1/* backupfile.c -- make Emacs style backup file names
2   Copyright (C) 1990-1999, 2000-2003, 2005-2006 Free Software Foundation, Inc.
3
4   This program is free software; you can redistribute it and/or modify
5   it under the terms of the GNU General Public License as published by
6   the Free Software Foundation; either version 2, or (at your option)
7   any later version.
8
9   This program 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
12   GNU General Public License for more details.
13
14   You should have received a copy of the GNU General Public License
15   along with this program; see the file COPYING.
16   If not, write to the Free Software Foundation,
17   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
18
19/* Written by David MacKenzie <djm@gnu.ai.mit.edu>.
20   Some algorithms adapted from GNU Emacs. */
21
22#include <config.h>
23
24#include "argmatch.h"
25#include "backupfile.h"
26
27#include <stdio.h>
28#include <sys/types.h>
29#if HAVE_STRING_H
30# include <string.h>
31#else
32# include <strings.h>
33#endif
34
35#if HAVE_DIRENT_H
36# include <dirent.h>
37#endif
38
39#include <stdlib.h>
40
41#include "basename.h"
42
43#if HAVE_DIRENT_H
44# define HAVE_DIR 1
45#else
46# define HAVE_DIR 0
47#endif
48
49#include <limits.h>
50
51/* Upper bound on the string length of an integer converted to string.
52   302 / 1000 is ceil (log10 (2.0)).  Subtract 1 for the sign bit;
53   add 1 for integer division truncation; add 1 more for a minus sign.  */
54#define INT_STRLEN_BOUND(t) ((sizeof (t) * CHAR_BIT - 1) * 302 / 1000 + 2)
55
56/* ISDIGIT differs from isdigit, as follows:
57   - Its arg may be any int or unsigned int; it need not be an unsigned char.
58   - It's guaranteed to evaluate its argument exactly once.
59   - It's typically faster.
60   Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
61   only '0' through '9' are digits.  Prefer ISDIGIT to isdigit unless
62   it's important to use the locale's definition of `digit' even when the
63   host does not conform to Posix.  */
64#define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)
65
66#if D_INO_IN_DIRENT
67# define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
68#else
69# define REAL_DIR_ENTRY(dp) 1
70#endif
71
72/* The extension added to file names to produce a simple (as opposed
73   to numbered) backup file name. */
74const char *simple_backup_suffix = "~";
75
76#if HAVE_DIR
77static int max_backup_version (const char *, const char *);
78static int version_number (const char *, const char *, size_t);
79#endif
80
81/* Return the name of the new backup file for file FILE,
82   allocated with malloc.  Return 0 if out of memory.
83   FILE must not end with a '/' unless it is the root directory.
84   Do not call this function if backup_type == none. */
85
86char *
87find_backup_file_name (const char *file, enum backup_type backup_type)
88{
89  size_t backup_suffix_size_max;
90  size_t file_len = strlen (file);
91  size_t numbered_suffix_size_max = INT_STRLEN_BOUND (int) + 4;
92  char *s;
93  const char *suffix = simple_backup_suffix;
94
95  /* Allow room for simple or `.~N~' backups.  */
96  backup_suffix_size_max = strlen (simple_backup_suffix) + 1;
97  if (HAVE_DIR && backup_suffix_size_max < numbered_suffix_size_max)
98    backup_suffix_size_max = numbered_suffix_size_max;
99
100  s = malloc (file_len + backup_suffix_size_max + numbered_suffix_size_max);
101  if (s)
102    {
103      strcpy (s, file);
104
105#if HAVE_DIR
106      if (backup_type != simple)
107	{
108	  int highest_backup;
109	  size_t dir_len = basename (s) - s;
110
111	  strcpy (s + dir_len, ".");
112	  highest_backup = max_backup_version (file + dir_len, s);
113	  if (! (backup_type == numbered_existing && highest_backup == 0))
114	    {
115	      char *numbered_suffix = s + (file_len + backup_suffix_size_max);
116	      sprintf (numbered_suffix, ".~%d~", highest_backup + 1);
117	      suffix = numbered_suffix;
118	    }
119	  strcpy (s, file);
120	}
121#endif /* HAVE_DIR */
122
123      addext (s, suffix, '~');
124    }
125  return s;
126}
127
128#if HAVE_DIR
129
130/* Return the number of the highest-numbered backup file for file
131   FILE in directory DIR.  If there are no numbered backups
132   of FILE in DIR, or an error occurs reading DIR, return 0.
133   */
134
135static int
136max_backup_version (const char *file, const char *dir)
137{
138  DIR *dirp;
139  struct dirent *dp;
140  int highest_version;
141  int this_version;
142  size_t file_name_length;
143
144  dirp = opendir (dir);
145  if (!dirp)
146    return 0;
147
148  highest_version = 0;
149  file_name_length = strlen (file);
150
151  while ((dp = readdir (dirp)) != 0)
152    {
153      if (!REAL_DIR_ENTRY (dp) || strlen (dp->d_name) < file_name_length + 4)
154	continue;
155
156      this_version = version_number (file, dp->d_name, file_name_length);
157      if (this_version > highest_version)
158	highest_version = this_version;
159    }
160  if (closedir (dirp))
161    return 0;
162  return highest_version;
163}
164
165/* If BACKUP is a numbered backup of BASE, return its version number;
166   otherwise return 0.  BASE_LENGTH is the length of BASE.
167   */
168
169static int
170version_number (const char *base, const char *backup, size_t base_length)
171{
172  int version;
173  const char *p;
174
175  version = 0;
176  if (strncmp (base, backup, base_length) == 0
177      && backup[base_length] == '.'
178      && backup[base_length + 1] == '~')
179    {
180      for (p = &backup[base_length + 2]; ISDIGIT (*p); ++p)
181	version = version * 10 + *p - '0';
182      if (p[0] != '~' || p[1])
183	version = 0;
184    }
185  return version;
186}
187#endif /* HAVE_DIR */
188
189static const char * const backup_args[] =
190{
191  /* In a series of synonyms, present the most meaning full first, so
192     that argmatch_valid be more readable. */
193  "none", "off",
194  "simple", "never",
195  "existing", "nil",
196  "numbered", "t",
197  0
198};
199
200static const enum backup_type backup_types[] =
201{
202  none, none,
203  simple, simple,
204  numbered_existing, numbered_existing,
205  numbered, numbered
206};
207
208/* Return the type of backup specified by VERSION.
209   If VERSION is NULL or the empty string, return numbered_existing.
210   If VERSION is invalid or ambiguous, fail with a diagnostic appropriate
211   for the specified CONTEXT.  Unambiguous abbreviations are accepted.  */
212
213enum backup_type
214get_version (const char *context, const char *version)
215{
216  if (version == 0 || *version == 0)
217    return numbered_existing;
218  else
219    return XARGMATCH (context, version, backup_args, backup_types);
220}
221
222
223/* Return the type of backup specified by VERSION.
224   If VERSION is NULL, use the value of the envvar VERSION_CONTROL.
225   If the specified string is invalid or ambiguous, fail with a diagnostic
226   appropriate for the specified CONTEXT.
227   Unambiguous abbreviations are accepted.  */
228
229enum backup_type
230xget_version (const char *context, const char *version)
231{
232  if (version && *version)
233    return get_version (context, version);
234  else
235    return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));
236}
237