sysdeps/posix/readdir_r.c

   1 /* Copyright (C) 1991-2013 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_R
  30 # define __READDIR_R __readdir_r
  31 # define __GETDENTS __getdents
  32 # define DIRENT_TYPE struct dirent
  33 # define __READDIR_R_ALIAS
  34 #endif
  35
  36 /* Read a directory entry from DIRP.  */
  37 int
  38 __READDIR_R (DIR *dirp, DIRENT_TYPE *entry, DIRENT_TYPE **result)
  39 {
  40   DIRENT_TYPE *dp;
  41   size_t reclen;
  42   const int saved_errno = errno;
  43
  44   __libc_lock_lock (dirp->lock);
  45
  46   do
  47     {
  48       if (dirp->offset >= dirp->size)
  49         {
  50           /* We've emptied out our buffer.  Refill it.  */
  51
  52           size_t maxread;
  53           ssize_t bytes;
  54
  55 #ifndef _DIRENT_HAVE_D_RECLEN
  56           /* Fixed-size struct; must read one at a time (see below).  */
  57           maxread = sizeof *dp;
  58 #else
  59           maxread = dirp->allocation;
  60 #endif
  61
  62           bytes = __GETDENTS (dirp->fd, dirp->data, maxread);
  63           if (bytes <= 0)
  64             {
  65               /* On some systems getdents fails with ENOENT when the
  66                  open directory has been rmdir'd already.  POSIX.1
  67                  requires that we treat this condition like normal EOF.  */
  68               if (bytes < 0 && errno == ENOENT)
  69                 {
  70                   bytes = 0;
  71                   __set_errno (saved_errno);
  72                 }
  73
  74               dp = NULL;
  75               /* Reclen != 0 signals that an error occurred.  */
  76               reclen = bytes != 0;
  77               break;
  78             }
  79           dirp->size = (size_t) bytes;
  80
  81           /* Reset the offset into the buffer.  */
  82           dirp->offset = 0;
  83         }
  84
  85       dp = (DIRENT_TYPE *) &dirp->data[dirp->offset];
  86
  87 #ifdef _DIRENT_HAVE_D_RECLEN
  88       reclen = dp->d_reclen;
  89 #else
  90       /* The only version of `struct dirent*' that lacks `d_reclen'
  91          is fixed-size.  */
  92       assert (sizeof dp->d_name > 1);
  93       reclen = sizeof *dp;
  94       /* The name is not terminated if it is the largest possible size.
  95          Clobber the following byte to ensure proper null termination.  We
  96          read just one entry at a time above so we know that byte will not
  97          be used later.  */
  98       dp->d_name[sizeof dp->d_name] = '\0';
  99 #endif
 100
 101       dirp->offset += reclen;
 102
 103 #ifdef _DIRENT_HAVE_D_OFF
 104       dirp->filepos = dp->d_off;
 105 #else
 106       dirp->filepos += reclen;
 107 #endif
 108
 109       /* Skip deleted files.  */
 110     }
 111   while (dp->d_ino == 0);
 112
 113   if (dp != NULL)
 114     {
 115 #ifdef GETDENTS_64BIT_ALIGNED
 116       /* The d_reclen value might include padding which is not part of
 117          the DIRENT_TYPE data structure.  */
 118       reclen = MIN (reclen,
 119                     offsetof (DIRENT_TYPE, d_name) + sizeof (dp->d_name));
 120 #endif
 121       *result = memcpy (entry, dp, reclen);
 122 #ifdef GETDENTS_64BIT_ALIGNED
 123       entry->d_reclen = reclen;
 124 #endif
 125     }
 126   else
 127     *result = NULL;
 128
 129   __libc_lock_unlock (dirp->lock);
 130
 131   return dp != NULL ? 0 : reclen ? errno : 0;
 132 }
 133
 134 #ifdef __READDIR_R_ALIAS
 135 weak_alias (__readdir_r, readdir_r)
 136 #endif