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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <errno.h>
  21 #include <limits.h>
  22 #include <stddef.h>
  23 #include <string.h>
  24 #include <dirent.h>
  25 #include <unistd.h>
  26 #include <sys/types.h>
  27 #include <assert.h>
  28
  29 #include <dirstream.h>
  30
  31 #ifndef __READDIR_R
  32 # define __READDIR_R __readdir_r
  33 # define __GETDENTS __getdents
  34 # define DIRENT_TYPE struct dirent
  35 # define __READDIR_R_ALIAS
  36 #endif
  37
  38 /* Read a directory entry from DIRP.  */
  39 int
  40 __READDIR_R (DIR *dirp, DIRENT_TYPE *entry, DIRENT_TYPE **result)
  41 {
  42   DIRENT_TYPE *dp;
  43   size_t reclen;
  44   const int saved_errno = errno;
  45
  46   __libc_lock_lock (dirp->lock);
  47
  48   do
  49     {
  50       if (dirp->offset >= dirp->size)
  51         {
  52           /* We've emptied out our buffer.  Refill it.  */
  53
  54           size_t maxread;
  55           ssize_t bytes;
  56
  57 #ifndef _DIRENT_HAVE_D_RECLEN
  58           /* Fixed-size struct; must read one at a time (see below).  */
  59           maxread = sizeof *dp;
  60 #else
  61           maxread = dirp->allocation;
  62 #endif
  63
  64           bytes = __GETDENTS (dirp->fd, dirp->data, maxread);
  65           if (bytes <= 0)
  66             {
  67               /* On some systems getdents fails with ENOENT when the
  68                  open directory has been rmdir'd already.  POSIX.1
  69                  requires that we treat this condition like normal EOF.  */
  70               if (bytes < 0 && errno == ENOENT)
  71                 {
  72                   bytes = 0;
  73                   __set_errno (saved_errno);
  74                 }
  75
  76               dp = NULL;
  77               /* Reclen != 0 signals that an error occurred.  */
  78               reclen = bytes != 0;
  79               break;
  80             }
  81           dirp->size = (size_t) bytes;
  82
  83           /* Reset the offset into the buffer.  */
  84           dirp->offset = 0;
  85         }
  86
  87       dp = (DIRENT_TYPE *) &dirp->data[dirp->offset];
  88
  89 #ifdef _DIRENT_HAVE_D_RECLEN
  90       reclen = dp->d_reclen;
  91 #else
  92       /* The only version of `struct dirent*' that lacks `d_reclen'
  93          is fixed-size.  */
  94       assert (sizeof dp->d_name > 1);
  95       reclen = sizeof *dp;
  96       /* The name is not terminated if it is the largest possible size.
  97          Clobber the following byte to ensure proper null termination.  We
  98          read just one entry at a time above so we know that byte will not
  99          be used later.  */
 100       dp->d_name[sizeof dp->d_name] = '\0';
 101 #endif
 102
 103       dirp->offset += reclen;
 104
 105 #ifdef _DIRENT_HAVE_D_OFF
 106       dirp->filepos = dp->d_off;
 107 #else
 108       dirp->filepos += reclen;
 109 #endif
 110
 111       /* Skip deleted files.  */
 112     }
 113   while (dp->d_ino == 0);
 114
 115   if (dp != NULL)
 116     {
 117 #ifdef GETDENTS_64BIT_ALIGNED
 118       /* The d_reclen value might include padding which is not part of
 119          the DIRENT_TYPE data structure.  */
 120       reclen = MIN (reclen, sizeof (DIRENT_TYPE));
 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