1/*	$OpenBSD: bcopy.c,v 1.7 2015/08/31 02:53:57 guenther 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 */
48void
49bcopy(const void *src0, void *dst0, size_t length)
50{
51	char *dst = dst0;
52	const char *src = src0;
53	size_t t;
54
55	if (length == 0 || dst == src)		/* nothing to do */
56		goto done;
57
58	/*
59	 * Macros: loop-t-times; and loop-t-times, t>0
60	 */
61#define	TLOOP(s) if (t) TLOOP1(s)
62#define	TLOOP1(s) do { s; } while (--t)
63
64	if ((unsigned long)dst < (unsigned long)src) {
65		/*
66		 * Copy forward.
67		 */
68		t = (long)src;	/* only need low bits */
69		if ((t | (long)dst) & wmask) {
70			/*
71			 * Try to align operands.  This cannot be done
72			 * unless the low bits match.
73			 */
74			if ((t ^ (long)dst) & wmask || length < wsize)
75				t = length;
76			else
77				t = wsize - (t & wmask);
78			length -= t;
79			TLOOP1(*dst++ = *src++);
80		}
81		/*
82		 * Copy whole words, then mop up any trailing bytes.
83		 */
84		t = length / wsize;
85		TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
86		t = length & wmask;
87		TLOOP(*dst++ = *src++);
88	} else {
89		/*
90		 * Copy backwards.  Otherwise essentially the same.
91		 * Alignment works as before, except that it takes
92		 * (t&wmask) bytes to align, not wsize-(t&wmask).
93		 */
94		src += length;
95		dst += length;
96		t = (long)src;
97		if ((t | (long)dst) & wmask) {
98			if ((t ^ (long)dst) & wmask || length <= wsize)
99				t = length;
100			else
101				t &= wmask;
102			length -= t;
103			TLOOP1(*--dst = *--src);
104		}
105		t = length / wsize;
106		TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
107		t = length & wmask;
108		TLOOP(*--dst = *--src);
109	}
110done:
111	return;
112}
113DEF_WEAK(bcopy);
114