Edit: /usr/include/c++/8/tr1/functional_hash.h (6043B)
// TR1 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
//
.
/** @file tr1/functional_hash.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{tr1/functional}
*/
#ifndef _GLIBCXX_TR1_FUNCTIONAL_HASH_H
#define _GLIBCXX_TR1_FUNCTIONAL_HASH_H 1
#pragma GCC system_header
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace tr1
{
/// Class template hash.
// Declaration of default hash functor std::tr1::hash. The types for
// which std::tr1::hash
is well-defined is in clause 6.3.3. of the PDTR.
template
struct hash : public std::unary_function<_Tp, size_t>
{
size_t
operator()(_Tp __val) const;
};
/// Partial specializations for pointer types.
template
struct hash<_Tp*> : public std::unary_function<_Tp*, size_t>
{
size_t
operator()(_Tp* __p) const
{ return reinterpret_cast(__p); }
};
/// Explicit specializations for integer types.
#define _TR1_hashtable_define_trivial_hash(_Tp) \
template<> \
inline size_t \
hash<_Tp>::operator()(_Tp __val) const \
{ return static_cast(__val); }
_TR1_hashtable_define_trivial_hash(bool);
_TR1_hashtable_define_trivial_hash(char);
_TR1_hashtable_define_trivial_hash(signed char);
_TR1_hashtable_define_trivial_hash(unsigned char);
_TR1_hashtable_define_trivial_hash(wchar_t);
_TR1_hashtable_define_trivial_hash(short);
_TR1_hashtable_define_trivial_hash(int);
_TR1_hashtable_define_trivial_hash(long);
_TR1_hashtable_define_trivial_hash(long long);
_TR1_hashtable_define_trivial_hash(unsigned short);
_TR1_hashtable_define_trivial_hash(unsigned int);
_TR1_hashtable_define_trivial_hash(unsigned long);
_TR1_hashtable_define_trivial_hash(unsigned long long);
#undef _TR1_hashtable_define_trivial_hash
// Fowler / Noll / Vo (FNV) Hash (type FNV-1a)
// (Used by the next specializations of std::tr1::hash.)
// N.B. These functions should work on unsigned char, otherwise they do not
// correctly implement the FNV-1a algorithm (see PR59406).
// The existing behaviour is retained for backwards compatibility.
/// Dummy generic implementation (for sizeof(size_t) != 4, 8).
template
struct _Fnv_hash_base
{
template
static size_t
hash(const _Tp* __ptr, size_t __clength)
{
size_t __result = 0;
const char* __cptr = reinterpret_cast(__ptr);
for (; __clength; --__clength)
__result = (__result * 131) + *__cptr++;
return __result;
}
};
template<>
struct _Fnv_hash_base<4>
{
template
static size_t
hash(const _Tp* __ptr, size_t __clength)
{
size_t __result = static_cast(2166136261UL);
const char* __cptr = reinterpret_cast(__ptr);
for (; __clength; --__clength)
{
__result ^= static_cast(*__cptr++);
__result *= static_cast(16777619UL);
}
return __result;
}
};
template<>
struct _Fnv_hash_base<8>
{
template
static size_t
hash(const _Tp* __ptr, size_t __clength)
{
size_t __result
= static_cast(14695981039346656037ULL);
const char* __cptr = reinterpret_cast(__ptr);
for (; __clength; --__clength)
{
__result ^= static_cast(*__cptr++);
__result *= static_cast(1099511628211ULL);
}
return __result;
}
};
struct _Fnv_hash
: public _Fnv_hash_base
{
using _Fnv_hash_base::hash;
template
static size_t
hash(const _Tp& __val)
{ return hash(&__val, sizeof(__val)); }
};
/// Explicit specializations for float.
template<>
inline size_t
hash::operator()(float __val) const
{
// 0 and -0 both hash to zero.
return __val != 0.0f ? std::tr1::_Fnv_hash::hash(__val) : 0;
}
/// Explicit specializations for double.
template<>
inline size_t
hash::operator()(double __val) const
{
// 0 and -0 both hash to zero.
return __val != 0.0 ? std::tr1::_Fnv_hash::hash(__val) : 0;
}
/// Explicit specializations for long double.
template<>
_GLIBCXX_PURE size_t
hash::operator()(long double __val) const;
/// Explicit specialization of member operator for non-builtin types.
template<>
_GLIBCXX_PURE size_t
hash::operator()(string) const;
template<>
_GLIBCXX_PURE size_t
hash::operator()(const string&) const;
#ifdef _GLIBCXX_USE_WCHAR_T
template<>
_GLIBCXX_PURE size_t
hash::operator()(wstring) const;
template<>
_GLIBCXX_PURE size_t
hash::operator()(const wstring&) const;
#endif
}
_GLIBCXX_END_NAMESPACE_VERSION
}
#endif // _GLIBCXX_TR1_FUNCTIONAL_HASH_H