sysdeps/libm-ieee754/s_scalbnf.c

   1 /* s_scalbnf.c -- float version of s_scalbn.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 #if defined(LIBM_SCCS) && !defined(lint)
  17 static char rcsid[] = "$NetBSD: s_scalbnf.c,v 1.4 1995/05/10 20:48:10 jtc Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 #ifdef __STDC__
  24 static const float
  25 #else
  26 static float
  27 #endif
  28 two25   =  3.355443200e+07,     /* 0x4c000000 */
  29 twom25  =  2.9802322388e-08,    /* 0x33000000 */
  30 huge   = 1.0e+30,
  31 tiny   = 1.0e-30;
  32
  33 #ifdef __STDC__
  34         float __scalbnf (float x, int n)
  35 #else
  36         float __scalbnf (x,n)
  37         float x; int n;
  38 #endif
  39 {
  40         int32_t k,ix;
  41         GET_FLOAT_WORD(ix,x);
  42         k = (ix&0x7f800000)>>23;                /* extract exponent */
  43         if (k==0) {                             /* 0 or subnormal x */
  44             if ((ix&0x7fffffff)==0) return x; /* +-0 */
  45             x *= two25;
  46             GET_FLOAT_WORD(ix,x);
  47             k = ((ix&0x7f800000)>>23) - 25;
  48             }
  49         if (k==0xff) return x+x;                /* NaN or Inf */
  50         k = k+n;
  51         if (n> 50000 || k >  0xfe)
  52           return huge*copysignf(huge,x); /* overflow  */
  53         if (n< -50000)
  54           return tiny*copysignf(tiny,x);        /*underflow*/
  55         if (k > 0)                              /* normal result */
  56             {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
  57         if (k <= -25)
  58             return tiny*copysignf(tiny,x);      /*underflow*/
  59         k += 25;                                /* subnormal result */
  60         SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
  61         return x*twom25;
  62 }
  63 weak_alias (__scalbnf, scalbnf)