The Android Open Source Project | b07e1d9 | 2009-03-03 19:29:30 -0800 | [diff] [blame] | 1 | |
| 2 | /* @(#)s_ilogb.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 | /* ieee_ilogb(double x) |
| 15 | * return the binary exponent of non-zero x |
| 16 | * ieee_ilogb(0) = 0x80000001 |
| 17 | * ieee_ilogb(inf/NaN) = 0x7fffffff (no signal is raised) |
| 18 | */ |
| 19 | |
| 20 | #include "fdlibm.h" |
| 21 | |
| 22 | #ifdef __STDC__ |
| 23 | int ieee_ilogb(double x) |
| 24 | #else |
| 25 | int ieee_ilogb(x) |
| 26 | double x; |
| 27 | #endif |
| 28 | { |
| 29 | int hx,lx,ix; |
| 30 | |
| 31 | hx = (__HI(x))&0x7fffffff; /* high word of x */ |
| 32 | if(hx<0x00100000) { |
| 33 | lx = __LO(x); |
| 34 | if((hx|lx)==0) |
| 35 | return 0x80000001; /* ieee_ilogb(0) = 0x80000001 */ |
| 36 | else /* subnormal x */ |
| 37 | if(hx==0) { |
| 38 | for (ix = -1043; lx>0; lx<<=1) ix -=1; |
| 39 | } else { |
| 40 | for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1; |
| 41 | } |
| 42 | return ix; |
| 43 | } |
| 44 | else if (hx<0x7ff00000) return (hx>>20)-1023; |
| 45 | else return 0x7fffffff; |
| 46 | } |