| The Android Open Source Project | b07e1d9 | 2009-03-03 19:29:30 -0800 | [diff] [blame] | 1 | |
| 2 | /* @(#)s_logb.c 1.3 95/01/18 */ |
| 3 | /* |
| 4 | * ==================================================== |
| 5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| 6 | * |
| 7 | * Developed at SunSoft, a Sun Microsystems, Inc. business. |
| 8 | * Permission to use, copy, modify, and distribute this |
| 9 | * software is freely granted, provided that this notice |
| 10 | * is preserved. |
| 11 | * ==================================================== |
| 12 | */ |
| 13 | |
| 14 | /* |
| 15 | * double ieee_logb(x) |
| 16 | * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. |
| 17 | * Use ilogb instead. |
| 18 | */ |
| 19 | |
| 20 | #include "fdlibm.h" |
| 21 | |
| 22 | #ifdef __STDC__ |
| 23 | double ieee_logb(double x) |
| 24 | #else |
| 25 | double ieee_logb(x) |
| 26 | double x; |
| 27 | #endif |
| 28 | { |
| 29 | int lx,ix; |
| 30 | ix = (__HI(x))&0x7fffffff; /* high |x| */ |
| 31 | lx = __LO(x); /* low x */ |
| 32 | if((ix|lx)==0) return -1.0/ieee_fabs(x); |
| 33 | if(ix>=0x7ff00000) return x*x; |
| 34 | if((ix>>=20)==0) /* IEEE 754 logb */ |
| 35 | return -1022.0; |
| 36 | else |
| 37 | return (double) (ix-1023); |
| 38 | } |