1/* Determine whether two file names refer to the same file.
2
3   Copyright (C) 1997, 1998, 1999, 2000, 2002, 2003, 2004, 2005, 2006 Free
4   Software Foundation, Inc.
5
6   This program is free software: you can redistribute it and/or modify
7   it under the terms of the GNU General Public License as published by
8   the Free Software Foundation; either version 3 of the License, or
9   (at your option) any later version.
10
11   This program is distributed in the hope that it will be useful,
12   but WITHOUT ANY WARRANTY; without even the implied warranty of
13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14   GNU General Public License for more details.
15
16   You should have received a copy of the GNU General Public License
17   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
18
19/* written by Jim Meyering */
20
21#include <config.h>
22
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>
31
32#include <string.h>
33
34#include <limits.h>
35#ifndef _POSIX_NAME_MAX
36# define _POSIX_NAME_MAX 14
37#endif
38
39#include "same.h"
40#include "dirname.h"
41#include "error.h"
42#include "same-inode.h"
43#include "xalloc.h"
44
45#ifndef MIN
46# define MIN(a, b) ((a) < (b) ? (a) : (b))
47#endif
48
49/* Return nonzero if SOURCE and DEST point to the same name in the same
50   directory.  */
51
52bool
53same_name (const char *source, const char *dest)
54{
55  /* Compare the basenames.  */
56  char const *source_basename = last_component (source);
57  char const *dest_basename = last_component (dest);
58  size_t source_baselen = base_len (source_basename);
59  size_t dest_baselen = base_len (dest_basename);
60  bool identical_basenames =
61    (source_baselen == dest_baselen
62     && memcmp (source_basename, dest_basename, dest_baselen) == 0);
63  bool compare_dirs = identical_basenames;
64  bool same = false;
65
66#if ! _POSIX_NO_TRUNC && HAVE_PATHCONF && defined _PC_NAME_MAX
67  /* This implementation silently truncates components of file names.  If
68     the base names might be truncated, check whether the truncated
69     base names are the same, while checking the directories.  */
70  size_t slen_max = HAVE_LONG_FILE_NAMES ? 255 : _POSIX_NAME_MAX;
71  size_t min_baselen = MIN (source_baselen, dest_baselen);
72  if (slen_max <= min_baselen
73      && memcmp (source_basename, dest_basename, slen_max) == 0)
74    compare_dirs = true;
75#endif
76
77  if (compare_dirs)
78    {
79      struct stat source_dir_stats;
80      struct stat dest_dir_stats;
81      char *source_dirname, *dest_dirname;
82
83      /* Compare the parent directories (via the device and inode numbers).  */
84      source_dirname = dir_name (source);
85      dest_dirname = dir_name (dest);
86
87      if (stat (source_dirname, &source_dir_stats))
88	{
89	  /* Shouldn't happen.  */
90	  error (1, errno, "%s", source_dirname);
91	}
92
93      if (stat (dest_dirname, &dest_dir_stats))
94	{
95	  /* Shouldn't happen.  */
96	  error (1, errno, "%s", dest_dirname);
97	}
98
99      same = SAME_INODE (source_dir_stats, dest_dir_stats);
100
101#if ! _POSIX_NO_TRUNC && HAVE_PATHCONF && defined _PC_NAME_MAX
102      if (same && ! identical_basenames)
103	{
104	  long name_max = (errno = 0, pathconf (dest_dirname, _PC_NAME_MAX));
105	  if (name_max < 0)
106	    {
107	      if (errno)
108		{
109		  /* Shouldn't happen.  */
110		  error (1, errno, "%s", dest_dirname);
111		}
112	      same = false;
113	    }
114	  else
115	    same = (name_max <= min_baselen
116		    && memcmp (source_basename, dest_basename, name_max) == 0);
117	}
118#endif
119
120      free (source_dirname);
121      free (dest_dirname);
122    }
123
124  return same;
125}
126