/*	$NetBSD: telldir.c,v 1.20 2013/03/06 11:27:28 yamt Exp $	*/

/*
 * 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.
 * 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.
 */

#include <sys/cdefs.h>

#include "reentrant.h"
#include "extern.h"

#include <sys/param.h>

#include <assert.h>
#include <dirent.h>
#include <stdlib.h>
#include <unistd.h>

#include "dirent_private.h"

long telldir(DIR *dirp) {
  long rv;
#ifdef _REENTRANT
  if (__isthreaded) {
    mutex_lock((mutex_t *)dirp->dd_lock);
    rv = _telldir_unlocked(dirp);
    mutex_unlock((mutex_t *)dirp->dd_lock);
  } else
#endif
    rv = _telldir_unlocked(dirp);
  return rv;
}

/*
 * return a pointer into a directory
 */
long _telldir_unlocked(DIR *dirp) {
  struct dirpos *lp;

  for (lp = dirp->dd_internal; lp; lp = lp->dp_next)
    if (lp->dp_seek == dirp->dd_seek && lp->dp_loc == dirp->dd_loc)
      return (intptr_t)lp;

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

  lp->dp_seek = dirp->dd_seek;
  lp->dp_loc = dirp->dd_loc;
  lp->dp_next = dirp->dd_internal;
  dirp->dd_internal = lp;

  return (intptr_t)lp;
}

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

  _DIAGASSERT(dirp != NULL);

  for (lp = dirp->dd_internal; lp; lp = lp->dp_next)
    if ((intptr_t)lp == loc)
      break;

  if (lp == NULL)
    return;

  if (lp->dp_loc == dirp->dd_loc && lp->dp_seek == dirp->dd_seek)
    return;

  dirp->dd_seek = lseek(dirp->dd_fd, lp->dp_seek, SEEK_SET);
  dirp->dd_loc = 0;
  while (dirp->dd_loc < lp->dp_loc)
    if (_readdir_unlocked(dirp, 0) == NULL)
      break;
}
