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floatdisf.c revision 1.4 
      1 /*	$NetBSD: floatdisf.c,v 1.4 1997/07/13 20:01:47 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. All advertising materials mentioning features or use of this software
     20  *    must display the following acknowledgement:
     21  *	This product includes software developed by the University of
     22  *	California, Berkeley and its contributors.
     23  * 4. Neither the name of the University nor the names of its contributors
     24  *    may be used to endorse or promote products derived from this software
     25  *    without specific prior written permission.
     26  *
     27  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     28  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     29  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     30  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     31  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     32  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     33  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     34  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     35  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     36  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     37  * SUCH DAMAGE.
     38  */
     39 
     40 #include <sys/cdefs.h>
     41 #if defined(LIBC_SCCS) && !defined(lint)
     42 #if 0
     43 static char sccsid[] = "@(#)floatdisf.c	8.1 (Berkeley) 6/4/93";
     44 #else
     45 __RCSID("$NetBSD: floatdisf.c,v 1.4 1997/07/13 20:01:47 christos Exp $");
     46 #endif
     47 #endif /* LIBC_SCCS and not lint */
     48 
     49 #include "quad.h"
     50 
     51 /*
     52  * Convert (signed) quad to float.
     53  */
     54 float
     55 __floatdisf(x)
     56 	quad_t x;
     57 {
     58 	float f;
     59 	union uu u;
     60 	int neg;
     61 
     62 	/*
     63 	 * Get an unsigned number first, by negating if necessary.
     64 	 */
     65 	if (x < 0)
     66 		u.q = -x, neg = 1;
     67 	else
     68 		u.q = x, neg = 0;
     69 
     70 	/*
     71 	 * Now u.ul[H] has the factor of 2^32 (or whatever) and u.ul[L]
     72 	 * has the units.  Ideally we could just set f, add LONG_BITS to
     73 	 * its exponent, and then add the units, but this is portable
     74 	 * code and does not know how to get at an exponent.  Machine-
     75 	 * specific code may be able to do this more efficiently.
     76 	 *
     77 	 * Using double here may be excessive paranoia.
     78 	 */
     79 	f = (double)u.ul[H] * (((long)1 << (LONG_BITS - 2)) * 4.0);
     80 	f += u.ul[L];
     81 
     82 	return (neg ? -f : f);
     83 }
     84