1*38fd1498Szrj // std::tr1::hash definitions, long double bits -*- C++ -*- 2*38fd1498Szrj 3*38fd1498Szrj // Copyright (C) 2010-2018 Free Software Foundation, Inc. 4*38fd1498Szrj // 5*38fd1498Szrj // This file is part of the GNU ISO C++ Library. This library is free 6*38fd1498Szrj // software; you can redistribute it and/or modify it under the 7*38fd1498Szrj // terms of the GNU General Public License as published by the 8*38fd1498Szrj // Free Software Foundation; either version 3, or (at your option) 9*38fd1498Szrj // any later version. 10*38fd1498Szrj 11*38fd1498Szrj // This library is distributed in the hope that it will be useful, 12*38fd1498Szrj // but WITHOUT ANY WARRANTY; without even the implied warranty of 13*38fd1498Szrj // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14*38fd1498Szrj // GNU General Public License for more details. 15*38fd1498Szrj 16*38fd1498Szrj // Under Section 7 of GPL version 3, you are granted additional 17*38fd1498Szrj // permissions described in the GCC Runtime Library Exception, version 18*38fd1498Szrj // 3.1, as published by the Free Software Foundation. 19*38fd1498Szrj 20*38fd1498Szrj // You should have received a copy of the GNU General Public License and 21*38fd1498Szrj // a copy of the GCC Runtime Library Exception along with this program; 22*38fd1498Szrj // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23*38fd1498Szrj // <http://www.gnu.org/licenses/>. 24*38fd1498Szrj 25*38fd1498Szrj #pragma GCC diagnostic ignored "-Wattribute-alias" 26*38fd1498Szrj 27*38fd1498Szrj namespace std _GLIBCXX_VISIBILITY(default) 28*38fd1498Szrj { 29*38fd1498Szrj namespace tr1 30*38fd1498Szrj { 31*38fd1498Szrj // For long double, careful with random padding bits (e.g., on x86, 32*38fd1498Szrj // 10 bytes -> 12 bytes) and resort to frexp. 33*38fd1498Szrj template<> 34*38fd1498Szrj size_t operator ()(long double __val) const35*38fd1498Szrj hash<long double>::operator()(long double __val) const 36*38fd1498Szrj { 37*38fd1498Szrj // 0 and -0 both hash to zero. 38*38fd1498Szrj if (__val == 0.0L) 39*38fd1498Szrj return 0; 40*38fd1498Szrj 41*38fd1498Szrj int __exponent; 42*38fd1498Szrj __val = __builtin_frexpl(__val, &__exponent); 43*38fd1498Szrj __val = __val < 0.0l ? -(__val + 0.5l) : __val; 44*38fd1498Szrj 45*38fd1498Szrj const long double __mult = __SIZE_MAX__ + 1.0l; 46*38fd1498Szrj __val *= __mult; 47*38fd1498Szrj 48*38fd1498Szrj // Try to use all the bits of the mantissa (really necessary only 49*38fd1498Szrj // on 32-bit targets, at least for 80-bit floating point formats). 50*38fd1498Szrj const size_t __hibits = (size_t)__val; 51*38fd1498Szrj __val = (__val - (long double)__hibits) * __mult; 52*38fd1498Szrj 53*38fd1498Szrj const size_t __coeff = __SIZE_MAX__ / __LDBL_MAX_EXP__; 54*38fd1498Szrj 55*38fd1498Szrj return __hibits + (size_t)__val + __coeff * __exponent; 56*38fd1498Szrj } 57*38fd1498Szrj } 58*38fd1498Szrj } 59