lib/libc/gen/opendir.c

   1 /*
   2  * Copyright (c) 1983, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * $FreeBSD: src/lib/libc/gen/opendir.c,v 1.10.2.1 2001/06/04 20:59:48 joerg Exp $
  30  *
  31  * @(#)opendir.c        8.8 (Berkeley) 5/1/95
  32  */
  33
  34 #include "namespace.h"
  35 #include <sys/param.h>
  36 #include <sys/stat.h>
  37
  38 #include <dirent.h>
  39 #include <errno.h>
  40 #include <fcntl.h>
  41 #include <stdlib.h>
  42 #include <string.h>
  43 #include <unistd.h>
  44 #include "un-namespace.h"
  45
  46 #include "gen_private.h"
  47
  48 #define DEFAULT_FLAGS (DTF_HIDEW | DTF_NODUP)
  49
  50 /*
  51  * Open a directory given its path.
  52  */
  53 DIR *
  54 opendir(const char *name)
  55 {
  56         return (__opendir2(name, DEFAULT_FLAGS));
  57 }
  58
  59 /*
  60  * Open a directory given a descriptor representing it.
  61  */
  62 DIR *
  63 fdopendir(int fd)
  64 {
  65         return (__fdopendir2(fd, DEFAULT_FLAGS));
  66 }
  67
  68 DIR *
  69 __opendir2(const char *name, int flags)
  70 {
  71         int fd;
  72         struct stat statb;
  73         DIR *dirp;
  74         int saved_errno;
  75
  76         /*
  77          * stat() before _open() because opening of special files may be
  78          * harmful.
  79          */
  80         if (stat(name, &statb) != 0)
  81                 return (NULL);
  82
  83         fd = _open(name, O_RDONLY | O_NONBLOCK | O_DIRECTORY | O_CLOEXEC);
  84         if (fd == -1)
  85                 return (NULL);
  86         dirp = __fdopendir2(fd, flags);
  87         if (dirp == NULL) {
  88                 saved_errno = errno;
  89                 _close(fd);
  90                 errno = saved_errno;
  91         }
  92
  93         return (dirp);
  94 }
  95
  96 DIR *
  97 __fdopendir2(int fd, int flags)
  98 {
  99         DIR *dirp;
 100         int incr;
 101         int saved_errno;
 102         struct stat statb;
 103
 104         dirp = NULL;
 105
 106         if (_fstat(fd, &statb) != 0)
 107                 goto fail;
 108         if (!S_ISDIR(statb.st_mode)) {
 109                 errno = ENOTDIR;
 110                 goto fail;
 111         }
 112         if (_fcntl(fd, F_SETFD, FD_CLOEXEC) == -1 ||
 113             (dirp = malloc(sizeof(DIR))) == NULL)
 114                 goto fail;
 115
 116         /*
 117          * Use the system page size if that is a multiple of DIRBLKSIZ.
 118          * Hopefully this can be a big win someday by allowing page
 119          * trades to user space to be done by _getdirentries().
 120          */
 121         incr = getpagesize();
 122         if ((incr % DIRBLKSIZ) != 0)
 123                 incr = DIRBLKSIZ;
 124
 125         dirp->dd_len = incr;
 126         dirp->dd_buf = malloc(dirp->dd_len);
 127         if (dirp->dd_buf == NULL)
 128                 goto fail;
 129         flags &= ~DTF_REWIND;
 130
 131         dirp->dd_loc = 0;
 132         dirp->dd_fd = fd;
 133         dirp->dd_flags = flags;
 134         dirp->dd_lock = NULL;
 135
 136         /*
 137          * Set up seek point for rewinddir.
 138          */
 139         dirp->dd_seek = 0;
 140         dirp->dd_rewind = telldir(dirp);
 141
 142         /*
 143          * The file offset of the fd passed to fdopendir() determines the
 144          * initial entry returned by readdir().  Save this offset so that
 145          * telldir() right after fdopendir() returns a value pointing to this
 146          * initial entry.
 147          * We don't have to worry about misaligned file offsets.  The kernel
 148          * deals with these.
 149          */
 150         if ((dirp->dd_seek = lseek(fd, 0, SEEK_CUR)) < 0)
 151                 goto fail;
 152
 153         return (dirp);
 154
 155 fail:
 156         saved_errno = errno;
 157         if (dirp != NULL) {
 158                 _reclaim_telldir(dirp);
 159                 free(dirp->dd_buf);
 160         }
 161         free(dirp);
 162         errno = saved_errno;
 163         return (NULL);
 164 }