xref: /freebsd-10.3-release/lib/libc/gen/telldir.c

/*
 * Copyright (c) 1983, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * 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.
 * 4. 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)telldir.c	8.1 (Berkeley) 6/4/93";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: releng/10.3/lib/libc/gen/telldir.c 282979 2015-05-15 15:49:24Z julian $");

#include "namespace.h"
#include <sys/param.h>
#include <sys/queue.h>
#include <dirent.h>
#include <pthread.h>
#include <stdlib.h>
#include <unistd.h>
#include "un-namespace.h"

#include "libc_private.h"
#include "gen-private.h"
#include "telldir.h"

/*
 * return a pointer into a directory
 */
long
telldir(dirp)
	DIR *dirp;
{
	struct ddloc *lp;
	long idx;

	if (__isthreaded)
		_pthread_mutex_lock(&dirp->dd_lock);
	LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
		if (lp->loc_seek == dirp->dd_seek &&
		    lp->loc_loc == dirp->dd_loc)
			break;
	}
	if (lp == NULL) {
		lp = malloc(sizeof(struct ddloc));
		if (lp == NULL) {
			if (__isthreaded)
				_pthread_mutex_unlock(&dirp->dd_lock);
			return (-1);
		}
		lp->loc_index = dirp->dd_td->td_loccnt++;
		lp->loc_seek = dirp->dd_seek;
		lp->loc_loc = dirp->dd_loc;
		LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe);
	}
	idx = lp->loc_index;
	if (__isthreaded)
		_pthread_mutex_unlock(&dirp->dd_lock);
	return (idx);
}

/*
 * seek to an entry in a directory.
 * Only values returned by "telldir" should be passed to seekdir.
 */
void
_seekdir(dirp, loc)
	DIR *dirp;
	long loc;
{
	struct ddloc *lp;
	struct dirent *dp;

	LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
		if (lp->loc_index == loc)
			break;
	}
	if (lp == NULL)
		return;
	if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)
		return;

	/* If it's within the same chunk of data, don't bother reloading. */
	if (lp->loc_seek == dirp->dd_seek) {
		/*
		 * If we go back to 0 don't make the next readdir
		 * trigger a call to getdirentries().
		 */
		if (lp->loc_loc == 0)
			dirp->dd_flags |= __DTF_SKIPREAD;
		dirp->dd_loc = lp->loc_loc;
		return;
	}
	(void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET);
	dirp->dd_seek = lp->loc_seek;
	dirp->dd_loc = 0;
	dirp->dd_flags &= ~__DTF_SKIPREAD; /* current contents are invalid */
	while (dirp->dd_loc < lp->loc_loc) {
		dp = _readdir_unlocked(dirp, 0);
		if (dp == NULL)
			break;
	}
}

/*
 * After readdir returns the last entry in a block, a call to telldir
 * returns a location that is after the end of that last entry.
 * However, that location doesn't refer to a valid directory entry.
 * Ideally, the call to telldir would return a location that refers to
 * the first entry in the next block.  That location is not known
 * until the next block is read, so readdir calls this function after
 * fetching a new block to fix any such telldir locations.
 */
void
_fixtelldir(DIR *dirp, long oldseek, long oldloc)
{
	struct ddloc *lp;

	lp = LIST_FIRST(&dirp->dd_td->td_locq);
	if (lp != NULL) {
		if (lp->loc_loc == oldloc &&
		    lp->loc_seek == oldseek) {
			lp->loc_seek = dirp->dd_seek;
			lp->loc_loc = dirp->dd_loc;
		}
	}
}

/*
 * Reclaim memory for telldir cookies which weren't used.
 */
void
_reclaim_telldir(dirp)
	DIR *dirp;
{
	struct ddloc *lp;
	struct ddloc *templp;

	lp = LIST_FIRST(&dirp->dd_td->td_locq);
	while (lp != NULL) {
		templp = lp;
		lp = LIST_NEXT(lp, loc_lqe);
		free(templp);
	}
	LIST_INIT(&dirp->dd_td->td_locq);
}