1 /* $NetBSD: compat_frexp_ieee754.c,v 1.5 2010/04/23 19:04:54 drochner Exp $ */ 2 3 /* 4 * Copyright (c) 1992, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This software was developed by the Computer Systems Engineering group 8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 9 * contributed to Berkeley. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * from: Header: frexp.c,v 1.1 91/07/07 04:45:01 torek Exp 36 */ 37 38 #include <sys/cdefs.h> 39 #if defined(LIBC_SCCS) && !defined(lint) 40 #if 0 41 static char sccsid[] = "@(#)frexp.c 8.1 (Berkeley) 6/4/93"; 42 #else 43 __RCSID("$NetBSD: compat_frexp_ieee754.c,v 1.5 2010/04/23 19:04:54 drochner Exp $"); 44 #endif 45 #endif /* LIBC_SCCS and not lint */ 46 47 #include <sys/types.h> 48 #include <machine/ieee.h> 49 50 double frexp(double, int *); 51 52 /* 53 * Split the given value into a fraction in the range [0.5, 1.0) and 54 * an exponent, such that frac * (2^exp) == value. If value is 0, 55 * return 0. 56 */ 57 double 58 frexp(double value, int *eptr) 59 { 60 union ieee_double_u u; 61 62 if (value) { 63 /* 64 * Fractions in [0.5..1.0) have an exponent of 2^-1. 65 * Leave Inf and NaN alone, however. 66 */ 67 u.dblu_d = value; 68 if (u.dblu_dbl.dbl_exp != DBL_EXP_INFNAN) { 69 *eptr = 0; 70 if (u.dblu_dbl.dbl_exp == 0) { 71 /* denormal, scale out of mantissa */ 72 *eptr = -DBL_FRACBITS; 73 u.dblu_d *= 4.50359962737049600000e+15; 74 } 75 *eptr += u.dblu_dbl.dbl_exp - (DBL_EXP_BIAS - 1); 76 u.dblu_dbl.dbl_exp = DBL_EXP_BIAS - 1; 77 } 78 return (u.dblu_d); 79 } else { 80 *eptr = 0; 81 return (value); 82 } 83 } 84