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/contrib/ntp/libntp/memmove.c

https://bitbucket.org/freebsd/freebsd-head/
C | 140 lines | 68 code | 10 blank | 62 comment | 15 complexity | f1669d8c02e9336e60902a1725291d2d MD5 | raw file
  1/*-
  2 * Copyright (c) 1990, 1993
  3 *	The Regents of the University of California.  All rights reserved.
  4 *
  5 * This code is derived from software contributed to Berkeley by
  6 * Chris Torek.
  7 *
  8 * Redistribution and use in source and binary forms, with or without
  9 * modification, are permitted provided that the following conditions
 10 * are met:
 11 * 1. Redistributions of source code must retain the above copyright
 12 *    notice, this list of conditions and the following disclaimer.
 13 * 2. Redistributions in binary form must reproduce the above copyright
 14 *    notice, this list of conditions and the following disclaimer in the
 15 *    documentation and/or other materials provided with the distribution.
 16 * 3. All advertising materials mentioning features or use of this software
 17 *    must display the following acknowledgement:
 18 *	This product includes software developed by the University of
 19 *	California, Berkeley and its contributors.
 20 * 4. Neither the name of the University nor the names of its contributors
 21 *    may be used to endorse or promote products derived from this software
 22 *    without specific prior written permission.
 23 *
 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 34 * SUCH DAMAGE.
 35 */
 36
 37#if defined(LIBC_SCCS) && !defined(lint)
 38static char sccsid[] = "@(#)bcopy.c	8.1 (Berkeley) 6/4/93";
 39#endif /* LIBC_SCCS and not lint */
 40
 41#ifdef HAVE_CONFIG_H
 42# include <config.h>
 43#endif
 44
 45#ifndef HAVE_MEMMOVE
 46#ifdef HAVE_SYS_TYPES_H
 47#include <sys/types.h>
 48#endif
 49#include <string.h>
 50
 51#include "l_stdlib.h"
 52
 53/*
 54 * sizeof(word) MUST BE A POWER OF TWO
 55 * SO THAT wmask BELOW IS ALL ONES
 56 */
 57typedef	int word;		/* "word" used for optimal copy speed */
 58
 59#define	wsize	sizeof(word)
 60#define	wmask	(wsize - 1)
 61
 62/*
 63 * Copy a block of memory, handling overlap.
 64 * This is the routine that actually implements
 65 * (the portable versions of) bcopy, memcpy, and memmove.
 66 */
 67void *
 68memmove(
 69	void *dst0,
 70	const void *src0,
 71	register size_t length
 72	)
 73{
 74	register char *dst = dst0;
 75	register const char *src = src0;
 76	register 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 = (int)src;	/* only need low bits */
 92		if ((t | (int)dst) & wmask) {
 93			/*
 94			 * Try to align operands.  This cannot be done
 95			 * unless the low bits match.
 96			 */
 97			if ((t ^ (int)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 = *(const word *)src; src += wsize;
109		    dst += wsize);
110		t = length & wmask;
111		TLOOP(*dst++ = *src++);
112	} else {
113		/*
114		 * Copy backwards.  Otherwise essentially the same.
115		 * Alignment works as before, except that it takes
116		 * (t&wmask) bytes to align, not wsize-(t&wmask).
117		 */
118		src += length;
119		dst += length;
120		t = (int)src;
121		if ((t | (int)dst) & wmask) {
122			if ((t ^ (int)dst) & wmask || length <= wsize)
123			    t = length;
124			else
125			    t &= wmask;
126			length -= t;
127			TLOOP1(*--dst = *--src);
128		}
129		t = length / wsize;
130		TLOOP(src -= wsize; dst -= wsize;
131		    *(word *)dst = *(const word *)src);
132		t = length & wmask;
133		TLOOP(*--dst = *--src);
134	}
135    done:
136	return (dst0);
137}
138#else
139int memmove_bs;
140#endif