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 <sys/cdefs.h> 14 __FBSDID("$FreeBSD$"); 15 16 #include <float.h> 17 #include <limits.h> 18 #include <math.h> 19 20 #include "fpmath.h" 21 22 int 23 ilogbl(long double x) 24 { 25 union IEEEl2bits u; 26 unsigned long m; 27 int b; 28 29 u.e = x; 30 if (u.bits.exp == 0) { 31 if ((u.bits.manl | u.bits.manh) == 0) 32 return (FP_ILOGB0); 33 /* denormalized */ 34 if (u.bits.manh == 0) { 35 m = 1lu << (LDBL_MANL_SIZE - 1); 36 for (b = LDBL_MANH_SIZE; !(u.bits.manl & m); m >>= 1) 37 b++; 38 } else { 39 m = 1lu << (LDBL_MANH_SIZE - 1); 40 for (b = 0; !(u.bits.manh & m); m >>= 1) 41 b++; 42 } 43 #ifdef LDBL_IMPLICIT_NBIT 44 b++; 45 #endif 46 return (LDBL_MIN_EXP - b - 1); 47 } else if (u.bits.exp < (LDBL_MAX_EXP << 1) - 1) 48 return (u.bits.exp - LDBL_MAX_EXP + 1); 49 else if (u.bits.manl != 0 || u.bits.manh != 0) 50 return (FP_ILOGBNAN); 51 else 52 return (INT_MAX); 53 } 54