projects / uclibc-ng.git / blame
| Commit | Line | Data |
|---|---|---|
| 7ce331c0 EA |
1 | /* @(#)s_logb.c 5.1 93/09/24 */ |
| 2 | /* | |
| 3 | * ==================================================== | |
| 4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. | |
| 5 | * | |
| 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 | * ==================================================== | |
| 11 | */ | |
| 12 | ||
| 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 | |
| 16 | ||
| 17 | /* | |
| 18 | * double logb(x) | |
| 19 | * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. | |
| 20 | * Use ilogb instead. | |
| 21 | */ | |
| 22 | ||
| 23 | #include "math.h" | |
| 24 | #include "math_private.h" | |
| 25 | ||
| 26 | #ifdef __STDC__ | |
| 27 | double logb(double x) | |
| 28 | #else | |
| 29 | double logb(x) | |
| 30 | double x; | |
| 31 | #endif | |
| 32 | { | |
| 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); | |
| 42 | } |