sysdeps/libm-ieee754/s_frexp.c

   1 /* @(#)s_frexp.c 5.1 93/09/24 */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12
  13 #if defined(LIBM_SCCS) && !defined(lint)
  14 static char rcsid[] = "$NetBSD: s_frexp.c,v 1.9 1995/05/10 20:47:24 jtc Exp $";
  15 #endif
  16
  17 /*
  18  * for non-zero x
  19  *      x = frexp(arg,&exp);
  20  * return a double fp quantity x such that 0.5 <= |x| <1.0
  21  * and the corresponding binary exponent "exp". That is
  22  *      arg = x*2^exp.
  23  * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
  24  * with *exp=0.
  25  */
  26
  27 #include "math.h"
  28 #include "math_private.h"
  29
  30 #ifdef __STDC__
  31 static const double
  32 #else
  33 static double
  34 #endif
  35 two54 =  1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
  36
  37 #ifdef __STDC__
  38         double __frexp(double x, int *eptr)
  39 #else
  40         double __frexp(x, eptr)
  41         double x; int *eptr;
  42 #endif
  43 {
  44         int32_t hx, ix, lx;
  45         EXTRACT_WORDS(hx,lx,x);
  46         ix = 0x7fffffff&hx;
  47         *eptr = 0;
  48         if(ix>=0x7ff00000||((ix|lx)==0)) return x;      /* 0,inf,nan */
  49         if (ix<0x00100000) {            /* subnormal */
  50             x *= two54;
  51             GET_HIGH_WORD(hx,x);
  52             ix = hx&0x7fffffff;
  53             *eptr = -54;
  54         }
  55         *eptr += (ix>>20)-1022;
  56         hx = (hx&0x800fffff)|0x3fe00000;
  57         SET_HIGH_WORD(x,hx);
  58         return x;
  59 }
  60 weak_alias (__frexp, frexp)
  61 #ifdef NO_LONG_DOUBLE
  62 strong_alias (__frexp, __frexpl)
  63 weak_alias (__frexp, frexpl)
  64 #endif