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 14 static char rcsid[] = "$FreeBSD$"; 15 #endif 16 17 #include <float.h> 18 #include <limits.h> 19 #include <math.h> 20 21 #include "fpmath.h" 22 23 long double logbl(long double x)24logbl(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) { /* x == 0 */ 33 u.bits.sign = 1; 34 return (1.0L / u.e); 35 } 36 /* denormalized */ 37 if (u.bits.manh == 0) { 38 m = 1lu << (LDBL_MANL_SIZE - 1); 39 for (b = LDBL_MANH_SIZE; !(u.bits.manl & m); m >>= 1) 40 b++; 41 } else { 42 m = 1lu << (LDBL_MANH_SIZE - 1); 43 for (b = 0; !(u.bits.manh & m); m >>= 1) 44 b++; 45 } 46 #ifdef LDBL_IMPLICIT_NBIT 47 b++; 48 #endif 49 return ((long double)(LDBL_MIN_EXP - b - 1)); 50 } 51 if (u.bits.exp < (LDBL_MAX_EXP << 1) - 1) /* normal */ 52 return ((long double)(u.bits.exp - LDBL_MAX_EXP + 1)); 53 else /* +/- inf or nan */ 54 return (x * x); 55 } 56