mirror of git://gcc.gnu.org/git/gcc.git
59 lines
2.0 KiB
C++
59 lines
2.0 KiB
C++
// std::hash definitions -*- C++ -*-
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// Copyright (C) 2010 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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#ifndef __GXX_EXPERIMENTAL_CXX0X__
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# error "hash_c++0x.cc must be compiled with -std=gnu++0x"
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#endif
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#include <bits/functional_hash.h>
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namespace std
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{
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/// std::hash specialization for long double.
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template<>
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size_t
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hash<long double>::operator()(long double __val) const
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{
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size_t __result = 0;
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int __exponent;
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__val = __builtin_frexpl(__val, &__exponent);
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__val = __val < 0.0l ? -(__val + 0.5l) : __val;
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const long double __mult = __SIZE_MAX__ + 1.0l;
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__val *= __mult;
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// Try to use all the bits of the mantissa (really necessary only
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// on 32-bit targets, at least for 80-bit floating point formats).
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const size_t __hibits = (size_t)__val;
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__val = (__val - (long double)__hibits) * __mult;
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const size_t __coeff = __SIZE_MAX__ / __LDBL_MAX_EXP__;
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__result = __hibits + (size_t)__val + __coeff * __exponent;
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return __result;
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}
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}
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