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/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>
__loadword(const void * __p)38 inline _LIBCPP_HIDE_FROM_ABI _Size __loadword(const void* __p) {
39   _Size __r;
40   std::memcpy(&__r, __p, sizeof(__r));
41   return __r;
42 }
43 
44 // We use murmur2 when size_t is 32 bits, and cityhash64 when size_t
45 // is 64 bits.  This is because cityhash64 uses 64bit x 64bit
46 // multiplication, which can be very slow on 32-bit systems.
47 template <class _Size, size_t = sizeof(_Size) * __CHAR_BIT__>
48 struct __murmur2_or_cityhash;
49 
50 template <class _Size>
51 struct __murmur2_or_cityhash<_Size, 32> {
52   _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK _Size
53   operator()(const void* __key, _Size __len) const {
54     // murmur2
55     const _Size __m             = 0x5bd1e995;
56     const _Size __r             = 24;
57     _Size __h                   = __len;
58     const unsigned char* __data = static_cast<const unsigned char*>(__key);
59     for (; __len >= 4; __data += 4, __len -= 4) {
60       _Size __k = std::__loadword<_Size>(__data);
61       __k *= __m;
62       __k ^= __k >> __r;
63       __k *= __m;
64       __h *= __m;
65       __h ^= __k;
66     }
67     switch (__len) {
68     case 3:
69       __h ^= static_cast<_Size>(__data[2] << 16);
70       _LIBCPP_FALLTHROUGH();
71     case 2:
72       __h ^= static_cast<_Size>(__data[1] << 8);
73       _LIBCPP_FALLTHROUGH();
74     case 1:
75       __h ^= __data[0];
76       __h *= __m;
77     }
78     __h ^= __h >> 13;
79     __h *= __m;
80     __h ^= __h >> 15;
81     return __h;
82   }
83 };
84 
85 template <class _Size>
86 struct __murmur2_or_cityhash<_Size, 64> {
87   // cityhash64
88   _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK _Size
89   operator()(const void* __key, _Size __len) const {
90     const char* __s = static_cast<const char*>(__key);
91     if (__len <= 32) {
92       if (__len <= 16) {
93         return __hash_len_0_to_16(__s, __len);
94       } else {
95         return __hash_len_17_to_32(__s, __len);
96       }
97     } else if (__len <= 64) {
98       return __hash_len_33_to_64(__s, __len);
99     }
100 
101     // For strings over 64 bytes we hash the end first, and then as we
102     // loop we keep 56 bytes of state: v, w, x, y, and z.
103     _Size __x = std::__loadword<_Size>(__s + __len - 40);
104     _Size __y = std::__loadword<_Size>(__s + __len - 16) + std::__loadword<_Size>(__s + __len - 56);
105     _Size __z =
106         __hash_len_16(std::__loadword<_Size>(__s + __len - 48) + __len, std::__loadword<_Size>(__s + __len - 24));
107     pair<_Size, _Size> __v = __weak_hash_len_32_with_seeds(__s + __len - 64, __len, __z);
108     pair<_Size, _Size> __w = __weak_hash_len_32_with_seeds(__s + __len - 32, __y + __k1, __x);
109     __x                    = __x * __k1 + std::__loadword<_Size>(__s);
110 
111     // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.
112     __len = (__len - 1) & ~static_cast<_Size>(63);
113     do {
114       __x = __rotate(__x + __y + __v.first + std::__loadword<_Size>(__s + 8), 37) * __k1;
115       __y = __rotate(__y + __v.second + std::__loadword<_Size>(__s + 48), 42) * __k1;
116       __x ^= __w.second;
117       __y += __v.first + std::__loadword<_Size>(__s + 40);
118       __z = __rotate(__z + __w.first, 33) * __k1;
119       __v = __weak_hash_len_32_with_seeds(__s, __v.second * __k1, __x + __w.first);
120       __w = __weak_hash_len_32_with_seeds(__s + 32, __z + __w.second, __y + std::__loadword<_Size>(__s + 16));
121       std::swap(__z, __x);
122       __s += 64;
123       __len -= 64;
124     } while (__len != 0);
125     return __hash_len_16(__hash_len_16(__v.first, __w.first) + __shift_mix(__y) * __k1 + __z,
126                          __hash_len_16(__v.second, __w.second) + __x);
127   }
128 
129 private:
130   // Some primes between 2^63 and 2^64.
131   static const _Size __k0 = 0xc3a5c85c97cb3127ULL;
132   static const _Size __k1 = 0xb492b66fbe98f273ULL;
133   static const _Size __k2 = 0x9ae16a3b2f90404fULL;
134   static const _Size __k3 = 0xc949d7c7509e6557ULL;
135 
136   _LIBCPP_HIDE_FROM_ABI static _Size __rotate(_Size __val, int __shift) {
137     return __shift == 0 ? __val : ((__val >> __shift) | (__val << (64 - __shift)));
138   }
139 
140   _LIBCPP_HIDE_FROM_ABI static _Size __rotate_by_at_least_1(_Size __val, int __shift) {
141     return (__val >> __shift) | (__val << (64 - __shift));
142   }
143 
144   _LIBCPP_HIDE_FROM_ABI static _Size __shift_mix(_Size __val) { return __val ^ (__val >> 47); }
145 
146   _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK static _Size __hash_len_16(_Size __u, _Size __v) {
147     const _Size __mul = 0x9ddfea08eb382d69ULL;
148     _Size __a         = (__u ^ __v) * __mul;
149     __a ^= (__a >> 47);
150     _Size __b = (__v ^ __a) * __mul;
151     __b ^= (__b >> 47);
152     __b *= __mul;
153     return __b;
154   }
155 
156   _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK static _Size
157   __hash_len_0_to_16(const char* __s, _Size __len) {
158     if (__len > 8) {
159       const _Size __a = std::__loadword<_Size>(__s);
160       const _Size __b = std::__loadword<_Size>(__s + __len - 8);
161       return __hash_len_16(__a, __rotate_by_at_least_1(__b + __len, __len)) ^ __b;
162     }
163     if (__len >= 4) {
164       const uint32_t __a = std::__loadword<uint32_t>(__s);
165       const uint32_t __b = std::__loadword<uint32_t>(__s + __len - 4);
166 #ifdef _LIBCPP_ABI_FIX_CITYHASH_IMPLEMENTATION
167       return __hash_len_16(__len + (static_cast<_Size>(__a) << 3), __b);
168 #else
169       return __hash_len_16(__len + (__a << 3), __b);
170 #endif
171     }
172     if (__len > 0) {
173       const unsigned char __a = static_cast<unsigned char>(__s[0]);
174       const unsigned char __b = static_cast<unsigned char>(__s[__len >> 1]);
175       const unsigned char __c = static_cast<unsigned char>(__s[__len - 1]);
176       const uint32_t __y      = static_cast<uint32_t>(__a) + (static_cast<uint32_t>(__b) << 8);
177       const uint32_t __z      = __len + (static_cast<uint32_t>(__c) << 2);
178       return __shift_mix(__y * __k2 ^ __z * __k3) * __k2;
179     }
180     return __k2;
181   }
182 
183   _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK static _Size
184   __hash_len_17_to_32(const char* __s, _Size __len) {
185     const _Size __a = std::__loadword<_Size>(__s) * __k1;
186     const _Size __b = std::__loadword<_Size>(__s + 8);
187     const _Size __c = std::__loadword<_Size>(__s + __len - 8) * __k2;
188     const _Size __d = std::__loadword<_Size>(__s + __len - 16) * __k0;
189     return __hash_len_16(
190         __rotate(__a - __b, 43) + __rotate(__c, 30) + __d, __a + __rotate(__b ^ __k3, 20) - __c + __len);
191   }
192 
193   // Return a 16-byte hash for 48 bytes.  Quick and dirty.
194   // Callers do best to use "random-looking" values for a and b.
195   _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK static pair<_Size, _Size>
196   __weak_hash_len_32_with_seeds(_Size __w, _Size __x, _Size __y, _Size __z, _Size __a, _Size __b) {
197     __a += __w;
198     __b             = __rotate(__b + __a + __z, 21);
199     const _Size __c = __a;
200     __a += __x;
201     __a += __y;
202     __b += __rotate(__a, 44);
203     return pair<_Size, _Size>(__a + __z, __b + __c);
204   }
205 
206   // Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.
207   _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK static pair<_Size, _Size>
208   __weak_hash_len_32_with_seeds(const char* __s, _Size __a, _Size __b) {
209     return __weak_hash_len_32_with_seeds(
210         std::__loadword<_Size>(__s),
211         std::__loadword<_Size>(__s + 8),
212         std::__loadword<_Size>(__s + 16),
213         std::__loadword<_Size>(__s + 24),
214         __a,
215         __b);
216   }
217 
218   // Return an 8-byte hash for 33 to 64 bytes.
219   _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK static _Size
220   __hash_len_33_to_64(const char* __s, size_t __len) {
221     _Size __z = std::__loadword<_Size>(__s + 24);
222     _Size __a = std::__loadword<_Size>(__s) + (__len + std::__loadword<_Size>(__s + __len - 16)) * __k0;
223     _Size __b = __rotate(__a + __z, 52);
224     _Size __c = __rotate(__a, 37);
225     __a += std::__loadword<_Size>(__s + 8);
226     __c += __rotate(__a, 7);
227     __a += std::__loadword<_Size>(__s + 16);
228     _Size __vf = __a + __z;
229     _Size __vs = __b + __rotate(__a, 31) + __c;
230     __a        = std::__loadword<_Size>(__s + 16) + std::__loadword<_Size>(__s + __len - 32);
231     __z += std::__loadword<_Size>(__s + __len - 8);
232     __b = __rotate(__a + __z, 52);
233     __c = __rotate(__a, 37);
234     __a += std::__loadword<_Size>(__s + __len - 24);
235     __c += __rotate(__a, 7);
236     __a += std::__loadword<_Size>(__s + __len - 16);
237     _Size __wf = __a + __z;
238     _Size __ws = __b + __rotate(__a, 31) + __c;
239     _Size __r  = __shift_mix((__vf + __ws) * __k2 + (__wf + __vs) * __k0);
240     return __shift_mix(__r * __k0 + __vs) * __k2;
241   }
242 };
243 
244 template <class _Tp, size_t = sizeof(_Tp) / sizeof(size_t)>
245 struct __scalar_hash;
246 
247 template <class _Tp>
248 struct __scalar_hash<_Tp, 0> : public __unary_function<_Tp, size_t> {
249   _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
250     union {
251       _Tp __t;
252       size_t __a;
253     } __u;
254     __u.__a = 0;
255     __u.__t = __v;
256     return __u.__a;
257   }
258 };
259 
260 template <class _Tp>
261 struct __scalar_hash<_Tp, 1> : public __unary_function<_Tp, size_t> {
262   _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
263     union {
264       _Tp __t;
265       size_t __a;
266     } __u;
267     __u.__t = __v;
268     return __u.__a;
269   }
270 };
271 
272 template <class _Tp>
273 struct __scalar_hash<_Tp, 2> : public __unary_function<_Tp, size_t> {
274   _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
275     union {
276       _Tp __t;
277       struct {
278         size_t __a;
279         size_t __b;
280       } __s;
281     } __u;
282     __u.__t = __v;
283     return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
284   }
285 };
286 
287 template <class _Tp>
288 struct __scalar_hash<_Tp, 3> : public __unary_function<_Tp, size_t> {
289   _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
290     union {
291       _Tp __t;
292       struct {
293         size_t __a;
294         size_t __b;
295         size_t __c;
296       } __s;
297     } __u;
298     __u.__t = __v;
299     return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
300   }
301 };
302 
303 template <class _Tp>
304 struct __scalar_hash<_Tp, 4> : public __unary_function<_Tp, size_t> {
305   _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
306     union {
307       _Tp __t;
308       struct {
309         size_t __a;
310         size_t __b;
311         size_t __c;
312         size_t __d;
313       } __s;
314     } __u;
315     __u.__t = __v;
316     return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
317   }
318 };
319 
320 struct _PairT {
321   size_t first;
322   size_t second;
323 };
324 
325 _LIBCPP_HIDE_FROM_ABI inline size_t __hash_combine(size_t __lhs, size_t __rhs) _NOEXCEPT {
326   typedef __scalar_hash<_PairT> _HashT;
327   const _PairT __p = {__lhs, __rhs};
328   return _HashT()(__p);
329 }
330 
331 template <class _Tp>
332 struct _LIBCPP_TEMPLATE_VIS hash<_Tp*> : public __unary_function<_Tp*, size_t> {
333   _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp* __v) const _NOEXCEPT {
334     union {
335       _Tp* __t;
336       size_t __a;
337     } __u;
338     __u.__t = __v;
339     return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
340   }
341 };
342 
343 template <>
344 struct _LIBCPP_TEMPLATE_VIS hash<bool> : public __unary_function<bool, size_t> {
345   _LIBCPP_HIDE_FROM_ABI size_t operator()(bool __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
346 };
347 
348 template <>
349 struct _LIBCPP_TEMPLATE_VIS hash<char> : public __unary_function<char, size_t> {
350   _LIBCPP_HIDE_FROM_ABI size_t operator()(char __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
351 };
352 
353 template <>
354 struct _LIBCPP_TEMPLATE_VIS hash<signed char> : public __unary_function<signed char, size_t> {
355   _LIBCPP_HIDE_FROM_ABI size_t operator()(signed char __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
356 };
357 
358 template <>
359 struct _LIBCPP_TEMPLATE_VIS hash<unsigned char> : public __unary_function<unsigned char, size_t> {
360   _LIBCPP_HIDE_FROM_ABI size_t operator()(unsigned char __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
361 };
362 
363 #ifndef _LIBCPP_HAS_NO_CHAR8_T
364 template <>
365 struct _LIBCPP_TEMPLATE_VIS hash<char8_t> : public __unary_function<char8_t, size_t> {
366   _LIBCPP_HIDE_FROM_ABI size_t operator()(char8_t __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
367 };
368 #endif // !_LIBCPP_HAS_NO_CHAR8_T
369 
370 template <>
371 struct _LIBCPP_TEMPLATE_VIS hash<char16_t> : public __unary_function<char16_t, size_t> {
372   _LIBCPP_HIDE_FROM_ABI size_t operator()(char16_t __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
373 };
374 
375 template <>
376 struct _LIBCPP_TEMPLATE_VIS hash<char32_t> : public __unary_function<char32_t, size_t> {
377   _LIBCPP_HIDE_FROM_ABI size_t operator()(char32_t __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
378 };
379 
380 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
381 template <>
382 struct _LIBCPP_TEMPLATE_VIS hash<wchar_t> : public __unary_function<wchar_t, size_t> {
383   _LIBCPP_HIDE_FROM_ABI size_t operator()(wchar_t __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
384 };
385 #endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS
386 
387 template <>
388 struct _LIBCPP_TEMPLATE_VIS hash<short> : public __unary_function<short, size_t> {
389   _LIBCPP_HIDE_FROM_ABI size_t operator()(short __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
390 };
391 
392 template <>
393 struct _LIBCPP_TEMPLATE_VIS hash<unsigned short> : public __unary_function<unsigned short, size_t> {
394   _LIBCPP_HIDE_FROM_ABI size_t operator()(unsigned short __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
395 };
396 
397 template <>
398 struct _LIBCPP_TEMPLATE_VIS hash<int> : public __unary_function<int, size_t> {
399   _LIBCPP_HIDE_FROM_ABI size_t operator()(int __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
400 };
401 
402 template <>
403 struct _LIBCPP_TEMPLATE_VIS hash<unsigned int> : public __unary_function<unsigned int, size_t> {
404   _LIBCPP_HIDE_FROM_ABI size_t operator()(unsigned int __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
405 };
406 
407 template <>
408 struct _LIBCPP_TEMPLATE_VIS hash<long> : public __unary_function<long, size_t> {
409   _LIBCPP_HIDE_FROM_ABI size_t operator()(long __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
410 };
411 
412 template <>
413 struct _LIBCPP_TEMPLATE_VIS hash<unsigned long> : public __unary_function<unsigned long, size_t> {
414   _LIBCPP_HIDE_FROM_ABI size_t operator()(unsigned long __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
415 };
416 
417 template <>
418 struct _LIBCPP_TEMPLATE_VIS hash<long long> : public __scalar_hash<long long> {};
419 
420 template <>
421 struct _LIBCPP_TEMPLATE_VIS hash<unsigned long long> : public __scalar_hash<unsigned long long> {};
422 
423 #ifndef _LIBCPP_HAS_NO_INT128
424 
425 template <>
426 struct _LIBCPP_TEMPLATE_VIS hash<__int128_t> : public __scalar_hash<__int128_t> {};
427 
428 template <>
429 struct _LIBCPP_TEMPLATE_VIS hash<__uint128_t> : public __scalar_hash<__uint128_t> {};
430 
431 #endif
432 
433 template <>
434 struct _LIBCPP_TEMPLATE_VIS hash<float> : public __scalar_hash<float> {
435   _LIBCPP_HIDE_FROM_ABI size_t operator()(float __v) const _NOEXCEPT {
436     // -0.0 and 0.0 should return same hash
437     if (__v == 0.0f)
438       return 0;
439     return __scalar_hash<float>::operator()(__v);
440   }
441 };
442 
443 template <>
444 struct _LIBCPP_TEMPLATE_VIS hash<double> : public __scalar_hash<double> {
445   _LIBCPP_HIDE_FROM_ABI size_t operator()(double __v) const _NOEXCEPT {
446     // -0.0 and 0.0 should return same hash
447     if (__v == 0.0)
448       return 0;
449     return __scalar_hash<double>::operator()(__v);
450   }
451 };
452 
453 template <>
454 struct _LIBCPP_TEMPLATE_VIS hash<long double> : public __scalar_hash<long double> {
455   _LIBCPP_HIDE_FROM_ABI size_t operator()(long double __v) const _NOEXCEPT {
456     // -0.0 and 0.0 should return same hash
457     if (__v == 0.0L)
458       return 0;
459 #if defined(__i386__) || (defined(__x86_64__) && defined(__ILP32__))
460     // Zero out padding bits
461     union {
462       long double __t;
463       struct {
464         size_t __a;
465         size_t __b;
466         size_t __c;
467         size_t __d;
468       } __s;
469     } __u;
470     __u.__s.__a = 0;
471     __u.__s.__b = 0;
472     __u.__s.__c = 0;
473     __u.__s.__d = 0;
474     __u.__t     = __v;
475     return __u.__s.__a ^ __u.__s.__b ^ __u.__s.__c ^ __u.__s.__d;
476 #elif defined(__x86_64__)
477     // Zero out padding bits
478     union {
479       long double __t;
480       struct {
481         size_t __a;
482         size_t __b;
483       } __s;
484     } __u;
485     __u.__s.__a = 0;
486     __u.__s.__b = 0;
487     __u.__t     = __v;
488     return __u.__s.__a ^ __u.__s.__b;
489 #else
490     return __scalar_hash<long double>::operator()(__v);
491 #endif
492   }
493 };
494 
495 template <class _Tp, bool = is_enum<_Tp>::value>
496 struct _LIBCPP_TEMPLATE_VIS __enum_hash : public __unary_function<_Tp, size_t> {
497   _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
498     typedef typename underlying_type<_Tp>::type type;
499     return hash<type>()(static_cast<type>(__v));
500   }
501 };
502 template <class _Tp>
503 struct _LIBCPP_TEMPLATE_VIS __enum_hash<_Tp, false> {
504   __enum_hash()                              = delete;
505   __enum_hash(__enum_hash const&)            = delete;
506   __enum_hash& operator=(__enum_hash const&) = delete;
507 };
508 
509 template <class _Tp>
510 struct _LIBCPP_TEMPLATE_VIS hash : public __enum_hash<_Tp> {};
511 
512 #if _LIBCPP_STD_VER >= 17
513 
514 template <>
515 struct _LIBCPP_TEMPLATE_VIS hash<nullptr_t> : public __unary_function<nullptr_t, size_t> {
516   _LIBCPP_HIDE_FROM_ABI size_t operator()(nullptr_t) const _NOEXCEPT { return 662607004ull; }
517 };
518 #endif
519 
520 #ifndef _LIBCPP_CXX03_LANG
521 template <class _Key, class _Hash>
522 using __check_hash_requirements _LIBCPP_NODEBUG =
523     integral_constant<bool,
524                       is_copy_constructible<_Hash>::value && is_move_constructible<_Hash>::value &&
525                           __invokable_r<size_t, _Hash, _Key const&>::value >;
526 
527 template <class _Key, class _Hash = hash<_Key> >
528 using __has_enabled_hash _LIBCPP_NODEBUG =
529     integral_constant<bool, __check_hash_requirements<_Key, _Hash>::value && is_default_constructible<_Hash>::value >;
530 
531 #  if _LIBCPP_STD_VER >= 17
532 template <class _Type, class>
533 using __enable_hash_helper_imp _LIBCPP_NODEBUG = _Type;
534 
535 template <class _Type, class... _Keys>
536 using __enable_hash_helper _LIBCPP_NODEBUG =
537     __enable_hash_helper_imp<_Type, __enable_if_t<__all<__has_enabled_hash<_Keys>::value...>::value> >;
538 #  else
539 template <class _Type, class...>
540 using __enable_hash_helper _LIBCPP_NODEBUG = _Type;
541 #  endif
542 
543 #endif // !_LIBCPP_CXX03_LANG
544 
545 _LIBCPP_END_NAMESPACE_STD
546 
547 #endif // _LIBCPP___FUNCTIONAL_HASH_H
548