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 long double 23 logbl(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) { /* x == 0 */ 32 u.bits.sign = 1; 33 return (1.0L / u.e); 34 } 35 /* denormalized */ 36 if (u.bits.manh == 0) { 37 m = 1lu << (LDBL_MANL_SIZE - 1); 38 for (b = LDBL_MANH_SIZE; !(u.bits.manl & m); m >>= 1) 39 b++; 40 } else { 41 m = 1lu << (LDBL_MANH_SIZE - 1); 42 for (b = 0; !(u.bits.manh & m); m >>= 1) 43 b++; 44 } 45 #ifdef LDBL_IMPLICIT_NBIT 46 b++; 47 #endif 48 return ((long double)(LDBL_MIN_EXP - b - 1)); 49 } 50 if (u.bits.exp < (LDBL_MAX_EXP << 1) - 1) /* normal */ 51 return ((long double)(u.bits.exp - LDBL_MAX_EXP + 1)); 52 else /* +/- inf or nan */ 53 return (x * x); 54 } 55