/*-
 * Copyright (c) 1992 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.
 *
 * %sccs.include.redist.c%
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)fixunsdfdi.c	5.3 (Berkeley) 06/02/92";
#endif /* LIBC_SCCS and not lint */

#include "quad.h"

#ifndef UQUAD_MAX	/* should be in <limits.h> maybe? */
#define	UQUAD_MAX ((u_quad)0 - 1)
#endif

#define	ONE_FOURTH	(1 << (LONG_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
__fixunsdfdi(double x)
{
	double toppart;
	union uu t;

	if (x < 0)
		return (UQUAD_MAX);	/* ??? should be 0?  ERANGE??? */
	if (x >= UQUAD_MAX)
		return (UQUAD_MAX);
	/*
	 * Get the upper part of the result.  Note that the divide
	 * may round up; we want to avoid this if possible, so we
	 * subtract `1/2' first.
	 */
	toppart = (x - ONE_HALF) / ONE;
	/*
	 * Now build a u_quad out of the top part.  The difference
	 * between x and this is the bottom part (this may introduce
	 * a few fuzzy bits, but what the heck).  With any luck this
	 * difference will be nonnegative: x should wind up in the
	 * range [0..ULONG_MAX].  For paranoia, we assume [LONG_MIN..
	 * 2*ULONG_MAX] instead.
	 */
	t.ul[H] = (unsigned long)toppart;
	t.ul[L] = 0;
	x -= (double)t.uq;
	if (x < 0) {
		t.ul[H]--;
		x += ULONG_MAX;
	}
	if (x > ULONG_MAX) {
		t.ul[H]++;
		x -= ULONG_MAX;
	}
	t.ul[L] = (u_long)x;
	return (t.uq);
}