1 /* backupfile.c -- make Emacs style backup file names
3 Copyright (C) 1990-2006, 2009-2010 Free Software Foundation, Inc.
5 This program is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>. */
18 /* Written by Paul Eggert and David MacKenzie.
19 Some algorithms adapted from GNU Emacs. */
23 #include "backupfile.h"
39 #ifndef _D_EXACT_NAMLEN
40 # define _D_EXACT_NAMLEN(dp) strlen ((dp)->d_name)
43 # define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
45 # define REAL_DIR_ENTRY(dp) 1
48 #if ! (HAVE_PATHCONF && defined _PC_NAME_MAX)
49 # define pathconf(file, option) (errno = -1)
52 #ifndef _POSIX_NAME_MAX
53 # define _POSIX_NAME_MAX 14
56 # define SIZE_MAX ((size_t) -1)
59 #if defined _XOPEN_NAME_MAX
60 # define NAME_MAX_MINIMUM _XOPEN_NAME_MAX
62 # define NAME_MAX_MINIMUM _POSIX_NAME_MAX
65 #ifndef HAVE_DOS_FILE_NAMES
66 # define HAVE_DOS_FILE_NAMES 0
68 #ifndef HAVE_LONG_FILE_NAMES
69 # define HAVE_LONG_FILE_NAMES 0
72 /* ISDIGIT differs from isdigit, as follows:
73 - Its arg may be any int or unsigned int; it need not be an unsigned char
75 - It's typically faster.
76 POSIX says that only '0' through '9' are digits. Prefer ISDIGIT to
77 ISDIGIT unless it's important to use the locale's definition
78 of `digit' even when the host does not conform to POSIX. */
79 #define ISDIGIT(c) ((unsigned int) (c) - '0' <= 9)
81 /* The extension added to file names to produce a simple (as opposed
82 to numbered) backup file name. */
83 char const *simple_backup_suffix = "~";
86 /* If FILE (which was of length FILELEN before an extension was
87 appended to it) is too long, replace the extension with the single
88 char E. If the result is still too long, remove the char just
92 check_extension (char *file, size_t filelen, char e)
94 char *base = last_component (file);
95 size_t baselen = base_len (base);
96 size_t baselen_max = HAVE_LONG_FILE_NAMES ? 255 : NAME_MAX_MINIMUM;
98 if (HAVE_DOS_FILE_NAMES || NAME_MAX_MINIMUM < baselen)
100 /* The new base name is long enough to require a pathconf check. */
103 /* Temporarily modify the buffer into its parent directory name,
104 invoke pathconf on the directory, and then restore the buffer. */
105 char tmp[sizeof "."];
106 memcpy (tmp, base, sizeof ".");
109 name_max = pathconf (file, _PC_NAME_MAX);
110 if (0 <= name_max || errno == 0)
112 long size = baselen_max = name_max;
113 if (name_max != size)
114 baselen_max = SIZE_MAX;
116 memcpy (base, tmp, sizeof ".");
119 if (HAVE_DOS_FILE_NAMES && baselen_max <= 12)
121 /* Live within DOS's 8.3 limit. */
122 char *dot = strchr (base, '.');
127 char const *second_dot = strchr (dot + 1, '.');
128 baselen_max = (second_dot
130 : dot + 1 - base + 3);
134 if (baselen_max < baselen)
136 baselen = file + filelen - base;
137 if (baselen_max <= baselen)
138 baselen = baselen_max - 1;
140 base[baselen + 1] = '\0';
144 /* Returned values for NUMBERED_BACKUP. */
146 enum numbered_backup_result
148 /* The new backup name is the same length as an existing backup
149 name, so it's valid for that directory. */
150 BACKUP_IS_SAME_LENGTH,
152 /* Some backup names already exist, but the returned name is longer
153 than any of them, and its length should be checked. */
156 /* There are no existing backup names. The new name's length
157 should be checked. */
161 /* *BUFFER contains a file name. Store into *BUFFER the next backup
162 name for the named file, with a version number greater than all the
163 existing numbered backups. Reallocate *BUFFER as necessary; its
164 initial allocated size is BUFFER_SIZE, which must be at least 4
165 bytes longer than the file name to make room for the initially
166 appended ".~1". FILELEN is the length of the original file name.
167 The returned value indicates what kind of backup was found. If an
168 I/O or other read error occurs, use the highest backup number that
171 static enum numbered_backup_result
172 numbered_backup (char **buffer, size_t buffer_size, size_t filelen)
174 enum numbered_backup_result result = BACKUP_IS_NEW;
178 size_t versionlenmax = 1;
179 char *base = last_component (buf);
180 size_t base_offset = base - buf;
181 size_t baselen = base_len (base);
183 /* Temporarily modify the buffer into its parent directory name,
184 open the directory, and then restore the buffer. */
185 char tmp[sizeof "."];
186 memcpy (tmp, base, sizeof ".");
188 dirp = opendir (buf);
189 memcpy (base, tmp, sizeof ".");
190 strcpy (base + baselen, ".~1~");
195 while ((dp = readdir (dirp)) != NULL)
203 if (! REAL_DIR_ENTRY (dp) || _D_EXACT_NAMLEN (dp) < baselen + 4)
206 if (memcmp (buf + base_offset, dp->d_name, baselen + 2) != 0)
209 p = dp->d_name + baselen + 2;
211 /* Check whether this file has a version number and if so,
212 whether it is larger. Use string operations rather than
213 integer arithmetic, to avoid problems with integer overflow. */
215 if (! ('1' <= *p && *p <= '9'))
217 all_9s = (*p == '9');
218 for (versionlen = 1; ISDIGIT (p[versionlen]); versionlen++)
219 all_9s &= (p[versionlen] == '9');
221 if (! (p[versionlen] == '~' && !p[versionlen + 1]
222 && (versionlenmax < versionlen
223 || (versionlenmax == versionlen
224 && memcmp (buf + filelen + 2, p, versionlen) <= 0))))
227 /* This directory has the largest version number seen so far.
228 Append this highest numbered extension to the file name,
229 prepending '0' to the number if it is all 9s. */
231 versionlenmax = all_9s + versionlen;
232 result = (all_9s ? BACKUP_IS_LONGER : BACKUP_IS_SAME_LENGTH);
233 new_buflen = filelen + 2 + versionlenmax + 1;
234 if (buffer_size <= new_buflen)
236 buf = xnrealloc (buf, 2, new_buflen);
237 buffer_size = new_buflen * 2;
244 memcpy (q, p, versionlen + 2);
246 /* Add 1 to the version number. */
259 /* Return the name of the new backup file for the existing file FILE,
260 allocated with malloc. Report an error and fail if out of memory.
261 Do not call this function if backup_type == no_backups. */
264 find_backup_file_name (char const *file, enum backup_type backup_type)
266 size_t filelen = strlen (file);
271 /* Allow room for simple or ".~N~" backups. The guess must be at
272 least sizeof ".~1~", but otherwise will be adjusted as needed. */
273 size_t simple_backup_suffix_size = strlen (simple_backup_suffix) + 1;
274 size_t backup_suffix_size_guess = simple_backup_suffix_size;
275 enum { GUESS = sizeof ".~12345~" };
276 if (backup_suffix_size_guess < GUESS)
277 backup_suffix_size_guess = GUESS;
279 ssize = filelen + backup_suffix_size_guess + 1;
281 memcpy (s, file, filelen + 1);
283 if (backup_type != simple_backups)
284 switch (numbered_backup (&s, ssize, filelen))
286 case BACKUP_IS_SAME_LENGTH:
289 case BACKUP_IS_LONGER:
294 simple = (backup_type == numbered_existing_backups);
299 memcpy (s + filelen, simple_backup_suffix, simple_backup_suffix_size);
300 check_extension (s, filelen, '~');
304 static char const * const backup_args[] =
306 /* In a series of synonyms, present the most meaningful first, so
307 that argmatch_valid be more readable. */
315 static const enum backup_type backup_types[] =
317 no_backups, no_backups,
318 simple_backups, simple_backups,
319 numbered_existing_backups, numbered_existing_backups,
320 numbered_backups, numbered_backups
323 /* Ensure that these two vectors have the same number of elements,
324 not counting the final NULL in the first one. */
325 ARGMATCH_VERIFY (backup_args, backup_types);
327 /* Return the type of backup specified by VERSION.
328 If VERSION is NULL or the empty string, return numbered_existing_backups.
329 If VERSION is invalid or ambiguous, fail with a diagnostic appropriate
330 for the specified CONTEXT. Unambiguous abbreviations are accepted. */
333 get_version (char const *context, char const *version)
335 if (version == 0 || *version == 0)
336 return numbered_existing_backups;
338 return XARGMATCH (context, version, backup_args, backup_types);
342 /* Return the type of backup specified by VERSION.
343 If VERSION is NULL, use the value of the envvar VERSION_CONTROL.
344 If the specified string is invalid or ambiguous, fail with a diagnostic
345 appropriate for the specified CONTEXT.
346 Unambiguous abbreviations are accepted. */
349 xget_version (char const *context, char const *version)
351 if (version && *version)
352 return get_version (context, version);
354 return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));