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"
46 # define NLENGTH(direct) strlen ((direct)->d_name)
48 # define dirent direct
49 # define NLENGTH(direct) ((size_t) (direct)->d_namlen)
54 # define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
56 # define REAL_DIR_ENTRY(dp) 1
59 #if ! (HAVE_PATHCONF && defined _PC_NAME_MAX)
60 # define pathconf(file, option) (errno = -1)
63 #ifndef _POSIX_NAME_MAX
64 # define _POSIX_NAME_MAX 14
67 # define SIZE_MAX ((size_t) -1)
70 #if defined _XOPEN_NAME_MAX
71 # define NAME_MAX_MINIMUM _XOPEN_NAME_MAX
73 # define NAME_MAX_MINIMUM _POSIX_NAME_MAX
76 #ifndef HAVE_DOS_FILE_NAMES
77 # define HAVE_DOS_FILE_NAMES 0
79 #ifndef HAVE_LONG_FILE_NAMES
80 # define HAVE_LONG_FILE_NAMES 0
83 /* ISDIGIT differs from isdigit, as follows:
84 - Its arg may be any int or unsigned int; it need not be an unsigned char
86 - It's typically faster.
87 POSIX says that only '0' through '9' are digits. Prefer ISDIGIT to
88 ISDIGIT unless it's important to use the locale's definition
89 of `digit' even when the host does not conform to POSIX. */
90 #define ISDIGIT(c) ((unsigned int) (c) - '0' <= 9)
92 /* The extension added to file names to produce a simple (as opposed
93 to numbered) backup file name. */
94 char const *simple_backup_suffix = "~";
97 /* If FILE (which was of length FILELEN before an extension was
98 appended to it) is too long, replace the extension with the single
99 char E. If the result is still too long, remove the char just
103 check_extension (char *file, size_t filelen, char e)
105 char *base = last_component (file);
106 size_t baselen = base_len (base);
107 size_t baselen_max = HAVE_LONG_FILE_NAMES ? 255 : NAME_MAX_MINIMUM;
109 if (HAVE_DOS_FILE_NAMES || NAME_MAX_MINIMUM < baselen)
111 /* The new base name is long enough to require a pathconf check. */
114 /* Temporarily modify the buffer into its parent directory name,
115 invoke pathconf on the directory, and then restore the buffer. */
116 char tmp[sizeof "."];
117 memcpy (tmp, base, sizeof ".");
120 name_max = pathconf (file, _PC_NAME_MAX);
121 if (0 <= name_max || errno == 0)
123 long size = baselen_max = name_max;
124 if (name_max != size)
125 baselen_max = SIZE_MAX;
127 memcpy (base, tmp, sizeof ".");
130 if (HAVE_DOS_FILE_NAMES && baselen_max <= 12)
132 /* Live within DOS's 8.3 limit. */
133 char *dot = strchr (base, '.');
138 char const *second_dot = strchr (dot + 1, '.');
139 baselen_max = (second_dot
141 : dot + 1 - base + 3);
145 if (baselen_max < baselen)
147 baselen = file + filelen - base;
148 if (baselen_max <= baselen)
149 baselen = baselen_max - 1;
151 base[baselen + 1] = '\0';
155 /* Returned values for NUMBERED_BACKUP. */
157 enum numbered_backup_result
159 /* The new backup name is the same length as an existing backup
160 name, so it's valid for that directory. */
161 BACKUP_IS_SAME_LENGTH,
163 /* Some backup names already exist, but the returned name is longer
164 than any of them, and its length should be checked. */
167 /* There are no existing backup names. The new name's length
168 should be checked. */
172 /* *BUFFER contains a file name. Store into *BUFFER the next backup
173 name for the named file, with a version number greater than all the
174 existing numbered backups. Reallocate *BUFFER as necessary; its
175 initial allocated size is BUFFER_SIZE, which must be at least 4
176 bytes longer than the file name to make room for the initially
177 appended ".~1". FILELEN is the length of the original file name.
178 The returned value indicates what kind of backup was found. If an
179 I/O or other read error occurs, use the highest backup number that
182 static enum numbered_backup_result
183 numbered_backup (char **buffer, size_t buffer_size, size_t filelen)
185 enum numbered_backup_result result = BACKUP_IS_NEW;
189 size_t versionlenmax = 1;
190 char *base = last_component (buf);
191 size_t base_offset = base - buf;
192 size_t baselen = base_len (base);
194 /* Temporarily modify the buffer into its parent directory name,
195 open the directory, and then restore the buffer. */
196 char tmp[sizeof "."];
197 memcpy (tmp, base, sizeof ".");
199 dirp = opendir (buf);
200 memcpy (base, tmp, sizeof ".");
201 strcpy (base + baselen, ".~1~");
206 while ((dp = readdir (dirp)) != NULL)
214 if (! REAL_DIR_ENTRY (dp) || NLENGTH (dp) < baselen + 4)
217 if (memcmp (buf + base_offset, dp->d_name, baselen + 2) != 0)
220 p = dp->d_name + baselen + 2;
222 /* Check whether this file has a version number and if so,
223 whether it is larger. Use string operations rather than
224 integer arithmetic, to avoid problems with integer overflow. */
226 if (! ('1' <= *p && *p <= '9'))
228 all_9s = (*p == '9');
229 for (versionlen = 1; ISDIGIT (p[versionlen]); versionlen++)
230 all_9s &= (p[versionlen] == '9');
232 if (! (p[versionlen] == '~' && !p[versionlen + 1]
233 && (versionlenmax < versionlen
234 || (versionlenmax == versionlen
235 && memcmp (buf + filelen + 2, p, versionlen) <= 0))))
238 /* This directory has the largest version number seen so far.
239 Append this highest numbered extension to the file name,
240 prepending '0' to the number if it is all 9s. */
242 versionlenmax = all_9s + versionlen;
243 result = (all_9s ? BACKUP_IS_LONGER : BACKUP_IS_SAME_LENGTH);
244 new_buflen = filelen + 2 + versionlenmax + 1;
245 if (buffer_size <= new_buflen)
247 buf = xnrealloc (buf, 2, new_buflen);
248 buffer_size = new_buflen * 2;
255 memcpy (q, p, versionlen + 2);
257 /* Add 1 to the version number. */
270 /* Return the name of the new backup file for the existing file FILE,
271 allocated with malloc. Report an error and fail if out of memory.
272 Do not call this function if backup_type == no_backups. */
275 find_backup_file_name (char const *file, enum backup_type backup_type)
277 size_t filelen = strlen (file);
282 /* Allow room for simple or ".~N~" backups. The guess must be at
283 least sizeof ".~1~", but otherwise will be adjusted as needed. */
284 size_t simple_backup_suffix_size = strlen (simple_backup_suffix) + 1;
285 size_t backup_suffix_size_guess = simple_backup_suffix_size;
286 enum { GUESS = sizeof ".~12345~" };
287 if (backup_suffix_size_guess < GUESS)
288 backup_suffix_size_guess = GUESS;
290 ssize = filelen + backup_suffix_size_guess + 1;
292 memcpy (s, file, filelen + 1);
294 if (backup_type != simple_backups)
295 switch (numbered_backup (&s, ssize, filelen))
297 case BACKUP_IS_SAME_LENGTH:
300 case BACKUP_IS_LONGER:
305 simple = (backup_type == numbered_existing_backups);
310 memcpy (s + filelen, simple_backup_suffix, simple_backup_suffix_size);
311 check_extension (s, filelen, '~');
315 static char const * const backup_args[] =
317 /* In a series of synonyms, present the most meaningful first, so
318 that argmatch_valid be more readable. */
326 static const enum backup_type backup_types[] =
328 no_backups, no_backups,
329 simple_backups, simple_backups,
330 numbered_existing_backups, numbered_existing_backups,
331 numbered_backups, numbered_backups
334 /* Ensure that these two vectors have the same number of elements,
335 not counting the final NULL in the first one. */
336 ARGMATCH_VERIFY (backup_args, backup_types);
338 /* Return the type of backup specified by VERSION.
339 If VERSION is NULL or the empty string, return numbered_existing_backups.
340 If VERSION is invalid or ambiguous, fail with a diagnostic appropriate
341 for the specified CONTEXT. Unambiguous abbreviations are accepted. */
344 get_version (char const *context, char const *version)
346 if (version == 0 || *version == 0)
347 return numbered_existing_backups;
349 return XARGMATCH (context, version, backup_args, backup_types);
353 /* Return the type of backup specified by VERSION.
354 If VERSION is NULL, use the value of the envvar VERSION_CONTROL.
355 If the specified string is invalid or ambiguous, fail with a diagnostic
356 appropriate for the specified CONTEXT.
357 Unambiguous abbreviations are accepted. */
360 xget_version (char const *context, char const *version)
362 if (version && *version)
363 return get_version (context, version);
365 return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));