sysdeps/unix/readdir_r.c

   1 /* Copyright (C) 1991,92,93,94,95,96,97,98,99,2000,02,10
   2         Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <limits.h>
  21 #include <stddef.h>
  22 #include <string.h>
  23 #include <dirent.h>
  24 #include <unistd.h>
  25 #include <sys/types.h>
  26 #include <assert.h>
  27
  28 #include <dirstream.h>
  29
  30 #ifndef __READDIR_R
  31 # define __READDIR_R __readdir_r
  32 # define __GETDENTS __getdents
  33 # define DIRENT_TYPE struct dirent
  34 # define __READDIR_R_ALIAS
  35 #endif
  36
  37 /* Read a directory entry from DIRP.  */
  38 int
  39 __READDIR_R (DIR *dirp, DIRENT_TYPE *entry, DIRENT_TYPE **result)
  40 {
  41   DIRENT_TYPE *dp;
  42   size_t reclen;
  43   const int saved_errno = errno;
  44
  45   __libc_lock_lock (dirp->lock);
  46
  47   do
  48     {
  49       if (dirp->offset >= dirp->size)
  50         {
  51           /* We've emptied out our buffer.  Refill it.  */
  52
  53           size_t maxread;
  54           ssize_t bytes;
  55
  56 #ifndef _DIRENT_HAVE_D_RECLEN
  57           /* Fixed-size struct; must read one at a time (see below).  */
  58           maxread = sizeof *dp;
  59 #else
  60           maxread = dirp->allocation;
  61 #endif
  62
  63           bytes = __GETDENTS (dirp->fd, dirp->data, maxread);
  64           if (bytes <= 0)
  65             {
  66               /* On some systems getdents fails with ENOENT when the
  67                  open directory has been rmdir'd already.  POSIX.1
  68                  requires that we treat this condition like normal EOF.  */
  69               if (bytes < 0 && errno == ENOENT)
  70                 {
  71                   bytes = 0;
  72                   __set_errno (saved_errno);
  73                 }
  74
  75               dp = NULL;
  76               /* Reclen != 0 signals that an error occurred.  */
  77               reclen = bytes != 0;
  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 just 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     }
 112   while (dp->d_ino == 0);
 113
 114   if (dp != NULL)
 115     {
 116 #ifdef GETDENTS_64BIT_ALIGNED
 117       /* The d_reclen value might include padding which is not part of
 118          the DIRENT_TYPE data structure.  */
 119       reclen = MIN (reclen,
 120                     offsetof (DIRENT_TYPE, d_name) + sizeof (dp->d_name));
 121 #endif
 122       *result = memcpy (entry, dp, reclen);
 123 #ifdef GETDENTS_64BIT_ALIGNED
 124       entry->d_reclen = reclen;
 125 #endif
 126     }
 127   else
 128     *result = NULL;
 129
 130   __libc_lock_unlock (dirp->lock);
 131
 132   return dp != NULL ? 0 : reclen ? errno : 0;
 133 }
 134
 135 #ifdef __READDIR_R_ALIAS
 136 weak_alias (__readdir_r, readdir_r)
 137 #endif