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// -*- C++ -*- 
//===-------------------------- __string ----------------------------------===// 
// 
// 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 
#define _LIBCPP___STRING 
 
#include <__config> 
#include <__algorithm/copy.h> 
#include <__algorithm/copy_backward.h> 
#include <__algorithm/copy_n.h> 
#include <__algorithm/fill_n.h> 
#include <__algorithm/find_first_of.h> 
#include <__algorithm/find_end.h> 
#include <__algorithm/min.h> 
#include <__functional/hash.h>     // for __murmur2_or_cityhash 
#include <__iterator/iterator_traits.h> 
#include <cstdio>      // for EOF 
#include <cstdint>     // for uint_least16_t 
#include <cstring>     // for memcpy 
#include <type_traits> // for __libcpp_is_constant_evaluated 
#include <iosfwd>      // for streampos & friends 
 
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS 
#   include <cwchar> // for wmemcpy 
#endif 
 
#include <__debug> 
 
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 
#pragma GCC system_header 
#endif 
 
_LIBCPP_PUSH_MACROS 
#include <__undef_macros> 
 
 
_LIBCPP_BEGIN_NAMESPACE_STD 
 
// The the extern template ABI lists are kept outside of <string> to improve the 
// readability of that header. 
 
// The extern template ABI lists are kept outside of <string> to improve the 
// readability of that header. We maintain 2 ABI lists: 
// - _LIBCPP_STRING_V1_EXTERN_TEMPLATE_LIST 
// - _LIBCPP_STRING_UNSTABLE_EXTERN_TEMPLATE_LIST 
// As the name implies, the ABI lists define the V1 (Stable) and unstable ABI. 
// 
// For unstable, we may explicitly remove function that are external in V1, 
// and add (new) external functions to better control inlining and compiler 
// optimization opportunities. 
// 
// For stable, the ABI list should rarely change, except for adding new 
// functions supporting new c++ version / API changes. Typically entries 
// must never be removed from the stable list. 
#define _LIBCPP_STRING_V1_EXTERN_TEMPLATE_LIST(_Func, _CharType) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, value_type const*, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::rfind(value_type const*, size_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__init(value_type const*, size_type, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::basic_string(basic_string const&)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, value_type const*)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::basic_string(basic_string const&, allocator<_CharType> const&)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_last_not_of(value_type const*, size_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::~basic_string()) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_first_not_of(value_type const*, size_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, size_type, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::operator=(value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__init(value_type const*, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS const _CharType& basic_string<_CharType>::at(size_type) const) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, value_type const*, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_first_of(value_type const*, size_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, size_type, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::assign(value_type const*, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::reserve(size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::append(value_type const*, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::assign(basic_string const&, size_type, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::copy(value_type*, size_type, size_type) const) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::basic_string(basic_string const&, size_type, size_type, allocator<_CharType> const&)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find(value_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__init(size_type, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, value_type const*)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_last_of(value_type const*, size_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__grow_by(size_type, size_type, size_type, size_type, size_type, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__grow_by_and_replace(size_type, size_type, size_type, size_type, size_type, size_type, value_type const*)) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::push_back(value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::append(size_type, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::rfind(value_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::assign(size_type, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::erase(size_type, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::append(basic_string const&, size_type, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS int basic_string<_CharType>::compare(value_type const*) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS int basic_string<_CharType>::compare(size_type, size_type, value_type const*) const) \ 
  _Func(_LIBCPP_FUNC_VIS _CharType& basic_string<_CharType>::at(size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::assign(value_type const*)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find(value_type const*, size_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS int basic_string<_CharType>::compare(size_type, size_type, basic_string const&, size_type, size_type) const) \ 
  _Func(_LIBCPP_FUNC_VIS int basic_string<_CharType>::compare(size_type, size_type, value_type const*, size_type) const) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::operator=(basic_string const&)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::append(value_type const*)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, basic_string const&, size_type, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::iterator basic_string<_CharType>::insert(basic_string::const_iterator, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::resize(size_type, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, basic_string const&, size_type, size_type)) \ 
  _LIBCPP_STRING_EXTERN_TEMPLATE_VARIABLE_LIST(_Func, _CharType) 
 
#define _LIBCPP_STRING_UNSTABLE_EXTERN_TEMPLATE_LIST(_Func, _CharType) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, value_type const*, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::rfind(value_type const*, size_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__init(value_type const*, size_type, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, value_type const*)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_last_not_of(value_type const*, size_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::~basic_string()) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_first_not_of(value_type const*, size_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, size_type, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::operator=(value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__init(value_type const*, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__init_copy_ctor_external(value_type const*, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS const _CharType& basic_string<_CharType>::at(size_type) const) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, value_type const*, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_first_of(value_type const*, size_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, size_type, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::__assign_external(value_type const*, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::__assign_external(value_type const*)) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::reserve(size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::append(value_type const*, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::assign(basic_string const&, size_type, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::copy(value_type*, size_type, size_type) const) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::basic_string(basic_string const&, size_type, size_type, allocator<_CharType> const&)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find(value_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__init(size_type, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, value_type const*)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find_last_of(value_type const*, size_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__grow_by(size_type, size_type, size_type, size_type, size_type, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__grow_by_and_replace(size_type, size_type, size_type, size_type, size_type, size_type, value_type const*)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::__assign_no_alias<false>(value_type const*, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::__assign_no_alias<true>(value_type const*, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::push_back(value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::append(size_type, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::rfind(value_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::assign(size_type, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::__erase_external_with_move(size_type, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::append(basic_string const&, size_type, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS int basic_string<_CharType>::compare(value_type const*) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS int basic_string<_CharType>::compare(size_type, size_type, value_type const*) const) \ 
  _Func(_LIBCPP_FUNC_VIS _CharType& basic_string<_CharType>::at(size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::size_type basic_string<_CharType>::find(value_type const*, size_type, size_type) const _NOEXCEPT) \ 
  _Func(_LIBCPP_FUNC_VIS int basic_string<_CharType>::compare(size_type, size_type, basic_string const&, size_type, size_type) const) \ 
  _Func(_LIBCPP_FUNC_VIS int basic_string<_CharType>::compare(size_type, size_type, value_type const*, size_type) const) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::append(value_type const*)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::replace(size_type, size_type, basic_string const&, size_type, size_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>::iterator basic_string<_CharType>::insert(basic_string::const_iterator, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS void basic_string<_CharType>::resize(size_type, value_type)) \ 
  _Func(_LIBCPP_FUNC_VIS basic_string<_CharType>& basic_string<_CharType>::insert(size_type, basic_string const&, size_type, size_type)) \ 
  _LIBCPP_STRING_EXTERN_TEMPLATE_VARIABLE_LIST(_Func, _CharType) 
 
// Workaround for CUDA which doesn't like extern templates for variables. 
#ifdef __CUDACC__ 
#define _LIBCPP_STRING_EXTERN_TEMPLATE_VARIABLE_LIST(_Func, _CharType) 
#else 
#define _LIBCPP_STRING_EXTERN_TEMPLATE_VARIABLE_LIST(_Func, _CharType) \ 
  _Func(_LIBCPP_FUNC_VIS const basic_string<_CharType>::size_type basic_string<_CharType>::npos) 
#endif 
 
// char_traits 
 
template <class _CharT> 
struct _LIBCPP_TEMPLATE_VIS char_traits 
{ 
    typedef _CharT    char_type; 
    typedef int       int_type; 
    typedef streamoff off_type; 
    typedef streampos pos_type; 
    typedef mbstate_t state_type; 
 
    static inline void _LIBCPP_CONSTEXPR_AFTER_CXX14 
        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_AFTER_CXX14 
    int compare(const char_type* __s1, const char_type* __s2, size_t __n); 
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14 
    size_t length(const char_type* __s); 
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14 
    const char_type* find(const char_type* __s, size_t __n, const char_type& __a); 
    static _LIBCPP_CONSTEXPR_AFTER_CXX17 
    char_type*       move(char_type* __s1, const char_type* __s2, size_t __n); 
    _LIBCPP_INLINE_VISIBILITY 
    static _LIBCPP_CONSTEXPR_AFTER_CXX17 
    char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n); 
    _LIBCPP_INLINE_VISIBILITY 
    static _LIBCPP_CONSTEXPR_AFTER_CXX17 
    char_type*       assign(char_type* __s, size_t __n, char_type __a); 
 
    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_CONSTEXPR_AFTER_CXX14 int 
char_traits<_CharT>::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; 
} 
 
template <class _CharT> 
inline 
_LIBCPP_CONSTEXPR_AFTER_CXX14 size_t 
char_traits<_CharT>::length(const char_type* __s) 
{ 
    size_t __len = 0; 
    for (; !eq(*__s, char_type(0)); ++__s) 
        ++__len; 
    return __len; 
} 
 
template <class _CharT> 
inline 
_LIBCPP_CONSTEXPR_AFTER_CXX14 const _CharT* 
char_traits<_CharT>::find(const char_type* __s, size_t __n, const char_type& __a) 
{ 
    for (; __n; --__n) 
    { 
        if (eq(*__s, __a)) 
            return __s; 
        ++__s; 
    } 
    return nullptr; 
} 
 
template <class _CharT> 
_LIBCPP_CONSTEXPR_AFTER_CXX17 _CharT* 
char_traits<_CharT>::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; 
} 
 
template <class _CharT> 
inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
_CharT* 
char_traits<_CharT>::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; 
} 
 
template <class _CharT> 
inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
_CharT* 
char_traits<_CharT>::assign(char_type* __s, size_t __n, char_type __a) 
{ 
    char_type* __r = __s; 
    for (; __n; --__n, ++__s) 
        assign(*__s, __a); 
    return __r; 
} 
 
// constexpr versions of move/copy/assign. 
 
template <class _CharT> 
static inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
_CharT* __move_constexpr(_CharT* __s1, const _CharT* __s2, size_t __n) _NOEXCEPT 
{ 
    if (__n == 0) return __s1; 
    if (__s1 < __s2) { 
      _VSTD::copy(__s2, __s2 + __n, __s1); 
    } else if (__s2 < __s1) { 
      _VSTD::copy_backward(__s2, __s2 + __n, __s1 + __n); 
    } 
    return __s1; 
} 
 
template <class _CharT> 
static inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
_CharT* __copy_constexpr(_CharT* __s1, const _CharT* __s2, size_t __n) _NOEXCEPT 
{ 
    _VSTD::copy_n(__s2, __n, __s1); 
    return __s1; 
} 
 
template <class _CharT> 
static inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
_CharT* __assign_constexpr(_CharT* __s, size_t __n, _CharT __a) _NOEXCEPT 
{ 
     _VSTD::fill_n(__s, __n, __a); 
     return __s; 
} 
 
// char_traits<char> 
 
template <> 
struct _LIBCPP_TEMPLATE_VIS char_traits<char> 
{ 
    typedef char      char_type; 
    typedef int       int_type; 
    typedef streamoff off_type; 
    typedef streampos pos_type; 
    typedef mbstate_t state_type; 
 
    static inline _LIBCPP_CONSTEXPR_AFTER_CXX14 
    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_AFTER_CXX14 
    int compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT; 
#ifdef _LIBCPP_COMPILER_MSVC 
    static inline size_t _LIBCPP_CONSTEXPR_AFTER_CXX14 length(const char_type* __s)  _NOEXCEPT
        {
            size_t __len = 0;
            for (; !eq(*__s, char_type(0)); ++__s)
                ++__len;
            return __len;
        }
#else 
    static inline size_t _LIBCPP_CONSTEXPR_AFTER_CXX14 
    length(const char_type* __s)  _NOEXCEPT {return __builtin_strlen(__s);} 
#endif 
    static _LIBCPP_CONSTEXPR_AFTER_CXX14 
    const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT; 
    static inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
    char_type* move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT 
        { 
            return __libcpp_is_constant_evaluated() 
                       ? _VSTD::__move_constexpr(__s1, __s2, __n) 
                       : __n == 0 ? __s1 : (char_type*)_VSTD::memmove(__s1, __s2, __n); 
        } 
    static inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
    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"); 
            } 
            return __libcpp_is_constant_evaluated() 
                       ? _VSTD::__copy_constexpr(__s1, __s2, __n) 
                       : __n == 0 ? __s1 : (char_type*)_VSTD::memcpy(__s1, __s2, __n); 
        } 
    static inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
    char_type* assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT 
        { 
            return __libcpp_is_constant_evaluated() 
                       ? _VSTD::__assign_constexpr(__s, __n, __a) 
                       : __n == 0 ? __s : (char_type*)_VSTD::memset(__s, to_int_type(__a), __n); 
        } 
 
    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);} 
}; 
 
inline _LIBCPP_CONSTEXPR_AFTER_CXX14 
int 
char_traits<char>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT 
{ 
    if (__n == 0) 
        return 0; 
#if __has_feature(cxx_constexpr_string_builtins) 
    return __builtin_memcmp(__s1, __s2, __n); 
#elif _LIBCPP_STD_VER <= 14 
    return _VSTD::memcmp(__s1, __s2, __n); 
#else 
    for (; __n; --__n, ++__s1, ++__s2) 
    { 
        if (lt(*__s1, *__s2)) 
            return -1; 
        if (lt(*__s2, *__s1)) 
            return 1; 
    } 
    return 0; 
#endif 
} 
 
inline _LIBCPP_CONSTEXPR_AFTER_CXX14 
const char* 
char_traits<char>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT 
{ 
    if (__n == 0) 
        return nullptr; 
#if __has_feature(cxx_constexpr_string_builtins) && !defined(__CUDACC__)
    return __builtin_char_memchr(__s, to_int_type(__a), __n); 
#elif _LIBCPP_STD_VER <= 14 
    return (const char_type*) _VSTD::memchr(__s, to_int_type(__a), __n); 
#else 
    for (; __n; --__n) 
    { 
        if (eq(*__s, __a)) 
            return __s; 
        ++__s; 
    } 
    return nullptr; 
#endif 
} 
 
 
// char_traits<wchar_t> 
 
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS 
template <> 
struct _LIBCPP_TEMPLATE_VIS char_traits<wchar_t> 
{ 
    typedef wchar_t   char_type; 
    typedef wint_t    int_type; 
    typedef streamoff off_type; 
    typedef streampos pos_type; 
    typedef mbstate_t state_type; 
 
    static inline _LIBCPP_CONSTEXPR_AFTER_CXX14 
    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_AFTER_CXX14 
    int compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT; 
    static _LIBCPP_CONSTEXPR_AFTER_CXX14 
    size_t length(const char_type* __s) _NOEXCEPT; 
    static _LIBCPP_CONSTEXPR_AFTER_CXX14 
    const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT; 
    static inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
    char_type* move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT 
        { 
            return __libcpp_is_constant_evaluated() 
                       ? _VSTD::__move_constexpr(__s1, __s2, __n) 
                       : __n == 0 ? __s1 : _VSTD::wmemmove(__s1, __s2, __n); 
        } 
    static inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
    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"); 
            } 
            return __libcpp_is_constant_evaluated() 
                       ? _VSTD::__copy_constexpr(__s1, __s2, __n) 
                       : __n == 0 ? __s1 : _VSTD::wmemcpy(__s1, __s2, __n); 
        } 
    static inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
    char_type* assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT 
        { 
            return __libcpp_is_constant_evaluated() 
                       ? _VSTD::__assign_constexpr(__s, __n, __a) 
                       : __n == 0 ? __s : _VSTD::wmemset(__s, __a, __n); 
        } 
    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);} 
}; 
 
inline _LIBCPP_CONSTEXPR_AFTER_CXX14 
int 
char_traits<wchar_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT 
{ 
    if (__n == 0) 
        return 0; 
#if __has_feature(cxx_constexpr_string_builtins) && !defined(__CUDACC__)
    return __builtin_wmemcmp(__s1, __s2, __n); 
#elif _LIBCPP_STD_VER <= 14 
    return _VSTD::wmemcmp(__s1, __s2, __n); 
#else 
    for (; __n; --__n, ++__s1, ++__s2) 
    { 
        if (lt(*__s1, *__s2)) 
            return -1; 
        if (lt(*__s2, *__s1)) 
            return 1; 
    } 
    return 0; 
#endif 
} 
 
inline _LIBCPP_CONSTEXPR_AFTER_CXX14 
size_t 
char_traits<wchar_t>::length(const char_type* __s) _NOEXCEPT 
{ 
#if __has_feature(cxx_constexpr_string_builtins) && !defined(__CUDACC__)
    return __builtin_wcslen(__s); 
#elif _LIBCPP_STD_VER <= 14 
    return _VSTD::wcslen(__s); 
#else 
    size_t __len = 0; 
    for (; !eq(*__s, char_type(0)); ++__s) 
        ++__len; 
    return __len; 
#endif 
} 
 
inline _LIBCPP_CONSTEXPR_AFTER_CXX14 
const wchar_t* 
char_traits<wchar_t>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT 
{ 
    if (__n == 0) 
        return nullptr; 
#if __has_feature(cxx_constexpr_string_builtins) && !defined(__CUDACC__)
    return __builtin_wmemchr(__s, __a, __n);
#elif _LIBCPP_STD_VER <= 14 
    return _VSTD::wmemchr(__s, __a, __n); 
#else 
    for (; __n; --__n) 
    { 
        if (eq(*__s, __a)) 
            return __s; 
        ++__s; 
    } 
    return nullptr; 
#endif 
} 
#endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS 
 
// Disable double inline warning. 
#ifdef _LIBCPP_COMPILER_MSVC 
#pragma warning ( push ) 
#pragma warning ( disable : 4141 ) 
#endif 
template <class _Traits> 
_LIBCPP_INLINE_VISIBILITY 
_LIBCPP_CONSTEXPR 
inline size_t __char_traits_length_checked(const typename _Traits::char_type* __s) _NOEXCEPT { 
#if _LIBCPP_DEBUG_LEVEL >= 1 
  return __s ? _Traits::length(__s) : (_VSTD::__libcpp_debug_function(_VSTD::__libcpp_debug_info(__FILE__, __LINE__, "p == nullptr", "null pointer pass to non-null argument of char_traits<...>::length")), 0); 
#else 
  return _Traits::length(__s); 
#endif 
} 
#ifdef _LIBCPP_COMPILER_MSVC 
#pragma warning ( pop ) 
#endif 
 
#ifndef _LIBCPP_HAS_NO_CHAR8_T 

template <>
struct _LIBCPP_TEMPLATE_VIS char_traits<char8_t>
{
    typedef char8_t        char_type;
    typedef unsigned int   int_type;
    typedef streamoff      off_type;
    typedef u8streampos    pos_type;
    typedef mbstate_t      state_type;

    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 constexpr
    int              compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;

    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_AFTER_CXX17 
    char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT 
        { 
            return __libcpp_is_constant_evaluated() 
                       ? _VSTD::__move_constexpr(__s1, __s2, __n) 
                       : __n == 0 ? __s1 : (char_type*)_VSTD::memmove(__s1, __s2, __n); 
        } 
 
    static _LIBCPP_CONSTEXPR_AFTER_CXX17 
    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"); 
            } 
            return __libcpp_is_constant_evaluated() 
                       ? _VSTD::__copy_constexpr(__s1, __s2, __n) 
                       : __n == 0 ? __s1 : (char_type*)_VSTD::memcpy(__s1, __s2, __n); 
        }
 
    static _LIBCPP_CONSTEXPR_AFTER_CXX17 
    char_type*       assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT 
        { 
            return __libcpp_is_constant_evaluated() 
                       ? _VSTD::__assign_constexpr(__s, __n, __a) 
                       : __n == 0 ? __s : (char_type*)_VSTD::memset(__s, to_int_type(__a), __n); 
        } 

    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;
}

inline constexpr
int
char_traits<char8_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
{
#if __has_feature(cxx_constexpr_string_builtins)
    return __builtin_memcmp(__s1, __s2, __n);
#else
    for (; __n; --__n, ++__s1, ++__s2)
    {
        if (lt(*__s1, *__s2))
            return -1;
        if (lt(*__s2, *__s1))
            return 1;
    }
    return 0;
#endif
}

// 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 

#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS 
 
template <> 
struct _LIBCPP_TEMPLATE_VIS char_traits<char16_t> 
{ 
    typedef char16_t       char_type; 
    typedef uint_least16_t int_type; 
    typedef streamoff      off_type; 
    typedef u16streampos   pos_type; 
    typedef mbstate_t      state_type; 
 
    static inline _LIBCPP_CONSTEXPR_AFTER_CXX14 
    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_AFTER_CXX14 
    int              compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT; 
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14 
    size_t           length(const char_type* __s) _NOEXCEPT; 
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14 
    const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT; 
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
    static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT; 
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
    static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT; 
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
    static char_type*       assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT; 
 
    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_AFTER_CXX14 
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_AFTER_CXX14 
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_AFTER_CXX14 
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; 
} 
 
inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
char16_t* 
char_traits<char16_t>::move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT 
{ 
    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; 
} 
 
inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
char16_t* 
char_traits<char16_t>::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"); 
    } 
    char_type* __r = __s1; 
    for (; __n; --__n, ++__s1, ++__s2) 
        assign(*__s1, *__s2); 
    return __r; 
} 
 
inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
char16_t* 
char_traits<char16_t>::assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT 
{ 
    char_type* __r = __s; 
    for (; __n; --__n, ++__s) 
        assign(*__s, __a); 
    return __r; 
} 
 
template <> 
struct _LIBCPP_TEMPLATE_VIS char_traits<char32_t> 
{ 
    typedef char32_t       char_type; 
    typedef uint_least32_t int_type; 
    typedef streamoff      off_type; 
    typedef u32streampos   pos_type; 
    typedef mbstate_t      state_type; 
 
    static inline _LIBCPP_CONSTEXPR_AFTER_CXX14 
    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_AFTER_CXX14 
    int              compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT; 
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14 
    size_t           length(const char_type* __s) _NOEXCEPT; 
    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14 
    const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT; 
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
    static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT; 
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
    static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT; 
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
    static char_type*       assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT; 
 
    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_AFTER_CXX14 
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_AFTER_CXX14 
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_AFTER_CXX14 
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; 
} 
 
inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
char32_t* 
char_traits<char32_t>::move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT 
{ 
    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; 
} 
 
inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
char32_t* 
char_traits<char32_t>::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"); 
    } 
    char_type* __r = __s1; 
    for (; __n; --__n, ++__s1, ++__s2) 
        assign(*__s1, *__s2); 
    return __r; 
} 
 
inline _LIBCPP_CONSTEXPR_AFTER_CXX17 
char32_t* 
char_traits<char32_t>::assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT 
{ 
    char_type* __r = __s; 
    for (; __n; --__n, ++__s) 
        assign(*__s, __a); 
    return __r; 
} 
 
#endif // _LIBCPP_HAS_NO_UNICODE_CHARS 
 
// helper fns for basic_string and string_view 
 
// __str_find 
template<class _CharT, class _SizeT, class _Traits, _SizeT __npos> 
inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _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> 
inline _LIBCPP_CONSTEXPR_AFTER_CXX11 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_AFTER_CXX11 _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 = __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_AFTER_CXX11 _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_AFTER_CXX11 _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 = _VSTD::__find_end( 
                  __p, __p + __pos, __s, __s + __n, _Traits::eq, 
                        random_access_iterator_tag(), random_access_iterator_tag()); 
    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_AFTER_CXX11 _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_AFTER_CXX11 _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_AFTER_CXX11 _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_AFTER_CXX11 _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_AFTER_CXX11 _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_AFTER_CXX11 _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)); 
} 
 
template <class _CharT, class _Iter, class _Traits=char_traits<_CharT> > 
struct __quoted_output_proxy 
{ 
    _Iter  __first; 
    _Iter  __last; 
    _CharT  __delim; 
    _CharT  __escape; 
 
    __quoted_output_proxy(_Iter __f, _Iter __l, _CharT __d, _CharT __e) 
    : __first(__f), __last(__l), __delim(__d), __escape(__e) {} 
    //  This would be a nice place for a string_ref 
}; 
 
_LIBCPP_END_NAMESPACE_STD 
 
_LIBCPP_POP_MACROS 
 
#endif // _LIBCPP___STRING