lib/libm/src/s_logbf.c

   1 /* s_logbf.c -- float version of s_logb.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_logbf.c,v 1.7 2002/05/26 22:01:57 wiz Exp $
  16  * $DragonFly: src/lib/libm/src/s_logbf.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 float
  23 logbf(float x)
  24 {
  25         int32_t ix;
  26         GET_FLOAT_WORD(ix,x);
  27         ix &= 0x7fffffff;                       /* high |x| */
  28         if(ix==0) return (float)-1.0/fabsf(x);
  29         if(ix>=0x7f800000) return x*x;
  30         if((ix>>=23)==0)                        /* IEEE 754 logb */
  31                 return -126.0;
  32         else
  33                 return (float) (ix-127);
  34 }