xref: /netbsd-src/common/lib/libc/string/bcopy.c (revision 23e81d3280fb561f21bc9bbc61f626819e130d83)

/*	$NetBSD: bcopy.c,v 1.13 2018/02/12 11:14:15 martin Exp $	*/

/*-
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)bcopy.c	8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: bcopy.c,v 1.13 2018/02/12 11:14:15 martin Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#if !defined(_KERNEL) && !defined(_STANDALONE)
#include <assert.h>
#include <string.h>
#else
#include <lib/libkern/libkern.h>
#if !defined(MEMCOPY) && defined(_STANDALONE)
#include <lib/libsa/stand.h>
#endif
#endif

#if defined(_FORTIFY_SOURCE) || defined(_STANDALONE) || defined(_KERNEL)
#undef bcopy
#undef memcpy
#undef memmove
#endif

#ifndef __OPTIMIZE_SIZE__
/*
 * sizeof(word) MUST BE A POWER OF TWO
 * SO THAT wmask BELOW IS ALL ONES
 */
typedef	long word;		/* "word" used for optimal copy speed */

#define	wsize	sizeof(word)
#define	wmask	(wsize - 1)

/*
 * Copy a block of memory, handling overlap.
 * This is the routine that actually implements
 * (the portable versions of) bcopy, memcpy, and memmove.
 */
#if defined(MEMCOPY)
void *
memcpy(void *dst0, const void *src0, size_t length)
#elif defined(MEMMOVE)
void *
memmove(void *dst0, const void *src0, size_t length)
#else
void
bcopy(const void *src0, void *dst0, size_t length)
#endif
{
	char *dst = dst0;
	const char *src = src0;
	size_t t;
	unsigned long u;

	if (length == 0 || dst == src)		/* nothing to do */
		goto done;

	/*
	 * Macros: loop-t-times; and loop-t-times, t>0
	 */
#define	TLOOP(s) if (t) TLOOP1(s)
#define	TLOOP1(s) do { s; } while (--t)

	if ((unsigned long)dst < (unsigned long)src) {
		/*
		 * Copy forward.
		 */
		u = (unsigned long)src;	/* only need low bits */
		if ((u | (unsigned long)dst) & wmask) {
			/*
			 * Try to align operands.  This cannot be done
			 * unless the low bits match.
			 */
			if ((u ^ (unsigned long)dst) & wmask || length < wsize)
				t = length;
			else
				t = wsize - (size_t)(u & wmask);
			length -= t;
			TLOOP1(*dst++ = *src++);
		}
		/*
		 * Copy whole words, then mop up any trailing bytes.
		 */
		t = length / wsize;
		TLOOP(*(word *)(void *)dst = *(const word *)(const void *)src; src += wsize; dst += wsize);
		t = length & wmask;
		TLOOP(*dst++ = *src++);
	} else {
		/*
		 * Copy backwards.  Otherwise essentially the same.
		 * Alignment works as before, except that it takes
		 * (t&wmask) bytes to align, not wsize-(t&wmask).
		 */
		src += length;
		dst += length;
		_DIAGASSERT((unsigned long)dst >= (unsigned long)dst0);
		_DIAGASSERT((unsigned long)src >= (unsigned long)src0);
		u = (unsigned long)src;
		if ((u | (unsigned long)dst) & wmask) {
			if ((u ^ (unsigned long)dst) & wmask || length <= wsize)
				t = length;
			else
				t = (size_t)(u & wmask);
			length -= t;
			TLOOP1(*--dst = *--src);
		}
		t = length / wsize;
		TLOOP(src -= wsize; dst -= wsize; *(word *)(void *)dst = *(const word *)(const void *)src);
		t = length & wmask;
		TLOOP(*--dst = *--src);
	}
done:
#if defined(MEMCOPY) || defined(MEMMOVE)
	return (dst0);
#else
	return;
#endif
}
#else /* __OPTIMIZE_SIZE__ */
#if defined(MEMCOPY)
/*
 * This is designed to be small, not fast.
 */
void *
memcpy(void *s1, const void *s2, size_t n)
{
	const char *f = s2;
	char *t = s1;

	while (n-- > 0)
		*t++ = *f++;
	return s1;
}
#elif defined(MEMMOVE)
/*
 * This is designed to be small, not fast.
 */
void *
memmove(void *s1, const void *s2, size_t n)
{
	const char *f = s2;
	char *t = s1;

	if (f < t) {
		f += n;
		t += n;
		while (n-- > 0)
			*--t = *--f;
	} else {
		while (n-- > 0)
			*t++ = *f++;
	}
	return s1;
}
#else
/*
 * This is designed to be small, not fast.
 */
void
bcopy(const void *s2, void *s1, size_t n)
{
	const char *f = s2;
	char *t = s1;

	while (n-- > 0)
		*t++ = *f++;
}
#endif
#endif /* __OPTIMIZE_SIZE__ */