libstdc++
experimental/string_view
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1 // Components for manipulating non-owning sequences of characters -*- C++ -*-
2 
3 // Copyright (C) 2013-2024 Free Software Foundation, Inc.
4 //
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15 
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24 
25 /** @file experimental/string_view
26  * This is a TS C++ Library header.
27  * @ingroup libfund-ts
28  */
29 
30 //
31 // N3762 basic_string_view library
32 //
33 
34 #ifndef _GLIBCXX_EXPERIMENTAL_STRING_VIEW
35 #define _GLIBCXX_EXPERIMENTAL_STRING_VIEW 1
36 
37 #pragma GCC system_header
38 
39 #include <bits/requires_hosted.h> // experimental is currently omitted
40 
41 #if __cplusplus >= 201402L
42 
43 #include <string>
44 #include <limits>
45 #include <bits/ranges_base.h> // enable_borrowed_range, enable_view
46 #include <experimental/bits/lfts_config.h>
47 
48 namespace std _GLIBCXX_VISIBILITY(default)
49 {
50 _GLIBCXX_BEGIN_NAMESPACE_VERSION
51 
52 namespace experimental
53 {
54 inline namespace fundamentals_v1
55 {
56 #define __cpp_lib_experimental_string_view 201411
57 
58  /**
59  * @class basic_string_view <experimental/string_view>
60  * @brief A non-owning reference to a string.
61  *
62  * @ingroup strings
63  * @ingroup sequences
64  * @ingroup libfund-ts
65  *
66  * @tparam _CharT Type of character
67  * @tparam _Traits Traits for character type, defaults to
68  * char_traits<_CharT>.
69  *
70  * A basic_string_view looks like this:
71  *
72  * @code
73  * _CharT* _M_str
74  * size_t _M_len
75  * @endcode
76  */
77  template<typename _CharT, typename _Traits = std::char_traits<_CharT>>
78  class basic_string_view
79  {
80  public:
81 
82  // types
83  using traits_type = _Traits;
84  using value_type = _CharT;
85  using pointer = _CharT*;
86  using const_pointer = const _CharT*;
87  using reference = _CharT&;
88  using const_reference = const _CharT&;
89  using const_iterator = const _CharT*;
90  using iterator = const_iterator;
91  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
92  using reverse_iterator = const_reverse_iterator;
93  using size_type = size_t;
94  using difference_type = ptrdiff_t;
95  static constexpr size_type npos = size_type(-1);
96 
97  // [string.view.cons], construct/copy
98 
99  constexpr
100  basic_string_view() noexcept
101  : _M_len{0}, _M_str{nullptr}
102  { }
103 
104  constexpr basic_string_view(const basic_string_view&) noexcept = default;
105 
106  template<typename _Allocator>
107  basic_string_view(const basic_string<_CharT, _Traits,
108  _Allocator>& __str) noexcept
109  : _M_len{__str.length()}, _M_str{__str.data()}
110  { }
111 
112  constexpr basic_string_view(const _CharT* __str)
113  : _M_len{__str == nullptr ? 0 : traits_type::length(__str)},
114  _M_str{__str}
115  { }
116 
117  constexpr basic_string_view(const _CharT* __str, size_type __len)
118  : _M_len{__len},
119  _M_str{__str}
120  { }
121 
122  basic_string_view&
123  operator=(const basic_string_view&) noexcept = default;
124 
125  // [string.view.iterators], iterators
126 
127  constexpr const_iterator
128  begin() const noexcept
129  { return this->_M_str; }
130 
131  constexpr const_iterator
132  end() const noexcept
133  { return this->_M_str + this->_M_len; }
134 
135  constexpr const_iterator
136  cbegin() const noexcept
137  { return this->_M_str; }
138 
139  constexpr const_iterator
140  cend() const noexcept
141  { return this->_M_str + this->_M_len; }
142 
143  const_reverse_iterator
144  rbegin() const noexcept
145  { return const_reverse_iterator(this->end()); }
146 
147  const_reverse_iterator
148  rend() const noexcept
149  { return const_reverse_iterator(this->begin()); }
150 
151  const_reverse_iterator
152  crbegin() const noexcept
153  { return const_reverse_iterator(this->end()); }
154 
155  const_reverse_iterator
156  crend() const noexcept
157  { return const_reverse_iterator(this->begin()); }
158 
159  // [string.view.capacity], capacity
160 
161  constexpr size_type
162  size() const noexcept
163  { return this->_M_len; }
164 
165  constexpr size_type
166  length() const noexcept
167  { return _M_len; }
168 
169  constexpr size_type
170  max_size() const noexcept
171  {
172  return (npos - sizeof(size_type) - sizeof(void*))
173  / sizeof(value_type) / 4;
174  }
175 
176  _GLIBCXX_NODISCARD constexpr bool
177  empty() const noexcept
178  { return this->_M_len == 0; }
179 
180  // [string.view.access], element access
181 
182  constexpr const _CharT&
183  operator[](size_type __pos) const
184  {
185  __glibcxx_assert(__pos < this->_M_len);
186  return *(this->_M_str + __pos);
187  }
188 
189  constexpr const _CharT&
190  at(size_type __pos) const
191  {
192  return __pos < this->_M_len
193  ? *(this->_M_str + __pos)
194  : (__throw_out_of_range_fmt(__N("basic_string_view::at: __pos "
195  "(which is %zu) >= this->size() "
196  "(which is %zu)"),
197  __pos, this->size()),
198  *this->_M_str);
199  }
200 
201  constexpr const _CharT&
202  front() const
203  {
204  __glibcxx_assert(this->_M_len > 0);
205  return *this->_M_str;
206  }
207 
208  constexpr const _CharT&
209  back() const
210  {
211  __glibcxx_assert(this->_M_len > 0);
212  return *(this->_M_str + this->_M_len - 1);
213  }
214 
215  constexpr const _CharT*
216  data() const noexcept
217  { return this->_M_str; }
218 
219  // [string.view.modifiers], modifiers:
220 
221  constexpr void
222  remove_prefix(size_type __n)
223  {
224  __glibcxx_assert(this->_M_len >= __n);
225  this->_M_str += __n;
226  this->_M_len -= __n;
227  }
228 
229  constexpr void
230  remove_suffix(size_type __n)
231  { this->_M_len -= __n; }
232 
233  constexpr void
234  swap(basic_string_view& __sv) noexcept
235  {
236  auto __tmp = *this;
237  *this = __sv;
238  __sv = __tmp;
239  }
240 
241 
242  // [string.view.ops], string operations:
243 
244  template<typename _Allocator>
245  explicit operator basic_string<_CharT, _Traits, _Allocator>() const
246  {
247  return { this->_M_str, this->_M_len };
248  }
249 
250  template<typename _Allocator = std::allocator<_CharT>>
251  basic_string<_CharT, _Traits, _Allocator>
252  to_string(const _Allocator& __alloc = _Allocator()) const
253  {
254  return { this->_M_str, this->_M_len, __alloc };
255  }
256 
257  size_type
258  copy(_CharT* __str, size_type __n, size_type __pos = 0) const
259  {
260  __glibcxx_requires_string_len(__str, __n);
261  if (__pos > this->_M_len)
262  __throw_out_of_range_fmt(__N("basic_string_view::copy: __pos "
263  "(which is %zu) > this->size() "
264  "(which is %zu)"),
265  __pos, this->size());
266  size_type __rlen{std::min(__n, size_type{this->_M_len - __pos})};
267  for (auto __begin = this->_M_str + __pos,
268  __end = __begin + __rlen; __begin != __end;)
269  *__str++ = *__begin++;
270  return __rlen;
271  }
272 
273 
274  // [string.view.ops], string operations:
275 
276  constexpr basic_string_view
277  substr(size_type __pos = 0, size_type __n = npos) const
278  {
279  return __pos <= this->_M_len
280  ? basic_string_view{this->_M_str + __pos,
281  std::min(__n, size_type{this->_M_len - __pos})}
282  : (__throw_out_of_range_fmt(__N("basic_string_view::substr: __pos "
283  "(which is %zu) > this->size() "
284  "(which is %zu)"),
285  __pos, this->size()), basic_string_view{});
286  }
287 
288  constexpr int
289  compare(basic_string_view __str) const noexcept
290  {
291  int __ret = traits_type::compare(this->_M_str, __str._M_str,
292  std::min(this->_M_len, __str._M_len));
293  if (__ret == 0)
294  __ret = _S_compare(this->_M_len, __str._M_len);
295  return __ret;
296  }
297 
298  constexpr int
299  compare(size_type __pos1, size_type __n1, basic_string_view __str) const
300  { return this->substr(__pos1, __n1).compare(__str); }
301 
302  constexpr int
303  compare(size_type __pos1, size_type __n1,
304  basic_string_view __str, size_type __pos2, size_type __n2) const
305  { return this->substr(__pos1, __n1).compare(__str.substr(__pos2, __n2)); }
306 
307  constexpr int
308  compare(const _CharT* __str) const noexcept
309  { return this->compare(basic_string_view{__str}); }
310 
311  constexpr int
312  compare(size_type __pos1, size_type __n1, const _CharT* __str) const
313  { return this->substr(__pos1, __n1).compare(basic_string_view{__str}); }
314 
315  constexpr int
316  compare(size_type __pos1, size_type __n1,
317  const _CharT* __str, size_type __n2) const
318  {
319  return this->substr(__pos1, __n1)
320  .compare(basic_string_view(__str, __n2));
321  }
322 
323  constexpr size_type
324  find(basic_string_view __str, size_type __pos = 0) const noexcept
325  { return this->find(__str._M_str, __pos, __str._M_len); }
326 
327  constexpr size_type
328  find(_CharT __c, size_type __pos=0) const noexcept;
329 
330  constexpr size_type
331  find(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
332 
333  constexpr size_type
334  find(const _CharT* __str, size_type __pos=0) const noexcept
335  { return this->find(__str, __pos, traits_type::length(__str)); }
336 
337  constexpr size_type
338  rfind(basic_string_view __str, size_type __pos = npos) const noexcept
339  { return this->rfind(__str._M_str, __pos, __str._M_len); }
340 
341  constexpr size_type
342  rfind(_CharT __c, size_type __pos = npos) const noexcept;
343 
344  constexpr size_type
345  rfind(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
346 
347  constexpr size_type
348  rfind(const _CharT* __str, size_type __pos = npos) const noexcept
349  { return this->rfind(__str, __pos, traits_type::length(__str)); }
350 
351  constexpr size_type
352  find_first_of(basic_string_view __str, size_type __pos = 0) const noexcept
353  { return this->find_first_of(__str._M_str, __pos, __str._M_len); }
354 
355  constexpr size_type
356  find_first_of(_CharT __c, size_type __pos = 0) const noexcept
357  { return this->find(__c, __pos); }
358 
359  constexpr size_type
360  find_first_of(const _CharT* __str, size_type __pos, size_type __n) const;
361 
362  constexpr size_type
363  find_first_of(const _CharT* __str, size_type __pos = 0) const noexcept
364  { return this->find_first_of(__str, __pos, traits_type::length(__str)); }
365 
366  constexpr size_type
367  find_last_of(basic_string_view __str,
368  size_type __pos = npos) const noexcept
369  { return this->find_last_of(__str._M_str, __pos, __str._M_len); }
370 
371  constexpr size_type
372  find_last_of(_CharT __c, size_type __pos=npos) const noexcept
373  { return this->rfind(__c, __pos); }
374 
375  constexpr size_type
376  find_last_of(const _CharT* __str, size_type __pos, size_type __n) const;
377 
378  constexpr size_type
379  find_last_of(const _CharT* __str, size_type __pos = npos) const noexcept
380  { return this->find_last_of(__str, __pos, traits_type::length(__str)); }
381 
382  constexpr size_type
383  find_first_not_of(basic_string_view __str,
384  size_type __pos = 0) const noexcept
385  { return this->find_first_not_of(__str._M_str, __pos, __str._M_len); }
386 
387  constexpr size_type
388  find_first_not_of(_CharT __c, size_type __pos = 0) const noexcept;
389 
390  constexpr size_type
391  find_first_not_of(const _CharT* __str,
392  size_type __pos, size_type __n) const;
393 
394  constexpr size_type
395  find_first_not_of(const _CharT* __str, size_type __pos = 0) const noexcept
396  {
397  return this->find_first_not_of(__str, __pos,
398  traits_type::length(__str));
399  }
400 
401  constexpr size_type
402  find_last_not_of(basic_string_view __str,
403  size_type __pos = npos) const noexcept
404  { return this->find_last_not_of(__str._M_str, __pos, __str._M_len); }
405 
406  constexpr size_type
407  find_last_not_of(_CharT __c, size_type __pos = npos) const noexcept;
408 
409  constexpr size_type
410  find_last_not_of(const _CharT* __str,
411  size_type __pos, size_type __n) const;
412 
413  constexpr size_type
414  find_last_not_of(const _CharT* __str,
415  size_type __pos = npos) const noexcept
416  {
417  return this->find_last_not_of(__str, __pos,
418  traits_type::length(__str));
419  }
420 
421  private:
422 
423  static constexpr int
424  _S_compare(size_type __n1, size_type __n2) noexcept
425  {
426  return difference_type(__n1 - __n2) > std::numeric_limits<int>::max()
427  ? std::numeric_limits<int>::max()
428  : difference_type(__n1 - __n2) < std::numeric_limits<int>::min()
429  ? std::numeric_limits<int>::min()
430  : static_cast<int>(difference_type(__n1 - __n2));
431  }
432 
433  size_t _M_len;
434  const _CharT* _M_str;
435  };
436 
437  // [string.view.comparison], non-member basic_string_view comparison functions
438 
439  // Several of these functions use type_identity_t to create a non-deduced
440  // context, so that only one argument participates in template argument
441  // deduction and the other argument gets implicitly converted to the deduced
442  // type (see N3766).
443 
444  template<typename _CharT, typename _Traits>
445  constexpr bool
446  operator==(basic_string_view<_CharT, _Traits> __x,
447  basic_string_view<_CharT, _Traits> __y) noexcept
448  { return __x.size() == __y.size() && __x.compare(__y) == 0; }
449 
450  template<typename _CharT, typename _Traits>
451  constexpr bool
452  operator==(basic_string_view<_CharT, _Traits> __x,
453  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
454  noexcept
455  { return __x.size() == __y.size() && __x.compare(__y) == 0; }
456 
457  template<typename _CharT, typename _Traits>
458  constexpr bool
459  operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
460  basic_string_view<_CharT, _Traits> __y) noexcept
461  { return __x.size() == __y.size() && __x.compare(__y) == 0; }
462 
463  template<typename _CharT, typename _Traits>
464  constexpr bool
465  operator!=(basic_string_view<_CharT, _Traits> __x,
466  basic_string_view<_CharT, _Traits> __y) noexcept
467  { return !(__x == __y); }
468 
469  template<typename _CharT, typename _Traits>
470  constexpr bool
471  operator!=(basic_string_view<_CharT, _Traits> __x,
472  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
473  noexcept
474  { return !(__x == __y); }
475 
476  template<typename _CharT, typename _Traits>
477  constexpr bool
478  operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
479  basic_string_view<_CharT, _Traits> __y) noexcept
480  { return !(__x == __y); }
481 
482  template<typename _CharT, typename _Traits>
483  constexpr bool
484  operator< (basic_string_view<_CharT, _Traits> __x,
485  basic_string_view<_CharT, _Traits> __y) noexcept
486  { return __x.compare(__y) < 0; }
487 
488  template<typename _CharT, typename _Traits>
489  constexpr bool
490  operator< (basic_string_view<_CharT, _Traits> __x,
491  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
492  noexcept
493  { return __x.compare(__y) < 0; }
494 
495  template<typename _CharT, typename _Traits>
496  constexpr bool
497  operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
498  basic_string_view<_CharT, _Traits> __y) noexcept
499  { return __x.compare(__y) < 0; }
500 
501  template<typename _CharT, typename _Traits>
502  constexpr bool
503  operator> (basic_string_view<_CharT, _Traits> __x,
504  basic_string_view<_CharT, _Traits> __y) noexcept
505  { return __x.compare(__y) > 0; }
506 
507  template<typename _CharT, typename _Traits>
508  constexpr bool
509  operator> (basic_string_view<_CharT, _Traits> __x,
510  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
511  noexcept
512  { return __x.compare(__y) > 0; }
513 
514  template<typename _CharT, typename _Traits>
515  constexpr bool
516  operator> (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
517  basic_string_view<_CharT, _Traits> __y) noexcept
518  { return __x.compare(__y) > 0; }
519 
520  template<typename _CharT, typename _Traits>
521  constexpr bool
522  operator<=(basic_string_view<_CharT, _Traits> __x,
523  basic_string_view<_CharT, _Traits> __y) noexcept
524  { return __x.compare(__y) <= 0; }
525 
526  template<typename _CharT, typename _Traits>
527  constexpr bool
528  operator<=(basic_string_view<_CharT, _Traits> __x,
529  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
530  noexcept
531  { return __x.compare(__y) <= 0; }
532 
533  template<typename _CharT, typename _Traits>
534  constexpr bool
535  operator<=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
536  basic_string_view<_CharT, _Traits> __y) noexcept
537  { return __x.compare(__y) <= 0; }
538 
539  template<typename _CharT, typename _Traits>
540  constexpr bool
541  operator>=(basic_string_view<_CharT, _Traits> __x,
542  basic_string_view<_CharT, _Traits> __y) noexcept
543  { return __x.compare(__y) >= 0; }
544 
545  template<typename _CharT, typename _Traits>
546  constexpr bool
547  operator>=(basic_string_view<_CharT, _Traits> __x,
548  __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
549  noexcept
550  { return __x.compare(__y) >= 0; }
551 
552  template<typename _CharT, typename _Traits>
553  constexpr bool
554  operator>=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
555  basic_string_view<_CharT, _Traits> __y) noexcept
556  { return __x.compare(__y) >= 0; }
557 
558  // [string.view.io], Inserters and extractors
559  template<typename _CharT, typename _Traits>
560  inline basic_ostream<_CharT, _Traits>&
561  operator<<(basic_ostream<_CharT, _Traits>& __os,
562  basic_string_view<_CharT,_Traits> __str)
563  { return __ostream_insert(__os, __str.data(), __str.size()); }
564 
565 
566  // basic_string_view typedef names
567 
568  using string_view = basic_string_view<char>;
569  using wstring_view = basic_string_view<wchar_t>;
570 #ifdef _GLIBCXX_USE_CHAR8_T
571  using u8string_view = basic_string_view<char8_t>;
572 #endif
573  using u16string_view = basic_string_view<char16_t>;
574  using u32string_view = basic_string_view<char32_t>;
575 } // namespace fundamentals_v1
576 } // namespace experimental
577 
578 
579  // [string.view.hash], hash support:
580  template<typename _Tp>
581  struct hash;
582 
583  template<>
584  struct hash<experimental::string_view>
585  : public __hash_base<size_t, experimental::string_view>
586  {
587  size_t
588  operator()(const experimental::string_view& __str) const noexcept
589  { return std::_Hash_impl::hash(__str.data(), __str.length()); }
590  };
591 
592  template<>
593  struct __is_fast_hash<hash<experimental::string_view>> : std::false_type
594  { };
595 
596  template<>
597  struct hash<experimental::wstring_view>
598  : public __hash_base<size_t, wstring>
599  {
600  size_t
601  operator()(const experimental::wstring_view& __s) const noexcept
602  { return std::_Hash_impl::hash(__s.data(),
603  __s.length() * sizeof(wchar_t)); }
604  };
605 
606  template<>
607  struct __is_fast_hash<hash<experimental::wstring_view>> : std::false_type
608  { };
609 
610 #ifdef _GLIBCXX_USE_CHAR8_T
611  template<>
612  struct hash<experimental::u8string_view>
613  : public __hash_base<size_t, experimental::u8string_view>
614  {
615  size_t
616  operator()(const experimental::u8string_view& __s) const noexcept
617  { return std::_Hash_impl::hash(__s.data(), __s.length()); }
618  };
619 
620  template<>
621  struct __is_fast_hash<hash<experimental::u8string_view>> : std::false_type
622  { };
623 #endif
624 
625  template<>
626  struct hash<experimental::u16string_view>
627  : public __hash_base<size_t, experimental::u16string_view>
628  {
629  size_t
630  operator()(const experimental::u16string_view& __s) const noexcept
631  { return std::_Hash_impl::hash(__s.data(),
632  __s.length() * sizeof(char16_t)); }
633  };
634 
635  template<>
636  struct __is_fast_hash<hash<experimental::u16string_view>> : std::false_type
637  { };
638 
639  template<>
640  struct hash<experimental::u32string_view>
641  : public __hash_base<size_t, experimental::u32string_view>
642  {
643  size_t
644  operator()(const experimental::u32string_view& __s) const noexcept
645  { return std::_Hash_impl::hash(__s.data(),
646  __s.length() * sizeof(char32_t)); }
647  };
648 
649  template<>
650  struct __is_fast_hash<hash<experimental::u32string_view>> : std::false_type
651  { };
652 
653 namespace experimental
654 {
655  // I added these EMSR.
656  inline namespace literals
657  {
658  inline namespace string_view_literals
659  {
660 #pragma GCC diagnostic push
661 #pragma GCC diagnostic ignored "-Wliteral-suffix"
662  inline constexpr basic_string_view<char>
663  operator""sv(const char* __str, size_t __len) noexcept
664  { return basic_string_view<char>{__str, __len}; }
665 
666  inline constexpr basic_string_view<wchar_t>
667  operator""sv(const wchar_t* __str, size_t __len) noexcept
668  { return basic_string_view<wchar_t>{__str, __len}; }
669 
670 #ifdef _GLIBCXX_USE_CHAR8_T
671  inline constexpr basic_string_view<char8_t>
672  operator""sv(const char8_t* __str, size_t __len) noexcept
673  { return basic_string_view<char8_t>{__str, __len}; }
674 #endif
675 
676  inline constexpr basic_string_view<char16_t>
677  operator""sv(const char16_t* __str, size_t __len) noexcept
678  { return basic_string_view<char16_t>{__str, __len}; }
679 
680  inline constexpr basic_string_view<char32_t>
681  operator""sv(const char32_t* __str, size_t __len) noexcept
682  { return basic_string_view<char32_t>{__str, __len}; }
683 #pragma GCC diagnostic pop
684  } // namespace string_literals
685  } // namespace literals
686 } // namespace experimental
687 
688 #if __cpp_lib_concepts
689  namespace ranges
690  {
691  // Opt-in to borrowed_range concept
692  template<typename _CharT, typename _Traits>
693  inline constexpr bool
694  enable_borrowed_range<experimental::basic_string_view<_CharT, _Traits>>
695  = true;
696 
697  // Opt-in to view concept
698  template<typename _CharT, typename _Traits>
699  inline constexpr bool
700  enable_view<experimental::basic_string_view<_CharT, _Traits>> = true;
701  }
702 #endif
703 
704 _GLIBCXX_END_NAMESPACE_VERSION
705 } // namespace std
706 
707 #include <experimental/bits/string_view.tcc>
708 
709 #endif // __cplusplus <= 201103L
710 
711 #endif // _GLIBCXX_EXPERIMENTAL_STRING_VIEW