rrfile_open.c

一款类linux的操作系统源码

/* 
 *  Roadrunner/pk
 *    Copyright (C) 1989-2001  Cornfed Systems, Inc.
 *
 *  The Roadrunner/pk operating system is free software; you can
 *  redistribute and/or modify it under the terms of the GNU General
 *  Public License, version 2, as published by the Free Software
 *  Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT 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; if not, write to the Free
 *  Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 *  MA 02111-1307 USA
 *
 *  More information about the Roadrunner/pk operating system of
 *  which this file is a part is available on the World-Wide Web
 *  at: http://www.cornfed.com.
 *
 */

#include <errno.h>
#include <fcntl.h>
#include <fs/rrfs.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int
rrfile_open(file_t file)
{
    rrfs_t rrfs = (rrfs_t) file->fs->data;
    rrfile_t rrfile;
    int rrfileno, result;

    mutex_lock(&rrfiletabmutex);

    for (rrfileno = 0;
	 rrfileno < RR_FILES && rrfiletab[rrfileno].flags & RF_INUSE;
	 rrfileno++);
    if (rrfileno == RR_FILES) {
#if _DEBUG
	kprintf("rrfile_open: rrfiletab full\n");
#endif
	mutex_unlock(&rrfiletabmutex);
	return EAGAIN;
    }
    rrfile = (rrfile_t) & (rrfiletab[rrfileno]);
    rrfile->flags |= RF_INUSE;
    mutex_unlock(&rrfiletabmutex);

    file->data = rrfile;
    file->bufsize =
	rrfs->mbr->params.sectorsperclust * rrfs->mbr->params.bytespersector;

    if (file->flags & O_RDONLY) {
	/* Look for an existing file */
	if ((result = rrfs_lookup(file, file->path)) < 0)
	    goto openerror;

	if (file->filesize == 0 && !(file->flags & F_DIR)) {
	    /* 
	     * The file has a directory entry but a zero file length and is
	     * not itself a directory.  Definitely at eof and no need to read
	     * first cluster.
	     */
	    file->flags |= F_EOF;
	    return 0;
	}
	if (rrfile->firstclust >= rrfs->mbr->params.clusters) {
#if _DEBUG
	    kprintf("rrfile_open: read only illegal first cluster\n");
#endif
	    result = EBADCLUST;
	    goto openerror;
	}
	/* Get buffer for first cluster */
	if (file->buf != NULL)
	    brel(file->buf);
	file->buf = bget(file->bufsize);
	blen(file->buf) = file->bufsize;

	/* Read first cluster */
	result = rrfs_readclust(file, rrfile->firstclust, &(file->buf));
	if (result < 0) {
#if _DEBUG
	    kprintf
		("rrfile_open: read first cluster failed (%s)\n",
		 strerror(result));
#endif
	    goto openerror;
	}
	return 0;

    } else if (file->flags & O_WRONLY || file->flags & O_RDWR) {
	file->flags |= F_EOF;

	if ((result = rrfs_lookup(file, file->path)) == 0) {
	    u_long prevclust;

	    if (file->filesize == 0 && !(file->flags & F_DIR)) {
		/* 
		 * The file has a directory entry but a zero file length and
		 * is not itself a directory.  Definitely at eof and no need
		 * to read last cluster.
		 */
		file->pos = 0;
		rrfile->flags |= RF_NEEDCLUST;
		return 0;
	    }
	    /* Scan to the last cluster */
	    for (rrfile->currclust = rrfile->firstclust;;) {
		if (rrfile->currclust >= rrfs->mbr->params.clusters)
		    break;
		prevclust = rrfile->currclust;
		rrfile->currclust =
		    rrfs_nextclust(file->fs, rrfile->currclust);
	    }
	    rrfile->currclust = prevclust;

	    if (rrfile->currclust >= rrfs->mbr->params.clusters) {
#if _DEBUG
		kprintf("rrfile_open: ");
		kprintf("write only or read/write illegal first cluster\n");
#endif
		result = EBADCLUST;
		goto openerror;
	    }
	    if (file->filesize % file->bufsize == 0) {
		/* 
		 * Special case when file size is multiple of the block size.
		 * Don't allocate a buffer and we'll need a cluster the first
		 * time a buffer is written.
		 */
		file->pos = file->filesize;
		rrfile->flags |= RF_NEEDCLUST;
		return 0;
	    }
	    /* Get buffer for last cluster */
	    if (file->buf != NULL)
		brel(file->buf);
	    file->buf = bget(file->bufsize);
	    blen(file->buf) = file->bufsize;

	    /* Read last cluster */
	    result = rrfs_readclust(file, rrfile->currclust, &(file->buf));
	    if (result < 0) {
#if _DEBUG
		kprintf
		    ("rrfile_open: read last cluster failed (%s)\n",
		     strerror(result));
#endif
		goto openerror;
	    }
	    file->pos = file->filesize;
	    bpos(file->buf) = file->filesize % file->bufsize;
	    return 0;

	} else if (file->flags & O_CREAT) {
	    result = rrfile_create(file, (file->flags & O_MKDIR ? 1 : 0));
	    if (result < 0) {
#if _DEBUG
		kprintf
		    ("rrfile_open: file create failed (%s)\n",
		     strerror(result));
#endif
		goto openerror;
	    }
	    rrfile->flags |= RF_NEEDCLUST;
	    file->pos = 0;

	    if (file->flags & O_MKDIR) {
		file->buf = bget(file->bufsize);
		blen(file->buf) = file->bufsize;
		bzero(bstart(file->buf), file->bufsize);
	    }
	    return 0;

	} else {
	    result = ENOENT;
	    goto openerror;
	}
    }
    /* Mode error */
    result = EINVAL;

  openerror:
    mutex_lock(&rrfiletabmutex);
    rrfile_clear(rrfile);
    mutex_unlock(&rrfiletabmutex);
    return result;
}