1 /* Copyright (C) 1993-2022 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 <https://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 *
__readdir(DIR * dirp)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)
67