| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| */ |
| |
| /* ilogb(double x) |
| * return the binary exponent of non-zero x |
| * ilogb(0) = FP_ILOGB0 |
| * ilogb(NaN) = FP_ILOGBNAN (no signal is raised) |
| * ilogb(inf) = INT_MAX (no signal is raised) |
| */ |
| |
| #include <limits.h> |
| |
| #include "math.h" |
| #include "math_private.h" |
| |
| int ilogb(double x) |
| { |
| int32_t hx,lx,ix; |
| |
| EXTRACT_WORDS(hx,lx,x); |
| hx &= 0x7fffffff; |
| if(hx<0x00100000) { |
| if((hx|lx)==0) |
| return FP_ILOGB0; |
| else /* subnormal x */ |
| if(hx==0) { |
| for (ix = -1043; lx>0; lx<<=1) ix -=1; |
| } else { |
| for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1; |
| } |
| return ix; |
| } |
| else if (hx<0x7ff00000) return (hx>>20)-1023; |
| else if (hx>0x7ff00000 || lx!=0) return FP_ILOGBNAN; |
| else return INT_MAX; |
| } |