lib/libm/src/w_log2f.c

   1 /* w_log10f.c -- float version of w_log10.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: w_log2f.c,v 1.1 2005/07/21 16:58:39 christos Exp $");
  19 #endif
  20
  21 /*
  22  * wrapper log2f(X)
  23  */
  24
  25 #include "math.h"
  26 #include "math_private.h"
  27
  28
  29 float
  30 log2f(float x)          /* wrapper log2f */
  31 {
  32 #ifdef _IEEE_LIBM
  33         return __ieee754_log2f(x);
  34 #else
  35         float z;
  36         z = __ieee754_log2f(x);
  37         if(_LIB_VERSION == _IEEE_ || isnanf(x)) return z;
  38         if(x<=(float)0.0) {
  39             if(x==(float)0.0)
  40                 /* log2(0) */
  41                 return (float)__kernel_standard((double)x,(double)x,148);
  42             else
  43                 /* log2(x<0) */
  44                 return (float)__kernel_standard((double)x,(double)x,149);
  45         } else
  46             return z;
  47 #endif
  48 }