lib/libm/src/s_ilogbf.c

   1 /* s_ilogbf.c -- float version of s_ilogb.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_ilogbf.c,v 1.7 2002/05/26 22:01:56 wiz Exp $
  16  * $DragonFly: src/lib/libm/src/s_ilogbf.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 int
  23 ilogbf(float x)
  24 {
  25         int32_t hx,ix;
  26
  27         GET_FLOAT_WORD(hx,x);
  28         hx &= 0x7fffffff;
  29         if(hx<0x00800000) {
  30             if(hx==0)
  31                 return 0x80000001;      /* ilogb(0) = 0x80000001 */
  32             else                        /* subnormal x */
  33                 for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1;
  34             return ix;
  35         }
  36         else if (hx<0x7f800000) return (hx>>23)-127;
  37         else return 0x7fffffff;
  38 }