bcopy.c revision 121531 
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)
38static char sccsid[] = "@(#)bcopy.c	8.1 (Berkeley) 6/4/93";
39#endif /* LIBC_SCCS and not lint */
40#include <sys/cdefs.h>
41__FBSDID("$FreeBSD: head/lib/libc/string/bcopy.c 121531 2003-10-26 03:55:58Z peter $");
42
43#include <sys/types.h>
44
45/*
46 * sizeof(word) MUST BE A POWER OF TWO
47 * SO THAT wmask BELOW IS ALL ONES
48 */
49typedef	int word;		/* "word" used for optimal copy speed */
50
51#define	wsize	sizeof(word)
52#define	wmask	(wsize - 1)
53
54/*
55 * Copy a block of memory, handling overlap.
56 * This is the routine that actually implements
57 * (the portable versions of) bcopy, memcpy, and memmove.
58 */
59#if defined(MEMCOPY) || defined(MEMMOVE)
60#include <string.h>
61
62void *
63#ifdef MEMCOPY
64memcpy
65#else
66memmove
67#endif
68(void *dst0, const void *src0, size_t length)
69#else
70#include <strings.h>
71
72void
73bcopy(const void *src0, void *dst0, size_t length)
74#endif
75{
76	char *dst = dst0;
77	const char *src = src0;
78	size_t t;
79
80	if (length == 0 || dst == src)		/* nothing to do */
81		goto done;
82
83	/*
84	 * Macros: loop-t-times; and loop-t-times, t>0
85	 */
86#define	TLOOP(s) if (t) TLOOP1(s)
87#define	TLOOP1(s) do { s; } while (--t)
88
89	if ((unsigned long)dst < (unsigned long)src) {
90		/*
91		 * Copy forward.
92		 */
93		t = (uintptr_t)src;	/* only need low bits */
94		if ((t | (uintptr_t)dst) & wmask) {
95			/*
96			 * Try to align operands.  This cannot be done
97			 * unless the low bits match.
98			 */
99			if ((t ^ (uintptr_t)dst) & wmask || length < wsize)
100				t = length;
101			else
102				t = wsize - (t & wmask);
103			length -= t;
104			TLOOP1(*dst++ = *src++);
105		}
106		/*
107		 * Copy whole words, then mop up any trailing bytes.
108		 */
109		t = length / wsize;
110		TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
111		t = length & wmask;
112		TLOOP(*dst++ = *src++);
113	} else {
114		/*
115		 * Copy backwards.  Otherwise essentially the same.
116		 * Alignment works as before, except that it takes
117		 * (t&wmask) bytes to align, not wsize-(t&wmask).
118		 */
119		src += length;
120		dst += length;
121		t = (uintptr_t)src;
122		if ((t | (uintptr_t)dst) & wmask) {
123			if ((t ^ (uintptr_t)dst) & wmask || length <= wsize)
124				t = length;
125			else
126				t &= wmask;
127			length -= t;
128			TLOOP1(*--dst = *--src);
129		}
130		t = length / wsize;
131		TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
132		t = length & wmask;
133		TLOOP(*--dst = *--src);
134	}
135done:
136#if defined(MEMCOPY) || defined(MEMMOVE)
137	return (dst0);
138#else
139	return;
140#endif
141}
142