1 /* $OpenBSD: frexp.c,v 1.2 2005/08/08 08:05:34 espie Exp $ */ 2 3 /*- 4 * Copyright (c) 2004 David Schultz <das@FreeBSD.ORG> 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 * 28 * $FreeBSD: frexp.c,v 1.1 2004/07/18 21:23:39 das Exp $ 29 */ 30 31 #include <sys/types.h> 32 #include <machine/ieee.h> 33 #include <math.h> 34 35 double 36 frexp(double v, int *ex) 37 { 38 union { 39 double v; 40 struct ieee_double s; 41 } u; 42 43 u.v = v; 44 switch (u.s.dbl_exp) { 45 case 0: /* 0 or subnormal */ 46 if ((u.s.dbl_fracl | u.s.dbl_frach) == 0) { 47 *ex = 0; 48 } else { 49 /* 50 * The power of 2 is arbitrary, any value from 54 to 51 * 1024 will do. 52 */ 53 u.v *= 0x1.0p514; 54 *ex = u.s.dbl_exp - (DBL_EXP_BIAS - 1 + 514); 55 u.s.dbl_exp = DBL_EXP_BIAS - 1; 56 } 57 break; 58 case DBL_EXP_INFNAN: /* Inf or NaN; value of *ex is unspecified */ 59 break; 60 default: /* normal */ 61 *ex = u.s.dbl_exp - (DBL_EXP_BIAS - 1); 62 u.s.dbl_exp = DBL_EXP_BIAS - 1; 63 break; 64 } 65 return (u.v); 66 } 67