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 */
40typedef	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
51void *
52memcpy(void *dst0, const void *src0, size_t length)
53#else
54#ifdef MEMMOVE
55void *
56memmove(void *dst0, const void *src0, size_t length)
57#else
58void
59bcopy(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	}
122done:
123#if defined(MEMCOPY) || defined(MEMMOVE)
124	return (dst0);
125#else
126	return;
127#endif
128}
129