1174698Sdas/* 2174698Sdas * From: @(#)s_ilogb.c 5.1 93/09/24 3174698Sdas * ==================================================== 4174698Sdas * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 5174698Sdas * 6174698Sdas * Developed at SunPro, a Sun Microsystems, Inc. business. 7174698Sdas * Permission to use, copy, modify, and distribute this 8174698Sdas * software is freely granted, provided that this notice 9174698Sdas * is preserved. 10174698Sdas * ==================================================== 11174698Sdas */ 12174698Sdas 13174698Sdas#ifndef lint 14174698Sdasstatic char rcsid[] = "$FreeBSD$"; 15174698Sdas#endif 16174698Sdas 17174698Sdas#include <float.h> 18174698Sdas#include <limits.h> 19174698Sdas#include <math.h> 20174698Sdas 21174698Sdas#include "fpmath.h" 22174698Sdas 23174698Sdaslong double 24174698Sdaslogbl(long double x) 25174698Sdas{ 26174698Sdas union IEEEl2bits u; 27174698Sdas unsigned long m; 28174698Sdas int b; 29174698Sdas 30174698Sdas u.e = x; 31174698Sdas if (u.bits.exp == 0) { 32174698Sdas if ((u.bits.manl | u.bits.manh) == 0) { /* x == 0 */ 33174698Sdas u.bits.sign = 1; 34174698Sdas return (1.0L / u.e); 35174698Sdas } 36174698Sdas /* denormalized */ 37174698Sdas if (u.bits.manh == 0) { 38174698Sdas m = 1lu << (LDBL_MANL_SIZE - 1); 39174698Sdas for (b = LDBL_MANH_SIZE; !(u.bits.manl & m); m >>= 1) 40174698Sdas b++; 41174698Sdas } else { 42174698Sdas m = 1lu << (LDBL_MANH_SIZE - 1); 43174698Sdas for (b = 0; !(u.bits.manh & m); m >>= 1) 44174698Sdas b++; 45174698Sdas } 46174698Sdas#ifdef LDBL_IMPLICIT_NBIT 47174698Sdas b++; 48174698Sdas#endif 49174698Sdas return ((long double)(LDBL_MIN_EXP - b - 1)); 50174698Sdas } 51174698Sdas if (u.bits.exp < (LDBL_MAX_EXP << 1) - 1) /* normal */ 52174698Sdas return ((long double)(u.bits.exp - LDBL_MAX_EXP + 1)); 53174698Sdas else /* +/- inf or nan */ 54174698Sdas return (x * x); 55174698Sdas} 56