RTAI API: base/math/s_logb.c Source File

00001 #if !defined(__ppc__) 00002 /* @(#)s_logb.c 5.1 93/09/24 */ 00003 /* 00004 * ==================================================== 00005 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 00006 * 00007 * Developed at SunPro, a Sun Microsystems, Inc. business. 00008 * Permission to use, copy, modify, and distribute this 00009 * software is freely granted, provided that this notice 00010 * is preserved. 00011 * ==================================================== 00012 */ 00013 00014 #if defined(LIBM_SCCS) && !defined(lint) 00015 static char rcsid[] = "$NetBSD: s_logb.c,v 1.8 1995/05/10 20:47:50 jtc Exp $"; 00016 #endif 00017 00018 /* 00019 * double logb(x) 00020 * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. 00021 * Use ilogb instead. 00022 */ 00023 00024 #include "math.h" 00025 #include "mathP.h" 00026 00027 #ifdef __STDC__ 00028 double logb(double x) 00029 #else 00030 double logb(x) 00031 double x; 00032 #endif 00033 { 00034 int32_t lx,ix; 00035 EXTRACT_WORDS(ix,lx,x); 00036 ix &= 0x7fffffff; /* high |x| */ 00037 if((ix|lx)==0) return -1.0/fabs(x); 00038 if(ix>=0x7ff00000) return x*x; 00039 if((ix>>=20)==0) /* IEEE 754 logb */ 00040 return -1022.0; 00041 else 00042 return (double) (ix-1023); 00043 } 00044 #endif /* !__ppc__ */