UbixOS V2 2.0

memcmp.S
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1 /*-
2 * Copyright (c) 2002-2018 The UbixOS Project.
3 * All rights reserved.
4 *
5 * This was developed by Christopher W. Olsen for the UbixOS Project.
6 *
7 * Redistribution and use in source and binary forms, with or without modification, are permitted
8 * provided that the following conditions are met:
9 *
10 * 1) Redistributions of source code must retain the above copyright notice, this list of
11 * conditions, the following disclaimer and the list of authors.
12 * 2) Redistributions in binary form must reproduce the above copyright notice, this list of
13 * conditions, the following disclaimer and the list of authors in the documentation and/or
14 * other materials provided with the distribution.
15 * 3) Neither the name of the UbixOS Project nor the names of its contributors may be used to
16 * endorse or promote products derived from this software without specific prior written
17 * permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
20 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
21 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
22 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
24 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
25 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
26 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 #include <i386/asmacros.h>
30
31 ENTRY(memcmp)
32 pushl %edi
33 pushl %esi
34 movl 12(%esp),%edi
35 movl 16(%esp),%esi
36 cld /* set compare direction forward */
37
38 movl 20(%esp),%ecx /* compare by words */
39 shrl $2,%ecx
40 repe
41 cmpsl
42 jne L5 /* do we match so far? */
43
44 movl 20(%esp),%ecx /* compare remainder by bytes */
45 andl $3,%ecx
46 repe
47 cmpsb
48 jne L6 /* do we match? */
49
50 xorl %eax,%eax /* we match, return zero */
51 popl %esi
52 popl %edi
53 ret
54
55 L5: movl $4,%ecx /* We know that one of the next */
56 subl %ecx,%edi /* four pairs of bytes do not */
57 subl %ecx,%esi /* match. */
58 repe
59 cmpsb
60 L6: movzbl -1(%edi),%eax /* Perform unsigned comparison */
61 movzbl -1(%esi),%edx
62 subl %edx,%eax
63 popl %esi
64 popl %edi
65 ret
66 END(memcmp)