1 /* backupfile.c -- make Emacs style backup file names
3 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
4 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; see the file COPYING.
19 If not, write to the Free Software Foundation,
20 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
22 /* Written by Paul Eggert and David MacKenzie.
23 Some algorithms adapted from GNU Emacs. */
29 #include "backupfile.h"
45 #ifndef _D_EXACT_NAMLEN
46 # define _D_EXACT_NAMLEN(dp) strlen ((dp)->d_name)
49 # define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
51 # define REAL_DIR_ENTRY(dp) 1
54 #if ! (HAVE_PATHCONF && defined _PC_NAME_MAX)
55 # define pathconf(file, option) (errno = -1)
58 #ifndef _POSIX_NAME_MAX
59 # define _POSIX_NAME_MAX 14
62 # define SIZE_MAX ((size_t) -1)
65 #if defined _XOPEN_NAME_MAX
66 # define NAME_MAX_MINIMUM _XOPEN_NAME_MAX
68 # define NAME_MAX_MINIMUM _POSIX_NAME_MAX
71 #ifndef HAVE_DOS_FILE_NAMES
72 # define HAVE_DOS_FILE_NAMES 0
74 #ifndef HAVE_LONG_FILE_NAMES
75 # define HAVE_LONG_FILE_NAMES 0
78 /* ISDIGIT differs from isdigit, as follows:
79 - Its arg may be any int or unsigned int; it need not be an unsigned char
81 - It's typically faster.
82 POSIX says that only '0' through '9' are digits. Prefer ISDIGIT to
83 ISDIGIT unless it's important to use the locale's definition
84 of `digit' even when the host does not conform to POSIX. */
85 #define ISDIGIT(c) ((unsigned int) (c) - '0' <= 9)
87 /* The extension added to file names to produce a simple (as opposed
88 to numbered) backup file name. */
89 char const *simple_backup_suffix = "~";
92 /* If FILE (which was of length FILELEN before an extension was
93 appended to it) is too long, replace the extension with the single
94 char E. If the result is still too long, remove the char just
98 check_extension (char *file, size_t filelen, char e)
100 char *base = last_component (file);
101 size_t baselen = base_len (base);
102 size_t baselen_max = HAVE_LONG_FILE_NAMES ? 255 : NAME_MAX_MINIMUM;
104 if (HAVE_DOS_FILE_NAMES || NAME_MAX_MINIMUM < baselen)
106 /* The new base name is long enough to require a pathconf check. */
109 /* Temporarily modify the buffer into its parent directory name,
110 invoke pathconf on the directory, and then restore the buffer. */
111 char tmp[sizeof "."];
112 memcpy (tmp, base, sizeof ".");
115 name_max = pathconf (file, _PC_NAME_MAX);
116 if (0 <= name_max || errno == 0)
118 long size = baselen_max = name_max;
119 if (name_max != size)
120 baselen_max = SIZE_MAX;
122 memcpy (base, tmp, sizeof ".");
125 if (HAVE_DOS_FILE_NAMES && baselen_max <= 12)
127 /* Live within DOS's 8.3 limit. */
128 char *dot = strchr (base, '.');
133 char const *second_dot = strchr (dot + 1, '.');
134 baselen_max = (second_dot
136 : dot + 1 - base + 3);
140 if (baselen_max < baselen)
142 baselen = file + filelen - base;
143 if (baselen_max <= baselen)
144 baselen = baselen_max - 1;
146 base[baselen + 1] = '\0';
150 /* Returned values for NUMBERED_BACKUP. */
152 enum numbered_backup_result
154 /* The new backup name is the same length as an existing backup
155 name, so it's valid for that directory. */
156 BACKUP_IS_SAME_LENGTH,
158 /* Some backup names already exist, but the returned name is longer
159 than any of them, and its length should be checked. */
162 /* There are no existing backup names. The new name's length
163 should be checked. */
167 /* *BUFFER contains a file name. Store into *BUFFER the next backup
168 name for the named file, with a version number greater than all the
169 existing numbered backups. Reallocate *BUFFER as necessary; its
170 initial allocated size is BUFFER_SIZE, which must be at least 4
171 bytes longer than the file name to make room for the initially
172 appended ".~1". FILELEN is the length of the original file name.
173 The returned value indicates what kind of backup was found. If an
174 I/O or other read error occurs, use the highest backup number that
177 static enum numbered_backup_result
178 numbered_backup (char **buffer, size_t buffer_size, size_t filelen)
180 enum numbered_backup_result result = BACKUP_IS_NEW;
184 size_t versionlenmax = 1;
185 char *base = last_component (buf);
186 size_t base_offset = base - buf;
187 size_t baselen = base_len (base);
189 /* Temporarily modify the buffer into its parent directory name,
190 open the directory, and then restore the buffer. */
191 char tmp[sizeof "."];
192 memcpy (tmp, base, sizeof ".");
194 dirp = opendir (buf);
195 memcpy (base, tmp, sizeof ".");
196 strcpy (base + baselen, ".~1~");
201 while ((dp = readdir (dirp)) != NULL)
209 if (! REAL_DIR_ENTRY (dp) || _D_EXACT_NAMLEN (dp) < baselen + 4)
212 if (memcmp (buf + base_offset, dp->d_name, baselen + 2) != 0)
215 p = dp->d_name + baselen + 2;
217 /* Check whether this file has a version number and if so,
218 whether it is larger. Use string operations rather than
219 integer arithmetic, to avoid problems with integer overflow. */
221 if (! ('1' <= *p && *p <= '9'))
223 all_9s = (*p == '9');
224 for (versionlen = 1; ISDIGIT (p[versionlen]); versionlen++)
225 all_9s &= (p[versionlen] == '9');
227 if (! (p[versionlen] == '~' && !p[versionlen + 1]
228 && (versionlenmax < versionlen
229 || (versionlenmax == versionlen
230 && memcmp (buf + filelen + 2, p, versionlen) <= 0))))
233 /* This directory has the largest version number seen so far.
234 Append this highest numbered extension to the file name,
235 prepending '0' to the number if it is all 9s. */
237 versionlenmax = all_9s + versionlen;
238 result = (all_9s ? BACKUP_IS_LONGER : BACKUP_IS_SAME_LENGTH);
239 new_buflen = filelen + 2 + versionlenmax + 1;
240 if (buffer_size <= new_buflen)
242 buf = xnrealloc (buf, 2, new_buflen);
243 buffer_size = new_buflen * 2;
250 memcpy (q, p, versionlen + 2);
252 /* Add 1 to the version number. */
265 /* Return the name of the new backup file for the existing file FILE,
266 allocated with malloc. Report an error and fail if out of memory.
267 Do not call this function if backup_type == no_backups. */
270 find_backup_file_name (char const *file, enum backup_type backup_type)
272 size_t filelen = strlen (file);
277 /* Allow room for simple or ".~N~" backups. The guess must be at
278 least sizeof ".~1~", but otherwise will be adjusted as needed. */
279 size_t simple_backup_suffix_size = strlen (simple_backup_suffix) + 1;
280 size_t backup_suffix_size_guess = simple_backup_suffix_size;
281 enum { GUESS = sizeof ".~12345~" };
282 if (backup_suffix_size_guess < GUESS)
283 backup_suffix_size_guess = GUESS;
285 ssize = filelen + backup_suffix_size_guess + 1;
287 memcpy (s, file, filelen + 1);
289 if (backup_type != simple_backups)
290 switch (numbered_backup (&s, ssize, filelen))
292 case BACKUP_IS_SAME_LENGTH:
295 case BACKUP_IS_LONGER:
300 simple = (backup_type == numbered_existing_backups);
305 memcpy (s + filelen, simple_backup_suffix, simple_backup_suffix_size);
306 check_extension (s, filelen, '~');
310 static char const * const backup_args[] =
312 /* In a series of synonyms, present the most meaningful first, so
313 that argmatch_valid be more readable. */
321 static const enum backup_type backup_types[] =
323 no_backups, no_backups,
324 simple_backups, simple_backups,
325 numbered_existing_backups, numbered_existing_backups,
326 numbered_backups, numbered_backups
329 /* Ensure that these two vectors have the same number of elements,
330 not counting the final NULL in the first one. */
331 ARGMATCH_VERIFY (backup_args, backup_types);
333 /* Return the type of backup specified by VERSION.
334 If VERSION is NULL or the empty string, return numbered_existing_backups.
335 If VERSION is invalid or ambiguous, fail with a diagnostic appropriate
336 for the specified CONTEXT. Unambiguous abbreviations are accepted. */
339 get_version (char const *context, char const *version)
341 if (version == 0 || *version == 0)
342 return numbered_existing_backups;
344 return XARGMATCH (context, version, backup_args, backup_types);
348 /* Return the type of backup specified by VERSION.
349 If VERSION is NULL, use the value of the envvar VERSION_CONTROL.
350 If the specified string is invalid or ambiguous, fail with a diagnostic
351 appropriate for the specified CONTEXT.
352 Unambiguous abbreviations are accepted. */
355 xget_version (char const *context, char const *version)
357 if (version && *version)
358 return get_version (context, version);
360 return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));