string_view

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// Components for manipulating non-owning sequences of characters -*- C++ -*-
 
// Copyright (C) 2013-2025 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
 
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
 
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.
 
/** @file include/string_view
 *  This is a Standard C++ Library header.
 */
 
//
// N3762 basic_string_view library
//
 
#ifndef _GLIBCXX_STRING_VIEW
#define _GLIBCXX_STRING_VIEW 1
 
#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif
 
#define __glibcxx_want_constexpr_char_traits
#define __glibcxx_want_constexpr_string_view
#define __glibcxx_want_freestanding_string_view
#define __glibcxx_want_string_view
#define __glibcxx_want_starts_ends_with
#define __glibcxx_want_string_contains
#include <bits/version.h>
 
#if __cplusplus >= 201703L
 
#include <bits/char_traits.h>
#include <bits/functexcept.h>
#include <bits/functional_hash.h>
#include <bits/range_access.h>
#include <bits/stl_algobase.h>
#include <ext/numeric_traits.h>
 
#if __cplusplus >= 202002L
# include <bits/ranges_base.h>
#endif
 
#if _GLIBCXX_HOSTED
# include <iosfwd>
# include <bits/ostream_insert.h>
#endif
 
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
 
  // Helper for basic_string and basic_string_view members.
  constexpr size_t
  __sv_check(size_t __size, size_t __pos, const char* __s)
  {
    if (__pos > __size)
      __throw_out_of_range_fmt(__N("%s: __pos (which is %zu) > __size "
                                   "(which is %zu)"), __s, __pos, __size);
    return __pos;
  }
 
  // Helper for basic_string members.
  // NB: __sv_limit doesn't check for a bad __pos value.
  constexpr size_t
  __sv_limit(size_t __size, size_t __pos, size_t __off) noexcept
  {
   const bool __testoff =  __off < __size - __pos;
   return __testoff ? __off : __size - __pos;
  }
 
  /**
   *  @class basic_string_view <string_view>
   *  @brief  A non-owning reference to a string.
   *
   *  @ingroup strings
   *  @ingroup sequences
   *
   *  @tparam _CharT  Type of character
   *  @tparam _Traits  Traits for character type, defaults to
   *                   char_traits<_CharT>.
   *
   *  A basic_string_view looks like this:
   *
   *  @code
   *    _CharT*    _M_str
   *    size_t     _M_len
   *  @endcode
   */
  template<typename _CharT, typename _Traits = std::char_traits<_CharT>>
    class basic_string_view
    {
      static_assert(!is_array_v<_CharT>);
      static_assert(is_trivially_copyable_v<_CharT>
          && is_trivially_default_constructible_v<_CharT>
          && is_standard_layout_v<_CharT>);
      static_assert(is_same_v<_CharT, typename _Traits::char_type>);
 
    public:
 
      // types
      using traits_type         = _Traits;
      using value_type          = _CharT;
      using pointer             = value_type*;
      using const_pointer       = const value_type*;
      using reference           = value_type&;
      using const_reference     = const value_type&;
      using const_iterator      = const value_type*;
      using iterator            = const_iterator;
      using const_reverse_iterator = std::reverse_iterator<const_iterator>;
      using reverse_iterator    = const_reverse_iterator;
      using size_type           = size_t;
      using difference_type     = ptrdiff_t;
      static constexpr size_type npos = size_type(-1);
 
      // [string.view.cons], construction and assignment
 
      constexpr
      basic_string_view() noexcept
      : _M_len{0}, _M_str{nullptr}
      { }
 
      constexpr basic_string_view(const basic_string_view&) noexcept = default;
 
      [[__gnu__::__nonnull__]]
      constexpr
      basic_string_view(const _CharT* __str) noexcept
      : _M_len{traits_type::length(__str)},
        _M_str{__str}
      { }
 
      constexpr
      basic_string_view(const _CharT* __str, size_type __len) noexcept
      : _M_len{__len}, _M_str{__str}
      { }
 
#if __cplusplus >= 202002L && __cpp_lib_concepts
      template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
        requires same_as<iter_value_t<_It>, _CharT>
          && (!convertible_to<_End, size_type>)
        constexpr
        basic_string_view(_It __first, _End __last)
        noexcept(noexcept(__last - __first))
        : _M_len(__last - __first), _M_str(std::to_address(__first))
        { }
 
#if __cplusplus > 202002L
      template<typename _Range, typename _DRange = remove_cvref_t<_Range>>
        requires (!is_same_v<_DRange, basic_string_view>)
          && ranges::contiguous_range<_Range>
          && ranges::sized_range<_Range>
          && is_same_v<ranges::range_value_t<_Range>, _CharT>
          && (!is_convertible_v<_Range, const _CharT*>)
          && (!requires (_DRange& __d) {
                __d.operator ::std::basic_string_view<_CharT, _Traits>();
              })
        constexpr explicit
        basic_string_view(_Range&& __r)
        noexcept(noexcept(ranges::size(__r)) && noexcept(ranges::data(__r)))
        : _M_len(ranges::size(__r)), _M_str(ranges::data(__r))
        { }
 
      basic_string_view(nullptr_t) = delete;
#endif // C++23
#endif // C++20
 
      constexpr basic_string_view&
      operator=(const basic_string_view&) noexcept = default;
 
      // [string.view.iterators], iterator support
 
      [[nodiscard]]
      constexpr const_iterator
      begin() const noexcept
      { return this->_M_str; }
 
      [[nodiscard]]
      constexpr const_iterator
      end() const noexcept
      { return this->_M_str + this->_M_len; }
 
      [[nodiscard]]
      constexpr const_iterator
      cbegin() const noexcept
      { return this->_M_str; }
 
      [[nodiscard]]
      constexpr const_iterator
      cend() const noexcept
      { return this->_M_str + this->_M_len; }
 
      [[nodiscard]]
      constexpr const_reverse_iterator
      rbegin() const noexcept
      { return const_reverse_iterator(this->end()); }
 
      [[nodiscard]]
      constexpr const_reverse_iterator
      rend() const noexcept
      { return const_reverse_iterator(this->begin()); }
 
      [[nodiscard]]
      constexpr const_reverse_iterator
      crbegin() const noexcept
      { return const_reverse_iterator(this->end()); }
 
      [[nodiscard]]
      constexpr const_reverse_iterator
      crend() const noexcept
      { return const_reverse_iterator(this->begin()); }
 
      // [string.view.capacity], capacity
 
      [[nodiscard]]
      constexpr size_type
      size() const noexcept
      { return this->_M_len; }
 
      [[nodiscard]]
      constexpr size_type
      length() const noexcept
      { return _M_len; }
 
      [[nodiscard]]
      constexpr size_type
      max_size() const noexcept
      {
        return (npos - sizeof(size_type) - sizeof(void*))
                / sizeof(value_type) / 4;
      }
 
      [[nodiscard]]
      constexpr bool
      empty() const noexcept
      { return this->_M_len == 0; }
 
      // [string.view.access], element access
 
      [[nodiscard]]
      constexpr const_reference
      operator[](size_type __pos) const noexcept
      {
        __glibcxx_assert(__pos < this->_M_len);
        return *(this->_M_str + __pos);
      }
 
      [[nodiscard]]
      constexpr const_reference
      at(size_type __pos) const
      {
        if (__pos >= _M_len)
          __throw_out_of_range_fmt(__N("basic_string_view::at: __pos "
                                       "(which is %zu) >= this->size() "
                                       "(which is %zu)"), __pos, this->size());
        return *(this->_M_str + __pos);
      }
 
      [[nodiscard]]
      constexpr const_reference
      front() const noexcept
      {
        __glibcxx_assert(this->_M_len > 0);
        return *this->_M_str;
      }
 
      [[nodiscard]]
      constexpr const_reference
      back() const noexcept
      {
        __glibcxx_assert(this->_M_len > 0);
        return *(this->_M_str + this->_M_len - 1);
      }
 
      [[nodiscard]]
      constexpr const_pointer
      data() const noexcept
      { return this->_M_str; }
 
      // [string.view.modifiers], modifiers:
 
      constexpr void
      remove_prefix(size_type __n) noexcept
      {
        __glibcxx_assert(this->_M_len >= __n);
        this->_M_str += __n;
        this->_M_len -= __n;
      }
 
      constexpr void
      remove_suffix(size_type __n) noexcept
      {
        __glibcxx_assert(this->_M_len >= __n);
        this->_M_len -= __n;
      }
 
      constexpr void
      swap(basic_string_view& __sv) noexcept
      {
        auto __tmp = *this;
        *this = __sv;
        __sv = __tmp;
      }
 
      // [string.view.ops], string operations:
 
      _GLIBCXX20_CONSTEXPR
      size_type
      copy(_CharT* __str, size_type __n, size_type __pos = 0) const
      {
        __glibcxx_requires_string_len(__str, __n);
        __pos = std::__sv_check(size(), __pos, "basic_string_view::copy");
        const size_type __rlen = std::min<size_t>(__n, _M_len - __pos);
        // _GLIBCXX_RESOLVE_LIB_DEFECTS
        // 2777. basic_string_view::copy should use char_traits::copy
        traits_type::copy(__str, data() + __pos, __rlen);
        return __rlen;
      }
 
      [[nodiscard]]
      constexpr basic_string_view
      substr(size_type __pos = 0, size_type __n = npos) const noexcept(false)
      {
        __pos = std::__sv_check(size(), __pos, "basic_string_view::substr");
        const size_type __rlen = std::min<size_t>(__n, _M_len - __pos);
        return basic_string_view{_M_str + __pos, __rlen};
      }
 
      [[nodiscard]]
      constexpr int
      compare(basic_string_view __str) const noexcept
      {
        const size_type __rlen = std::min(this->_M_len, __str._M_len);
        int __ret = traits_type::compare(this->_M_str, __str._M_str, __rlen);
        if (__ret == 0)
          __ret = _S_compare(this->_M_len, __str._M_len);
        return __ret;
      }
 
      [[nodiscard]]
      constexpr int
      compare(size_type __pos1, size_type __n1, basic_string_view __str) const
      { return this->substr(__pos1, __n1).compare(__str); }
 
      [[nodiscard]]
      constexpr int
      compare(size_type __pos1, size_type __n1,
              basic_string_view __str, size_type __pos2, size_type __n2) const
      {
        return this->substr(__pos1, __n1).compare(__str.substr(__pos2, __n2));
      }
 
      [[nodiscard, __gnu__::__nonnull__]]
      constexpr int
      compare(const _CharT* __str) const noexcept
      { return this->compare(basic_string_view{__str}); }
 
      [[nodiscard, __gnu__::__nonnull__]]
      constexpr int
      compare(size_type __pos1, size_type __n1, const _CharT* __str) const
      { return this->substr(__pos1, __n1).compare(basic_string_view{__str}); }
 
      [[nodiscard]]
      constexpr int
      compare(size_type __pos1, size_type __n1,
              const _CharT* __str, size_type __n2) const noexcept(false)
      {
        return this->substr(__pos1, __n1)
                   .compare(basic_string_view(__str, __n2));
      }
 
#ifdef __cpp_lib_starts_ends_with // C++ >= 20
      [[nodiscard]]
      constexpr bool
      starts_with(basic_string_view __x) const noexcept
      {
        return _M_len >= __x._M_len
          && traits_type::compare(_M_str, __x._M_str, __x._M_len) == 0;
      }
 
      [[nodiscard]]
      constexpr bool
      starts_with(_CharT __x) const noexcept
      { return !this->empty() && traits_type::eq(this->front(), __x); }
 
      [[nodiscard, __gnu__::__nonnull__]]
      constexpr bool
      starts_with(const _CharT* __x) const noexcept
      { return this->starts_with(basic_string_view(__x)); }
 
      [[nodiscard]]
      constexpr bool
      ends_with(basic_string_view __x) const noexcept
      {
        const auto __len = this->size();
        const auto __xlen = __x.size();
        return __len >= __xlen
          && traits_type::compare(end() - __xlen, __x.data(), __xlen) == 0;
      }
 
      [[nodiscard]]
      constexpr bool
      ends_with(_CharT __x) const noexcept
      { return !this->empty() && traits_type::eq(this->back(), __x); }
 
      [[nodiscard, __gnu__::__nonnull__]]
      constexpr bool
      ends_with(const _CharT* __x) const noexcept
      { return this->ends_with(basic_string_view(__x)); }
#endif // __cpp_lib_starts_ends_with
 
#if __cplusplus > 202002L
#if _GLIBCXX_HOSTED && !defined(__cpp_lib_string_contains)
      // This FTM is not freestanding as it also implies matching <string>
      // support, and <string> is omitted from the freestanding subset.
# error "libstdc++ bug: string_contains not defined when it should be"
#endif // HOSTED
      [[nodiscard]]
      constexpr bool
      contains(basic_string_view __x) const noexcept
      { return this->find(__x) != npos; }
 
      [[nodiscard]]
      constexpr bool
      contains(_CharT __x) const noexcept
      { return this->find(__x) != npos; }
 
      [[nodiscard, __gnu__::__nonnull__]]
      constexpr bool
      contains(const _CharT* __x) const noexcept
      { return this->find(__x) != npos; }
#endif // C++23
 
      // [string.view.find], searching
 
      [[nodiscard]]
      constexpr size_type
      find(basic_string_view __str, size_type __pos = 0) const noexcept
      { return this->find(__str._M_str, __pos, __str._M_len); }
 
      [[nodiscard]]
      constexpr size_type
      find(_CharT __c, size_type __pos = 0) const noexcept;
 
      [[nodiscard]]
      constexpr size_type
      find(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
 
      [[nodiscard, __gnu__::__nonnull__]]
      constexpr size_type
      find(const _CharT* __str, size_type __pos = 0) const noexcept
      { return this->find(__str, __pos, traits_type::length(__str)); }
 
      [[nodiscard]]
      constexpr size_type
      rfind(basic_string_view __str, size_type __pos = npos) const noexcept
      { return this->rfind(__str._M_str, __pos, __str._M_len); }
 
      [[nodiscard]]
      constexpr size_type
      rfind(_CharT __c, size_type __pos = npos) const noexcept;
 
      [[nodiscard]]
      constexpr size_type
      rfind(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
 
      [[nodiscard, __gnu__::__nonnull__]]
      constexpr size_type
      rfind(const _CharT* __str, size_type __pos = npos) const noexcept
      { return this->rfind(__str, __pos, traits_type::length(__str)); }
 
      [[nodiscard]]
      constexpr size_type
      find_first_of(basic_string_view __str, size_type __pos = 0) const noexcept
      { return this->find_first_of(__str._M_str, __pos, __str._M_len); }
 
      [[nodiscard]]
      constexpr size_type
      find_first_of(_CharT __c, size_type __pos = 0) const noexcept
      { return this->find(__c, __pos); }
 
      [[nodiscard]]
      constexpr size_type
      find_first_of(const _CharT* __str, size_type __pos,
                    size_type __n) const noexcept;
 
      [[nodiscard, __gnu__::__nonnull__]]
      constexpr size_type
      find_first_of(const _CharT* __str, size_type __pos = 0) const noexcept
      { return this->find_first_of(__str, __pos, traits_type::length(__str)); }
 
      [[nodiscard]]
      constexpr size_type
      find_last_of(basic_string_view __str,
                   size_type __pos = npos) const noexcept
      { return this->find_last_of(__str._M_str, __pos, __str._M_len); }
 
      [[nodiscard]]
      constexpr size_type
      find_last_of(_CharT __c, size_type __pos=npos) const noexcept
      { return this->rfind(__c, __pos); }
 
      [[nodiscard]]
      constexpr size_type
      find_last_of(const _CharT* __str, size_type __pos,
                   size_type __n) const noexcept;
 
      [[nodiscard, __gnu__::__nonnull__]]
      constexpr size_type
      find_last_of(const _CharT* __str, size_type __pos = npos) const noexcept
      { return this->find_last_of(__str, __pos, traits_type::length(__str)); }
 
      [[nodiscard]]
      constexpr size_type
      find_first_not_of(basic_string_view __str,
                        size_type __pos = 0) const noexcept
      { return this->find_first_not_of(__str._M_str, __pos, __str._M_len); }
 
      [[nodiscard]]
      constexpr size_type
      find_first_not_of(_CharT __c, size_type __pos = 0) const noexcept;
 
      [[nodiscard]]
      constexpr size_type
      find_first_not_of(const _CharT* __str,
                        size_type __pos, size_type __n) const noexcept;
 
      [[nodiscard, __gnu__::__nonnull__]]
      constexpr size_type
      find_first_not_of(const _CharT* __str, size_type __pos = 0) const noexcept
      {
        return this->find_first_not_of(__str, __pos,
                                       traits_type::length(__str));
      }
 
      [[nodiscard]]
      constexpr size_type
      find_last_not_of(basic_string_view __str,
                       size_type __pos = npos) const noexcept
      { return this->find_last_not_of(__str._M_str, __pos, __str._M_len); }
 
      [[nodiscard]]
      constexpr size_type
      find_last_not_of(_CharT __c, size_type __pos = npos) const noexcept;
 
      [[nodiscard]]
      constexpr size_type
      find_last_not_of(const _CharT* __str,
                       size_type __pos, size_type __n) const noexcept;
 
      [[nodiscard, __gnu__::__nonnull__]]
      constexpr size_type
      find_last_not_of(const _CharT* __str,
                       size_type __pos = npos) const noexcept
      {
        return this->find_last_not_of(__str, __pos,
                                      traits_type::length(__str));
      }
 
    private:
 
      static constexpr int
      _S_compare(size_type __n1, size_type __n2) noexcept
      {
        using __limits = __gnu_cxx::__int_traits<int>;
        const difference_type __diff = __n1 - __n2;
        if (__diff > __limits::__max)
          return __limits::__max;
        if (__diff < __limits::__min)
          return __limits::__min;
        return static_cast<int>(__diff);
      }
 
      size_t        _M_len;
      const _CharT* _M_str;
    };
 
#if __cplusplus > 201703L && __cpp_lib_concepts && __cpp_deduction_guides
  template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
    basic_string_view(_It, _End) -> basic_string_view<iter_value_t<_It>>;
 
#if __cplusplus > 202002L
  template<ranges::contiguous_range _Range>
    basic_string_view(_Range&&)
      -> basic_string_view<ranges::range_value_t<_Range>>;
#endif
#endif
 
  // [string.view.comparison], non-member basic_string_view comparison function
 
  // Several of these functions use type_identity_t to create a non-deduced
  // context, so that only one argument participates in template argument
  // deduction and the other argument gets implicitly converted to the deduced
  // type (see N3766).
 
#if __cpp_lib_three_way_comparison
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator==(basic_string_view<_CharT, _Traits> __x,
               type_identity_t<basic_string_view<_CharT, _Traits>> __y)
    noexcept
    { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr auto
    operator<=>(basic_string_view<_CharT, _Traits> __x,
                __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
    noexcept
    -> decltype(__detail::__char_traits_cmp_cat<_Traits>(0))
    { return __detail::__char_traits_cmp_cat<_Traits>(__x.compare(__y)); }
#else
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator==(basic_string_view<_CharT, _Traits> __x,
               __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
    noexcept
    { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator==(basic_string_view<_CharT, _Traits> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator!=(basic_string_view<_CharT, _Traits> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return !(__x == __y); }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator!=(basic_string_view<_CharT, _Traits> __x,
               __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
    noexcept
    { return !(__x == __y); }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return !(__x == __y); }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator< (basic_string_view<_CharT, _Traits> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) < 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator< (basic_string_view<_CharT, _Traits> __x,
               __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
    noexcept
    { return __x.compare(__y) < 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) < 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator> (basic_string_view<_CharT, _Traits> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) > 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator> (basic_string_view<_CharT, _Traits> __x,
               __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
    noexcept
    { return __x.compare(__y) > 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator> (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) > 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator<=(basic_string_view<_CharT, _Traits> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) <= 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator<=(basic_string_view<_CharT, _Traits> __x,
               __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
    noexcept
    { return __x.compare(__y) <= 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator<=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) <= 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator>=(basic_string_view<_CharT, _Traits> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) >= 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator>=(basic_string_view<_CharT, _Traits> __x,
               __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
    noexcept
    { return __x.compare(__y) >= 0; }
 
  template<typename _CharT, typename _Traits>
    [[nodiscard]]
    constexpr bool
    operator>=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) >= 0; }
#endif // three-way comparison
 
#if _GLIBCXX_HOSTED
  // [string.view.io], Inserters and extractors
  template<typename _CharT, typename _Traits>
    inline basic_ostream<_CharT, _Traits>&
    operator<<(basic_ostream<_CharT, _Traits>& __os,
               basic_string_view<_CharT,_Traits> __str)
    { return __ostream_insert(__os, __str.data(), __str.size()); }
#endif // HOSTED
 
  // basic_string_view typedef names
 
  using string_view = basic_string_view<char>;
  using wstring_view = basic_string_view<wchar_t>;
#ifdef _GLIBCXX_USE_CHAR8_T
  using u8string_view = basic_string_view<char8_t>;
#endif
  using u16string_view = basic_string_view<char16_t>;
  using u32string_view = basic_string_view<char32_t>;
 
  // [string.view.hash], hash support:
 
  template<typename _Tp>
    struct hash;
 
  template<>
    struct hash<string_view>
    : public __hash_base<size_t, string_view>
    {
      [[nodiscard]]
      size_t
      operator()(const string_view& __str) const noexcept
      { return std::_Hash_impl::hash(__str.data(), __str.length()); }
    };
 
  template<>
    struct __is_fast_hash<hash<string_view>> : std::false_type
    { };
 
  template<>
    struct hash<wstring_view>
    : public __hash_base<size_t, wstring_view>
    {
      [[nodiscard]]
      size_t
      operator()(const wstring_view& __s) const noexcept
      { return std::_Hash_impl::hash(__s.data(),
                                     __s.length() * sizeof(wchar_t)); }
    };
 
  template<>
    struct __is_fast_hash<hash<wstring_view>> : std::false_type
    { };
 
#ifdef _GLIBCXX_USE_CHAR8_T
  template<>
    struct hash<u8string_view>
    : public __hash_base<size_t, u8string_view>
    {
      [[nodiscard]]
      size_t
      operator()(const u8string_view& __str) const noexcept
      { return std::_Hash_impl::hash(__str.data(), __str.length()); }
    };
 
  template<>
    struct __is_fast_hash<hash<u8string_view>> : std::false_type
    { };
#endif
 
  template<>
    struct hash<u16string_view>
    : public __hash_base<size_t, u16string_view>
    {
      [[nodiscard]]
      size_t
      operator()(const u16string_view& __s) const noexcept
      { return std::_Hash_impl::hash(__s.data(),
                                     __s.length() * sizeof(char16_t)); }
    };
 
  template<>
    struct __is_fast_hash<hash<u16string_view>> : std::false_type
    { };
 
  template<>
    struct hash<u32string_view>
    : public __hash_base<size_t, u32string_view>
    {
      [[nodiscard]]
      size_t
      operator()(const u32string_view& __s) const noexcept
      { return std::_Hash_impl::hash(__s.data(),
                                     __s.length() * sizeof(char32_t)); }
    };
 
  template<>
    struct __is_fast_hash<hash<u32string_view>> : std::false_type
    { };
 
  inline namespace literals
  {
  inline namespace string_view_literals
  {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wliteral-suffix"
    inline constexpr basic_string_view<char>
    operator""sv(const char* __str, size_t __len) noexcept
    { return basic_string_view<char>{__str, __len}; }
 
    inline constexpr basic_string_view<wchar_t>
    operator""sv(const wchar_t* __str, size_t __len) noexcept
    { return basic_string_view<wchar_t>{__str, __len}; }
 
#ifdef _GLIBCXX_USE_CHAR8_T
    inline constexpr basic_string_view<char8_t>
    operator""sv(const char8_t* __str, size_t __len) noexcept
    { return basic_string_view<char8_t>{__str, __len}; }
#endif
 
    inline constexpr basic_string_view<char16_t>
    operator""sv(const char16_t* __str, size_t __len) noexcept
    { return basic_string_view<char16_t>{__str, __len}; }
 
    inline constexpr basic_string_view<char32_t>
    operator""sv(const char32_t* __str, size_t __len) noexcept
    { return basic_string_view<char32_t>{__str, __len}; }
 
#pragma GCC diagnostic pop
  } // namespace string_literals
  } // namespace literals
 
#if __cpp_lib_concepts
  namespace ranges
  {
    // Opt-in to borrowed_range concept
    template<typename _CharT, typename _Traits>
      inline constexpr bool
        enable_borrowed_range<basic_string_view<_CharT, _Traits>> = true;
 
    // Opt-in to view concept
    template<typename _CharT, typename _Traits>
      inline constexpr bool
        enable_view<basic_string_view<_CharT, _Traits>> = true;
  }
#endif
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
 
#include <bits/string_view.tcc>
 
#endif // __cplusplus <= 201402L
 
#endif // _GLIBCXX_EXPERIMENTAL_STRING_VIEW