vma-iter: Add support for Android.
[gnulib.git] / lib / same.c
blob39b63983179df7780ffffdf70629968c3c4950f6
1 /* Determine whether two file names refer to the same file.
3 Copyright (C) 1997-2000, 2002-2006, 2009-2019 Free Software Foundation, Inc.
5 This program is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3 of the License, or
8 (at your option) any later version.
10 This program 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
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <https://www.gnu.org/licenses/>. */
18 /* written by Jim Meyering */
20 #include <config.h>
22 #include <fcntl.h>
23 #include <stdbool.h>
24 #include <stdio.h>
25 #include <unistd.h>
26 #include <stdlib.h>
27 #include <sys/types.h>
28 #include <sys/stat.h>
29 #include <ctype.h>
30 #include <errno.h>
32 #include <string.h>
34 #include <limits.h>
35 #ifndef _POSIX_NAME_MAX
36 # define _POSIX_NAME_MAX 14
37 #endif
39 #include "same.h"
40 #include "dirname.h"
41 #include "error.h"
42 #include "same-inode.h"
44 #ifndef MIN
45 # define MIN(a, b) ((a) < (b) ? (a) : (b))
46 #endif
48 /* Whether file name components are silently truncated (behavior that
49 POSIX stopped allowing in 2008). This enables checks whether
50 truncated base names are the same, while checking the directories. */
51 #if !_POSIX_NO_TRUNC && HAVE_FPATHCONF && defined _PC_NAME_MAX
52 # define CHECK_TRUNCATION true
53 #else
54 # define CHECK_TRUNCATION false
55 #endif
57 /* Return nonzero if SOURCE and DEST point to the same name in the same
58 directory. */
60 bool
61 same_name (const char *source, const char *dest)
63 return same_nameat (AT_FDCWD, source, AT_FDCWD, dest);
66 /* Likewise, but interpret the file names relative to SOURCE_FD and DEST_FD,
67 in the style of openat. */
69 bool
70 same_nameat (int source_dfd, char const *source,
71 int dest_dfd, char const *dest)
73 /* Compare the basenames. */
74 char const *source_basename = last_component (source);
75 char const *dest_basename = last_component (dest);
76 size_t source_baselen = base_len (source_basename);
77 size_t dest_baselen = base_len (dest_basename);
78 bool identical_basenames =
79 (source_baselen == dest_baselen
80 && memcmp (source_basename, dest_basename, dest_baselen) == 0);
81 bool compare_dirs = identical_basenames;
82 bool same = false;
84 #if CHECK_TRUNCATION
85 size_t slen_max = HAVE_LONG_FILE_NAMES ? 255 : _POSIX_NAME_MAX;
86 size_t min_baselen = MIN (source_baselen, dest_baselen);
87 if (slen_max <= min_baselen
88 && memcmp (source_basename, dest_basename, slen_max) == 0)
89 compare_dirs = true;
90 #endif
92 if (compare_dirs)
94 struct stat source_dir_stats;
95 struct stat dest_dir_stats;
97 /* Compare the parent directories (via the device and inode numbers). */
98 char *source_dirname = dir_name (source);
99 int flags = AT_SYMLINK_NOFOLLOW;
100 if (fstatat (source_dfd, source_dirname, &source_dir_stats, flags) != 0)
102 /* Shouldn't happen. */
103 error (1, errno, "%s", source_dirname);
105 free (source_dirname);
107 char *dest_dirname = dir_name (dest);
109 #if CHECK_TRUNCATION
110 int destdir_errno = 0;
111 int open_flags = O_SEARCH | O_CLOEXEC | O_DIRECTORY;
112 int destdir_fd = openat (dest_dfd, dest_dirname, open_flags);
113 if (destdir_fd < 0 || fstat (destdir_fd, &dest_dir_stats) != 0)
114 destdir_errno = errno;
115 else if (SAME_INODE (source_dir_stats, dest_dir_stats))
117 same = identical_basenames;
118 if (! same)
120 errno = 0;
121 long name_max = fpathconf (destdir_fd, _PC_NAME_MAX);
122 if (name_max < 0)
123 destdir_errno = errno;
124 else
125 same = (name_max <= min_baselen
126 && (memcmp (source_basename, dest_basename, name_max)
127 == 0));
130 close (destdir_fd);
131 if (destdir_errno != 0)
133 /* Shouldn't happen. */
134 error (1, destdir_errno, "%s", dest_dirname);
136 #else
137 if (fstatat (dest_dfd, dest_dirname, &dest_dir_stats, flags) != 0)
139 /* Shouldn't happen. */
140 error (1, errno, "%s", dest_dirname);
142 same = SAME_INODE (source_dir_stats, dest_dir_stats);
143 #endif
145 free (dest_dirname);
148 return same;