sysdeps/ieee754/ldbl-96/s_logbl.c

   1 /* s_logbl.c -- long double version of s_logb.c.
   2  * Conversion to long double by Ulrich Drepper,
   3  * Cygnus Support, drepper@cygnus.com.
   4  */
   5
   6 /*
   7  * ====================================================
   8  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   9  *
  10  * Developed at SunPro, a Sun Microsystems, Inc. business.
  11  * Permission to use, copy, modify, and distribute this
  12  * software is freely granted, provided that this notice
  13  * is preserved.
  14  * ====================================================
  15  */
  16
  17 #if defined(LIBM_SCCS) && !defined(lint)
  18 static char rcsid[] = "$NetBSD: $";
  19 #endif
  20
  21 /*
  22  * long double logbl(x)
  23  * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
  24  * Use ilogb instead.
  25  */
  26
  27 #include "math.h"
  28 #include "math_private.h"
  29
  30 #ifdef __STDC__
  31         long double __logbl(long double x)
  32 #else
  33         long double __logbl(x)
  34         long double x;
  35 #endif
  36 {
  37         int32_t es,lx,ix;
  38         GET_LDOUBLE_WORDS(es,ix,lx,x);
  39         es &= 0x7fff;                           /* exponent */
  40         if((es|ix|lx)==0) return -1.0/fabs(x);
  41         if(es==0x7fff) return x*x;
  42         if(es==0)                       /* IEEE 754 logb */
  43                 return -16382.0;
  44         else
  45                 return (long double) (es-0x3fff);
  46 }
  47 weak_alias (__logbl, logbl)