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
  16 #include <sys/cdefs.h>
  17 #if defined(LIBM_SCCS) && !defined(lint)
  18 __RCSID("$NetBSD: s_scalbnf.c,v 1.9 2010/04/23 19:17:07 drochner Exp $");
  19 #endif
  20
  21 #include "namespace.h"
  22 #include "math.h"
  23 #include "math_private.h"
  24
  25 #ifdef __weak_alias
  26 __weak_alias(scalbnf, _scalbnf)
  27 #endif
  28
  29 static const float
  30 two25   =  3.355443200e+07,     /* 0x4c000000 */
  31 twom25  =  2.9802322388e-08,    /* 0x33000000 */
  32 huge   = 1.0e+30,
  33 tiny   = 1.0e-30;
  34
  35 float
  36 scalbnf(float x, int n)
  37 {
  38         int32_t k,ix;
  39         GET_FLOAT_WORD(ix,x);
  40         k = (ix&0x7f800000)>>23;                /* extract exponent */
  41         if (k==0) {                             /* 0 or subnormal x */
  42             if ((ix&0x7fffffff)==0) return x; /* +-0 */
  43             x *= two25;
  44             GET_FLOAT_WORD(ix,x);
  45             k = ((ix&0x7f800000)>>23) - 25;
  46             if (n< -50000) return tiny*x;       /*underflow*/
  47             }
  48         if (k==0xff) return x+x;                /* NaN or Inf */
  49         k = k+n;
  50         if (k >  0xfe) return huge*copysignf(huge,x); /* overflow  */
  51         if (k > 0)                              /* normal result */
  52             {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
  53         if (k <= -25) {
  54             if (n > 50000)      /* in case integer overflow in n+k */
  55                 return huge*copysignf(huge,x);  /*overflow*/
  56             else return tiny*copysignf(tiny,x); /*underflow*/
  57         }
  58         k += 25;                                /* subnormal result */
  59         SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
  60         return x*twom25;
  61 }