movebytes.c

刻录光盘的程序

/* @(#)movebytes.c	1.10 98/02/15 Copyright 1985 J. Schilling */
/*
 *	move data
 *
 *	Copyright (c) 1985 J. Schilling
 */
/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING.  If not, write to
 * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <standard.h>
#include <align.h>

#define	DO8(a)	a;a;a;a;a;a;a;a;

char *movebytes(fromv, tov, cnt)
	const void	*fromv;
	void		*tov;
	int		cnt;
{
	register const char	*from	= fromv;
	register char		*to	= tov;
	register int		n;

	if ((n = cnt) == 0)
		return (to);

	if (from >= to) {
		/*
		 * source is on higher adresses than destination:
		 *	move bytes forwards
		 */
		if (n >= 8 * sizeof(long)) {
			if (l2aligned(from, to)) {
				register const long *froml = (const long *)from;
				register long *tol = (long *)to;
				register int rem = n % (8 * sizeof (long));
			
				n /= (8 * sizeof (long));
				do {
					DO8 (*tol++ = *froml++);
				} while (--n > 0);

				from = (const char *)froml;
				to = (char *)tol;
				n = rem;
			}

			if (n >= 8) {
				n -= 8;
				do {
					DO8 (*to++ = *from++);
				} while ((n -= 8) >= 0);
				n += 8;
			}

			if (n > 0) do {
				*to++ = *from++;
			} while (--n > 0);
			return (to);
		}
		if (n > 0) do {
			*to++ = *from++;
		} while (--n > 0);
		return (to);
	} else {
		char *ep;

		/*
		 * source is on lower adresses than destination:
		 *	move bytes backwards
		 */
		to += n;
		from += n;
		ep = to;
		if (n >= 8 * sizeof(long)) {
			if (l2aligned(from, to)) {
				register const long *froml = (const long *)from;
				register long *tol = (long *)to;
				register int rem = n % (8 * sizeof (long));

				n /= (8 * sizeof (long));
				do {
					DO8 (*--tol = *--froml);
				} while (--n > 0);

				from = (const char *)froml;
				to = (char *)tol;
				n = rem;
			}
			if (n >= 8) {
				n -= 8;
				do {
					DO8 (*--to = *--from);
				} while ((n -= 8) >= 0);
				n += 8;
			}
			if (n > 0) do {
				*--to = *--from;
			} while (--n > 0);
			return (ep);
		}
		if (n > 0) do {
			*--to = *--from;
		} while (--n > 0);
		return (ep);
	}
}