UbixOS V2 2.0

memset.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
32 ENTRY(memset)
33 pushl %edi
34 pushl %ebx
35 movl 12(%esp),%edi
36 movzbl 16(%esp),%eax /* unsigned char, zero extend */
37 movl 20(%esp),%ecx
38 pushl %edi /* push address of buffer */
39
40 cld /* set fill direction forward */
41
42 /*
43 * if the string is too short, it's really not worth the overhead
44 * of aligning to word boundries, etc. So we jump to a plain
45 * unaligned set.
46 */
47 cmpl $0x0f,%ecx
48 jle L1
49
50 movb %al,%ah /* copy char to all bytes in word */
51 movl %eax,%edx
52 sall $16,%eax
53 orl %edx,%eax
54
55 movl %edi,%edx /* compute misalignment */
56 negl %edx
57 andl $3,%edx
58 movl %ecx,%ebx
59 subl %edx,%ebx
60
61 movl %edx,%ecx /* set until word aligned */
62 rep
63 stosb
64
65 movl %ebx,%ecx
66 shrl $2,%ecx /* set by words */
67 rep
68 stosl
69
70 movl %ebx,%ecx /* set remainder by bytes */
71 andl $3,%ecx
72 L1: rep
73 stosb
74
75 popl %eax /* pop address of buffer */
76 popl %ebx
77 popl %edi
78 ret
79 END(memset)