0,0 → 1,57 |
// std::hash definitions -*- C++ -*- |
|
// Copyright (C) 2010-2015 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 |
// <http://www.gnu.org/licenses/>. |
|
#if __cplusplus < 201103L |
# error "hash_c++0x.cc must be compiled with -std=gnu++0x" |
#endif |
|
#include <type_traits> |
#include <bits/functional_hash.h> |
|
namespace std _GLIBCXX_VISIBILITY(default) |
{ |
_GLIBCXX_PURE size_t |
hash<long double>::operator()(long double __val) const noexcept |
{ |
// 0 and -0 both hash to zero. |
if (__val == 0.0L) |
return 0; |
|
int __exponent; |
__val = __builtin_frexpl(__val, &__exponent); |
__val = __val < 0.0l ? -(__val + 0.5l) : __val; |
|
const long double __mult = __SIZE_MAX__ + 1.0l; |
__val *= __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 size_t __hibits = (size_t)__val; |
__val = (__val - (long double)__hibits) * __mult; |
|
const size_t __coeff = __SIZE_MAX__ / __LDBL_MAX_EXP__; |
|
return __hibits + (size_t)__val + __coeff * __exponent; |
} |
} |