// functional_hash.h header -*- C++ -*-
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// Copyright (C) 2007, 2008, 2009, 2010 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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* You should not attempt to use it directly.
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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 <cstddef>
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#include <bits/stl_function.h>
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namespace std
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{
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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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/// Primary class template hash.
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template<typename _Tp>
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struct hash : public std::unary_function<_Tp, size_t>
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{
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size_t
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operator()(_Tp __val) const;
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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 std::unary_function<_Tp*, size_t>
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{
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size_t
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operator()(_Tp* __p) const
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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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inline size_t \
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hash<_Tp>::operator()(_Tp __val) const \
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{ return static_cast<size_t>(__val); }
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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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#undef _Cxx_hashtable_define_trivial_hash
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// Fowler / Noll / Vo (FNV) Hash (type FNV-1a)
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// Dummy generic implementation (for sizeof(size_t) != 4, 8).
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template<size_t>
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struct _Fnv_hash_base
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{
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template<typename _Tp>
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static size_t
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hash(const _Tp* __ptr, size_t __clength, size_t __hash = 0)
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{
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const char* __cptr = reinterpret_cast<const char*>(__ptr);
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for (; __clength; --__clength)
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__hash = (__hash * 131) + *__cptr++;
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return __hash;
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}
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};
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template<>
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struct _Fnv_hash_base<4>
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{
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template<typename _Tp>
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static size_t
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hash(const _Tp* __ptr, size_t __clength,
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size_t __hash = static_cast<size_t>(2166136261UL))
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{
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const char* __cptr = reinterpret_cast<const char*>(__ptr);
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for (; __clength; --__clength)
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{
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__hash ^= static_cast<size_t>(*__cptr++);
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__hash *= static_cast<size_t>(16777619UL);
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}
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return __hash;
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}
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};
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template<>
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struct _Fnv_hash_base<8>
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{
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template<typename _Tp>
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static size_t
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hash(const _Tp* __ptr, size_t __clength,
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size_t __hash = static_cast<size_t>(14695981039346656037ULL))
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{
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const char* __cptr = reinterpret_cast<const char*>(__ptr);
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for (; __clength; --__clength)
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{
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__hash ^= static_cast<size_t>(*__cptr++);
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__hash *= static_cast<size_t>(1099511628211ULL);
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}
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return __hash;
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}
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};
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struct _Fnv_hash
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: public _Fnv_hash_base<sizeof(size_t)>
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{
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using _Fnv_hash_base<sizeof(size_t)>::hash;
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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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inline size_t
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hash<float>::operator()(float __val) const
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{
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// 0 and -0 both hash to zero.
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return __val != 0.0f ? std::_Fnv_hash::hash(__val) : 0;
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}
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/// Specialization for double.
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template<>
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inline size_t
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hash<double>::operator()(double __val) const
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{
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// 0 and -0 both hash to zero.
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return __val != 0.0 ? std::_Fnv_hash::hash(__val) : 0;
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}
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/// Specialization for long double.
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template<>
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_GLIBCXX_PURE size_t
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hash<long double>::operator()(long double __val) const;
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// @} group hashes
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}
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#endif // _FUNCTIONAL_HASH_H
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