1/* 2 * From: @(#)s_ilogb.c 5.1 93/09/24 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 14static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_ilogbl.c,v 1.1 2004/10/11 18:13:52 stefanf Exp $"; 15#endif 16 17#include <float.h> 18#include <limits.h> 19#include <math.h> 20 21#include "fpmath.h" 22 23int 24ilogbl(long double x) 25{ 26 union IEEEl2bits u; 27 unsigned long m; 28 int b; 29 30 u.e = x; 31 if (u.bits.exp == 0) { 32 if ((u.bits.manl | u.bits.manh) == 0) 33 return (FP_ILOGB0); 34 /* denormalized */ 35 if (u.bits.manh == 0) { 36 m = 1lu << (LDBL_MANL_SIZE - 1); 37 for (b = LDBL_MANH_SIZE; !(u.bits.manl & m); m >>= 1) 38 b++; 39 } else { 40 m = 1lu << (LDBL_MANH_SIZE - 1); 41 for (b = 0; !(u.bits.manh & m); m >>= 1) 42 b++; 43 } 44#ifdef LDBL_IMPLICIT_NBIT 45 b++; 46#endif 47 return (LDBL_MIN_EXP - b - 1); 48 } else if (u.bits.exp < (LDBL_MAX_EXP << 1) - 1) 49 return (u.bits.exp - LDBL_MAX_EXP + 1); 50 else if (u.bits.manl != 0 || u.bits.manh != 0) 51 return (FP_ILOGBNAN); 52 else 53 return (INT_MAX); 54} 55