1/*	$OpenBSD: bcopy.c,v 1.2 2017/01/24 08:09:05 kettenis Exp $ */
2
3/*-
4 * Copyright (c) 1990 The Regents of the University of California.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#include <sys/types.h>
36#include <sys/systm.h>
37
38#undef bcopy
39
40/*
41 * sizeof(word) MUST BE A POWER OF TWO
42 * SO THAT wmask BELOW IS ALL ONES
43 */
44typedef	long word;		/* "word" used for optimal copy speed */
45
46#define	wsize	sizeof(word)
47#define	wmask	(wsize - 1)
48
49/*
50 * Copy a block of memory, handling overlap.
51 * This is the routine that actually implements
52 * (the portable versions of) bcopy, memcpy, and memmove.
53 */
54void
55bcopy(const void *src0, void *dst0, size_t length)
56{
57	char *dst = dst0;
58	const char *src = src0;
59	size_t t;
60
61	if (length == 0 || dst == src)		/* nothing to do */
62		goto done;
63
64	/*
65	 * Macros: loop-t-times; and loop-t-times, t>0
66	 */
67#define	TLOOP(s) if (t) TLOOP1(s)
68#define	TLOOP1(s) do { s; } while (--t)
69
70	if ((unsigned long)dst < (unsigned long)src) {
71		/*
72		 * Copy forward.
73		 */
74		t = (long)src;	/* only need low bits */
75		if ((t | (long)dst) & wmask) {
76			/*
77			 * Try to align operands.  This cannot be done
78			 * unless the low bits match.
79			 */
80			if ((t ^ (long)dst) & wmask || length < wsize)
81				t = length;
82			else
83				t = wsize - (t & wmask);
84			length -= t;
85			TLOOP1(*dst++ = *src++);
86		}
87		/*
88		 * Copy whole words, then mop up any trailing bytes.
89		 */
90		t = length / wsize;
91		TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
92		t = length & wmask;
93		TLOOP(*dst++ = *src++);
94	} else {
95		/*
96		 * Copy backwards.  Otherwise essentially the same.
97		 * Alignment works as before, except that it takes
98		 * (t&wmask) bytes to align, not wsize-(t&wmask).
99		 */
100		src += length;
101		dst += length;
102		t = (long)src;
103		if ((t | (long)dst) & wmask) {
104			if ((t ^ (long)dst) & wmask || length <= wsize)
105				t = length;
106			else
107				t &= wmask;
108			length -= t;
109			TLOOP1(*--dst = *--src);
110		}
111		t = length / wsize;
112		TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
113		t = length & wmask;
114		TLOOP(*--dst = *--src);
115	}
116done:
117	return;
118}
119