sysdeps/posix/readdir.c

   1 /* Copyright (C) 1991-2015 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <limits.h>
  20 #include <stddef.h>
  21 #include <string.h>
  22 #include <dirent.h>
  23 #include <unistd.h>
  24 #include <sys/types.h>
  25 #include <assert.h>
  26
  27 #include <dirstream.h>
  28
  29 #ifndef __READDIR
  30 # define __READDIR __readdir
  31 # define __GETDENTS __getdents
  32 # define DIRENT_TYPE struct dirent
  33 # define __READDIR_ALIAS
  34 #endif
  35
  36 /* Read a directory entry from DIRP.  */
  37 DIRENT_TYPE *
  38 __READDIR (DIR *dirp)
  39 {
  40   DIRENT_TYPE *dp;
  41   int saved_errno = errno;
  42
  43 #if IS_IN (libc)
  44   __libc_lock_lock (dirp->lock);
  45 #endif
  46
  47   do
  48     {
  49       size_t reclen;
  50
  51       if (dirp->offset >= dirp->size)
  52         {
  53           /* We've emptied out our buffer.  Refill it.  */
  54
  55           size_t maxread;
  56           ssize_t bytes;
  57
  58 #ifndef _DIRENT_HAVE_D_RECLEN
  59           /* Fixed-size struct; must read one at a time (see below).  */
  60           maxread = sizeof *dp;
  61 #else
  62           maxread = dirp->allocation;
  63 #endif
  64
  65           bytes = __GETDENTS (dirp->fd, dirp->data, maxread);
  66           if (bytes <= 0)
  67             {
  68               /* On some systems getdents fails with ENOENT when the
  69                  open directory has been rmdir'd already.  POSIX.1
  70                  requires that we treat this condition like normal EOF.  */
  71               if (bytes < 0 && errno == ENOENT)
  72                 bytes = 0;
  73
  74               /* Don't modifiy errno when reaching EOF.  */
  75               if (bytes == 0)
  76                 __set_errno (saved_errno);
  77               dp = NULL;
  78               break;
  79             }
  80           dirp->size = (size_t) bytes;
  81
  82           /* Reset the offset into the buffer.  */
  83           dirp->offset = 0;
  84         }
  85
  86       dp = (DIRENT_TYPE *) &dirp->data[dirp->offset];
  87
  88 #ifdef _DIRENT_HAVE_D_RECLEN
  89       reclen = dp->d_reclen;
  90 #else
  91       /* The only version of `struct dirent*' that lacks `d_reclen'
  92          is fixed-size.  */
  93       assert (sizeof dp->d_name > 1);
  94       reclen = sizeof *dp;
  95       /* The name is not terminated if it is the largest possible size.
  96          Clobber the following byte to ensure proper null termination.  We
  97          read jst one entry at a time above so we know that byte will not
  98          be used later.  */
  99       dp->d_name[sizeof dp->d_name] = '\0';
 100 #endif
 101
 102       dirp->offset += reclen;
 103
 104 #ifdef _DIRENT_HAVE_D_OFF
 105       dirp->filepos = dp->d_off;
 106 #else
 107       dirp->filepos += reclen;
 108 #endif
 109
 110       /* Skip deleted files.  */
 111     } while (dp->d_ino == 0);
 112
 113 #if IS_IN (libc)
 114   __libc_lock_unlock (dirp->lock);
 115 #endif
 116
 117   return dp;
 118 }
 119
 120 #ifdef __READDIR_ALIAS
 121 weak_alias (__readdir, readdir)
 122 #endif