pushpull.c

这是著名的jffs2嵌入式日志文件系统的源代码

/*
 * JFFS2 -- Journalling Flash File System, Version 2.
 *
 * Copyright (C) 2001 Red Hat, Inc.
 *
 * Created by David Woodhouse <[e-mail]>
 *
 * The original JFFS, from which the design for JFFS2 was derived,
 * was designed and implemented by Axis Communications AB.
 *
 * The contents of this file are subject to the Red Hat eCos Public
 * License Version 1.1 (the "Licence"); you may not use this file
 * except in compliance with the Licence.  You may obtain a copy of
 * the Licence at http://www.redhat.com/
 *
 * Software distributed under the Licence is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing rights and
 * limitations under the Licence.
 *
 * The Original Code is JFFS2 - Journalling Flash File System, version 2
 *
 * Alternatively, the contents of this file may be used under the
 * terms of the GNU General Public License version 2 (the "GPL"), in
 * which case the provisions of the GPL are applicable instead of the
 * above.  If you wish to allow the use of your version of this file
 * only under the terms of the GPL and not to allow others to use your
 * version of this file under the RHEPL, indicate your decision by
 * deleting the provisions above and replace them with the notice and
 * other provisions required by the GPL.  If you do not delete the
 * provisions above, a recipient may use your version of this file
 * under either the RHEPL or the GPL.
 *
 * $Id: pushpull.c,v 1.7 2001/09/23 10:04:15 rmk Exp $
 *
 */

#include <linux/string.h>
#include "pushpull.h"
#include <linux/errno.h>

void init_pushpull(struct pushpull *pp, char *buf, unsigned buflen, unsigned ofs, unsigned reserve)
{
	pp->buf = buf;
	pp->buflen = buflen;
	pp->ofs = ofs;
	pp->reserve = reserve;
}
     

int pushbit(struct pushpull *pp, int bit, int use_reserved)
{
	if (pp->ofs >= pp->buflen - (use_reserved?0:pp->reserve)) {
		return -ENOSPC;
	}

	if (bit) {
		pp->buf[pp->ofs >> 3] |= (1<<(7-(pp->ofs &7)));
	}
	else {
		pp->buf[pp->ofs >> 3] &= ~(1<<(7-(pp->ofs &7)));
	}
	pp->ofs++;

	return 0;
}

int pushedbits(struct pushpull *pp)
{
	return pp->ofs;
}