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  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) */
  81.