201 lines
5.9 KiB
C++
201 lines
5.9 KiB
C++
// TR1 functional_hash.h header -*- C++ -*-
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// Copyright (C) 2007-2021 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 tr1/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{tr1/functional}
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*/
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#ifndef _GLIBCXX_TR1_FUNCTIONAL_HASH_H
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#define _GLIBCXX_TR1_FUNCTIONAL_HASH_H 1
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#pragma GCC system_header
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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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namespace tr1
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{
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/// Class template hash.
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// Declaration of default hash functor std::tr1::hash. The types for
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// which std::tr1::hash<T> is well-defined is in clause 6.3.3. of the PDTR.
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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 _TR1_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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_TR1_hashtable_define_trivial_hash(bool);
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_TR1_hashtable_define_trivial_hash(char);
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_TR1_hashtable_define_trivial_hash(signed char);
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_TR1_hashtable_define_trivial_hash(unsigned char);
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_TR1_hashtable_define_trivial_hash(wchar_t);
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_TR1_hashtable_define_trivial_hash(short);
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_TR1_hashtable_define_trivial_hash(int);
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_TR1_hashtable_define_trivial_hash(long);
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_TR1_hashtable_define_trivial_hash(long long);
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_TR1_hashtable_define_trivial_hash(unsigned short);
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_TR1_hashtable_define_trivial_hash(unsigned int);
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_TR1_hashtable_define_trivial_hash(unsigned long);
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_TR1_hashtable_define_trivial_hash(unsigned long long);
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#undef _TR1_hashtable_define_trivial_hash
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// Fowler / Noll / Vo (FNV) Hash (type FNV-1a)
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// (Used by the next specializations of std::tr1::hash.)
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// N.B. These functions should work on unsigned char, otherwise they do not
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// correctly implement the FNV-1a algorithm (see PR59406).
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// The existing behaviour is retained for backwards compatibility.
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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)
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{
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size_t __result = 0;
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const char* __cptr = reinterpret_cast<const char*>(__ptr);
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for (; __clength; --__clength)
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__result = (__result * 131) + *__cptr++;
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return __result;
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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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{
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size_t __result = static_cast<size_t>(2166136261UL);
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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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__result ^= static_cast<size_t>(*__cptr++);
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__result *= static_cast<size_t>(16777619UL);
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}
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return __result;
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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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{
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size_t __result
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= static_cast<size_t>(14695981039346656037ULL);
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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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__result ^= static_cast<size_t>(*__cptr++);
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__result *= static_cast<size_t>(1099511628211ULL);
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}
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return __result;
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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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};
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/// Explicit specializations 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::tr1::_Fnv_hash::hash(__val) : 0;
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}
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/// Explicit specializations 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::tr1::_Fnv_hash::hash(__val) : 0;
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}
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/// Explicit specializations 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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/// Explicit specialization of member operator for non-builtin types.
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template<>
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_GLIBCXX_PURE size_t
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hash<string>::operator()(string) const;
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template<>
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_GLIBCXX_PURE size_t
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hash<const string&>::operator()(const string&) const;
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#ifdef _GLIBCXX_USE_WCHAR_T
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template<>
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_GLIBCXX_PURE size_t
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hash<wstring>::operator()(wstring) const;
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template<>
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_GLIBCXX_PURE size_t
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hash<const wstring&>::operator()(const wstring&) const;
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#endif
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}
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_GLIBCXX_END_NAMESPACE_VERSION
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}
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#endif // _GLIBCXX_TR1_FUNCTIONAL_HASH_H
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