Annotation of sys/lib/libkern/subdi3.c, Revision 1.1
1.1 ! nbrk 1: /*-
! 2: * Copyright (c) 1992, 1993
! 3: * The Regents of the University of California. All rights reserved.
! 4: *
! 5: * This software was developed by the Computer Systems Engineering group
! 6: * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
! 7: * contributed to Berkeley.
! 8: *
! 9: * Redistribution and use in source and binary forms, with or without
! 10: * modification, are permitted provided that the following conditions
! 11: * are met:
! 12: * 1. Redistributions of source code must retain the above copyright
! 13: * notice, this list of conditions and the following disclaimer.
! 14: * 2. Redistributions in binary form must reproduce the above copyright
! 15: * notice, this list of conditions and the following disclaimer in the
! 16: * documentation and/or other materials provided with the distribution.
! 17: * 3. Neither the name of the University nor the names of its contributors
! 18: * may be used to endorse or promote products derived from this software
! 19: * without specific prior written permission.
! 20: *
! 21: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
! 22: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
! 23: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
! 24: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
! 25: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
! 26: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
! 27: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
! 28: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
! 29: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
! 30: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
! 31: * SUCH DAMAGE.
! 32: */
! 33:
! 34: #if defined(LIBC_SCCS) && !defined(lint)
! 35: static char rcsid[] = "$OpenBSD: subdi3.c,v 1.5 2004/11/28 07:23:41 mickey Exp $";
! 36: #endif /* LIBC_SCCS and not lint */
! 37:
! 38: #include "quad.h"
! 39:
! 40: /*
! 41: * Subtract two quad values. This is trivial since a one-bit carry
! 42: * from a single u_int difference x-y occurs if and only if (x-y) > x.
! 43: */
! 44: quad_t
! 45: __subdi3(quad_t a, quad_t b)
! 46: {
! 47: union uu aa, bb, diff;
! 48:
! 49: aa.q = a;
! 50: bb.q = b;
! 51: diff.ul[L] = aa.ul[L] - bb.ul[L];
! 52: diff.ul[H] = aa.ul[H] - bb.ul[H] - (diff.ul[L] > aa.ul[L]);
! 53: return (diff.q);
! 54: }
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