1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef _LIBCPP___FUNCTIONAL_HASH_H
10 #define _LIBCPP___FUNCTIONAL_HASH_H
11 
12 #include <__config>
13 #include <__functional/invoke.h>
14 #include <__functional/unary_function.h>
15 #include <__fwd/hash.h>
16 #include <__tuple_dir/sfinae_helpers.h>
17 #include <__type_traits/is_copy_constructible.h>
18 #include <__type_traits/is_default_constructible.h>
19 #include <__type_traits/is_enum.h>
20 #include <__type_traits/is_move_constructible.h>
21 #include <__type_traits/underlying_type.h>
22 #include <__utility/forward.h>
23 #include <__utility/move.h>
24 #include <__utility/pair.h>
25 #include <__utility/swap.h>
26 #include <cstddef>
27 #include <cstdint>
28 #include <cstring>
29 #include <limits>
30 
31 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
32 #  pragma GCC system_header
33 #endif
34 
35 _LIBCPP_BEGIN_NAMESPACE_STD
36 
37 template <class _Size>
38 inline _LIBCPP_INLINE_VISIBILITY
39 _Size
40 __loadword(const void* __p)
41 {
42     _Size __r;
43     _VSTD::memcpy(&__r, __p, sizeof(__r));
44     return __r;
45 }
46 
47 // We use murmur2 when size_t is 32 bits, and cityhash64 when size_t
48 // is 64 bits.  This is because cityhash64 uses 64bit x 64bit
49 // multiplication, which can be very slow on 32-bit systems.
50 template <class _Size, size_t = sizeof(_Size)*__CHAR_BIT__>
51 struct __murmur2_or_cityhash;
52 
53 template <class _Size>
54 struct __murmur2_or_cityhash<_Size, 32>
55 {
56     inline _Size operator()(const void* __key, _Size __len)
57          _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK;
58 };
59 
60 // murmur2
61 template <class _Size>
62 _Size
63 __murmur2_or_cityhash<_Size, 32>::operator()(const void* __key, _Size __len)
64 {
65     const _Size __m = 0x5bd1e995;
66     const _Size __r = 24;
67     _Size __h = __len;
68     const unsigned char* __data = static_cast<const unsigned char*>(__key);
69     for (; __len >= 4; __data += 4, __len -= 4)
70     {
71         _Size __k = std::__loadword<_Size>(__data);
72         __k *= __m;
73         __k ^= __k >> __r;
74         __k *= __m;
75         __h *= __m;
76         __h ^= __k;
77     }
78     switch (__len)
79     {
80     case 3:
81         __h ^= static_cast<_Size>(__data[2] << 16);
82         _LIBCPP_FALLTHROUGH();
83     case 2:
84         __h ^= static_cast<_Size>(__data[1] << 8);
85         _LIBCPP_FALLTHROUGH();
86     case 1:
87         __h ^= __data[0];
88         __h *= __m;
89     }
90     __h ^= __h >> 13;
91     __h *= __m;
92     __h ^= __h >> 15;
93     return __h;
94 }
95 
96 template <class _Size>
97 struct __murmur2_or_cityhash<_Size, 64>
98 {
99     inline _Size operator()(const void* __key, _Size __len)  _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK;
100 
101  private:
102   // Some primes between 2^63 and 2^64.
103   static const _Size __k0 = 0xc3a5c85c97cb3127ULL;
104   static const _Size __k1 = 0xb492b66fbe98f273ULL;
105   static const _Size __k2 = 0x9ae16a3b2f90404fULL;
106   static const _Size __k3 = 0xc949d7c7509e6557ULL;
107 
108   static _Size __rotate(_Size __val, int __shift) {
109     return __shift == 0 ? __val : ((__val >> __shift) | (__val << (64 - __shift)));
110   }
111 
112   static _Size __rotate_by_at_least_1(_Size __val, int __shift) {
113     return (__val >> __shift) | (__val << (64 - __shift));
114   }
115 
116   static _Size __shift_mix(_Size __val) {
117     return __val ^ (__val >> 47);
118   }
119 
120   static _Size __hash_len_16(_Size __u, _Size __v)
121      _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
122   {
123     const _Size __mul = 0x9ddfea08eb382d69ULL;
124     _Size __a = (__u ^ __v) * __mul;
125     __a ^= (__a >> 47);
126     _Size __b = (__v ^ __a) * __mul;
127     __b ^= (__b >> 47);
128     __b *= __mul;
129     return __b;
130   }
131 
132   static _Size __hash_len_0_to_16(const char* __s, _Size __len)
133      _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
134   {
135     if (__len > 8) {
136       const _Size __a = std::__loadword<_Size>(__s);
137       const _Size __b = std::__loadword<_Size>(__s + __len - 8);
138       return __hash_len_16(__a, __rotate_by_at_least_1(__b + __len, __len)) ^ __b;
139     }
140     if (__len >= 4) {
141       const uint32_t __a = std::__loadword<uint32_t>(__s);
142       const uint32_t __b = std::__loadword<uint32_t>(__s + __len - 4);
143 #ifdef _LIBCPP_ABI_FIX_CITYHASH_IMPLEMENTATION
144       return __hash_len_16(__len + (static_cast<_Size>(__a) << 3), __b);
145 #else
146       return __hash_len_16(__len + (__a << 3), __b);
147 #endif
148     }
149     if (__len > 0) {
150       const unsigned char __a = static_cast<unsigned char>(__s[0]);
151       const unsigned char __b = static_cast<unsigned char>(__s[__len >> 1]);
152       const unsigned char __c = static_cast<unsigned char>(__s[__len - 1]);
153       const uint32_t __y = static_cast<uint32_t>(__a) +
154                            (static_cast<uint32_t>(__b) << 8);
155       const uint32_t __z = __len + (static_cast<uint32_t>(__c) << 2);
156       return __shift_mix(__y * __k2 ^ __z * __k3) * __k2;
157     }
158     return __k2;
159   }
160 
161   static _Size __hash_len_17_to_32(const char *__s, _Size __len)
162      _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
163   {
164     const _Size __a = std::__loadword<_Size>(__s) * __k1;
165     const _Size __b = std::__loadword<_Size>(__s + 8);
166     const _Size __c = std::__loadword<_Size>(__s + __len - 8) * __k2;
167     const _Size __d = std::__loadword<_Size>(__s + __len - 16) * __k0;
168     return __hash_len_16(__rotate(__a - __b, 43) + __rotate(__c, 30) + __d,
169                          __a + __rotate(__b ^ __k3, 20) - __c + __len);
170   }
171 
172   // Return a 16-byte hash for 48 bytes.  Quick and dirty.
173   // Callers do best to use "random-looking" values for a and b.
174   static pair<_Size, _Size> __weak_hash_len_32_with_seeds(
175       _Size __w, _Size __x, _Size __y, _Size __z, _Size __a, _Size __b)
176         _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
177   {
178     __a += __w;
179     __b = __rotate(__b + __a + __z, 21);
180     const _Size __c = __a;
181     __a += __x;
182     __a += __y;
183     __b += __rotate(__a, 44);
184     return pair<_Size, _Size>(__a + __z, __b + __c);
185   }
186 
187   // Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.
188   static pair<_Size, _Size> __weak_hash_len_32_with_seeds(
189       const char* __s, _Size __a, _Size __b)
190     _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
191   {
192     return __weak_hash_len_32_with_seeds(std::__loadword<_Size>(__s),
193                                          std::__loadword<_Size>(__s + 8),
194                                          std::__loadword<_Size>(__s + 16),
195                                          std::__loadword<_Size>(__s + 24),
196                                          __a,
197                                          __b);
198   }
199 
200   // Return an 8-byte hash for 33 to 64 bytes.
201   static _Size __hash_len_33_to_64(const char *__s, size_t __len)
202     _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
203   {
204     _Size __z = std::__loadword<_Size>(__s + 24);
205     _Size __a = std::__loadword<_Size>(__s) +
206                 (__len + std::__loadword<_Size>(__s + __len - 16)) * __k0;
207     _Size __b = __rotate(__a + __z, 52);
208     _Size __c = __rotate(__a, 37);
209     __a += std::__loadword<_Size>(__s + 8);
210     __c += __rotate(__a, 7);
211     __a += std::__loadword<_Size>(__s + 16);
212     _Size __vf = __a + __z;
213     _Size __vs = __b + __rotate(__a, 31) + __c;
214     __a = std::__loadword<_Size>(__s + 16) + std::__loadword<_Size>(__s + __len - 32);
215     __z += std::__loadword<_Size>(__s + __len - 8);
216     __b = __rotate(__a + __z, 52);
217     __c = __rotate(__a, 37);
218     __a += std::__loadword<_Size>(__s + __len - 24);
219     __c += __rotate(__a, 7);
220     __a += std::__loadword<_Size>(__s + __len - 16);
221     _Size __wf = __a + __z;
222     _Size __ws = __b + __rotate(__a, 31) + __c;
223     _Size __r = __shift_mix((__vf + __ws) * __k2 + (__wf + __vs) * __k0);
224     return __shift_mix(__r * __k0 + __vs) * __k2;
225   }
226 };
227 
228 // cityhash64
229 template <class _Size>
230 _Size
231 __murmur2_or_cityhash<_Size, 64>::operator()(const void* __key, _Size __len)
232 {
233   const char* __s = static_cast<const char*>(__key);
234   if (__len <= 32) {
235     if (__len <= 16) {
236       return __hash_len_0_to_16(__s, __len);
237     } else {
238       return __hash_len_17_to_32(__s, __len);
239     }
240   } else if (__len <= 64) {
241     return __hash_len_33_to_64(__s, __len);
242   }
243 
244   // For strings over 64 bytes we hash the end first, and then as we
245   // loop we keep 56 bytes of state: v, w, x, y, and z.
246   _Size __x = std::__loadword<_Size>(__s + __len - 40);
247   _Size __y = std::__loadword<_Size>(__s + __len - 16) +
248               std::__loadword<_Size>(__s + __len - 56);
249   _Size __z = __hash_len_16(std::__loadword<_Size>(__s + __len - 48) + __len,
250                           std::__loadword<_Size>(__s + __len - 24));
251   pair<_Size, _Size> __v = __weak_hash_len_32_with_seeds(__s + __len - 64, __len, __z);
252   pair<_Size, _Size> __w = __weak_hash_len_32_with_seeds(__s + __len - 32, __y + __k1, __x);
253   __x = __x * __k1 + std::__loadword<_Size>(__s);
254 
255   // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.
256   __len = (__len - 1) & ~static_cast<_Size>(63);
257   do {
258     __x = __rotate(__x + __y + __v.first + std::__loadword<_Size>(__s + 8), 37) * __k1;
259     __y = __rotate(__y + __v.second + std::__loadword<_Size>(__s + 48), 42) * __k1;
260     __x ^= __w.second;
261     __y += __v.first + std::__loadword<_Size>(__s + 40);
262     __z = __rotate(__z + __w.first, 33) * __k1;
263     __v = __weak_hash_len_32_with_seeds(__s, __v.second * __k1, __x + __w.first);
264     __w = __weak_hash_len_32_with_seeds(__s + 32, __z + __w.second,
265                                         __y + std::__loadword<_Size>(__s + 16));
266     _VSTD::swap(__z, __x);
267     __s += 64;
268     __len -= 64;
269   } while (__len != 0);
270   return __hash_len_16(
271       __hash_len_16(__v.first, __w.first) + __shift_mix(__y) * __k1 + __z,
272       __hash_len_16(__v.second, __w.second) + __x);
273 }
274 
275 template <class _Tp, size_t = sizeof(_Tp) / sizeof(size_t)>
276 struct __scalar_hash;
277 
278 template <class _Tp>
279 struct __scalar_hash<_Tp, 0>
280     : public __unary_function<_Tp, size_t>
281 {
282     _LIBCPP_INLINE_VISIBILITY
283     size_t operator()(_Tp __v) const _NOEXCEPT
284     {
285         union
286         {
287             _Tp    __t;
288             size_t __a;
289         } __u;
290         __u.__a = 0;
291         __u.__t = __v;
292         return __u.__a;
293     }
294 };
295 
296 template <class _Tp>
297 struct __scalar_hash<_Tp, 1>
298     : public __unary_function<_Tp, size_t>
299 {
300     _LIBCPP_INLINE_VISIBILITY
301     size_t operator()(_Tp __v) const _NOEXCEPT
302     {
303         union
304         {
305             _Tp    __t;
306             size_t __a;
307         } __u;
308         __u.__t = __v;
309         return __u.__a;
310     }
311 };
312 
313 template <class _Tp>
314 struct __scalar_hash<_Tp, 2>
315     : public __unary_function<_Tp, size_t>
316 {
317     _LIBCPP_INLINE_VISIBILITY
318     size_t operator()(_Tp __v) const _NOEXCEPT
319     {
320         union
321         {
322             _Tp __t;
323             struct
324             {
325                 size_t __a;
326                 size_t __b;
327             } __s;
328         } __u;
329         __u.__t = __v;
330         return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
331     }
332 };
333 
334 template <class _Tp>
335 struct __scalar_hash<_Tp, 3>
336     : public __unary_function<_Tp, size_t>
337 {
338     _LIBCPP_INLINE_VISIBILITY
339     size_t operator()(_Tp __v) const _NOEXCEPT
340     {
341         union
342         {
343             _Tp __t;
344             struct
345             {
346                 size_t __a;
347                 size_t __b;
348                 size_t __c;
349             } __s;
350         } __u;
351         __u.__t = __v;
352         return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
353     }
354 };
355 
356 template <class _Tp>
357 struct __scalar_hash<_Tp, 4>
358     : public __unary_function<_Tp, size_t>
359 {
360     _LIBCPP_INLINE_VISIBILITY
361     size_t operator()(_Tp __v) const _NOEXCEPT
362     {
363         union
364         {
365             _Tp __t;
366             struct
367             {
368                 size_t __a;
369                 size_t __b;
370                 size_t __c;
371                 size_t __d;
372             } __s;
373         } __u;
374         __u.__t = __v;
375         return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
376     }
377 };
378 
379 struct _PairT {
380   size_t first;
381   size_t second;
382 };
383 
384 _LIBCPP_INLINE_VISIBILITY
385 inline size_t __hash_combine(size_t __lhs, size_t __rhs) _NOEXCEPT {
386     typedef __scalar_hash<_PairT> _HashT;
387     const _PairT __p = {__lhs, __rhs};
388     return _HashT()(__p);
389 }
390 
391 template<class _Tp>
392 struct _LIBCPP_TEMPLATE_VIS hash<_Tp*>
393     : public __unary_function<_Tp*, size_t>
394 {
395     _LIBCPP_INLINE_VISIBILITY
396     size_t operator()(_Tp* __v) const _NOEXCEPT
397     {
398         union
399         {
400             _Tp* __t;
401             size_t __a;
402         } __u;
403         __u.__t = __v;
404         return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
405     }
406 };
407 
408 template <>
409 struct _LIBCPP_TEMPLATE_VIS hash<bool>
410     : public __unary_function<bool, size_t>
411 {
412     _LIBCPP_INLINE_VISIBILITY
413     size_t operator()(bool __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
414 };
415 
416 template <>
417 struct _LIBCPP_TEMPLATE_VIS hash<char>
418     : public __unary_function<char, size_t>
419 {
420     _LIBCPP_INLINE_VISIBILITY
421     size_t operator()(char __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
422 };
423 
424 template <>
425 struct _LIBCPP_TEMPLATE_VIS hash<signed char>
426     : public __unary_function<signed char, size_t>
427 {
428     _LIBCPP_INLINE_VISIBILITY
429     size_t operator()(signed char __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
430 };
431 
432 template <>
433 struct _LIBCPP_TEMPLATE_VIS hash<unsigned char>
434     : public __unary_function<unsigned char, size_t>
435 {
436     _LIBCPP_INLINE_VISIBILITY
437     size_t operator()(unsigned char __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
438 };
439 
440 #ifndef _LIBCPP_HAS_NO_CHAR8_T
441 template <>
442 struct _LIBCPP_TEMPLATE_VIS hash<char8_t>
443     : public __unary_function<char8_t, size_t>
444 {
445     _LIBCPP_INLINE_VISIBILITY
446     size_t operator()(char8_t __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
447 };
448 #endif // !_LIBCPP_HAS_NO_CHAR8_T
449 
450 template <>
451 struct _LIBCPP_TEMPLATE_VIS hash<char16_t>
452     : public __unary_function<char16_t, size_t>
453 {
454     _LIBCPP_INLINE_VISIBILITY
455     size_t operator()(char16_t __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
456 };
457 
458 template <>
459 struct _LIBCPP_TEMPLATE_VIS hash<char32_t>
460     : public __unary_function<char32_t, size_t>
461 {
462     _LIBCPP_INLINE_VISIBILITY
463     size_t operator()(char32_t __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
464 };
465 
466 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
467 template <>
468 struct _LIBCPP_TEMPLATE_VIS hash<wchar_t>
469     : public __unary_function<wchar_t, size_t>
470 {
471     _LIBCPP_INLINE_VISIBILITY
472     size_t operator()(wchar_t __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
473 };
474 #endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS
475 
476 template <>
477 struct _LIBCPP_TEMPLATE_VIS hash<short>
478     : public __unary_function<short, size_t>
479 {
480     _LIBCPP_INLINE_VISIBILITY
481     size_t operator()(short __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
482 };
483 
484 template <>
485 struct _LIBCPP_TEMPLATE_VIS hash<unsigned short>
486     : public __unary_function<unsigned short, size_t>
487 {
488     _LIBCPP_INLINE_VISIBILITY
489     size_t operator()(unsigned short __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
490 };
491 
492 template <>
493 struct _LIBCPP_TEMPLATE_VIS hash<int>
494     : public __unary_function<int, size_t>
495 {
496     _LIBCPP_INLINE_VISIBILITY
497     size_t operator()(int __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
498 };
499 
500 template <>
501 struct _LIBCPP_TEMPLATE_VIS hash<unsigned int>
502     : public __unary_function<unsigned int, size_t>
503 {
504     _LIBCPP_INLINE_VISIBILITY
505     size_t operator()(unsigned int __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
506 };
507 
508 template <>
509 struct _LIBCPP_TEMPLATE_VIS hash<long>
510     : public __unary_function<long, size_t>
511 {
512     _LIBCPP_INLINE_VISIBILITY
513     size_t operator()(long __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
514 };
515 
516 template <>
517 struct _LIBCPP_TEMPLATE_VIS hash<unsigned long>
518     : public __unary_function<unsigned long, size_t>
519 {
520     _LIBCPP_INLINE_VISIBILITY
521     size_t operator()(unsigned long __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
522 };
523 
524 template <>
525 struct _LIBCPP_TEMPLATE_VIS hash<long long>
526     : public __scalar_hash<long long>
527 {
528 };
529 
530 template <>
531 struct _LIBCPP_TEMPLATE_VIS hash<unsigned long long>
532     : public __scalar_hash<unsigned long long>
533 {
534 };
535 
536 #ifndef _LIBCPP_HAS_NO_INT128
537 
538 template <>
539 struct _LIBCPP_TEMPLATE_VIS hash<__int128_t>
540     : public __scalar_hash<__int128_t>
541 {
542 };
543 
544 template <>
545 struct _LIBCPP_TEMPLATE_VIS hash<__uint128_t>
546     : public __scalar_hash<__uint128_t>
547 {
548 };
549 
550 #endif
551 
552 template <>
553 struct _LIBCPP_TEMPLATE_VIS hash<float>
554     : public __scalar_hash<float>
555 {
556     _LIBCPP_INLINE_VISIBILITY
557     size_t operator()(float __v) const _NOEXCEPT
558     {
559         // -0.0 and 0.0 should return same hash
560        if (__v == 0.0f)
561            return 0;
562         return __scalar_hash<float>::operator()(__v);
563     }
564 };
565 
566 template <>
567 struct _LIBCPP_TEMPLATE_VIS hash<double>
568     : public __scalar_hash<double>
569 {
570     _LIBCPP_INLINE_VISIBILITY
571     size_t operator()(double __v) const _NOEXCEPT
572     {
573         // -0.0 and 0.0 should return same hash
574        if (__v == 0.0)
575            return 0;
576         return __scalar_hash<double>::operator()(__v);
577     }
578 };
579 
580 template <>
581 struct _LIBCPP_TEMPLATE_VIS hash<long double>
582     : public __scalar_hash<long double>
583 {
584     _LIBCPP_INLINE_VISIBILITY
585     size_t operator()(long double __v) const _NOEXCEPT
586     {
587         // -0.0 and 0.0 should return same hash
588         if (__v == 0.0L)
589             return 0;
590 #if defined(__i386__) || (defined(__x86_64__) && defined(__ILP32__))
591         // Zero out padding bits
592         union
593         {
594             long double __t;
595             struct
596             {
597                 size_t __a;
598                 size_t __b;
599                 size_t __c;
600                 size_t __d;
601             } __s;
602         } __u;
603         __u.__s.__a = 0;
604         __u.__s.__b = 0;
605         __u.__s.__c = 0;
606         __u.__s.__d = 0;
607         __u.__t = __v;
608         return __u.__s.__a ^ __u.__s.__b ^ __u.__s.__c ^ __u.__s.__d;
609 #elif defined(__x86_64__)
610         // Zero out padding bits
611         union
612         {
613             long double __t;
614             struct
615             {
616                 size_t __a;
617                 size_t __b;
618             } __s;
619         } __u;
620         __u.__s.__a = 0;
621         __u.__s.__b = 0;
622         __u.__t = __v;
623         return __u.__s.__a ^ __u.__s.__b;
624 #else
625         return __scalar_hash<long double>::operator()(__v);
626 #endif
627     }
628 };
629 
630 template <class _Tp, bool = is_enum<_Tp>::value>
631 struct _LIBCPP_TEMPLATE_VIS __enum_hash
632     : public __unary_function<_Tp, size_t>
633 {
634     _LIBCPP_INLINE_VISIBILITY
635     size_t operator()(_Tp __v) const _NOEXCEPT
636     {
637         typedef typename underlying_type<_Tp>::type type;
638         return hash<type>()(static_cast<type>(__v));
639     }
640 };
641 template <class _Tp>
642 struct _LIBCPP_TEMPLATE_VIS __enum_hash<_Tp, false> {
643     __enum_hash() = delete;
644     __enum_hash(__enum_hash const&) = delete;
645     __enum_hash& operator=(__enum_hash const&) = delete;
646 };
647 
648 template <class _Tp>
649 struct _LIBCPP_TEMPLATE_VIS hash : public __enum_hash<_Tp>
650 {
651 };
652 
653 #if _LIBCPP_STD_VER > 14
654 
655 template <>
656 struct _LIBCPP_TEMPLATE_VIS hash<nullptr_t>
657   : public __unary_function<nullptr_t, size_t>
658 {
659     _LIBCPP_INLINE_VISIBILITY
660     size_t operator()(nullptr_t) const _NOEXCEPT {
661         return 662607004ull;
662     }
663 };
664 #endif
665 
666 #ifndef _LIBCPP_CXX03_LANG
667 template <class _Key, class _Hash>
668 using __check_hash_requirements _LIBCPP_NODEBUG = integral_constant<bool,
669     is_copy_constructible<_Hash>::value &&
670     is_move_constructible<_Hash>::value &&
671     __invokable_r<size_t, _Hash, _Key const&>::value
672 >;
673 
674 template <class _Key, class _Hash = hash<_Key> >
675 using __has_enabled_hash _LIBCPP_NODEBUG = integral_constant<bool,
676     __check_hash_requirements<_Key, _Hash>::value &&
677     is_default_constructible<_Hash>::value
678 >;
679 
680 #if _LIBCPP_STD_VER > 14
681 template <class _Type, class>
682 using __enable_hash_helper_imp _LIBCPP_NODEBUG = _Type;
683 
684 template <class _Type, class ..._Keys>
685 using __enable_hash_helper _LIBCPP_NODEBUG = __enable_hash_helper_imp<_Type,
686   typename enable_if<__all<__has_enabled_hash<_Keys>::value...>::value>::type
687 >;
688 #else
689 template <class _Type, class ...>
690 using __enable_hash_helper _LIBCPP_NODEBUG = _Type;
691 #endif
692 
693 #endif // !_LIBCPP_CXX03_LANG
694 
695 _LIBCPP_END_NAMESPACE_STD
696 
697 #endif // _LIBCPP___FUNCTIONAL_HASH_H
698