1 /* $OpenBSD: memmove.c,v 1.1 2014/11/30 19:43:56 deraadt Exp $ */
2 /*-
3 * Copyright (c) 1990 The Regents of the University of California.
4 * All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * Chris Torek.
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 #include <string.h>
35
36 /*
37 * sizeof(word) MUST BE A POWER OF TWO
38 * SO THAT wmask BELOW IS ALL ONES
39 */
40 typedef long word; /* "word" used for optimal copy speed */
41
42 #define wsize sizeof(word)
43 #define wmask (wsize - 1)
44
45 /*
46 * Copy a block of memory, handling overlap.
47 */
48 void *
memmove(void * dst0,const void * src0,size_t length)49 memmove(void *dst0, const void *src0, size_t length)
50 {
51 char *dst = dst0;
52 const char *src = src0;
53 size_t t;
54
55 if (length == 0 || dst == src) /* nothing to do */
56 goto done;
57
58 /*
59 * Macros: loop-t-times; and loop-t-times, t>0
60 */
61 #define TLOOP(s) if (t) TLOOP1(s)
62 #define TLOOP1(s) do { s; } while (--t)
63
64 if ((unsigned long)dst < (unsigned long)src) {
65 /*
66 * Copy forward.
67 */
68 t = (long)src; /* only need low bits */
69 if ((t | (long)dst) & wmask) {
70 /*
71 * Try to align operands. This cannot be done
72 * unless the low bits match.
73 */
74 if ((t ^ (long)dst) & wmask || length < wsize)
75 t = length;
76 else
77 t = wsize - (t & wmask);
78 length -= t;
79 TLOOP1(*dst++ = *src++);
80 }
81 /*
82 * Copy whole words, then mop up any trailing bytes.
83 */
84 t = length / wsize;
85 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
86 t = length & wmask;
87 TLOOP(*dst++ = *src++);
88 } else {
89 /*
90 * Copy backwards. Otherwise essentially the same.
91 * Alignment works as before, except that it takes
92 * (t&wmask) bytes to align, not wsize-(t&wmask).
93 */
94 src += length;
95 dst += length;
96 t = (long)src;
97 if ((t | (long)dst) & wmask) {
98 if ((t ^ (long)dst) & wmask || length <= wsize)
99 t = length;
100 else
101 t &= wmask;
102 length -= t;
103 TLOOP1(*--dst = *--src);
104 }
105 t = length / wsize;
106 TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
107 t = length & wmask;
108 TLOOP(*--dst = *--src);
109 }
110 done:
111 return (dst0);
112 }
113