1// -*- C++ -*-
2//===--------------------------- string -----------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP_STRING
11#define _LIBCPP_STRING
12
13/*
14    string synopsis
15
16namespace std
17{
18
19template <class stateT>
20class fpos
21{
22private:
23    stateT st;
24public:
25    fpos(streamoff = streamoff());
26
27    operator streamoff() const;
28
29    stateT state() const;
30    void state(stateT);
31
32    fpos& operator+=(streamoff);
33    fpos  operator+ (streamoff) const;
34    fpos& operator-=(streamoff);
35    fpos  operator- (streamoff) const;
36};
37
38template <class stateT> streamoff operator-(const fpos<stateT>& x, const fpos<stateT>& y);
39
40template <class stateT> bool operator==(const fpos<stateT>& x, const fpos<stateT>& y);
41template <class stateT> bool operator!=(const fpos<stateT>& x, const fpos<stateT>& y);
42
43template <class charT>
44struct char_traits
45{
46    typedef charT     char_type;
47    typedef ...       int_type;
48    typedef streamoff off_type;
49    typedef streampos pos_type;
50    typedef mbstate_t state_type;
51
52    static void assign(char_type& c1, const char_type& c2) noexcept;
53    static constexpr bool eq(char_type c1, char_type c2) noexcept;
54    static constexpr bool lt(char_type c1, char_type c2) noexcept;
55
56    static int              compare(const char_type* s1, const char_type* s2, size_t n);
57    static size_t           length(const char_type* s);
58    static const char_type* find(const char_type* s, size_t n, const char_type& a);
59    static char_type*       move(char_type* s1, const char_type* s2, size_t n);
60    static char_type*       copy(char_type* s1, const char_type* s2, size_t n);
61    static char_type*       assign(char_type* s, size_t n, char_type a);
62
63    static constexpr int_type  not_eof(int_type c) noexcept;
64    static constexpr char_type to_char_type(int_type c) noexcept;
65    static constexpr int_type  to_int_type(char_type c) noexcept;
66    static constexpr bool      eq_int_type(int_type c1, int_type c2) noexcept;
67    static constexpr int_type  eof() noexcept;
68};
69
70template <> struct char_traits<char>;
71template <> struct char_traits<wchar_t>;
72
73template<class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> >
74class basic_string
75{
76public:
77// types:
78    typedef traits traits_type;
79    typedef typename traits_type::char_type value_type;
80    typedef Allocator allocator_type;
81    typedef typename allocator_type::size_type size_type;
82    typedef typename allocator_type::difference_type difference_type;
83    typedef typename allocator_type::reference reference;
84    typedef typename allocator_type::const_reference const_reference;
85    typedef typename allocator_type::pointer pointer;
86    typedef typename allocator_type::const_pointer const_pointer;
87    typedef implementation-defined iterator;
88    typedef implementation-defined const_iterator;
89    typedef std::reverse_iterator<iterator> reverse_iterator;
90    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
91
92    static const size_type npos = -1;
93
94    basic_string()
95        noexcept(is_nothrow_default_constructible<allocator_type>::value);
96    explicit basic_string(const allocator_type& a);
97    basic_string(const basic_string& str);
98    basic_string(basic_string&& str)
99        noexcept(is_nothrow_move_constructible<allocator_type>::value);
100    basic_string(const basic_string& str, size_type pos,
101                 const allocator_type& a = allocator_type());
102    basic_string(const basic_string& str, size_type pos, size_type n,
103                 const Allocator& a = Allocator());
104    template<class T>
105        basic_string(const T& t, size_type pos, size_type n, const Allocator& a = Allocator()); // C++17
106    template <class T>
107        explicit basic_string(const T& t, const Allocator& a = Allocator()); // C++17
108    basic_string(const value_type* s, const allocator_type& a = allocator_type());
109    basic_string(const value_type* s, size_type n, const allocator_type& a = allocator_type());
110    basic_string(size_type n, value_type c, const allocator_type& a = allocator_type());
111    template<class InputIterator>
112        basic_string(InputIterator begin, InputIterator end,
113                     const allocator_type& a = allocator_type());
114    basic_string(initializer_list<value_type>, const Allocator& = Allocator());
115    basic_string(const basic_string&, const Allocator&);
116    basic_string(basic_string&&, const Allocator&);
117
118    ~basic_string();
119
120    operator basic_string_view<charT, traits>() const noexcept;
121
122    basic_string& operator=(const basic_string& str);
123    template <class T>
124        basic_string& operator=(const T& t); // C++17
125    basic_string& operator=(basic_string&& str)
126        noexcept(
127             allocator_type::propagate_on_container_move_assignment::value ||
128             allocator_type::is_always_equal::value ); // C++17
129    basic_string& operator=(const value_type* s);
130    basic_string& operator=(value_type c);
131    basic_string& operator=(initializer_list<value_type>);
132
133    iterator       begin() noexcept;
134    const_iterator begin() const noexcept;
135    iterator       end() noexcept;
136    const_iterator end() const noexcept;
137
138    reverse_iterator       rbegin() noexcept;
139    const_reverse_iterator rbegin() const noexcept;
140    reverse_iterator       rend() noexcept;
141    const_reverse_iterator rend() const noexcept;
142
143    const_iterator         cbegin() const noexcept;
144    const_iterator         cend() const noexcept;
145    const_reverse_iterator crbegin() const noexcept;
146    const_reverse_iterator crend() const noexcept;
147
148    size_type size() const noexcept;
149    size_type length() const noexcept;
150    size_type max_size() const noexcept;
151    size_type capacity() const noexcept;
152
153    void resize(size_type n, value_type c);
154    void resize(size_type n);
155
156    void reserve(size_type res_arg = 0);
157    void shrink_to_fit();
158    void clear() noexcept;
159    bool empty() const noexcept;
160
161    const_reference operator[](size_type pos) const;
162    reference       operator[](size_type pos);
163
164    const_reference at(size_type n) const;
165    reference       at(size_type n);
166
167    basic_string& operator+=(const basic_string& str);
168    template <class T>
169        basic_string& operator+=(const T& t);              // C++17
170    basic_string& operator+=(const value_type* s);
171    basic_string& operator+=(value_type c);
172    basic_string& operator+=(initializer_list<value_type>);
173
174    basic_string& append(const basic_string& str);
175    template <class T>
176        basic_string& append(const T& t);                 // C++17
177    basic_string& append(const basic_string& str, size_type pos, size_type n=npos); //C++14
178    template <class T>
179        basic_string& append(const T& t, size_type pos, size_type n=npos); // C++17
180    basic_string& append(const value_type* s, size_type n);
181    basic_string& append(const value_type* s);
182    basic_string& append(size_type n, value_type c);
183    template<class InputIterator>
184        basic_string& append(InputIterator first, InputIterator last);
185    basic_string& append(initializer_list<value_type>);
186
187    void push_back(value_type c);
188    void pop_back();
189    reference       front();
190    const_reference front() const;
191    reference       back();
192    const_reference back() const;
193
194    basic_string& assign(const basic_string& str);
195    template <class T>
196        basic_string& assign(const T& t);  // C++17
197    basic_string& assign(basic_string&& str);
198    basic_string& assign(const basic_string& str, size_type pos, size_type n=npos); // C++14
199    template <class T>
200        basic_string& assign(const T& t, size_type pos, size_type n=npos); // C++17
201    basic_string& assign(const value_type* s, size_type n);
202    basic_string& assign(const value_type* s);
203    basic_string& assign(size_type n, value_type c);
204    template<class InputIterator>
205        basic_string& assign(InputIterator first, InputIterator last);
206    basic_string& assign(initializer_list<value_type>);
207
208    basic_string& insert(size_type pos1, const basic_string& str);
209    template <class T>
210        basic_string& insert(size_type pos1, const T& t);
211    basic_string& insert(size_type pos1, const basic_string& str,
212                         size_type pos2, size_type n);
213    template <class T>
214        basic_string& insert(size_type pos1, const T& t, size_type pos2, size_type n); // C++17
215    basic_string& insert(size_type pos, const value_type* s, size_type n=npos); //C++14
216    basic_string& insert(size_type pos, const value_type* s);
217    basic_string& insert(size_type pos, size_type n, value_type c);
218    iterator      insert(const_iterator p, value_type c);
219    iterator      insert(const_iterator p, size_type n, value_type c);
220    template<class InputIterator>
221        iterator insert(const_iterator p, InputIterator first, InputIterator last);
222    iterator      insert(const_iterator p, initializer_list<value_type>);
223
224    basic_string& erase(size_type pos = 0, size_type n = npos);
225    iterator      erase(const_iterator position);
226    iterator      erase(const_iterator first, const_iterator last);
227
228    basic_string& replace(size_type pos1, size_type n1, const basic_string& str);
229    template <class T>
230    basic_string& replace(size_type pos1, size_type n1, const T& t);  // C++17
231    basic_string& replace(size_type pos1, size_type n1, const basic_string& str,
232                          size_type pos2, size_type n2=npos); // C++14
233    template <class T>
234        basic_string& replace(size_type pos1, size_type n1, const T& t,
235                              size_type pos2, size_type n); // C++17
236    basic_string& replace(size_type pos, size_type n1, const value_type* s, size_type n2);
237    basic_string& replace(size_type pos, size_type n1, const value_type* s);
238    basic_string& replace(size_type pos, size_type n1, size_type n2, value_type c);
239    basic_string& replace(const_iterator i1, const_iterator i2, const basic_string& str);
240    template <class T>
241        basic_string& replace(const_iterator i1, const_iterator i2, const T& t);  // C++17
242    basic_string& replace(const_iterator i1, const_iterator i2, const value_type* s, size_type n);
243    basic_string& replace(const_iterator i1, const_iterator i2, const value_type* s);
244    basic_string& replace(const_iterator i1, const_iterator i2, size_type n, value_type c);
245    template<class InputIterator>
246        basic_string& replace(const_iterator i1, const_iterator i2, InputIterator j1, InputIterator j2);
247    basic_string& replace(const_iterator i1, const_iterator i2, initializer_list<value_type>);
248
249    size_type copy(value_type* s, size_type n, size_type pos = 0) const;
250    basic_string substr(size_type pos = 0, size_type n = npos) const;
251
252    void swap(basic_string& str)
253        noexcept(allocator_traits<allocator_type>::propagate_on_container_swap::value ||
254                 allocator_traits<allocator_type>::is_always_equal::value);  // C++17
255
256    const value_type* c_str() const noexcept;
257    const value_type* data() const noexcept;
258          value_type* data()       noexcept;   // C++17
259
260    allocator_type get_allocator() const noexcept;
261
262    size_type find(const basic_string& str, size_type pos = 0) const noexcept;
263    template <class T>
264        size_type find(const T& t, size_type pos = 0) const;  // C++17
265    size_type find(const value_type* s, size_type pos, size_type n) const noexcept;
266    size_type find(const value_type* s, size_type pos = 0) const noexcept;
267    size_type find(value_type c, size_type pos = 0) const noexcept;
268
269    size_type rfind(const basic_string& str, size_type pos = npos) const noexcept;
270    template <class T>
271        size_type rfind(const T& t, size_type pos = npos) const;  // C++17
272    size_type rfind(const value_type* s, size_type pos, size_type n) const noexcept;
273    size_type rfind(const value_type* s, size_type pos = npos) const noexcept;
274    size_type rfind(value_type c, size_type pos = npos) const noexcept;
275
276    size_type find_first_of(const basic_string& str, size_type pos = 0) const noexcept;
277    template <class T>
278        size_type find_first_of(const T& t, size_type pos = 0) const; // C++17
279    size_type find_first_of(const value_type* s, size_type pos, size_type n) const noexcept;
280    size_type find_first_of(const value_type* s, size_type pos = 0) const noexcept;
281    size_type find_first_of(value_type c, size_type pos = 0) const noexcept;
282
283    size_type find_last_of(const basic_string& str, size_type pos = npos) const noexcept;
284    template <class T>
285        size_type find_last_of(const T& t, size_type pos = npos) const noexcept;  // C++17
286    size_type find_last_of(const value_type* s, size_type pos, size_type n) const noexcept;
287    size_type find_last_of(const value_type* s, size_type pos = npos) const noexcept;
288    size_type find_last_of(value_type c, size_type pos = npos) const noexcept;
289
290    size_type find_first_not_of(const basic_string& str, size_type pos = 0) const noexcept;
291    template <class T>
292        size_type find_first_not_of(const T& t, size_type pos = 0) const; // C++17
293    size_type find_first_not_of(const value_type* s, size_type pos, size_type n) const noexcept;
294    size_type find_first_not_of(const value_type* s, size_type pos = 0) const noexcept;
295    size_type find_first_not_of(value_type c, size_type pos = 0) const noexcept;
296
297    size_type find_last_not_of(const basic_string& str, size_type pos = npos) const noexcept;
298    template <class T>
299        size_type find_last_not_of(const T& t, size_type pos = npos) const; // C++17
300    size_type find_last_not_of(const value_type* s, size_type pos, size_type n) const noexcept;
301    size_type find_last_not_of(const value_type* s, size_type pos = npos) const noexcept;
302    size_type find_last_not_of(value_type c, size_type pos = npos) const noexcept;
303
304    int compare(const basic_string& str) const noexcept;
305    template <class T>
306        int compare(const T& t) const noexcept;  // C++17
307    int compare(size_type pos1, size_type n1, const basic_string& str) const;
308    template <class T>
309        int compare(size_type pos1, size_type n1, const T& t) const;  // C++17
310    int compare(size_type pos1, size_type n1, const basic_string& str,
311                size_type pos2, size_type n2=npos) const; // C++14
312    template <class T>
313        int compare(size_type pos1, size_type n1, const T& t,
314                    size_type pos2, size_type n2=npos) const; // C++17
315    int compare(const value_type* s) const noexcept;
316    int compare(size_type pos1, size_type n1, const value_type* s) const;
317    int compare(size_type pos1, size_type n1, const value_type* s, size_type n2) const;
318
319    bool starts_with(basic_string_view<charT, traits> sv) const noexcept; // C++2a
320    bool starts_with(charT c) const noexcept;                             // C++2a
321    bool starts_with(const charT* s) const;                               // C++2a
322    bool ends_with(basic_string_view<charT, traits> sv) const noexcept;   // C++2a
323    bool ends_with(charT c) const noexcept;                               // C++2a
324    bool ends_with(const charT* s) const;                                 // C++2a
325
326    bool __invariants() const;
327};
328
329template<class InputIterator,
330         class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
331basic_string(InputIterator, InputIterator, Allocator = Allocator())
332   -> basic_string<typename iterator_traits<InputIterator>::value_type,
333                  char_traits<typename iterator_traits<InputIterator>::value_type>,
334                  Allocator>;   // C++17
335
336template<class charT, class traits, class Allocator>
337basic_string<charT, traits, Allocator>
338operator+(const basic_string<charT, traits, Allocator>& lhs,
339          const basic_string<charT, traits, Allocator>& rhs);
340
341template<class charT, class traits, class Allocator>
342basic_string<charT, traits, Allocator>
343operator+(const charT* lhs , const basic_string<charT,traits,Allocator>&rhs);
344
345template<class charT, class traits, class Allocator>
346basic_string<charT, traits, Allocator>
347operator+(charT lhs, const basic_string<charT,traits,Allocator>& rhs);
348
349template<class charT, class traits, class Allocator>
350basic_string<charT, traits, Allocator>
351operator+(const basic_string<charT, traits, Allocator>& lhs, const charT* rhs);
352
353template<class charT, class traits, class Allocator>
354basic_string<charT, traits, Allocator>
355operator+(const basic_string<charT, traits, Allocator>& lhs, charT rhs);
356
357template<class charT, class traits, class Allocator>
358bool operator==(const basic_string<charT, traits, Allocator>& lhs,
359                const basic_string<charT, traits, Allocator>& rhs) noexcept;
360
361template<class charT, class traits, class Allocator>
362bool operator==(const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;
363
364template<class charT, class traits, class Allocator>
365bool operator==(const basic_string<charT,traits,Allocator>& lhs, const charT* rhs) noexcept;
366
367template<class charT, class traits, class Allocator>
368bool operator!=(const basic_string<charT,traits,Allocator>& lhs,
369                const basic_string<charT, traits, Allocator>& rhs) noexcept;
370
371template<class charT, class traits, class Allocator>
372bool operator!=(const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;
373
374template<class charT, class traits, class Allocator>
375bool operator!=(const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;
376
377template<class charT, class traits, class Allocator>
378bool operator< (const basic_string<charT, traits, Allocator>& lhs,
379                const basic_string<charT, traits, Allocator>& rhs) noexcept;
380
381template<class charT, class traits, class Allocator>
382bool operator< (const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;
383
384template<class charT, class traits, class Allocator>
385bool operator< (const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;
386
387template<class charT, class traits, class Allocator>
388bool operator> (const basic_string<charT, traits, Allocator>& lhs,
389                const basic_string<charT, traits, Allocator>& rhs) noexcept;
390
391template<class charT, class traits, class Allocator>
392bool operator> (const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;
393
394template<class charT, class traits, class Allocator>
395bool operator> (const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;
396
397template<class charT, class traits, class Allocator>
398bool operator<=(const basic_string<charT, traits, Allocator>& lhs,
399                const basic_string<charT, traits, Allocator>& rhs) noexcept;
400
401template<class charT, class traits, class Allocator>
402bool operator<=(const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;
403
404template<class charT, class traits, class Allocator>
405bool operator<=(const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;
406
407template<class charT, class traits, class Allocator>
408bool operator>=(const basic_string<charT, traits, Allocator>& lhs,
409                const basic_string<charT, traits, Allocator>& rhs) noexcept;
410
411template<class charT, class traits, class Allocator>
412bool operator>=(const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;
413
414template<class charT, class traits, class Allocator>
415bool operator>=(const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;
416
417template<class charT, class traits, class Allocator>
418void swap(basic_string<charT, traits, Allocator>& lhs,
419          basic_string<charT, traits, Allocator>& rhs)
420            noexcept(noexcept(lhs.swap(rhs)));
421
422template<class charT, class traits, class Allocator>
423basic_istream<charT, traits>&
424operator>>(basic_istream<charT, traits>& is, basic_string<charT, traits, Allocator>& str);
425
426template<class charT, class traits, class Allocator>
427basic_ostream<charT, traits>&
428operator<<(basic_ostream<charT, traits>& os, const basic_string<charT, traits, Allocator>& str);
429
430template<class charT, class traits, class Allocator>
431basic_istream<charT, traits>&
432getline(basic_istream<charT, traits>& is, basic_string<charT, traits, Allocator>& str,
433        charT delim);
434
435template<class charT, class traits, class Allocator>
436basic_istream<charT, traits>&
437getline(basic_istream<charT, traits>& is, basic_string<charT, traits, Allocator>& str);
438
439template<class charT, class traits, class Allocator, class U>
440void erase(basic_string<charT, traits, Allocator>& c, const U& value); // C++20
441template<class charT, class traits, class Allocator, class Predicate>
442void erase_if(basic_string<charT, traits, Allocator>& c, Predicate pred); // C++20
443
444typedef basic_string<char>    string;
445typedef basic_string<wchar_t> wstring;
446typedef basic_string<char16_t> u16string;
447typedef basic_string<char32_t> u32string;
448
449int                stoi  (const string& str, size_t* idx = 0, int base = 10);
450long               stol  (const string& str, size_t* idx = 0, int base = 10);
451unsigned long      stoul (const string& str, size_t* idx = 0, int base = 10);
452long long          stoll (const string& str, size_t* idx = 0, int base = 10);
453unsigned long long stoull(const string& str, size_t* idx = 0, int base = 10);
454
455float       stof (const string& str, size_t* idx = 0);
456double      stod (const string& str, size_t* idx = 0);
457long double stold(const string& str, size_t* idx = 0);
458
459string to_string(int val);
460string to_string(unsigned val);
461string to_string(long val);
462string to_string(unsigned long val);
463string to_string(long long val);
464string to_string(unsigned long long val);
465string to_string(float val);
466string to_string(double val);
467string to_string(long double val);
468
469int                stoi  (const wstring& str, size_t* idx = 0, int base = 10);
470long               stol  (const wstring& str, size_t* idx = 0, int base = 10);
471unsigned long      stoul (const wstring& str, size_t* idx = 0, int base = 10);
472long long          stoll (const wstring& str, size_t* idx = 0, int base = 10);
473unsigned long long stoull(const wstring& str, size_t* idx = 0, int base = 10);
474
475float       stof (const wstring& str, size_t* idx = 0);
476double      stod (const wstring& str, size_t* idx = 0);
477long double stold(const wstring& str, size_t* idx = 0);
478
479wstring to_wstring(int val);
480wstring to_wstring(unsigned val);
481wstring to_wstring(long val);
482wstring to_wstring(unsigned long val);
483wstring to_wstring(long long val);
484wstring to_wstring(unsigned long long val);
485wstring to_wstring(float val);
486wstring to_wstring(double val);
487wstring to_wstring(long double val);
488
489template <> struct hash<string>;
490template <> struct hash<u16string>;
491template <> struct hash<u32string>;
492template <> struct hash<wstring>;
493
494basic_string<char>     operator "" s( const char *str,     size_t len ); // C++14
495basic_string<wchar_t>  operator "" s( const wchar_t *str,  size_t len ); // C++14
496basic_string<char16_t> operator "" s( const char16_t *str, size_t len ); // C++14
497basic_string<char32_t> operator "" s( const char32_t *str, size_t len ); // C++14
498
499}  // std
500
501*/
502
503#include <__config>
504#include <string_view>
505#include <iosfwd>
506#include <cstring>
507#include <cstdio>  // For EOF.
508#include <cwchar>
509#include <algorithm>
510#include <iterator>
511#include <utility>
512#include <memory>
513#include <stdexcept>
514#include <type_traits>
515#include <initializer_list>
516#include <__functional_base>
517#include <version>
518#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
519#include <cstdint>
520#endif
521
522#include <__debug>
523
524#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
525#pragma GCC system_header
526#endif
527
528_LIBCPP_PUSH_MACROS
529#include <__undef_macros>
530
531
532_LIBCPP_BEGIN_NAMESPACE_STD
533
534// fpos
535
536template <class _StateT>
537class _LIBCPP_TEMPLATE_VIS fpos
538{
539private:
540    _StateT __st_;
541    streamoff __off_;
542public:
543    _LIBCPP_INLINE_VISIBILITY fpos(streamoff __off = streamoff()) : __st_(), __off_(__off) {}
544
545    _LIBCPP_INLINE_VISIBILITY operator streamoff() const {return __off_;}
546
547    _LIBCPP_INLINE_VISIBILITY _StateT state() const {return __st_;}
548    _LIBCPP_INLINE_VISIBILITY void state(_StateT __st) {__st_ = __st;}
549
550    _LIBCPP_INLINE_VISIBILITY fpos& operator+=(streamoff __off) {__off_ += __off; return *this;}
551    _LIBCPP_INLINE_VISIBILITY fpos  operator+ (streamoff __off) const {fpos __t(*this); __t += __off; return __t;}
552    _LIBCPP_INLINE_VISIBILITY fpos& operator-=(streamoff __off) {__off_ -= __off; return *this;}
553    _LIBCPP_INLINE_VISIBILITY fpos  operator- (streamoff __off) const {fpos __t(*this); __t -= __off; return __t;}
554};
555
556template <class _StateT>
557inline _LIBCPP_INLINE_VISIBILITY
558streamoff operator-(const fpos<_StateT>& __x, const fpos<_StateT>& __y)
559    {return streamoff(__x) - streamoff(__y);}
560
561template <class _StateT>
562inline _LIBCPP_INLINE_VISIBILITY
563bool operator==(const fpos<_StateT>& __x, const fpos<_StateT>& __y)
564    {return streamoff(__x) == streamoff(__y);}
565
566template <class _StateT>
567inline _LIBCPP_INLINE_VISIBILITY
568bool operator!=(const fpos<_StateT>& __x, const fpos<_StateT>& __y)
569    {return streamoff(__x) != streamoff(__y);}
570
571// basic_string
572
573template<class _CharT, class _Traits, class _Allocator>
574basic_string<_CharT, _Traits, _Allocator>
575operator+(const basic_string<_CharT, _Traits, _Allocator>& __x,
576          const basic_string<_CharT, _Traits, _Allocator>& __y);
577
578template<class _CharT, class _Traits, class _Allocator>
579basic_string<_CharT, _Traits, _Allocator>
580operator+(const _CharT* __x, const basic_string<_CharT,_Traits,_Allocator>& __y);
581
582template<class _CharT, class _Traits, class _Allocator>
583basic_string<_CharT, _Traits, _Allocator>
584operator+(_CharT __x, const basic_string<_CharT,_Traits,_Allocator>& __y);
585
586template<class _CharT, class _Traits, class _Allocator>
587inline _LIBCPP_INLINE_VISIBILITY
588basic_string<_CharT, _Traits, _Allocator>
589operator+(const basic_string<_CharT, _Traits, _Allocator>& __x, const _CharT* __y);
590
591template<class _CharT, class _Traits, class _Allocator>
592basic_string<_CharT, _Traits, _Allocator>
593operator+(const basic_string<_CharT, _Traits, _Allocator>& __x, _CharT __y);
594
595_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS string operator+<char, char_traits<char>, allocator<char> >(char const*, string const&))
596
597template <bool>
598class _LIBCPP_TEMPLATE_VIS __basic_string_common
599{
600protected:
601    _LIBCPP_NORETURN void __throw_length_error() const;
602    _LIBCPP_NORETURN void __throw_out_of_range() const;
603};
604
605template <bool __b>
606void
607__basic_string_common<__b>::__throw_length_error() const
608{
609    _VSTD::__throw_length_error("basic_string");
610}
611
612template <bool __b>
613void
614__basic_string_common<__b>::__throw_out_of_range() const
615{
616    _VSTD::__throw_out_of_range("basic_string");
617}
618
619_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __basic_string_common<true>)
620
621#ifdef _LIBCPP_NO_EXCEPTIONS
622template <class _Iter>
623struct __libcpp_string_gets_noexcept_iterator_impl : public true_type {};
624#elif defined(_LIBCPP_HAS_NO_NOEXCEPT)
625template <class _Iter>
626struct __libcpp_string_gets_noexcept_iterator_impl : public false_type {};
627#else
628template <class _Iter, bool = __is_cpp17_forward_iterator<_Iter>::value>
629struct __libcpp_string_gets_noexcept_iterator_impl : public _LIBCPP_BOOL_CONSTANT((
630    noexcept(++(declval<_Iter&>())) &&
631    is_nothrow_assignable<_Iter&, _Iter>::value &&
632    noexcept(declval<_Iter>() == declval<_Iter>()) &&
633    noexcept(*declval<_Iter>())
634)) {};
635
636template <class _Iter>
637struct __libcpp_string_gets_noexcept_iterator_impl<_Iter, false> : public false_type {};
638#endif
639
640
641template <class _Iter>
642struct __libcpp_string_gets_noexcept_iterator
643    : public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value || __libcpp_string_gets_noexcept_iterator_impl<_Iter>::value) {};
644
645template <class _CharT, class _Traits, class _Tp>
646struct __can_be_converted_to_string_view : public _LIBCPP_BOOL_CONSTANT(
647    ( is_convertible<const _Tp&, basic_string_view<_CharT, _Traits> >::value &&
648     !is_convertible<const _Tp&, const _CharT*>::value)) {};
649
650#ifdef _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
651
652template <class _CharT, size_t = sizeof(_CharT)>
653struct __padding
654{
655    unsigned char __xx[sizeof(_CharT)-1];
656};
657
658template <class _CharT>
659struct __padding<_CharT, 1>
660{
661};
662
663#endif  // _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
664
665template<class _CharT, class _Traits, class _Allocator>
666class _LIBCPP_TEMPLATE_VIS basic_string
667    : private __basic_string_common<true>
668{
669public:
670    typedef basic_string                                 __self;
671    typedef basic_string_view<_CharT, _Traits>           __self_view;
672    typedef _Traits                                      traits_type;
673    typedef _CharT                                       value_type;
674    typedef _Allocator                                   allocator_type;
675    typedef allocator_traits<allocator_type>             __alloc_traits;
676    typedef typename __alloc_traits::size_type           size_type;
677    typedef typename __alloc_traits::difference_type     difference_type;
678    typedef value_type&                                  reference;
679    typedef const value_type&                            const_reference;
680    typedef typename __alloc_traits::pointer             pointer;
681    typedef typename __alloc_traits::const_pointer       const_pointer;
682
683    static_assert((!is_array<value_type>::value), "Character type of basic_string must not be an array");
684    static_assert(( is_standard_layout<value_type>::value), "Character type of basic_string must be standard-layout");
685    static_assert(( is_trivial<value_type>::value), "Character type of basic_string must be trivial");
686    static_assert(( is_same<_CharT, typename traits_type::char_type>::value),
687                  "traits_type::char_type must be the same type as CharT");
688    static_assert(( is_same<typename allocator_type::value_type, value_type>::value),
689                  "Allocator::value_type must be same type as value_type");
690
691#if defined(_LIBCPP_RAW_ITERATORS)
692    typedef pointer                                      iterator;
693    typedef const_pointer                                const_iterator;
694#else  // defined(_LIBCPP_RAW_ITERATORS)
695    typedef __wrap_iter<pointer>                         iterator;
696    typedef __wrap_iter<const_pointer>                   const_iterator;
697#endif  // defined(_LIBCPP_RAW_ITERATORS)
698    typedef _VSTD::reverse_iterator<iterator>             reverse_iterator;
699    typedef _VSTD::reverse_iterator<const_iterator>       const_reverse_iterator;
700
701private:
702
703#ifdef _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
704
705    struct __long
706    {
707        pointer   __data_;
708        size_type __size_;
709        size_type __cap_;
710    };
711
712#ifdef _LIBCPP_BIG_ENDIAN
713    static const size_type __short_mask = 0x01;
714    static const size_type __long_mask  = 0x1ul;
715#else  // _LIBCPP_BIG_ENDIAN
716    static const size_type __short_mask = 0x80;
717    static const size_type __long_mask  = ~(size_type(~0) >> 1);
718#endif  // _LIBCPP_BIG_ENDIAN
719
720    enum {__min_cap = (sizeof(__long) - 1)/sizeof(value_type) > 2 ?
721                      (sizeof(__long) - 1)/sizeof(value_type) : 2};
722
723    struct __short
724    {
725        value_type __data_[__min_cap];
726        struct
727            : __padding<value_type>
728        {
729            unsigned char __size_;
730        };
731    };
732
733#else
734
735    struct __long
736    {
737        size_type __cap_;
738        size_type __size_;
739        pointer   __data_;
740    };
741
742#ifdef _LIBCPP_BIG_ENDIAN
743    static const size_type __short_mask = 0x80;
744    static const size_type __long_mask  = ~(size_type(~0) >> 1);
745#else  // _LIBCPP_BIG_ENDIAN
746    static const size_type __short_mask = 0x01;
747    static const size_type __long_mask  = 0x1ul;
748#endif  // _LIBCPP_BIG_ENDIAN
749
750    enum {__min_cap = (sizeof(__long) - 1)/sizeof(value_type) > 2 ?
751                      (sizeof(__long) - 1)/sizeof(value_type) : 2};
752
753    struct __short
754    {
755        union
756        {
757            unsigned char __size_;
758            value_type __lx;
759        };
760        value_type __data_[__min_cap];
761    };
762
763#endif  // _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
764
765    union __ulx{__long __lx; __short __lxx;};
766
767    enum {__n_words = sizeof(__ulx) / sizeof(size_type)};
768
769    struct __raw
770    {
771        size_type __words[__n_words];
772    };
773
774    struct __rep
775    {
776        union
777        {
778            __long  __l;
779            __short __s;
780            __raw   __r;
781        };
782    };
783
784    __compressed_pair<__rep, allocator_type> __r_;
785
786public:
787    static const size_type npos = -1;
788
789    _LIBCPP_INLINE_VISIBILITY basic_string()
790        _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value);
791
792    _LIBCPP_INLINE_VISIBILITY explicit basic_string(const allocator_type& __a)
793#if _LIBCPP_STD_VER <= 14
794        _NOEXCEPT_(is_nothrow_copy_constructible<allocator_type>::value);
795#else
796        _NOEXCEPT;
797#endif
798
799    basic_string(const basic_string& __str);
800    basic_string(const basic_string& __str, const allocator_type& __a);
801
802#ifndef _LIBCPP_CXX03_LANG
803    _LIBCPP_INLINE_VISIBILITY
804    basic_string(basic_string&& __str)
805#if _LIBCPP_STD_VER <= 14
806        _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value);
807#else
808        _NOEXCEPT;
809#endif
810
811    _LIBCPP_INLINE_VISIBILITY
812    basic_string(basic_string&& __str, const allocator_type& __a);
813#endif  // _LIBCPP_CXX03_LANG
814
815    template <class = typename enable_if<__is_allocator<_Allocator>::value, nullptr_t>::type>
816    _LIBCPP_INLINE_VISIBILITY
817    basic_string(const _CharT* __s) : __r_(__default_init_tag(), __default_init_tag()) {
818      _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*) detected nullptr");
819      __init(__s, traits_type::length(__s));
820#   if _LIBCPP_DEBUG_LEVEL >= 2
821      __get_db()->__insert_c(this);
822#   endif
823    }
824
825    template <class = typename enable_if<__is_allocator<_Allocator>::value, nullptr_t>::type>
826        _LIBCPP_INLINE_VISIBILITY
827        basic_string(const _CharT* __s, const _Allocator& __a);
828
829    _LIBCPP_INLINE_VISIBILITY
830    basic_string(const _CharT* __s, size_type __n);
831    _LIBCPP_INLINE_VISIBILITY
832    basic_string(const _CharT* __s, size_type __n, const _Allocator& __a);
833    _LIBCPP_INLINE_VISIBILITY
834    basic_string(size_type __n, _CharT __c);
835
836    template <class = typename enable_if<__is_allocator<_Allocator>::value, nullptr_t>::type>
837        _LIBCPP_INLINE_VISIBILITY
838        basic_string(size_type __n, _CharT __c, const _Allocator& __a);
839
840    basic_string(const basic_string& __str, size_type __pos, size_type __n,
841                 const _Allocator& __a = _Allocator());
842    _LIBCPP_INLINE_VISIBILITY
843    basic_string(const basic_string& __str, size_type __pos,
844                 const _Allocator& __a = _Allocator());
845
846    template<class _Tp, class = typename enable_if<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value, void>::type>
847        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
848        basic_string(const _Tp& __t, size_type __pos, size_type __n,
849                              const allocator_type& __a = allocator_type());
850
851    template<class _Tp, class = typename enable_if<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value, void>::type>
852        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
853        explicit basic_string(const _Tp& __t);
854
855    template<class _Tp, class = typename enable_if<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value, void>::type>
856        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
857        explicit basic_string(const _Tp& __t, const allocator_type& __a);
858
859    template<class _InputIterator, class = typename enable_if<__is_cpp17_input_iterator<_InputIterator>::value>::type>
860        _LIBCPP_INLINE_VISIBILITY
861        basic_string(_InputIterator __first, _InputIterator __last);
862    template<class _InputIterator, class = typename enable_if<__is_cpp17_input_iterator<_InputIterator>::value>::type>
863        _LIBCPP_INLINE_VISIBILITY
864        basic_string(_InputIterator __first, _InputIterator __last, const allocator_type& __a);
865#ifndef _LIBCPP_CXX03_LANG
866    _LIBCPP_INLINE_VISIBILITY
867    basic_string(initializer_list<_CharT> __il);
868    _LIBCPP_INLINE_VISIBILITY
869    basic_string(initializer_list<_CharT> __il, const _Allocator& __a);
870#endif  // _LIBCPP_CXX03_LANG
871
872    inline ~basic_string();
873
874    _LIBCPP_INLINE_VISIBILITY
875    operator __self_view() const _NOEXCEPT { return __self_view(data(), size()); }
876
877    basic_string& operator=(const basic_string& __str);
878
879    template <class _Tp, class = typename enable_if<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value, void>::type>
880    basic_string& operator=(const _Tp& __t)
881        {__self_view __sv = __t; return assign(__sv);}
882
883#ifndef _LIBCPP_CXX03_LANG
884    _LIBCPP_INLINE_VISIBILITY
885    basic_string& operator=(basic_string&& __str)
886        _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value));
887     _LIBCPP_INLINE_VISIBILITY
888    basic_string& operator=(initializer_list<value_type> __il) {return assign(__il.begin(), __il.size());}
889#endif
890    _LIBCPP_INLINE_VISIBILITY basic_string& operator=(const value_type* __s) {return assign(__s);}
891    basic_string& operator=(value_type __c);
892
893#if _LIBCPP_DEBUG_LEVEL >= 2
894    _LIBCPP_INLINE_VISIBILITY
895    iterator begin() _NOEXCEPT
896        {return iterator(this, __get_pointer());}
897    _LIBCPP_INLINE_VISIBILITY
898    const_iterator begin() const _NOEXCEPT
899        {return const_iterator(this, __get_pointer());}
900    _LIBCPP_INLINE_VISIBILITY
901    iterator end() _NOEXCEPT
902        {return iterator(this, __get_pointer() + size());}
903    _LIBCPP_INLINE_VISIBILITY
904    const_iterator end() const _NOEXCEPT
905        {return const_iterator(this, __get_pointer() + size());}
906#else
907    _LIBCPP_INLINE_VISIBILITY
908    iterator begin() _NOEXCEPT
909        {return iterator(__get_pointer());}
910    _LIBCPP_INLINE_VISIBILITY
911    const_iterator begin() const _NOEXCEPT
912        {return const_iterator(__get_pointer());}
913    _LIBCPP_INLINE_VISIBILITY
914    iterator end() _NOEXCEPT
915        {return iterator(__get_pointer() + size());}
916    _LIBCPP_INLINE_VISIBILITY
917    const_iterator end() const _NOEXCEPT
918        {return const_iterator(__get_pointer() + size());}
919#endif  // _LIBCPP_DEBUG_LEVEL >= 2
920    _LIBCPP_INLINE_VISIBILITY
921    reverse_iterator rbegin() _NOEXCEPT
922        {return reverse_iterator(end());}
923    _LIBCPP_INLINE_VISIBILITY
924    const_reverse_iterator rbegin() const _NOEXCEPT
925        {return const_reverse_iterator(end());}
926    _LIBCPP_INLINE_VISIBILITY
927    reverse_iterator rend() _NOEXCEPT
928        {return reverse_iterator(begin());}
929    _LIBCPP_INLINE_VISIBILITY
930    const_reverse_iterator rend() const _NOEXCEPT
931        {return const_reverse_iterator(begin());}
932
933    _LIBCPP_INLINE_VISIBILITY
934    const_iterator cbegin() const _NOEXCEPT
935        {return begin();}
936    _LIBCPP_INLINE_VISIBILITY
937    const_iterator cend() const _NOEXCEPT
938        {return end();}
939    _LIBCPP_INLINE_VISIBILITY
940    const_reverse_iterator crbegin() const _NOEXCEPT
941        {return rbegin();}
942    _LIBCPP_INLINE_VISIBILITY
943    const_reverse_iterator crend() const _NOEXCEPT
944        {return rend();}
945
946    _LIBCPP_INLINE_VISIBILITY size_type size() const _NOEXCEPT
947        {return __is_long() ? __get_long_size() : __get_short_size();}
948    _LIBCPP_INLINE_VISIBILITY size_type length() const _NOEXCEPT {return size();}
949    _LIBCPP_INLINE_VISIBILITY size_type max_size() const _NOEXCEPT;
950    _LIBCPP_INLINE_VISIBILITY size_type capacity() const _NOEXCEPT
951        {return (__is_long() ? __get_long_cap()
952                             : static_cast<size_type>(__min_cap)) - 1;}
953
954    void resize(size_type __n, value_type __c);
955    _LIBCPP_INLINE_VISIBILITY void resize(size_type __n) {resize(__n, value_type());}
956
957    void reserve(size_type __res_arg);
958    _LIBCPP_INLINE_VISIBILITY void __resize_default_init(size_type __n);
959
960    _LIBCPP_INLINE_VISIBILITY
961    void reserve() _NOEXCEPT {reserve(0);}
962    _LIBCPP_INLINE_VISIBILITY
963    void shrink_to_fit() _NOEXCEPT {reserve();}
964    _LIBCPP_INLINE_VISIBILITY
965    void clear() _NOEXCEPT;
966    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
967    bool empty() const _NOEXCEPT {return size() == 0;}
968
969    _LIBCPP_INLINE_VISIBILITY const_reference operator[](size_type __pos) const _NOEXCEPT;
970    _LIBCPP_INLINE_VISIBILITY reference       operator[](size_type __pos)       _NOEXCEPT;
971
972    const_reference at(size_type __n) const;
973    reference       at(size_type __n);
974
975    _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(const basic_string& __str) {return append(__str);}
976
977    template <class _Tp>
978    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
979    typename enable_if
980        <
981            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
982            basic_string&
983        >::type
984                                            operator+=(const _Tp& __t)            {__self_view __sv = __t; return append(__sv);}
985    _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(const value_type* __s)     {return append(__s);}
986    _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(value_type __c)            {push_back(__c); return *this;}
987#ifndef _LIBCPP_CXX03_LANG
988    _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(initializer_list<value_type> __il) {return append(__il);}
989#endif  // _LIBCPP_CXX03_LANG
990
991    _LIBCPP_INLINE_VISIBILITY
992    basic_string& append(const basic_string& __str);
993
994    template <class _Tp>
995    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
996    typename enable_if
997        <
998            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
999            basic_string&
1000        >::type
1001                  append(const _Tp& __t) { __self_view __sv = __t; return append(__sv.data(), __sv.size()); }
1002    basic_string& append(const basic_string& __str, size_type __pos, size_type __n=npos);
1003
1004    template <class _Tp>
1005    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1006    typename enable_if
1007        <
1008            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1009            basic_string&
1010        >::type
1011                  append(const _Tp& __t, size_type __pos, size_type __n=npos);
1012    basic_string& append(const value_type* __s, size_type __n);
1013    basic_string& append(const value_type* __s);
1014    basic_string& append(size_type __n, value_type __c);
1015
1016    _LIBCPP_INLINE_VISIBILITY
1017    void __append_default_init(size_type __n);
1018
1019    template <class _ForwardIterator>
1020    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1021    basic_string& __append_forward_unsafe(_ForwardIterator, _ForwardIterator);
1022    template<class _InputIterator>
1023    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1024    typename enable_if
1025        <
1026            __is_exactly_cpp17_input_iterator<_InputIterator>::value
1027                || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
1028            basic_string&
1029        >::type
1030    _LIBCPP_INLINE_VISIBILITY
1031    append(_InputIterator __first, _InputIterator __last) {
1032      const basic_string __temp (__first, __last, __alloc());
1033      append(__temp.data(), __temp.size());
1034      return *this;
1035    }
1036    template<class _ForwardIterator>
1037    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1038    typename enable_if
1039        <
1040            __is_cpp17_forward_iterator<_ForwardIterator>::value
1041                && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
1042            basic_string&
1043        >::type
1044    _LIBCPP_INLINE_VISIBILITY
1045    append(_ForwardIterator __first, _ForwardIterator __last) {
1046      return __append_forward_unsafe(__first, __last);
1047    }
1048
1049#ifndef _LIBCPP_CXX03_LANG
1050    _LIBCPP_INLINE_VISIBILITY
1051    basic_string& append(initializer_list<value_type> __il) {return append(__il.begin(), __il.size());}
1052#endif  // _LIBCPP_CXX03_LANG
1053
1054    void push_back(value_type __c);
1055    _LIBCPP_INLINE_VISIBILITY
1056    void pop_back();
1057    _LIBCPP_INLINE_VISIBILITY reference       front() _NOEXCEPT;
1058    _LIBCPP_INLINE_VISIBILITY const_reference front() const _NOEXCEPT;
1059    _LIBCPP_INLINE_VISIBILITY reference       back() _NOEXCEPT;
1060    _LIBCPP_INLINE_VISIBILITY const_reference back() const _NOEXCEPT;
1061
1062    template <class _Tp>
1063    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1064    typename enable_if
1065        <
1066            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1067            basic_string&
1068        >::type
1069                 assign(const _Tp & __t) { __self_view __sv = __t; return assign(__sv.data(), __sv.size()); }
1070    _LIBCPP_INLINE_VISIBILITY
1071    basic_string& assign(const basic_string& __str) { return *this = __str; }
1072#ifndef _LIBCPP_CXX03_LANG
1073    _LIBCPP_INLINE_VISIBILITY
1074    basic_string& assign(basic_string&& __str)
1075        _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value))
1076        {*this = _VSTD::move(__str); return *this;}
1077#endif
1078    basic_string& assign(const basic_string& __str, size_type __pos, size_type __n=npos);
1079    template <class _Tp>
1080    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1081    typename enable_if
1082        <
1083            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1084            basic_string&
1085        >::type
1086                  assign(const _Tp & __t, size_type __pos, size_type __n=npos);
1087    basic_string& assign(const value_type* __s, size_type __n);
1088    basic_string& assign(const value_type* __s);
1089    basic_string& assign(size_type __n, value_type __c);
1090    template<class _InputIterator>
1091    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1092    typename enable_if
1093        <
1094           __is_exactly_cpp17_input_iterator<_InputIterator>::value
1095                || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
1096            basic_string&
1097        >::type
1098        assign(_InputIterator __first, _InputIterator __last);
1099    template<class _ForwardIterator>
1100    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1101    typename enable_if
1102        <
1103            __is_cpp17_forward_iterator<_ForwardIterator>::value
1104                 && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
1105            basic_string&
1106        >::type
1107        assign(_ForwardIterator __first, _ForwardIterator __last);
1108#ifndef _LIBCPP_CXX03_LANG
1109    _LIBCPP_INLINE_VISIBILITY
1110    basic_string& assign(initializer_list<value_type> __il) {return assign(__il.begin(), __il.size());}
1111#endif  // _LIBCPP_CXX03_LANG
1112
1113    _LIBCPP_INLINE_VISIBILITY
1114    basic_string& insert(size_type __pos1, const basic_string& __str);
1115
1116    template <class _Tp>
1117    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1118    typename enable_if
1119        <
1120            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1121            basic_string&
1122        >::type
1123                 insert(size_type __pos1, const _Tp& __t)
1124    { __self_view __sv = __t; return insert(__pos1, __sv.data(), __sv.size()); }
1125
1126    template <class _Tp>
1127    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1128    typename enable_if
1129        <
1130            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1131            basic_string&
1132        >::type
1133                  insert(size_type __pos1, const _Tp& __t, size_type __pos2, size_type __n=npos);
1134    basic_string& insert(size_type __pos1, const basic_string& __str, size_type __pos2, size_type __n=npos);
1135    basic_string& insert(size_type __pos, const value_type* __s, size_type __n);
1136    basic_string& insert(size_type __pos, const value_type* __s);
1137    basic_string& insert(size_type __pos, size_type __n, value_type __c);
1138    iterator      insert(const_iterator __pos, value_type __c);
1139    _LIBCPP_INLINE_VISIBILITY
1140    iterator      insert(const_iterator __pos, size_type __n, value_type __c);
1141    template<class _InputIterator>
1142    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1143    typename enable_if
1144        <
1145           __is_exactly_cpp17_input_iterator<_InputIterator>::value
1146                || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
1147            iterator
1148        >::type
1149        insert(const_iterator __pos, _InputIterator __first, _InputIterator __last);
1150    template<class _ForwardIterator>
1151    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1152    typename enable_if
1153        <
1154            __is_cpp17_forward_iterator<_ForwardIterator>::value
1155                 && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
1156            iterator
1157        >::type
1158        insert(const_iterator __pos, _ForwardIterator __first, _ForwardIterator __last);
1159#ifndef _LIBCPP_CXX03_LANG
1160    _LIBCPP_INLINE_VISIBILITY
1161    iterator insert(const_iterator __pos, initializer_list<value_type> __il)
1162                    {return insert(__pos, __il.begin(), __il.end());}
1163#endif  // _LIBCPP_CXX03_LANG
1164
1165    basic_string& erase(size_type __pos = 0, size_type __n = npos);
1166    _LIBCPP_INLINE_VISIBILITY
1167    iterator      erase(const_iterator __pos);
1168    _LIBCPP_INLINE_VISIBILITY
1169    iterator      erase(const_iterator __first, const_iterator __last);
1170
1171    _LIBCPP_INLINE_VISIBILITY
1172    basic_string& replace(size_type __pos1, size_type __n1, const basic_string& __str);
1173
1174    template <class _Tp>
1175    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1176    typename enable_if
1177        <
1178            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1179            basic_string&
1180        >::type
1181                  replace(size_type __pos1, size_type __n1, const _Tp& __t) { __self_view __sv = __t; return replace(__pos1, __n1, __sv.data(), __sv.size()); }
1182    basic_string& replace(size_type __pos1, size_type __n1, const basic_string& __str, size_type __pos2, size_type __n2=npos);
1183    template <class _Tp>
1184    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1185    typename enable_if
1186        <
1187            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1188            basic_string&
1189        >::type
1190                  replace(size_type __pos1, size_type __n1, const _Tp& __t, size_type __pos2, size_type __n2=npos);
1191    basic_string& replace(size_type __pos, size_type __n1, const value_type* __s, size_type __n2);
1192    basic_string& replace(size_type __pos, size_type __n1, const value_type* __s);
1193    basic_string& replace(size_type __pos, size_type __n1, size_type __n2, value_type __c);
1194    _LIBCPP_INLINE_VISIBILITY
1195    basic_string& replace(const_iterator __i1, const_iterator __i2, const basic_string& __str);
1196
1197    template <class _Tp>
1198    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1199    typename enable_if
1200        <
1201            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1202            basic_string&
1203        >::type
1204                  replace(const_iterator __i1, const_iterator __i2, const _Tp& __t) { __self_view __sv = __t; return replace(__i1 - begin(), __i2 - __i1, __sv); }
1205
1206    _LIBCPP_INLINE_VISIBILITY
1207    basic_string& replace(const_iterator __i1, const_iterator __i2, const value_type* __s, size_type __n);
1208    _LIBCPP_INLINE_VISIBILITY
1209    basic_string& replace(const_iterator __i1, const_iterator __i2, const value_type* __s);
1210    _LIBCPP_INLINE_VISIBILITY
1211    basic_string& replace(const_iterator __i1, const_iterator __i2, size_type __n, value_type __c);
1212    template<class _InputIterator>
1213    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1214    typename enable_if
1215        <
1216            __is_cpp17_input_iterator<_InputIterator>::value,
1217            basic_string&
1218        >::type
1219        replace(const_iterator __i1, const_iterator __i2, _InputIterator __j1, _InputIterator __j2);
1220#ifndef _LIBCPP_CXX03_LANG
1221    _LIBCPP_INLINE_VISIBILITY
1222    basic_string& replace(const_iterator __i1, const_iterator __i2, initializer_list<value_type> __il)
1223        {return replace(__i1, __i2, __il.begin(), __il.end());}
1224#endif  // _LIBCPP_CXX03_LANG
1225
1226    size_type copy(value_type* __s, size_type __n, size_type __pos = 0) const;
1227    _LIBCPP_INLINE_VISIBILITY
1228    basic_string substr(size_type __pos = 0, size_type __n = npos) const;
1229
1230    _LIBCPP_INLINE_VISIBILITY
1231    void swap(basic_string& __str)
1232#if _LIBCPP_STD_VER >= 14
1233        _NOEXCEPT;
1234#else
1235        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value ||
1236                    __is_nothrow_swappable<allocator_type>::value);
1237#endif
1238
1239    _LIBCPP_INLINE_VISIBILITY
1240    const value_type* c_str() const _NOEXCEPT {return data();}
1241    _LIBCPP_INLINE_VISIBILITY
1242    const value_type* data() const _NOEXCEPT  {return _VSTD::__to_address(__get_pointer());}
1243#if _LIBCPP_STD_VER > 14 || defined(_LIBCPP_BUILDING_LIBRARY)
1244    _LIBCPP_INLINE_VISIBILITY
1245    value_type* data()             _NOEXCEPT  {return _VSTD::__to_address(__get_pointer());}
1246#endif
1247
1248    _LIBCPP_INLINE_VISIBILITY
1249    allocator_type get_allocator() const _NOEXCEPT {return __alloc();}
1250
1251    _LIBCPP_INLINE_VISIBILITY
1252    size_type find(const basic_string& __str, size_type __pos = 0) const _NOEXCEPT;
1253
1254    template <class _Tp>
1255    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1256    typename enable_if
1257        <
1258            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1259            size_type
1260        >::type
1261              find(const _Tp& __t, size_type __pos = 0) const;
1262    size_type find(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
1263    _LIBCPP_INLINE_VISIBILITY
1264    size_type find(const value_type* __s, size_type __pos = 0) const _NOEXCEPT;
1265    size_type find(value_type __c, size_type __pos = 0) const _NOEXCEPT;
1266
1267    _LIBCPP_INLINE_VISIBILITY
1268    size_type rfind(const basic_string& __str, size_type __pos = npos) const _NOEXCEPT;
1269
1270    template <class _Tp>
1271    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1272    typename enable_if
1273        <
1274            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1275            size_type
1276        >::type
1277              rfind(const _Tp& __t, size_type __pos = npos) const;
1278    size_type rfind(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
1279    _LIBCPP_INLINE_VISIBILITY
1280    size_type rfind(const value_type* __s, size_type __pos = npos) const _NOEXCEPT;
1281    size_type rfind(value_type __c, size_type __pos = npos) const _NOEXCEPT;
1282
1283    _LIBCPP_INLINE_VISIBILITY
1284    size_type find_first_of(const basic_string& __str, size_type __pos = 0) const _NOEXCEPT;
1285
1286    template <class _Tp>
1287    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1288    typename enable_if
1289        <
1290            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1291            size_type
1292        >::type
1293              find_first_of(const _Tp& __t, size_type __pos = 0) const;
1294    size_type find_first_of(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
1295    _LIBCPP_INLINE_VISIBILITY
1296    size_type find_first_of(const value_type* __s, size_type __pos = 0) const _NOEXCEPT;
1297    _LIBCPP_INLINE_VISIBILITY
1298    size_type find_first_of(value_type __c, size_type __pos = 0) const _NOEXCEPT;
1299
1300    _LIBCPP_INLINE_VISIBILITY
1301    size_type find_last_of(const basic_string& __str, size_type __pos = npos) const _NOEXCEPT;
1302
1303    template <class _Tp>
1304    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1305    typename enable_if
1306        <
1307            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1308            size_type
1309        >::type
1310              find_last_of(const _Tp& __t, size_type __pos = npos) const;
1311    size_type find_last_of(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
1312    _LIBCPP_INLINE_VISIBILITY
1313    size_type find_last_of(const value_type* __s, size_type __pos = npos) const _NOEXCEPT;
1314    _LIBCPP_INLINE_VISIBILITY
1315    size_type find_last_of(value_type __c, size_type __pos = npos) const _NOEXCEPT;
1316
1317    _LIBCPP_INLINE_VISIBILITY
1318    size_type find_first_not_of(const basic_string& __str, size_type __pos = 0) const _NOEXCEPT;
1319
1320    template <class _Tp>
1321    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1322    typename enable_if
1323        <
1324            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1325            size_type
1326        >::type
1327              find_first_not_of(const _Tp &__t, size_type __pos = 0) const;
1328    size_type find_first_not_of(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
1329    _LIBCPP_INLINE_VISIBILITY
1330    size_type find_first_not_of(const value_type* __s, size_type __pos = 0) const _NOEXCEPT;
1331    _LIBCPP_INLINE_VISIBILITY
1332    size_type find_first_not_of(value_type __c, size_type __pos = 0) const _NOEXCEPT;
1333
1334    _LIBCPP_INLINE_VISIBILITY
1335    size_type find_last_not_of(const basic_string& __str, size_type __pos = npos) const _NOEXCEPT;
1336
1337    template <class _Tp>
1338    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1339    typename enable_if
1340        <
1341            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1342            size_type
1343        >::type
1344              find_last_not_of(const _Tp& __t, size_type __pos = npos) const;
1345    size_type find_last_not_of(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
1346    _LIBCPP_INLINE_VISIBILITY
1347    size_type find_last_not_of(const value_type* __s, size_type __pos = npos) const _NOEXCEPT;
1348    _LIBCPP_INLINE_VISIBILITY
1349    size_type find_last_not_of(value_type __c, size_type __pos = npos) const _NOEXCEPT;
1350
1351    _LIBCPP_INLINE_VISIBILITY
1352    int compare(const basic_string& __str) const _NOEXCEPT;
1353
1354    template <class _Tp>
1355    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1356    typename enable_if
1357        <
1358            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1359            int
1360        >::type
1361        compare(const _Tp &__t) const;
1362
1363    template <class _Tp>
1364    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
1365    typename enable_if
1366        <
1367            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1368            int
1369        >::type
1370         compare(size_type __pos1, size_type __n1, const _Tp& __t) const;
1371
1372    _LIBCPP_INLINE_VISIBILITY
1373    int compare(size_type __pos1, size_type __n1, const basic_string& __str) const;
1374    int compare(size_type __pos1, size_type __n1, const basic_string& __str, size_type __pos2, size_type __n2=npos) const;
1375
1376    template <class _Tp>
1377    inline _LIBCPP_INLINE_VISIBILITY
1378        typename enable_if
1379        <
1380            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
1381            int
1382        >::type
1383        compare(size_type __pos1, size_type __n1, const _Tp& __t, size_type __pos2, size_type __n2=npos) const;
1384    int compare(const value_type* __s) const _NOEXCEPT;
1385    int compare(size_type __pos1, size_type __n1, const value_type* __s) const;
1386    int compare(size_type __pos1, size_type __n1, const value_type* __s, size_type __n2) const;
1387
1388#if _LIBCPP_STD_VER > 17
1389    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
1390    bool starts_with(__self_view __sv) const _NOEXCEPT
1391    { return __self_view(data(), size()).starts_with(__sv); }
1392
1393    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
1394    bool starts_with(value_type __c) const _NOEXCEPT
1395    { return !empty() && _Traits::eq(front(), __c); }
1396
1397    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
1398    bool starts_with(const value_type* __s) const _NOEXCEPT
1399    { return starts_with(__self_view(__s)); }
1400
1401    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
1402    bool ends_with(__self_view __sv) const _NOEXCEPT
1403    { return __self_view(data(), size()).ends_with( __sv); }
1404
1405    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
1406    bool ends_with(value_type __c) const _NOEXCEPT
1407    { return !empty() && _Traits::eq(back(), __c); }
1408
1409    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
1410    bool ends_with(const value_type* __s) const _NOEXCEPT
1411    { return ends_with(__self_view(__s)); }
1412#endif
1413
1414    _LIBCPP_INLINE_VISIBILITY bool __invariants() const;
1415
1416    _LIBCPP_INLINE_VISIBILITY void __clear_and_shrink() _NOEXCEPT;
1417
1418    _LIBCPP_INLINE_VISIBILITY
1419    bool __is_long() const _NOEXCEPT
1420        {return bool(__r_.first().__s.__size_ & __short_mask);}
1421
1422#if _LIBCPP_DEBUG_LEVEL >= 2
1423
1424    bool __dereferenceable(const const_iterator* __i) const;
1425    bool __decrementable(const const_iterator* __i) const;
1426    bool __addable(const const_iterator* __i, ptrdiff_t __n) const;
1427    bool __subscriptable(const const_iterator* __i, ptrdiff_t __n) const;
1428
1429#endif  // _LIBCPP_DEBUG_LEVEL >= 2
1430
1431private:
1432    _LIBCPP_INLINE_VISIBILITY
1433    allocator_type& __alloc() _NOEXCEPT
1434        {return __r_.second();}
1435    _LIBCPP_INLINE_VISIBILITY
1436    const allocator_type& __alloc() const _NOEXCEPT
1437        {return __r_.second();}
1438
1439#ifdef _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
1440
1441    _LIBCPP_INLINE_VISIBILITY
1442    void __set_short_size(size_type __s) _NOEXCEPT
1443#   ifdef _LIBCPP_BIG_ENDIAN
1444        {__r_.first().__s.__size_ = (unsigned char)(__s << 1);}
1445#   else
1446        {__r_.first().__s.__size_ = (unsigned char)(__s);}
1447#   endif
1448
1449    _LIBCPP_INLINE_VISIBILITY
1450    size_type __get_short_size() const _NOEXCEPT
1451#   ifdef _LIBCPP_BIG_ENDIAN
1452        {return __r_.first().__s.__size_ >> 1;}
1453#   else
1454        {return __r_.first().__s.__size_;}
1455#   endif
1456
1457#else  // _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
1458
1459    _LIBCPP_INLINE_VISIBILITY
1460    void __set_short_size(size_type __s) _NOEXCEPT
1461#   ifdef _LIBCPP_BIG_ENDIAN
1462        {__r_.first().__s.__size_ = (unsigned char)(__s);}
1463#   else
1464        {__r_.first().__s.__size_ = (unsigned char)(__s << 1);}
1465#   endif
1466
1467    _LIBCPP_INLINE_VISIBILITY
1468    size_type __get_short_size() const _NOEXCEPT
1469#   ifdef _LIBCPP_BIG_ENDIAN
1470        {return __r_.first().__s.__size_;}
1471#   else
1472        {return __r_.first().__s.__size_ >> 1;}
1473#   endif
1474
1475#endif  // _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
1476
1477    _LIBCPP_INLINE_VISIBILITY
1478    void __set_long_size(size_type __s) _NOEXCEPT
1479        {__r_.first().__l.__size_ = __s;}
1480    _LIBCPP_INLINE_VISIBILITY
1481    size_type __get_long_size() const _NOEXCEPT
1482        {return __r_.first().__l.__size_;}
1483    _LIBCPP_INLINE_VISIBILITY
1484    void __set_size(size_type __s) _NOEXCEPT
1485        {if (__is_long()) __set_long_size(__s); else __set_short_size(__s);}
1486
1487    _LIBCPP_INLINE_VISIBILITY
1488    void __set_long_cap(size_type __s) _NOEXCEPT
1489        {__r_.first().__l.__cap_  = __long_mask | __s;}
1490    _LIBCPP_INLINE_VISIBILITY
1491    size_type __get_long_cap() const _NOEXCEPT
1492        {return __r_.first().__l.__cap_ & size_type(~__long_mask);}
1493
1494    _LIBCPP_INLINE_VISIBILITY
1495    void __set_long_pointer(pointer __p) _NOEXCEPT
1496        {__r_.first().__l.__data_ = __p;}
1497    _LIBCPP_INLINE_VISIBILITY
1498    pointer __get_long_pointer() _NOEXCEPT
1499        {return __r_.first().__l.__data_;}
1500    _LIBCPP_INLINE_VISIBILITY
1501    const_pointer __get_long_pointer() const _NOEXCEPT
1502        {return __r_.first().__l.__data_;}
1503    _LIBCPP_INLINE_VISIBILITY
1504    pointer __get_short_pointer() _NOEXCEPT
1505        {return pointer_traits<pointer>::pointer_to(__r_.first().__s.__data_[0]);}
1506    _LIBCPP_INLINE_VISIBILITY
1507    const_pointer __get_short_pointer() const _NOEXCEPT
1508        {return pointer_traits<const_pointer>::pointer_to(__r_.first().__s.__data_[0]);}
1509    _LIBCPP_INLINE_VISIBILITY
1510    pointer __get_pointer() _NOEXCEPT
1511        {return __is_long() ? __get_long_pointer() : __get_short_pointer();}
1512    _LIBCPP_INLINE_VISIBILITY
1513    const_pointer __get_pointer() const _NOEXCEPT
1514        {return __is_long() ? __get_long_pointer() : __get_short_pointer();}
1515
1516    _LIBCPP_INLINE_VISIBILITY
1517    void __zero() _NOEXCEPT
1518        {
1519            size_type (&__a)[__n_words] = __r_.first().__r.__words;
1520            for (unsigned __i = 0; __i < __n_words; ++__i)
1521                __a[__i] = 0;
1522        }
1523
1524    template <size_type __a> static
1525        _LIBCPP_INLINE_VISIBILITY
1526        size_type __align_it(size_type __s) _NOEXCEPT
1527            {return (__s + (__a-1)) & ~(__a-1);}
1528    enum {__alignment = 16};
1529    static _LIBCPP_INLINE_VISIBILITY
1530    size_type __recommend(size_type __s) _NOEXCEPT
1531        {
1532        if (__s < __min_cap) return static_cast<size_type>(__min_cap) - 1;
1533        size_type __guess = __align_it<sizeof(value_type) < __alignment ?
1534                     __alignment/sizeof(value_type) : 1 > (__s+1) - 1;
1535        if (__guess == __min_cap) ++__guess;
1536        return __guess;
1537        }
1538
1539    inline
1540    void __init(const value_type* __s, size_type __sz, size_type __reserve);
1541    inline
1542    void __init(const value_type* __s, size_type __sz);
1543    inline
1544    void __init(size_type __n, value_type __c);
1545
1546    template <class _InputIterator>
1547    inline
1548    typename enable_if
1549    <
1550        __is_exactly_cpp17_input_iterator<_InputIterator>::value,
1551        void
1552    >::type
1553    __init(_InputIterator __first, _InputIterator __last);
1554
1555    template <class _ForwardIterator>
1556    inline
1557    typename enable_if
1558    <
1559        __is_cpp17_forward_iterator<_ForwardIterator>::value,
1560        void
1561    >::type
1562    __init(_ForwardIterator __first, _ForwardIterator __last);
1563
1564    void __grow_by(size_type __old_cap, size_type __delta_cap, size_type __old_sz,
1565                   size_type __n_copy,  size_type __n_del,     size_type __n_add = 0);
1566    void __grow_by_and_replace(size_type __old_cap, size_type __delta_cap, size_type __old_sz,
1567                               size_type __n_copy,  size_type __n_del,
1568                               size_type __n_add, const value_type* __p_new_stuff);
1569
1570    _LIBCPP_INLINE_VISIBILITY
1571    void __erase_to_end(size_type __pos);
1572
1573    _LIBCPP_INLINE_VISIBILITY
1574    void __copy_assign_alloc(const basic_string& __str)
1575        {__copy_assign_alloc(__str, integral_constant<bool,
1576                      __alloc_traits::propagate_on_container_copy_assignment::value>());}
1577
1578    _LIBCPP_INLINE_VISIBILITY
1579    void __copy_assign_alloc(const basic_string& __str, true_type)
1580        {
1581            if (__alloc() == __str.__alloc())
1582                __alloc() = __str.__alloc();
1583            else
1584            {
1585                if (!__str.__is_long())
1586                {
1587                    __clear_and_shrink();
1588                    __alloc() = __str.__alloc();
1589                }
1590                else
1591                {
1592                    allocator_type __a = __str.__alloc();
1593                    pointer __p = __alloc_traits::allocate(__a, __str.__get_long_cap());
1594                    __clear_and_shrink();
1595                    __alloc() = _VSTD::move(__a);
1596                    __set_long_pointer(__p);
1597                    __set_long_cap(__str.__get_long_cap());
1598                    __set_long_size(__str.size());
1599                }
1600            }
1601        }
1602
1603    _LIBCPP_INLINE_VISIBILITY
1604    void __copy_assign_alloc(const basic_string&, false_type) _NOEXCEPT
1605        {}
1606
1607#ifndef _LIBCPP_CXX03_LANG
1608    _LIBCPP_INLINE_VISIBILITY
1609    void __move_assign(basic_string& __str, false_type)
1610        _NOEXCEPT_(__alloc_traits::is_always_equal::value);
1611    _LIBCPP_INLINE_VISIBILITY
1612    void __move_assign(basic_string& __str, true_type)
1613#if _LIBCPP_STD_VER > 14
1614        _NOEXCEPT;
1615#else
1616        _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value);
1617#endif
1618#endif
1619
1620    _LIBCPP_INLINE_VISIBILITY
1621    void
1622    __move_assign_alloc(basic_string& __str)
1623        _NOEXCEPT_(
1624            !__alloc_traits::propagate_on_container_move_assignment::value ||
1625            is_nothrow_move_assignable<allocator_type>::value)
1626    {__move_assign_alloc(__str, integral_constant<bool,
1627                      __alloc_traits::propagate_on_container_move_assignment::value>());}
1628
1629    _LIBCPP_INLINE_VISIBILITY
1630    void __move_assign_alloc(basic_string& __c, true_type)
1631        _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value)
1632        {
1633            __alloc() = _VSTD::move(__c.__alloc());
1634        }
1635
1636    _LIBCPP_INLINE_VISIBILITY
1637    void __move_assign_alloc(basic_string&, false_type)
1638        _NOEXCEPT
1639        {}
1640
1641    _LIBCPP_INLINE_VISIBILITY void __invalidate_all_iterators();
1642    _LIBCPP_INLINE_VISIBILITY void __invalidate_iterators_past(size_type);
1643
1644    friend basic_string operator+<>(const basic_string&, const basic_string&);
1645    friend basic_string operator+<>(const value_type*, const basic_string&);
1646    friend basic_string operator+<>(value_type, const basic_string&);
1647    friend basic_string operator+<>(const basic_string&, const value_type*);
1648    friend basic_string operator+<>(const basic_string&, value_type);
1649};
1650
1651#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
1652template<class _InputIterator,
1653         class _CharT = typename iterator_traits<_InputIterator>::value_type,
1654         class _Allocator = allocator<_CharT>,
1655         class = typename enable_if<__is_cpp17_input_iterator<_InputIterator>::value, void>::type,
1656         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type
1657         >
1658basic_string(_InputIterator, _InputIterator, _Allocator = _Allocator())
1659  -> basic_string<_CharT, char_traits<_CharT>, _Allocator>;
1660
1661template<class _CharT,
1662         class _Traits,
1663         class _Allocator = allocator<_CharT>,
1664         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type
1665         >
1666explicit basic_string(basic_string_view<_CharT, _Traits>, const _Allocator& = _Allocator())
1667  -> basic_string<_CharT, _Traits, _Allocator>;
1668
1669template<class _CharT,
1670         class _Traits,
1671         class _Allocator = allocator<_CharT>,
1672         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type,
1673         class _Sz = typename allocator_traits<_Allocator>::size_type
1674         >
1675basic_string(basic_string_view<_CharT, _Traits>, _Sz, _Sz, const _Allocator& = _Allocator())
1676  -> basic_string<_CharT, _Traits, _Allocator>;
1677#endif
1678
1679
1680template <class _CharT, class _Traits, class _Allocator>
1681inline
1682void
1683basic_string<_CharT, _Traits, _Allocator>::__invalidate_all_iterators()
1684{
1685#if _LIBCPP_DEBUG_LEVEL >= 2
1686    __get_db()->__invalidate_all(this);
1687#endif  // _LIBCPP_DEBUG_LEVEL >= 2
1688}
1689
1690template <class _CharT, class _Traits, class _Allocator>
1691inline
1692void
1693basic_string<_CharT, _Traits, _Allocator>::__invalidate_iterators_past(size_type
1694#if _LIBCPP_DEBUG_LEVEL >= 2
1695                                                                        __pos
1696#endif
1697                                                                      )
1698{
1699#if _LIBCPP_DEBUG_LEVEL >= 2
1700    __c_node* __c = __get_db()->__find_c_and_lock(this);
1701    if (__c)
1702    {
1703        const_pointer __new_last = __get_pointer() + __pos;
1704        for (__i_node** __p = __c->end_; __p != __c->beg_; )
1705        {
1706            --__p;
1707            const_iterator* __i = static_cast<const_iterator*>((*__p)->__i_);
1708            if (__i->base() > __new_last)
1709            {
1710                (*__p)->__c_ = nullptr;
1711                if (--__c->end_ != __p)
1712                    memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
1713            }
1714        }
1715        __get_db()->unlock();
1716    }
1717#endif  // _LIBCPP_DEBUG_LEVEL >= 2
1718}
1719
1720template <class _CharT, class _Traits, class _Allocator>
1721inline
1722basic_string<_CharT, _Traits, _Allocator>::basic_string()
1723    _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
1724     : __r_(__default_init_tag(), __default_init_tag())
1725{
1726#if _LIBCPP_DEBUG_LEVEL >= 2
1727    __get_db()->__insert_c(this);
1728#endif
1729    __zero();
1730}
1731
1732template <class _CharT, class _Traits, class _Allocator>
1733inline
1734basic_string<_CharT, _Traits, _Allocator>::basic_string(const allocator_type& __a)
1735#if _LIBCPP_STD_VER <= 14
1736        _NOEXCEPT_(is_nothrow_copy_constructible<allocator_type>::value)
1737#else
1738        _NOEXCEPT
1739#endif
1740: __r_(__default_init_tag(), __a)
1741{
1742#if _LIBCPP_DEBUG_LEVEL >= 2
1743    __get_db()->__insert_c(this);
1744#endif
1745    __zero();
1746}
1747
1748template <class _CharT, class _Traits, class _Allocator>
1749void basic_string<_CharT, _Traits, _Allocator>::__init(const value_type* __s,
1750                                                       size_type __sz,
1751                                                       size_type __reserve)
1752{
1753    if (__reserve > max_size())
1754        this->__throw_length_error();
1755    pointer __p;
1756    if (__reserve < __min_cap)
1757    {
1758        __set_short_size(__sz);
1759        __p = __get_short_pointer();
1760    }
1761    else
1762    {
1763        size_type __cap = __recommend(__reserve);
1764        __p = __alloc_traits::allocate(__alloc(), __cap+1);
1765        __set_long_pointer(__p);
1766        __set_long_cap(__cap+1);
1767        __set_long_size(__sz);
1768    }
1769    traits_type::copy(_VSTD::__to_address(__p), __s, __sz);
1770    traits_type::assign(__p[__sz], value_type());
1771}
1772
1773template <class _CharT, class _Traits, class _Allocator>
1774void
1775basic_string<_CharT, _Traits, _Allocator>::__init(const value_type* __s, size_type __sz)
1776{
1777    if (__sz > max_size())
1778        this->__throw_length_error();
1779    pointer __p;
1780    if (__sz < __min_cap)
1781    {
1782        __set_short_size(__sz);
1783        __p = __get_short_pointer();
1784    }
1785    else
1786    {
1787        size_type __cap = __recommend(__sz);
1788        __p = __alloc_traits::allocate(__alloc(), __cap+1);
1789        __set_long_pointer(__p);
1790        __set_long_cap(__cap+1);
1791        __set_long_size(__sz);
1792    }
1793    traits_type::copy(_VSTD::__to_address(__p), __s, __sz);
1794    traits_type::assign(__p[__sz], value_type());
1795}
1796
1797template <class _CharT, class _Traits, class _Allocator>
1798template <class>
1799basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, const _Allocator& __a)
1800    : __r_(__default_init_tag(), __a)
1801{
1802    _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*, allocator) detected nullptr");
1803    __init(__s, traits_type::length(__s));
1804#if _LIBCPP_DEBUG_LEVEL >= 2
1805    __get_db()->__insert_c(this);
1806#endif
1807}
1808
1809template <class _CharT, class _Traits, class _Allocator>
1810inline
1811basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_type __n)
1812     : __r_(__default_init_tag(), __default_init_tag())
1813{
1814    _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n) detected nullptr");
1815    __init(__s, __n);
1816#if _LIBCPP_DEBUG_LEVEL >= 2
1817    __get_db()->__insert_c(this);
1818#endif
1819}
1820
1821template <class _CharT, class _Traits, class _Allocator>
1822inline
1823basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_type __n, const _Allocator& __a)
1824    : __r_(__default_init_tag(), __a)
1825{
1826    _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n, allocator) detected nullptr");
1827    __init(__s, __n);
1828#if _LIBCPP_DEBUG_LEVEL >= 2
1829    __get_db()->__insert_c(this);
1830#endif
1831}
1832
1833template <class _CharT, class _Traits, class _Allocator>
1834basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str)
1835    : __r_(__default_init_tag(), __alloc_traits::select_on_container_copy_construction(__str.__alloc()))
1836{
1837    if (!__str.__is_long())
1838        __r_.first().__r = __str.__r_.first().__r;
1839    else
1840        __init(_VSTD::__to_address(__str.__get_long_pointer()), __str.__get_long_size());
1841#if _LIBCPP_DEBUG_LEVEL >= 2
1842    __get_db()->__insert_c(this);
1843#endif
1844}
1845
1846template <class _CharT, class _Traits, class _Allocator>
1847basic_string<_CharT, _Traits, _Allocator>::basic_string(
1848    const basic_string& __str, const allocator_type& __a)
1849    : __r_(__default_init_tag(), __a)
1850{
1851    if (!__str.__is_long())
1852        __r_.first().__r = __str.__r_.first().__r;
1853    else
1854        __init(_VSTD::__to_address(__str.__get_long_pointer()), __str.__get_long_size());
1855#if _LIBCPP_DEBUG_LEVEL >= 2
1856    __get_db()->__insert_c(this);
1857#endif
1858}
1859
1860#ifndef _LIBCPP_CXX03_LANG
1861
1862template <class _CharT, class _Traits, class _Allocator>
1863inline
1864basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str)
1865#if _LIBCPP_STD_VER <= 14
1866        _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value)
1867#else
1868        _NOEXCEPT
1869#endif
1870    : __r_(_VSTD::move(__str.__r_))
1871{
1872    __str.__zero();
1873#if _LIBCPP_DEBUG_LEVEL >= 2
1874    __get_db()->__insert_c(this);
1875    if (__is_long())
1876        __get_db()->swap(this, &__str);
1877#endif
1878}
1879
1880template <class _CharT, class _Traits, class _Allocator>
1881inline
1882basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str, const allocator_type& __a)
1883    : __r_(__default_init_tag(), __a)
1884{
1885    if (__str.__is_long() && __a != __str.__alloc()) // copy, not move
1886        __init(_VSTD::__to_address(__str.__get_long_pointer()), __str.__get_long_size());
1887    else
1888    {
1889        __r_.first().__r = __str.__r_.first().__r;
1890        __str.__zero();
1891    }
1892#if _LIBCPP_DEBUG_LEVEL >= 2
1893    __get_db()->__insert_c(this);
1894    if (__is_long())
1895        __get_db()->swap(this, &__str);
1896#endif
1897}
1898
1899#endif  // _LIBCPP_CXX03_LANG
1900
1901template <class _CharT, class _Traits, class _Allocator>
1902void
1903basic_string<_CharT, _Traits, _Allocator>::__init(size_type __n, value_type __c)
1904{
1905    if (__n > max_size())
1906        this->__throw_length_error();
1907    pointer __p;
1908    if (__n < __min_cap)
1909    {
1910        __set_short_size(__n);
1911        __p = __get_short_pointer();
1912    }
1913    else
1914    {
1915        size_type __cap = __recommend(__n);
1916        __p = __alloc_traits::allocate(__alloc(), __cap+1);
1917        __set_long_pointer(__p);
1918        __set_long_cap(__cap+1);
1919        __set_long_size(__n);
1920    }
1921    traits_type::assign(_VSTD::__to_address(__p), __n, __c);
1922    traits_type::assign(__p[__n], value_type());
1923}
1924
1925template <class _CharT, class _Traits, class _Allocator>
1926inline
1927basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __c)
1928     : __r_(__default_init_tag(), __default_init_tag())
1929{
1930    __init(__n, __c);
1931#if _LIBCPP_DEBUG_LEVEL >= 2
1932    __get_db()->__insert_c(this);
1933#endif
1934}
1935
1936template <class _CharT, class _Traits, class _Allocator>
1937template <class>
1938basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __c, const _Allocator& __a)
1939    : __r_(__default_init_tag(), __a)
1940{
1941    __init(__n, __c);
1942#if _LIBCPP_DEBUG_LEVEL >= 2
1943    __get_db()->__insert_c(this);
1944#endif
1945}
1946
1947template <class _CharT, class _Traits, class _Allocator>
1948basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str,
1949                                                        size_type __pos, size_type __n,
1950                                                        const _Allocator& __a)
1951    : __r_(__default_init_tag(), __a)
1952{
1953    size_type __str_sz = __str.size();
1954    if (__pos > __str_sz)
1955        this->__throw_out_of_range();
1956    __init(__str.data() + __pos, _VSTD::min(__n, __str_sz - __pos));
1957#if _LIBCPP_DEBUG_LEVEL >= 2
1958    __get_db()->__insert_c(this);
1959#endif
1960}
1961
1962template <class _CharT, class _Traits, class _Allocator>
1963inline
1964basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str, size_type __pos,
1965                                                        const _Allocator& __a)
1966    : __r_(__default_init_tag(), __a)
1967{
1968    size_type __str_sz = __str.size();
1969    if (__pos > __str_sz)
1970        this->__throw_out_of_range();
1971    __init(__str.data() + __pos, __str_sz - __pos);
1972#if _LIBCPP_DEBUG_LEVEL >= 2
1973    __get_db()->__insert_c(this);
1974#endif
1975}
1976
1977template <class _CharT, class _Traits, class _Allocator>
1978template <class _Tp, class>
1979basic_string<_CharT, _Traits, _Allocator>::basic_string(
1980             const _Tp& __t, size_type __pos, size_type __n, const allocator_type& __a)
1981    : __r_(__default_init_tag(), __a)
1982{
1983    __self_view __sv0 = __t;
1984    __self_view __sv = __sv0.substr(__pos, __n);
1985    __init(__sv.data(), __sv.size());
1986#if _LIBCPP_DEBUG_LEVEL >= 2
1987    __get_db()->__insert_c(this);
1988#endif
1989}
1990
1991template <class _CharT, class _Traits, class _Allocator>
1992template <class _Tp, class>
1993basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp & __t)
1994     : __r_(__default_init_tag(), __default_init_tag())
1995{
1996    __self_view __sv = __t;
1997    __init(__sv.data(), __sv.size());
1998#if _LIBCPP_DEBUG_LEVEL >= 2
1999    __get_db()->__insert_c(this);
2000#endif
2001}
2002
2003template <class _CharT, class _Traits, class _Allocator>
2004template <class _Tp, class>
2005basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp & __t, const _Allocator& __a)
2006    : __r_(__default_init_tag(), __a)
2007{
2008    __self_view __sv = __t;
2009    __init(__sv.data(), __sv.size());
2010#if _LIBCPP_DEBUG_LEVEL >= 2
2011    __get_db()->__insert_c(this);
2012#endif
2013}
2014
2015template <class _CharT, class _Traits, class _Allocator>
2016template <class _InputIterator>
2017typename enable_if
2018<
2019    __is_exactly_cpp17_input_iterator<_InputIterator>::value,
2020    void
2021>::type
2022basic_string<_CharT, _Traits, _Allocator>::__init(_InputIterator __first, _InputIterator __last)
2023{
2024    __zero();
2025#ifndef _LIBCPP_NO_EXCEPTIONS
2026    try
2027    {
2028#endif  // _LIBCPP_NO_EXCEPTIONS
2029    for (; __first != __last; ++__first)
2030        push_back(*__first);
2031#ifndef _LIBCPP_NO_EXCEPTIONS
2032    }
2033    catch (...)
2034    {
2035        if (__is_long())
2036            __alloc_traits::deallocate(__alloc(), __get_long_pointer(), __get_long_cap());
2037        throw;
2038    }
2039#endif  // _LIBCPP_NO_EXCEPTIONS
2040}
2041
2042template <class _CharT, class _Traits, class _Allocator>
2043template <class _ForwardIterator>
2044typename enable_if
2045<
2046    __is_cpp17_forward_iterator<_ForwardIterator>::value,
2047    void
2048>::type
2049basic_string<_CharT, _Traits, _Allocator>::__init(_ForwardIterator __first, _ForwardIterator __last)
2050{
2051    size_type __sz = static_cast<size_type>(_VSTD::distance(__first, __last));
2052    if (__sz > max_size())
2053        this->__throw_length_error();
2054    pointer __p;
2055    if (__sz < __min_cap)
2056    {
2057        __set_short_size(__sz);
2058        __p = __get_short_pointer();
2059    }
2060    else
2061    {
2062        size_type __cap = __recommend(__sz);
2063        __p = __alloc_traits::allocate(__alloc(), __cap+1);
2064        __set_long_pointer(__p);
2065        __set_long_cap(__cap+1);
2066        __set_long_size(__sz);
2067    }
2068    for (; __first != __last; ++__first, (void) ++__p)
2069        traits_type::assign(*__p, *__first);
2070    traits_type::assign(*__p, value_type());
2071}
2072
2073template <class _CharT, class _Traits, class _Allocator>
2074template<class _InputIterator, class>
2075inline
2076basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first, _InputIterator __last)
2077     : __r_(__default_init_tag(), __default_init_tag())
2078{
2079    __init(__first, __last);
2080#if _LIBCPP_DEBUG_LEVEL >= 2
2081    __get_db()->__insert_c(this);
2082#endif
2083}
2084
2085template <class _CharT, class _Traits, class _Allocator>
2086template<class _InputIterator, class>
2087inline
2088basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first, _InputIterator __last,
2089                                                        const allocator_type& __a)
2090    : __r_(__default_init_tag(), __a)
2091{
2092    __init(__first, __last);
2093#if _LIBCPP_DEBUG_LEVEL >= 2
2094    __get_db()->__insert_c(this);
2095#endif
2096}
2097
2098#ifndef _LIBCPP_CXX03_LANG
2099
2100template <class _CharT, class _Traits, class _Allocator>
2101inline
2102basic_string<_CharT, _Traits, _Allocator>::basic_string(
2103    initializer_list<_CharT> __il)
2104     : __r_(__default_init_tag(), __default_init_tag())
2105{
2106    __init(__il.begin(), __il.end());
2107#if _LIBCPP_DEBUG_LEVEL >= 2
2108    __get_db()->__insert_c(this);
2109#endif
2110}
2111
2112template <class _CharT, class _Traits, class _Allocator>
2113inline
2114
2115basic_string<_CharT, _Traits, _Allocator>::basic_string(
2116    initializer_list<_CharT> __il, const _Allocator& __a)
2117    : __r_(__default_init_tag(), __a)
2118{
2119    __init(__il.begin(), __il.end());
2120#if _LIBCPP_DEBUG_LEVEL >= 2
2121    __get_db()->__insert_c(this);
2122#endif
2123}
2124
2125#endif  // _LIBCPP_CXX03_LANG
2126
2127template <class _CharT, class _Traits, class _Allocator>
2128basic_string<_CharT, _Traits, _Allocator>::~basic_string()
2129{
2130#if _LIBCPP_DEBUG_LEVEL >= 2
2131    __get_db()->__erase_c(this);
2132#endif
2133    if (__is_long())
2134        __alloc_traits::deallocate(__alloc(), __get_long_pointer(), __get_long_cap());
2135}
2136
2137template <class _CharT, class _Traits, class _Allocator>
2138void
2139basic_string<_CharT, _Traits, _Allocator>::__grow_by_and_replace
2140    (size_type __old_cap, size_type __delta_cap, size_type __old_sz,
2141     size_type __n_copy,  size_type __n_del,     size_type __n_add, const value_type* __p_new_stuff)
2142{
2143    size_type __ms = max_size();
2144    if (__delta_cap > __ms - __old_cap - 1)
2145        this->__throw_length_error();
2146    pointer __old_p = __get_pointer();
2147    size_type __cap = __old_cap < __ms / 2 - __alignment ?
2148                          __recommend(_VSTD::max(__old_cap + __delta_cap, 2 * __old_cap)) :
2149                          __ms - 1;
2150    pointer __p = __alloc_traits::allocate(__alloc(), __cap+1);
2151    __invalidate_all_iterators();
2152    if (__n_copy != 0)
2153        traits_type::copy(_VSTD::__to_address(__p),
2154                          _VSTD::__to_address(__old_p), __n_copy);
2155    if (__n_add != 0)
2156        traits_type::copy(_VSTD::__to_address(__p) + __n_copy, __p_new_stuff, __n_add);
2157    size_type __sec_cp_sz = __old_sz - __n_del - __n_copy;
2158    if (__sec_cp_sz != 0)
2159        traits_type::copy(_VSTD::__to_address(__p) + __n_copy + __n_add,
2160                          _VSTD::__to_address(__old_p) + __n_copy + __n_del, __sec_cp_sz);
2161    if (__old_cap+1 != __min_cap)
2162        __alloc_traits::deallocate(__alloc(), __old_p, __old_cap+1);
2163    __set_long_pointer(__p);
2164    __set_long_cap(__cap+1);
2165    __old_sz = __n_copy + __n_add + __sec_cp_sz;
2166    __set_long_size(__old_sz);
2167    traits_type::assign(__p[__old_sz], value_type());
2168}
2169
2170template <class _CharT, class _Traits, class _Allocator>
2171void
2172basic_string<_CharT, _Traits, _Allocator>::__grow_by(size_type __old_cap, size_type __delta_cap, size_type __old_sz,
2173                                                     size_type __n_copy,  size_type __n_del,     size_type __n_add)
2174{
2175    size_type __ms = max_size();
2176    if (__delta_cap > __ms - __old_cap)
2177        this->__throw_length_error();
2178    pointer __old_p = __get_pointer();
2179    size_type __cap = __old_cap < __ms / 2 - __alignment ?
2180                          __recommend(_VSTD::max(__old_cap + __delta_cap, 2 * __old_cap)) :
2181                          __ms - 1;
2182    pointer __p = __alloc_traits::allocate(__alloc(), __cap+1);
2183    __invalidate_all_iterators();
2184    if (__n_copy != 0)
2185        traits_type::copy(_VSTD::__to_address(__p),
2186                          _VSTD::__to_address(__old_p), __n_copy);
2187    size_type __sec_cp_sz = __old_sz - __n_del - __n_copy;
2188    if (__sec_cp_sz != 0)
2189        traits_type::copy(_VSTD::__to_address(__p) + __n_copy + __n_add,
2190                          _VSTD::__to_address(__old_p) + __n_copy + __n_del,
2191                          __sec_cp_sz);
2192    if (__old_cap+1 != __min_cap)
2193        __alloc_traits::deallocate(__alloc(), __old_p, __old_cap+1);
2194    __set_long_pointer(__p);
2195    __set_long_cap(__cap+1);
2196}
2197
2198// assign
2199
2200template <class _CharT, class _Traits, class _Allocator>
2201basic_string<_CharT, _Traits, _Allocator>&
2202basic_string<_CharT, _Traits, _Allocator>::assign(const value_type* __s, size_type __n)
2203{
2204    _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::assign received nullptr");
2205    size_type __cap = capacity();
2206    if (__cap >= __n)
2207    {
2208        value_type* __p = _VSTD::__to_address(__get_pointer());
2209        traits_type::move(__p, __s, __n);
2210        traits_type::assign(__p[__n], value_type());
2211        __set_size(__n);
2212        __invalidate_iterators_past(__n);
2213    }
2214    else
2215    {
2216        size_type __sz = size();
2217        __grow_by_and_replace(__cap, __n - __cap, __sz, 0, __sz, __n, __s);
2218    }
2219    return *this;
2220}
2221
2222template <class _CharT, class _Traits, class _Allocator>
2223basic_string<_CharT, _Traits, _Allocator>&
2224basic_string<_CharT, _Traits, _Allocator>::assign(size_type __n, value_type __c)
2225{
2226    size_type __cap = capacity();
2227    if (__cap < __n)
2228    {
2229        size_type __sz = size();
2230        __grow_by(__cap, __n - __cap, __sz, 0, __sz);
2231    }
2232    else
2233        __invalidate_iterators_past(__n);
2234    value_type* __p = _VSTD::__to_address(__get_pointer());
2235    traits_type::assign(__p, __n, __c);
2236    traits_type::assign(__p[__n], value_type());
2237    __set_size(__n);
2238    return *this;
2239}
2240
2241template <class _CharT, class _Traits, class _Allocator>
2242basic_string<_CharT, _Traits, _Allocator>&
2243basic_string<_CharT, _Traits, _Allocator>::operator=(value_type __c)
2244{
2245    pointer __p;
2246    if (__is_long())
2247    {
2248        __p = __get_long_pointer();
2249        __set_long_size(1);
2250    }
2251    else
2252    {
2253        __p = __get_short_pointer();
2254        __set_short_size(1);
2255    }
2256    traits_type::assign(*__p, __c);
2257    traits_type::assign(*++__p, value_type());
2258    __invalidate_iterators_past(1);
2259    return *this;
2260}
2261
2262template <class _CharT, class _Traits, class _Allocator>
2263basic_string<_CharT, _Traits, _Allocator>&
2264basic_string<_CharT, _Traits, _Allocator>::operator=(const basic_string& __str)
2265{
2266    if (this != &__str)
2267    {
2268        __copy_assign_alloc(__str);
2269        return assign(__str.data(), __str.size());
2270    }
2271    return *this;
2272}
2273
2274#ifndef _LIBCPP_CXX03_LANG
2275
2276template <class _CharT, class _Traits, class _Allocator>
2277inline
2278void
2279basic_string<_CharT, _Traits, _Allocator>::__move_assign(basic_string& __str, false_type)
2280    _NOEXCEPT_(__alloc_traits::is_always_equal::value)
2281{
2282    if (__alloc() != __str.__alloc())
2283        assign(__str);
2284    else
2285        __move_assign(__str, true_type());
2286}
2287
2288template <class _CharT, class _Traits, class _Allocator>
2289inline
2290void
2291basic_string<_CharT, _Traits, _Allocator>::__move_assign(basic_string& __str, true_type)
2292#if _LIBCPP_STD_VER > 14
2293    _NOEXCEPT
2294#else
2295    _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value)
2296#endif
2297{
2298  if (__is_long()) {
2299    __alloc_traits::deallocate(__alloc(), __get_long_pointer(),
2300                               __get_long_cap());
2301#if _LIBCPP_STD_VER <= 14
2302    if (!is_nothrow_move_assignable<allocator_type>::value) {
2303      __set_short_size(0);
2304      traits_type::assign(__get_short_pointer()[0], value_type());
2305    }
2306#endif
2307  }
2308  __move_assign_alloc(__str);
2309  __r_.first() = __str.__r_.first();
2310  __str.__set_short_size(0);
2311  traits_type::assign(__str.__get_short_pointer()[0], value_type());
2312}
2313
2314template <class _CharT, class _Traits, class _Allocator>
2315inline
2316basic_string<_CharT, _Traits, _Allocator>&
2317basic_string<_CharT, _Traits, _Allocator>::operator=(basic_string&& __str)
2318    _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value))
2319{
2320    __move_assign(__str, integral_constant<bool,
2321          __alloc_traits::propagate_on_container_move_assignment::value>());
2322    return *this;
2323}
2324
2325#endif
2326
2327template <class _CharT, class _Traits, class _Allocator>
2328template<class _InputIterator>
2329typename enable_if
2330<
2331     __is_exactly_cpp17_input_iterator <_InputIterator>::value
2332          || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
2333    basic_string<_CharT, _Traits, _Allocator>&
2334>::type
2335basic_string<_CharT, _Traits, _Allocator>::assign(_InputIterator __first, _InputIterator __last)
2336{
2337    const basic_string __temp(__first, __last, __alloc());
2338    assign(__temp.data(), __temp.size());
2339    return *this;
2340}
2341
2342template <class _CharT, class _Traits, class _Allocator>
2343template<class _ForwardIterator>
2344typename enable_if
2345<
2346    __is_cpp17_forward_iterator<_ForwardIterator>::value
2347         && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
2348    basic_string<_CharT, _Traits, _Allocator>&
2349>::type
2350basic_string<_CharT, _Traits, _Allocator>::assign(_ForwardIterator __first, _ForwardIterator __last)
2351{
2352    size_type __n = static_cast<size_type>(_VSTD::distance(__first, __last));
2353    size_type __cap = capacity();
2354    if (__cap < __n)
2355    {
2356        size_type __sz = size();
2357        __grow_by(__cap, __n - __cap, __sz, 0, __sz);
2358    }
2359    else
2360        __invalidate_iterators_past(__n);
2361    pointer __p = __get_pointer();
2362    for (; __first != __last; ++__first, ++__p)
2363        traits_type::assign(*__p, *__first);
2364    traits_type::assign(*__p, value_type());
2365    __set_size(__n);
2366    return *this;
2367}
2368
2369template <class _CharT, class _Traits, class _Allocator>
2370basic_string<_CharT, _Traits, _Allocator>&
2371basic_string<_CharT, _Traits, _Allocator>::assign(const basic_string& __str, size_type __pos, size_type __n)
2372{
2373    size_type __sz = __str.size();
2374    if (__pos > __sz)
2375        this->__throw_out_of_range();
2376    return assign(__str.data() + __pos, _VSTD::min(__n, __sz - __pos));
2377}
2378
2379template <class _CharT, class _Traits, class _Allocator>
2380template <class _Tp>
2381typename enable_if
2382<
2383    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
2384    basic_string<_CharT, _Traits, _Allocator>&
2385>::type
2386basic_string<_CharT, _Traits, _Allocator>::assign(const _Tp & __t, size_type __pos, size_type __n)
2387{
2388    __self_view __sv = __t;
2389    size_type __sz = __sv.size();
2390    if (__pos > __sz)
2391        this->__throw_out_of_range();
2392    return assign(__sv.data() + __pos, _VSTD::min(__n, __sz - __pos));
2393}
2394
2395
2396template <class _CharT, class _Traits, class _Allocator>
2397basic_string<_CharT, _Traits, _Allocator>&
2398basic_string<_CharT, _Traits, _Allocator>::assign(const value_type* __s)
2399{
2400    _LIBCPP_ASSERT(__s != nullptr, "string::assign received nullptr");
2401    return assign(__s, traits_type::length(__s));
2402}
2403
2404// append
2405
2406template <class _CharT, class _Traits, class _Allocator>
2407basic_string<_CharT, _Traits, _Allocator>&
2408basic_string<_CharT, _Traits, _Allocator>::append(const value_type* __s, size_type __n)
2409{
2410    _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::append received nullptr");
2411    size_type __cap = capacity();
2412    size_type __sz = size();
2413    if (__cap - __sz >= __n)
2414    {
2415        if (__n)
2416        {
2417            value_type* __p = _VSTD::__to_address(__get_pointer());
2418            traits_type::copy(__p + __sz, __s, __n);
2419            __sz += __n;
2420            __set_size(__sz);
2421            traits_type::assign(__p[__sz], value_type());
2422        }
2423    }
2424    else
2425        __grow_by_and_replace(__cap, __sz + __n - __cap, __sz, __sz, 0, __n, __s);
2426    return *this;
2427}
2428
2429template <class _CharT, class _Traits, class _Allocator>
2430basic_string<_CharT, _Traits, _Allocator>&
2431basic_string<_CharT, _Traits, _Allocator>::append(size_type __n, value_type __c)
2432{
2433    if (__n)
2434    {
2435        size_type __cap = capacity();
2436        size_type __sz = size();
2437        if (__cap - __sz < __n)
2438            __grow_by(__cap, __sz + __n - __cap, __sz, __sz, 0);
2439        pointer __p = __get_pointer();
2440        traits_type::assign(_VSTD::__to_address(__p) + __sz, __n, __c);
2441        __sz += __n;
2442        __set_size(__sz);
2443        traits_type::assign(__p[__sz], value_type());
2444    }
2445    return *this;
2446}
2447
2448template <class _CharT, class _Traits, class _Allocator>
2449inline void
2450basic_string<_CharT, _Traits, _Allocator>::__append_default_init(size_type __n)
2451{
2452    if (__n)
2453    {
2454        size_type __cap = capacity();
2455        size_type __sz = size();
2456        if (__cap - __sz < __n)
2457            __grow_by(__cap, __sz + __n - __cap, __sz, __sz, 0);
2458        pointer __p = __get_pointer();
2459        __sz += __n;
2460        __set_size(__sz);
2461        traits_type::assign(__p[__sz], value_type());
2462    }
2463}
2464
2465template <class _CharT, class _Traits, class _Allocator>
2466void
2467basic_string<_CharT, _Traits, _Allocator>::push_back(value_type __c)
2468{
2469    bool __is_short = !__is_long();
2470    size_type __cap;
2471    size_type __sz;
2472    if (__is_short)
2473    {
2474        __cap = __min_cap - 1;
2475        __sz = __get_short_size();
2476    }
2477    else
2478    {
2479        __cap = __get_long_cap() - 1;
2480        __sz = __get_long_size();
2481    }
2482    if (__sz == __cap)
2483    {
2484        __grow_by(__cap, 1, __sz, __sz, 0);
2485        __is_short = !__is_long();
2486    }
2487    pointer __p;
2488    if (__is_short)
2489    {
2490        __p = __get_short_pointer() + __sz;
2491        __set_short_size(__sz+1);
2492    }
2493    else
2494    {
2495        __p = __get_long_pointer() + __sz;
2496        __set_long_size(__sz+1);
2497    }
2498    traits_type::assign(*__p, __c);
2499    traits_type::assign(*++__p, value_type());
2500}
2501
2502template <class _Tp>
2503bool __ptr_in_range (const _Tp* __p, const _Tp* __first, const _Tp* __last)
2504{
2505    return __first <= __p && __p < __last;
2506}
2507
2508template <class _Tp1, class _Tp2>
2509bool __ptr_in_range (const _Tp1*, const _Tp2*, const _Tp2*)
2510{
2511    return false;
2512}
2513
2514template <class _CharT, class _Traits, class _Allocator>
2515template<class _ForwardIterator>
2516basic_string<_CharT, _Traits, _Allocator>&
2517basic_string<_CharT, _Traits, _Allocator>::__append_forward_unsafe(
2518    _ForwardIterator __first, _ForwardIterator __last)
2519{
2520    static_assert(__is_cpp17_forward_iterator<_ForwardIterator>::value,
2521                  "function requires a ForwardIterator");
2522    size_type __sz = size();
2523    size_type __cap = capacity();
2524    size_type __n = static_cast<size_type>(_VSTD::distance(__first, __last));
2525    if (__n)
2526    {
2527        typedef typename iterator_traits<_ForwardIterator>::reference _CharRef;
2528        _CharRef __tmp_ref = *__first;
2529        if (__ptr_in_range(_VSTD::addressof(__tmp_ref), data(), data() + size()))
2530        {
2531            const basic_string __temp (__first, __last, __alloc());
2532            append(__temp.data(), __temp.size());
2533        }
2534        else
2535        {
2536            if (__cap - __sz < __n)
2537                __grow_by(__cap, __sz + __n - __cap, __sz, __sz, 0);
2538            pointer __p = __get_pointer() + __sz;
2539            for (; __first != __last; ++__p, ++__first)
2540                traits_type::assign(*__p, *__first);
2541            traits_type::assign(*__p, value_type());
2542            __set_size(__sz + __n);
2543        }
2544    }
2545    return *this;
2546}
2547
2548template <class _CharT, class _Traits, class _Allocator>
2549inline
2550basic_string<_CharT, _Traits, _Allocator>&
2551basic_string<_CharT, _Traits, _Allocator>::append(const basic_string& __str)
2552{
2553    return append(__str.data(), __str.size());
2554}
2555
2556template <class _CharT, class _Traits, class _Allocator>
2557basic_string<_CharT, _Traits, _Allocator>&
2558basic_string<_CharT, _Traits, _Allocator>::append(const basic_string& __str, size_type __pos, size_type __n)
2559{
2560    size_type __sz = __str.size();
2561    if (__pos > __sz)
2562        this->__throw_out_of_range();
2563    return append(__str.data() + __pos, _VSTD::min(__n, __sz - __pos));
2564}
2565
2566template <class _CharT, class _Traits, class _Allocator>
2567template <class _Tp>
2568    typename enable_if
2569    <
2570        __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
2571        basic_string<_CharT, _Traits, _Allocator>&
2572    >::type
2573basic_string<_CharT, _Traits, _Allocator>::append(const _Tp & __t, size_type __pos, size_type __n)
2574{
2575    __self_view __sv = __t;
2576    size_type __sz = __sv.size();
2577    if (__pos > __sz)
2578        this->__throw_out_of_range();
2579    return append(__sv.data() + __pos, _VSTD::min(__n, __sz - __pos));
2580}
2581
2582template <class _CharT, class _Traits, class _Allocator>
2583basic_string<_CharT, _Traits, _Allocator>&
2584basic_string<_CharT, _Traits, _Allocator>::append(const value_type* __s)
2585{
2586    _LIBCPP_ASSERT(__s != nullptr, "string::append received nullptr");
2587    return append(__s, traits_type::length(__s));
2588}
2589
2590// insert
2591
2592template <class _CharT, class _Traits, class _Allocator>
2593basic_string<_CharT, _Traits, _Allocator>&
2594basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos, const value_type* __s, size_type __n)
2595{
2596    _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::insert received nullptr");
2597    size_type __sz = size();
2598    if (__pos > __sz)
2599        this->__throw_out_of_range();
2600    size_type __cap = capacity();
2601    if (__cap - __sz >= __n)
2602    {
2603        if (__n)
2604        {
2605            value_type* __p = _VSTD::__to_address(__get_pointer());
2606            size_type __n_move = __sz - __pos;
2607            if (__n_move != 0)
2608            {
2609                if (__p + __pos <= __s && __s < __p + __sz)
2610                    __s += __n;
2611                traits_type::move(__p + __pos + __n, __p + __pos, __n_move);
2612            }
2613            traits_type::move(__p + __pos, __s, __n);
2614            __sz += __n;
2615            __set_size(__sz);
2616            traits_type::assign(__p[__sz], value_type());
2617        }
2618    }
2619    else
2620        __grow_by_and_replace(__cap, __sz + __n - __cap, __sz, __pos, 0, __n, __s);
2621    return *this;
2622}
2623
2624template <class _CharT, class _Traits, class _Allocator>
2625basic_string<_CharT, _Traits, _Allocator>&
2626basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos, size_type __n, value_type __c)
2627{
2628    size_type __sz = size();
2629    if (__pos > __sz)
2630        this->__throw_out_of_range();
2631    if (__n)
2632    {
2633        size_type __cap = capacity();
2634        value_type* __p;
2635        if (__cap - __sz >= __n)
2636        {
2637            __p = _VSTD::__to_address(__get_pointer());
2638            size_type __n_move = __sz - __pos;
2639            if (__n_move != 0)
2640                traits_type::move(__p + __pos + __n, __p + __pos, __n_move);
2641        }
2642        else
2643        {
2644            __grow_by(__cap, __sz + __n - __cap, __sz, __pos, 0, __n);
2645            __p = _VSTD::__to_address(__get_long_pointer());
2646        }
2647        traits_type::assign(__p + __pos, __n, __c);
2648        __sz += __n;
2649        __set_size(__sz);
2650        traits_type::assign(__p[__sz], value_type());
2651    }
2652    return *this;
2653}
2654
2655template <class _CharT, class _Traits, class _Allocator>
2656template<class _InputIterator>
2657typename enable_if
2658<
2659   __is_exactly_cpp17_input_iterator<_InputIterator>::value
2660        || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
2661   typename basic_string<_CharT, _Traits, _Allocator>::iterator
2662>::type
2663basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, _InputIterator __first, _InputIterator __last)
2664{
2665#if _LIBCPP_DEBUG_LEVEL >= 2
2666    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__pos) == this,
2667        "string::insert(iterator, range) called with an iterator not"
2668        " referring to this string");
2669#endif
2670    const basic_string __temp(__first, __last, __alloc());
2671    return insert(__pos, __temp.data(), __temp.data() + __temp.size());
2672}
2673
2674template <class _CharT, class _Traits, class _Allocator>
2675template<class _ForwardIterator>
2676typename enable_if
2677<
2678    __is_cpp17_forward_iterator<_ForwardIterator>::value
2679        && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
2680    typename basic_string<_CharT, _Traits, _Allocator>::iterator
2681>::type
2682basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, _ForwardIterator __first, _ForwardIterator __last)
2683{
2684#if _LIBCPP_DEBUG_LEVEL >= 2
2685    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__pos) == this,
2686        "string::insert(iterator, range) called with an iterator not"
2687        " referring to this string");
2688#endif
2689    size_type __ip = static_cast<size_type>(__pos - begin());
2690    size_type __n = static_cast<size_type>(_VSTD::distance(__first, __last));
2691    if (__n)
2692    {
2693        typedef typename iterator_traits<_ForwardIterator>::reference _CharRef;
2694        _CharRef __tmp_char = *__first;
2695        if (__ptr_in_range(_VSTD::addressof(__tmp_char), data(), data() + size()))
2696        {
2697            const basic_string __temp(__first, __last, __alloc());
2698            return insert(__pos, __temp.data(), __temp.data() + __temp.size());
2699        }
2700
2701        size_type __sz = size();
2702        size_type __cap = capacity();
2703        value_type* __p;
2704        if (__cap - __sz >= __n)
2705        {
2706            __p = _VSTD::__to_address(__get_pointer());
2707            size_type __n_move = __sz - __ip;
2708            if (__n_move != 0)
2709                traits_type::move(__p + __ip + __n, __p + __ip, __n_move);
2710        }
2711        else
2712        {
2713            __grow_by(__cap, __sz + __n - __cap, __sz, __ip, 0, __n);
2714            __p = _VSTD::__to_address(__get_long_pointer());
2715        }
2716        __sz += __n;
2717        __set_size(__sz);
2718        traits_type::assign(__p[__sz], value_type());
2719        for (__p += __ip; __first != __last; ++__p, ++__first)
2720            traits_type::assign(*__p, *__first);
2721    }
2722    return begin() + __ip;
2723}
2724
2725template <class _CharT, class _Traits, class _Allocator>
2726inline
2727basic_string<_CharT, _Traits, _Allocator>&
2728basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos1, const basic_string& __str)
2729{
2730    return insert(__pos1, __str.data(), __str.size());
2731}
2732
2733template <class _CharT, class _Traits, class _Allocator>
2734basic_string<_CharT, _Traits, _Allocator>&
2735basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos1, const basic_string& __str,
2736                                                  size_type __pos2, size_type __n)
2737{
2738    size_type __str_sz = __str.size();
2739    if (__pos2 > __str_sz)
2740        this->__throw_out_of_range();
2741    return insert(__pos1, __str.data() + __pos2, _VSTD::min(__n, __str_sz - __pos2));
2742}
2743
2744template <class _CharT, class _Traits, class _Allocator>
2745template <class _Tp>
2746typename enable_if
2747<
2748    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
2749    basic_string<_CharT, _Traits, _Allocator>&
2750>::type
2751basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos1, const _Tp& __t,
2752                                                  size_type __pos2, size_type __n)
2753{
2754    __self_view __sv = __t;
2755    size_type __str_sz = __sv.size();
2756    if (__pos2 > __str_sz)
2757        this->__throw_out_of_range();
2758    return insert(__pos1, __sv.data() + __pos2, _VSTD::min(__n, __str_sz - __pos2));
2759}
2760
2761template <class _CharT, class _Traits, class _Allocator>
2762basic_string<_CharT, _Traits, _Allocator>&
2763basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos, const value_type* __s)
2764{
2765    _LIBCPP_ASSERT(__s != nullptr, "string::insert received nullptr");
2766    return insert(__pos, __s, traits_type::length(__s));
2767}
2768
2769template <class _CharT, class _Traits, class _Allocator>
2770typename basic_string<_CharT, _Traits, _Allocator>::iterator
2771basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, value_type __c)
2772{
2773    size_type __ip = static_cast<size_type>(__pos - begin());
2774    size_type __sz = size();
2775    size_type __cap = capacity();
2776    value_type* __p;
2777    if (__cap == __sz)
2778    {
2779        __grow_by(__cap, 1, __sz, __ip, 0, 1);
2780        __p = _VSTD::__to_address(__get_long_pointer());
2781    }
2782    else
2783    {
2784        __p = _VSTD::__to_address(__get_pointer());
2785        size_type __n_move = __sz - __ip;
2786        if (__n_move != 0)
2787            traits_type::move(__p + __ip + 1, __p + __ip, __n_move);
2788    }
2789    traits_type::assign(__p[__ip], __c);
2790    traits_type::assign(__p[++__sz], value_type());
2791    __set_size(__sz);
2792    return begin() + static_cast<difference_type>(__ip);
2793}
2794
2795template <class _CharT, class _Traits, class _Allocator>
2796inline
2797typename basic_string<_CharT, _Traits, _Allocator>::iterator
2798basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, size_type __n, value_type __c)
2799{
2800#if _LIBCPP_DEBUG_LEVEL >= 2
2801    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__pos) == this,
2802        "string::insert(iterator, n, value) called with an iterator not"
2803        " referring to this string");
2804#endif
2805    difference_type __p = __pos - begin();
2806    insert(static_cast<size_type>(__p), __n, __c);
2807    return begin() + __p;
2808}
2809
2810// replace
2811
2812template <class _CharT, class _Traits, class _Allocator>
2813basic_string<_CharT, _Traits, _Allocator>&
2814basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __n1, const value_type* __s, size_type __n2)
2815    _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
2816{
2817    _LIBCPP_ASSERT(__n2 == 0 || __s != nullptr, "string::replace received nullptr");
2818    size_type __sz = size();
2819    if (__pos > __sz)
2820        this->__throw_out_of_range();
2821    __n1 = _VSTD::min(__n1, __sz - __pos);
2822    size_type __cap = capacity();
2823    if (__cap - __sz + __n1 >= __n2)
2824    {
2825        value_type* __p = _VSTD::__to_address(__get_pointer());
2826        if (__n1 != __n2)
2827        {
2828            size_type __n_move = __sz - __pos - __n1;
2829            if (__n_move != 0)
2830            {
2831                if (__n1 > __n2)
2832                {
2833                    traits_type::move(__p + __pos, __s, __n2);
2834                    traits_type::move(__p + __pos + __n2, __p + __pos + __n1, __n_move);
2835                    goto __finish;
2836                }
2837                if (__p + __pos < __s && __s < __p + __sz)
2838                {
2839                    if (__p + __pos + __n1 <= __s)
2840                        __s += __n2 - __n1;
2841                    else // __p + __pos < __s < __p + __pos + __n1
2842                    {
2843                        traits_type::move(__p + __pos, __s, __n1);
2844                        __pos += __n1;
2845                        __s += __n2;
2846                        __n2 -= __n1;
2847                        __n1 = 0;
2848                    }
2849                }
2850                traits_type::move(__p + __pos + __n2, __p + __pos + __n1, __n_move);
2851            }
2852        }
2853        traits_type::move(__p + __pos, __s, __n2);
2854__finish:
2855// __sz += __n2 - __n1; in this and the below function below can cause unsigned integer overflow,
2856// but this is a safe operation, so we disable the check.
2857        __sz += __n2 - __n1;
2858        __set_size(__sz);
2859        __invalidate_iterators_past(__sz);
2860        traits_type::assign(__p[__sz], value_type());
2861    }
2862    else
2863        __grow_by_and_replace(__cap, __sz - __n1 + __n2 - __cap, __sz, __pos, __n1, __n2, __s);
2864    return *this;
2865}
2866
2867template <class _CharT, class _Traits, class _Allocator>
2868basic_string<_CharT, _Traits, _Allocator>&
2869basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __n1, size_type __n2, value_type __c)
2870    _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
2871{
2872    size_type __sz = size();
2873    if (__pos > __sz)
2874        this->__throw_out_of_range();
2875    __n1 = _VSTD::min(__n1, __sz - __pos);
2876    size_type __cap = capacity();
2877    value_type* __p;
2878    if (__cap - __sz + __n1 >= __n2)
2879    {
2880        __p = _VSTD::__to_address(__get_pointer());
2881        if (__n1 != __n2)
2882        {
2883            size_type __n_move = __sz - __pos - __n1;
2884            if (__n_move != 0)
2885                traits_type::move(__p + __pos + __n2, __p + __pos + __n1, __n_move);
2886        }
2887    }
2888    else
2889    {
2890        __grow_by(__cap, __sz - __n1 + __n2 - __cap, __sz, __pos, __n1, __n2);
2891        __p = _VSTD::__to_address(__get_long_pointer());
2892    }
2893    traits_type::assign(__p + __pos, __n2, __c);
2894    __sz += __n2 - __n1;
2895    __set_size(__sz);
2896    __invalidate_iterators_past(__sz);
2897    traits_type::assign(__p[__sz], value_type());
2898    return *this;
2899}
2900
2901template <class _CharT, class _Traits, class _Allocator>
2902template<class _InputIterator>
2903typename enable_if
2904<
2905    __is_cpp17_input_iterator<_InputIterator>::value,
2906    basic_string<_CharT, _Traits, _Allocator>&
2907>::type
2908basic_string<_CharT, _Traits, _Allocator>::replace(const_iterator __i1, const_iterator __i2,
2909                                                   _InputIterator __j1, _InputIterator __j2)
2910{
2911    const basic_string __temp(__j1, __j2, __alloc());
2912    return this->replace(__i1, __i2, __temp);
2913}
2914
2915template <class _CharT, class _Traits, class _Allocator>
2916inline
2917basic_string<_CharT, _Traits, _Allocator>&
2918basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos1, size_type __n1, const basic_string& __str)
2919{
2920    return replace(__pos1, __n1, __str.data(), __str.size());
2921}
2922
2923template <class _CharT, class _Traits, class _Allocator>
2924basic_string<_CharT, _Traits, _Allocator>&
2925basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos1, size_type __n1, const basic_string& __str,
2926                                                   size_type __pos2, size_type __n2)
2927{
2928    size_type __str_sz = __str.size();
2929    if (__pos2 > __str_sz)
2930        this->__throw_out_of_range();
2931    return replace(__pos1, __n1, __str.data() + __pos2, _VSTD::min(__n2, __str_sz - __pos2));
2932}
2933
2934template <class _CharT, class _Traits, class _Allocator>
2935template <class _Tp>
2936typename enable_if
2937<
2938    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
2939    basic_string<_CharT, _Traits, _Allocator>&
2940>::type
2941basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos1, size_type __n1, const _Tp& __t,
2942                                                   size_type __pos2, size_type __n2)
2943{
2944    __self_view __sv = __t;
2945    size_type __str_sz = __sv.size();
2946    if (__pos2 > __str_sz)
2947        this->__throw_out_of_range();
2948    return replace(__pos1, __n1, __sv.data() + __pos2, _VSTD::min(__n2, __str_sz - __pos2));
2949}
2950
2951template <class _CharT, class _Traits, class _Allocator>
2952basic_string<_CharT, _Traits, _Allocator>&
2953basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __n1, const value_type* __s)
2954{
2955    _LIBCPP_ASSERT(__s != nullptr, "string::replace received nullptr");
2956    return replace(__pos, __n1, __s, traits_type::length(__s));
2957}
2958
2959template <class _CharT, class _Traits, class _Allocator>
2960inline
2961basic_string<_CharT, _Traits, _Allocator>&
2962basic_string<_CharT, _Traits, _Allocator>::replace(const_iterator __i1, const_iterator __i2, const basic_string& __str)
2963{
2964    return replace(static_cast<size_type>(__i1 - begin()), static_cast<size_type>(__i2 - __i1),
2965                   __str.data(), __str.size());
2966}
2967
2968template <class _CharT, class _Traits, class _Allocator>
2969inline
2970basic_string<_CharT, _Traits, _Allocator>&
2971basic_string<_CharT, _Traits, _Allocator>::replace(const_iterator __i1, const_iterator __i2, const value_type* __s, size_type __n)
2972{
2973    return replace(static_cast<size_type>(__i1 - begin()), static_cast<size_type>(__i2 - __i1), __s, __n);
2974}
2975
2976template <class _CharT, class _Traits, class _Allocator>
2977inline
2978basic_string<_CharT, _Traits, _Allocator>&
2979basic_string<_CharT, _Traits, _Allocator>::replace(const_iterator __i1, const_iterator __i2, const value_type* __s)
2980{
2981    return replace(static_cast<size_type>(__i1 - begin()), static_cast<size_type>(__i2 - __i1), __s);
2982}
2983
2984template <class _CharT, class _Traits, class _Allocator>
2985inline
2986basic_string<_CharT, _Traits, _Allocator>&
2987basic_string<_CharT, _Traits, _Allocator>::replace(const_iterator __i1, const_iterator __i2, size_type __n, value_type __c)
2988{
2989    return replace(static_cast<size_type>(__i1 - begin()), static_cast<size_type>(__i2 - __i1), __n, __c);
2990}
2991
2992// erase
2993
2994template <class _CharT, class _Traits, class _Allocator>
2995basic_string<_CharT, _Traits, _Allocator>&
2996basic_string<_CharT, _Traits, _Allocator>::erase(size_type __pos, size_type __n)
2997{
2998    size_type __sz = size();
2999    if (__pos > __sz)
3000        this->__throw_out_of_range();
3001    if (__n)
3002    {
3003        value_type* __p = _VSTD::__to_address(__get_pointer());
3004        __n = _VSTD::min(__n, __sz - __pos);
3005        size_type __n_move = __sz - __pos - __n;
3006        if (__n_move != 0)
3007            traits_type::move(__p + __pos, __p + __pos + __n, __n_move);
3008        __sz -= __n;
3009        __set_size(__sz);
3010        __invalidate_iterators_past(__sz);
3011        traits_type::assign(__p[__sz], value_type());
3012    }
3013    return *this;
3014}
3015
3016template <class _CharT, class _Traits, class _Allocator>
3017inline
3018typename basic_string<_CharT, _Traits, _Allocator>::iterator
3019basic_string<_CharT, _Traits, _Allocator>::erase(const_iterator __pos)
3020{
3021#if _LIBCPP_DEBUG_LEVEL >= 2
3022    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__pos) == this,
3023        "string::erase(iterator) called with an iterator not"
3024        " referring to this string");
3025#endif
3026    _LIBCPP_ASSERT(__pos != end(),
3027        "string::erase(iterator) called with a non-dereferenceable iterator");
3028    iterator __b = begin();
3029    size_type __r = static_cast<size_type>(__pos - __b);
3030    erase(__r, 1);
3031    return __b + static_cast<difference_type>(__r);
3032}
3033
3034template <class _CharT, class _Traits, class _Allocator>
3035inline
3036typename basic_string<_CharT, _Traits, _Allocator>::iterator
3037basic_string<_CharT, _Traits, _Allocator>::erase(const_iterator __first, const_iterator __last)
3038{
3039#if _LIBCPP_DEBUG_LEVEL >= 2
3040    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__first) == this,
3041        "string::erase(iterator,  iterator) called with an iterator not"
3042        " referring to this string");
3043#endif
3044    _LIBCPP_ASSERT(__first <= __last, "string::erase(first, last) called with invalid range");
3045    iterator __b = begin();
3046    size_type __r = static_cast<size_type>(__first - __b);
3047    erase(__r, static_cast<size_type>(__last - __first));
3048    return __b + static_cast<difference_type>(__r);
3049}
3050
3051template <class _CharT, class _Traits, class _Allocator>
3052inline
3053void
3054basic_string<_CharT, _Traits, _Allocator>::pop_back()
3055{
3056    _LIBCPP_ASSERT(!empty(), "string::pop_back(): string is already empty");
3057    size_type __sz;
3058    if (__is_long())
3059    {
3060        __sz = __get_long_size() - 1;
3061        __set_long_size(__sz);
3062        traits_type::assign(*(__get_long_pointer() + __sz), value_type());
3063    }
3064    else
3065    {
3066        __sz = __get_short_size() - 1;
3067        __set_short_size(__sz);
3068        traits_type::assign(*(__get_short_pointer() + __sz), value_type());
3069    }
3070    __invalidate_iterators_past(__sz);
3071}
3072
3073template <class _CharT, class _Traits, class _Allocator>
3074inline
3075void
3076basic_string<_CharT, _Traits, _Allocator>::clear() _NOEXCEPT
3077{
3078    __invalidate_all_iterators();
3079    if (__is_long())
3080    {
3081        traits_type::assign(*__get_long_pointer(), value_type());
3082        __set_long_size(0);
3083    }
3084    else
3085    {
3086        traits_type::assign(*__get_short_pointer(), value_type());
3087        __set_short_size(0);
3088    }
3089}
3090
3091template <class _CharT, class _Traits, class _Allocator>
3092inline
3093void
3094basic_string<_CharT, _Traits, _Allocator>::__erase_to_end(size_type __pos)
3095{
3096    if (__is_long())
3097    {
3098        traits_type::assign(*(__get_long_pointer() + __pos), value_type());
3099        __set_long_size(__pos);
3100    }
3101    else
3102    {
3103        traits_type::assign(*(__get_short_pointer() + __pos), value_type());
3104        __set_short_size(__pos);
3105    }
3106    __invalidate_iterators_past(__pos);
3107}
3108
3109template <class _CharT, class _Traits, class _Allocator>
3110void
3111basic_string<_CharT, _Traits, _Allocator>::resize(size_type __n, value_type __c)
3112{
3113    size_type __sz = size();
3114    if (__n > __sz)
3115        append(__n - __sz, __c);
3116    else
3117        __erase_to_end(__n);
3118}
3119
3120template <class _CharT, class _Traits, class _Allocator>
3121inline void
3122basic_string<_CharT, _Traits, _Allocator>::__resize_default_init(size_type __n)
3123{
3124    size_type __sz = size();
3125    if (__n > __sz) {
3126       __append_default_init(__n - __sz);
3127    } else
3128        __erase_to_end(__n);
3129}
3130
3131template <class _CharT, class _Traits, class _Allocator>
3132inline
3133typename basic_string<_CharT, _Traits, _Allocator>::size_type
3134basic_string<_CharT, _Traits, _Allocator>::max_size() const _NOEXCEPT
3135{
3136    size_type __m = __alloc_traits::max_size(__alloc());
3137#ifdef _LIBCPP_BIG_ENDIAN
3138    return (__m <= ~__long_mask ? __m : __m/2) - __alignment;
3139#else
3140    return __m - __alignment;
3141#endif
3142}
3143
3144template <class _CharT, class _Traits, class _Allocator>
3145void
3146basic_string<_CharT, _Traits, _Allocator>::reserve(size_type __res_arg)
3147{
3148    if (__res_arg > max_size())
3149        this->__throw_length_error();
3150    size_type __cap = capacity();
3151    size_type __sz = size();
3152    __res_arg = _VSTD::max(__res_arg, __sz);
3153    __res_arg = __recommend(__res_arg);
3154    if (__res_arg != __cap)
3155    {
3156        pointer __new_data, __p;
3157        bool __was_long, __now_long;
3158        if (__res_arg == __min_cap - 1)
3159        {
3160            __was_long = true;
3161            __now_long = false;
3162            __new_data = __get_short_pointer();
3163            __p = __get_long_pointer();
3164        }
3165        else
3166        {
3167            if (__res_arg > __cap)
3168                __new_data = __alloc_traits::allocate(__alloc(), __res_arg+1);
3169            else
3170            {
3171            #ifndef _LIBCPP_NO_EXCEPTIONS
3172                try
3173                {
3174            #endif  // _LIBCPP_NO_EXCEPTIONS
3175                    __new_data = __alloc_traits::allocate(__alloc(), __res_arg+1);
3176            #ifndef _LIBCPP_NO_EXCEPTIONS
3177                }
3178                catch (...)
3179                {
3180                    return;
3181                }
3182            #else  // _LIBCPP_NO_EXCEPTIONS
3183                if (__new_data == nullptr)
3184                    return;
3185            #endif  // _LIBCPP_NO_EXCEPTIONS
3186            }
3187            __now_long = true;
3188            __was_long = __is_long();
3189            __p = __get_pointer();
3190        }
3191        traits_type::copy(_VSTD::__to_address(__new_data),
3192                          _VSTD::__to_address(__p), size()+1);
3193        if (__was_long)
3194            __alloc_traits::deallocate(__alloc(), __p, __cap+1);
3195        if (__now_long)
3196        {
3197            __set_long_cap(__res_arg+1);
3198            __set_long_size(__sz);
3199            __set_long_pointer(__new_data);
3200        }
3201        else
3202            __set_short_size(__sz);
3203        __invalidate_all_iterators();
3204    }
3205}
3206
3207template <class _CharT, class _Traits, class _Allocator>
3208inline
3209typename basic_string<_CharT, _Traits, _Allocator>::const_reference
3210basic_string<_CharT, _Traits, _Allocator>::operator[](size_type __pos) const _NOEXCEPT
3211{
3212    _LIBCPP_ASSERT(__pos <= size(), "string index out of bounds");
3213    return *(data() + __pos);
3214}
3215
3216template <class _CharT, class _Traits, class _Allocator>
3217inline
3218typename basic_string<_CharT, _Traits, _Allocator>::reference
3219basic_string<_CharT, _Traits, _Allocator>::operator[](size_type __pos) _NOEXCEPT
3220{
3221    _LIBCPP_ASSERT(__pos <= size(), "string index out of bounds");
3222    return *(__get_pointer() + __pos);
3223}
3224
3225template <class _CharT, class _Traits, class _Allocator>
3226typename basic_string<_CharT, _Traits, _Allocator>::const_reference
3227basic_string<_CharT, _Traits, _Allocator>::at(size_type __n) const
3228{
3229    if (__n >= size())
3230        this->__throw_out_of_range();
3231    return (*this)[__n];
3232}
3233
3234template <class _CharT, class _Traits, class _Allocator>
3235typename basic_string<_CharT, _Traits, _Allocator>::reference
3236basic_string<_CharT, _Traits, _Allocator>::at(size_type __n)
3237{
3238    if (__n >= size())
3239        this->__throw_out_of_range();
3240    return (*this)[__n];
3241}
3242
3243template <class _CharT, class _Traits, class _Allocator>
3244inline
3245typename basic_string<_CharT, _Traits, _Allocator>::reference
3246basic_string<_CharT, _Traits, _Allocator>::front() _NOEXCEPT
3247{
3248    _LIBCPP_ASSERT(!empty(), "string::front(): string is empty");
3249    return *__get_pointer();
3250}
3251
3252template <class _CharT, class _Traits, class _Allocator>
3253inline
3254typename basic_string<_CharT, _Traits, _Allocator>::const_reference
3255basic_string<_CharT, _Traits, _Allocator>::front() const _NOEXCEPT
3256{
3257    _LIBCPP_ASSERT(!empty(), "string::front(): string is empty");
3258    return *data();
3259}
3260
3261template <class _CharT, class _Traits, class _Allocator>
3262inline
3263typename basic_string<_CharT, _Traits, _Allocator>::reference
3264basic_string<_CharT, _Traits, _Allocator>::back() _NOEXCEPT
3265{
3266    _LIBCPP_ASSERT(!empty(), "string::back(): string is empty");
3267    return *(__get_pointer() + size() - 1);
3268}
3269
3270template <class _CharT, class _Traits, class _Allocator>
3271inline
3272typename basic_string<_CharT, _Traits, _Allocator>::const_reference
3273basic_string<_CharT, _Traits, _Allocator>::back() const _NOEXCEPT
3274{
3275    _LIBCPP_ASSERT(!empty(), "string::back(): string is empty");
3276    return *(data() + size() - 1);
3277}
3278
3279template <class _CharT, class _Traits, class _Allocator>
3280typename basic_string<_CharT, _Traits, _Allocator>::size_type
3281basic_string<_CharT, _Traits, _Allocator>::copy(value_type* __s, size_type __n, size_type __pos) const
3282{
3283    size_type __sz = size();
3284    if (__pos > __sz)
3285        this->__throw_out_of_range();
3286    size_type __rlen = _VSTD::min(__n, __sz - __pos);
3287    traits_type::copy(__s, data() + __pos, __rlen);
3288    return __rlen;
3289}
3290
3291template <class _CharT, class _Traits, class _Allocator>
3292inline
3293basic_string<_CharT, _Traits, _Allocator>
3294basic_string<_CharT, _Traits, _Allocator>::substr(size_type __pos, size_type __n) const
3295{
3296    return basic_string(*this, __pos, __n, __alloc());
3297}
3298
3299template <class _CharT, class _Traits, class _Allocator>
3300inline
3301void
3302basic_string<_CharT, _Traits, _Allocator>::swap(basic_string& __str)
3303#if _LIBCPP_STD_VER >= 14
3304        _NOEXCEPT
3305#else
3306        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value ||
3307                    __is_nothrow_swappable<allocator_type>::value)
3308#endif
3309{
3310#if _LIBCPP_DEBUG_LEVEL >= 2
3311    if (!__is_long())
3312        __get_db()->__invalidate_all(this);
3313    if (!__str.__is_long())
3314        __get_db()->__invalidate_all(&__str);
3315    __get_db()->swap(this, &__str);
3316#endif
3317    _LIBCPP_ASSERT(
3318        __alloc_traits::propagate_on_container_swap::value ||
3319        __alloc_traits::is_always_equal::value ||
3320        __alloc() == __str.__alloc(), "swapping non-equal allocators");
3321    _VSTD::swap(__r_.first(), __str.__r_.first());
3322    __swap_allocator(__alloc(), __str.__alloc());
3323}
3324
3325// find
3326
3327template <class _Traits>
3328struct _LIBCPP_HIDDEN __traits_eq
3329{
3330    typedef typename _Traits::char_type char_type;
3331    _LIBCPP_INLINE_VISIBILITY
3332    bool operator()(const char_type& __x, const char_type& __y) _NOEXCEPT
3333        {return _Traits::eq(__x, __y);}
3334};
3335
3336template<class _CharT, class _Traits, class _Allocator>
3337typename basic_string<_CharT, _Traits, _Allocator>::size_type
3338basic_string<_CharT, _Traits, _Allocator>::find(const value_type* __s,
3339                                                size_type __pos,
3340                                                size_type __n) const _NOEXCEPT
3341{
3342    _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find(): received nullptr");
3343    return __str_find<value_type, size_type, traits_type, npos>
3344        (data(), size(), __s, __pos, __n);
3345}
3346
3347template<class _CharT, class _Traits, class _Allocator>
3348inline
3349typename basic_string<_CharT, _Traits, _Allocator>::size_type
3350basic_string<_CharT, _Traits, _Allocator>::find(const basic_string& __str,
3351                                                size_type __pos) const _NOEXCEPT
3352{
3353    return __str_find<value_type, size_type, traits_type, npos>
3354        (data(), size(), __str.data(), __pos, __str.size());
3355}
3356
3357template<class _CharT, class _Traits, class _Allocator>
3358template <class _Tp>
3359typename enable_if
3360<
3361    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
3362    typename basic_string<_CharT, _Traits, _Allocator>::size_type
3363>::type
3364basic_string<_CharT, _Traits, _Allocator>::find(const _Tp &__t,
3365                                                size_type __pos) const
3366{
3367    __self_view __sv = __t;
3368    return __str_find<value_type, size_type, traits_type, npos>
3369        (data(), size(), __sv.data(), __pos, __sv.size());
3370}
3371
3372template<class _CharT, class _Traits, class _Allocator>
3373inline
3374typename basic_string<_CharT, _Traits, _Allocator>::size_type
3375basic_string<_CharT, _Traits, _Allocator>::find(const value_type* __s,
3376                                                size_type __pos) const _NOEXCEPT
3377{
3378    _LIBCPP_ASSERT(__s != nullptr, "string::find(): received nullptr");
3379    return __str_find<value_type, size_type, traits_type, npos>
3380        (data(), size(), __s, __pos, traits_type::length(__s));
3381}
3382
3383template<class _CharT, class _Traits, class _Allocator>
3384typename basic_string<_CharT, _Traits, _Allocator>::size_type
3385basic_string<_CharT, _Traits, _Allocator>::find(value_type __c,
3386                                                size_type __pos) const _NOEXCEPT
3387{
3388    return __str_find<value_type, size_type, traits_type, npos>
3389        (data(), size(), __c, __pos);
3390}
3391
3392// rfind
3393
3394template<class _CharT, class _Traits, class _Allocator>
3395typename basic_string<_CharT, _Traits, _Allocator>::size_type
3396basic_string<_CharT, _Traits, _Allocator>::rfind(const value_type* __s,
3397                                                 size_type __pos,
3398                                                 size_type __n) const _NOEXCEPT
3399{
3400    _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::rfind(): received nullptr");
3401    return __str_rfind<value_type, size_type, traits_type, npos>
3402        (data(), size(), __s, __pos, __n);
3403}
3404
3405template<class _CharT, class _Traits, class _Allocator>
3406inline
3407typename basic_string<_CharT, _Traits, _Allocator>::size_type
3408basic_string<_CharT, _Traits, _Allocator>::rfind(const basic_string& __str,
3409                                                 size_type __pos) const _NOEXCEPT
3410{
3411    return __str_rfind<value_type, size_type, traits_type, npos>
3412        (data(), size(), __str.data(), __pos, __str.size());
3413}
3414
3415template<class _CharT, class _Traits, class _Allocator>
3416template <class _Tp>
3417typename enable_if
3418<
3419    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
3420    typename basic_string<_CharT, _Traits, _Allocator>::size_type
3421>::type
3422basic_string<_CharT, _Traits, _Allocator>::rfind(const _Tp& __t,
3423                                                size_type __pos) const
3424{
3425    __self_view __sv = __t;
3426    return __str_rfind<value_type, size_type, traits_type, npos>
3427        (data(), size(), __sv.data(), __pos, __sv.size());
3428}
3429
3430template<class _CharT, class _Traits, class _Allocator>
3431inline
3432typename basic_string<_CharT, _Traits, _Allocator>::size_type
3433basic_string<_CharT, _Traits, _Allocator>::rfind(const value_type* __s,
3434                                                 size_type __pos) const _NOEXCEPT
3435{
3436    _LIBCPP_ASSERT(__s != nullptr, "string::rfind(): received nullptr");
3437    return __str_rfind<value_type, size_type, traits_type, npos>
3438        (data(), size(), __s, __pos, traits_type::length(__s));
3439}
3440
3441template<class _CharT, class _Traits, class _Allocator>
3442typename basic_string<_CharT, _Traits, _Allocator>::size_type
3443basic_string<_CharT, _Traits, _Allocator>::rfind(value_type __c,
3444                                                 size_type __pos) const _NOEXCEPT
3445{
3446    return __str_rfind<value_type, size_type, traits_type, npos>
3447        (data(), size(), __c, __pos);
3448}
3449
3450// find_first_of
3451
3452template<class _CharT, class _Traits, class _Allocator>
3453typename basic_string<_CharT, _Traits, _Allocator>::size_type
3454basic_string<_CharT, _Traits, _Allocator>::find_first_of(const value_type* __s,
3455                                                         size_type __pos,
3456                                                         size_type __n) const _NOEXCEPT
3457{
3458    _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find_first_of(): received nullptr");
3459    return __str_find_first_of<value_type, size_type, traits_type, npos>
3460        (data(), size(), __s, __pos, __n);
3461}
3462
3463template<class _CharT, class _Traits, class _Allocator>
3464inline
3465typename basic_string<_CharT, _Traits, _Allocator>::size_type
3466basic_string<_CharT, _Traits, _Allocator>::find_first_of(const basic_string& __str,
3467                                                         size_type __pos) const _NOEXCEPT
3468{
3469    return __str_find_first_of<value_type, size_type, traits_type, npos>
3470        (data(), size(), __str.data(), __pos, __str.size());
3471}
3472
3473template<class _CharT, class _Traits, class _Allocator>
3474template <class _Tp>
3475typename enable_if
3476<
3477    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
3478    typename basic_string<_CharT, _Traits, _Allocator>::size_type
3479>::type
3480basic_string<_CharT, _Traits, _Allocator>::find_first_of(const _Tp& __t,
3481                                                size_type __pos) const
3482{
3483    __self_view __sv = __t;
3484    return __str_find_first_of<value_type, size_type, traits_type, npos>
3485        (data(), size(), __sv.data(), __pos, __sv.size());
3486}
3487
3488template<class _CharT, class _Traits, class _Allocator>
3489inline
3490typename basic_string<_CharT, _Traits, _Allocator>::size_type
3491basic_string<_CharT, _Traits, _Allocator>::find_first_of(const value_type* __s,
3492                                                         size_type __pos) const _NOEXCEPT
3493{
3494    _LIBCPP_ASSERT(__s != nullptr, "string::find_first_of(): received nullptr");
3495    return __str_find_first_of<value_type, size_type, traits_type, npos>
3496        (data(), size(), __s, __pos, traits_type::length(__s));
3497}
3498
3499template<class _CharT, class _Traits, class _Allocator>
3500inline
3501typename basic_string<_CharT, _Traits, _Allocator>::size_type
3502basic_string<_CharT, _Traits, _Allocator>::find_first_of(value_type __c,
3503                                                         size_type __pos) const _NOEXCEPT
3504{
3505    return find(__c, __pos);
3506}
3507
3508// find_last_of
3509
3510template<class _CharT, class _Traits, class _Allocator>
3511typename basic_string<_CharT, _Traits, _Allocator>::size_type
3512basic_string<_CharT, _Traits, _Allocator>::find_last_of(const value_type* __s,
3513                                                        size_type __pos,
3514                                                        size_type __n) const _NOEXCEPT
3515{
3516    _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find_last_of(): received nullptr");
3517    return __str_find_last_of<value_type, size_type, traits_type, npos>
3518        (data(), size(), __s, __pos, __n);
3519}
3520
3521template<class _CharT, class _Traits, class _Allocator>
3522inline
3523typename basic_string<_CharT, _Traits, _Allocator>::size_type
3524basic_string<_CharT, _Traits, _Allocator>::find_last_of(const basic_string& __str,
3525                                                        size_type __pos) const _NOEXCEPT
3526{
3527    return __str_find_last_of<value_type, size_type, traits_type, npos>
3528        (data(), size(), __str.data(), __pos, __str.size());
3529}
3530
3531template<class _CharT, class _Traits, class _Allocator>
3532template <class _Tp>
3533typename enable_if
3534<
3535    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
3536    typename basic_string<_CharT, _Traits, _Allocator>::size_type
3537>::type
3538basic_string<_CharT, _Traits, _Allocator>::find_last_of(const _Tp& __t,
3539                                                size_type __pos) const
3540{
3541    __self_view __sv = __t;
3542    return __str_find_last_of<value_type, size_type, traits_type, npos>
3543        (data(), size(), __sv.data(), __pos, __sv.size());
3544}
3545
3546template<class _CharT, class _Traits, class _Allocator>
3547inline
3548typename basic_string<_CharT, _Traits, _Allocator>::size_type
3549basic_string<_CharT, _Traits, _Allocator>::find_last_of(const value_type* __s,
3550                                                        size_type __pos) const _NOEXCEPT
3551{
3552    _LIBCPP_ASSERT(__s != nullptr, "string::find_last_of(): received nullptr");
3553    return __str_find_last_of<value_type, size_type, traits_type, npos>
3554        (data(), size(), __s, __pos, traits_type::length(__s));
3555}
3556
3557template<class _CharT, class _Traits, class _Allocator>
3558inline
3559typename basic_string<_CharT, _Traits, _Allocator>::size_type
3560basic_string<_CharT, _Traits, _Allocator>::find_last_of(value_type __c,
3561                                                        size_type __pos) const _NOEXCEPT
3562{
3563    return rfind(__c, __pos);
3564}
3565
3566// find_first_not_of
3567
3568template<class _CharT, class _Traits, class _Allocator>
3569typename basic_string<_CharT, _Traits, _Allocator>::size_type
3570basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(const value_type* __s,
3571                                                             size_type __pos,
3572                                                             size_type __n) const _NOEXCEPT
3573{
3574    _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find_first_not_of(): received nullptr");
3575    return __str_find_first_not_of<value_type, size_type, traits_type, npos>
3576        (data(), size(), __s, __pos, __n);
3577}
3578
3579template<class _CharT, class _Traits, class _Allocator>
3580inline
3581typename basic_string<_CharT, _Traits, _Allocator>::size_type
3582basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(const basic_string& __str,
3583                                                             size_type __pos) const _NOEXCEPT
3584{
3585    return __str_find_first_not_of<value_type, size_type, traits_type, npos>
3586        (data(), size(), __str.data(), __pos, __str.size());
3587}
3588
3589template<class _CharT, class _Traits, class _Allocator>
3590template <class _Tp>
3591typename enable_if
3592<
3593    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
3594    typename basic_string<_CharT, _Traits, _Allocator>::size_type
3595>::type
3596basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(const _Tp& __t,
3597                                                size_type __pos) const
3598{
3599    __self_view __sv = __t;
3600    return __str_find_first_not_of<value_type, size_type, traits_type, npos>
3601        (data(), size(), __sv.data(), __pos, __sv.size());
3602}
3603
3604template<class _CharT, class _Traits, class _Allocator>
3605inline
3606typename basic_string<_CharT, _Traits, _Allocator>::size_type
3607basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(const value_type* __s,
3608                                                             size_type __pos) const _NOEXCEPT
3609{
3610    _LIBCPP_ASSERT(__s != nullptr, "string::find_first_not_of(): received nullptr");
3611    return __str_find_first_not_of<value_type, size_type, traits_type, npos>
3612        (data(), size(), __s, __pos, traits_type::length(__s));
3613}
3614
3615template<class _CharT, class _Traits, class _Allocator>
3616inline
3617typename basic_string<_CharT, _Traits, _Allocator>::size_type
3618basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(value_type __c,
3619                                                             size_type __pos) const _NOEXCEPT
3620{
3621    return __str_find_first_not_of<value_type, size_type, traits_type, npos>
3622        (data(), size(), __c, __pos);
3623}
3624
3625// find_last_not_of
3626
3627template<class _CharT, class _Traits, class _Allocator>
3628typename basic_string<_CharT, _Traits, _Allocator>::size_type
3629basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(const value_type* __s,
3630                                                            size_type __pos,
3631                                                            size_type __n) const _NOEXCEPT
3632{
3633    _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find_last_not_of(): received nullptr");
3634    return __str_find_last_not_of<value_type, size_type, traits_type, npos>
3635        (data(), size(), __s, __pos, __n);
3636}
3637
3638template<class _CharT, class _Traits, class _Allocator>
3639inline
3640typename basic_string<_CharT, _Traits, _Allocator>::size_type
3641basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(const basic_string& __str,
3642                                                            size_type __pos) const _NOEXCEPT
3643{
3644    return __str_find_last_not_of<value_type, size_type, traits_type, npos>
3645        (data(), size(), __str.data(), __pos, __str.size());
3646}
3647
3648template<class _CharT, class _Traits, class _Allocator>
3649template <class _Tp>
3650typename enable_if
3651<
3652    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
3653    typename basic_string<_CharT, _Traits, _Allocator>::size_type
3654>::type
3655basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(const _Tp& __t,
3656                                                size_type __pos) const
3657{
3658    __self_view __sv = __t;
3659    return __str_find_last_not_of<value_type, size_type, traits_type, npos>
3660        (data(), size(), __sv.data(), __pos, __sv.size());
3661}
3662
3663template<class _CharT, class _Traits, class _Allocator>
3664inline
3665typename basic_string<_CharT, _Traits, _Allocator>::size_type
3666basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(const value_type* __s,
3667                                                            size_type __pos) const _NOEXCEPT
3668{
3669    _LIBCPP_ASSERT(__s != nullptr, "string::find_last_not_of(): received nullptr");
3670    return __str_find_last_not_of<value_type, size_type, traits_type, npos>
3671        (data(), size(), __s, __pos, traits_type::length(__s));
3672}
3673
3674template<class _CharT, class _Traits, class _Allocator>
3675inline
3676typename basic_string<_CharT, _Traits, _Allocator>::size_type
3677basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(value_type __c,
3678                                                            size_type __pos) const _NOEXCEPT
3679{
3680    return __str_find_last_not_of<value_type, size_type, traits_type, npos>
3681        (data(), size(), __c, __pos);
3682}
3683
3684// compare
3685
3686template <class _CharT, class _Traits, class _Allocator>
3687template <class _Tp>
3688typename enable_if
3689<
3690    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
3691    int
3692>::type
3693basic_string<_CharT, _Traits, _Allocator>::compare(const _Tp& __t) const
3694{
3695    __self_view __sv = __t;
3696    size_t __lhs_sz = size();
3697    size_t __rhs_sz = __sv.size();
3698    int __result = traits_type::compare(data(), __sv.data(),
3699                                        _VSTD::min(__lhs_sz, __rhs_sz));
3700    if (__result != 0)
3701        return __result;
3702    if (__lhs_sz < __rhs_sz)
3703        return -1;
3704    if (__lhs_sz > __rhs_sz)
3705        return 1;
3706    return 0;
3707}
3708
3709template <class _CharT, class _Traits, class _Allocator>
3710inline
3711int
3712basic_string<_CharT, _Traits, _Allocator>::compare(const basic_string& __str) const _NOEXCEPT
3713{
3714    return compare(__self_view(__str));
3715}
3716
3717template <class _CharT, class _Traits, class _Allocator>
3718int
3719basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
3720                                                   size_type __n1,
3721                                                   const value_type* __s,
3722                                                   size_type __n2) const
3723{
3724    _LIBCPP_ASSERT(__n2 == 0 || __s != nullptr, "string::compare(): received nullptr");
3725    size_type __sz = size();
3726    if (__pos1 > __sz || __n2 == npos)
3727        this->__throw_out_of_range();
3728    size_type __rlen = _VSTD::min(__n1, __sz - __pos1);
3729    int __r = traits_type::compare(data() + __pos1, __s, _VSTD::min(__rlen, __n2));
3730    if (__r == 0)
3731    {
3732        if (__rlen < __n2)
3733            __r = -1;
3734        else if (__rlen > __n2)
3735            __r = 1;
3736    }
3737    return __r;
3738}
3739
3740template <class _CharT, class _Traits, class _Allocator>
3741template <class _Tp>
3742typename enable_if
3743<
3744    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
3745    int
3746>::type
3747basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
3748                                                   size_type __n1,
3749                                                   const _Tp& __t) const
3750{
3751    __self_view __sv = __t;
3752    return compare(__pos1, __n1, __sv.data(), __sv.size());
3753}
3754
3755template <class _CharT, class _Traits, class _Allocator>
3756inline
3757int
3758basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
3759                                                   size_type __n1,
3760                                                   const basic_string& __str) const
3761{
3762    return compare(__pos1, __n1, __str.data(), __str.size());
3763}
3764
3765template <class _CharT, class _Traits, class _Allocator>
3766template <class _Tp>
3767typename enable_if
3768<
3769    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
3770    int
3771>::type
3772basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
3773                                                   size_type __n1,
3774                                                   const _Tp& __t,
3775                                                   size_type __pos2,
3776                                                   size_type __n2) const
3777{
3778    __self_view __sv = __t;
3779    return __self_view(*this).substr(__pos1, __n1).compare(__sv.substr(__pos2, __n2));
3780}
3781
3782template <class _CharT, class _Traits, class _Allocator>
3783int
3784basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
3785                                                   size_type __n1,
3786                                                   const basic_string& __str,
3787                                                   size_type __pos2,
3788                                                   size_type __n2) const
3789{
3790        return compare(__pos1, __n1, __self_view(__str), __pos2, __n2);
3791}
3792
3793template <class _CharT, class _Traits, class _Allocator>
3794int
3795basic_string<_CharT, _Traits, _Allocator>::compare(const value_type* __s) const _NOEXCEPT
3796{
3797    _LIBCPP_ASSERT(__s != nullptr, "string::compare(): received nullptr");
3798    return compare(0, npos, __s, traits_type::length(__s));
3799}
3800
3801template <class _CharT, class _Traits, class _Allocator>
3802int
3803basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
3804                                                   size_type __n1,
3805                                                   const value_type* __s) const
3806{
3807    _LIBCPP_ASSERT(__s != nullptr, "string::compare(): received nullptr");
3808    return compare(__pos1, __n1, __s, traits_type::length(__s));
3809}
3810
3811// __invariants
3812
3813template<class _CharT, class _Traits, class _Allocator>
3814inline
3815bool
3816basic_string<_CharT, _Traits, _Allocator>::__invariants() const
3817{
3818    if (size() > capacity())
3819        return false;
3820    if (capacity() < __min_cap - 1)
3821        return false;
3822    if (data() == 0)
3823        return false;
3824    if (data()[size()] != value_type(0))
3825        return false;
3826    return true;
3827}
3828
3829// __clear_and_shrink
3830
3831template<class _CharT, class _Traits, class _Allocator>
3832inline
3833void
3834basic_string<_CharT, _Traits, _Allocator>::__clear_and_shrink() _NOEXCEPT
3835{
3836    clear();
3837    if(__is_long())
3838    {
3839        __alloc_traits::deallocate(__alloc(), __get_long_pointer(), capacity() + 1);
3840        __set_long_cap(0);
3841        __set_short_size(0);
3842    }
3843}
3844
3845// operator==
3846
3847template<class _CharT, class _Traits, class _Allocator>
3848inline _LIBCPP_INLINE_VISIBILITY
3849bool
3850operator==(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
3851           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
3852{
3853    size_t __lhs_sz = __lhs.size();
3854    return __lhs_sz == __rhs.size() && _Traits::compare(__lhs.data(),
3855                                                        __rhs.data(),
3856                                                        __lhs_sz) == 0;
3857}
3858
3859template<class _Allocator>
3860inline _LIBCPP_INLINE_VISIBILITY
3861bool
3862operator==(const basic_string<char, char_traits<char>, _Allocator>& __lhs,
3863           const basic_string<char, char_traits<char>, _Allocator>& __rhs) _NOEXCEPT
3864{
3865    size_t __lhs_sz = __lhs.size();
3866    if (__lhs_sz != __rhs.size())
3867        return false;
3868    const char* __lp = __lhs.data();
3869    const char* __rp = __rhs.data();
3870    if (__lhs.__is_long())
3871        return char_traits<char>::compare(__lp, __rp, __lhs_sz) == 0;
3872    for (; __lhs_sz != 0; --__lhs_sz, ++__lp, ++__rp)
3873        if (*__lp != *__rp)
3874            return false;
3875    return true;
3876}
3877
3878template<class _CharT, class _Traits, class _Allocator>
3879inline _LIBCPP_INLINE_VISIBILITY
3880bool
3881operator==(const _CharT* __lhs,
3882           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
3883{
3884    typedef basic_string<_CharT, _Traits, _Allocator> _String;
3885    _LIBCPP_ASSERT(__lhs != nullptr, "operator==(char*, basic_string): received nullptr");
3886    size_t __lhs_len = _Traits::length(__lhs);
3887    if (__lhs_len != __rhs.size()) return false;
3888    return __rhs.compare(0, _String::npos, __lhs, __lhs_len) == 0;
3889}
3890
3891template<class _CharT, class _Traits, class _Allocator>
3892inline _LIBCPP_INLINE_VISIBILITY
3893bool
3894operator==(const basic_string<_CharT,_Traits,_Allocator>& __lhs,
3895           const _CharT* __rhs) _NOEXCEPT
3896{
3897    typedef basic_string<_CharT, _Traits, _Allocator> _String;
3898    _LIBCPP_ASSERT(__rhs != nullptr, "operator==(basic_string, char*): received nullptr");
3899    size_t __rhs_len = _Traits::length(__rhs);
3900    if (__rhs_len != __lhs.size()) return false;
3901    return __lhs.compare(0, _String::npos, __rhs, __rhs_len) == 0;
3902}
3903
3904template<class _CharT, class _Traits, class _Allocator>
3905inline _LIBCPP_INLINE_VISIBILITY
3906bool
3907operator!=(const basic_string<_CharT,_Traits,_Allocator>& __lhs,
3908           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
3909{
3910    return !(__lhs == __rhs);
3911}
3912
3913template<class _CharT, class _Traits, class _Allocator>
3914inline _LIBCPP_INLINE_VISIBILITY
3915bool
3916operator!=(const _CharT* __lhs,
3917           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
3918{
3919    return !(__lhs == __rhs);
3920}
3921
3922template<class _CharT, class _Traits, class _Allocator>
3923inline _LIBCPP_INLINE_VISIBILITY
3924bool
3925operator!=(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
3926           const _CharT* __rhs) _NOEXCEPT
3927{
3928    return !(__lhs == __rhs);
3929}
3930
3931// operator<
3932
3933template<class _CharT, class _Traits, class _Allocator>
3934inline _LIBCPP_INLINE_VISIBILITY
3935bool
3936operator< (const basic_string<_CharT, _Traits, _Allocator>& __lhs,
3937           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
3938{
3939    return __lhs.compare(__rhs) < 0;
3940}
3941
3942template<class _CharT, class _Traits, class _Allocator>
3943inline _LIBCPP_INLINE_VISIBILITY
3944bool
3945operator< (const basic_string<_CharT, _Traits, _Allocator>& __lhs,
3946           const _CharT* __rhs) _NOEXCEPT
3947{
3948    return __lhs.compare(__rhs) < 0;
3949}
3950
3951template<class _CharT, class _Traits, class _Allocator>
3952inline _LIBCPP_INLINE_VISIBILITY
3953bool
3954operator< (const _CharT* __lhs,
3955           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
3956{
3957    return __rhs.compare(__lhs) > 0;
3958}
3959
3960// operator>
3961
3962template<class _CharT, class _Traits, class _Allocator>
3963inline _LIBCPP_INLINE_VISIBILITY
3964bool
3965operator> (const basic_string<_CharT, _Traits, _Allocator>& __lhs,
3966           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
3967{
3968    return __rhs < __lhs;
3969}
3970
3971template<class _CharT, class _Traits, class _Allocator>
3972inline _LIBCPP_INLINE_VISIBILITY
3973bool
3974operator> (const basic_string<_CharT, _Traits, _Allocator>& __lhs,
3975           const _CharT* __rhs) _NOEXCEPT
3976{
3977    return __rhs < __lhs;
3978}
3979
3980template<class _CharT, class _Traits, class _Allocator>
3981inline _LIBCPP_INLINE_VISIBILITY
3982bool
3983operator> (const _CharT* __lhs,
3984           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
3985{
3986    return __rhs < __lhs;
3987}
3988
3989// operator<=
3990
3991template<class _CharT, class _Traits, class _Allocator>
3992inline _LIBCPP_INLINE_VISIBILITY
3993bool
3994operator<=(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
3995           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
3996{
3997    return !(__rhs < __lhs);
3998}
3999
4000template<class _CharT, class _Traits, class _Allocator>
4001inline _LIBCPP_INLINE_VISIBILITY
4002bool
4003operator<=(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
4004           const _CharT* __rhs) _NOEXCEPT
4005{
4006    return !(__rhs < __lhs);
4007}
4008
4009template<class _CharT, class _Traits, class _Allocator>
4010inline _LIBCPP_INLINE_VISIBILITY
4011bool
4012operator<=(const _CharT* __lhs,
4013           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
4014{
4015    return !(__rhs < __lhs);
4016}
4017
4018// operator>=
4019
4020template<class _CharT, class _Traits, class _Allocator>
4021inline _LIBCPP_INLINE_VISIBILITY
4022bool
4023operator>=(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
4024           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
4025{
4026    return !(__lhs < __rhs);
4027}
4028
4029template<class _CharT, class _Traits, class _Allocator>
4030inline _LIBCPP_INLINE_VISIBILITY
4031bool
4032operator>=(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
4033           const _CharT* __rhs) _NOEXCEPT
4034{
4035    return !(__lhs < __rhs);
4036}
4037
4038template<class _CharT, class _Traits, class _Allocator>
4039inline _LIBCPP_INLINE_VISIBILITY
4040bool
4041operator>=(const _CharT* __lhs,
4042           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
4043{
4044    return !(__lhs < __rhs);
4045}
4046
4047// operator +
4048
4049template<class _CharT, class _Traits, class _Allocator>
4050basic_string<_CharT, _Traits, _Allocator>
4051operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
4052          const basic_string<_CharT, _Traits, _Allocator>& __rhs)
4053{
4054    basic_string<_CharT, _Traits, _Allocator> __r(__lhs.get_allocator());
4055    typename basic_string<_CharT, _Traits, _Allocator>::size_type __lhs_sz = __lhs.size();
4056    typename basic_string<_CharT, _Traits, _Allocator>::size_type __rhs_sz = __rhs.size();
4057    __r.__init(__lhs.data(), __lhs_sz, __lhs_sz + __rhs_sz);
4058    __r.append(__rhs.data(), __rhs_sz);
4059    return __r;
4060}
4061
4062template<class _CharT, class _Traits, class _Allocator>
4063basic_string<_CharT, _Traits, _Allocator>
4064operator+(const _CharT* __lhs , const basic_string<_CharT,_Traits,_Allocator>& __rhs)
4065{
4066    basic_string<_CharT, _Traits, _Allocator> __r(__rhs.get_allocator());
4067    typename basic_string<_CharT, _Traits, _Allocator>::size_type __lhs_sz = _Traits::length(__lhs);
4068    typename basic_string<_CharT, _Traits, _Allocator>::size_type __rhs_sz = __rhs.size();
4069    __r.__init(__lhs, __lhs_sz, __lhs_sz + __rhs_sz);
4070    __r.append(__rhs.data(), __rhs_sz);
4071    return __r;
4072}
4073
4074template<class _CharT, class _Traits, class _Allocator>
4075basic_string<_CharT, _Traits, _Allocator>
4076operator+(_CharT __lhs, const basic_string<_CharT,_Traits,_Allocator>& __rhs)
4077{
4078    basic_string<_CharT, _Traits, _Allocator> __r(__rhs.get_allocator());
4079    typename basic_string<_CharT, _Traits, _Allocator>::size_type __rhs_sz = __rhs.size();
4080    __r.__init(&__lhs, 1, 1 + __rhs_sz);
4081    __r.append(__rhs.data(), __rhs_sz);
4082    return __r;
4083}
4084
4085template<class _CharT, class _Traits, class _Allocator>
4086inline
4087basic_string<_CharT, _Traits, _Allocator>
4088operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs, const _CharT* __rhs)
4089{
4090    basic_string<_CharT, _Traits, _Allocator> __r(__lhs.get_allocator());
4091    typename basic_string<_CharT, _Traits, _Allocator>::size_type __lhs_sz = __lhs.size();
4092    typename basic_string<_CharT, _Traits, _Allocator>::size_type __rhs_sz = _Traits::length(__rhs);
4093    __r.__init(__lhs.data(), __lhs_sz, __lhs_sz + __rhs_sz);
4094    __r.append(__rhs, __rhs_sz);
4095    return __r;
4096}
4097
4098template<class _CharT, class _Traits, class _Allocator>
4099basic_string<_CharT, _Traits, _Allocator>
4100operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs, _CharT __rhs)
4101{
4102    basic_string<_CharT, _Traits, _Allocator> __r(__lhs.get_allocator());
4103    typename basic_string<_CharT, _Traits, _Allocator>::size_type __lhs_sz = __lhs.size();
4104    __r.__init(__lhs.data(), __lhs_sz, __lhs_sz + 1);
4105    __r.push_back(__rhs);
4106    return __r;
4107}
4108
4109#ifndef _LIBCPP_CXX03_LANG
4110
4111template<class _CharT, class _Traits, class _Allocator>
4112inline _LIBCPP_INLINE_VISIBILITY
4113basic_string<_CharT, _Traits, _Allocator>
4114operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, const basic_string<_CharT, _Traits, _Allocator>& __rhs)
4115{
4116    return _VSTD::move(__lhs.append(__rhs));
4117}
4118
4119template<class _CharT, class _Traits, class _Allocator>
4120inline _LIBCPP_INLINE_VISIBILITY
4121basic_string<_CharT, _Traits, _Allocator>
4122operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs, basic_string<_CharT, _Traits, _Allocator>&& __rhs)
4123{
4124    return _VSTD::move(__rhs.insert(0, __lhs));
4125}
4126
4127template<class _CharT, class _Traits, class _Allocator>
4128inline _LIBCPP_INLINE_VISIBILITY
4129basic_string<_CharT, _Traits, _Allocator>
4130operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, basic_string<_CharT, _Traits, _Allocator>&& __rhs)
4131{
4132    return _VSTD::move(__lhs.append(__rhs));
4133}
4134
4135template<class _CharT, class _Traits, class _Allocator>
4136inline _LIBCPP_INLINE_VISIBILITY
4137basic_string<_CharT, _Traits, _Allocator>
4138operator+(const _CharT* __lhs , basic_string<_CharT,_Traits,_Allocator>&& __rhs)
4139{
4140    return _VSTD::move(__rhs.insert(0, __lhs));
4141}
4142
4143template<class _CharT, class _Traits, class _Allocator>
4144inline _LIBCPP_INLINE_VISIBILITY
4145basic_string<_CharT, _Traits, _Allocator>
4146operator+(_CharT __lhs, basic_string<_CharT,_Traits,_Allocator>&& __rhs)
4147{
4148    __rhs.insert(__rhs.begin(), __lhs);
4149    return _VSTD::move(__rhs);
4150}
4151
4152template<class _CharT, class _Traits, class _Allocator>
4153inline _LIBCPP_INLINE_VISIBILITY
4154basic_string<_CharT, _Traits, _Allocator>
4155operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, const _CharT* __rhs)
4156{
4157    return _VSTD::move(__lhs.append(__rhs));
4158}
4159
4160template<class _CharT, class _Traits, class _Allocator>
4161inline _LIBCPP_INLINE_VISIBILITY
4162basic_string<_CharT, _Traits, _Allocator>
4163operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, _CharT __rhs)
4164{
4165    __lhs.push_back(__rhs);
4166    return _VSTD::move(__lhs);
4167}
4168
4169#endif  // _LIBCPP_CXX03_LANG
4170
4171// swap
4172
4173template<class _CharT, class _Traits, class _Allocator>
4174inline _LIBCPP_INLINE_VISIBILITY
4175void
4176swap(basic_string<_CharT, _Traits, _Allocator>& __lhs,
4177     basic_string<_CharT, _Traits, _Allocator>& __rhs)
4178     _NOEXCEPT_(_NOEXCEPT_(__lhs.swap(__rhs)))
4179{
4180    __lhs.swap(__rhs);
4181}
4182
4183#ifndef _LIBCPP_NO_HAS_CHAR8_T
4184typedef basic_string<char8_t> u8string;
4185#endif
4186
4187#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
4188typedef basic_string<char16_t> u16string;
4189typedef basic_string<char32_t> u32string;
4190#endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
4191
4192_LIBCPP_FUNC_VIS int                stoi  (const string& __str, size_t* __idx = 0, int __base = 10);
4193_LIBCPP_FUNC_VIS long               stol  (const string& __str, size_t* __idx = 0, int __base = 10);
4194_LIBCPP_FUNC_VIS unsigned long      stoul (const string& __str, size_t* __idx = 0, int __base = 10);
4195_LIBCPP_FUNC_VIS long long          stoll (const string& __str, size_t* __idx = 0, int __base = 10);
4196_LIBCPP_FUNC_VIS unsigned long long stoull(const string& __str, size_t* __idx = 0, int __base = 10);
4197
4198_LIBCPP_FUNC_VIS float       stof (const string& __str, size_t* __idx = 0);
4199_LIBCPP_FUNC_VIS double      stod (const string& __str, size_t* __idx = 0);
4200_LIBCPP_FUNC_VIS long double stold(const string& __str, size_t* __idx = 0);
4201
4202_LIBCPP_FUNC_VIS string to_string(int __val);
4203_LIBCPP_FUNC_VIS string to_string(unsigned __val);
4204_LIBCPP_FUNC_VIS string to_string(long __val);
4205_LIBCPP_FUNC_VIS string to_string(unsigned long __val);
4206_LIBCPP_FUNC_VIS string to_string(long long __val);
4207_LIBCPP_FUNC_VIS string to_string(unsigned long long __val);
4208_LIBCPP_FUNC_VIS string to_string(float __val);
4209_LIBCPP_FUNC_VIS string to_string(double __val);
4210_LIBCPP_FUNC_VIS string to_string(long double __val);
4211
4212_LIBCPP_FUNC_VIS int                stoi  (const wstring& __str, size_t* __idx = 0, int __base = 10);
4213_LIBCPP_FUNC_VIS long               stol  (const wstring& __str, size_t* __idx = 0, int __base = 10);
4214_LIBCPP_FUNC_VIS unsigned long      stoul (const wstring& __str, size_t* __idx = 0, int __base = 10);
4215_LIBCPP_FUNC_VIS long long          stoll (const wstring& __str, size_t* __idx = 0, int __base = 10);
4216_LIBCPP_FUNC_VIS unsigned long long stoull(const wstring& __str, size_t* __idx = 0, int __base = 10);
4217
4218_LIBCPP_FUNC_VIS float       stof (const wstring& __str, size_t* __idx = 0);
4219_LIBCPP_FUNC_VIS double      stod (const wstring& __str, size_t* __idx = 0);
4220_LIBCPP_FUNC_VIS long double stold(const wstring& __str, size_t* __idx = 0);
4221
4222_LIBCPP_FUNC_VIS wstring to_wstring(int __val);
4223_LIBCPP_FUNC_VIS wstring to_wstring(unsigned __val);
4224_LIBCPP_FUNC_VIS wstring to_wstring(long __val);
4225_LIBCPP_FUNC_VIS wstring to_wstring(unsigned long __val);
4226_LIBCPP_FUNC_VIS wstring to_wstring(long long __val);
4227_LIBCPP_FUNC_VIS wstring to_wstring(unsigned long long __val);
4228_LIBCPP_FUNC_VIS wstring to_wstring(float __val);
4229_LIBCPP_FUNC_VIS wstring to_wstring(double __val);
4230_LIBCPP_FUNC_VIS wstring to_wstring(long double __val);
4231
4232template<class _CharT, class _Traits, class _Allocator>
4233    const typename basic_string<_CharT, _Traits, _Allocator>::size_type
4234                   basic_string<_CharT, _Traits, _Allocator>::npos;
4235
4236template <class _CharT, class _Allocator>
4237struct _LIBCPP_TEMPLATE_VIS
4238    hash<basic_string<_CharT, char_traits<_CharT>, _Allocator> >
4239    : public unary_function<
4240          basic_string<_CharT, char_traits<_CharT>, _Allocator>, size_t>
4241{
4242    size_t
4243    operator()(const basic_string<_CharT, char_traits<_CharT>, _Allocator>& __val) const _NOEXCEPT
4244    { return __do_string_hash(__val.data(), __val.data() + __val.size()); }
4245};
4246
4247
4248template<class _CharT, class _Traits, class _Allocator>
4249basic_ostream<_CharT, _Traits>&
4250operator<<(basic_ostream<_CharT, _Traits>& __os,
4251           const basic_string<_CharT, _Traits, _Allocator>& __str);
4252
4253template<class _CharT, class _Traits, class _Allocator>
4254basic_istream<_CharT, _Traits>&
4255operator>>(basic_istream<_CharT, _Traits>& __is,
4256           basic_string<_CharT, _Traits, _Allocator>& __str);
4257
4258template<class _CharT, class _Traits, class _Allocator>
4259basic_istream<_CharT, _Traits>&
4260getline(basic_istream<_CharT, _Traits>& __is,
4261        basic_string<_CharT, _Traits, _Allocator>& __str, _CharT __dlm);
4262
4263template<class _CharT, class _Traits, class _Allocator>
4264inline _LIBCPP_INLINE_VISIBILITY
4265basic_istream<_CharT, _Traits>&
4266getline(basic_istream<_CharT, _Traits>& __is,
4267        basic_string<_CharT, _Traits, _Allocator>& __str);
4268
4269#ifndef _LIBCPP_CXX03_LANG
4270
4271template<class _CharT, class _Traits, class _Allocator>
4272inline _LIBCPP_INLINE_VISIBILITY
4273basic_istream<_CharT, _Traits>&
4274getline(basic_istream<_CharT, _Traits>&& __is,
4275        basic_string<_CharT, _Traits, _Allocator>& __str, _CharT __dlm);
4276
4277template<class _CharT, class _Traits, class _Allocator>
4278inline _LIBCPP_INLINE_VISIBILITY
4279basic_istream<_CharT, _Traits>&
4280getline(basic_istream<_CharT, _Traits>&& __is,
4281        basic_string<_CharT, _Traits, _Allocator>& __str);
4282
4283#endif  // _LIBCPP_CXX03_LANG
4284
4285#if _LIBCPP_STD_VER > 17
4286template<class _CharT, class _Traits, class _Allocator, class _Up>
4287inline _LIBCPP_INLINE_VISIBILITY
4288void erase(basic_string<_CharT, _Traits, _Allocator>& __str, const _Up& __v)
4289{ __str.erase(_VSTD::remove(__str.begin(), __str.end(), __v), __str.end()); }
4290
4291template<class _CharT, class _Traits, class _Allocator, class _Predicate>
4292inline _LIBCPP_INLINE_VISIBILITY
4293void erase_if(basic_string<_CharT, _Traits, _Allocator>& __str, _Predicate __pred)
4294{ __str.erase(_VSTD::remove_if(__str.begin(), __str.end(), __pred), __str.end()); }
4295#endif
4296
4297#if _LIBCPP_DEBUG_LEVEL >= 2
4298
4299template<class _CharT, class _Traits, class _Allocator>
4300bool
4301basic_string<_CharT, _Traits, _Allocator>::__dereferenceable(const const_iterator* __i) const
4302{
4303    return this->data() <= _VSTD::__to_address(__i->base()) &&
4304           _VSTD::__to_address(__i->base()) < this->data() + this->size();
4305}
4306
4307template<class _CharT, class _Traits, class _Allocator>
4308bool
4309basic_string<_CharT, _Traits, _Allocator>::__decrementable(const const_iterator* __i) const
4310{
4311    return this->data() < _VSTD::__to_address(__i->base()) &&
4312           _VSTD::__to_address(__i->base()) <= this->data() + this->size();
4313}
4314
4315template<class _CharT, class _Traits, class _Allocator>
4316bool
4317basic_string<_CharT, _Traits, _Allocator>::__addable(const const_iterator* __i, ptrdiff_t __n) const
4318{
4319    const value_type* __p = _VSTD::__to_address(__i->base()) + __n;
4320    return this->data() <= __p && __p <= this->data() + this->size();
4321}
4322
4323template<class _CharT, class _Traits, class _Allocator>
4324bool
4325basic_string<_CharT, _Traits, _Allocator>::__subscriptable(const const_iterator* __i, ptrdiff_t __n) const
4326{
4327    const value_type* __p = _VSTD::__to_address(__i->base()) + __n;
4328    return this->data() <= __p && __p < this->data() + this->size();
4329}
4330
4331#endif  // _LIBCPP_DEBUG_LEVEL >= 2
4332
4333_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_string<char>)
4334_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_string<wchar_t>)
4335
4336#if _LIBCPP_STD_VER > 11
4337// Literal suffixes for basic_string [basic.string.literals]
4338inline namespace literals
4339{
4340  inline namespace string_literals
4341  {
4342    inline _LIBCPP_INLINE_VISIBILITY
4343    basic_string<char> operator "" s( const char *__str, size_t __len )
4344    {
4345        return basic_string<char> (__str, __len);
4346    }
4347
4348    inline _LIBCPP_INLINE_VISIBILITY
4349    basic_string<wchar_t> operator "" s( const wchar_t *__str, size_t __len )
4350    {
4351        return basic_string<wchar_t> (__str, __len);
4352    }
4353
4354#ifndef _LIBCPP_NO_HAS_CHAR8_T
4355    inline _LIBCPP_INLINE_VISIBILITY
4356    basic_string<char8_t> operator "" s(const char8_t *__str, size_t __len) _NOEXCEPT
4357    {
4358        return basic_string<char8_t> (__str, __len);
4359    }
4360#endif
4361
4362    inline _LIBCPP_INLINE_VISIBILITY
4363    basic_string<char16_t> operator "" s( const char16_t *__str, size_t __len )
4364    {
4365        return basic_string<char16_t> (__str, __len);
4366    }
4367
4368    inline _LIBCPP_INLINE_VISIBILITY
4369    basic_string<char32_t> operator "" s( const char32_t *__str, size_t __len )
4370    {
4371        return basic_string<char32_t> (__str, __len);
4372    }
4373  }
4374}
4375#endif
4376
4377_LIBCPP_END_NAMESPACE_STD
4378
4379_LIBCPP_POP_MACROS
4380
4381#endif  // _LIBCPP_STRING
4382