Update.
[glibc.git] / sysdeps / libm-ieee754 / s_logb.c
blob4668cf78f8810340baa67f0327bec002c2c125ff
1 /* @(#)s_logb.c 5.1 93/09/24 */
2 /*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
13 #if defined(LIBM_SCCS) && !defined(lint)
14 static char rcsid[] = "$NetBSD: s_logb.c,v 1.8 1995/05/10 20:47:50 jtc Exp $";
15 #endif
18 * double logb(x)
19 * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
20 * Use ilogb instead.
23 #include "math.h"
24 #include "math_private.h"
26 #ifdef __STDC__
27 double __logb(double x)
28 #else
29 double __logb(x)
30 double x;
31 #endif
33 int32_t lx,ix;
34 EXTRACT_WORDS(ix,lx,x);
35 ix &= 0x7fffffff; /* high |x| */
36 if((ix|lx)==0) return -1.0/fabs(x);
37 if(ix>=0x7ff00000) return x*x;
38 if((ix>>=20)==0) /* IEEE 754 logb */
39 return -1022.0;
40 else
41 return (double) (ix-1023);
43 weak_alias (__logb, logb)
44 #ifdef NO_LONG_DOUBLE
45 strong_alias (__logb, __logbl)
46 weak_alias (__logb, logbl)
47 #endif