sysdeps/mach/hurd/readdir.c

   1 /* Copyright (C) 1993-2014 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 <stddef.h>
  20 #include <dirent.h>
  21 #include <unistd.h>
  22 #include <endian.h>
  23 #include <assert.h>
  24
  25 /* Read a directory entry from DIRP.  */
  26 struct dirent *
  27 __readdir (DIR *dirp)
  28 {
  29   struct dirent64 *entry64 = __readdir64 (dirp);
  30
  31   if (sizeof (struct dirent64) == sizeof (struct dirent))
  32     /* We should in fact just be an alias to readdir64 on this machine.  */
  33     return (struct dirent *) entry64;
  34
  35   /* These are all compile-time constants.  We know that d_ino is the first
  36      member and that the layout of the following members matches exactly in
  37      both structures.  */
  38   assert (offsetof (struct dirent, d_ino) == 0);
  39   assert (offsetof (struct dirent64, d_ino) == 0);
  40 # define MATCH(memb)                                                          \
  41   assert (offsetof (struct dirent64, memb) - sizeof (entry64->d_ino)          \
  42           == offsetof (struct dirent, memb) - sizeof (ino_t))
  43   MATCH (d_reclen);
  44   MATCH (d_type);
  45   MATCH (d_namlen);
  46 # undef MATCH
  47
  48   if (entry64 == NULL)
  49     return NULL;
  50
  51   struct dirent *const entry = ((void *) (&entry64->d_ino + 1)
  52                                 - sizeof entry->d_ino);
  53   const ino_t d_ino = entry64->d_ino;
  54   if (d_ino != entry64->d_ino)
  55     {
  56       __set_errno (EOVERFLOW);
  57       return NULL;
  58     }
  59 # if BYTE_ORDER != BIG_ENDIAN   /* We just skipped over the zero high word.  */
  60   entry->d_ino = d_ino; /* ... or the nonzero low word, swap it.  */
  61 # endif
  62   entry->d_reclen -= sizeof entry64->d_ino - sizeof entry->d_ino;
  63   return entry;
  64 }
  65
  66 weak_alias (__readdir, readdir)