1 /* $OpenBSD: bcopy.c,v 1.5 2005/08/08 08:05:37 espie 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 * This is the routine that actually implements
48 * (the portable versions of) bcopy, memcpy, and memmove.
49 */
50 #ifdef MEMCOPY
51 void *
memcpy(void * dst0,const void * src0,size_t length)52 memcpy(void *dst0, const void *src0, size_t length)
53 #else
54 #ifdef MEMMOVE
55 void *
56 memmove(void *dst0, const void *src0, size_t length)
57 #else
58 void
59 bcopy(const void *src0, void *dst0, size_t length)
60 #endif
61 #endif
62 {
63 char *dst = dst0;
64 const char *src = src0;
65 size_t t;
66
67 if (length == 0 || dst == src) /* nothing to do */
68 goto done;
69
70 /*
71 * Macros: loop-t-times; and loop-t-times, t>0
72 */
73 #define TLOOP(s) if (t) TLOOP1(s)
74 #define TLOOP1(s) do { s; } while (--t)
75
76 if ((unsigned long)dst < (unsigned long)src) {
77 /*
78 * Copy forward.
79 */
80 t = (long)src; /* only need low bits */
81 if ((t | (long)dst) & wmask) {
82 /*
83 * Try to align operands. This cannot be done
84 * unless the low bits match.
85 */
86 if ((t ^ (long)dst) & wmask || length < wsize)
87 t = length;
88 else
89 t = wsize - (t & wmask);
90 length -= t;
91 TLOOP1(*dst++ = *src++);
92 }
93 /*
94 * Copy whole words, then mop up any trailing bytes.
95 */
96 t = length / wsize;
97 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
98 t = length & wmask;
99 TLOOP(*dst++ = *src++);
100 } else {
101 /*
102 * Copy backwards. Otherwise essentially the same.
103 * Alignment works as before, except that it takes
104 * (t&wmask) bytes to align, not wsize-(t&wmask).
105 */
106 src += length;
107 dst += length;
108 t = (long)src;
109 if ((t | (long)dst) & wmask) {
110 if ((t ^ (long)dst) & wmask || length <= wsize)
111 t = length;
112 else
113 t &= wmask;
114 length -= t;
115 TLOOP1(*--dst = *--src);
116 }
117 t = length / wsize;
118 TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
119 t = length & wmask;
120 TLOOP(*--dst = *--src);
121 }
122 done:
123 #if defined(MEMCOPY) || defined(MEMMOVE)
124 return (dst0);
125 #else
126 return;
127 #endif
128 }
129