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      1 /*	$NetBSD: readdir.c,v 1.27 2024/09/10 17:11:19 riastradh 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[] = "@(#)readdir.c	8.3 (Berkeley) 9/29/94";
     36 #else
     37 __RCSID("$NetBSD: readdir.c,v 1.27 2024/09/10 17:11:19 riastradh 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 <dirent.h>
     47 #include <errno.h>
     48 #include <string.h>
     49 #include <unistd.h>
     50 
     51 #include "dirent_private.h"
     52 
     53 /*
     54  * get next entry in a directory.
     55  */
     56 struct dirent *
     57 _readdir_unlocked(DIR *dirp, int skipdeleted)
     58 {
     59 	const int saved_errno = errno;
     60 	struct dirent *dp;
     61 
     62 	for (;;) {
     63 		if (dirp->dd_loc >= dirp->dd_size) {
     64 			if (dirp->dd_flags & __DTF_READALL)
     65 				break;
     66 			dirp->dd_loc = 0;
     67 		}
     68 		if (dirp->dd_loc == 0 && !(dirp->dd_flags & __DTF_READALL)) {
     69 			dirp->dd_seek = lseek(dirp->dd_fd, (off_t)0, SEEK_CUR);
     70 			dirp->dd_size = getdents(dirp->dd_fd,
     71 			    dirp->dd_buf, (size_t)dirp->dd_len);
     72 			if (dirp->dd_size == 0) /* end of directory */
     73 				break;
     74 			if (dirp->dd_size == -1) /* getdents sets errno */
     75 				return NULL;
     76 			if (dirp->dd_size < 0) { /* paranoia */
     77 				errno = EIO;
     78 				return NULL;
     79 			}
     80 		}
     81 		dp = (struct dirent *)
     82 		    (void *)(dirp->dd_buf + (size_t)dirp->dd_loc);
     83 		/* bogus pointer check */
     84 		if ((intptr_t)dp & _DIRENT_ALIGN(dp)) {
     85 			errno = EIO;
     86 			return NULL;
     87 		}
     88 		/* d_reclen is unsigned; no need to compare it <= 0 */
     89 		if (dp->d_reclen > dirp->dd_len + 1 - dirp->dd_loc) {
     90 			errno = EIO;
     91 			return NULL;
     92 		}
     93 		dirp->dd_loc += dp->d_reclen;
     94 		if (dp->d_ino == 0 && skipdeleted)
     95 			continue;
     96 		if (dp->d_type == DT_WHT && (dirp->dd_flags & DTF_HIDEW))
     97 			continue;
     98 		return dp;
     99 	}
    100 
    101 	errno = saved_errno;
    102 	return NULL;
    103 }
    104 
    105 struct dirent *
    106 readdir(DIR *dirp)
    107 {
    108 	struct dirent	*dp;
    109 
    110 #ifdef _REENTRANT
    111 	if (__isthreaded) {
    112 		mutex_lock((mutex_t *)dirp->dd_lock);
    113 		dp = _readdir_unlocked(dirp, 1);
    114 		mutex_unlock((mutex_t *)dirp->dd_lock);
    115 	}
    116 	else
    117 #endif
    118 		dp = _readdir_unlocked(dirp, 1);
    119 	return (dp);
    120 }
    121 
    122 int
    123 readdir_r(DIR *dirp, struct dirent *entry, struct dirent **result)
    124 {
    125 	struct dirent *dp;
    126 	int saved_errno;
    127 
    128 	saved_errno = errno;
    129 	errno = 0;
    130 #ifdef _REENTRANT
    131 	if (__isthreaded) {
    132 		mutex_lock((mutex_t *)dirp->dd_lock);
    133 		if ((dp = _readdir_unlocked(dirp, 1)) != NULL)
    134 			memcpy(entry, dp, (size_t)_DIRENT_SIZE(dp));
    135 		mutex_unlock((mutex_t *)dirp->dd_lock);
    136 	}
    137 	else
    138 #endif
    139 		if ((dp = _readdir_unlocked(dirp, 1)) != NULL)
    140 			memcpy(entry, dp, (size_t)_DIRENT_SIZE(dp));
    141 
    142 	if (errno != 0) {
    143 		if (dp == NULL)
    144 			return (errno);
    145 	} else
    146 		errno = saved_errno;
    147 
    148 	if (dp != NULL)
    149 		*result = entry;
    150 	else
    151 		*result = NULL;
    152 
    153 	return (0);
    154 }
    155