| /* @(#)s_ilogb.c 5.1 93/09/24 */ |
| /* |
| * ==================================================== |
| * 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. |
| * ==================================================== |
| */ |
| |
| #if defined(LIBM_SCCS) && !defined(lint) |
| static char rcsid[] = "$NetBSD: s_ilogb.c,v 1.9 1995/05/10 20:47:28 jtc Exp $"; |
| #endif |
| |
| /* 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" |
| |
| #ifdef __STDC__ |
| int __ilogb(double x) |
| #else |
| int __ilogb(x) |
| double x; |
| #endif |
| { |
| int32_t hx,lx,ix; |
| |
| GET_HIGH_WORD(hx,x); |
| hx &= 0x7fffffff; |
| if(hx<0x00100000) { |
| GET_LOW_WORD(lx,x); |
| if((hx|lx)==0) |
| return FP_ILOGB0; /* ilogb(0) = 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 (FP_ILOGBNAN != INT_MAX) { |
| /* ISO C99 requires ilogb(+-Inf) == INT_MAX. */ |
| GET_LOW_WORD(lx,x); |
| if(((hx^0x7ff00000)|lx) == 0) |
| return INT_MAX; |
| } |
| return FP_ILOGBNAN; |
| } |
| weak_alias (__ilogb, ilogb) |
| #ifdef NO_LONG_DOUBLE |
| strong_alias (__ilogb, __ilogbl) |
| weak_alias (__ilogb, ilogbl) |
| #endif |
