1/* Determine whether two file names refer to the same file.
2
3   Copyright (C) 1997-2000, 2002-2006, 2009-2010 Free Software Foundation, Inc.
4
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.
9
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.
14
15   You should have received a copy of the GNU General Public License
16   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
17
18/* written by Jim Meyering */
19
20#include <config.h>
21
22#include <stdbool.h>
23#include <stdio.h>
24#include <unistd.h>
25#include <stdlib.h>
26#include <sys/types.h>
27#include <sys/stat.h>
28#include <ctype.h>
29#include <errno.h>
30
31#include <string.h>
32
33#include <limits.h>
34#ifndef _POSIX_NAME_MAX
35# define _POSIX_NAME_MAX 14
36#endif
37
38#include "same.h"
39#include "dirname.h"
40#include "error.h"
41#include "same-inode.h"
42
43#ifndef MIN
44# define MIN(a, b) ((a) < (b) ? (a) : (b))
45#endif
46
47/* Return nonzero if SOURCE and DEST point to the same name in the same
48   directory.  */
49
50bool
51same_name (const char *source, const char *dest)
52{
53  /* Compare the basenames.  */
54  char const *source_basename = last_component (source);
55  char const *dest_basename = last_component (dest);
56  size_t source_baselen = base_len (source_basename);
57  size_t dest_baselen = base_len (dest_basename);
58  bool identical_basenames =
59    (source_baselen == dest_baselen
60     && memcmp (source_basename, dest_basename, dest_baselen) == 0);
61  bool compare_dirs = identical_basenames;
62  bool same = false;
63
64#if ! _POSIX_NO_TRUNC && HAVE_PATHCONF && defined _PC_NAME_MAX
65  /* This implementation silently truncates components of file names.  If
66     the base names might be truncated, check whether the truncated
67     base names are the same, while checking the directories.  */
68  size_t slen_max = HAVE_LONG_FILE_NAMES ? 255 : _POSIX_NAME_MAX;
69  size_t min_baselen = MIN (source_baselen, dest_baselen);
70  if (slen_max <= min_baselen
71      && memcmp (source_basename, dest_basename, slen_max) == 0)
72    compare_dirs = true;
73#endif
74
75  if (compare_dirs)
76    {
77      struct stat source_dir_stats;
78      struct stat dest_dir_stats;
79      char *source_dirname, *dest_dirname;
80
81      /* Compare the parent directories (via the device and inode numbers).  */
82      source_dirname = dir_name (source);
83      dest_dirname = dir_name (dest);
84
85      if (stat (source_dirname, &source_dir_stats))
86        {
87          /* Shouldn't happen.  */
88          error (1, errno, "%s", source_dirname);
89        }
90
91      if (stat (dest_dirname, &dest_dir_stats))
92        {
93          /* Shouldn't happen.  */
94          error (1, errno, "%s", dest_dirname);
95        }
96
97      same = SAME_INODE (source_dir_stats, dest_dir_stats);
98
99#if ! _POSIX_NO_TRUNC && HAVE_PATHCONF && defined _PC_NAME_MAX
100      if (same && ! identical_basenames)
101        {
102          long name_max = (errno = 0, pathconf (dest_dirname, _PC_NAME_MAX));
103          if (name_max < 0)
104            {
105              if (errno)
106                {
107                  /* Shouldn't happen.  */
108                  error (1, errno, "%s", dest_dirname);
109                }
110              same = false;
111            }
112          else
113            same = (name_max <= min_baselen
114                    && memcmp (source_basename, dest_basename, name_max) == 0);
115        }
116#endif
117
118      free (source_dirname);
119      free (dest_dirname);
120    }
121
122  return same;
123}
124