xref: /src/lib/libc/quad/fixunsdfdi.c

/*	$NetBSD: fixunsdfdi.c,v 1.9 2012/03/13 21:13:42 christos Exp $	*/

/*-
 * Copyright (c) 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This software was developed by the Computer Systems Engineering group
 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
 * contributed to Berkeley.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)fixunsdfdi.c	8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: fixunsdfdi.c,v 1.9 2012/03/13 21:13:42 christos Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include "quad.h"

#define	ONE_FOURTH	((int)1 << (unsigned int)(INT_BITS - 2))
#define	ONE_HALF	(ONE_FOURTH * 2.0)
#define	ONE		(ONE_FOURTH * 4.0)

/*
 * Convert double to (unsigned) quad.
 * Not sure what to do with negative numbers---for now, anything out
 * of range becomes UQUAD_MAX.
 */
u_quad_t
__fixunsdfdi(double x)
{
	union uu t;
	unsigned int tmp;

	if (x < 0)
		return (UQUAD_MAX);	/* ??? should be 0?  ERANGE??? */
#ifdef notdef				/* this falls afoul of a GCC bug */
	if (x >= UQUAD_MAX)
		return (UQUAD_MAX);
#else					/* so we wire in 2^64-1 instead */
	if (x >= 18446744073709551615.0)	/* XXX */
		return (UQUAD_MAX);
#endif
	/*
	 * Now we know that 0 <= x <= 18446744073709549568.  The upper
	 * limit is one ulp less than 18446744073709551615 tested for above.
	 * Dividing this by 2^32 will *not* round irrespective of any
	 * rounding modes (except if the result is an IEEE denorm).
	 * Furthermore, the quotient will fit into a 32-bit integer.
	 */
	tmp = x / ONE;
	t.ul[L] = (unsigned int) (x - tmp * ONE);
	t.ul[H] = tmp;
	return (t.uq);
}