1/* backupfile.c -- make Emacs style backup file names
2   Copyright (C) 1990-1997, 1998, 1999 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   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
18
19/* Written by David MacKenzie <djm@gnu.ai.mit.edu>.
20   Some algorithms adapted from GNU Emacs. */
21
22#if HAVE_CONFIG_H
23# include <config.h>
24#endif
25
26#include <argmatch.h>
27#include <backupfile.h>
28
29#include <stdio.h>
30#include <sys/types.h>
31#if HAVE_STRING_H
32# include <string.h>
33#else
34# include <strings.h>
35#endif
36
37#if HAVE_DIRENT_H
38# include <dirent.h>
39# define NLENGTH(direct) strlen ((direct)->d_name)
40#else
41# define dirent direct
42# define NLENGTH(direct) ((size_t) (direct)->d_namlen)
43# if HAVE_SYS_NDIR_H
44#  include <sys/ndir.h>
45# endif
46# if HAVE_SYS_DIR_H
47#  include <sys/dir.h>
48# endif
49# if HAVE_NDIR_H
50#  include <ndir.h>
51# endif
52#endif
53
54#if CLOSEDIR_VOID
55/* Fake a return value. */
56# define CLOSEDIR(d) (closedir (d), 0)
57#else
58# define CLOSEDIR(d) closedir (d)
59#endif
60
61#if STDC_HEADERS
62# include <stdlib.h>
63#else
64char *malloc ();
65#endif
66
67#ifndef HAVE_DECL_GETENV
68char *getenv ();
69#endif
70
71char *base_name PARAMS ((char const *));
72
73#if HAVE_DIRENT_H || HAVE_NDIR_H || HAVE_SYS_DIR_H || HAVE_SYS_NDIR_H
74# define HAVE_DIR 1
75#else
76# define HAVE_DIR 0
77#endif
78
79#if HAVE_LIMITS_H
80# include <limits.h>
81#endif
82#ifndef CHAR_BIT
83# define CHAR_BIT 8
84#endif
85/* Upper bound on the string length of an integer converted to string.
86   302 / 1000 is ceil (log10 (2.0)).  Subtract 1 for the sign bit;
87   add 1 for integer division truncation; add 1 more for a minus sign.  */
88#define INT_STRLEN_BOUND(t) ((sizeof (t) * CHAR_BIT - 1) * 302 / 1000 + 2)
89
90/* ISDIGIT differs from isdigit, as follows:
91   - Its arg may be any int or unsigned int; it need not be an unsigned char.
92   - It's guaranteed to evaluate its argument exactly once.
93   - It's typically faster.
94   Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
95   only '0' through '9' are digits.  Prefer ISDIGIT to isdigit unless
96   it's important to use the locale's definition of `digit' even when the
97   host does not conform to Posix.  */
98#define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)
99
100#if D_INO_IN_DIRENT
101# define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
102#else
103# define REAL_DIR_ENTRY(dp) 1
104#endif
105
106/* The extension added to file names to produce a simple (as opposed
107   to numbered) backup file name. */
108const char *simple_backup_suffix = "~";
109
110static int max_backup_version PARAMS ((const char *, const char *));
111static int version_number PARAMS ((const char *, const char *, size_t));
112
113/* Return the name of the new backup file for file FILE,
114   allocated with malloc.  Return 0 if out of memory.
115   FILE must not end with a '/' unless it is the root directory.
116   Do not call this function if backup_type == none. */
117
118char *
119find_backup_file_name (const char *file, enum backup_type backup_type)
120{
121  size_t backup_suffix_size_max;
122  size_t file_len = strlen (file);
123  size_t numbered_suffix_size_max = INT_STRLEN_BOUND (int) + 4;
124  char *s;
125  const char *suffix = simple_backup_suffix;
126
127  /* Allow room for simple or `.~N~' backups.  */
128  backup_suffix_size_max = strlen (simple_backup_suffix) + 1;
129  if (HAVE_DIR && backup_suffix_size_max < numbered_suffix_size_max)
130    backup_suffix_size_max = numbered_suffix_size_max;
131
132  s = malloc (file_len + backup_suffix_size_max + numbered_suffix_size_max);
133  if (s)
134    {
135      strcpy (s, file);
136
137#if HAVE_DIR
138      if (backup_type != simple)
139	{
140	  int highest_backup;
141	  size_t dir_len = base_name (s) - s;
142
143	  strcpy (s + dir_len, ".");
144	  highest_backup = max_backup_version (file + dir_len, s);
145	  if (! (backup_type == numbered_existing && highest_backup == 0))
146	    {
147	      char *numbered_suffix = s + (file_len + backup_suffix_size_max);
148	      sprintf (numbered_suffix, ".~%d~", highest_backup + 1);
149	      suffix = numbered_suffix;
150	    }
151	  strcpy (s, file);
152	}
153#endif /* HAVE_DIR */
154
155      addext (s, suffix, '~');
156    }
157  return s;
158}
159
160#if HAVE_DIR
161
162/* Return the number of the highest-numbered backup file for file
163   FILE in directory DIR.  If there are no numbered backups
164   of FILE in DIR, or an error occurs reading DIR, return 0.
165   */
166
167static int
168max_backup_version (const char *file, const char *dir)
169{
170  DIR *dirp;
171  struct dirent *dp;
172  int highest_version;
173  int this_version;
174  size_t file_name_length;
175
176  dirp = opendir (dir);
177  if (!dirp)
178    return 0;
179
180  highest_version = 0;
181  file_name_length = strlen (file);
182
183  while ((dp = readdir (dirp)) != 0)
184    {
185      if (!REAL_DIR_ENTRY (dp) || NLENGTH (dp) < file_name_length + 4)
186	continue;
187
188      this_version = version_number (file, dp->d_name, file_name_length);
189      if (this_version > highest_version)
190	highest_version = this_version;
191    }
192  if (CLOSEDIR (dirp))
193    return 0;
194  return highest_version;
195}
196
197/* If BACKUP is a numbered backup of BASE, return its version number;
198   otherwise return 0.  BASE_LENGTH is the length of BASE.
199   */
200
201static int
202version_number (const char *base, const char *backup, size_t base_length)
203{
204  int version;
205  const char *p;
206
207  version = 0;
208  if (strncmp (base, backup, base_length) == 0
209      && backup[base_length] == '.'
210      && backup[base_length + 1] == '~')
211    {
212      for (p = &backup[base_length + 2]; ISDIGIT (*p); ++p)
213	version = version * 10 + *p - '0';
214      if (p[0] != '~' || p[1])
215	version = 0;
216    }
217  return version;
218}
219#endif /* HAVE_DIR */
220
221static const char * const backup_args[] =
222{
223  /* In a series of synonyms, present the most meaning full first, so
224     that argmatch_valid be more readable. */
225  "none", "off",
226  "simple", "never",
227  "existing", "nil",
228  "numbered", "t",
229  0
230};
231
232static const enum backup_type backup_types[] =
233{
234  none, none,
235  simple, simple,
236  numbered_existing, numbered_existing,
237  numbered, numbered
238};
239
240/* Return the type of backup specified by VERSION.
241   If VERSION is NULL or the empty string, return numbered_existing.
242   If VERSION is invalid or ambiguous, fail with a diagnostic appropriate
243   for the specified CONTEXT.  Unambiguous abbreviations are accepted.  */
244
245enum backup_type
246get_version (const char *context, const char *version)
247{
248  if (version == 0 || *version == 0)
249    return numbered_existing;
250  else
251    return XARGMATCH (context, version, backup_args, backup_types);
252}
253
254
255/* Return the type of backup specified by VERSION.
256   If VERSION is NULL, use the value of the envvar VERSION_CONTROL.
257   If the specified string is invalid or ambiguous, fail with a diagnostic
258   appropriate for the specified CONTEXT.
259   Unambiguous abbreviations are accepted.  */
260
261enum backup_type
262xget_version (const char *context, const char *version)
263{
264  if (version && *version)
265    return get_version (context, version);
266  else
267    return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));
268}
269