, typename _Traits>
601  constexpr bool
602  operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
603  basic_string_view<_CharT, _Traits> __y) noexcept
604  { return __x.compare(__y) < 0; }
605 
606  template<typename _CharT, typename _Traits>
607  constexpr bool
608  operator> (basic_string_view<_CharT, _Traits> __x,
609  basic_string_view<_CharT, _Traits> __y) noexcept
610  { return __x.compare(__y) > 0; }
611 
612  template<typename _CharT, typename _Traits>
613  constexpr bool
614  operator> (basic_string_view<_CharT, _Traits> __x,
615  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
616  noexcept
617  { return __x.compare(__y) > 0; }
618 
619  template<typename _CharT, typename _Traits>
620  constexpr bool
621  operator> (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
622  basic_string_view<_CharT, _Traits> __y) noexcept
623  { return __x.compare(__y) > 0; }
624 
625  template<typename _CharT, typename _Traits>
626  constexpr bool
627  operator<=(basic_string_view<_CharT, _Traits> __x,
628  basic_string_view<_CharT, _Traits> __y) noexcept
629  { return __x.compare(__y) <= 0; }
630 
631  template<typename _CharT, typename _Traits>
632  constexpr bool
633  operator<=(basic_string_view<_CharT, _Traits> __x,
634  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
635  noexcept
636  { return __x.compare(__y) <= 0; }
637 
638  template<typename _CharT, typename _Traits>
639  constexpr bool
640  operator<=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
641  basic_string_view<_CharT, _Traits> __y) noexcept
642  { return __x.compare(__y) <= 0; }
643 
644  template<typename _CharT, typename _Traits>
645  constexpr bool
646  operator>=(basic_string_view<_CharT, _Traits> __x,
647  basic_string_view<_CharT, _Traits> __y) noexcept
648  { return __x.compare(__y) >= 0; }
649 
650  template<typename _CharT, typename _Traits>
651  constexpr bool
652  operator>=(basic_string_view<_CharT, _Traits> __x,
653  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
654  noexcept
655  { return __x.compare(__y) >= 0; }
656 
657  template<typename _CharT, typename _Traits>
658  constexpr bool
659  operator>=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
660  basic_string_view<_CharT, _Traits> __y) noexcept
661  { return __x.compare(__y) >= 0; }
662 #endif // three-way comparison
663 
664  // [string.view.io], Inserters and extractors
665  template<typename _CharT, typename _Traits>
666  inline basic_ostream<_CharT, _Traits>&
667  operator<<(basic_ostream<_CharT, _Traits>& __os,
668  basic_string_view<_CharT,_Traits> __str)
669  { return __ostream_insert(__os, __str.data(), __str.size()); }
670 
671 
672  // basic_string_view typedef names
673 
674  using string_view = basic_string_view<char>;
675 #ifdef _GLIBCXX_USE_WCHAR_T
676  using wstring_view = basic_string_view<wchar_t>;
677 #endif
678 #ifdef _GLIBCXX_USE_CHAR8_T
679  using u8string_view = basic_string_view<char8_t>;
680 #endif
681  using u16string_view = basic_string_view<char16_t>;
682  using u32string_view = basic_string_view<char32_t>;
683 
684  // [string.view.hash], hash support:
685 
686  template<typename _Tp>
687  struct hash;
688 
689  template<>
690  struct hash<string_view>
691  : public __hash_base<size_t, string_view>
692  {
693  size_t
694  operator()(const string_view& __str) const noexcept
695  { return std::_Hash_impl::hash(__str.data(), __str.length()); }
696  };
697 
698  template<>
699  struct __is_fast_hash<hash<string_view>> : std::false_type
700  { };
701 
702 #ifdef _GLIBCXX_USE_WCHAR_T
703  template<>
704  struct hash<wstring_view>
705  : public __hash_base<size_t, wstring_view>
706  {
707  size_t
708  operator()(const wstring_view& __s) const noexcept
709  { return std::_Hash_impl::hash(__s.data(),
710  __s.length() * sizeof(wchar_t)); }
711  };
712 
713  template<>
714  struct __is_fast_hash<hash<wstring_view>> : std::false_type
715  { };
716 #endif
717 
718 #ifdef _GLIBCXX_USE_CHAR8_T
719  template<>
720  struct hash<u8string_view>
721  : public __hash_base<size_t, u8string_view>
722  {
723  size_t
724  operator()(const u8string_view& __str) const noexcept
725  { return std::_Hash_impl::hash(__str.data(), __str.length()); }
726  };
727 
728  template<>
729  struct __is_fast_hash<hash<u8string_view>> : std::false_type
730  { };
731 #endif
732 
733  template<>
734  struct hash<u16string_view>
735  : public __hash_base<size_t, u16string_view>
736  {
737  size_t
738  operator()(const u16string_view& __s) const noexcept
739  { return std::_Hash_impl::hash(__s.data(),
740  __s.length() * sizeof(char16_t)); }
741  };
742 
743  template<>
744  struct __is_fast_hash<hash<u16string_view>> : std::false_type
745  { };
746 
747  template<>
748  struct hash<u32string_view>
749  : public __hash_base<size_t, u32string_view>
750  {
751  size_t
752  operator()(const u32string_view& __s) const noexcept
753  { return std::_Hash_impl::hash(__s.data(),
754  __s.length() * sizeof(char32_t)); }
755  };
756 
757  template<>
758  struct __is_fast_hash<hash<u32string_view>> : std::false_type
759  { };
760 
761  inline namespace literals
762  {
763  inline namespace string_view_literals
764  {
765 #pragma GCC diagnostic push
766 #pragma GCC diagnostic ignored "-Wliteral-suffix"
767  inline constexpr basic_string_view<char>
768  operator""sv(const char* __str, size_t __len) noexcept
769  { return basic_string_view<char>{__str, __len}; }
770 
771 #ifdef _GLIBCXX_USE_WCHAR_T
772  inline constexpr basic_string_view<wchar_t>
773  operator""sv(const wchar_t* __str, size_t __len) noexcept
774  { return basic_string_view<wchar_t>{__str, __len}; }
775 #endif
776 
777 #ifdef _GLIBCXX_USE_CHAR8_T
778  inline constexpr basic_string_view<char8_t>
779  operator""sv(const char8_t* __str, size_t __len) noexcept
780  { return basic_string_view<char8_t>{__str, __len}; }
781 #endif
782 
783  inline constexpr basic_string_view<char16_t>
784  operator""sv(const char16_t* __str, size_t __len) noexcept
785  { return basic_string_view<char16_t>{__str, __len}; }
786 
787  inline constexpr basic_string_view<char32_t>
788  operator""sv(const char32_t* __str, size_t __len) noexcept
789  { return basic_string_view<char32_t>{__str, __len}; }
790 
791 #pragma GCC diagnostic pop
792  } // namespace string_literals
793  } // namespace literals
794 
795 #if __cpp_lib_concepts
796  namespace ranges
797  {
798  // Opt-in to borrowed_range concept
799  template<typename _CharT, typename _Traits>
800  inline constexpr bool
801  enable_borrowed_range<basic_string_view<_CharT, _Traits>> = true;
802 
803  // Opt-in to view concept
804  template<typename _CharT, typename _Traits>
805  inline constexpr bool
806  enable_view<basic_string_view<_CharT, _Traits>> = true;
807  }
808 #endif
809 _GLIBCXX_END_NAMESPACE_VERSION
810 } // namespace std
811 
812 #include <bits/string_view.tcc>
813 
814 #endif // __cplusplus <= 201402L
815 
816 #endif // _GLIBCXX_EXPERIMENTAL_STRING_VIEW