1/*-
2 * See the file LICENSE for redistribution information.
3 *
4 * Copyright (c) 1996,2008 Oracle.  All rights reserved.
5 */
6/*
7 * Copyright (c) 1990, 1993
8 *	The Regents of the University of California.  All rights reserved.
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 * $Id: memmove.c,v 12.8 2008/01/08 20:58:08 bostic Exp $
35 */
36
37#include "db_config.h"
38
39#include "db_int.h"
40
41/*
42 * sizeof(word) MUST BE A POWER OF TWO
43 * SO THAT wmask BELOW IS ALL ONES
44 */
45typedef	int word;		/* "word" used for optimal copy speed */
46
47#undef	wsize
48#define	wsize	sizeof(word)
49#undef	wmask
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#ifdef MEMCOPY
58/*
59 * PUBLIC: #ifndef HAVE_MEMCPY
60 * PUBLIC: void *memcpy __P((void *, const void *, size_t));
61 * PUBLIC: #endif
62 */
63void *
64memcpy(dst0, src0, length)
65#else
66#ifdef MEMMOVE
67/*
68 * PUBLIC: #ifndef HAVE_MEMMOVE
69 * PUBLIC: void *memmove __P((void *, const void *, size_t));
70 * PUBLIC: #endif
71 */
72void *
73memmove(dst0, src0, length)
74#else
75void
76bcopy(src0, dst0, length)
77#endif
78#endif
79	void *dst0;
80	const void *src0;
81	register size_t length;
82{
83	register char *dst = dst0;
84	register const char *src = src0;
85	register size_t t;
86
87	if (length == 0 || dst == src)		/* nothing to do */
88		goto done;
89
90	/*
91	 * Macros: loop-t-times; and loop-t-times, t>0
92	 */
93#undef	TLOOP
94#define	TLOOP(s) if (t) TLOOP1(s)
95#undef	TLOOP1
96#define	TLOOP1(s) do { s; } while (--t)
97
98	if ((unsigned long)dst < (unsigned long)src) {
99		/*
100		 * Copy forward.
101		 */
102		t = (size_t)src;	/* only need low bits */
103		if ((t | (size_t)dst) & wmask) {
104			/*
105			 * Try to align operands.  This cannot be done
106			 * unless the low bits match.
107			 */
108			if ((t ^ (size_t)dst) & wmask || length < wsize)
109				t = length;
110			else
111				t = wsize - (t & wmask);
112			length -= t;
113			TLOOP1(*dst++ = *src++);
114		}
115		/*
116		 * Copy whole words, then mop up any trailing bytes.
117		 */
118		t = length / wsize;
119		TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
120		t = length & wmask;
121		TLOOP(*dst++ = *src++);
122	} else {
123		/*
124		 * Copy backwards.  Otherwise essentially the same.
125		 * Alignment works as before, except that it takes
126		 * (t&wmask) bytes to align, not wsize-(t&wmask).
127		 */
128		src += length;
129		dst += length;
130		t = (size_t)src;
131		if ((t | (size_t)dst) & wmask) {
132			if ((t ^ (size_t)dst) & wmask || length <= wsize)
133				t = length;
134			else
135				t &= wmask;
136			length -= t;
137			TLOOP1(*--dst = *--src);
138		}
139		t = length / wsize;
140		TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
141		t = length & wmask;
142		TLOOP(*--dst = *--src);
143	}
144done:
145#if defined(MEMCOPY) || defined(MEMMOVE)
146	return (dst0);
147#else
148	return;
149#endif
150}
151