xref: /freebsd/lib/libc/string/bcopy.c (revision 380a989b3223d455375b4fae70fd0b9bdd43bafb)
1 /*-
2  * Copyright (c) 1990, 1993
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * This code is derived from software contributed to Berkeley by
6  * Chris Torek.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  * 3. All advertising materials mentioning features or use of this software
17  *    must display the following acknowledgement:
18  *	This product includes software developed by the University of
19  *	California, Berkeley and its contributors.
20  * 4. Neither the name of the University nor the names of its contributors
21  *    may be used to endorse or promote products derived from this software
22  *    without specific prior written permission.
23  *
24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34  * SUCH DAMAGE.
35  */
36 
37 #if defined(LIBC_SCCS) && !defined(lint)
38 static char sccsid[] = "@(#)bcopy.c	8.1 (Berkeley) 6/4/93";
39 #endif /* LIBC_SCCS and not lint */
40 
41 #include <sys/cdefs.h>
42 #include <string.h>
43 
44 /*
45  * sizeof(word) MUST BE A POWER OF TWO
46  * SO THAT wmask BELOW IS ALL ONES
47  */
48 typedef	int word;		/* "word" used for optimal copy speed */
49 
50 #define	wsize	sizeof(word)
51 #define	wmask	(wsize - 1)
52 
53 /*
54  * Copy a block of memory, handling overlap.
55  * This is the routine that actually implements
56  * (the portable versions of) bcopy, memcpy, and memmove.
57  */
58 #ifdef MEMCOPY
59 void *
60 memcpy(dst0, src0, length)
61 #else
62 #ifdef MEMMOVE
63 void *
64 memmove(dst0, src0, length)
65 #else
66 void
67 bcopy(src0, dst0, length)
68 #endif
69 #endif
70 	void *dst0;
71 	const void *src0;
72 	register size_t length;
73 {
74 	register char *dst = dst0;
75 	register const char *src = src0;
76 	register size_t t;
77 
78 	if (length == 0 || dst == src)		/* nothing to do */
79 		goto done;
80 
81 	/*
82 	 * Macros: loop-t-times; and loop-t-times, t>0
83 	 */
84 #define	TLOOP(s) if (t) TLOOP1(s)
85 #define	TLOOP1(s) do { s; } while (--t)
86 
87 	if ((unsigned long)dst < (unsigned long)src) {
88 		/*
89 		 * Copy forward.
90 		 */
91 		t = (int)src;	/* only need low bits */
92 		if ((t | (int)dst) & wmask) {
93 			/*
94 			 * Try to align operands.  This cannot be done
95 			 * unless the low bits match.
96 			 */
97 			if ((t ^ (int)dst) & wmask || length < wsize)
98 				t = length;
99 			else
100 				t = wsize - (t & wmask);
101 			length -= t;
102 			TLOOP1(*dst++ = *src++);
103 		}
104 		/*
105 		 * Copy whole words, then mop up any trailing bytes.
106 		 */
107 		t = length / wsize;
108 		TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
109 		t = length & wmask;
110 		TLOOP(*dst++ = *src++);
111 	} else {
112 		/*
113 		 * Copy backwards.  Otherwise essentially the same.
114 		 * Alignment works as before, except that it takes
115 		 * (t&wmask) bytes to align, not wsize-(t&wmask).
116 		 */
117 		src += length;
118 		dst += length;
119 		t = (int)src;
120 		if ((t | (int)dst) & wmask) {
121 			if ((t ^ (int)dst) & wmask || length <= wsize)
122 				t = length;
123 			else
124 				t &= wmask;
125 			length -= t;
126 			TLOOP1(*--dst = *--src);
127 		}
128 		t = length / wsize;
129 		TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
130 		t = length & wmask;
131 		TLOOP(*--dst = *--src);
132 	}
133 done:
134 #if defined(MEMCOPY) || defined(MEMMOVE)
135 	return (dst0);
136 #else
137 	return;
138 #endif
139 }
140