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 #include "cdefs-compat.h" 14 //__FBSDID("$FreeBSD: src/lib/msun/src/s_ilogbl.c,v 1.2 2008/02/22 02:30:35 das Exp $"); 15 16 #include <float.h> 17 #include <limits.h> 18 #include <openlibm_math.h> 19 20 #include "fpmath.h" 21 #include "math_private.h" 22 23 DLLEXPORT int 24 ilogbl(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