1 // std::hash and std::tr1::hash definitions -*- C++ -*-
3 // Copyright (C) 2007, 2008, 2009 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
29 #ifdef __GXX_EXPERIMENTAL_CXX0X__
31 # define _GLIBCXX_BEGIN_NAMESPACE_TR1
32 # define _GLIBCXX_END_NAMESPACE_TR1
34 #include <tr1/functional>
35 # define _GLIBCXX_BEGIN_NAMESPACE_TR1 namespace tr1 {
36 # define _GLIBCXX_END_NAMESPACE_TR1 }
41 _GLIBCXX_BEGIN_NAMESPACE_TR1
43 // For long double, careful with random padding bits (e.g., on x86,
44 // 10 bytes -> 12 bytes) and resort to frexp.
47 hash<long double>::operator()(long double __val) const throw ()
52 __val = std::frexp(__val, &__exponent);
53 __val = __val < 0.0l ? -(__val + 0.5l) : __val;
55 const long double __mult =
56 __gnu_cxx::__numeric_traits<size_t>::__max + 1.0l;
59 // Try to use all the bits of the mantissa (really necessary only
60 // on 32-bit targets, at least for 80-bit floating point formats).
61 const size_t __hibits = (size_t)__val;
62 __val = (__val - (long double)__hibits) * __mult;
64 const size_t __coeff =
65 __gnu_cxx::__numeric_traits<size_t>::__max / __LDBL_MAX_EXP__;
67 __result = __hibits + (size_t)__val + __coeff * __exponent;
72 #ifndef _GLIBCXX_LONG_DOUBLE_COMPAT_IMPL
75 hash<string>::operator()(string __s) const throw ()
76 { return _Fnv_hash<>::hash(__s.data(), __s.length()); }
80 hash<const string&>::operator()(const string& __s) const throw ()
81 { return _Fnv_hash<>::hash(__s.data(), __s.length()); }
83 #ifdef _GLIBCXX_USE_WCHAR_T
86 hash<wstring>::operator()(wstring __s) const throw ()
88 const char* __p = reinterpret_cast<const char*>(__s.data());
89 return _Fnv_hash<>::hash(__p, __s.length() * sizeof(wchar_t));
94 hash<const wstring&>::operator()(const wstring& __s) const throw ()
96 const char* __p = reinterpret_cast<const char*>(__s.data());
97 return _Fnv_hash<>::hash(__p, __s.length() * sizeof(wchar_t));
102 _GLIBCXX_END_NAMESPACE_TR1