bcmp.c revision 48020 
1/*
2 * Copyright (c) 1987, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. 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 * $Id: bcmp.c,v 1.4 1997/02/22 09:39:51 peter Exp $
34 */
35
36#include <string.h>
37#include <machine/endian.h>
38
39typedef	const void	*cvp;
40typedef	const unsigned char	*ustring;
41typedef unsigned long	ul;
42typedef const unsigned long	*culp;
43
44/*
45 * bcmp -- vax cmpc3 instruction
46 */
47int
48bcmp(b1, b2, length)
49	const void *b1, *b2;
50	register size_t length;
51{
52#if BYTE_ORDER == LITTLE_ENDIAN
53	/*
54	 * The following code is endian specific.  Changing it from
55	 * little-endian to big-endian is fairly trivial, but making
56	 * it do both is more difficult.
57	 *
58	 * Note that this code will reference the entire longword which
59	 * includes the final byte to compare.  I don't believe this is
60	 * a problem since AFAIK, objects are not protected at smaller
61	 * than longword boundaries.
62	 */
63	int	shl, shr, len = length;
64	ustring	p1 = b1, p2 = b2;
65	ul	va, vb;
66
67	if (len == 0)
68		return (0);
69
70	/*
71	 * align p1 to a longword boundary
72	 */
73	while ((long)p1 & (sizeof(long) - 1)) {
74		if (*p1++ != *p2++)
75			return (1);
76		if (--len <= 0)
77			return (0);
78	}
79
80	/*
81	 * align p2 to longword boundary and calculate the shift required to
82	 * align p1 and p2
83	 */
84	shr = (long)p2 & (sizeof(long) - 1);
85	if (shr != 0) {
86		p2 -= shr;			/* p2 now longword aligned */
87		shr <<= 3;			/* offset in bits */
88		shl = (sizeof(long) << 3) - shr;
89
90		va = *(culp)p2;
91		p2 += sizeof(long);
92
93		while ((len -= sizeof(long)) >= 0) {
94			vb = *(culp)p2;
95			p2 += sizeof(long);
96			if (*(culp)p1 != (va >> shr | vb << shl))
97				return (1);
98			p1 += sizeof(long);
99			va = vb;
100		}
101		/*
102		 * At this point, len is between -sizeof(long) and -1,
103		 * representing 0 .. sizeof(long)-1 bytes remaining.
104		 */
105		if (!(len += sizeof(long)))
106			return (0);
107
108		len <<= 3;		/* remaining length in bits */
109		/*
110		 * The following is similar to the `if' condition
111		 * inside the above while loop.  The ?: is necessary
112		 * to avoid accessing the longword after the longword
113		 * containing the last byte to be compared.
114		 */
115		return ((((va >> shr | ((shl < len) ? *(culp)p2 << shl : 0)) ^
116		    *(culp)p1) & ((1L << len) - 1)) != 0);
117	} else {
118		/* p1 and p2 have common alignment so no shifting needed */
119		while ((len -= sizeof(long)) >= 0) {
120			if (*(culp)p1 != *(culp)p2)
121				return (1);
122			p1 += sizeof(long);
123			p2 += sizeof(long);
124		}
125
126		/*
127		 * At this point, len is between -sizeof(long) and -1,
128		 * representing 0 .. sizeof(long)-1 bytes remaining.
129		 */
130		if (!(len += sizeof(long)))
131			return (0);
132
133		return (((*(culp)p1 ^ *(culp)p2)
134			 & ((1L << (len << 3)) - 1)) != 0);
135	}
136#else
137	register char *p1, *p2;
138
139	if (length == 0)
140		return(0);
141	p1 = (char *)b1;
142	p2 = (char *)b2;
143	do
144		if (*p1++ != *p2++)
145			break;
146	while (--length);
147	return(length);
148#endif
149}
150