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/>.
25 // For long double, careful with random padding bits (e.g., on x86,
26 // 10 bytes -> 12 bytes) and resort to frexp.
29 hash
<long double>::operator()(long double __val
) const
34 __val
= std::frexp(__val
, &__exponent
);
35 __val
= __val
< 0.0l ? -(__val
+ 0.5l) : __val
;
37 const long double __mult
=
38 __gnu_cxx::__numeric_traits
<size_t>::__max
+ 1.0l;
41 // Try to use all the bits of the mantissa (really necessary only
42 // on 32-bit targets, at least for 80-bit floating point formats).
43 const size_t __hibits
= (size_t)__val
;
44 __val
= (__val
- (long double)__hibits
) * __mult
;
46 const size_t __coeff
=
47 __gnu_cxx::__numeric_traits
<size_t>::__max
/ __LDBL_MAX_EXP__
;
49 __result
= __hibits
+ (size_t)__val
+ __coeff
* __exponent
;
54 #ifndef _GLIBCXX_LONG_DOUBLE_COMPAT_IMPL
57 hash
<string
>::operator()(string __s
) const
58 { return _Fnv_hash
<>::hash(__s
.data(), __s
.length()); }
62 hash
<const string
&>::operator()(const string
& __s
) const
63 { return _Fnv_hash
<>::hash(__s
.data(), __s
.length()); }
65 #ifdef _GLIBCXX_USE_WCHAR_T
68 hash
<wstring
>::operator()(wstring __s
) const
70 const char* __p
= reinterpret_cast<const char*>(__s
.data());
71 return _Fnv_hash
<>::hash(__p
, __s
.length() * sizeof(wchar_t));
76 hash
<const wstring
&>::operator()(const wstring
& __s
) const
78 const char* __p
= reinterpret_cast<const char*>(__s
.data());
79 return _Fnv_hash
<>::hash(__p
, __s
.length() * sizeof(wchar_t));