1 /* $OpenBSD: bcopy.c,v 1.2 2017/01/24 08:09:05 kettenis Exp $ */
2
3 /*-
4 * Copyright (c) 1990 The Regents of the University of California.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #include <sys/types.h>
36 #include <sys/systm.h>
37
38 #undef bcopy
39
40 /*
41 * sizeof(word) MUST BE A POWER OF TWO
42 * SO THAT wmask BELOW IS ALL ONES
43 */
44 typedef long word; /* "word" used for optimal copy speed */
45
46 #define wsize sizeof(word)
47 #define wmask (wsize - 1)
48
49 /*
50 * Copy a block of memory, handling overlap.
51 * This is the routine that actually implements
52 * (the portable versions of) bcopy, memcpy, and memmove.
53 */
54 void
bcopy(const void * src0,void * dst0,size_t length)55 bcopy(const void *src0, void *dst0, size_t length)
56 {
57 char *dst = dst0;
58 const char *src = src0;
59 size_t t;
60
61 if (length == 0 || dst == src) /* nothing to do */
62 goto done;
63
64 /*
65 * Macros: loop-t-times; and loop-t-times, t>0
66 */
67 #define TLOOP(s) if (t) TLOOP1(s)
68 #define TLOOP1(s) do { s; } while (--t)
69
70 if ((unsigned long)dst < (unsigned long)src) {
71 /*
72 * Copy forward.
73 */
74 t = (long)src; /* only need low bits */
75 if ((t | (long)dst) & wmask) {
76 /*
77 * Try to align operands. This cannot be done
78 * unless the low bits match.
79 */
80 if ((t ^ (long)dst) & wmask || length < wsize)
81 t = length;
82 else
83 t = wsize - (t & wmask);
84 length -= t;
85 TLOOP1(*dst++ = *src++);
86 }
87 /*
88 * Copy whole words, then mop up any trailing bytes.
89 */
90 t = length / wsize;
91 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
92 t = length & wmask;
93 TLOOP(*dst++ = *src++);
94 } else {
95 /*
96 * Copy backwards. Otherwise essentially the same.
97 * Alignment works as before, except that it takes
98 * (t&wmask) bytes to align, not wsize-(t&wmask).
99 */
100 src += length;
101 dst += length;
102 t = (long)src;
103 if ((t | (long)dst) & wmask) {
104 if ((t ^ (long)dst) & wmask || length <= wsize)
105 t = length;
106 else
107 t &= wmask;
108 length -= t;
109 TLOOP1(*--dst = *--src);
110 }
111 t = length / wsize;
112 TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
113 t = length & wmask;
114 TLOOP(*--dst = *--src);
115 }
116 done:
117 return;
118 }
119