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DEFINITIONS
This source file includes following definitions.
- memmove
1 /*
2 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
3 * The President and Fellows of Harvard College.
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. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 /*
31 * This file is shared between libc and the kernel, so don't put anything
32 * in here that won't work in both contexts.
33 */
34
35 #ifdef _KERNEL
36 #include <types.h>
37 #include <lib.h>
38 #else
39 #include <stdint.h>
40 #include <string.h>
41 #endif
42
43 /*
44 * C standard function - copy a block of memory, handling overlapping
45 * regions correctly.
46 */
47
48 void *
49 memmove(void *dst, const void *src, size_t len)
50 {
51 size_t i;
52
53 /*
54 * If the buffers don't overlap, it doesn't matter what direction
55 * we copy in. If they do, it does, so just assume they always do.
56 * We don't concern ourselves with the possibility that the region
57 * to copy might roll over across the top of memory, because it's
58 * not going to happen.
59 *
60 * If the destination is above the source, we have to copy
61 * back to front to avoid overwriting the data we want to
62 * copy.
63 *
64 * dest: dddddddd
65 * src: ssssssss ^
66 * | ^ |___|
67 * |___|
68 *
69 * If the destination is below the source, we have to copy
70 * front to back.
71 *
72 * dest: dddddddd
73 * src: ^ ssssssss
74 * |___| ^ |
75 * |___|
76 */
77
78 if ((uintptr_t)dst < (uintptr_t)src) {
79 /*
80 * As author/maintainer of libc, take advantage of the
81 * fact that we know memcpy copies forwards.
82 */
83 return memcpy(dst, src, len);
84 }
85
86 /*
87 * Copy by words in the common case. Look in memcpy.c for more
88 * information.
89 */
90
91 if ((uintptr_t)dst % sizeof(long) == 0 &&
92 (uintptr_t)src % sizeof(long) == 0 &&
93 len % sizeof(long) == 0) {
94
95 long *d = dst;
96 const long *s = src;
97
98 /*
99 * The reason we copy index i-1 and test i>0 is that
100 * i is unsigned -- so testing i>=0 doesn't work.
101 */
102
103 for (i=len/sizeof(long); i>0; i--) {
104 d[i-1] = s[i-1];
105 }
106 }
107 else {
108 char *d = dst;
109 const char *s = src;
110
111 for (i=len; i>0; i--) {
112 d[i-1] = s[i-1];
113 }
114 }
115
116 return dst;
117 }