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32676c08 | 1 | /* Copyright (C) 1985, 1986, 1987, 1992 Free Software Foundation, Inc. |
8489eb67 RS |
2 | |
3 | This file is part of GNU Emacs. | |
4 | ||
5 | GNU Emacs is free software; you can redistribute it and/or modify | |
6 | it under the terms of the GNU General Public License as published by | |
32676c08 | 7 | the Free Software Foundation; either version 2, or (at your option) |
8489eb67 RS |
8 | any later version. |
9 | ||
10 | GNU Emacs 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. | |
14 | ||
15 | You should have received a copy of the GNU General Public License | |
16 | along with GNU Emacs; see the file COPYING. If not, write to | |
17 | the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */ | |
18 | ||
19 | ||
20 | #include <sys/types.h> | |
21 | #include <sys/stat.h> | |
22 | #include "config.h" | |
bfb61299 JB |
23 | |
24 | #ifdef VMS | |
b350a838 | 25 | #include "vms-pwd.h" |
bfb61299 | 26 | #else |
8489eb67 | 27 | #include <pwd.h> |
bfb61299 JB |
28 | #endif |
29 | ||
8489eb67 RS |
30 | #include <errno.h> |
31 | #include <sys/file.h> | |
32 | #ifdef USG | |
33 | #include <fcntl.h> | |
34 | #endif /* USG */ | |
35 | ||
8489eb67 RS |
36 | #include "lisp.h" |
37 | #include "paths.h" | |
38 | #include "buffer.h" | |
39 | ||
40 | extern int errno; | |
41 | ||
32676c08 JB |
42 | extern char *egetenv (); |
43 | ||
8489eb67 RS |
44 | #ifdef CLASH_DETECTION |
45 | ||
46 | /* If system does not have symbolic links, it does not have lstat. | |
47 | In that case, use ordinary stat instead. */ | |
48 | ||
49 | #ifndef S_IFLNK | |
50 | #define lstat stat | |
51 | #endif | |
52 | ||
32676c08 JB |
53 | |
54 | /* The name of the directory in which we keep lock files, with a '/' | |
55 | appended. */ | |
56 | char *lock_path; | |
57 | ||
58 | /* The name of the file in the lock directory which is used to | |
59 | arbitrate access to the entire directory. */ | |
60 | #define SUPERLOCK_NAME "!!!SuperLock!!!" | |
61 | ||
62 | /* The path to the superlock file. This is SUPERLOCK_NAME appended to | |
63 | lock_path. */ | |
64 | char *superlock_path; | |
65 | ||
66 | /* Set LOCK to the name of the lock file for the filename FILE. | |
67 | char *LOCK; Lisp_Object FILE; */ | |
68 | #define MAKE_LOCK_PATH (lock, file) \ | |
69 | (lock = (char *) alloca (XSTRING (file)->size + strlen (lock_path) + 1), \ | |
70 | fill_in_lock_file_name (lock, (file))) | |
71 | ||
72 | fill_in_lock_file_name (lockfile, fn) | |
73 | register char *lockfile; | |
74 | register Lisp_Object fn; | |
75 | { | |
76 | register char *p; | |
77 | ||
78 | strcpy (lockfile, lock_path); | |
79 | ||
80 | p = lockfile + strlen (lockfile); | |
81 | ||
82 | strcpy (p, XSTRING (fn)->data); | |
83 | ||
84 | for (; *p; p++) | |
85 | { | |
86 | if (*p == '/') | |
87 | *p = '!'; | |
88 | } | |
89 | } | |
90 | ||
8489eb67 RS |
91 | static Lisp_Object |
92 | lock_file_owner_name (lfname) | |
93 | char *lfname; | |
94 | { | |
95 | struct stat s; | |
96 | struct passwd *the_pw; | |
97 | extern struct passwd *getpwuid (); | |
98 | ||
99 | if (lstat (lfname, &s) == 0) | |
100 | the_pw = getpwuid (s.st_uid); | |
101 | return (the_pw == 0 ? Qnil : build_string (the_pw->pw_name)); | |
102 | } | |
103 | ||
104 | ||
105 | /* lock_file locks file fn, | |
106 | meaning it serves notice on the world that you intend to edit that file. | |
107 | This should be done only when about to modify a file-visiting | |
108 | buffer previously unmodified. | |
109 | Do not (normally) call lock_buffer for a buffer already modified, | |
110 | as either the file is already locked, or the user has already | |
111 | decided to go ahead without locking. | |
112 | ||
113 | When lock_buffer returns, either the lock is locked for us, | |
114 | or the user has said to go ahead without locking. | |
115 | ||
116 | If the file is locked by someone else, lock_buffer calls | |
117 | ask-user-about-lock (a Lisp function) with two arguments, | |
118 | the file name and the name of the user who did the locking. | |
119 | This function can signal an error, or return t meaning | |
120 | take away the lock, or return nil meaning ignore the lock. */ | |
121 | ||
122 | /* The lock file name is the file name with "/" replaced by "!" | |
123 | and put in the Emacs lock directory. */ | |
124 | /* (ie., /ka/king/junk.tex -> /!/!ka!king!junk.tex). */ | |
125 | ||
126 | void | |
127 | lock_file (fn) | |
128 | register Lisp_Object fn; | |
129 | { | |
130 | register Lisp_Object attack; | |
131 | register char *lfname; | |
132 | ||
32676c08 | 133 | MAKE_LOCK_PATH (lfname, fn); |
8489eb67 | 134 | |
32676c08 JB |
135 | /* See if this file is visited and has changed on disk since it was |
136 | visited. */ | |
8489eb67 RS |
137 | { |
138 | register Lisp_Object subject_buf = Fget_file_buffer (fn); | |
265a9e55 JB |
139 | if (!NILP (subject_buf) |
140 | && NILP (Fverify_visited_file_modtime (subject_buf)) | |
141 | && !NILP (Ffile_exists_p (fn))) | |
8489eb67 RS |
142 | call1 (intern ("ask-user-about-supersession-threat"), fn); |
143 | } | |
144 | ||
145 | /* Try to lock the lock. */ | |
146 | if (lock_if_free (lfname) <= 0) | |
147 | /* Return now if we have locked it, or if lock dir does not exist */ | |
148 | return; | |
149 | ||
150 | /* Else consider breaking the lock */ | |
151 | attack = call2 (intern ("ask-user-about-lock"), fn, | |
152 | lock_file_owner_name (lfname)); | |
265a9e55 | 153 | if (!NILP (attack)) |
8489eb67 RS |
154 | /* User says take the lock */ |
155 | { | |
156 | lock_superlock (lfname); | |
157 | lock_file_1 (lfname, O_WRONLY) ; | |
32676c08 | 158 | unlink (superlock_path); |
8489eb67 RS |
159 | return; |
160 | } | |
161 | /* User says ignore the lock */ | |
162 | } | |
163 | ||
8489eb67 RS |
164 | /* Lock the lock file named LFNAME. |
165 | If MODE is O_WRONLY, we do so even if it is already locked. | |
166 | If MODE is O_WRONLY | O_EXCL | O_CREAT, we do so only if it is free. | |
167 | Return 1 if successful, 0 if not. */ | |
168 | ||
169 | int | |
170 | lock_file_1 (lfname, mode) | |
171 | int mode; char *lfname; | |
172 | { | |
173 | register int fd; | |
174 | char buf[20]; | |
175 | ||
176 | if ((fd = open (lfname, mode, 0666)) >= 0) | |
177 | { | |
178 | #ifdef USG | |
179 | chmod (lfname, 0666); | |
180 | #else | |
181 | fchmod (fd, 0666); | |
182 | #endif | |
183 | sprintf (buf, "%d ", getpid ()); | |
184 | write (fd, buf, strlen (buf)); | |
185 | close (fd); | |
186 | return 1; | |
187 | } | |
188 | else | |
189 | return 0; | |
190 | } | |
191 | ||
192 | /* Lock the lock named LFNAME if possible. | |
193 | Return 0 in that case. | |
194 | Return positive if lock is really locked by someone else. | |
195 | Return -1 if cannot lock for any other reason. */ | |
196 | ||
197 | int | |
198 | lock_if_free (lfname) | |
199 | register char *lfname; | |
200 | { | |
201 | register int clasher; | |
202 | ||
203 | while (lock_file_1 (lfname, O_WRONLY | O_EXCL | O_CREAT) == 0) | |
204 | { | |
205 | if (errno != EEXIST) | |
206 | return -1; | |
207 | clasher = current_lock_owner (lfname); | |
208 | if (clasher != 0) | |
209 | if (clasher != getpid ()) | |
210 | return (clasher); | |
211 | else return (0); | |
212 | /* Try again to lock it */ | |
213 | } | |
214 | return 0; | |
215 | } | |
216 | ||
217 | /* Return the pid of the process that claims to own the lock file LFNAME, | |
218 | or 0 if nobody does or the lock is obsolete, | |
219 | or -1 if something is wrong with the locking mechanism. */ | |
220 | ||
221 | int | |
222 | current_lock_owner (lfname) | |
223 | char *lfname; | |
224 | { | |
225 | int owner = current_lock_owner_1 (lfname); | |
226 | if (owner == 0 && errno == ENOENT) | |
227 | return (0); | |
228 | /* Is it locked by a process that exists? */ | |
229 | if (owner != 0 && (kill (owner, 0) >= 0 || errno == EPERM)) | |
230 | return (owner); | |
231 | if (unlink (lfname) < 0) | |
232 | return (-1); | |
233 | return (0); | |
234 | } | |
235 | ||
236 | int | |
237 | current_lock_owner_1 (lfname) | |
238 | char *lfname; | |
239 | { | |
240 | register int fd; | |
241 | char buf[20]; | |
242 | int tem; | |
243 | ||
244 | fd = open (lfname, O_RDONLY, 0666); | |
245 | if (fd < 0) | |
246 | return 0; | |
247 | tem = read (fd, buf, sizeof buf); | |
248 | close (fd); | |
249 | return (tem <= 0 ? 0 : atoi (buf)); | |
250 | } | |
251 | ||
252 | \f | |
253 | void | |
254 | unlock_file (fn) | |
255 | register Lisp_Object fn; | |
256 | { | |
257 | register char *lfname; | |
258 | ||
32676c08 | 259 | MAKE_LOCK_PATH (lfname, fn); |
8489eb67 RS |
260 | |
261 | lock_superlock (lfname); | |
262 | ||
263 | if (current_lock_owner_1 (lfname) == getpid ()) | |
264 | unlink (lfname); | |
265 | ||
32676c08 | 266 | unlink (superlock_path); |
8489eb67 RS |
267 | } |
268 | ||
269 | lock_superlock (lfname) | |
270 | char *lfname; | |
271 | { | |
272 | register int i, fd; | |
273 | ||
32676c08 | 274 | for (i = -20; i < 0 && (fd = open (superlock_path, |
8489eb67 RS |
275 | O_WRONLY | O_EXCL | O_CREAT, 0666)) < 0; |
276 | i++) | |
277 | { | |
278 | if (errno != EEXIST) | |
279 | return; | |
280 | sleep (1); | |
281 | } | |
282 | if (fd >= 0) | |
283 | { | |
284 | #ifdef USG | |
32676c08 | 285 | chmod (superlock_path, 0666); |
8489eb67 RS |
286 | #else |
287 | fchmod (fd, 0666); | |
288 | #endif | |
289 | write (fd, lfname, strlen (lfname)); | |
290 | close (fd); | |
291 | } | |
292 | } | |
293 | ||
294 | void | |
295 | unlock_all_files () | |
296 | { | |
297 | register Lisp_Object tail; | |
298 | register struct buffer *b; | |
299 | ||
300 | for (tail = Vbuffer_alist; XGCTYPE (tail) == Lisp_Cons; | |
301 | tail = XCONS (tail)->cdr) | |
302 | { | |
303 | b = XBUFFER (XCONS (XCONS (tail)->car)->cdr); | |
304 | if (XTYPE (b->filename) == Lisp_String && | |
305 | b->save_modified < BUF_MODIFF (b)) | |
306 | unlock_file (b->filename); | |
307 | } | |
308 | } | |
309 | ||
310 | \f | |
311 | DEFUN ("lock-buffer", Flock_buffer, Slock_buffer, | |
312 | 0, 1, 0, | |
313 | "Lock FILE, if current buffer is modified.\n\ | |
314 | FILE defaults to current buffer's visited file,\n\ | |
315 | or else nothing is done if current buffer isn't visiting a file.") | |
316 | (fn) | |
317 | Lisp_Object fn; | |
318 | { | |
265a9e55 | 319 | if (NILP (fn)) |
8489eb67 RS |
320 | fn = current_buffer->filename; |
321 | else | |
322 | CHECK_STRING (fn, 0); | |
323 | if (current_buffer->save_modified < MODIFF | |
265a9e55 | 324 | && !NILP (fn)) |
8489eb67 RS |
325 | lock_file (fn); |
326 | return Qnil; | |
327 | } | |
328 | ||
329 | DEFUN ("unlock-buffer", Funlock_buffer, Sunlock_buffer, | |
330 | 0, 0, 0, | |
331 | "Unlock the file visited in the current buffer,\n\ | |
332 | if it should normally be locked.") | |
333 | () | |
334 | { | |
335 | if (current_buffer->save_modified < MODIFF && | |
336 | XTYPE (current_buffer->filename) == Lisp_String) | |
337 | unlock_file (current_buffer->filename); | |
338 | return Qnil; | |
339 | } | |
340 | ||
341 | \f | |
342 | /* Unlock the file visited in buffer BUFFER. */ | |
343 | ||
344 | unlock_buffer (buffer) | |
345 | struct buffer *buffer; | |
346 | { | |
347 | if (buffer->save_modified < BUF_MODIFF (buffer) && | |
348 | XTYPE (buffer->filename) == Lisp_String) | |
349 | unlock_file (buffer->filename); | |
350 | } | |
351 | ||
352 | DEFUN ("file-locked-p", Ffile_locked_p, Sfile_locked_p, 0, 1, 0, | |
353 | "Return nil if the FILENAME is not locked,\n\ | |
354 | t if it is locked by you, else a string of the name of the locker.") | |
355 | (fn) | |
356 | Lisp_Object fn; | |
357 | { | |
358 | register char *lfname; | |
359 | int owner; | |
360 | ||
361 | fn = Fexpand_file_name (fn, Qnil); | |
362 | ||
32676c08 | 363 | MAKE_LOCK_PATH (lfname, fn); |
8489eb67 RS |
364 | |
365 | owner = current_lock_owner (lfname); | |
366 | if (owner <= 0) | |
367 | return (Qnil); | |
368 | else if (owner == getpid ()) | |
369 | return (Qt); | |
370 | ||
371 | return (lock_file_owner_name (lfname)); | |
372 | } | |
373 | ||
32676c08 JB |
374 | \f |
375 | /* Initialization functions. */ | |
376 | ||
377 | init_filelock () | |
378 | { | |
379 | lock_path = egetenv ("EMACSLOCKDIR"); | |
380 | if (! lock_path) | |
381 | lock_path = PATH_LOCK; | |
382 | ||
383 | /* Make sure it ends with a slash. */ | |
384 | if (lock_path[strlen (lock_path) - 1] != '/') | |
385 | { | |
386 | lock_path = strcpy ((char *) xmalloc (strlen (lock_path) + 2), | |
387 | lock_path); | |
388 | strcat (lock_path, "/"); | |
389 | } | |
390 | ||
391 | superlock_path = (char *) xmalloc ((strlen (lock_path) | |
392 | + sizeof (SUPERLOCK_NAME))); | |
393 | strcpy (superlock_path, lock_path); | |
394 | strcat (superlock_path, SUPERLOCK_NAME); | |
395 | } | |
396 | ||
8489eb67 RS |
397 | syms_of_filelock () |
398 | { | |
399 | defsubr (&Sunlock_buffer); | |
400 | defsubr (&Slock_buffer); | |
401 | defsubr (&Sfile_locked_p); | |
402 | } | |
403 | ||
404 | #endif /* CLASH_DETECTION */ |