libjava/java/lang/e_remainder.c

   1
   2 /* @(#)e_remainder.c 5.1 93/09/24 */
   3 /*
   4  * ====================================================
   5  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   6  *
   7  * Developed at SunPro, a Sun Microsystems, Inc. business.
   8  * Permission to use, copy, modify, and distribute this
   9  * software is freely granted, provided that this notice
  10  * is preserved.
  11  * ====================================================
  12  */
  13
  14 /* __ieee754_remainder(x,p)
  15  * Return :
  16  *      returns  x REM p  =  x - [x/p]*p as if in infinite
  17  *      precise arithmetic, where [x/p] is the (infinite bit)
  18  *      integer nearest x/p (in half way case choose the even one).
  19  * Method :
  20  *      Based on fmod() return x-[x/p]chopped*p exactlp.
  21  */
  22
  23 #include "fdlibm.h"
  24
  25 #ifndef _DOUBLE_IS_32BITS
  26
  27 #ifdef __STDC__
  28 static const double zero = 0.0;
  29 #else
  30 static double zero = 0.0;
  31 #endif
  32
  33
  34 #ifdef __STDC__
  35         double __ieee754_remainder(double x, double p)
  36 #else
  37         double __ieee754_remainder(x,p)
  38         double x,p;
  39 #endif
  40 {
  41         int32_t hx,hp;
  42         uint32_t sx,lx,lp;
  43         double p_half;
  44
  45         EXTRACT_WORDS(hx,lx,x);
  46         EXTRACT_WORDS(hp,lp,p);
  47         sx = hx&0x80000000;
  48         hp &= 0x7fffffff;
  49         hx &= 0x7fffffff;
  50
  51     /* purge off exception values */
  52         if((hp|lp)==0) return (x*p)/(x*p);      /* p = 0 */
  53         if((hx>=0x7ff00000)||                   /* x not finite */
  54           ((hp>=0x7ff00000)&&                   /* p is NaN */
  55           (((hp-0x7ff00000)|lp)!=0)))
  56             return (x*p)/(x*p);
  57
  58
  59         if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p);  /* now x < 2p */
  60         if (((hx-hp)|(lx-lp))==0) return zero*x;
  61         x  = fabs(x);
  62         p  = fabs(p);
  63         if (hp<0x00200000) {
  64             if(x+x>p) {
  65                 x-=p;
  66                 if(x+x>=p) x -= p;
  67             }
  68         } else {
  69             p_half = 0.5*p;
  70             if(x>p_half) {
  71                 x-=p;
  72                 if(x>=p_half) x -= p;
  73             }
  74         }
  75         GET_HIGH_WORD(hx,x);
  76         SET_HIGH_WORD(x,hx^sx);
  77         return x;
  78 }
  79
  80 #endif /* defined(_DOUBLE_IS_32BITS) */