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      1 /*	$NetBSD: telldir.c,v 1.20 2013/03/06 11:27:28 yamt Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1983, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. Neither the name of the University nor the names of its contributors
     16  *    may be used to endorse or promote products derived from this software
     17  *    without specific prior written permission.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     29  * SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 #if 0
     35 static char sccsid[] = "@(#)telldir.c	8.1 (Berkeley) 6/4/93";
     36 #else
     37 __RCSID("$NetBSD: telldir.c,v 1.20 2013/03/06 11:27:28 yamt Exp $");
     38 #endif
     39 #endif /* LIBC_SCCS and not lint */
     40 
     41 #include "namespace.h"
     42 #include "reentrant.h"
     43 #include "extern.h"
     44 #include <sys/param.h>
     45 
     46 #include <assert.h>
     47 #include <dirent.h>
     48 #include <stdlib.h>
     49 #include <unistd.h>
     50 
     51 #include "dirent_private.h"
     52 
     53 #ifdef __weak_alias
     54 __weak_alias(telldir,_telldir)
     55 #endif
     56 
     57 long
     58 telldir(DIR *dirp)
     59 {
     60 	long rv;
     61 #ifdef _REENTRANT
     62 	if (__isthreaded) {
     63 		mutex_lock((mutex_t *)dirp->dd_lock);
     64 		rv = _telldir_unlocked(dirp);
     65 		mutex_unlock((mutex_t *)dirp->dd_lock);
     66 	} else
     67 #endif
     68 		rv = _telldir_unlocked(dirp);
     69 	return rv;
     70 }
     71 
     72 /*
     73  * return a pointer into a directory
     74  */
     75 long
     76 _telldir_unlocked(DIR *dirp)
     77 {
     78 	struct dirpos *lp;
     79 
     80 	for (lp = dirp->dd_internal; lp; lp = lp->dp_next)
     81 		if (lp->dp_seek == dirp->dd_seek &&
     82 		    lp->dp_loc == dirp->dd_loc)
     83 			return (intptr_t)lp;
     84 
     85 	if ((lp = malloc(sizeof(*lp))) == NULL)
     86 		return (-1);
     87 
     88 	lp->dp_seek = dirp->dd_seek;
     89 	lp->dp_loc = dirp->dd_loc;
     90 	lp->dp_next = dirp->dd_internal;
     91 	dirp->dd_internal = lp;
     92 
     93 	return (intptr_t)lp;
     94 }
     95 
     96 /*
     97  * seek to an entry in a directory.
     98  * Only values returned by "telldir" should be passed to seekdir.
     99  */
    100 void
    101 _seekdir_unlocked(DIR *dirp, long loc)
    102 {
    103 	struct dirpos *lp;
    104 
    105 	_DIAGASSERT(dirp != NULL);
    106 
    107 	for (lp = dirp->dd_internal; lp; lp = lp->dp_next)
    108 		if ((intptr_t)lp == loc)
    109 			break;
    110 
    111 	if (lp == NULL)
    112 		return;
    113 
    114 	if (lp->dp_loc == dirp->dd_loc && lp->dp_seek == dirp->dd_seek)
    115 		return;
    116 
    117 	dirp->dd_seek = lseek(dirp->dd_fd, lp->dp_seek, SEEK_SET);
    118 	dirp->dd_loc = 0;
    119 	while (dirp->dd_loc < lp->dp_loc)
    120 		if (_readdir_unlocked(dirp, 0) == NULL)
    121 			break;
    122 }
    123