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glibc  2.9
s_isinfl.c
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00001 /* Copyright (C) 1991, 1992, 1995, 1997, 2002 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003 
00004    The GNU C Library is free software; you can redistribute it and/or
00005    modify it under the terms of the GNU Lesser General Public
00006    License as published by the Free Software Foundation; either
00007    version 2.1 of the License, or (at your option) any later version.
00008 
00009    The GNU C Library is distributed in the hope that it will be useful,
00010    but WITHOUT ANY WARRANTY; without even the implied warranty of
00011    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012    Lesser General Public License for more details.
00013 
00014    You should have received a copy of the GNU Lesser General Public
00015    License along with the GNU C Library; if not, write to the Free
00016    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00017    02111-1307 USA.  */
00018 
00019 #include <math.h>
00020 #include "ieee754.h"
00021 
00022 /* Return 0 if VALUE is finite or NaN, +1 if it
00023    is +Infinity, -1 if it is -Infinity.  */
00024 int
00025 __isinfl (long double value)
00026 {
00027   union ieee854_long_double u;
00028 
00029   u.d = value;
00030 
00031   /* An IEEE 854 infinity has an exponent with the
00032      maximum possible value and a zero mantissa.
00033      In Motorola's interpretation the integer bit is ignored.  */
00034   if ((u.ieee.exponent & 0x7fff) == 0x7fff &&
00035       (u.ieee.mantissa0 & 0x7fffffff) == 0 && u.ieee.mantissa1 == 0)
00036     return u.ieee.negative ? -1 : 1;
00037 
00038   return 0;
00039 }
00040 
00041 hidden_def (__isinfl)
00042 weak_alias (__isinfl, isinfl);