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