bcopy.c revision 330897 
1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 1993
5 *	The Regents of the University of California.  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#if defined(LIBC_SCCS) && !defined(lint)
36static char sccsid[] = "@(#)bcopy.c	8.1 (Berkeley) 6/4/93";
37#endif /* LIBC_SCCS and not lint */
38#include <sys/cdefs.h>
39__FBSDID("$FreeBSD: stable/11/lib/libc/string/bcopy.c 330897 2018-03-14 03:19:51Z eadler $");
40
41#include <sys/types.h>
42
43/*
44 * sizeof(word) MUST BE A POWER OF TWO
45 * SO THAT wmask BELOW IS ALL ONES
46 */
47typedef	int word;		/* "word" used for optimal copy speed */
48
49#define	wsize	sizeof(word)
50#define	wmask	(wsize - 1)
51
52/*
53 * Copy a block of memory, handling overlap.
54 * This is the routine that actually implements
55 * (the portable versions of) bcopy, memcpy, and memmove.
56 */
57#if defined(MEMCOPY) || defined(MEMMOVE)
58#include <string.h>
59
60void *
61#ifdef MEMCOPY
62memcpy
63#else
64memmove
65#endif
66(void *dst0, const void *src0, size_t length)
67#else
68#include <strings.h>
69
70void
71bcopy(const void *src0, void *dst0, size_t length)
72#endif
73{
74	char *dst = dst0;
75	const char *src = src0;
76	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 = (uintptr_t)src;	/* only need low bits */
92		if ((t | (uintptr_t)dst) & wmask) {
93			/*
94			 * Try to align operands.  This cannot be done
95			 * unless the low bits match.
96			 */
97			if ((t ^ (uintptr_t)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 = (uintptr_t)src;
120		if ((t | (uintptr_t)dst) & wmask) {
121			if ((t ^ (uintptr_t)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	}
133done:
134#if defined(MEMCOPY) || defined(MEMMOVE)
135	return (dst0);
136#else
137	return;
138#endif
139}
140