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Editing: functional_hash.h
// functional_hash.h header -*- C++ -*- // Copyright (C) 2007-2018 Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 3, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see // <http://www.gnu.org/licenses/>. /** @file bits/functional_hash.h * This is an internal header file, included by other library headers. * Do not attempt to use it directly. @headername{functional} */ #ifndef _FUNCTIONAL_HASH_H #define _FUNCTIONAL_HASH_H 1 #pragma GCC system_header #include <bits/hash_bytes.h> namespace std _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION /** @defgroup hashes Hashes * @ingroup functors * * Hashing functors taking a variable type and returning a @c std::size_t. * * @{ */ template<typename _Result, typename _Arg> struct __hash_base { typedef _Result result_type _GLIBCXX17_DEPRECATED; typedef _Arg argument_type _GLIBCXX17_DEPRECATED; }; /// Primary class template hash. template<typename _Tp> struct hash; template<typename _Tp, typename = void> struct __poison_hash { static constexpr bool __enable_hash_call = false; private: // Private rather than deleted to be non-trivially-copyable. __poison_hash(__poison_hash&&); ~__poison_hash(); }; template<typename _Tp> struct __poison_hash<_Tp, __void_t<decltype(hash<_Tp>()(declval<_Tp>()))>> { static constexpr bool __enable_hash_call = true; }; // Helper struct for SFINAE-poisoning non-enum types. template<typename _Tp, bool = is_enum<_Tp>::value> struct __hash_enum { private: // Private rather than deleted to be non-trivially-copyable. __hash_enum(__hash_enum&&); ~__hash_enum(); }; // Helper struct for hash with enum types. template<typename _Tp> struct __hash_enum<_Tp, true> : public __hash_base<size_t, _Tp> { size_t operator()(_Tp __val) const noexcept { using __type = typename underlying_type<_Tp>::type; return hash<__type>{}(static_cast<__type>(__val)); } }; /// Primary class template hash, usable for enum types only. // Use with non-enum types still SFINAES. template<typename _Tp> struct hash : __hash_enum<_Tp> { }; /// Partial specializations for pointer types. template<typename _Tp> struct hash<_Tp*> : public __hash_base<size_t, _Tp*> { size_t operator()(_Tp* __p) const noexcept { return reinterpret_cast<size_t>(__p); } }; // Explicit specializations for integer types. #define _Cxx_hashtable_define_trivial_hash(_Tp) \ template<> \ struct hash<_Tp> : public __hash_base<size_t, _Tp> \ { \ size_t \ operator()(_Tp __val) const noexcept \ { return static_cast<size_t>(__val); } \ }; /// Explicit specialization for bool. _Cxx_hashtable_define_trivial_hash(bool) /// Explicit specialization for char. _Cxx_hashtable_define_trivial_hash(char) /// Explicit specialization for signed char. _Cxx_hashtable_define_trivial_hash(signed char) /// Explicit specialization for unsigned char. _Cxx_hashtable_define_trivial_hash(unsigned char) /// Explicit specialization for wchar_t. _Cxx_hashtable_define_trivial_hash(wchar_t) /// Explicit specialization for char16_t. _Cxx_hashtable_define_trivial_hash(char16_t) /// Explicit specialization for char32_t. _Cxx_hashtable_define_trivial_hash(char32_t) /// Explicit specialization for short. _Cxx_hashtable_define_trivial_hash(short) /// Explicit specialization for int. _Cxx_hashtable_define_trivial_hash(int) /// Explicit specialization for long. _Cxx_hashtable_define_trivial_hash(long) /// Explicit specialization for long long. _Cxx_hashtable_define_trivial_hash(long long) /// Explicit specialization for unsigned short. _Cxx_hashtable_define_trivial_hash(unsigned short) /// Explicit specialization for unsigned int. _Cxx_hashtable_define_trivial_hash(unsigned int) /// Explicit specialization for unsigned long. _Cxx_hashtable_define_trivial_hash(unsigned long) /// Explicit specialization for unsigned long long. _Cxx_hashtable_define_trivial_hash(unsigned long long) #ifdef __GLIBCXX_TYPE_INT_N_0 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_0) _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_0 unsigned) #endif #ifdef __GLIBCXX_TYPE_INT_N_1 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_1) _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_1 unsigned) #endif #ifdef __GLIBCXX_TYPE_INT_N_2 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_2) _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_2 unsigned) #endif #ifdef __GLIBCXX_TYPE_INT_N_3 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_3) _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_3 unsigned) #endif #undef _Cxx_hashtable_define_trivial_hash struct _Hash_impl { static size_t hash(const void* __ptr, size_t __clength, size_t __seed = static_cast<size_t>(0xc70f6907UL)) { return _Hash_bytes(__ptr, __clength, __seed); } template<typename _Tp> static size_t hash(const _Tp& __val) { return hash(&__val, sizeof(__val)); } template<typename _Tp> static size_t __hash_combine(const _Tp& __val, size_t __hash) { return hash(&__val, sizeof(__val), __hash); } }; // A hash function similar to FNV-1a (see PR59406 for how it differs). struct _Fnv_hash_impl { static size_t hash(const void* __ptr, size_t __clength, size_t __seed = static_cast<size_t>(2166136261UL)) { return _Fnv_hash_bytes(__ptr, __clength, __seed); } template<typename _Tp> static size_t hash(const _Tp& __val) { return hash(&__val, sizeof(__val)); } template<typename _Tp> static size_t __hash_combine(const _Tp& __val, size_t __hash) { return hash(&__val, sizeof(__val), __hash); } }; /// Specialization for float. template<> struct hash<float> : public __hash_base<size_t, float> { size_t operator()(float __val) const noexcept { // 0 and -0 both hash to zero. return __val != 0.0f ? std::_Hash_impl::hash(__val) : 0; } }; /// Specialization for double. template<> struct hash<double> : public __hash_base<size_t, double> { size_t operator()(double __val) const noexcept { // 0 and -0 both hash to zero. return __val != 0.0 ? std::_Hash_impl::hash(__val) : 0; } }; /// Specialization for long double. template<> struct hash<long double> : public __hash_base<size_t, long double> { _GLIBCXX_PURE size_t operator()(long double __val) const noexcept; }; // @} group hashes // Hint about performance of hash functor. If not fast the hash-based // containers will cache the hash code. // Default behavior is to consider that hashers are fast unless specified // otherwise. template<typename _Hash> struct __is_fast_hash : public std::true_type { }; template<> struct __is_fast_hash<hash<long double>> : public std::false_type { }; _GLIBCXX_END_NAMESPACE_VERSION } // namespace #endif // _FUNCTIONAL_HASH_H
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