libstdc++-v3/include/std/string_view

   1 // Components for manipulating non-owning sequences of characters -*- C++ -*-
   2
   3 // Copyright (C) 2013-2020 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 /** @file 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/int_limits.h>
  44 #include <bits/range_access.h>
  45 #include <bits/ostream_insert.h>
  46
  47 namespace std _GLIBCXX_VISIBILITY(default)
  48 {
  49 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  50
  51 #define __cpp_lib_string_view 201803
  52
  53   // Helper for basic_string and basic_string_view members.
  54   constexpr size_t
  55   __sv_check(size_t __size, size_t __pos, const char* __s)
  56   {
  57     if (__pos > __size)
  58       __throw_out_of_range_fmt(__N("%s: __pos (which is %zu) > __size "
  59                                    "(which is %zu)"), __s, __pos, __size);
  60     return __pos;
  61   }
  62
  63   // Helper for basic_string members.
  64   // NB: __sv_limit doesn't check for a bad __pos value.
  65   constexpr size_t
  66   __sv_limit(size_t __size, size_t __pos, size_t __off) noexcept
  67   {
  68    const bool __testoff =  __off < __size - __pos;
  69    return __testoff ? __off : __size - __pos;
  70   }
  71
  72   /**
  73    *  @class basic_string_view <string_view>
  74    *  @brief  A non-owning reference to a string.
  75    *
  76    *  @ingroup strings
  77    *  @ingroup sequences
  78    *
  79    *  @tparam _CharT  Type of character
  80    *  @tparam _Traits  Traits for character type, defaults to
  81    *                   char_traits<_CharT>.
  82    *
  83    *  A basic_string_view looks like this:
  84    *
  85    *  @code
  86    *    _CharT*    _M_str
  87    *    size_t     _M_len
  88    *  @endcode
  89    */
  90   template<typename _CharT, typename _Traits = std::char_traits<_CharT>>
  91     class basic_string_view
  92     {
  93       static_assert(!is_array_v<_CharT>);
  94       static_assert(is_trivial_v<_CharT> && is_standard_layout_v<_CharT>);
  95       static_assert(is_same_v<_CharT, typename _Traits::char_type>);
  96
  97     public:
  98
  99       // types
 100       using traits_type         = _Traits;
 101       using value_type          = _CharT;
 102       using pointer             = value_type*;
 103       using const_pointer       = const value_type*;
 104       using reference           = value_type&;
 105       using const_reference     = const value_type&;
 106       using const_iterator      = const value_type*;
 107       using iterator            = const_iterator;
 108       using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 109       using reverse_iterator    = const_reverse_iterator;
 110       using size_type           = size_t;
 111       using difference_type     = ptrdiff_t;
 112       static constexpr size_type npos = size_type(-1);
 113
 114       // [string.view.cons], construction and assignment
 115
 116       constexpr
 117       basic_string_view() noexcept
 118       : _M_len{0}, _M_str{nullptr}
 119       { }
 120
 121       constexpr basic_string_view(const basic_string_view&) noexcept = default;
 122
 123       __attribute__((__nonnull__)) constexpr
 124       basic_string_view(const _CharT* __str) noexcept
 125       : _M_len{traits_type::length(__str)},
 126         _M_str{__str}
 127       { }
 128
 129       constexpr
 130       basic_string_view(const _CharT* __str, size_type __len) noexcept
 131       : _M_len{__len}, _M_str{__str}
 132       { }
 133
 134 #if __cplusplus > 201703L && __cpp_lib_concepts
 135       template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
 136         requires same_as<iter_value_t<_It>, _CharT>
 137           && (!convertible_to<_End, size_type>)
 138         constexpr
 139         basic_string_view(_It __first, _End __last)
 140         : _M_len(__last - __first), _M_str(std::to_address(__first))
 141         { }
 142 #endif
 143
 144       constexpr basic_string_view&
 145       operator=(const basic_string_view&) noexcept = default;
 146
 147       // [string.view.iterators], iterator support
 148
 149       constexpr const_iterator
 150       begin() const noexcept
 151       { return this->_M_str; }
 152
 153       constexpr const_iterator
 154       end() const noexcept
 155       { return this->_M_str + this->_M_len; }
 156
 157       constexpr const_iterator
 158       cbegin() const noexcept
 159       { return this->_M_str; }
 160
 161       constexpr const_iterator
 162       cend() const noexcept
 163       { return this->_M_str + this->_M_len; }
 164
 165       constexpr const_reverse_iterator
 166       rbegin() const noexcept
 167       { return const_reverse_iterator(this->end()); }
 168
 169       constexpr const_reverse_iterator
 170       rend() const noexcept
 171       { return const_reverse_iterator(this->begin()); }
 172
 173       constexpr const_reverse_iterator
 174       crbegin() const noexcept
 175       { return const_reverse_iterator(this->end()); }
 176
 177       constexpr const_reverse_iterator
 178       crend() const noexcept
 179       { return const_reverse_iterator(this->begin()); }
 180
 181       // [string.view.capacity], capacity
 182
 183       constexpr size_type
 184       size() const noexcept
 185       { return this->_M_len; }
 186
 187       constexpr size_type
 188       length() const noexcept
 189       { return _M_len; }
 190
 191       constexpr size_type
 192       max_size() const noexcept
 193       {
 194         return (npos - sizeof(size_type) - sizeof(void*))
 195                 / sizeof(value_type) / 4;
 196       }
 197
 198       [[nodiscard]] constexpr bool
 199       empty() const noexcept
 200       { return this->_M_len == 0; }
 201
 202       // [string.view.access], element access
 203
 204       constexpr const_reference
 205       operator[](size_type __pos) const noexcept
 206       {
 207         // TODO: Assert to restore in a way compatible with the constexpr.
 208         // __glibcxx_assert(__pos < this->_M_len);
 209         return *(this->_M_str + __pos);
 210       }
 211
 212       constexpr const_reference
 213       at(size_type __pos) const
 214       {
 215         if (__pos >= _M_len)
 216           __throw_out_of_range_fmt(__N("basic_string_view::at: __pos "
 217                                        "(which is %zu) >= this->size() "
 218                                        "(which is %zu)"), __pos, this->size());
 219         return *(this->_M_str + __pos);
 220       }
 221
 222       constexpr const_reference
 223       front() const noexcept
 224       {
 225         // TODO: Assert to restore in a way compatible with the constexpr.
 226         // __glibcxx_assert(this->_M_len > 0);
 227         return *this->_M_str;
 228       }
 229
 230       constexpr const_reference
 231       back() const noexcept
 232       {
 233         // TODO: Assert to restore in a way compatible with the constexpr.
 234         // __glibcxx_assert(this->_M_len > 0);
 235         return *(this->_M_str + this->_M_len - 1);
 236       }
 237
 238       constexpr const_pointer
 239       data() const noexcept
 240       { return this->_M_str; }
 241
 242       // [string.view.modifiers], modifiers:
 243
 244       constexpr void
 245       remove_prefix(size_type __n) noexcept
 246       {
 247         __glibcxx_assert(this->_M_len >= __n);
 248         this->_M_str += __n;
 249         this->_M_len -= __n;
 250       }
 251
 252       constexpr void
 253       remove_suffix(size_type __n) noexcept
 254       { this->_M_len -= __n; }
 255
 256       constexpr void
 257       swap(basic_string_view& __sv) noexcept
 258       {
 259         auto __tmp = *this;
 260         *this = __sv;
 261         __sv = __tmp;
 262       }
 263
 264       // [string.view.ops], string operations:
 265
 266       size_type
 267       copy(_CharT* __str, size_type __n, size_type __pos = 0) const
 268       {
 269         __glibcxx_requires_string_len(__str, __n);
 270         __pos = std::__sv_check(size(), __pos, "basic_string_view::copy");
 271         const size_type __rlen = std::min(__n, _M_len - __pos);
 272         // _GLIBCXX_RESOLVE_LIB_DEFECTS
 273         // 2777. basic_string_view::copy should use char_traits::copy
 274         traits_type::copy(__str, data() + __pos, __rlen);
 275         return __rlen;
 276       }
 277
 278       constexpr basic_string_view
 279       substr(size_type __pos = 0, size_type __n = npos) const noexcept(false)
 280       {
 281         __pos = std::__sv_check(size(), __pos, "basic_string_view::substr");
 282         const size_type __rlen = std::min(__n, _M_len - __pos);
 283         return basic_string_view{_M_str + __pos, __rlen};
 284       }
 285
 286       constexpr int
 287       compare(basic_string_view __str) const noexcept
 288       {
 289         const size_type __rlen = std::min(this->_M_len, __str._M_len);
 290         int __ret = traits_type::compare(this->_M_str, __str._M_str, __rlen);
 291         if (__ret == 0)
 292           __ret = _S_compare(this->_M_len, __str._M_len);
 293         return __ret;
 294       }
 295
 296       constexpr int
 297       compare(size_type __pos1, size_type __n1, basic_string_view __str) const
 298       { return this->substr(__pos1, __n1).compare(__str); }
 299
 300       constexpr int
 301       compare(size_type __pos1, size_type __n1,
 302               basic_string_view __str, size_type __pos2, size_type __n2) const
 303       {
 304         return this->substr(__pos1, __n1).compare(__str.substr(__pos2, __n2));
 305       }
 306
 307       __attribute__((__nonnull__)) constexpr int
 308       compare(const _CharT* __str) const noexcept
 309       { return this->compare(basic_string_view{__str}); }
 310
 311       __attribute__((__nonnull__)) 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 noexcept(false)
 318       {
 319         return this->substr(__pos1, __n1)
 320                    .compare(basic_string_view(__str, __n2));
 321       }
 322
 323 #if __cplusplus > 201703L
 324       constexpr bool
 325       starts_with(basic_string_view __x) const noexcept
 326       { return this->substr(0, __x.size()) == __x; }
 327
 328       constexpr bool
 329       starts_with(_CharT __x) const noexcept
 330       { return !this->empty() && traits_type::eq(this->front(), __x); }
 331
 332       constexpr bool
 333       starts_with(const _CharT* __x) const noexcept
 334       { return this->starts_with(basic_string_view(__x)); }
 335
 336       constexpr bool
 337       ends_with(basic_string_view __x) const noexcept
 338       {
 339         return this->size() >= __x.size()
 340             && this->compare(this->size() - __x.size(), npos, __x) == 0;
 341       }
 342
 343       constexpr bool
 344       ends_with(_CharT __x) const noexcept
 345       { return !this->empty() && traits_type::eq(this->back(), __x); }
 346
 347       constexpr bool
 348       ends_with(const _CharT* __x) const noexcept
 349       { return this->ends_with(basic_string_view(__x)); }
 350 #endif // C++20
 351
 352       // [string.view.find], searching
 353
 354       constexpr size_type
 355       find(basic_string_view __str, size_type __pos = 0) const noexcept
 356       { return this->find(__str._M_str, __pos, __str._M_len); }
 357
 358       constexpr size_type
 359       find(_CharT __c, size_type __pos = 0) const noexcept;
 360
 361       constexpr size_type
 362       find(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
 363
 364       __attribute__((__nonnull__)) constexpr size_type
 365       find(const _CharT* __str, size_type __pos = 0) const noexcept
 366       { return this->find(__str, __pos, traits_type::length(__str)); }
 367
 368       constexpr size_type
 369       rfind(basic_string_view __str, size_type __pos = npos) const noexcept
 370       { return this->rfind(__str._M_str, __pos, __str._M_len); }
 371
 372       constexpr size_type
 373       rfind(_CharT __c, size_type __pos = npos) const noexcept;
 374
 375       constexpr size_type
 376       rfind(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
 377
 378       __attribute__((__nonnull__)) constexpr size_type
 379       rfind(const _CharT* __str, size_type __pos = npos) const noexcept
 380       { return this->rfind(__str, __pos, traits_type::length(__str)); }
 381
 382       constexpr size_type
 383       find_first_of(basic_string_view __str, size_type __pos = 0) const noexcept
 384       { return this->find_first_of(__str._M_str, __pos, __str._M_len); }
 385
 386       constexpr size_type
 387       find_first_of(_CharT __c, size_type __pos = 0) const noexcept
 388       { return this->find(__c, __pos); }
 389
 390       constexpr size_type
 391       find_first_of(const _CharT* __str, size_type __pos,
 392                     size_type __n) const noexcept;
 393
 394       __attribute__((__nonnull__)) constexpr size_type
 395       find_first_of(const _CharT* __str, size_type __pos = 0) const noexcept
 396       { return this->find_first_of(__str, __pos, traits_type::length(__str)); }
 397
 398       constexpr size_type
 399       find_last_of(basic_string_view __str,
 400                    size_type __pos = npos) const noexcept
 401       { return this->find_last_of(__str._M_str, __pos, __str._M_len); }
 402
 403       constexpr size_type
 404       find_last_of(_CharT __c, size_type __pos=npos) const noexcept
 405       { return this->rfind(__c, __pos); }
 406
 407       constexpr size_type
 408       find_last_of(const _CharT* __str, size_type __pos,
 409                    size_type __n) const noexcept;
 410
 411       __attribute__((__nonnull__)) constexpr size_type
 412       find_last_of(const _CharT* __str, size_type __pos = npos) const noexcept
 413       { return this->find_last_of(__str, __pos, traits_type::length(__str)); }
 414
 415       constexpr size_type
 416       find_first_not_of(basic_string_view __str,
 417                         size_type __pos = 0) const noexcept
 418       { return this->find_first_not_of(__str._M_str, __pos, __str._M_len); }
 419
 420       constexpr size_type
 421       find_first_not_of(_CharT __c, size_type __pos = 0) const noexcept;
 422
 423       constexpr size_type
 424       find_first_not_of(const _CharT* __str,
 425                         size_type __pos, size_type __n) const noexcept;
 426
 427       __attribute__((__nonnull__)) constexpr size_type
 428       find_first_not_of(const _CharT* __str, size_type __pos = 0) const noexcept
 429       {
 430         return this->find_first_not_of(__str, __pos,
 431                                        traits_type::length(__str));
 432       }
 433
 434       constexpr size_type
 435       find_last_not_of(basic_string_view __str,
 436                        size_type __pos = npos) const noexcept
 437       { return this->find_last_not_of(__str._M_str, __pos, __str._M_len); }
 438
 439       constexpr size_type
 440       find_last_not_of(_CharT __c, size_type __pos = npos) const noexcept;
 441
 442       constexpr size_type
 443       find_last_not_of(const _CharT* __str,
 444                        size_type __pos, size_type __n) const noexcept;
 445
 446       __attribute__((__nonnull__)) constexpr size_type
 447       find_last_not_of(const _CharT* __str,
 448                        size_type __pos = npos) const noexcept
 449       {
 450         return this->find_last_not_of(__str, __pos,
 451                                       traits_type::length(__str));
 452       }
 453
 454     private:
 455
 456       static constexpr int
 457       _S_compare(size_type __n1, size_type __n2) noexcept
 458       {
 459         const difference_type __diff = __n1 - __n2;
 460         if (__diff > __detail::__int_limits<int>::max())
 461           return __detail::__int_limits<int>::max();
 462         if (__diff < __detail::__int_limits<int>::min())
 463           return __detail::__int_limits<int>::min();
 464         return static_cast<int>(__diff);
 465       }
 466
 467       size_t        _M_len;
 468       const _CharT* _M_str;
 469     };
 470
 471 #if __cplusplus > 201703L && __cpp_lib_concepts && __cpp_deduction_guides
 472   template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
 473     basic_string_view(_It, _End) -> basic_string_view<iter_value_t<_It>>;
 474 #endif
 475
 476   // [string.view.comparison], non-member basic_string_view comparison function
 477
 478   // Several of these functions use type_identity_t to create a non-deduced
 479   // context, so that only one argument participates in template argument
 480   // deduction and the other argument gets implicitly converted to the deduced
 481   // type (see N3766).
 482
 483   template<typename _CharT, typename _Traits>
 484     constexpr bool
 485     operator==(basic_string_view<_CharT, _Traits> __x,
 486                basic_string_view<_CharT, _Traits> __y) noexcept
 487     { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 488
 489   template<typename _CharT, typename _Traits>
 490     constexpr bool
 491     operator==(basic_string_view<_CharT, _Traits> __x,
 492                __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
 493     noexcept
 494     { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 495
 496   template<typename _CharT, typename _Traits>
 497     constexpr bool
 498     operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
 499                basic_string_view<_CharT, _Traits> __y) noexcept
 500     { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 501
 502   template<typename _CharT, typename _Traits>
 503     constexpr bool
 504     operator!=(basic_string_view<_CharT, _Traits> __x,
 505                basic_string_view<_CharT, _Traits> __y) noexcept
 506     { return !(__x == __y); }
 507
 508   template<typename _CharT, typename _Traits>
 509     constexpr bool
 510     operator!=(basic_string_view<_CharT, _Traits> __x,
 511                __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
 512     noexcept
 513     { return !(__x == __y); }
 514
 515   template<typename _CharT, typename _Traits>
 516     constexpr bool
 517     operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
 518                basic_string_view<_CharT, _Traits> __y) noexcept
 519     { return !(__x == __y); }
 520
 521   template<typename _CharT, typename _Traits>
 522     constexpr bool
 523     operator< (basic_string_view<_CharT, _Traits> __x,
 524                basic_string_view<_CharT, _Traits> __y) noexcept
 525     { return __x.compare(__y) < 0; }
 526
 527   template<typename _CharT, typename _Traits>
 528     constexpr bool
 529     operator< (basic_string_view<_CharT, _Traits> __x,
 530                __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
 531     noexcept
 532     { return __x.compare(__y) < 0; }
 533
 534   template<typename _CharT, typename _Traits>
 535     constexpr bool
 536     operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
 537                basic_string_view<_CharT, _Traits> __y) noexcept
 538     { return __x.compare(__y) < 0; }
 539
 540   template<typename _CharT, typename _Traits>
 541     constexpr bool
 542     operator> (basic_string_view<_CharT, _Traits> __x,
 543                basic_string_view<_CharT, _Traits> __y) noexcept
 544     { return __x.compare(__y) > 0; }
 545
 546   template<typename _CharT, typename _Traits>
 547     constexpr bool
 548     operator> (basic_string_view<_CharT, _Traits> __x,
 549                __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
 550     noexcept
 551     { return __x.compare(__y) > 0; }
 552
 553   template<typename _CharT, typename _Traits>
 554     constexpr bool
 555     operator> (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
 556                basic_string_view<_CharT, _Traits> __y) noexcept
 557     { return __x.compare(__y) > 0; }
 558
 559   template<typename _CharT, typename _Traits>
 560     constexpr bool
 561     operator<=(basic_string_view<_CharT, _Traits> __x,
 562                basic_string_view<_CharT, _Traits> __y) noexcept
 563     { return __x.compare(__y) <= 0; }
 564
 565   template<typename _CharT, typename _Traits>
 566     constexpr bool
 567     operator<=(basic_string_view<_CharT, _Traits> __x,
 568                __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
 569     noexcept
 570     { return __x.compare(__y) <= 0; }
 571
 572   template<typename _CharT, typename _Traits>
 573     constexpr bool
 574     operator<=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
 575                basic_string_view<_CharT, _Traits> __y) noexcept
 576     { return __x.compare(__y) <= 0; }
 577
 578   template<typename _CharT, typename _Traits>
 579     constexpr bool
 580     operator>=(basic_string_view<_CharT, _Traits> __x,
 581                basic_string_view<_CharT, _Traits> __y) noexcept
 582     { return __x.compare(__y) >= 0; }
 583
 584   template<typename _CharT, typename _Traits>
 585     constexpr bool
 586     operator>=(basic_string_view<_CharT, _Traits> __x,
 587                __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
 588     noexcept
 589     { return __x.compare(__y) >= 0; }
 590
 591   template<typename _CharT, typename _Traits>
 592     constexpr bool
 593     operator>=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
 594                basic_string_view<_CharT, _Traits> __y) noexcept
 595     { return __x.compare(__y) >= 0; }
 596
 597   // [string.view.io], Inserters and extractors
 598   template<typename _CharT, typename _Traits>
 599     inline basic_ostream<_CharT, _Traits>&
 600     operator<<(basic_ostream<_CharT, _Traits>& __os,
 601                basic_string_view<_CharT,_Traits> __str)
 602     { return __ostream_insert(__os, __str.data(), __str.size()); }
 603
 604
 605   // basic_string_view typedef names
 606
 607   using string_view = basic_string_view<char>;
 608 #ifdef _GLIBCXX_USE_WCHAR_T
 609   using wstring_view = basic_string_view<wchar_t>;
 610 #endif
 611 #ifdef _GLIBCXX_USE_CHAR8_T
 612   using u8string_view = basic_string_view<char8_t>;
 613 #endif
 614   using u16string_view = basic_string_view<char16_t>;
 615   using u32string_view = basic_string_view<char32_t>;
 616
 617   // [string.view.hash], hash support:
 618
 619   template<typename _Tp>
 620     struct hash;
 621
 622   template<>
 623     struct hash<string_view>
 624     : public __hash_base<size_t, string_view>
 625     {
 626       size_t
 627       operator()(const string_view& __str) const noexcept
 628       { return std::_Hash_impl::hash(__str.data(), __str.length()); }
 629     };
 630
 631   template<>
 632     struct __is_fast_hash<hash<string_view>> : std::false_type
 633     { };
 634
 635 #ifdef _GLIBCXX_USE_WCHAR_T
 636   template<>
 637     struct hash<wstring_view>
 638     : public __hash_base<size_t, wstring_view>
 639     {
 640       size_t
 641       operator()(const wstring_view& __s) const noexcept
 642       { return std::_Hash_impl::hash(__s.data(),
 643                                      __s.length() * sizeof(wchar_t)); }
 644     };
 645
 646   template<>
 647     struct __is_fast_hash<hash<wstring_view>> : std::false_type
 648     { };
 649 #endif
 650
 651 #ifdef _GLIBCXX_USE_CHAR8_T
 652   template<>
 653     struct hash<u8string_view>
 654     : public __hash_base<size_t, u8string_view>
 655     {
 656       size_t
 657       operator()(const u8string_view& __str) const noexcept
 658       { return std::_Hash_impl::hash(__str.data(), __str.length()); }
 659     };
 660
 661   template<>
 662     struct __is_fast_hash<hash<u8string_view>> : std::false_type
 663     { };
 664 #endif
 665
 666   template<>
 667     struct hash<u16string_view>
 668     : public __hash_base<size_t, u16string_view>
 669     {
 670       size_t
 671       operator()(const u16string_view& __s) const noexcept
 672       { return std::_Hash_impl::hash(__s.data(),
 673                                      __s.length() * sizeof(char16_t)); }
 674     };
 675
 676   template<>
 677     struct __is_fast_hash<hash<u16string_view>> : std::false_type
 678     { };
 679
 680   template<>
 681     struct hash<u32string_view>
 682     : public __hash_base<size_t, u32string_view>
 683     {
 684       size_t
 685       operator()(const u32string_view& __s) const noexcept
 686       { return std::_Hash_impl::hash(__s.data(),
 687                                      __s.length() * sizeof(char32_t)); }
 688     };
 689
 690   template<>
 691     struct __is_fast_hash<hash<u32string_view>> : std::false_type
 692     { };
 693
 694   inline namespace literals
 695   {
 696   inline namespace string_view_literals
 697   {
 698 #pragma GCC diagnostic push
 699 #pragma GCC diagnostic ignored "-Wliteral-suffix"
 700     inline constexpr basic_string_view<char>
 701     operator""sv(const char* __str, size_t __len) noexcept
 702     { return basic_string_view<char>{__str, __len}; }
 703
 704 #ifdef _GLIBCXX_USE_WCHAR_T
 705     inline constexpr basic_string_view<wchar_t>
 706     operator""sv(const wchar_t* __str, size_t __len) noexcept
 707     { return basic_string_view<wchar_t>{__str, __len}; }
 708 #endif
 709
 710 #ifdef _GLIBCXX_USE_CHAR8_T
 711     inline constexpr basic_string_view<char8_t>
 712     operator""sv(const char8_t* __str, size_t __len) noexcept
 713     { return basic_string_view<char8_t>{__str, __len}; }
 714 #endif
 715
 716     inline constexpr basic_string_view<char16_t>
 717     operator""sv(const char16_t* __str, size_t __len) noexcept
 718     { return basic_string_view<char16_t>{__str, __len}; }
 719
 720     inline constexpr basic_string_view<char32_t>
 721     operator""sv(const char32_t* __str, size_t __len) noexcept
 722     { return basic_string_view<char32_t>{__str, __len}; }
 723
 724 #pragma GCC diagnostic pop
 725   } // namespace string_literals
 726   } // namespace literals
 727
 728 #if __cpp_lib_concepts
 729   namespace ranges
 730   {
 731     // Opt-in to borrowed_range concept
 732     template<typename _CharT, typename _Traits>
 733       inline constexpr bool
 734         enable_borrowed_range<basic_string_view<_CharT, _Traits>> = true;
 735
 736     // Opt-in to view concept
 737     template<typename _CharT, typename _Traits>
 738       inline constexpr bool
 739         enable_view<basic_string_view<_CharT, _Traits>> = true;
 740   }
 741 #endif
 742 _GLIBCXX_END_NAMESPACE_VERSION
 743 } // namespace std
 744
 745 #include <bits/string_view.tcc>
 746
 747 #endif // __cplusplus <= 201402L
 748
 749 #endif // _GLIBCXX_EXPERIMENTAL_STRING_VIEW