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utility (48826B)


      1 // -*- C++ -*-
      2 //===-------------------------- utility -----------------------------------===//
      3 //
      4 //                     The LLVM Compiler Infrastructure
      5 //
      6 // This file is dual licensed under the MIT and the University of Illinois Open
      7 // Source Licenses. See LICENSE.TXT for details.
      8 //
      9 //===----------------------------------------------------------------------===//
     10 
     11 #ifndef _LIBCPP_UTILITY
     12 #define _LIBCPP_UTILITY
     13 
     14 /*
     15     utility synopsis
     16 
     17 #include <initializer_list>
     18 
     19 namespace std
     20 {
     21 
     22 template <class T>
     23     void
     24     swap(T& a, T& b);
     25 
     26 namespace rel_ops
     27 {
     28     template<class T> bool operator!=(const T&, const T&);
     29     template<class T> bool operator> (const T&, const T&);
     30     template<class T> bool operator<=(const T&, const T&);
     31     template<class T> bool operator>=(const T&, const T&);
     32 }
     33 
     34 template<class T>
     35 void
     36 swap(T& a, T& b) noexcept(is_nothrow_move_constructible<T>::value &&
     37                           is_nothrow_move_assignable<T>::value);
     38 
     39 template <class T, size_t N>
     40 void
     41 swap(T (&a)[N], T (&b)[N]) noexcept(noexcept(swap(*a, *b)));
     42 
     43 template <class T> T&& forward(typename remove_reference<T>::type& t) noexcept;  // constexpr in C++14
     44 template <class T> T&& forward(typename remove_reference<T>::type&& t) noexcept; // constexpr in C++14
     45 
     46 template <class T> typename remove_reference<T>::type&& move(T&&) noexcept;      // constexpr in C++14
     47 
     48 template <class T>
     49     typename conditional
     50     <
     51         !is_nothrow_move_constructible<T>::value && is_copy_constructible<T>::value,
     52         const T&,
     53         T&&
     54     >::type
     55     move_if_noexcept(T& x) noexcept; // constexpr in C++14
     56 
     57 template <class T> constexpr add_const_t<T>& as_const(T& t) noexcept;      // C++17
     58 template <class T>                      void as_const(const T&&) = delete; // C++17
     59 
     60 template <class T> typename add_rvalue_reference<T>::type declval() noexcept;
     61 
     62 template <class T1, class T2>
     63 struct pair
     64 {
     65     typedef T1 first_type;
     66     typedef T2 second_type;
     67 
     68     T1 first;
     69     T2 second;
     70 
     71     pair(const pair&) = default;
     72     pair(pair&&) = default;
     73     constexpr pair();
     74     pair(const T1& x, const T2& y);                          // constexpr in C++14
     75     template <class U, class V> pair(U&& x, V&& y);          // constexpr in C++14
     76     template <class U, class V> pair(const pair<U, V>& p);   // constexpr in C++14
     77     template <class U, class V> pair(pair<U, V>&& p);        // constexpr in C++14
     78     template <class... Args1, class... Args2>
     79         pair(piecewise_construct_t, tuple<Args1...> first_args,
     80              tuple<Args2...> second_args);
     81 
     82     template <class U, class V> pair& operator=(const pair<U, V>& p);
     83     pair& operator=(pair&& p) noexcept(is_nothrow_move_assignable<T1>::value &&
     84                                        is_nothrow_move_assignable<T2>::value);
     85     template <class U, class V> pair& operator=(pair<U, V>&& p);
     86 
     87     void swap(pair& p) noexcept(is_nothrow_swappable_v<T1> &&
     88                                 is_nothrow_swappable_v<T2>);
     89 };
     90 
     91 template <class T1, class T2> bool operator==(const pair<T1,T2>&, const pair<T1,T2>&); // constexpr in C++14
     92 template <class T1, class T2> bool operator!=(const pair<T1,T2>&, const pair<T1,T2>&); // constexpr in C++14
     93 template <class T1, class T2> bool operator< (const pair<T1,T2>&, const pair<T1,T2>&); // constexpr in C++14
     94 template <class T1, class T2> bool operator> (const pair<T1,T2>&, const pair<T1,T2>&); // constexpr in C++14
     95 template <class T1, class T2> bool operator>=(const pair<T1,T2>&, const pair<T1,T2>&); // constexpr in C++14
     96 template <class T1, class T2> bool operator<=(const pair<T1,T2>&, const pair<T1,T2>&); // constexpr in C++14
     97 
     98 template <class T1, class T2> pair<V1, V2> make_pair(T1&&, T2&&);   // constexpr in C++14
     99 template <class T1, class T2>
    100 void
    101 swap(pair<T1, T2>& x, pair<T1, T2>& y) noexcept(noexcept(x.swap(y)));
    102 
    103 struct piecewise_construct_t { };
    104 inline constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
    105 
    106 template <class T> struct tuple_size;
    107 template <size_t I, class T> class tuple_element;
    108 
    109 template <class T1, class T2> struct tuple_size<pair<T1, T2> >;
    110 template <class T1, class T2> struct tuple_element<0, pair<T1, T2> >;
    111 template <class T1, class T2> struct tuple_element<1, pair<T1, T2> >;
    112 
    113 template<size_t I, class T1, class T2>
    114     typename tuple_element<I, pair<T1, T2> >::type&
    115     get(pair<T1, T2>&) noexcept; // constexpr in C++14
    116 
    117 template<size_t I, class T1, class T2>
    118     const typename tuple_element<I, pair<T1, T2> >::type&
    119     get(const pair<T1, T2>&) noexcept; // constexpr in C++14
    120 
    121 template<size_t I, class T1, class T2>
    122     typename tuple_element<I, pair<T1, T2> >::type&&
    123     get(pair<T1, T2>&&) noexcept; // constexpr in C++14
    124 
    125 template<size_t I, class T1, class T2>
    126     const typename tuple_element<I, pair<T1, T2> >::type&&
    127     get(const pair<T1, T2>&&) noexcept; // constexpr in C++14
    128 
    129 template<class T1, class T2>
    130     constexpr T1& get(pair<T1, T2>&) noexcept; // C++14
    131 
    132 template<class T1, class T2>
    133     constexpr const T1& get(const pair<T1, T2>&) noexcept; // C++14
    134 
    135 template<class T1, class T2>
    136     constexpr T1&& get(pair<T1, T2>&&) noexcept; // C++14
    137 
    138 template<class T1, class T2>
    139     constexpr const T1&& get(const pair<T1, T2>&&) noexcept; // C++14
    140 
    141 template<class T1, class T2>
    142     constexpr T1& get(pair<T2, T1>&) noexcept; // C++14
    143 
    144 template<class T1, class T2>
    145     constexpr const T1& get(const pair<T2, T1>&) noexcept; // C++14
    146 
    147 template<class T1, class T2>
    148     constexpr T1&& get(pair<T2, T1>&&) noexcept; // C++14
    149 
    150 template<class T1, class T2>
    151     constexpr const T1&& get(const pair<T2, T1>&&) noexcept; // C++14
    152 
    153 // C++14
    154 
    155 template<class T, T... I>
    156 struct integer_sequence
    157 {
    158     typedef T value_type;
    159 
    160     static constexpr size_t size() noexcept;
    161 };
    162 
    163 template<size_t... I>
    164   using index_sequence = integer_sequence<size_t, I...>;
    165 
    166 template<class T, T N>
    167   using make_integer_sequence = integer_sequence<T, 0, 1, ..., N-1>;
    168 template<size_t N>
    169   using make_index_sequence = make_integer_sequence<size_t, N>;
    170 
    171 template<class... T>
    172   using index_sequence_for = make_index_sequence<sizeof...(T)>;
    173 
    174 template<class T, class U=T>
    175     T exchange(T& obj, U&& new_value);
    176 
    177 // 20.2.7, in-place construction // C++17
    178 struct in_place_t {
    179   explicit in_place_t() = default;
    180 };
    181 inline constexpr in_place_t in_place{};
    182 template <class T>
    183   struct in_place_type_t {
    184     explicit in_place_type_t() = default;
    185   };
    186 template <class T>
    187   inline constexpr in_place_type_t<T> in_place_type{};
    188 template <size_t I>
    189   struct in_place_index_t {
    190     explicit in_place_index_t() = default;
    191   };
    192 template <size_t I>
    193   inline constexpr in_place_index_t<I> in_place_index{};
    194 
    195 }  // std
    196 
    197 */
    198 
    199 #include <__config>
    200 #include <__tuple>
    201 #include <type_traits>
    202 #include <initializer_list>
    203 #include <cstddef>
    204 #include <cstring>
    205 #include <cstdint>
    206 #include <version>
    207 #include <__debug>
    208 
    209 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
    210 #pragma GCC system_header
    211 #endif
    212 
    213 _LIBCPP_BEGIN_NAMESPACE_STD
    214 
    215 namespace rel_ops
    216 {
    217 
    218 template<class _Tp>
    219 inline _LIBCPP_INLINE_VISIBILITY
    220 bool
    221 operator!=(const _Tp& __x, const _Tp& __y)
    222 {
    223     return !(__x == __y);
    224 }
    225 
    226 template<class _Tp>
    227 inline _LIBCPP_INLINE_VISIBILITY
    228 bool
    229 operator> (const _Tp& __x, const _Tp& __y)
    230 {
    231     return __y < __x;
    232 }
    233 
    234 template<class _Tp>
    235 inline _LIBCPP_INLINE_VISIBILITY
    236 bool
    237 operator<=(const _Tp& __x, const _Tp& __y)
    238 {
    239     return !(__y < __x);
    240 }
    241 
    242 template<class _Tp>
    243 inline _LIBCPP_INLINE_VISIBILITY
    244 bool
    245 operator>=(const _Tp& __x, const _Tp& __y)
    246 {
    247     return !(__x < __y);
    248 }
    249 
    250 }  // rel_ops
    251 
    252 // swap_ranges
    253 
    254 
    255 template <class _ForwardIterator1, class _ForwardIterator2>
    256 inline _LIBCPP_INLINE_VISIBILITY
    257 _ForwardIterator2
    258 swap_ranges(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2)
    259 {
    260     for(; __first1 != __last1; ++__first1, (void) ++__first2)
    261         swap(*__first1, *__first2);
    262     return __first2;
    263 }
    264 
    265 // forward declared in <type_traits>
    266 template<class _Tp, size_t _Np>
    267 inline _LIBCPP_INLINE_VISIBILITY
    268 typename enable_if<
    269     __is_swappable<_Tp>::value
    270 >::type
    271 swap(_Tp (&__a)[_Np], _Tp (&__b)[_Np]) _NOEXCEPT_(__is_nothrow_swappable<_Tp>::value)
    272 {
    273     _VSTD::swap_ranges(__a, __a + _Np, __b);
    274 }
    275 
    276 template <class _Tp>
    277 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    278 #ifndef _LIBCPP_CXX03_LANG
    279 typename conditional
    280 <
    281     !is_nothrow_move_constructible<_Tp>::value && is_copy_constructible<_Tp>::value,
    282     const _Tp&,
    283     _Tp&&
    284 >::type
    285 #else  // _LIBCPP_CXX03_LANG
    286 const _Tp&
    287 #endif
    288 move_if_noexcept(_Tp& __x) _NOEXCEPT
    289 {
    290     return _VSTD::move(__x);
    291 }
    292 
    293 #if _LIBCPP_STD_VER > 14
    294 template <class _Tp> constexpr add_const_t<_Tp>& as_const(_Tp& __t) noexcept { return __t; }
    295 template <class _Tp>                        void as_const(const _Tp&&) = delete;
    296 #endif
    297 
    298 struct _LIBCPP_TEMPLATE_VIS piecewise_construct_t { };
    299 #if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_LIBRARY)
    300 extern _LIBCPP_EXPORTED_FROM_ABI const piecewise_construct_t piecewise_construct;// = piecewise_construct_t();
    301 #else
    302 /* _LIBCPP_INLINE_VAR */ constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
    303 #endif
    304 
    305 #if defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
    306 template <class, class>
    307 struct __non_trivially_copyable_base {
    308   _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
    309   __non_trivially_copyable_base() _NOEXCEPT {}
    310   _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
    311   __non_trivially_copyable_base(__non_trivially_copyable_base const&) _NOEXCEPT {}
    312 };
    313 #endif
    314 
    315 template <class _T1, class _T2>
    316 struct _LIBCPP_TEMPLATE_VIS pair
    317 #if defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
    318 : private __non_trivially_copyable_base<_T1, _T2>
    319 #endif
    320 {
    321     typedef _T1 first_type;
    322     typedef _T2 second_type;
    323 
    324     _T1 first;
    325     _T2 second;
    326 
    327 #if !defined(_LIBCPP_CXX03_LANG)
    328     pair(pair const&) = default;
    329     pair(pair&&) = default;
    330 #else
    331   // Use the implicitly declared copy constructor in C++03
    332 #endif
    333 
    334 #ifdef _LIBCPP_CXX03_LANG
    335     _LIBCPP_INLINE_VISIBILITY
    336     pair() : first(), second() {}
    337 
    338     _LIBCPP_INLINE_VISIBILITY
    339     pair(_T1 const& __t1, _T2 const& __t2) : first(__t1), second(__t2) {}
    340 
    341     template <class _U1, class _U2>
    342     _LIBCPP_INLINE_VISIBILITY
    343     pair(const pair<_U1, _U2>& __p) : first(__p.first), second(__p.second) {}
    344 
    345     _LIBCPP_INLINE_VISIBILITY
    346     pair& operator=(pair const& __p) {
    347         first = __p.first;
    348         second = __p.second;
    349         return *this;
    350     }
    351 #else
    352     template <bool _Val>
    353     using _EnableB = typename enable_if<_Val, bool>::type;
    354 
    355     struct _CheckArgs {
    356       template <class _U1, class _U2>
    357       static constexpr bool __enable_default() {
    358           return is_default_constructible<_U1>::value
    359               && is_default_constructible<_U2>::value;
    360       }
    361 
    362       template <class _U1, class _U2>
    363       static constexpr bool __enable_explicit() {
    364           return is_constructible<first_type, _U1>::value
    365               && is_constructible<second_type, _U2>::value
    366               && (!is_convertible<_U1, first_type>::value
    367                   || !is_convertible<_U2, second_type>::value);
    368       }
    369 
    370       template <class _U1, class _U2>
    371       static constexpr bool __enable_implicit() {
    372           return is_constructible<first_type, _U1>::value
    373               && is_constructible<second_type, _U2>::value
    374               && is_convertible<_U1, first_type>::value
    375               && is_convertible<_U2, second_type>::value;
    376       }
    377     };
    378 
    379     template <bool _MaybeEnable>
    380     using _CheckArgsDep = typename conditional<
    381       _MaybeEnable, _CheckArgs, __check_tuple_constructor_fail>::type;
    382 
    383     struct _CheckTupleLikeConstructor {
    384         template <class _Tuple>
    385         static constexpr bool __enable_implicit() {
    386             return __tuple_convertible<_Tuple, pair>::value;
    387         }
    388 
    389         template <class _Tuple>
    390         static constexpr bool __enable_explicit() {
    391             return __tuple_constructible<_Tuple, pair>::value
    392                && !__tuple_convertible<_Tuple, pair>::value;
    393         }
    394 
    395         template <class _Tuple>
    396         static constexpr bool __enable_assign() {
    397             return __tuple_assignable<_Tuple, pair>::value;
    398         }
    399     };
    400 
    401     template <class _Tuple>
    402     using _CheckTLC = typename conditional<
    403         __tuple_like_with_size<_Tuple, 2>::value
    404             && !is_same<typename decay<_Tuple>::type, pair>::value,
    405         _CheckTupleLikeConstructor,
    406         __check_tuple_constructor_fail
    407     >::type;
    408 
    409     template<bool _Dummy = true, _EnableB<
    410             _CheckArgsDep<_Dummy>::template __enable_default<_T1, _T2>()
    411     > = false>
    412     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    413     pair() _NOEXCEPT_(is_nothrow_default_constructible<first_type>::value &&
    414                       is_nothrow_default_constructible<second_type>::value)
    415         : first(), second() {}
    416 
    417     template <bool _Dummy = true, _EnableB<
    418              _CheckArgsDep<_Dummy>::template __enable_explicit<_T1 const&, _T2 const&>()
    419     > = false>
    420     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    421     explicit pair(_T1 const& __t1, _T2 const& __t2)
    422         _NOEXCEPT_(is_nothrow_copy_constructible<first_type>::value &&
    423                    is_nothrow_copy_constructible<second_type>::value)
    424         : first(__t1), second(__t2) {}
    425 
    426     template<bool _Dummy = true, _EnableB<
    427             _CheckArgsDep<_Dummy>::template __enable_implicit<_T1 const&, _T2 const&>()
    428     > = false>
    429     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    430     pair(_T1 const& __t1, _T2 const& __t2)
    431         _NOEXCEPT_(is_nothrow_copy_constructible<first_type>::value &&
    432                    is_nothrow_copy_constructible<second_type>::value)
    433         : first(__t1), second(__t2) {}
    434 
    435     template<class _U1, class _U2, _EnableB<
    436              _CheckArgs::template __enable_explicit<_U1, _U2>()
    437     > = false>
    438     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    439     explicit pair(_U1&& __u1, _U2&& __u2)
    440         _NOEXCEPT_((is_nothrow_constructible<first_type, _U1>::value &&
    441                     is_nothrow_constructible<second_type, _U2>::value))
    442         : first(_VSTD::forward<_U1>(__u1)), second(_VSTD::forward<_U2>(__u2)) {}
    443 
    444     template<class _U1, class _U2, _EnableB<
    445             _CheckArgs::template __enable_implicit<_U1, _U2>()
    446     > = false>
    447     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    448     pair(_U1&& __u1, _U2&& __u2)
    449         _NOEXCEPT_((is_nothrow_constructible<first_type, _U1>::value &&
    450                     is_nothrow_constructible<second_type, _U2>::value))
    451         : first(_VSTD::forward<_U1>(__u1)), second(_VSTD::forward<_U2>(__u2)) {}
    452 
    453     template<class _U1, class _U2, _EnableB<
    454             _CheckArgs::template __enable_explicit<_U1 const&, _U2 const&>()
    455     > = false>
    456     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    457     explicit pair(pair<_U1, _U2> const& __p)
    458         _NOEXCEPT_((is_nothrow_constructible<first_type, _U1 const&>::value &&
    459                     is_nothrow_constructible<second_type, _U2 const&>::value))
    460         : first(__p.first), second(__p.second) {}
    461 
    462     template<class _U1, class _U2, _EnableB<
    463             _CheckArgs::template __enable_implicit<_U1 const&, _U2 const&>()
    464     > = false>
    465     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    466     pair(pair<_U1, _U2> const& __p)
    467         _NOEXCEPT_((is_nothrow_constructible<first_type, _U1 const&>::value &&
    468                     is_nothrow_constructible<second_type, _U2 const&>::value))
    469         : first(__p.first), second(__p.second) {}
    470 
    471     template<class _U1, class _U2, _EnableB<
    472             _CheckArgs::template __enable_explicit<_U1, _U2>()
    473     > = false>
    474     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    475     explicit pair(pair<_U1, _U2>&&__p)
    476         _NOEXCEPT_((is_nothrow_constructible<first_type, _U1&&>::value &&
    477                     is_nothrow_constructible<second_type, _U2&&>::value))
    478         : first(_VSTD::forward<_U1>(__p.first)), second(_VSTD::forward<_U2>(__p.second)) {}
    479 
    480     template<class _U1, class _U2, _EnableB<
    481             _CheckArgs::template __enable_implicit<_U1, _U2>()
    482     > = false>
    483     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    484     pair(pair<_U1, _U2>&& __p)
    485         _NOEXCEPT_((is_nothrow_constructible<first_type, _U1&&>::value &&
    486                     is_nothrow_constructible<second_type, _U2&&>::value))
    487         : first(_VSTD::forward<_U1>(__p.first)), second(_VSTD::forward<_U2>(__p.second)) {}
    488 
    489     template<class _Tuple, _EnableB<
    490             _CheckTLC<_Tuple>::template __enable_explicit<_Tuple>()
    491     > = false>
    492     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    493     explicit pair(_Tuple&& __p)
    494         : first(_VSTD::get<0>(_VSTD::forward<_Tuple>(__p))),
    495           second(_VSTD::get<1>(_VSTD::forward<_Tuple>(__p))) {}
    496 
    497     template<class _Tuple, _EnableB<
    498             _CheckTLC<_Tuple>::template __enable_implicit<_Tuple>()
    499     > = false>
    500     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    501     pair(_Tuple&& __p)
    502         : first(_VSTD::get<0>(_VSTD::forward<_Tuple>(__p))),
    503           second(_VSTD::get<1>(_VSTD::forward<_Tuple>(__p))) {}
    504 
    505     template <class... _Args1, class... _Args2>
    506     _LIBCPP_INLINE_VISIBILITY
    507     pair(piecewise_construct_t __pc,
    508          tuple<_Args1...> __first_args, tuple<_Args2...> __second_args)
    509         _NOEXCEPT_((is_nothrow_constructible<first_type, _Args1...>::value &&
    510                     is_nothrow_constructible<second_type, _Args2...>::value))
    511         : pair(__pc, __first_args, __second_args,
    512                 typename __make_tuple_indices<sizeof...(_Args1)>::type(),
    513                 typename __make_tuple_indices<sizeof...(_Args2) >::type()) {}
    514 
    515     _LIBCPP_INLINE_VISIBILITY
    516     pair& operator=(typename conditional<
    517                         is_copy_assignable<first_type>::value &&
    518                         is_copy_assignable<second_type>::value,
    519                     pair, __nat>::type const& __p)
    520         _NOEXCEPT_(is_nothrow_copy_assignable<first_type>::value &&
    521                    is_nothrow_copy_assignable<second_type>::value)
    522     {
    523         first = __p.first;
    524         second = __p.second;
    525         return *this;
    526     }
    527 
    528     _LIBCPP_INLINE_VISIBILITY
    529     pair& operator=(typename conditional<
    530                         is_move_assignable<first_type>::value &&
    531                         is_move_assignable<second_type>::value,
    532                     pair, __nat>::type&& __p)
    533         _NOEXCEPT_(is_nothrow_move_assignable<first_type>::value &&
    534                    is_nothrow_move_assignable<second_type>::value)
    535     {
    536         first = _VSTD::forward<first_type>(__p.first);
    537         second = _VSTD::forward<second_type>(__p.second);
    538         return *this;
    539     }
    540 
    541     template <class _Tuple, _EnableB<
    542             _CheckTLC<_Tuple>::template __enable_assign<_Tuple>()
    543      > = false>
    544     _LIBCPP_INLINE_VISIBILITY
    545     pair& operator=(_Tuple&& __p) {
    546         first = _VSTD::get<0>(_VSTD::forward<_Tuple>(__p));
    547         second = _VSTD::get<1>(_VSTD::forward<_Tuple>(__p));
    548         return *this;
    549     }
    550 #endif
    551 
    552     _LIBCPP_INLINE_VISIBILITY
    553     void
    554     swap(pair& __p) _NOEXCEPT_(__is_nothrow_swappable<first_type>::value &&
    555                                __is_nothrow_swappable<second_type>::value)
    556     {
    557         using _VSTD::swap;
    558         swap(first,  __p.first);
    559         swap(second, __p.second);
    560     }
    561 private:
    562 
    563 #ifndef _LIBCPP_CXX03_LANG
    564     template <class... _Args1, class... _Args2, size_t... _I1, size_t... _I2>
    565         _LIBCPP_INLINE_VISIBILITY
    566         pair(piecewise_construct_t,
    567              tuple<_Args1...>& __first_args, tuple<_Args2...>& __second_args,
    568              __tuple_indices<_I1...>, __tuple_indices<_I2...>);
    569 #endif
    570 };
    571 
    572 #ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
    573 template<class _T1, class _T2>
    574 pair(_T1, _T2) -> pair<_T1, _T2>;
    575 #endif // _LIBCPP_HAS_NO_DEDUCTION_GUIDES
    576 
    577 template <class _T1, class _T2>
    578 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    579 bool
    580 operator==(const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
    581 {
    582     return __x.first == __y.first && __x.second == __y.second;
    583 }
    584 
    585 template <class _T1, class _T2>
    586 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    587 bool
    588 operator!=(const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
    589 {
    590     return !(__x == __y);
    591 }
    592 
    593 template <class _T1, class _T2>
    594 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    595 bool
    596 operator< (const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
    597 {
    598     return __x.first < __y.first || (!(__y.first < __x.first) && __x.second < __y.second);
    599 }
    600 
    601 template <class _T1, class _T2>
    602 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    603 bool
    604 operator> (const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
    605 {
    606     return __y < __x;
    607 }
    608 
    609 template <class _T1, class _T2>
    610 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    611 bool
    612 operator>=(const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
    613 {
    614     return !(__x < __y);
    615 }
    616 
    617 template <class _T1, class _T2>
    618 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    619 bool
    620 operator<=(const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
    621 {
    622     return !(__y < __x);
    623 }
    624 
    625 template <class _T1, class _T2>
    626 inline _LIBCPP_INLINE_VISIBILITY
    627 typename enable_if
    628 <
    629     __is_swappable<_T1>::value &&
    630     __is_swappable<_T2>::value,
    631     void
    632 >::type
    633 swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
    634                      _NOEXCEPT_((__is_nothrow_swappable<_T1>::value &&
    635                                  __is_nothrow_swappable<_T2>::value))
    636 {
    637     __x.swap(__y);
    638 }
    639 
    640 template <class _Tp>
    641 struct __unwrap_reference { typedef _Tp type; };
    642 
    643 template <class _Tp>
    644 struct __unwrap_reference<reference_wrapper<_Tp> > { typedef _Tp& type; };
    645 
    646 #if _LIBCPP_STD_VER > 17
    647 template <class _Tp>
    648 struct unwrap_reference : __unwrap_reference<_Tp> { };
    649 
    650 template <class _Tp>
    651 struct unwrap_ref_decay : unwrap_reference<typename decay<_Tp>::type> { };
    652 #endif // > C++17
    653 
    654 template <class _Tp>
    655 struct __unwrap_ref_decay
    656 #if _LIBCPP_STD_VER > 17
    657     : unwrap_ref_decay<_Tp>
    658 #else
    659     : __unwrap_reference<typename decay<_Tp>::type>
    660 #endif
    661 { };
    662 
    663 #ifndef _LIBCPP_CXX03_LANG
    664 
    665 template <class _T1, class _T2>
    666 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    667 pair<typename __unwrap_ref_decay<_T1>::type, typename __unwrap_ref_decay<_T2>::type>
    668 make_pair(_T1&& __t1, _T2&& __t2)
    669 {
    670     return pair<typename __unwrap_ref_decay<_T1>::type, typename __unwrap_ref_decay<_T2>::type>
    671                (_VSTD::forward<_T1>(__t1), _VSTD::forward<_T2>(__t2));
    672 }
    673 
    674 #else  // _LIBCPP_CXX03_LANG
    675 
    676 template <class _T1, class _T2>
    677 inline _LIBCPP_INLINE_VISIBILITY
    678 pair<_T1,_T2>
    679 make_pair(_T1 __x, _T2 __y)
    680 {
    681     return pair<_T1, _T2>(__x, __y);
    682 }
    683 
    684 #endif  // _LIBCPP_CXX03_LANG
    685 
    686 template <class _T1, class _T2>
    687   struct _LIBCPP_TEMPLATE_VIS tuple_size<pair<_T1, _T2> >
    688     : public integral_constant<size_t, 2> {};
    689 
    690 template <size_t _Ip, class _T1, class _T2>
    691 class _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, pair<_T1, _T2> >
    692 {
    693     static_assert(_Ip < 2, "Index out of bounds in std::tuple_element<std::pair<T1, T2>>");
    694 };
    695 
    696 template <class _T1, class _T2>
    697 class _LIBCPP_TEMPLATE_VIS tuple_element<0, pair<_T1, _T2> >
    698 {
    699 public:
    700     typedef _T1 type;
    701 };
    702 
    703 template <class _T1, class _T2>
    704 class _LIBCPP_TEMPLATE_VIS tuple_element<1, pair<_T1, _T2> >
    705 {
    706 public:
    707     typedef _T2 type;
    708 };
    709 
    710 template <size_t _Ip> struct __get_pair;
    711 
    712 template <>
    713 struct __get_pair<0>
    714 {
    715     template <class _T1, class _T2>
    716     static
    717     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    718     _T1&
    719     get(pair<_T1, _T2>& __p) _NOEXCEPT {return __p.first;}
    720 
    721     template <class _T1, class _T2>
    722     static
    723     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    724     const _T1&
    725     get(const pair<_T1, _T2>& __p) _NOEXCEPT {return __p.first;}
    726 
    727 #ifndef _LIBCPP_CXX03_LANG
    728     template <class _T1, class _T2>
    729     static
    730     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    731     _T1&&
    732     get(pair<_T1, _T2>&& __p) _NOEXCEPT {return _VSTD::forward<_T1>(__p.first);}
    733 
    734     template <class _T1, class _T2>
    735     static
    736     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    737     const _T1&&
    738     get(const pair<_T1, _T2>&& __p) _NOEXCEPT {return _VSTD::forward<const _T1>(__p.first);}
    739 #endif  // _LIBCPP_CXX03_LANG
    740 };
    741 
    742 template <>
    743 struct __get_pair<1>
    744 {
    745     template <class _T1, class _T2>
    746     static
    747     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    748     _T2&
    749     get(pair<_T1, _T2>& __p) _NOEXCEPT {return __p.second;}
    750 
    751     template <class _T1, class _T2>
    752     static
    753     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    754     const _T2&
    755     get(const pair<_T1, _T2>& __p) _NOEXCEPT {return __p.second;}
    756 
    757 #ifndef _LIBCPP_CXX03_LANG
    758     template <class _T1, class _T2>
    759     static
    760     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    761     _T2&&
    762     get(pair<_T1, _T2>&& __p) _NOEXCEPT {return _VSTD::forward<_T2>(__p.second);}
    763 
    764     template <class _T1, class _T2>
    765     static
    766     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    767     const _T2&&
    768     get(const pair<_T1, _T2>&& __p) _NOEXCEPT {return _VSTD::forward<const _T2>(__p.second);}
    769 #endif  // _LIBCPP_CXX03_LANG
    770 };
    771 
    772 template <size_t _Ip, class _T1, class _T2>
    773 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    774 typename tuple_element<_Ip, pair<_T1, _T2> >::type&
    775 get(pair<_T1, _T2>& __p) _NOEXCEPT
    776 {
    777     return __get_pair<_Ip>::get(__p);
    778 }
    779 
    780 template <size_t _Ip, class _T1, class _T2>
    781 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    782 const typename tuple_element<_Ip, pair<_T1, _T2> >::type&
    783 get(const pair<_T1, _T2>& __p) _NOEXCEPT
    784 {
    785     return __get_pair<_Ip>::get(__p);
    786 }
    787 
    788 #ifndef _LIBCPP_CXX03_LANG
    789 template <size_t _Ip, class _T1, class _T2>
    790 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    791 typename tuple_element<_Ip, pair<_T1, _T2> >::type&&
    792 get(pair<_T1, _T2>&& __p) _NOEXCEPT
    793 {
    794     return __get_pair<_Ip>::get(_VSTD::move(__p));
    795 }
    796 
    797 template <size_t _Ip, class _T1, class _T2>
    798 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
    799 const typename tuple_element<_Ip, pair<_T1, _T2> >::type&&
    800 get(const pair<_T1, _T2>&& __p) _NOEXCEPT
    801 {
    802     return __get_pair<_Ip>::get(_VSTD::move(__p));
    803 }
    804 #endif  // _LIBCPP_CXX03_LANG
    805 
    806 #if _LIBCPP_STD_VER > 11
    807 template <class _T1, class _T2>
    808 inline _LIBCPP_INLINE_VISIBILITY
    809 constexpr _T1 & get(pair<_T1, _T2>& __p) _NOEXCEPT
    810 {
    811     return __get_pair<0>::get(__p);
    812 }
    813 
    814 template <class _T1, class _T2>
    815 inline _LIBCPP_INLINE_VISIBILITY
    816 constexpr _T1 const & get(pair<_T1, _T2> const& __p) _NOEXCEPT
    817 {
    818     return __get_pair<0>::get(__p);
    819 }
    820 
    821 template <class _T1, class _T2>
    822 inline _LIBCPP_INLINE_VISIBILITY
    823 constexpr _T1 && get(pair<_T1, _T2>&& __p) _NOEXCEPT
    824 {
    825     return __get_pair<0>::get(_VSTD::move(__p));
    826 }
    827 
    828 template <class _T1, class _T2>
    829 inline _LIBCPP_INLINE_VISIBILITY
    830 constexpr _T1 const && get(pair<_T1, _T2> const&& __p) _NOEXCEPT
    831 {
    832     return __get_pair<0>::get(_VSTD::move(__p));
    833 }
    834 
    835 template <class _T1, class _T2>
    836 inline _LIBCPP_INLINE_VISIBILITY
    837 constexpr _T1 & get(pair<_T2, _T1>& __p) _NOEXCEPT
    838 {
    839     return __get_pair<1>::get(__p);
    840 }
    841 
    842 template <class _T1, class _T2>
    843 inline _LIBCPP_INLINE_VISIBILITY
    844 constexpr _T1 const & get(pair<_T2, _T1> const& __p) _NOEXCEPT
    845 {
    846     return __get_pair<1>::get(__p);
    847 }
    848 
    849 template <class _T1, class _T2>
    850 inline _LIBCPP_INLINE_VISIBILITY
    851 constexpr _T1 && get(pair<_T2, _T1>&& __p) _NOEXCEPT
    852 {
    853     return __get_pair<1>::get(_VSTD::move(__p));
    854 }
    855 
    856 template <class _T1, class _T2>
    857 inline _LIBCPP_INLINE_VISIBILITY
    858 constexpr _T1 const && get(pair<_T2, _T1> const&& __p) _NOEXCEPT
    859 {
    860     return __get_pair<1>::get(_VSTD::move(__p));
    861 }
    862 
    863 #endif
    864 
    865 #if _LIBCPP_STD_VER > 11
    866 
    867 template<class _Tp, _Tp... _Ip>
    868 struct _LIBCPP_TEMPLATE_VIS integer_sequence
    869 {
    870     typedef _Tp value_type;
    871     static_assert( is_integral<_Tp>::value,
    872                   "std::integer_sequence can only be instantiated with an integral type" );
    873     static
    874     _LIBCPP_INLINE_VISIBILITY
    875     constexpr
    876     size_t
    877     size() noexcept { return sizeof...(_Ip); }
    878 };
    879 
    880 template<size_t... _Ip>
    881     using index_sequence = integer_sequence<size_t, _Ip...>;
    882 
    883 #if __has_builtin(__make_integer_seq) && !defined(_LIBCPP_TESTING_FALLBACK_MAKE_INTEGER_SEQUENCE)
    884 
    885 template <class _Tp, _Tp _Ep>
    886 using __make_integer_sequence = __make_integer_seq<integer_sequence, _Tp, _Ep>;
    887 
    888 #else
    889 
    890 template<typename _Tp, _Tp _Np> using __make_integer_sequence_unchecked =
    891   typename __detail::__make<_Np>::type::template __convert<integer_sequence, _Tp>;
    892 
    893 template <class _Tp, _Tp _Ep>
    894 struct __make_integer_sequence_checked
    895 {
    896     static_assert(is_integral<_Tp>::value,
    897                   "std::make_integer_sequence can only be instantiated with an integral type" );
    898     static_assert(0 <= _Ep, "std::make_integer_sequence must have a non-negative sequence length");
    899     // Workaround GCC bug by preventing bad installations when 0 <= _Ep
    900     // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68929
    901     typedef __make_integer_sequence_unchecked<_Tp, 0 <= _Ep ? _Ep : 0> type;
    902 };
    903 
    904 template <class _Tp, _Tp _Ep>
    905 using __make_integer_sequence = typename __make_integer_sequence_checked<_Tp, _Ep>::type;
    906 
    907 #endif
    908 
    909 template<class _Tp, _Tp _Np>
    910     using make_integer_sequence = __make_integer_sequence<_Tp, _Np>;
    911 
    912 template<size_t _Np>
    913     using make_index_sequence = make_integer_sequence<size_t, _Np>;
    914 
    915 template<class... _Tp>
    916     using index_sequence_for = make_index_sequence<sizeof...(_Tp)>;
    917 
    918 #endif  // _LIBCPP_STD_VER > 11
    919 
    920 #if _LIBCPP_STD_VER > 11
    921 template<class _T1, class _T2 = _T1>
    922 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    923 _T1 exchange(_T1& __obj, _T2 && __new_value)
    924 {
    925     _T1 __old_value = _VSTD::move(__obj);
    926     __obj = _VSTD::forward<_T2>(__new_value);
    927     return __old_value;
    928 }
    929 #endif  // _LIBCPP_STD_VER > 11
    930 
    931 #if _LIBCPP_STD_VER > 14
    932 
    933 struct _LIBCPP_TYPE_VIS in_place_t {
    934     explicit in_place_t() = default;
    935 };
    936 _LIBCPP_INLINE_VAR constexpr in_place_t in_place{};
    937 
    938 template <class _Tp>
    939 struct _LIBCPP_TEMPLATE_VIS in_place_type_t {
    940     explicit in_place_type_t() = default;
    941 };
    942 template <class _Tp>
    943 _LIBCPP_INLINE_VAR constexpr in_place_type_t<_Tp> in_place_type{};
    944 
    945 template <size_t _Idx>
    946 struct _LIBCPP_TYPE_VIS in_place_index_t {
    947     explicit in_place_index_t() = default;
    948 };
    949 template <size_t _Idx>
    950 _LIBCPP_INLINE_VAR constexpr in_place_index_t<_Idx> in_place_index{};
    951 
    952 template <class _Tp> struct __is_inplace_type_imp : false_type {};
    953 template <class _Tp> struct __is_inplace_type_imp<in_place_type_t<_Tp>> : true_type {};
    954 
    955 template <class _Tp>
    956 using __is_inplace_type = __is_inplace_type_imp<__uncvref_t<_Tp>>;
    957 
    958 template <class _Tp> struct __is_inplace_index_imp : false_type {};
    959 template <size_t _Idx> struct __is_inplace_index_imp<in_place_index_t<_Idx>> : true_type {};
    960 
    961 template <class _Tp>
    962 using __is_inplace_index = __is_inplace_index_imp<__uncvref_t<_Tp>>;
    963 
    964 #endif // _LIBCPP_STD_VER > 14
    965 
    966 template <class _Arg, class _Result>
    967 struct _LIBCPP_TEMPLATE_VIS unary_function
    968 {
    969     typedef _Arg    argument_type;
    970     typedef _Result result_type;
    971 };
    972 
    973 template <class _Size>
    974 inline _LIBCPP_INLINE_VISIBILITY
    975 _Size
    976 __loadword(const void* __p)
    977 {
    978     _Size __r;
    979     std::memcpy(&__r, __p, sizeof(__r));
    980     return __r;
    981 }
    982 
    983 // We use murmur2 when size_t is 32 bits, and cityhash64 when size_t
    984 // is 64 bits.  This is because cityhash64 uses 64bit x 64bit
    985 // multiplication, which can be very slow on 32-bit systems.
    986 template <class _Size, size_t = sizeof(_Size)*__CHAR_BIT__>
    987 struct __murmur2_or_cityhash;
    988 
    989 template <class _Size>
    990 struct __murmur2_or_cityhash<_Size, 32>
    991 {
    992     inline _Size operator()(const void* __key, _Size __len)
    993          _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK;
    994 };
    995 
    996 // murmur2
    997 template <class _Size>
    998 _Size
    999 __murmur2_or_cityhash<_Size, 32>::operator()(const void* __key, _Size __len)
   1000 {
   1001     const _Size __m = 0x5bd1e995;
   1002     const _Size __r = 24;
   1003     _Size __h = __len;
   1004     const unsigned char* __data = static_cast<const unsigned char*>(__key);
   1005     for (; __len >= 4; __data += 4, __len -= 4)
   1006     {
   1007         _Size __k = __loadword<_Size>(__data);
   1008         __k *= __m;
   1009         __k ^= __k >> __r;
   1010         __k *= __m;
   1011         __h *= __m;
   1012         __h ^= __k;
   1013     }
   1014     switch (__len)
   1015     {
   1016     case 3:
   1017         __h ^= __data[2] << 16;
   1018         _LIBCPP_FALLTHROUGH();
   1019     case 2:
   1020         __h ^= __data[1] << 8;
   1021         _LIBCPP_FALLTHROUGH();
   1022     case 1:
   1023         __h ^= __data[0];
   1024         __h *= __m;
   1025     }
   1026     __h ^= __h >> 13;
   1027     __h *= __m;
   1028     __h ^= __h >> 15;
   1029     return __h;
   1030 }
   1031 
   1032 template <class _Size>
   1033 struct __murmur2_or_cityhash<_Size, 64>
   1034 {
   1035     inline _Size operator()(const void* __key, _Size __len)  _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK;
   1036 
   1037  private:
   1038   // Some primes between 2^63 and 2^64.
   1039   static const _Size __k0 = 0xc3a5c85c97cb3127ULL;
   1040   static const _Size __k1 = 0xb492b66fbe98f273ULL;
   1041   static const _Size __k2 = 0x9ae16a3b2f90404fULL;
   1042   static const _Size __k3 = 0xc949d7c7509e6557ULL;
   1043 
   1044   static _Size __rotate(_Size __val, int __shift) {
   1045     return __shift == 0 ? __val : ((__val >> __shift) | (__val << (64 - __shift)));
   1046   }
   1047 
   1048   static _Size __rotate_by_at_least_1(_Size __val, int __shift) {
   1049     return (__val >> __shift) | (__val << (64 - __shift));
   1050   }
   1051 
   1052   static _Size __shift_mix(_Size __val) {
   1053     return __val ^ (__val >> 47);
   1054   }
   1055 
   1056   static _Size __hash_len_16(_Size __u, _Size __v)
   1057      _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
   1058   {
   1059     const _Size __mul = 0x9ddfea08eb382d69ULL;
   1060     _Size __a = (__u ^ __v) * __mul;
   1061     __a ^= (__a >> 47);
   1062     _Size __b = (__v ^ __a) * __mul;
   1063     __b ^= (__b >> 47);
   1064     __b *= __mul;
   1065     return __b;
   1066   }
   1067 
   1068   static _Size __hash_len_0_to_16(const char* __s, _Size __len)
   1069      _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
   1070   {
   1071     if (__len > 8) {
   1072       const _Size __a = __loadword<_Size>(__s);
   1073       const _Size __b = __loadword<_Size>(__s + __len - 8);
   1074       return __hash_len_16(__a, __rotate_by_at_least_1(__b + __len, __len)) ^ __b;
   1075     }
   1076     if (__len >= 4) {
   1077       const uint32_t __a = __loadword<uint32_t>(__s);
   1078       const uint32_t __b = __loadword<uint32_t>(__s + __len - 4);
   1079       return __hash_len_16(__len + (__a << 3), __b);
   1080     }
   1081     if (__len > 0) {
   1082       const unsigned char __a = __s[0];
   1083       const unsigned char __b = __s[__len >> 1];
   1084       const unsigned char __c = __s[__len - 1];
   1085       const uint32_t __y = static_cast<uint32_t>(__a) +
   1086                            (static_cast<uint32_t>(__b) << 8);
   1087       const uint32_t __z = __len + (static_cast<uint32_t>(__c) << 2);
   1088       return __shift_mix(__y * __k2 ^ __z * __k3) * __k2;
   1089     }
   1090     return __k2;
   1091   }
   1092 
   1093   static _Size __hash_len_17_to_32(const char *__s, _Size __len)
   1094      _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
   1095   {
   1096     const _Size __a = __loadword<_Size>(__s) * __k1;
   1097     const _Size __b = __loadword<_Size>(__s + 8);
   1098     const _Size __c = __loadword<_Size>(__s + __len - 8) * __k2;
   1099     const _Size __d = __loadword<_Size>(__s + __len - 16) * __k0;
   1100     return __hash_len_16(__rotate(__a - __b, 43) + __rotate(__c, 30) + __d,
   1101                          __a + __rotate(__b ^ __k3, 20) - __c + __len);
   1102   }
   1103 
   1104   // Return a 16-byte hash for 48 bytes.  Quick and dirty.
   1105   // Callers do best to use "random-looking" values for a and b.
   1106   static pair<_Size, _Size> __weak_hash_len_32_with_seeds(
   1107       _Size __w, _Size __x, _Size __y, _Size __z, _Size __a, _Size __b)
   1108         _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
   1109   {
   1110     __a += __w;
   1111     __b = __rotate(__b + __a + __z, 21);
   1112     const _Size __c = __a;
   1113     __a += __x;
   1114     __a += __y;
   1115     __b += __rotate(__a, 44);
   1116     return pair<_Size, _Size>(__a + __z, __b + __c);
   1117   }
   1118 
   1119   // Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.
   1120   static pair<_Size, _Size> __weak_hash_len_32_with_seeds(
   1121       const char* __s, _Size __a, _Size __b)
   1122     _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
   1123   {
   1124     return __weak_hash_len_32_with_seeds(__loadword<_Size>(__s),
   1125                                          __loadword<_Size>(__s + 8),
   1126                                          __loadword<_Size>(__s + 16),
   1127                                          __loadword<_Size>(__s + 24),
   1128                                          __a,
   1129                                          __b);
   1130   }
   1131 
   1132   // Return an 8-byte hash for 33 to 64 bytes.
   1133   static _Size __hash_len_33_to_64(const char *__s, size_t __len)
   1134     _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
   1135   {
   1136     _Size __z = __loadword<_Size>(__s + 24);
   1137     _Size __a = __loadword<_Size>(__s) +
   1138                 (__len + __loadword<_Size>(__s + __len - 16)) * __k0;
   1139     _Size __b = __rotate(__a + __z, 52);
   1140     _Size __c = __rotate(__a, 37);
   1141     __a += __loadword<_Size>(__s + 8);
   1142     __c += __rotate(__a, 7);
   1143     __a += __loadword<_Size>(__s + 16);
   1144     _Size __vf = __a + __z;
   1145     _Size __vs = __b + __rotate(__a, 31) + __c;
   1146     __a = __loadword<_Size>(__s + 16) + __loadword<_Size>(__s + __len - 32);
   1147     __z += __loadword<_Size>(__s + __len - 8);
   1148     __b = __rotate(__a + __z, 52);
   1149     __c = __rotate(__a, 37);
   1150     __a += __loadword<_Size>(__s + __len - 24);
   1151     __c += __rotate(__a, 7);
   1152     __a += __loadword<_Size>(__s + __len - 16);
   1153     _Size __wf = __a + __z;
   1154     _Size __ws = __b + __rotate(__a, 31) + __c;
   1155     _Size __r = __shift_mix((__vf + __ws) * __k2 + (__wf + __vs) * __k0);
   1156     return __shift_mix(__r * __k0 + __vs) * __k2;
   1157   }
   1158 };
   1159 
   1160 // cityhash64
   1161 template <class _Size>
   1162 _Size
   1163 __murmur2_or_cityhash<_Size, 64>::operator()(const void* __key, _Size __len)
   1164 {
   1165   const char* __s = static_cast<const char*>(__key);
   1166   if (__len <= 32) {
   1167     if (__len <= 16) {
   1168       return __hash_len_0_to_16(__s, __len);
   1169     } else {
   1170       return __hash_len_17_to_32(__s, __len);
   1171     }
   1172   } else if (__len <= 64) {
   1173     return __hash_len_33_to_64(__s, __len);
   1174   }
   1175 
   1176   // For strings over 64 bytes we hash the end first, and then as we
   1177   // loop we keep 56 bytes of state: v, w, x, y, and z.
   1178   _Size __x = __loadword<_Size>(__s + __len - 40);
   1179   _Size __y = __loadword<_Size>(__s + __len - 16) +
   1180               __loadword<_Size>(__s + __len - 56);
   1181   _Size __z = __hash_len_16(__loadword<_Size>(__s + __len - 48) + __len,
   1182                           __loadword<_Size>(__s + __len - 24));
   1183   pair<_Size, _Size> __v = __weak_hash_len_32_with_seeds(__s + __len - 64, __len, __z);
   1184   pair<_Size, _Size> __w = __weak_hash_len_32_with_seeds(__s + __len - 32, __y + __k1, __x);
   1185   __x = __x * __k1 + __loadword<_Size>(__s);
   1186 
   1187   // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.
   1188   __len = (__len - 1) & ~static_cast<_Size>(63);
   1189   do {
   1190     __x = __rotate(__x + __y + __v.first + __loadword<_Size>(__s + 8), 37) * __k1;
   1191     __y = __rotate(__y + __v.second + __loadword<_Size>(__s + 48), 42) * __k1;
   1192     __x ^= __w.second;
   1193     __y += __v.first + __loadword<_Size>(__s + 40);
   1194     __z = __rotate(__z + __w.first, 33) * __k1;
   1195     __v = __weak_hash_len_32_with_seeds(__s, __v.second * __k1, __x + __w.first);
   1196     __w = __weak_hash_len_32_with_seeds(__s + 32, __z + __w.second,
   1197                                         __y + __loadword<_Size>(__s + 16));
   1198     std::swap(__z, __x);
   1199     __s += 64;
   1200     __len -= 64;
   1201   } while (__len != 0);
   1202   return __hash_len_16(
   1203       __hash_len_16(__v.first, __w.first) + __shift_mix(__y) * __k1 + __z,
   1204       __hash_len_16(__v.second, __w.second) + __x);
   1205 }
   1206 
   1207 template <class _Tp, size_t = sizeof(_Tp) / sizeof(size_t)>
   1208 struct __scalar_hash;
   1209 
   1210 template <class _Tp>
   1211 struct __scalar_hash<_Tp, 0>
   1212     : public unary_function<_Tp, size_t>
   1213 {
   1214     _LIBCPP_INLINE_VISIBILITY
   1215     size_t operator()(_Tp __v) const _NOEXCEPT
   1216     {
   1217         union
   1218         {
   1219             _Tp    __t;
   1220             size_t __a;
   1221         } __u;
   1222         __u.__a = 0;
   1223         __u.__t = __v;
   1224         return __u.__a;
   1225     }
   1226 };
   1227 
   1228 template <class _Tp>
   1229 struct __scalar_hash<_Tp, 1>
   1230     : public unary_function<_Tp, size_t>
   1231 {
   1232     _LIBCPP_INLINE_VISIBILITY
   1233     size_t operator()(_Tp __v) const _NOEXCEPT
   1234     {
   1235         union
   1236         {
   1237             _Tp    __t;
   1238             size_t __a;
   1239         } __u;
   1240         __u.__t = __v;
   1241         return __u.__a;
   1242     }
   1243 };
   1244 
   1245 template <class _Tp>
   1246 struct __scalar_hash<_Tp, 2>
   1247     : public unary_function<_Tp, size_t>
   1248 {
   1249     _LIBCPP_INLINE_VISIBILITY
   1250     size_t operator()(_Tp __v) const _NOEXCEPT
   1251     {
   1252         union
   1253         {
   1254             _Tp __t;
   1255             struct
   1256             {
   1257                 size_t __a;
   1258                 size_t __b;
   1259             } __s;
   1260         } __u;
   1261         __u.__t = __v;
   1262         return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
   1263     }
   1264 };
   1265 
   1266 template <class _Tp>
   1267 struct __scalar_hash<_Tp, 3>
   1268     : public unary_function<_Tp, size_t>
   1269 {
   1270     _LIBCPP_INLINE_VISIBILITY
   1271     size_t operator()(_Tp __v) const _NOEXCEPT
   1272     {
   1273         union
   1274         {
   1275             _Tp __t;
   1276             struct
   1277             {
   1278                 size_t __a;
   1279                 size_t __b;
   1280                 size_t __c;
   1281             } __s;
   1282         } __u;
   1283         __u.__t = __v;
   1284         return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
   1285     }
   1286 };
   1287 
   1288 template <class _Tp>
   1289 struct __scalar_hash<_Tp, 4>
   1290     : public unary_function<_Tp, size_t>
   1291 {
   1292     _LIBCPP_INLINE_VISIBILITY
   1293     size_t operator()(_Tp __v) const _NOEXCEPT
   1294     {
   1295         union
   1296         {
   1297             _Tp __t;
   1298             struct
   1299             {
   1300                 size_t __a;
   1301                 size_t __b;
   1302                 size_t __c;
   1303                 size_t __d;
   1304             } __s;
   1305         } __u;
   1306         __u.__t = __v;
   1307         return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
   1308     }
   1309 };
   1310 
   1311 struct _PairT {
   1312   size_t first;
   1313   size_t second;
   1314 };
   1315 
   1316 _LIBCPP_INLINE_VISIBILITY
   1317 inline size_t __hash_combine(size_t __lhs, size_t __rhs) _NOEXCEPT {
   1318     typedef __scalar_hash<_PairT> _HashT;
   1319     const _PairT __p = {__lhs, __rhs};
   1320     return _HashT()(__p);
   1321 }
   1322 
   1323 template<class _Tp>
   1324 struct _LIBCPP_TEMPLATE_VIS hash<_Tp*>
   1325     : public unary_function<_Tp*, size_t>
   1326 {
   1327     _LIBCPP_INLINE_VISIBILITY
   1328     size_t operator()(_Tp* __v) const _NOEXCEPT
   1329     {
   1330         union
   1331         {
   1332             _Tp* __t;
   1333             size_t __a;
   1334         } __u;
   1335         __u.__t = __v;
   1336         return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
   1337     }
   1338 };
   1339 
   1340 
   1341 template <>
   1342 struct _LIBCPP_TEMPLATE_VIS hash<bool>
   1343     : public unary_function<bool, size_t>
   1344 {
   1345     _LIBCPP_INLINE_VISIBILITY
   1346     size_t operator()(bool __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
   1347 };
   1348 
   1349 template <>
   1350 struct _LIBCPP_TEMPLATE_VIS hash<char>
   1351     : public unary_function<char, size_t>
   1352 {
   1353     _LIBCPP_INLINE_VISIBILITY
   1354     size_t operator()(char __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
   1355 };
   1356 
   1357 template <>
   1358 struct _LIBCPP_TEMPLATE_VIS hash<signed char>
   1359     : public unary_function<signed char, size_t>
   1360 {
   1361     _LIBCPP_INLINE_VISIBILITY
   1362     size_t operator()(signed char __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
   1363 };
   1364 
   1365 template <>
   1366 struct _LIBCPP_TEMPLATE_VIS hash<unsigned char>
   1367     : public unary_function<unsigned char, size_t>
   1368 {
   1369     _LIBCPP_INLINE_VISIBILITY
   1370     size_t operator()(unsigned char __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
   1371 };
   1372 
   1373 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
   1374 
   1375 template <>
   1376 struct _LIBCPP_TEMPLATE_VIS hash<char16_t>
   1377     : public unary_function<char16_t, size_t>
   1378 {
   1379     _LIBCPP_INLINE_VISIBILITY
   1380     size_t operator()(char16_t __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
   1381 };
   1382 
   1383 template <>
   1384 struct _LIBCPP_TEMPLATE_VIS hash<char32_t>
   1385     : public unary_function<char32_t, size_t>
   1386 {
   1387     _LIBCPP_INLINE_VISIBILITY
   1388     size_t operator()(char32_t __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
   1389 };
   1390 
   1391 #endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
   1392 
   1393 template <>
   1394 struct _LIBCPP_TEMPLATE_VIS hash<wchar_t>
   1395     : public unary_function<wchar_t, size_t>
   1396 {
   1397     _LIBCPP_INLINE_VISIBILITY
   1398     size_t operator()(wchar_t __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
   1399 };
   1400 
   1401 template <>
   1402 struct _LIBCPP_TEMPLATE_VIS hash<short>
   1403     : public unary_function<short, size_t>
   1404 {
   1405     _LIBCPP_INLINE_VISIBILITY
   1406     size_t operator()(short __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
   1407 };
   1408 
   1409 template <>
   1410 struct _LIBCPP_TEMPLATE_VIS hash<unsigned short>
   1411     : public unary_function<unsigned short, size_t>
   1412 {
   1413     _LIBCPP_INLINE_VISIBILITY
   1414     size_t operator()(unsigned short __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
   1415 };
   1416 
   1417 template <>
   1418 struct _LIBCPP_TEMPLATE_VIS hash<int>
   1419     : public unary_function<int, size_t>
   1420 {
   1421     _LIBCPP_INLINE_VISIBILITY
   1422     size_t operator()(int __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
   1423 };
   1424 
   1425 template <>
   1426 struct _LIBCPP_TEMPLATE_VIS hash<unsigned int>
   1427     : public unary_function<unsigned int, size_t>
   1428 {
   1429     _LIBCPP_INLINE_VISIBILITY
   1430     size_t operator()(unsigned int __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
   1431 };
   1432 
   1433 template <>
   1434 struct _LIBCPP_TEMPLATE_VIS hash<long>
   1435     : public unary_function<long, size_t>
   1436 {
   1437     _LIBCPP_INLINE_VISIBILITY
   1438     size_t operator()(long __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
   1439 };
   1440 
   1441 template <>
   1442 struct _LIBCPP_TEMPLATE_VIS hash<unsigned long>
   1443     : public unary_function<unsigned long, size_t>
   1444 {
   1445     _LIBCPP_INLINE_VISIBILITY
   1446     size_t operator()(unsigned long __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
   1447 };
   1448 
   1449 template <>
   1450 struct _LIBCPP_TEMPLATE_VIS hash<long long>
   1451     : public __scalar_hash<long long>
   1452 {
   1453 };
   1454 
   1455 template <>
   1456 struct _LIBCPP_TEMPLATE_VIS hash<unsigned long long>
   1457     : public __scalar_hash<unsigned long long>
   1458 {
   1459 };
   1460 
   1461 #ifndef _LIBCPP_HAS_NO_INT128
   1462 
   1463 template <>
   1464 struct _LIBCPP_TEMPLATE_VIS hash<__int128_t>
   1465     : public __scalar_hash<__int128_t>
   1466 {
   1467 };
   1468 
   1469 template <>
   1470 struct _LIBCPP_TEMPLATE_VIS hash<__uint128_t>
   1471     : public __scalar_hash<__uint128_t>
   1472 {
   1473 };
   1474 
   1475 #endif
   1476 
   1477 template <>
   1478 struct _LIBCPP_TEMPLATE_VIS hash<float>
   1479     : public __scalar_hash<float>
   1480 {
   1481     _LIBCPP_INLINE_VISIBILITY
   1482     size_t operator()(float __v) const _NOEXCEPT
   1483     {
   1484         // -0.0 and 0.0 should return same hash
   1485        if (__v == 0.0)
   1486            return 0;
   1487         return __scalar_hash<float>::operator()(__v);
   1488     }
   1489 };
   1490 
   1491 template <>
   1492 struct _LIBCPP_TEMPLATE_VIS hash<double>
   1493     : public __scalar_hash<double>
   1494 {
   1495     _LIBCPP_INLINE_VISIBILITY
   1496     size_t operator()(double __v) const _NOEXCEPT
   1497     {
   1498         // -0.0 and 0.0 should return same hash
   1499        if (__v == 0.0)
   1500            return 0;
   1501         return __scalar_hash<double>::operator()(__v);
   1502     }
   1503 };
   1504 
   1505 template <>
   1506 struct _LIBCPP_TEMPLATE_VIS hash<long double>
   1507     : public __scalar_hash<long double>
   1508 {
   1509     _LIBCPP_INLINE_VISIBILITY
   1510     size_t operator()(long double __v) const _NOEXCEPT
   1511     {
   1512         // -0.0 and 0.0 should return same hash
   1513         if (__v == 0.0)
   1514             return 0;
   1515 #if defined(__i386__)
   1516         // Zero out padding bits
   1517         union
   1518         {
   1519             long double __t;
   1520             struct
   1521             {
   1522                 size_t __a;
   1523                 size_t __b;
   1524                 size_t __c;
   1525                 size_t __d;
   1526             } __s;
   1527         } __u;
   1528         __u.__s.__a = 0;
   1529         __u.__s.__b = 0;
   1530         __u.__s.__c = 0;
   1531         __u.__s.__d = 0;
   1532         __u.__t = __v;
   1533         return __u.__s.__a ^ __u.__s.__b ^ __u.__s.__c ^ __u.__s.__d;
   1534 #elif defined(__x86_64__)
   1535         // Zero out padding bits
   1536         union
   1537         {
   1538             long double __t;
   1539             struct
   1540             {
   1541                 size_t __a;
   1542                 size_t __b;
   1543             } __s;
   1544         } __u;
   1545         __u.__s.__a = 0;
   1546         __u.__s.__b = 0;
   1547         __u.__t = __v;
   1548         return __u.__s.__a ^ __u.__s.__b;
   1549 #else
   1550         return __scalar_hash<long double>::operator()(__v);
   1551 #endif
   1552     }
   1553 };
   1554 
   1555 #if _LIBCPP_STD_VER > 11
   1556 
   1557 template <class _Tp, bool = is_enum<_Tp>::value>
   1558 struct _LIBCPP_TEMPLATE_VIS __enum_hash
   1559     : public unary_function<_Tp, size_t>
   1560 {
   1561     _LIBCPP_INLINE_VISIBILITY
   1562     size_t operator()(_Tp __v) const _NOEXCEPT
   1563     {
   1564         typedef typename underlying_type<_Tp>::type type;
   1565         return hash<type>{}(static_cast<type>(__v));
   1566     }
   1567 };
   1568 template <class _Tp>
   1569 struct _LIBCPP_TEMPLATE_VIS __enum_hash<_Tp, false> {
   1570     __enum_hash() = delete;
   1571     __enum_hash(__enum_hash const&) = delete;
   1572     __enum_hash& operator=(__enum_hash const&) = delete;
   1573 };
   1574 
   1575 template <class _Tp>
   1576 struct _LIBCPP_TEMPLATE_VIS hash : public __enum_hash<_Tp>
   1577 {
   1578 };
   1579 #endif
   1580 
   1581 #if _LIBCPP_STD_VER > 14
   1582 
   1583 template <>
   1584 struct _LIBCPP_TEMPLATE_VIS hash<nullptr_t>
   1585   : public unary_function<nullptr_t, size_t>
   1586 {
   1587   _LIBCPP_INLINE_VISIBILITY
   1588   size_t operator()(nullptr_t) const _NOEXCEPT {
   1589     return 662607004ull;
   1590   }
   1591 };
   1592 #endif
   1593 
   1594 #ifndef _LIBCPP_CXX03_LANG
   1595 template <class _Key, class _Hash>
   1596 using __check_hash_requirements = integral_constant<bool,
   1597     is_copy_constructible<_Hash>::value &&
   1598     is_move_constructible<_Hash>::value &&
   1599     __invokable_r<size_t, _Hash, _Key const&>::value
   1600 >;
   1601 
   1602 template <class _Key, class _Hash = std::hash<_Key> >
   1603 using __has_enabled_hash = integral_constant<bool,
   1604     __check_hash_requirements<_Key, _Hash>::value &&
   1605     is_default_constructible<_Hash>::value
   1606 >;
   1607 
   1608 #if _LIBCPP_STD_VER > 14
   1609 template <class _Type, class>
   1610 using __enable_hash_helper_imp = _Type;
   1611 
   1612 template <class _Type, class ..._Keys>
   1613 using __enable_hash_helper = __enable_hash_helper_imp<_Type,
   1614   typename enable_if<__all<__has_enabled_hash<_Keys>::value...>::value>::type
   1615 >;
   1616 #else
   1617 template <class _Type, class ...>
   1618 using __enable_hash_helper = _Type;
   1619 #endif
   1620 
   1621 #endif // !_LIBCPP_CXX03_LANG
   1622 
   1623 _LIBCPP_END_NAMESPACE_STD
   1624 
   1625 #endif  // _LIBCPP_UTILITY