Home | History | Annotate | Line # | Download | only in quad
floatdisf.c revision 1.8 
      1 /*	$NetBSD: floatdisf.c,v 1.8 2012/03/13 21:13:42 christos 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 
     36 #include <sys/cdefs.h>
     37 #if defined(LIBC_SCCS) && !defined(lint)
     38 #if 0
     39 static char sccsid[] = "@(#)floatdisf.c	8.1 (Berkeley) 6/4/93";
     40 #else
     41 __RCSID("$NetBSD: floatdisf.c,v 1.8 2012/03/13 21:13:42 christos Exp $");
     42 #endif
     43 #endif /* LIBC_SCCS and not lint */
     44 
     45 #include "quad.h"
     46 
     47 /*
     48  * Convert (signed) quad to float.
     49  */
     50 float
     51 __floatdisf(quad_t x)
     52 {
     53 	float f;
     54 	union uu u;
     55 	int neg;
     56 
     57 	/*
     58 	 * Get an unsigned number first, by negating if necessary.
     59 	 */
     60 	if (x < 0)
     61 		u.q = -x, neg = 1;
     62 	else
     63 		u.q = x, neg = 0;
     64 
     65 	/*
     66 	 * Now u.ul[H] has the factor of 2^32 (or whatever) and u.ul[L]
     67 	 * has the units.  Ideally we could just set f, add INT_BITS to
     68 	 * its exponent, and then add the units, but this is portable
     69 	 * code and does not know how to get at an exponent.  Machine-
     70 	 * specific code may be able to do this more efficiently.
     71 	 *
     72 	 * Using double here may be excessive paranoia.
     73 	 */
     74 	f = (double)u.ul[H] * (((int)1 << (unsigned int)(INT_BITS - 2)) * 4.0);
     75 	f += u.ul[L];
     76 
     77 	return (neg ? -f : f);
     78 }
     79