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
  16 #include <sys/cdefs.h>
  17 #if defined(LIBM_SCCS) && !defined(lint)
  18 __RCSID("$NetBSD: s_logbf.c,v 1.7 2002/05/26 22:01:57 wiz Exp $");
  19 #endif
  20
  21 #include "math.h"
  22 #include "math_private.h"
  23
  24 float
  25 logbf(float x)
  26 {
  27         int32_t ix;
  28         GET_FLOAT_WORD(ix,x);
  29         ix &= 0x7fffffff;                       /* high |x| */
  30         if(ix==0) return (float)-1.0/fabsf(x);
  31         if(ix>=0x7f800000) return x*x;
  32         if((ix>>=23)==0)                        /* IEEE 754 logb */
  33                 return -126.0;
  34         else
  35                 return (float) (ix-127);
  36 }