lib/libm/src/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  * $NetBSD: s_scalbnf.c,v 1.8 2002/05/26 22:01:58 wiz Exp $
  16  * $DragonFly: src/lib/libm/src/s_scalbnf.c,v 1.1 2005/07/26 21:15:20 joerg Exp $
  17  */
  18
  19 #include <math.h>
  20 #include "math_private.h"
  21
  22 static const float
  23 two25   =  3.355443200e+07,     /* 0x4c000000 */
  24 twom25  =  2.9802322388e-08,    /* 0x33000000 */
  25 huge   = 1.0e+30,
  26 tiny   = 1.0e-30;
  27
  28 float
  29 scalbnf(float x, int n)
  30 {
  31         int32_t k,ix;
  32         GET_FLOAT_WORD(ix,x);
  33         k = (ix&0x7f800000)>>23;                /* extract exponent */
  34         if (k==0) {                             /* 0 or subnormal x */
  35             if ((ix&0x7fffffff)==0) return x; /* +-0 */
  36             x *= two25;
  37             GET_FLOAT_WORD(ix,x);
  38             k = ((ix&0x7f800000)>>23) - 25;
  39             if (n< -50000) return tiny*x;       /*underflow*/
  40             }
  41         if (k==0xff) return x+x;                /* NaN or Inf */
  42         k = k+n;
  43         if (k >  0xfe) return huge*copysignf(huge,x); /* overflow  */
  44         if (k > 0)                              /* normal result */
  45             {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
  46         if (k <= -25) {
  47             if (n > 50000)      /* in case integer overflow in n+k */
  48                 return huge*copysignf(huge,x);  /*overflow*/
  49             else return tiny*copysignf(tiny,x); /*underflow*/
  50         }
  51         k += 25;                                /* subnormal result */
  52         SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
  53         return x*twom25;
  54 }