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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7 // terms of the GNU General Public License as published by the
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9 // any later version.
10 
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15 
16 // Under Section 7 of GPL version 3, you are granted additional
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18 // 3.1, as published by the Free Software Foundation.
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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  : _M_len(__last - __first), _M_str(std::to_address(__first))
148  { }
149 
150 #if __cplusplus > 202002L
151  template<typename _Range, typename _DRange = remove_cvref_t<_Range>>
152  requires (!is_same_v<_DRange, basic_string_view>)
153  && ranges::contiguous_range<_Range>
154  && ranges::sized_range<_Range>
155  && is_same_v<ranges::range_value_t<_Range>, _CharT>
156  && (!is_convertible_v<_Range, const _CharT*>)
157  && (!requires (_DRange& __d) {
158  __d.operator ::std::basic_string_view<_CharT, _Traits>();
159  })
160  && (!requires { typename _DRange::traits_type; }
161  || is_same_v<typename _DRange::traits_type, _Traits>)
162  constexpr
163  basic_string_view(_Range&& __r)
164  noexcept(noexcept(ranges::size(__r)) && noexcept(ranges::data(__r)))
165  : _M_len(ranges::size(__r)), _M_str(ranges::data(__r))
166  { }
167 #endif // C++23
168 #endif // C++20
169 
170  constexpr basic_string_view&
171  operator=(const basic_string_view&) noexcept = default;
172 
173  // [string.view.iterators], iterator support
174 
175  constexpr const_iterator
176  begin() const noexcept
177  { return this->_M_str; }
178 
179  constexpr const_iterator
180  end() const noexcept
181  { return this->_M_str + this->_M_len; }
182 
183  constexpr const_iterator
184  cbegin() const noexcept
185  { return this->_M_str; }
186 
187  constexpr const_iterator
188  cend() const noexcept
189  { return this->_M_str + this->_M_len; }
190 
191  constexpr const_reverse_iterator
192  rbegin() const noexcept
193  { return const_reverse_iterator(this->end()); }
194 
195  constexpr const_reverse_iterator
196  rend() const noexcept
197  { return const_reverse_iterator(this->begin()); }
198 
199  constexpr const_reverse_iterator
200  crbegin() const noexcept
201  { return const_reverse_iterator(this->end()); }
202 
203  constexpr const_reverse_iterator
204  crend() const noexcept
205  { return const_reverse_iterator(this->begin()); }
206 
207  // [string.view.capacity], capacity
208 
209  constexpr size_type
210  size() const noexcept
211  { return this->_M_len; }
212 
213  constexpr size_type
214  length() const noexcept
215  { return _M_len; }
216 
217  constexpr size_type
218  max_size() const noexcept
219  {
220  return (npos - sizeof(size_type) - sizeof(void*))
221  / sizeof(value_type) / 4;
222  }
223 
224  [[nodiscard]] constexpr bool
225  empty() const noexcept
226  { return this->_M_len == 0; }
227 
228  // [string.view.access], element access
229 
230  constexpr const_reference
231  operator[](size_type __pos) const noexcept
232  {
233  __glibcxx_assert(__pos < this->_M_len);
234  return *(this->_M_str + __pos);
235  }
236 
237  constexpr const_reference
238  at(size_type __pos) const
239  {
240  if (__pos >= _M_len)
241  __throw_out_of_range_fmt(__N("basic_string_view::at: __pos "
242  "(which is %zu) >= this->size() "
243  "(which is %zu)"), __pos, this->size());
244  return *(this->_M_str + __pos);
245  }
246 
247  constexpr const_reference
248  front() const noexcept
249  {
250  __glibcxx_assert(this->_M_len > 0);
251  return *this->_M_str;
252  }
253 
254  constexpr const_reference
255  back() const noexcept
256  {
257  __glibcxx_assert(this->_M_len > 0);
258  return *(this->_M_str + this->_M_len - 1);
259  }
260 
261  constexpr const_pointer
262  data() const noexcept
263  { return this->_M_str; }
264 
265  // [string.view.modifiers], modifiers:
266 
267  constexpr void
268  remove_prefix(size_type __n) noexcept
269  {
270  __glibcxx_assert(this->_M_len >= __n);
271  this->_M_str += __n;
272  this->_M_len -= __n;
273  }
274 
275  constexpr void
276  remove_suffix(size_type __n) noexcept
277  { this->_M_len -= __n; }
278 
279  constexpr void
280  swap(basic_string_view& __sv) noexcept
281  {
282  auto __tmp = *this;
283  *this = __sv;
284  __sv = __tmp;
285  }
286 
287  // [string.view.ops], string operations:
288 
289  _GLIBCXX20_CONSTEXPR
290  size_type
291  copy(_CharT* __str, size_type __n, size_type __pos = 0) const
292  {
293  __glibcxx_requires_string_len(__str, __n);
294  __pos = std::__sv_check(size(), __pos, "basic_string_view::copy");
295  const size_type __rlen = std::min(__n, _M_len - __pos);
296  // _GLIBCXX_RESOLVE_LIB_DEFECTS
297  // 2777. basic_string_view::copy should use char_traits::copy
298  traits_type::copy(__str, data() + __pos, __rlen);
299  return __rlen;
300  }
301 
302  constexpr basic_string_view
303  substr(size_type __pos = 0, size_type __n = npos) const noexcept(false)
304  {
305  __pos = std::__sv_check(size(), __pos, "basic_string_view::substr");
306  const size_type __rlen = std::min(__n, _M_len - __pos);
307  return basic_string_view{_M_str + __pos, __rlen};
308  }
309 
310  constexpr int
311  compare(basic_string_view __str) const noexcept
312  {
313  const size_type __rlen = std::min(this->_M_len, __str._M_len);
314  int __ret = traits_type::compare(this->_M_str, __str._M_str, __rlen);
315  if (__ret == 0)
316  __ret = _S_compare(this->_M_len, __str._M_len);
317  return __ret;
318  }
319 
320  constexpr int
321  compare(size_type __pos1, size_type __n1, basic_string_view __str) const
322  { return this->substr(__pos1, __n1).compare(__str); }
323 
324  constexpr int
325  compare(size_type __pos1, size_type __n1,
326  basic_string_view __str, size_type __pos2, size_type __n2) const
327  {
328  return this->substr(__pos1, __n1).compare(__str.substr(__pos2, __n2));
329  }
330 
331  __attribute__((__nonnull__)) constexpr int
332  compare(const _CharT* __str) const noexcept
333  { return this->compare(basic_string_view{__str}); }
334 
335  __attribute__((__nonnull__)) constexpr int
336  compare(size_type __pos1, size_type __n1, const _CharT* __str) const
337  { return this->substr(__pos1, __n1).compare(basic_string_view{__str}); }
338 
339  constexpr int
340  compare(size_type __pos1, size_type __n1,
341  const _CharT* __str, size_type __n2) const noexcept(false)
342  {
343  return this->substr(__pos1, __n1)
344  .compare(basic_string_view(__str, __n2));
345  }
346 
347 #if __cplusplus > 201703L
348 #define __cpp_lib_starts_ends_with 201711L
349  constexpr bool
350  starts_with(basic_string_view __x) const noexcept
351  { return this->substr(0, __x.size()) == __x; }
352 
353  constexpr bool
354  starts_with(_CharT __x) const noexcept
355  { return !this->empty() && traits_type::eq(this->front(), __x); }
356 
357  constexpr bool
358  starts_with(const _CharT* __x) const noexcept
359  { return this->starts_with(basic_string_view(__x)); }
360 
361  constexpr bool
362  ends_with(basic_string_view __x) const noexcept
363  {
364  const auto __len = this->size();
365  const auto __xlen = __x.size();
366  return __len >= __xlen
367  && traits_type::compare(end() - __xlen, __x.data(), __xlen) == 0;
368  }
369 
370  constexpr bool
371  ends_with(_CharT __x) const noexcept
372  { return !this->empty() && traits_type::eq(this->back(), __x); }
373 
374  constexpr bool
375  ends_with(const _CharT* __x) const noexcept
376  { return this->ends_with(basic_string_view(__x)); }
377 #endif // C++20
378 
379 #if __cplusplus > 202002L
380 #define __cpp_lib_string_contains 202011L
381  constexpr bool
382  contains(basic_string_view __x) const noexcept
383  { return this->find(__x) != npos; }
384 
385  constexpr bool
386  contains(_CharT __x) const noexcept
387  { return this->find(__x) != npos; }
388 
389  constexpr bool
390  contains(const _CharT* __x) const noexcept
391  { return this->find(__x) != npos; }
392 #endif // C++23
393 
394  // [string.view.find], searching
395 
396  constexpr size_type
397  find(basic_string_view __str, size_type __pos = 0) const noexcept
398  { return this->find(__str._M_str, __pos, __str._M_len); }
399 
400  constexpr size_type
401  find(_CharT __c, size_type __pos = 0) const noexcept;
402 
403  constexpr size_type
404  find(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
405 
406  __attribute__((__nonnull__)) constexpr size_type
407  find(const _CharT* __str, size_type __pos = 0) const noexcept
408  { return this->find(__str, __pos, traits_type::length(__str)); }
409 
410  constexpr size_type
411  rfind(basic_string_view __str, size_type __pos = npos) const noexcept
412  { return this->rfind(__str._M_str, __pos, __str._M_len); }
413 
414  constexpr size_type
415  rfind(_CharT __c, size_type __pos = npos) const noexcept;
416 
417  constexpr size_type
418  rfind(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
419 
420  __attribute__((__nonnull__)) constexpr size_type
421  rfind(const _CharT* __str, size_type __pos = npos) const noexcept
422  { return this->rfind(__str, __pos, traits_type::length(__str)); }
423 
424  constexpr size_type
425  find_first_of(basic_string_view __str, size_type __pos = 0) const noexcept
426  { return this->find_first_of(__str._M_str, __pos, __str._M_len); }
427 
428  constexpr size_type
429  find_first_of(_CharT __c, size_type __pos = 0) const noexcept
430  { return this->find(__c, __pos); }
431 
432  constexpr size_type
433  find_first_of(const _CharT* __str, size_type __pos,
434  size_type __n) const noexcept;
435 
436  __attribute__((__nonnull__)) constexpr size_type
437  find_first_of(const _CharT* __str, size_type __pos = 0) const noexcept
438  { return this->find_first_of(__str, __pos, traits_type::length(__str)); }
439 
440  constexpr size_type
441  find_last_of(basic_string_view __str,
442  size_type __pos = npos) const noexcept
443  { return this->find_last_of(__str._M_str, __pos, __str._M_len); }
444 
445  constexpr size_type
446  find_last_of(_CharT __c, size_type __pos=npos) const noexcept
447  { return this->rfind(__c, __pos); }
448 
449  constexpr size_type
450  find_last_of(const _CharT* __str, size_type __pos,
451  size_type __n) const noexcept;
452 
453  __attribute__((__nonnull__)) constexpr size_type
454  find_last_of(const _CharT* __str, size_type __pos = npos) const noexcept
455  { return this->find_last_of(__str, __pos, traits_type::length(__str)); }
456 
457  constexpr size_type
458  find_first_not_of(basic_string_view __str,
459  size_type __pos = 0) const noexcept
460  { return this->find_first_not_of(__str._M_str, __pos, __str._M_len); }
461 
462  constexpr size_type
463  find_first_not_of(_CharT __c, size_type __pos = 0) const noexcept;
464 
465  constexpr size_type
466  find_first_not_of(const _CharT* __str,
467  size_type __pos, size_type __n) const noexcept;
468 
469  __attribute__((__nonnull__)) constexpr size_type
470  find_first_not_of(const _CharT* __str, size_type __pos = 0) const noexcept
471  {
472  return this->find_first_not_of(__str, __pos,
473  traits_type::length(__str));
474  }
475 
476  constexpr size_type
477  find_last_not_of(basic_string_view __str,
478  size_type __pos = npos) const noexcept
479  { return this->find_last_not_of(__str._M_str, __pos, __str._M_len); }
480 
481  constexpr size_type
482  find_last_not_of(_CharT __c, size_type __pos = npos) const noexcept;
483 
484  constexpr size_type
485  find_last_not_of(const _CharT* __str,
486  size_type __pos, size_type __n) const noexcept;
487 
488  __attribute__((__nonnull__)) constexpr size_type
489  find_last_not_of(const _CharT* __str,
490  size_type __pos = npos) const noexcept
491  {
492  return this->find_last_not_of(__str, __pos,
493  traits_type::length(__str));
494  }
495 
496  private:
497 
498  static constexpr int
499  _S_compare(size_type __n1, size_type __n2) noexcept
500  {
501  using __limits = __gnu_cxx::__int_traits<int>;
502  const difference_type __diff = __n1 - __n2;
503  if (__diff > __limits::__max)
504  return __limits::__max;
505  if (__diff < __limits::__min)
506  return __limits::__min;
507  return static_cast<int>(__diff);
508  }
509 
510  size_t _M_len;
511  const _CharT* _M_str;
512  };
513 
514 #if __cplusplus > 201703L && __cpp_lib_concepts && __cpp_deduction_guides
515  template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
516  basic_string_view(_It, _End) -> basic_string_view<iter_value_t<_It>>;
517 
518 #if __cplusplus > 202002L
519  template<ranges::contiguous_range _Range>
520  basic_string_view(_Range&&)
521  -> basic_string_view<ranges::range_value_t<_Range>>;
522 #endif
523 #endif
524 
525  // [string.view.comparison], non-member basic_string_view comparison function
526 
527  // Several of these functions use type_identity_t to create a non-deduced
528  // context, so that only one argument participates in template argument
529  // deduction and the other argument gets implicitly converted to the deduced
530  // type (see N3766).
531 
532  template<typename _CharT, typename _Traits>
533  constexpr bool
534  operator==(basic_string_view<_CharT, _Traits> __x,
535  basic_string_view<_CharT, _Traits> __y) noexcept
536  { return __x.size() == __y.size() && __x.compare(__y) == 0; }
537 
538  template<typename _CharT, typename _Traits>
539  constexpr bool
540  operator==(basic_string_view<_CharT, _Traits> __x,
541  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
542  noexcept
543  { return __x.size() == __y.size() && __x.compare(__y) == 0; }
544 
545 #if __cpp_lib_three_way_comparison
546  template<typename _CharT, typename _Traits>
547  constexpr auto
548  operator<=>(basic_string_view<_CharT, _Traits> __x,
549  basic_string_view<_CharT, _Traits> __y) noexcept
550  -> decltype(__detail::__char_traits_cmp_cat<_Traits>(0))
551  { return __detail::__char_traits_cmp_cat<_Traits>(__x.compare(__y)); }
552 
553  template<typename _CharT, typename _Traits>
554  constexpr auto
555  operator<=>(basic_string_view<_CharT, _Traits> __x,
556  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
557  noexcept
558  -> decltype(__detail::__char_traits_cmp_cat<_Traits>(0))
559  { return __detail::__char_traits_cmp_cat<_Traits>(__x.compare(__y)); }
560 #else
561  template<typename _CharT, typename _Traits>
562  constexpr bool
563  operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
564  basic_string_view<_CharT, _Traits> __y) noexcept
565  { return __x.size() == __y.size() && __x.compare(__y) == 0; }
566 
567  template<typename _CharT, typename _Traits>
568  constexpr bool
569  operator!=(basic_string_view<_CharT, _Traits> __x,
570  basic_string_view<_CharT, _Traits> __y) noexcept
571  { return !(__x == __y); }
572 
573  template<typename _CharT, typename _Traits>
574  constexpr bool
575  operator!=(basic_string_view<_CharT, _Traits> __x,
576  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
577  noexcept
578  { return !(__x == __y); }
579 
580  template<typename _CharT, typename _Traits>
581  constexpr bool
582  operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
583  basic_string_view<_CharT, _Traits> __y) noexcept
584  { return !(__x == __y); }
585 
586  template<typename _CharT, typename _Traits>
587  constexpr bool
588  operator< (basic_string_view<_CharT, _Traits> __x,
589  basic_string_view<_CharT, _Traits> __y) noexcept
590  { return __x.compare(__y) < 0; }
591 
592  template<typename _CharT, typename _Traits>
593  constexpr bool
594  operator< (basic_string_view<_CharT, _Traits> __x,
595  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
596  noexcept
597  { return __x.compare(__y) < 0; }
598 
599  template<typename _CharT, typename _Traits>
600  constexpr bool
601  operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
602  basic_string_view<_CharT, _Traits> __y) noexcept
603  { return __x.compare(__y) < 0; }
604 
605  template<typename _CharT, typename _Traits>
606  constexpr bool
607  operator> (basic_string_view<_CharT, _Traits> __x,
608  basic_string_view<_CharT, _Traits> __y) noexcept
609  { return __x.compare(__y) > 0; }
610 
611  template<typename _CharT, typename _Traits>
612  constexpr bool
613  operator> (basic_string_view<_CharT, _Traits> __x,
614  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
615  noexcept
616  { return __x.compare(__y) > 0; }
617 
618  template<typename _CharT, typename _Traits>
619  constexpr bool
620  operator> (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
621  basic_string_view<_CharT, _Traits> __y) noexcept
622  { return __x.compare(__y) > 0; }
623 
624  template<typename _CharT, typename _Traits>
625  constexpr bool
626  operator<=(basic_string_view<_CharT, _Traits> __x,
627  basic_string_view<_CharT, _Traits> __y) noexcept
628  { return __x.compare(__y) <= 0; }
629 
630  template<typename _CharT, typename _Traits>
631  constexpr bool
632  operator<=(basic_string_view<_CharT, _Traits> __x,
633  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
634  noexcept
635  { return __x.compare(__y) <= 0; }
636 
637  template<typename _CharT, typename _Traits>
638  constexpr bool
639  operator<=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
640  basic_string_view<_CharT, _Traits> __y) noexcept
641  { return __x.compare(__y) <= 0; }
642 
643  template<typename _CharT, typename _Traits>
644  constexpr bool
645  operator>=(basic_string_view<_CharT, _Traits> __x,
646  basic_string_view<_CharT, _Traits> __y) noexcept
647  { return __x.compare(__y) >= 0; }
648 
649  template<typename _CharT, typename _Traits>
650  constexpr bool
651  operator>=(basic_string_view<_CharT, _Traits> __x,
652  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
653  noexcept
654  { return __x.compare(__y) >= 0; }
655 
656  template<typename _CharT, typename _Traits>
657  constexpr bool
658  operator>=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
659  basic_string_view<_CharT, _Traits> __y) noexcept
660  { return __x.compare(__y) >= 0; }
661 #endif // three-way comparison
662 
663  // [string.view.io], Inserters and extractors
664  template<typename _CharT, typename _Traits>
665  inline basic_ostream<_CharT, _Traits>&
666  operator<<(basic_ostream<_CharT, _Traits>& __os,
667  basic_string_view<_CharT,_Traits> __str)
668  { return __ostream_insert(__os, __str.data(), __str.size()); }
669 
670 
671  // basic_string_view typedef names
672 
673  using string_view = basic_string_view<char>;
674 #ifdef _GLIBCXX_USE_WCHAR_T
675  using wstring_view = basic_string_view<wchar_t>;
676 #endif
677 #ifdef _GLIBCXX_USE_CHAR8_T
678  using u8string_view = basic_string_view<char8_t>;
679 #endif
680  using u16string_view = basic_string_view<char16_t>;
681  using u32string_view = basic_string_view<char32_t>;
682 
683  // [string.view.hash], hash support:
684 
685  template<typename _Tp>
686  struct hash;
687 
688  template<>
689  struct hash<string_view>
690  : public __hash_base<size_t, string_view>
691  {
692  size_t
693  operator()(const string_view& __str) const noexcept
694  { return std::_Hash_impl::hash(__str.data(), __str.length()); }
695  };
696 
697  template<>
698  struct __is_fast_hash<hash<string_view>> : std::false_type
699  { };
700 
701 #ifdef _GLIBCXX_USE_WCHAR_T
702  template<>
703  struct hash<wstring_view>
704  : public __hash_base<size_t, wstring_view>
705  {
706  size_t
707  operator()(const wstring_view& __s) const noexcept
708  { return std::_Hash_impl::hash(__s.data(),
709  __s.length() * sizeof(wchar_t)); }
710  };
711 
712  template<>
713  struct __is_fast_hash<hash<wstring_view>> : std::false_type
714  { };
715 #endif
716 
717 #ifdef _GLIBCXX_USE_CHAR8_T
718  template<>
719  struct hash<u8string_view>
720  : public __hash_base<size_t, u8string_view>
721  {
722  size_t
723  operator()(const u8string_view& __str) const noexcept
724  { return std::_Hash_impl::hash(__str.data(), __str.length()); }
725  };
726 
727  template<>
728  struct __is_fast_hash<hash<u8string_view>> : std::false_type
729  { };
730 #endif
731 
732  template<>
733  struct hash<u16string_view>
734  : public __hash_base<size_t, u16string_view>
735  {
736  size_t
737  operator()(const u16string_view& __s) const noexcept
738  { return std::_Hash_impl::hash(__s.data(),
739  __s.length() * sizeof(char16_t)); }
740  };
741 
742  template<>
743  struct __is_fast_hash<hash<u16string_view>> : std::false_type
744  { };
745 
746  template<>
747  struct hash<u32string_view>
748  : public __hash_base<size_t, u32string_view>
749  {
750  size_t
751  operator()(const u32string_view& __s) const noexcept
752  { return std::_Hash_impl::hash(__s.data(),
753  __s.length() * sizeof(char32_t)); }
754  };
755 
756  template<>
757  struct __is_fast_hash<hash<u32string_view>> : std::false_type
758  { };
759 
760  inline namespace literals
761  {
762  inline namespace string_view_literals
763  {
764 #pragma GCC diagnostic push
765 #pragma GCC diagnostic ignored "-Wliteral-suffix"
766  inline constexpr basic_string_view<char>
767  operator""sv(const char* __str, size_t __len) noexcept
768  { return basic_string_view<char>{__str, __len}; }
769 
770 #ifdef _GLIBCXX_USE_WCHAR_T
771  inline constexpr basic_string_view<wchar_t>
772  operator""sv(const wchar_t* __str, size_t __len) noexcept
773  { return basic_string_view<wchar_t>{__str, __len}; }
774 #endif
775 
776 #ifdef _GLIBCXX_USE_CHAR8_T
777  inline constexpr basic_string_view<char8_t>
778  operator""sv(const char8_t* __str, size_t __len) noexcept
779  { return basic_string_view<char8_t>{__str, __len}; }
780 #endif
781 
782  inline constexpr basic_string_view<char16_t>
783  operator""sv(const char16_t* __str, size_t __len) noexcept
784  { return basic_string_view<char16_t>{__str, __len}; }
785 
786  inline constexpr basic_string_view<char32_t>
787  operator""sv(const char32_t* __str, size_t __len) noexcept
788  { return basic_string_view<char32_t>{__str, __len}; }
789 
790 #pragma GCC diagnostic pop
791  } // namespace string_literals
792  } // namespace literals
793 
794 #if __cpp_lib_concepts
795  namespace ranges
796  {
797  // Opt-in to borrowed_range concept
798  template<typename _CharT, typename _Traits>
799  inline constexpr bool
800  enable_borrowed_range<basic_string_view<_CharT, _Traits>> = true;
801 
802  // Opt-in to view concept
803  template<typename _CharT, typename _Traits>
804  inline constexpr bool
805  enable_view<basic_string_view<_CharT, _Traits>> = true;
806  }
807 #endif
808 _GLIBCXX_END_NAMESPACE_VERSION
809 } // namespace std
810 
811 #include <bits/string_view.tcc>
812 
813 #endif // __cplusplus <= 201402L
814 
815 #endif // _GLIBCXX_EXPERIMENTAL_STRING_VIEW