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