char_traits.h

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___STRING_CHAR_TRAITS_H
#define _LIBCPP___STRING_CHAR_TRAITS_H

#include <__algorithm/copy_n.h>
#include <__algorithm/fill_n.h>
#include <__algorithm/find_end.h>
#include <__algorithm/find_first_of.h>
#include <__algorithm/min.h>
#include <__compare/ordering.h>
#include <__config>
#include <__functional/hash.h>
#include <__iterator/iterator_traits.h>
#include <__type_traits/is_constant_evaluated.h>
#include <cstddef>
#include <cstdint>
#include <cstdio>
#include <cstring>
#include <iosfwd>

#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
#   include <cwchar> // for wmemcpy
#endif

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _CharT>
struct char_traits;
/*
The Standard does not define the base template for char_traits because it is impossible to provide
a correct definition for arbitrary character types. Instead, it requires implementations to provide
specializations for predefined character types like `char`, `wchar_t` and others. We provide this as
exposition-only to document what members a char_traits specialization should provide:
{
    using char_type  = _CharT;
    using int_type   = ...;
    using off_type   = ...;
    using pos_type   = ...;
    using state_type = ...;

    static void assign(char_type&, const char_type&);
    static bool eq(char_type, char_type);
    static bool lt(char_type, char_type);

    static int              compare(const char_type*, const char_type*, size_t);
    static size_t           length(const char_type*);
    static const char_type* find(const char_type*, size_t, const char_type&);
    static char_type*       move(char_type*, const char_type*, size_t);
    static char_type*       copy(char_type*, const char_type*, size_t);
    static char_type*       assign(char_type*, size_t, char_type);

    static int_type  not_eof(int_type);
    static char_type to_char_type(int_type);
    static int_type  to_int_type(char_type);
    static bool      eq_int_type(int_type, int_type);
    static int_type  eof();
};
*/

//
// Temporary extension to provide a base template for std::char_traits.
// TODO: Remove in LLVM 18.
//
template <class _CharT>
struct _LIBCPP_DEPRECATED_("char_traits<T> for T not equal to char, wchar_t, char8_t, char16_t or char32_t is non-standard and is provided for a temporary period. It will be removed in LLVM 18, so please migrate off of it.")
    char_traits
{
    using char_type  = _CharT;
    using int_type   = int;
    using off_type   = streamoff;
    using pos_type   = streampos;
    using state_type = mbstate_t;

    static inline void _LIBCPP_CONSTEXPR_SINCE_CXX17
        assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
        {return __c1 == __c2;}
    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
        {return __c1 < __c2;}

    static _LIBCPP_CONSTEXPR_SINCE_CXX17
    int compare(const char_type* __s1, const char_type* __s2, size_t __n) {
        for (; __n; --__n, ++__s1, ++__s2)
        {
            if (lt(*__s1, *__s2))
                return -1;
            if (lt(*__s2, *__s1))
                return 1;
        }
        return 0;
    }
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_SINCE_CXX17
    size_t length(const char_type* __s) {
        size_t __len = 0;
        for (; !eq(*__s, char_type(0)); ++__s)
            ++__len;
        return __len;
    }
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_SINCE_CXX17
    const char_type* find(const char_type* __s, size_t __n, const char_type& __a) {
        for (; __n; --__n)
        {
            if (eq(*__s, __a))
                return __s;
            ++__s;
        }
        return nullptr;
    }
    static _LIBCPP_CONSTEXPR_SINCE_CXX20
    char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) {
        if (__n == 0) return __s1;
        char_type* __r = __s1;
        if (__s1 < __s2)
        {
            for (; __n; --__n, ++__s1, ++__s2)
                assign(*__s1, *__s2);
        }
        else if (__s2 < __s1)
        {
            __s1 += __n;
            __s2 += __n;
            for (; __n; --__n)
                assign(*--__s1, *--__s2);
        }
        return __r;
    }
    _LIBCPP_INLINE_VISIBILITY
    static _LIBCPP_CONSTEXPR_SINCE_CXX20
    char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n) {
        if (!__libcpp_is_constant_evaluated()) {
            _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
        }
        char_type* __r = __s1;
        for (; __n; --__n, ++__s1, ++__s2)
            assign(*__s1, *__s2);
        return __r;
    }
    _LIBCPP_INLINE_VISIBILITY
    static _LIBCPP_CONSTEXPR_SINCE_CXX20
    char_type*       assign(char_type* __s, size_t __n, char_type __a) {
        char_type* __r = __s;
        for (; __n; --__n, ++__s)
            assign(*__s, __a);
        return __r;
    }

    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
        {return char_type(__c);}
    static inline _LIBCPP_CONSTEXPR int_type  to_int_type(char_type __c) _NOEXCEPT
        {return int_type(__c);}
    static inline _LIBCPP_CONSTEXPR bool      eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
        {return __c1 == __c2;}
    static inline _LIBCPP_CONSTEXPR int_type  eof() _NOEXCEPT
        {return int_type(EOF);}
};

template <class _CharT>
_LIBCPP_HIDE_FROM_ABI static inline _LIBCPP_CONSTEXPR_SINCE_CXX20
_CharT* __char_traits_move(_CharT* __dest, const _CharT* __source, size_t __n) _NOEXCEPT
{
#ifdef _LIBCPP_COMPILER_GCC
  if (__libcpp_is_constant_evaluated()) {
    if (__n == 0)
      return __dest;
    _CharT* __allocation = new _CharT[__n];
    std::copy_n(__source, __n, __allocation);
    std::copy_n(static_cast<const _CharT*>(__allocation), __n, __dest);
    delete[] __allocation;
    return __dest;
  }
#endif
  ::__builtin_memmove(__dest, __source, __n * sizeof(_CharT));
  return __dest;
}

// char_traits<char>

template <>
struct _LIBCPP_TEMPLATE_VIS char_traits<char>
{
    using char_type           = char;
    using int_type            = int;
    using off_type            = streamoff;
    using pos_type            = streampos;
    using state_type          = mbstate_t;
#if _LIBCPP_STD_VER > 17
    using comparison_category = strong_ordering;
#endif

    static inline _LIBCPP_CONSTEXPR_SINCE_CXX17
    void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
            {return __c1 == __c2;}
    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
        {return (unsigned char)__c1 < (unsigned char)__c2;}

  static _LIBCPP_CONSTEXPR_SINCE_CXX17 int compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
    if (__n == 0)
      return 0;
    return std::__constexpr_memcmp(__s1, __s2, __n);
  }

  static inline size_t _LIBCPP_CONSTEXPR_SINCE_CXX17 length(const char_type* __s)  _NOEXCEPT {
    return std::__constexpr_strlen(__s);
  }

  static _LIBCPP_CONSTEXPR_SINCE_CXX17
  const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT {
    if (__n == 0)
        return nullptr;
    return std::__constexpr_char_memchr(__s, static_cast<int>(__a), __n);
  }

    static inline _LIBCPP_CONSTEXPR_SINCE_CXX20
    char_type* move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
        return std::__char_traits_move(__s1, __s2, __n);
    }

    static inline _LIBCPP_CONSTEXPR_SINCE_CXX20
    char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
        if (!__libcpp_is_constant_evaluated())
            _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
        std::copy_n(__s2, __n, __s1);
        return __s1;
    }

    static inline _LIBCPP_CONSTEXPR_SINCE_CXX20
    char_type* assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT {
        std::fill_n(__s, __n, __a);
        return __s;
    }

    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
        {return char_type(__c);}
    static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
        {return int_type((unsigned char)__c);}
    static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
        {return __c1 == __c2;}
    static inline _LIBCPP_CONSTEXPR int_type  eof() _NOEXCEPT
        {return int_type(EOF);}
};

// char_traits<wchar_t>

#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
template <>
struct _LIBCPP_TEMPLATE_VIS char_traits<wchar_t>
{
    using char_type           = wchar_t;
    using int_type            = wint_t;
    using off_type            = streamoff;
    using pos_type            = streampos;
    using state_type          = mbstate_t;
#if _LIBCPP_STD_VER > 17
    using comparison_category = strong_ordering;
#endif

    static inline _LIBCPP_CONSTEXPR_SINCE_CXX17
    void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
        {return __c1 == __c2;}
    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
        {return __c1 < __c2;}

  static _LIBCPP_CONSTEXPR_SINCE_CXX17 int compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
    if (__n == 0)
        return 0;
    return std::__constexpr_wmemcmp(__s1, __s2, __n);
  }

  static _LIBCPP_CONSTEXPR_SINCE_CXX17 size_t length(const char_type* __s) _NOEXCEPT {
    return std::__constexpr_wcslen(__s);
  }

  static _LIBCPP_CONSTEXPR_SINCE_CXX17
  const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT {
    if (__n == 0)
        return nullptr;
    return std::__constexpr_wmemchr(__s, __a, __n);
  }

    static inline _LIBCPP_CONSTEXPR_SINCE_CXX20
    char_type* move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
        return std::__char_traits_move(__s1, __s2, __n);
    }

    static inline _LIBCPP_CONSTEXPR_SINCE_CXX20
    char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
        if (!__libcpp_is_constant_evaluated())
            _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
        std::copy_n(__s2, __n, __s1);
        return __s1;
    }

    static inline _LIBCPP_CONSTEXPR_SINCE_CXX20
    char_type* assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT {
        std::fill_n(__s, __n, __a);
        return __s;
    }

    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
        {return char_type(__c);}
    static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
        {return int_type(__c);}
    static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
        {return __c1 == __c2;}
    static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
        {return int_type(WEOF);}
};
#endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS

#ifndef _LIBCPP_HAS_NO_CHAR8_T

template <>
struct _LIBCPP_TEMPLATE_VIS char_traits<char8_t>
{
    using char_type           = char8_t;
    using int_type            = unsigned int;
    using off_type            = streamoff;
    using pos_type            = u8streampos;
    using state_type          = mbstate_t;
#if _LIBCPP_STD_VER > 17
    using comparison_category = strong_ordering;
#endif

    static inline constexpr void assign(char_type& __c1, const char_type& __c2) noexcept
        {__c1 = __c2;}
    static inline constexpr bool eq(char_type __c1, char_type __c2) noexcept
        {return __c1 == __c2;}
    static inline constexpr bool lt(char_type __c1, char_type __c2) noexcept
        {return __c1 < __c2;}

  static _LIBCPP_HIDE_FROM_ABI constexpr int
  compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
      return std::__constexpr_memcmp(__s1, __s2, __n);
  }

    static constexpr
    size_t           length(const char_type* __s) _NOEXCEPT;

    _LIBCPP_INLINE_VISIBILITY static constexpr
    const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;

    static _LIBCPP_CONSTEXPR_SINCE_CXX20
    char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
        return std::__char_traits_move(__s1, __s2, __n);
    }

    static _LIBCPP_CONSTEXPR_SINCE_CXX20
    char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
        if (!__libcpp_is_constant_evaluated())
            _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
        std::copy_n(__s2, __n, __s1);
        return __s1;
    }

    static _LIBCPP_CONSTEXPR_SINCE_CXX20
    char_type*       assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT {
        std::fill_n(__s, __n, __a);
        return __s;
    }

    static inline constexpr int_type  not_eof(int_type __c) noexcept
        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
    static inline constexpr char_type to_char_type(int_type __c) noexcept
        {return char_type(__c);}
    static inline constexpr int_type to_int_type(char_type __c) noexcept
        {return int_type(__c);}
    static inline constexpr bool eq_int_type(int_type __c1, int_type __c2) noexcept
        {return __c1 == __c2;}
    static inline constexpr int_type eof() noexcept
        {return int_type(EOF);}
};

// TODO use '__builtin_strlen' if it ever supports char8_t ??
inline constexpr
size_t
char_traits<char8_t>::length(const char_type* __s) _NOEXCEPT
{
    size_t __len = 0;
    for (; !eq(*__s, char_type(0)); ++__s)
        ++__len;
    return __len;
}

// TODO use '__builtin_char_memchr' if it ever supports char8_t ??
inline constexpr
const char8_t*
char_traits<char8_t>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
{
    for (; __n; --__n)
    {
        if (eq(*__s, __a))
            return __s;
        ++__s;
    }
    return nullptr;
}

#endif // _LIBCPP_HAS_NO_CHAR8_T

template <>
struct _LIBCPP_TEMPLATE_VIS char_traits<char16_t>
{
    using char_type           = char16_t;
    using int_type            = uint_least16_t;
    using off_type            = streamoff;
    using pos_type            = u16streampos;
    using state_type          = mbstate_t;
#if _LIBCPP_STD_VER > 17
    using comparison_category = strong_ordering;
#endif

    static inline _LIBCPP_CONSTEXPR_SINCE_CXX17
    void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
        {return __c1 == __c2;}
    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
        {return __c1 < __c2;}

    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_SINCE_CXX17
    int              compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_SINCE_CXX17
    size_t           length(const char_type* __s) _NOEXCEPT;
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_SINCE_CXX17
    const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
    static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
        return std::__char_traits_move(__s1, __s2, __n);
    }

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
    static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
        if (!__libcpp_is_constant_evaluated())
            _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
        std::copy_n(__s2, __n, __s1);
        return __s1;
    }

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
    static char_type*       assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT {
        std::fill_n(__s, __n, __a);
        return __s;
    }

    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
        {return char_type(__c);}
    static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
        {return int_type(__c);}
    static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
        {return __c1 == __c2;}
    static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
        {return int_type(0xFFFF);}
};

inline _LIBCPP_CONSTEXPR_SINCE_CXX17
int
char_traits<char16_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
{
    for (; __n; --__n, ++__s1, ++__s2)
    {
        if (lt(*__s1, *__s2))
            return -1;
        if (lt(*__s2, *__s1))
            return 1;
    }
    return 0;
}

inline _LIBCPP_CONSTEXPR_SINCE_CXX17
size_t
char_traits<char16_t>::length(const char_type* __s) _NOEXCEPT
{
    size_t __len = 0;
    for (; !eq(*__s, char_type(0)); ++__s)
        ++__len;
    return __len;
}

inline _LIBCPP_CONSTEXPR_SINCE_CXX17
const char16_t*
char_traits<char16_t>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
{
    for (; __n; --__n)
    {
        if (eq(*__s, __a))
            return __s;
        ++__s;
    }
    return nullptr;
}

template <>
struct _LIBCPP_TEMPLATE_VIS char_traits<char32_t>
{
    using char_type           = char32_t;
    using int_type            = uint_least32_t;
    using off_type            = streamoff;
    using pos_type            = u32streampos;
    using state_type          = mbstate_t;
#if _LIBCPP_STD_VER > 17
    using comparison_category = strong_ordering;
#endif

    static inline _LIBCPP_CONSTEXPR_SINCE_CXX17
    void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
        {return __c1 == __c2;}
    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
        {return __c1 < __c2;}

    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_SINCE_CXX17
    int              compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_SINCE_CXX17
    size_t           length(const char_type* __s) _NOEXCEPT;
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_SINCE_CXX17
    const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
    static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
        return std::__char_traits_move(__s1, __s2, __n);
    }

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
    static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
        std::copy_n(__s2, __n, __s1);
        return __s1;
    }

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
    static char_type*       assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT {
        std::fill_n(__s, __n, __a);
        return __s;
    }

    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
        {return char_type(__c);}
    static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
        {return int_type(__c);}
    static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
        {return __c1 == __c2;}
    static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
        {return int_type(0xFFFFFFFF);}
};

inline _LIBCPP_CONSTEXPR_SINCE_CXX17
int
char_traits<char32_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
{
    for (; __n; --__n, ++__s1, ++__s2)
    {
        if (lt(*__s1, *__s2))
            return -1;
        if (lt(*__s2, *__s1))
            return 1;
    }
    return 0;
}

inline _LIBCPP_CONSTEXPR_SINCE_CXX17
size_t
char_traits<char32_t>::length(const char_type* __s) _NOEXCEPT
{
    size_t __len = 0;
    for (; !eq(*__s, char_type(0)); ++__s)
        ++__len;
    return __len;
}

inline _LIBCPP_CONSTEXPR_SINCE_CXX17
const char32_t*
char_traits<char32_t>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
{
    for (; __n; --__n)
    {
        if (eq(*__s, __a))
            return __s;
        ++__s;
    }
    return nullptr;
}

// helper fns for basic_string and string_view

// __str_find
template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
inline _SizeT _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_INLINE_VISIBILITY
__str_find(const _CharT *__p, _SizeT __sz,
             _CharT __c, _SizeT __pos) _NOEXCEPT
{
    if (__pos >= __sz)
        return __npos;
    const _CharT* __r = _Traits::find(__p + __pos, __sz - __pos, __c);
    if (__r == nullptr)
        return __npos;
    return static_cast<_SizeT>(__r - __p);
}

template <class _CharT, class _Traits>
_LIBCPP_HIDE_FROM_ABI inline _LIBCPP_CONSTEXPR_SINCE_CXX14 const _CharT *
__search_substring(const _CharT *__first1, const _CharT *__last1,
                   const _CharT *__first2, const _CharT *__last2) _NOEXCEPT {
  // Take advantage of knowing source and pattern lengths.
  // Stop short when source is smaller than pattern.
  const ptrdiff_t __len2 = __last2 - __first2;
  if (__len2 == 0)
    return __first1;

  ptrdiff_t __len1 = __last1 - __first1;
  if (__len1 < __len2)
    return __last1;

  // First element of __first2 is loop invariant.
  _CharT __f2 = *__first2;
  while (true) {
    __len1 = __last1 - __first1;
    // Check whether __first1 still has at least __len2 bytes.
    if (__len1 < __len2)
      return __last1;

    // Find __f2 the first byte matching in __first1.
    __first1 = _Traits::find(__first1, __len1 - __len2 + 1, __f2);
    if (__first1 == nullptr)
      return __last1;

    // It is faster to compare from the first byte of __first1 even if we
    // already know that it matches the first byte of __first2: this is because
    // __first2 is most likely aligned, as it is user's "pattern" string, and
    // __first1 + 1 is most likely not aligned, as the match is in the middle of
    // the string.
    if (_Traits::compare(__first1, __first2, __len2) == 0)
      return __first1;

    ++__first1;
  }
}

template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
inline _SizeT _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_INLINE_VISIBILITY
__str_find(const _CharT *__p, _SizeT __sz,
       const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
{
    if (__pos > __sz)
        return __npos;

    if (__n == 0) // There is nothing to search, just return __pos.
        return __pos;

    const _CharT *__r = std::__search_substring<_CharT, _Traits>(
        __p + __pos, __p + __sz, __s, __s + __n);

    if (__r == __p + __sz)
        return __npos;
    return static_cast<_SizeT>(__r - __p);
}


// __str_rfind

template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
inline _SizeT _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_INLINE_VISIBILITY
__str_rfind(const _CharT *__p, _SizeT __sz,
              _CharT __c, _SizeT __pos) _NOEXCEPT
{
    if (__sz < 1)
        return __npos;
    if (__pos < __sz)
        ++__pos;
    else
        __pos = __sz;
    for (const _CharT* __ps = __p + __pos; __ps != __p;)
    {
        if (_Traits::eq(*--__ps, __c))
            return static_cast<_SizeT>(__ps - __p);
    }
    return __npos;
}

template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
inline _SizeT _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_INLINE_VISIBILITY
__str_rfind(const _CharT *__p, _SizeT __sz,
        const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
{
    __pos = _VSTD::min(__pos, __sz);
    if (__n < __sz - __pos)
        __pos += __n;
    else
        __pos = __sz;
    const _CharT* __r = std::__find_end_classic(__p, __p + __pos, __s, __s + __n, _Traits::eq);
    if (__n > 0 && __r == __p + __pos)
        return __npos;
    return static_cast<_SizeT>(__r - __p);
}

// __str_find_first_of
template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
inline _SizeT _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_INLINE_VISIBILITY
__str_find_first_of(const _CharT *__p, _SizeT __sz,
                const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
{
    if (__pos >= __sz || __n == 0)
        return __npos;
    const _CharT* __r = _VSTD::__find_first_of_ce
        (__p + __pos, __p + __sz, __s, __s + __n, _Traits::eq );
    if (__r == __p + __sz)
        return __npos;
    return static_cast<_SizeT>(__r - __p);
}


// __str_find_last_of
template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
inline _SizeT _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_INLINE_VISIBILITY
__str_find_last_of(const _CharT *__p, _SizeT __sz,
               const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
    {
    if (__n != 0)
    {
        if (__pos < __sz)
            ++__pos;
        else
            __pos = __sz;
        for (const _CharT* __ps = __p + __pos; __ps != __p;)
        {
            const _CharT* __r = _Traits::find(__s, __n, *--__ps);
            if (__r)
                return static_cast<_SizeT>(__ps - __p);
        }
    }
    return __npos;
}


// __str_find_first_not_of
template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
inline _SizeT _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_INLINE_VISIBILITY
__str_find_first_not_of(const _CharT *__p, _SizeT __sz,
                    const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
{
    if (__pos < __sz)
    {
        const _CharT* __pe = __p + __sz;
        for (const _CharT* __ps = __p + __pos; __ps != __pe; ++__ps)
            if (_Traits::find(__s, __n, *__ps) == nullptr)
                return static_cast<_SizeT>(__ps - __p);
    }
    return __npos;
}


template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
inline _SizeT _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_INLINE_VISIBILITY
__str_find_first_not_of(const _CharT *__p, _SizeT __sz,
                          _CharT __c, _SizeT __pos) _NOEXCEPT
{
    if (__pos < __sz)
    {
        const _CharT* __pe = __p + __sz;
        for (const _CharT* __ps = __p + __pos; __ps != __pe; ++__ps)
            if (!_Traits::eq(*__ps, __c))
                return static_cast<_SizeT>(__ps - __p);
    }
    return __npos;
}


// __str_find_last_not_of
template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
inline _SizeT _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_INLINE_VISIBILITY
__str_find_last_not_of(const _CharT *__p, _SizeT __sz,
                   const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
{
    if (__pos < __sz)
        ++__pos;
    else
        __pos = __sz;
    for (const _CharT* __ps = __p + __pos; __ps != __p;)
        if (_Traits::find(__s, __n, *--__ps) == nullptr)
            return static_cast<_SizeT>(__ps - __p);
    return __npos;
}


template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
inline _SizeT _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_INLINE_VISIBILITY
__str_find_last_not_of(const _CharT *__p, _SizeT __sz,
                         _CharT __c, _SizeT __pos) _NOEXCEPT
{
    if (__pos < __sz)
        ++__pos;
    else
        __pos = __sz;
    for (const _CharT* __ps = __p + __pos; __ps != __p;)
        if (!_Traits::eq(*--__ps, __c))
            return static_cast<_SizeT>(__ps - __p);
    return __npos;
}

template<class _Ptr>
inline _LIBCPP_INLINE_VISIBILITY
size_t __do_string_hash(_Ptr __p, _Ptr __e)
{
    typedef typename iterator_traits<_Ptr>::value_type value_type;
    return __murmur2_or_cityhash<size_t>()(__p, (__e-__p)*sizeof(value_type));
}

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___STRING_CHAR_TRAITS_H