sysdeps/ieee754/ldbl-96/s_scalbnl.c

   1 /* s_scalbnl.c -- long double version of s_scalbn.c.
   2  * Conversion to long double by Ulrich Drepper,
   3  * Cygnus Support, drepper@cygnus.com.
   4  */
   5
   6 /*
   7  * ====================================================
   8  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   9  *
  10  * Developed at SunPro, a Sun Microsystems, Inc. business.
  11  * Permission to use, copy, modify, and distribute this
  12  * software is freely granted, provided that this notice
  13  * is preserved.
  14  * ====================================================
  15  */
  16
  17 #if defined(LIBM_SCCS) && !defined(lint)
  18 static char rcsid[] = "$NetBSD: $";
  19 #endif
  20
  21 /*
  22  * scalbnl (long double x, int n)
  23  * scalbnl(x,n) returns x* 2**n  computed by  exponent
  24  * manipulation rather than by actually performing an
  25  * exponentiation or a multiplication.
  26  */
  27
  28 #include "math.h"
  29 #include "math_private.h"
  30
  31 #ifdef __STDC__
  32 static const long double
  33 #else
  34 static long double
  35 #endif
  36 two64   =  1.8446744073709551616e19L,
  37 twom64  =  5.421010862427522170037e-20L,
  38 huge   = 1.0e+4900L,
  39 tiny   = 1.0e-4900L;
  40
  41 #ifdef __STDC__
  42         long double __scalbnl (long double x, int n)
  43 #else
  44         long double __scalbnl (x,n)
  45         long double x; int n;
  46 #endif
  47 {
  48         int32_t k,es,hx,lx;
  49         GET_LDOUBLE_WORDS(es,hx,lx,x);
  50         k = es&0x7fff;                          /* extract exponent */
  51         if (k==0) {                             /* 0 or subnormal x */
  52             if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
  53             x *= two64;
  54             GET_LDOUBLE_EXP(hx,x);
  55             k = (hx&0x7fff) - 64;
  56             }
  57         if (k==0x7fff) return x+x;              /* NaN or Inf */
  58         k = k+n;
  59         if (n> 50000 || k > 0x7ffe)
  60           return huge*__copysignl(huge,x); /* overflow  */
  61         if (n< -50000)
  62           return tiny*__copysignl(tiny,x);
  63         if (k > 0)                              /* normal result */
  64             {SET_LDOUBLE_EXP(x,(es&0x8000)|k); return x;}
  65         if (k <= -64)
  66             return tiny*__copysignl(tiny,x);    /*underflow*/
  67         k += 64;                                /* subnormal result */
  68         SET_LDOUBLE_EXP(x,(es&0x8000)|k);
  69         return x*twom64;
  70 }
  71 weak_alias (__scalbnl, scalbnl)