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 long double 21 logbl(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) { /* x == 0 */ 30 u.bits.sign = 1; 31 return (1.0L / u.e); 32 } 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 ((long double)(LDBL_MIN_EXP - b - 1)); 47 } 48 if (u.bits.exp < (LDBL_MAX_EXP << 1) - 1) /* normal */ 49 return ((long double)(u.bits.exp - LDBL_MAX_EXP + 1)); 50 else /* +/- inf or nan */ 51 return (x * x); 52 } 53