sysdeps/mach/hurd/readdir.c

   1 /* Copyright (C) 1993,94,95,96,97,2002 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <errno.h>
  20 #include <stddef.h>
  21 #include <dirent.h>
  22 #include <unistd.h>
  23 #include <endian.h>
  24 #include <assert.h>
  25
  26 /* Read a directory entry from DIRP.  */
  27 struct dirent *
  28 __readdir (DIR *dirp)
  29 {
  30   struct dirent64 *entry64 = __readdir64 (dirp);
  31
  32   if (sizeof (struct dirent64) == sizeof (struct dirent))
  33     /* We should in fact just be an alias to readdir64 on this machine.  */
  34     return (struct dirent *) entry64;
  35
  36   /* These are all compile-time constants.  We know that d_ino is the first
  37      member and that the layout of the following members matches exactly in
  38      both structures.  */
  39   assert (offsetof (struct dirent, d_ino) == 0);
  40   assert (offsetof (struct dirent64, d_ino) == 0);
  41 # define MATCH(memb)                                                          \
  42   assert (offsetof (struct dirent64, memb) - sizeof (entry64->d_ino)          \
  43           == offsetof (struct dirent, memb) - sizeof (ino_t))
  44   MATCH (d_reclen);
  45   MATCH (d_type);
  46   MATCH (d_namlen);
  47 # undef MATCH
  48
  49   if (entry64 == NULL)
  50     return NULL;
  51
  52   struct dirent *const entry = ((void *) (&entry64->d_ino + 1)
  53                                 - sizeof entry->d_ino);
  54   const ino_t d_ino = entry64->d_ino;
  55   if (d_ino != entry64->d_ino)
  56     {
  57       __set_errno (EOVERFLOW);
  58       return NULL;
  59     }
  60 # if BYTE_ORDER != BIG_ENDIAN   /* We just skipped over the zero high word.  */
  61   entry->d_ino = d_ino; /* ... or the nonzero low word, swap it.  */
  62 # endif
  63   entry->d_reclen -= sizeof entry64->d_ino - sizeof entry->d_ino;
  64   return entry;
  65 }
  66
  67 weak_alias (__readdir, readdir)