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glibc  2.9
s_trunc.c
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00001 /* Truncate argument to nearest integral value not larger than the argument.
00002    Copyright (C) 1997, 1998 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
00005 
00006    The GNU C Library is free software; you can redistribute it and/or
00007    modify it under the terms of the GNU Lesser General Public
00008    License as published by the Free Software Foundation; either
00009    version 2.1 of the License, or (at your option) any later version.
00010 
00011    The GNU C Library is distributed in the hope that it will be useful,
00012    but WITHOUT ANY WARRANTY; without even the implied warranty of
00013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014    Lesser General Public License for more details.
00015 
00016    You should have received a copy of the GNU Lesser General Public
00017    License along with the GNU C Library; if not, write to the Free
00018    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00019    02111-1307 USA.  */
00020 
00021 #include <math.h>
00022 
00023 #include "math_private.h"
00024 
00025 
00026 double
00027 __trunc (double x)
00028 {
00029   int32_t i0, j0;
00030   u_int32_t i1;
00031   int sx;
00032 
00033   EXTRACT_WORDS (i0, i1, x);
00034   sx = i0 & 0x80000000;
00035   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
00036   if (j0 < 20)
00037     {
00038       if (j0 < 0)
00039        /* The magnitude of the number is < 1 so the result is +-0.  */
00040        INSERT_WORDS (x, sx, 0);
00041       else
00042        INSERT_WORDS (x, sx | (i0 & ~(0x000fffff >> j0)), 0);
00043     }
00044   else if (j0 > 51)
00045     {
00046       if (j0 == 0x400)
00047        /* x is inf or NaN.  */
00048        return x + x;
00049     }
00050   else
00051     {
00052       INSERT_WORDS (x, i0, i1 & ~(0xffffffffu >> (j0 - 20)));
00053     }
00054 
00055   return x;
00056 }
00057 weak_alias (__trunc, trunc)
00058 #ifdef NO_LONG_DOUBLE
00059 strong_alias (__trunc, __truncl)
00060 weak_alias (__trunc, truncl)
00061 #endif