usr/src/lib/libc/quad/subdi3.c

/*-
 * 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[] = "@(#)subdi3.c    5.4 (Berkeley) %G%";
#endif /* LIBC_SCCS and not lint */

#include "quad.h"

/*
 * Subtract two quad values.  This is trivial since a one-bit carry
 * from a single u_long difference x-y occurs if and only if (x-y) > x.
 */
quad
__subdi3(quad a, quad b)
{
        union uu aa, bb, diff;

        aa.q = a;
        bb.q = b;
        diff.ul[L] = aa.ul[L] - bb.ul[L];
        diff.ul[H] = aa.ul[H] - bb.ul[H] - (diff.ul[L] > aa.ul[L]);
        return (diff.q);
}