sysdeps/libm-ieee754/s_remquol.c

   1 /* Compute remainder and a congruent to the quotient.
   2    Copyright (C) 1997 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include <math.h>
  22
  23 #include "math_private.h"
  24
  25
  26 static const long double zero = 0.0;
  27
  28
  29 long double
  30 __remquol (long double x, long double p, int *quo)
  31 {
  32   int32_t ex,ep,hx,hp;
  33   u_int32_t sx,lx,lp;
  34   int cquo,qs;
  35
  36   GET_LDOUBLE_WORDS (ex, hx, lx, x);
  37   GET_LDOUBLE_WORDS (ep, hp, lp, p);
  38   sx = ex & 0x8000;
  39   qs = (sx ^ (ep & 0x8000)) >> 15;
  40   ep &= 0x7fff;
  41   ex &= 0x7fff;
  42
  43   /* Purge off exception values.  */
  44   if ((ep | hp | lp) == 0)
  45     return (x * p) / (x * p);                   /* p = 0 */
  46   if ((ex == 0x7fff)                            /* x not finite */
  47       || ((ep == 0x7fff)                        /* p is NaN */
  48           && ((hp | lp) != 0)))
  49     return (x * p) / (x * p);
  50
  51   if (ep <= 0x7ffb)
  52     x = __ieee754_fmodl (x, 8 * p);             /* now x < 8p */
  53
  54   if (((ex - ep) | (hx - hp) | (lx - lp)) == 0)
  55     {
  56       *quo = qs ? -1 : 1;
  57       return zero * x;
  58     }
  59
  60   x  = fabsl (x);
  61   p  = fabsl (p);
  62   cquo = 0;
  63
  64   if (x >= 4 * p)
  65     {
  66       x -= 4 * p;
  67       cquo += 4;
  68     }
  69   if (x >= 2 * p)
  70     {
  71       x -= 2 * p;
  72       cquo += 2;
  73     }
  74
  75   if (ep < 0x0002)
  76     {
  77       if (x + x > p)
  78         {
  79           x -= p;
  80           ++cquo;
  81           if (x + x >= p)
  82             {
  83               x -= p;
  84               ++cquo;
  85             }
  86         }
  87     }
  88   else
  89     {
  90       long double p_half = 0.5 * p;
  91       if (x > p_half)
  92         {
  93           x -= p;
  94           ++cquo;
  95           if (x >= p_half)
  96             {
  97               x -= p;
  98               ++cquo;
  99             }
 100         }
 101     }
 102
 103   *quo = qs ? -cquo : cquo;
 104
 105   if (sx)
 106     x = -x;
 107   return x;
 108 }
 109 weak_alias (__remquol, remquol)