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// TR1 functional -*- C++ -*-
// Copyright (C) 2007 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 2, 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.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING. If not, write to the Free
// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// USA.
// As a special exception, you may use this file as part of a free software
// library without restriction. Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License. This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.
/** @file tr1/functional_hash.h
* This is an internal header file, included by other library headers.
* You should not attempt to use it directly.
*/
#ifndef _TR1_FUNCTIONAL_HASH_H
#define _TR1_FUNCTIONAL_HASH_H 1
#include <string>
#include <cmath> // for std::frexp
namespace std
{
_GLIBCXX_BEGIN_NAMESPACE(tr1)
// Definition of default hash function std::tr1::hash<>. The types for
// which std::tr1::hash<T> is defined is in clause 6.3.3. of the PDTR.
template<typename T>
struct hash;
#define _TR1_hashtable_define_trivial_hash(_Tp) \
template<> \
struct hash<_Tp> \
: public std::unary_function<_Tp, std::size_t> \
{ \
std::size_t \
operator()(_Tp __val) const \
{ return static_cast<std::size_t>(__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
template<typename _Tp>
struct hash<_Tp*>
: public std::unary_function<_Tp*, std::size_t>
{
std::size_t
operator()(_Tp* __p) const
{ return reinterpret_cast<std::size_t>(__p); }
};
// Fowler / Noll / Vo (FNV) Hash (type FNV-1a)
// (used by the next specializations of std::tr1::hash<>)
// Dummy generic implementation (for sizeof(size_t) != 4, 8).
template<std::size_t = sizeof(std::size_t)>
struct _Fnv_hash
{
static std::size_t
hash(const char* __first, std::size_t __length)
{
std::size_t __result = 0;
for (; __length > 0; --__length)
__result = (__result * 131) + *__first++;
return __result;
}
};
template<>
struct _Fnv_hash<4>
{
static std::size_t
hash(const char* __first, std::size_t __length)
{
std::size_t __result = static_cast<std::size_t>(2166136261UL);
for (; __length > 0; --__length)
{
__result ^= static_cast<std::size_t>(*__first++);
__result *= static_cast<std::size_t>(16777619UL);
}
return __result;
}
};
template<>
struct _Fnv_hash<8>
{
static std::size_t
hash(const char* __first, std::size_t __length)
{
std::size_t __result =
static_cast<std::size_t>(14695981039346656037ULL);
for (; __length > 0; --__length)
{
__result ^= static_cast<std::size_t>(*__first++);
__result *= static_cast<std::size_t>(1099511628211ULL);
}
return __result;
}
};
// XXX String and floating point hashes probably shouldn't be inline
// member functions, since are nontrivial. Once we have the framework
// for TR1 .cc files, these should go in one.
template<>
struct hash<std::string>
: public std::unary_function<std::string, std::size_t>
{
std::size_t
operator()(const std::string& __s) const
{ return _Fnv_hash<>::hash(__s.data(), __s.length()); }
};
#ifdef _GLIBCXX_USE_WCHAR_T
template<>
struct hash<std::wstring>
: public std::unary_function<std::wstring, std::size_t>
{
std::size_t
operator()(const std::wstring& __s) const
{
return _Fnv_hash<>::hash(reinterpret_cast<const char*>(__s.data()),
__s.length() * sizeof(wchar_t));
}
};
#endif
template<>
struct hash<float>
: public std::unary_function<float, std::size_t>
{
std::size_t
operator()(float __fval) const
{
std::size_t __result = 0;
// 0 and -0 both hash to zero.
if (__fval != 0.0f)
__result = _Fnv_hash<>::hash(reinterpret_cast<const char*>(&__fval),
sizeof(__fval));
return __result;
}
};
template<>
struct hash<double>
: public std::unary_function<double, std::size_t>
{
std::size_t
operator()(double __dval) const
{
std::size_t __result = 0;
// 0 and -0 both hash to zero.
if (__dval != 0.0)
__result = _Fnv_hash<>::hash(reinterpret_cast<const char*>(&__dval),
sizeof(__dval));
return __result;
}
};
// For long double, careful with random padding bits (e.g., on x86,
// 10 bytes -> 12 bytes) and resort to frexp.
template<>
struct hash<long double>
: public std::unary_function<long double, std::size_t>
{
std::size_t
operator()(long double __ldval) const
{
std::size_t __result = 0;
int __exponent;
__ldval = std::frexp(__ldval, &__exponent);
__ldval = __ldval < 0.0l ? -(__ldval + 0.5l) : __ldval;
const long double __mult =
std::numeric_limits<std::size_t>::max() + 1.0l;
__ldval *= __mult;
// Try to use all the bits of the mantissa (really necessary only
// on 32-bit targets, at least for 80-bit floating point formats).
const std::size_t __hibits = (std::size_t)__ldval;
__ldval = (__ldval - (long double)__hibits) * __mult;
const std::size_t __coeff =
(std::numeric_limits<std::size_t>::max()
/ std::numeric_limits<long double>::max_exponent);
__result = __hibits + (std::size_t)__ldval + __coeff * __exponent;
return __result;
}
};
_GLIBCXX_END_NAMESPACE
}
#endif
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