Line data Source code
1 : /* backupfile.c -- make Emacs style backup file names
2 :
3 : Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
4 : 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software
5 : Foundation, Inc.
6 :
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 3 of the License, or
10 : (at your option) any later version.
11 :
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.
16 :
17 : You should have received a copy of the GNU General Public License
18 : along with this program. If not, see <http://www.gnu.org/licenses/>. */
19 :
20 : /* Written by Paul Eggert and David MacKenzie.
21 : Some algorithms adapted from GNU Emacs. */
22 :
23 : #include <config.h>
24 :
25 : #include "backupfile.h"
26 :
27 : #include "argmatch.h"
28 : #include "dirname.h"
29 : #include "xalloc.h"
30 :
31 : #include <errno.h>
32 : #include <stdbool.h>
33 : #include <stdlib.h>
34 : #include <string.h>
35 :
36 : #include <limits.h>
37 :
38 : #include <unistd.h>
39 :
40 : #include <dirent.h>
41 : #ifndef _D_EXACT_NAMLEN
42 : # define _D_EXACT_NAMLEN(dp) strlen ((dp)->d_name)
43 : #endif
44 : #if D_INO_IN_DIRENT
45 : # define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
46 : #else
47 : # define REAL_DIR_ENTRY(dp) 1
48 : #endif
49 :
50 : #if ! (HAVE_PATHCONF && defined _PC_NAME_MAX)
51 : # define pathconf(file, option) (errno = -1)
52 : #endif
53 :
54 : #ifndef _POSIX_NAME_MAX
55 : # define _POSIX_NAME_MAX 14
56 : #endif
57 : #ifndef SIZE_MAX
58 : # define SIZE_MAX ((size_t) -1)
59 : #endif
60 :
61 : #if defined _XOPEN_NAME_MAX
62 : # define NAME_MAX_MINIMUM _XOPEN_NAME_MAX
63 : #else
64 : # define NAME_MAX_MINIMUM _POSIX_NAME_MAX
65 : #endif
66 :
67 : #ifndef HAVE_DOS_FILE_NAMES
68 : # define HAVE_DOS_FILE_NAMES 0
69 : #endif
70 : #ifndef HAVE_LONG_FILE_NAMES
71 : # define HAVE_LONG_FILE_NAMES 0
72 : #endif
73 :
74 : /* ISDIGIT differs from isdigit, as follows:
75 : - Its arg may be any int or unsigned int; it need not be an unsigned char
76 : or EOF.
77 : - It's typically faster.
78 : POSIX says that only '0' through '9' are digits. Prefer ISDIGIT to
79 : ISDIGIT unless it's important to use the locale's definition
80 : of `digit' even when the host does not conform to POSIX. */
81 : #define ISDIGIT(c) ((unsigned int) (c) - '0' <= 9)
82 :
83 : /* The results of opendir() in this file are not used with dirfd and fchdir,
84 : therefore save some unnecessary work in fchdir.c. */
85 : #undef opendir
86 : #undef closedir
87 :
88 : /* The extension added to file names to produce a simple (as opposed
89 : to numbered) backup file name. */
90 : char const *simple_backup_suffix = "~";
91 :
92 :
93 : /* If FILE (which was of length FILELEN before an extension was
94 : appended to it) is too long, replace the extension with the single
95 : char E. If the result is still too long, remove the char just
96 : before E. */
97 :
98 : static void
99 13 : check_extension (char *file, size_t filelen, char e)
100 : {
101 13 : char *base = last_component (file);
102 13 : size_t baselen = base_len (base);
103 13 : size_t baselen_max = HAVE_LONG_FILE_NAMES ? 255 : NAME_MAX_MINIMUM;
104 :
105 13 : if (HAVE_DOS_FILE_NAMES || NAME_MAX_MINIMUM < baselen)
106 : {
107 : /* The new base name is long enough to require a pathconf check. */
108 : long name_max;
109 :
110 : /* Temporarily modify the buffer into its parent directory name,
111 : invoke pathconf on the directory, and then restore the buffer. */
112 : char tmp[sizeof "."];
113 0 : memcpy (tmp, base, sizeof ".");
114 0 : strcpy (base, ".");
115 0 : errno = 0;
116 0 : name_max = pathconf (file, _PC_NAME_MAX);
117 0 : if (0 <= name_max || errno == 0)
118 : {
119 0 : long size = baselen_max = name_max;
120 0 : if (name_max != size)
121 0 : baselen_max = SIZE_MAX;
122 : }
123 0 : memcpy (base, tmp, sizeof ".");
124 : }
125 :
126 : if (HAVE_DOS_FILE_NAMES && baselen_max <= 12)
127 : {
128 : /* Live within DOS's 8.3 limit. */
129 : char *dot = strchr (base, '.');
130 : if (!dot)
131 : baselen_max = 8;
132 : else
133 : {
134 : char const *second_dot = strchr (dot + 1, '.');
135 : baselen_max = (second_dot
136 : ? second_dot - base
137 : : dot + 1 - base + 3);
138 : }
139 : }
140 :
141 13 : if (baselen_max < baselen)
142 : {
143 0 : baselen = file + filelen - base;
144 0 : if (baselen_max <= baselen)
145 0 : baselen = baselen_max - 1;
146 0 : base[baselen] = e;
147 0 : base[baselen + 1] = '\0';
148 : }
149 13 : }
150 :
151 : /* Returned values for NUMBERED_BACKUP. */
152 :
153 : enum numbered_backup_result
154 : {
155 : /* The new backup name is the same length as an existing backup
156 : name, so it's valid for that directory. */
157 : BACKUP_IS_SAME_LENGTH,
158 :
159 : /* Some backup names already exist, but the returned name is longer
160 : than any of them, and its length should be checked. */
161 : BACKUP_IS_LONGER,
162 :
163 : /* There are no existing backup names. The new name's length
164 : should be checked. */
165 : BACKUP_IS_NEW
166 : };
167 :
168 : /* *BUFFER contains a file name. Store into *BUFFER the next backup
169 : name for the named file, with a version number greater than all the
170 : existing numbered backups. Reallocate *BUFFER as necessary; its
171 : initial allocated size is BUFFER_SIZE, which must be at least 4
172 : bytes longer than the file name to make room for the initially
173 : appended ".~1". FILELEN is the length of the original file name.
174 : The returned value indicates what kind of backup was found. If an
175 : I/O or other read error occurs, use the highest backup number that
176 : was found. */
177 :
178 : static enum numbered_backup_result
179 11 : numbered_backup (char **buffer, size_t buffer_size, size_t filelen)
180 : {
181 11 : enum numbered_backup_result result = BACKUP_IS_NEW;
182 : DIR *dirp;
183 : struct dirent *dp;
184 11 : char *buf = *buffer;
185 11 : size_t versionlenmax = 1;
186 11 : char *base = last_component (buf);
187 11 : size_t base_offset = base - buf;
188 11 : size_t baselen = base_len (base);
189 :
190 : /* Temporarily modify the buffer into its parent directory name,
191 : open the directory, and then restore the buffer. */
192 : char tmp[sizeof "."];
193 11 : memcpy (tmp, base, sizeof ".");
194 11 : strcpy (base, ".");
195 11 : dirp = opendir (buf);
196 11 : memcpy (base, tmp, sizeof ".");
197 11 : strcpy (base + baselen, ".~1~");
198 :
199 11 : if (!dirp)
200 0 : return result;
201 :
202 4025 : while ((dp = readdir (dirp)) != NULL)
203 : {
204 : char const *p;
205 : char *q;
206 : bool all_9s;
207 : size_t versionlen;
208 : size_t new_buflen;
209 :
210 4003 : if (! REAL_DIR_ENTRY (dp) || _D_EXACT_NAMLEN (dp) < baselen + 4)
211 1030 : continue;
212 :
213 2973 : if (memcmp (buf + base_offset, dp->d_name, baselen + 2) != 0)
214 2973 : continue;
215 :
216 0 : p = dp->d_name + baselen + 2;
217 :
218 : /* Check whether this file has a version number and if so,
219 : whether it is larger. Use string operations rather than
220 : integer arithmetic, to avoid problems with integer overflow. */
221 :
222 0 : if (! ('1' <= *p && *p <= '9'))
223 0 : continue;
224 0 : all_9s = (*p == '9');
225 0 : for (versionlen = 1; ISDIGIT (p[versionlen]); versionlen++)
226 0 : all_9s &= (p[versionlen] == '9');
227 :
228 0 : if (! (p[versionlen] == '~' && !p[versionlen + 1]
229 : && (versionlenmax < versionlen
230 0 : || (versionlenmax == versionlen
231 0 : && memcmp (buf + filelen + 2, p, versionlen) <= 0))))
232 0 : continue;
233 :
234 : /* This directory has the largest version number seen so far.
235 : Append this highest numbered extension to the file name,
236 : prepending '0' to the number if it is all 9s. */
237 :
238 0 : versionlenmax = all_9s + versionlen;
239 0 : result = (all_9s ? BACKUP_IS_LONGER : BACKUP_IS_SAME_LENGTH);
240 0 : new_buflen = filelen + 2 + versionlenmax + 1;
241 0 : if (buffer_size <= new_buflen)
242 : {
243 0 : buf = xnrealloc (buf, 2, new_buflen);
244 0 : buffer_size = new_buflen * 2;
245 : }
246 0 : q = buf + filelen;
247 0 : *q++ = '.';
248 0 : *q++ = '~';
249 0 : *q = '0';
250 0 : q += all_9s;
251 0 : memcpy (q, p, versionlen + 2);
252 :
253 : /* Add 1 to the version number. */
254 :
255 0 : q += versionlen;
256 0 : while (*--q == '9')
257 0 : *q = '0';
258 0 : ++*q;
259 : }
260 :
261 11 : closedir (dirp);
262 11 : *buffer = buf;
263 11 : return result;
264 : }
265 :
266 : /* Return the name of the new backup file for the existing file FILE,
267 : allocated with malloc. Report an error and fail if out of memory.
268 : Do not call this function if backup_type == no_backups. */
269 :
270 : char *
271 13 : find_backup_file_name (char const *file, enum backup_type backup_type)
272 : {
273 13 : size_t filelen = strlen (file);
274 : char *s;
275 : size_t ssize;
276 13 : bool simple = true;
277 :
278 : /* Allow room for simple or ".~N~" backups. The guess must be at
279 : least sizeof ".~1~", but otherwise will be adjusted as needed. */
280 13 : size_t simple_backup_suffix_size = strlen (simple_backup_suffix) + 1;
281 13 : size_t backup_suffix_size_guess = simple_backup_suffix_size;
282 : enum { GUESS = sizeof ".~12345~" };
283 13 : if (backup_suffix_size_guess < GUESS)
284 13 : backup_suffix_size_guess = GUESS;
285 :
286 13 : ssize = filelen + backup_suffix_size_guess + 1;
287 13 : s = xmalloc (ssize);
288 13 : memcpy (s, file, filelen + 1);
289 :
290 13 : if (backup_type != simple_backups)
291 11 : switch (numbered_backup (&s, ssize, filelen))
292 : {
293 0 : case BACKUP_IS_SAME_LENGTH:
294 0 : return s;
295 :
296 0 : case BACKUP_IS_LONGER:
297 0 : simple = false;
298 0 : break;
299 :
300 11 : case BACKUP_IS_NEW:
301 11 : simple = (backup_type == numbered_existing_backups);
302 11 : break;
303 : }
304 :
305 13 : if (simple)
306 13 : memcpy (s + filelen, simple_backup_suffix, simple_backup_suffix_size);
307 13 : check_extension (s, filelen, '~');
308 13 : return s;
309 : }
310 :
311 : static char const * const backup_args[] =
312 : {
313 : /* In a series of synonyms, present the most meaningful first, so
314 : that argmatch_valid be more readable. */
315 : "none", "off",
316 : "simple", "never",
317 : "existing", "nil",
318 : "numbered", "t",
319 : NULL
320 : };
321 :
322 : static const enum backup_type backup_types[] =
323 : {
324 : no_backups, no_backups,
325 : simple_backups, simple_backups,
326 : numbered_existing_backups, numbered_existing_backups,
327 : numbered_backups, numbered_backups
328 : };
329 :
330 : /* Ensure that these two vectors have the same number of elements,
331 : not counting the final NULL in the first one. */
332 : ARGMATCH_VERIFY (backup_args, backup_types);
333 :
334 : /* Return the type of backup specified by VERSION.
335 : If VERSION is NULL or the empty string, return numbered_existing_backups.
336 : If VERSION is invalid or ambiguous, fail with a diagnostic appropriate
337 : for the specified CONTEXT. Unambiguous abbreviations are accepted. */
338 :
339 : enum backup_type
340 73 : get_version (char const *context, char const *version)
341 : {
342 73 : if (version == 0 || *version == 0)
343 53 : return numbered_existing_backups;
344 : else
345 20 : return XARGMATCH (context, version, backup_args, backup_types);
346 : }
347 :
348 :
349 : /* Return the type of backup specified by VERSION.
350 : If VERSION is NULL, use the value of the envvar VERSION_CONTROL.
351 : If the specified string is invalid or ambiguous, fail with a diagnostic
352 : appropriate for the specified CONTEXT.
353 : Unambiguous abbreviations are accepted. */
354 :
355 : enum backup_type
356 73 : xget_version (char const *context, char const *version)
357 : {
358 73 : if (version && *version)
359 20 : return get_version (context, version);
360 : else
361 53 : return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));
362 : }
|
