| The Android Open Source Project | a27d2ba | 2008-10-21 07:00:00 -0700 | [diff] [blame^] | 1 | /* @(#)s_ilogb.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 | #ifndef lint |
| 14 | static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_ilogb.c,v 1.9 2004/10/09 17:14:28 stefanf Exp $"; |
| 15 | #endif |
| 16 | |
| 17 | /* ilogb(double x) |
| 18 | * return the binary exponent of non-zero x |
| 19 | * ilogb(0) = FP_ILOGB0 |
| 20 | * ilogb(NaN) = FP_ILOGBNAN (no signal is raised) |
| 21 | * ilogb(inf) = INT_MAX (no signal is raised) |
| 22 | */ |
| 23 | |
| 24 | #include <limits.h> |
| 25 | |
| 26 | #include "math.h" |
| 27 | #include "math_private.h" |
| 28 | |
| 29 | int ilogb(double x) |
| 30 | { |
| 31 | int32_t hx,lx,ix; |
| 32 | |
| 33 | EXTRACT_WORDS(hx,lx,x); |
| 34 | hx &= 0x7fffffff; |
| 35 | if(hx<0x00100000) { |
| 36 | if((hx|lx)==0) |
| 37 | return FP_ILOGB0; |
| 38 | else /* subnormal x */ |
| 39 | if(hx==0) { |
| 40 | for (ix = -1043; lx>0; lx<<=1) ix -=1; |
| 41 | } else { |
| 42 | for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1; |
| 43 | } |
| 44 | return ix; |
| 45 | } |
| 46 | else if (hx<0x7ff00000) return (hx>>20)-1023; |
| 47 | else if (hx>0x7ff00000 || lx!=0) return FP_ILOGBNAN; |
| 48 | else return INT_MAX; |
| 49 | } |