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. */
27 #include "backupfile.h"
43 #ifndef _D_EXACT_NAMLEN
44 # define _D_EXACT_NAMLEN(dp) strlen ((dp)->d_name)
47 # define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
49 # define REAL_DIR_ENTRY(dp) 1
52 #if ! (HAVE_PATHCONF && defined _PC_NAME_MAX)
53 # define pathconf(file, option) (errno = -1)
56 #ifndef _POSIX_NAME_MAX
57 # define _POSIX_NAME_MAX 14
60 # define SIZE_MAX ((size_t) -1)
63 #if defined _XOPEN_NAME_MAX
64 # define NAME_MAX_MINIMUM _XOPEN_NAME_MAX
66 # define NAME_MAX_MINIMUM _POSIX_NAME_MAX
69 #ifndef HAVE_DOS_FILE_NAMES
70 # define HAVE_DOS_FILE_NAMES 0
72 #ifndef HAVE_LONG_FILE_NAMES
73 # define HAVE_LONG_FILE_NAMES 0
76 /* ISDIGIT differs from isdigit, as follows:
77 - Its arg may be any int or unsigned int; it need not be an unsigned char
79 - It's typically faster.
80 POSIX says that only '0' through '9' are digits. Prefer ISDIGIT to
81 ISDIGIT unless it's important to use the locale's definition
82 of `digit' even when the host does not conform to POSIX. */
83 #define ISDIGIT(c) ((unsigned int) (c) - '0' <= 9)
85 /* The extension added to file names to produce a simple (as opposed
86 to numbered) backup file name. */
87 char const *simple_backup_suffix = "~";
90 /* If FILE (which was of length FILELEN before an extension was
91 appended to it) is too long, replace the extension with the single
92 char E. If the result is still too long, remove the char just
96 check_extension (char *file, size_t filelen, char e)
98 char *base = last_component (file);
99 size_t baselen = base_len (base);
100 size_t baselen_max = HAVE_LONG_FILE_NAMES ? 255 : NAME_MAX_MINIMUM;
102 if (HAVE_DOS_FILE_NAMES || NAME_MAX_MINIMUM < baselen)
104 /* The new base name is long enough to require a pathconf check. */
107 /* Temporarily modify the buffer into its parent directory name,
108 invoke pathconf on the directory, and then restore the buffer. */
109 char tmp[sizeof "."];
110 memcpy (tmp, base, sizeof ".");
113 name_max = pathconf (file, _PC_NAME_MAX);
114 if (0 <= name_max || errno == 0)
116 long size = baselen_max = name_max;
117 if (name_max != size)
118 baselen_max = SIZE_MAX;
120 memcpy (base, tmp, sizeof ".");
123 if (HAVE_DOS_FILE_NAMES && baselen_max <= 12)
125 /* Live within DOS's 8.3 limit. */
126 char *dot = strchr (base, '.');
131 char const *second_dot = strchr (dot + 1, '.');
132 baselen_max = (second_dot
134 : dot + 1 - base + 3);
138 if (baselen_max < baselen)
140 baselen = file + filelen - base;
141 if (baselen_max <= baselen)
142 baselen = baselen_max - 1;
144 base[baselen + 1] = '\0';
148 /* Returned values for NUMBERED_BACKUP. */
150 enum numbered_backup_result
152 /* The new backup name is the same length as an existing backup
153 name, so it's valid for that directory. */
154 BACKUP_IS_SAME_LENGTH,
156 /* Some backup names already exist, but the returned name is longer
157 than any of them, and its length should be checked. */
160 /* There are no existing backup names. The new name's length
161 should be checked. */
165 /* *BUFFER contains a file name. Store into *BUFFER the next backup
166 name for the named file, with a version number greater than all the
167 existing numbered backups. Reallocate *BUFFER as necessary; its
168 initial allocated size is BUFFER_SIZE, which must be at least 4
169 bytes longer than the file name to make room for the initially
170 appended ".~1". FILELEN is the length of the original file name.
171 The returned value indicates what kind of backup was found. If an
172 I/O or other read error occurs, use the highest backup number that
175 static enum numbered_backup_result
176 numbered_backup (char **buffer, size_t buffer_size, size_t filelen)
178 enum numbered_backup_result result = BACKUP_IS_NEW;
182 size_t versionlenmax = 1;
183 char *base = last_component (buf);
184 size_t base_offset = base - buf;
185 size_t baselen = base_len (base);
187 /* Temporarily modify the buffer into its parent directory name,
188 open the directory, and then restore the buffer. */
189 char tmp[sizeof "."];
190 memcpy (tmp, base, sizeof ".");
192 dirp = opendir (buf);
193 memcpy (base, tmp, sizeof ".");
194 strcpy (base + baselen, ".~1~");
199 while ((dp = readdir (dirp)) != NULL)
207 if (! REAL_DIR_ENTRY (dp) || _D_EXACT_NAMLEN (dp) < baselen + 4)
210 if (memcmp (buf + base_offset, dp->d_name, baselen + 2) != 0)
213 p = dp->d_name + baselen + 2;
215 /* Check whether this file has a version number and if so,
216 whether it is larger. Use string operations rather than
217 integer arithmetic, to avoid problems with integer overflow. */
219 if (! ('1' <= *p && *p <= '9'))
221 all_9s = (*p == '9');
222 for (versionlen = 1; ISDIGIT (p[versionlen]); versionlen++)
223 all_9s &= (p[versionlen] == '9');
225 if (! (p[versionlen] == '~' && !p[versionlen + 1]
226 && (versionlenmax < versionlen
227 || (versionlenmax == versionlen
228 && memcmp (buf + filelen + 2, p, versionlen) <= 0))))
231 /* This directory has the largest version number seen so far.
232 Append this highest numbered extension to the file name,
233 prepending '0' to the number if it is all 9s. */
235 versionlenmax = all_9s + versionlen;
236 result = (all_9s ? BACKUP_IS_LONGER : BACKUP_IS_SAME_LENGTH);
237 new_buflen = filelen + 2 + versionlenmax + 1;
238 if (buffer_size <= new_buflen)
240 buf = xnrealloc (buf, 2, new_buflen);
241 buffer_size = new_buflen * 2;
248 memcpy (q, p, versionlen + 2);
250 /* Add 1 to the version number. */
263 /* Return the name of the new backup file for the existing file FILE,
264 allocated with malloc. Report an error and fail if out of memory.
265 Do not call this function if backup_type == no_backups. */
268 find_backup_file_name (char const *file, enum backup_type backup_type)
270 size_t filelen = strlen (file);
275 /* Allow room for simple or ".~N~" backups. The guess must be at
276 least sizeof ".~1~", but otherwise will be adjusted as needed. */
277 size_t simple_backup_suffix_size = strlen (simple_backup_suffix) + 1;
278 size_t backup_suffix_size_guess = simple_backup_suffix_size;
279 enum { GUESS = sizeof ".~12345~" };
280 if (backup_suffix_size_guess < GUESS)
281 backup_suffix_size_guess = GUESS;
283 ssize = filelen + backup_suffix_size_guess + 1;
285 memcpy (s, file, filelen + 1);
287 if (backup_type != simple_backups)
288 switch (numbered_backup (&s, ssize, filelen))
290 case BACKUP_IS_SAME_LENGTH:
293 case BACKUP_IS_LONGER:
298 simple = (backup_type == numbered_existing_backups);
303 memcpy (s + filelen, simple_backup_suffix, simple_backup_suffix_size);
304 check_extension (s, filelen, '~');
308 static char const * const backup_args[] =
310 /* In a series of synonyms, present the most meaningful first, so
311 that argmatch_valid be more readable. */
319 static const enum backup_type backup_types[] =
321 no_backups, no_backups,
322 simple_backups, simple_backups,
323 numbered_existing_backups, numbered_existing_backups,
324 numbered_backups, numbered_backups
327 /* Ensure that these two vectors have the same number of elements,
328 not counting the final NULL in the first one. */
329 ARGMATCH_VERIFY (backup_args, backup_types);
331 /* Return the type of backup specified by VERSION.
332 If VERSION is NULL or the empty string, return numbered_existing_backups.
333 If VERSION is invalid or ambiguous, fail with a diagnostic appropriate
334 for the specified CONTEXT. Unambiguous abbreviations are accepted. */
337 get_version (char const *context, char const *version)
339 if (version == 0 || *version == 0)
340 return numbered_existing_backups;
342 return XARGMATCH (context, version, backup_args, backup_types);
346 /* Return the type of backup specified by VERSION.
347 If VERSION is NULL, use the value of the envvar VERSION_CONTROL.
348 If the specified string is invalid or ambiguous, fail with a diagnostic
349 appropriate for the specified CONTEXT.
350 Unambiguous abbreviations are accepted. */
353 xget_version (char const *context, char const *version)
355 if (version && *version)
356 return get_version (context, version);
358 return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));