newlib/newlib/libc/posix/telldir.c

#ifndef HAVE_OPENDIR

/*
 * Copyright (c) 1983 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.
 * 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)telldir.c	5.9 (Berkeley) 2/23/91";
#endif /* LIBC_SCCS and not lint */

#include <sys/param.h>
#include <dirent.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/lock.h>

/*
 * The option SINGLEUSE may be defined to say that a telldir
 * cookie may be used only once before it is freed. This option
 * is used to avoid having memory usage grow without bound.
 */
#define SINGLEUSE

/*
 * One of these structures is malloced to describe the current directory
 * position each time telldir is called. It records the current magic 
 * cookie returned by getdirentries and the offset within the buffer
 * associated with that return value.
 */
struct ddloc {
	struct	ddloc *loc_next;/* next structure in list */
	long	loc_index;	/* key associated with structure */
	long	loc_seek;	/* magic cookie returned by getdirentries */
	long	loc_loc;	/* offset of entry in buffer */
	DIR    *loc_dirp;       /* DIR pointer */
};

#define	NDIRHASH	32	/* Num of hash lists, must be a power of 2 */
#define	LOCHASH(i)	((i)&(NDIRHASH-1))

static long	dd_loccnt = 1;	/* Index of entry for sequential readdir's */
static struct	ddloc *dd_hash[NDIRHASH];   /* Hash list heads for ddlocs */

#if !defined(__SINGLE_THREAD__) && defined(HAVE_DD_LOCK)
__LOCK_INIT(static, __dd_hash_mutex);
#endif

/*
 * return a pointer into a directory
 */

#if !defined(_ELIX_LEVEL) || (_ELIX_LEVEL >= 2)

long
telldir (DIR *dirp)
{
	register int index;
	register struct ddloc *lp;

	if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL)
		return (-1);

#ifdef HAVE_DD_LOCK
	__lock_acquire_recursive(dirp->dd_lock);
#ifndef __SINGLE_THREAD__
	__lock_acquire(__dd_hash_mutex);
#endif
#endif
	index = dd_loccnt++;
	lp->loc_index = index;
	lp->loc_seek = dirp->dd_seek;
	lp->loc_loc = dirp->dd_loc;
	lp->loc_dirp = dirp;
	lp->loc_next = dd_hash[LOCHASH(index)];
	dd_hash[LOCHASH(index)] = lp;
#ifdef HAVE_DD_LOCK
#ifndef __SINGLE_THREAD__
	__lock_release(__dd_hash_mutex);
#endif
	__lock_release_recursive(dirp->dd_lock);
#endif
	return (index);
}

#endif /* !_ELIX_LEVEL || _ELIX_LEVEL >= 2 */

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

#if !defined(__SINGLE_THREAD__) && defined(HAVE_DD_LOCK)
	__lock_acquire(__dd_hash_mutex);
#endif
	if (loc != 0) {
		prevlp = &dd_hash[LOCHASH(loc)];
		lp = *prevlp;
		while (lp != NULL) {
			if (lp->loc_index == loc)
				break;
			prevlp = &lp->loc_next;
			lp = lp->loc_next;
		}
		if (lp == NULL) {
#if !defined(__SINGLE_THREAD__) && defined(HAVE_DD_LOCK)
			__lock_release(__dd_hash_mutex);
#endif
			return;
		}
		if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)
			goto found;
		(void) lseek(dirp->dd_fd, lp->loc_seek, 0);
		dirp->dd_seek = lp->loc_seek;
		dirp->dd_loc = 0;
		while (dirp->dd_loc < lp->loc_loc) {
			dp = readdir(dirp);
			if (dp == NULL)
				break;
		}
found:
#ifdef SINGLEUSE
		*prevlp = lp->loc_next;
		free((caddr_t)lp);
#endif
	} else {
		// loc 0 means rewinding
		(void) lseek(dirp->dd_fd, 0, 0);
		dirp->dd_seek = 0;
		dirp->dd_loc = 0;
	}
#if !defined(__SINGLE_THREAD__) && defined(HAVE_DD_LOCK)
	__lock_release(__dd_hash_mutex);
#endif
}

/* clean out any hash entries from a closed directory */
void
_cleanupdir (register DIR *dirp)
{
	int i;

#if !defined(__SINGLE_THREAD__) && defined(HAVE_DD_LOCK)
	__lock_acquire(__dd_hash_mutex);
#endif
	for (i = 0; i < NDIRHASH; ++i) {
		struct ddloc head;
		register struct ddloc *lp;
		register struct ddloc *prevlp;

		lp = dd_hash[i];
		head.loc_next = lp;
		prevlp = &head;
		while (lp != NULL) {
			struct ddloc *nextlp;

			nextlp = lp->loc_next;
			if (lp->loc_dirp == dirp) {
				prevlp->loc_next = nextlp;
				free((caddr_t)lp);
			}
			else
				prevlp = lp;
			lp = nextlp;
		}
		dd_hash[i] = head.loc_next;
	}
#if !defined(__SINGLE_THREAD__) && defined(HAVE_DD_LOCK)
	__lock_release(__dd_hash_mutex);
#endif

}
#endif /* ! HAVE_OPENDIR */