Commit | Line | Data |
---|---|---|
8dbbc384 | 1 | /* Copyright (C) 1985, 86, 87, 93, 94, 96 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 | |
3b7ad313 EN |
17 | the Free Software Foundation, Inc., 59 Temple Place - Suite 330, |
18 | Boston, MA 02111-1307, USA. */ | |
8489eb67 RS |
19 | |
20 | ||
21 | #include <sys/types.h> | |
22 | #include <sys/stat.h> | |
18160b98 | 23 | #include <config.h> |
bfb61299 JB |
24 | |
25 | #ifdef VMS | |
b350a838 | 26 | #include "vms-pwd.h" |
bfb61299 | 27 | #else |
8489eb67 | 28 | #include <pwd.h> |
8dbbc384 | 29 | #endif /* not VMS */ |
bfb61299 | 30 | |
8489eb67 RS |
31 | #include <sys/file.h> |
32 | #ifdef USG | |
33 | #include <fcntl.h> | |
8dbbc384 | 34 | #include <string.h> |
8489eb67 RS |
35 | #endif /* USG */ |
36 | ||
8489eb67 | 37 | #include "lisp.h" |
8489eb67 RS |
38 | #include "buffer.h" |
39 | ||
8dbbc384 RS |
40 | #include <errno.h> |
41 | #ifndef errno | |
8489eb67 | 42 | extern int errno; |
79941276 RS |
43 | #endif |
44 | ||
8489eb67 RS |
45 | #ifdef CLASH_DETECTION |
46 | ||
8dbbc384 RS |
47 | /* The strategy: to lock a file FN, create a symlink .#FN in FN's |
48 | directory, with link data `user@host.pid'. This avoids a single | |
49 | mount (== failure) point for lock files. | |
50 | ||
51 | When the host in the lock data is the current host, we can check if | |
52 | the pid is valid with kill. | |
53 | ||
54 | Otherwise, we could look at a separate file that maps hostnames to | |
55 | reboot times to see if the remote pid can possibly be valid, since we | |
56 | don't want Emacs to have to communicate via pipes or sockets or | |
57 | whatever to other processes, either locally or remotely; rms says | |
58 | that's too unreliable. Hence the separate file, which could | |
59 | theoretically be updated by daemons running separately -- but this | |
60 | whole idea is unimplemented; in practice, at least in our | |
61 | environment, it seems such stale locks arise fiarly infrequently, and | |
62 | Emacs' standard methods of dealing with clashes suffice. | |
63 | ||
64 | We use symlinks instead of normal files because (1) they can be | |
65 | stored more efficiently on the filesystem, since the kernel knows | |
66 | they will be small, and (2) all the info about the lock can be read | |
67 | in a single system call (readlink). Although we could use regular | |
68 | files to be useful on old systems lacking symlinks, noawdays | |
69 | virtually all such systems are probably single-user anyway, so it | |
70 | didn't seem worth the complication. | |
71 | ||
72 | Similarly, we don't worry about a possible 14-character limit on | |
73 | file names, because those are all the same systems that don't have | |
74 | symlinks. | |
75 | ||
76 | This is compatible with the locking scheme used by Interleaf (which | |
77 | has contributed this implementation for Emacs), and was designed by | |
78 | Ethan Jacobson, Kimbo Mundy, and others. | |
79 | ||
80 | --karl@cs.umb.edu/karl@hq.ileaf.com. */ | |
8489eb67 | 81 | |
8dbbc384 RS |
82 | \f |
83 | /* Here is the structure that stores information about a lock. */ | |
32676c08 | 84 | |
8dbbc384 RS |
85 | typedef struct |
86 | { | |
87 | char *user; | |
88 | char *host; | |
9005cb4f | 89 | unsigned long pid; |
8dbbc384 | 90 | } lock_info_type; |
32676c08 | 91 | |
8dbbc384 RS |
92 | /* When we read the info back, we might need this much more. */ |
93 | #define LOCK_PID_MAX 21 /* enough for signed 64 bits plus null */ | |
32676c08 | 94 | |
8dbbc384 RS |
95 | /* Free the two dynamically-allocated pieces in PTR. */ |
96 | #define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0) | |
e31fbc7a | 97 | |
e31fbc7a | 98 | |
8dbbc384 RS |
99 | /* Write the name of the lock file for FN into LFNAME. Length will be |
100 | that of FN plus two more for the leading `.#' plus one for the null. */ | |
7b92975f | 101 | #define MAKE_LOCK_NAME(lock, file) \ |
8dbbc384 RS |
102 | (lock = (char *) alloca (XSTRING (file)->size + 2 + 1), \ |
103 | fill_in_lock_file_name (lock, (file))) | |
e31fbc7a | 104 | |
8dbbc384 RS |
105 | static void |
106 | fill_in_lock_file_name (lockfile, fn) | |
e31fbc7a RS |
107 | register char *lockfile; |
108 | register Lisp_Object fn; | |
109 | { | |
8dbbc384 RS |
110 | register char *p; |
111 | ||
112 | strcpy (lockfile, XSTRING (fn)->data); | |
113 | ||
114 | /* Shift the nondirectory part of the file name (including the null) | |
115 | right two characters. Here is one of the places where we'd have to | |
116 | do something to support 14-character-max file names. */ | |
117 | for (p = lockfile + strlen (lockfile); p != lockfile && *p != '/'; p--) | |
118 | p[2] = *p; | |
e31fbc7a | 119 | |
8dbbc384 RS |
120 | /* Insert the `.#'. */ |
121 | p[1] = '.'; | |
122 | p[2] = '#'; | |
123 | } | |
e31fbc7a | 124 | |
8dbbc384 RS |
125 | /* Lock the lock file named LFNAME. |
126 | If FORCE is nonzero, we do so even if it is already locked. | |
127 | Return 1 if successful, 0 if not. */ | |
e31fbc7a | 128 | |
8dbbc384 RS |
129 | static int |
130 | lock_file_1 (lfname, force) | |
131 | char *lfname; | |
132 | int force; | |
133 | { | |
134 | register int err; | |
135 | char *user_name = XSTRING (Fuser_login_name (Qnil))->data; | |
136 | char *host_name = XSTRING (Fsystem_name ())->data; | |
137 | char *lock_info_str = alloca (strlen (user_name) + strlen (host_name) + 21); | |
138 | ||
9005cb4f RS |
139 | sprintf (lock_info_str, "%s@%s.%lu", user_name, host_name, |
140 | (unsigned long) getpid ()); | |
8dbbc384 RS |
141 | |
142 | err = symlink (lock_info_str, lfname); | |
143 | if (errno == EEXIST && force) | |
e31fbc7a | 144 | { |
8dbbc384 RS |
145 | unlink (lfname); |
146 | err = symlink (lock_info_str, lfname); | |
e31fbc7a | 147 | } |
e31fbc7a | 148 | |
8dbbc384 RS |
149 | return err == 0; |
150 | } | |
e31fbc7a | 151 | |
32676c08 | 152 | |
8dbbc384 RS |
153 | \f |
154 | /* Return 0 if nobody owns the lock file LFNAME or the lock is obsolete, | |
155 | 1 if another process owns it (and set OWNER (if non-null) to info), | |
156 | 2 if the current process owns it, | |
157 | or -1 if something is wrong with the locking mechanism. */ | |
e31fbc7a | 158 | |
8dbbc384 RS |
159 | static int |
160 | current_lock_owner (owner, lfname) | |
161 | lock_info_type *owner; | |
162 | char *lfname; | |
32676c08 | 163 | { |
8dbbc384 RS |
164 | #ifndef index |
165 | extern char *rindex (), *index (); | |
166 | #endif | |
167 | int o, p, len, ret; | |
168 | int local_owner = 0; | |
169 | char *at, *dot; | |
170 | char *lfinfo = 0; | |
171 | int bufsize = 50; | |
172 | /* Read arbitrarily-long contents of symlink. Similar code in | |
173 | file-symlink-p in fileio.c. */ | |
174 | do | |
175 | { | |
176 | bufsize *= 2; | |
177 | lfinfo = (char *) xrealloc (lfinfo, bufsize); | |
178 | len = readlink (lfname, lfinfo, bufsize); | |
179 | } | |
180 | while (len >= bufsize); | |
181 | ||
182 | /* If nonexistent lock file, all is well; otherwise, got strange error. */ | |
183 | if (len == -1) | |
184 | { | |
185 | xfree (lfinfo); | |
186 | return errno == ENOENT ? 0 : -1; | |
187 | } | |
32676c08 | 188 | |
8dbbc384 RS |
189 | /* Link info exists, so `len' is its length. Null terminate. */ |
190 | lfinfo[len] = 0; | |
191 | ||
192 | /* Even if the caller doesn't want the owner info, we still have to | |
193 | read it to determine return value, so allocate it. */ | |
194 | if (!owner) | |
195 | { | |
196 | owner = alloca (sizeof (lock_info_type)); | |
197 | local_owner = 1; | |
198 | } | |
199 | ||
200 | /* Parse USER@HOST.PID. If can't parse, return -1. */ | |
201 | /* The USER is everything before the first @. */ | |
202 | at = index (lfinfo, '@'); | |
203 | dot = rindex (lfinfo, '.'); | |
204 | if (!at || !dot) { | |
205 | xfree (lfinfo); | |
206 | return -1; | |
207 | } | |
208 | len = at - lfinfo; | |
209 | owner->user = (char *) xmalloc (len + 1); | |
210 | strncpy (owner->user, lfinfo, len); | |
211 | owner->user[len] = 0; | |
212 | ||
213 | /* The PID is everything after the last `.'. */ | |
214 | owner->pid = atoi (dot + 1); | |
32676c08 | 215 | |
8dbbc384 RS |
216 | /* The host is everything in between. */ |
217 | len = dot - at - 1; | |
218 | owner->host = (char *) xmalloc (len + 1); | |
219 | strncpy (owner->host, at + 1, len); | |
220 | owner->host[len] = 0; | |
32676c08 | 221 | |
8dbbc384 RS |
222 | /* We're done looking at the link info. */ |
223 | xfree (lfinfo); | |
224 | ||
225 | /* On current host? */ | |
226 | if (strcmp (owner->host, XSTRING (Fsystem_name ())->data) == 0) | |
32676c08 | 227 | { |
8dbbc384 RS |
228 | if (owner->pid == getpid ()) |
229 | ret = 2; /* We own it. */ | |
230 | ||
231 | if (owner->pid > 0 | |
232 | && (kill (owner->pid, 0) >= 0 || errno == EPERM)) | |
233 | ret = 1; /* An existing process on this machine owns it. */ | |
234 | ||
235 | /* The owner process is dead or has a strange pid (<=0), so try to | |
236 | zap the lockfile. */ | |
237 | if (unlink (lfname) < 0) | |
238 | ret = -1; | |
239 | ||
240 | ret = 0; | |
32676c08 | 241 | } |
8dbbc384 RS |
242 | else |
243 | { /* If we wanted to support the check for stale locks on remote machines, | |
244 | here's where we'd do it. */ | |
245 | ret = 1; | |
246 | } | |
247 | ||
248 | /* Avoid garbage. */ | |
249 | if (local_owner || ret <= 0) | |
250 | { | |
251 | FREE_LOCK_INFO (*owner); | |
252 | } | |
253 | return ret; | |
32676c08 JB |
254 | } |
255 | ||
8dbbc384 RS |
256 | \f |
257 | /* Lock the lock named LFNAME if possible. | |
258 | Return 0 in that case. | |
259 | Return positive if some other process owns the lock, and info about | |
260 | that process in CLASHER. | |
261 | Return -1 if cannot lock for any other reason. */ | |
8489eb67 | 262 | |
8dbbc384 RS |
263 | static int |
264 | lock_if_free (clasher, lfname) | |
265 | lock_info_type *clasher; | |
266 | register char *lfname; | |
267 | { | |
268 | while (lock_file_1 (lfname, 0) == 0) | |
269 | { | |
270 | int locker; | |
e0e0205b | 271 | |
8dbbc384 RS |
272 | if (errno != EEXIST) |
273 | return -1; | |
274 | ||
275 | locker = current_lock_owner (clasher, lfname); | |
276 | if (locker == 2) | |
277 | { | |
278 | FREE_LOCK_INFO (*clasher); | |
279 | return 0; /* We ourselves locked it. */ | |
280 | } | |
281 | else if (locker == 1) | |
282 | return 1; /* Someone else has it. */ | |
283 | else if (locker == -1) | |
284 | return -1; /* Something's wrong. */ | |
285 | ||
286 | /* If some other error, or no such lock, try to lock again. */ | |
287 | /* Is there a case where we loop forever? */ | |
288 | } | |
289 | return 0; | |
8489eb67 RS |
290 | } |
291 | ||
8dbbc384 | 292 | /* lock_file locks file FN, |
8489eb67 RS |
293 | meaning it serves notice on the world that you intend to edit that file. |
294 | This should be done only when about to modify a file-visiting | |
295 | buffer previously unmodified. | |
8dbbc384 | 296 | Do not (normally) call this for a buffer already modified, |
8489eb67 RS |
297 | as either the file is already locked, or the user has already |
298 | decided to go ahead without locking. | |
299 | ||
8dbbc384 | 300 | When this returns, either the lock is locked for us, |
8489eb67 RS |
301 | or the user has said to go ahead without locking. |
302 | ||
8dbbc384 | 303 | If the file is locked by someone else, this calls |
8489eb67 | 304 | ask-user-about-lock (a Lisp function) with two arguments, |
8dbbc384 | 305 | the file name and info about the user who did the locking. |
8489eb67 RS |
306 | This function can signal an error, or return t meaning |
307 | take away the lock, or return nil meaning ignore the lock. */ | |
308 | ||
8489eb67 RS |
309 | void |
310 | lock_file (fn) | |
8dbbc384 | 311 | register Lisp_Object fn; |
8489eb67 | 312 | { |
5383bc6d | 313 | register Lisp_Object attack, orig_fn; |
8dbbc384 RS |
314 | register char *lfname, *locker; |
315 | lock_info_type lock_info; | |
8489eb67 | 316 | |
5383bc6d | 317 | orig_fn = fn; |
1e89de84 KH |
318 | fn = Fexpand_file_name (fn, Qnil); |
319 | ||
8dbbc384 | 320 | /* Create the name of the lock-file for file fn */ |
7b92975f | 321 | MAKE_LOCK_NAME (lfname, fn); |
8489eb67 | 322 | |
32676c08 JB |
323 | /* See if this file is visited and has changed on disk since it was |
324 | visited. */ | |
8489eb67 | 325 | { |
a57bc488 | 326 | register Lisp_Object subject_buf; |
5383bc6d | 327 | subject_buf = get_truename_buffer (orig_fn); |
265a9e55 JB |
328 | if (!NILP (subject_buf) |
329 | && NILP (Fverify_visited_file_modtime (subject_buf)) | |
330 | && !NILP (Ffile_exists_p (fn))) | |
8489eb67 RS |
331 | call1 (intern ("ask-user-about-supersession-threat"), fn); |
332 | } | |
333 | ||
334 | /* Try to lock the lock. */ | |
8dbbc384 RS |
335 | if (lock_if_free (&lock_info, lfname) <= 0) |
336 | /* Return now if we have locked it, or if lock creation failed */ | |
8489eb67 RS |
337 | return; |
338 | ||
339 | /* Else consider breaking the lock */ | |
8dbbc384 RS |
340 | locker = alloca (strlen (lock_info.user) + strlen (lock_info.host) |
341 | + LOCK_PID_MAX + 9); | |
342 | sprintf (locker, "%s@%s (pid %d)", lock_info.user, lock_info.host, | |
343 | lock_info.pid); | |
344 | FREE_LOCK_INFO (lock_info); | |
345 | ||
346 | attack = call2 (intern ("ask-user-about-lock"), fn, build_string (locker)); | |
265a9e55 | 347 | if (!NILP (attack)) |
8489eb67 RS |
348 | /* User says take the lock */ |
349 | { | |
8dbbc384 | 350 | lock_file_1 (lfname, 1); |
8489eb67 RS |
351 | return; |
352 | } | |
353 | /* User says ignore the lock */ | |
354 | } | |
355 | ||
8489eb67 RS |
356 | void |
357 | unlock_file (fn) | |
358 | register Lisp_Object fn; | |
359 | { | |
360 | register char *lfname; | |
361 | ||
1e89de84 KH |
362 | fn = Fexpand_file_name (fn, Qnil); |
363 | ||
7b92975f | 364 | MAKE_LOCK_NAME (lfname, fn); |
8489eb67 | 365 | |
8dbbc384 | 366 | if (current_lock_owner (0, lfname) == 2) |
8489eb67 | 367 | unlink (lfname); |
8489eb67 RS |
368 | } |
369 | ||
370 | void | |
371 | unlock_all_files () | |
372 | { | |
373 | register Lisp_Object tail; | |
374 | register struct buffer *b; | |
375 | ||
4e6c9d9e | 376 | for (tail = Vbuffer_alist; GC_CONSP (tail); tail = XCONS (tail)->cdr) |
8489eb67 RS |
377 | { |
378 | b = XBUFFER (XCONS (XCONS (tail)->car)->cdr); | |
5757b805 RS |
379 | if (STRINGP (b->file_truename) && BUF_SAVE_MODIFF (b) < BUF_MODIFF (b)) |
380 | unlock_file (b->file_truename); | |
8489eb67 RS |
381 | } |
382 | } | |
8489eb67 RS |
383 | \f |
384 | DEFUN ("lock-buffer", Flock_buffer, Slock_buffer, | |
385 | 0, 1, 0, | |
386 | "Lock FILE, if current buffer is modified.\n\ | |
387 | FILE defaults to current buffer's visited file,\n\ | |
388 | or else nothing is done if current buffer isn't visiting a file.") | |
e9319ef2 EN |
389 | (file) |
390 | Lisp_Object file; | |
8489eb67 | 391 | { |
e9319ef2 EN |
392 | if (NILP (file)) |
393 | file = current_buffer->file_truename; | |
8489eb67 | 394 | else |
e9319ef2 | 395 | CHECK_STRING (file, 0); |
6a140159 | 396 | if (SAVE_MODIFF < MODIFF |
e9319ef2 EN |
397 | && !NILP (file)) |
398 | lock_file (file); | |
8489eb67 RS |
399 | return Qnil; |
400 | } | |
401 | ||
402 | DEFUN ("unlock-buffer", Funlock_buffer, Sunlock_buffer, | |
403 | 0, 0, 0, | |
404 | "Unlock the file visited in the current buffer,\n\ | |
405 | if it should normally be locked.") | |
406 | () | |
407 | { | |
6a140159 | 408 | if (SAVE_MODIFF < MODIFF |
5757b805 RS |
409 | && STRINGP (current_buffer->file_truename)) |
410 | unlock_file (current_buffer->file_truename); | |
8489eb67 RS |
411 | return Qnil; |
412 | } | |
413 | ||
8489eb67 RS |
414 | /* Unlock the file visited in buffer BUFFER. */ |
415 | ||
416 | unlock_buffer (buffer) | |
417 | struct buffer *buffer; | |
418 | { | |
6a140159 | 419 | if (BUF_SAVE_MODIFF (buffer) < BUF_MODIFF (buffer) |
5757b805 RS |
420 | && STRINGP (buffer->file_truename)) |
421 | unlock_file (buffer->file_truename); | |
8489eb67 RS |
422 | } |
423 | ||
424 | DEFUN ("file-locked-p", Ffile_locked_p, Sfile_locked_p, 0, 1, 0, | |
425 | "Return nil if the FILENAME is not locked,\n\ | |
426 | t if it is locked by you, else a string of the name of the locker.") | |
e9319ef2 EN |
427 | (filename) |
428 | Lisp_Object filename; | |
8489eb67 | 429 | { |
8dbbc384 | 430 | Lisp_Object ret; |
8489eb67 RS |
431 | register char *lfname; |
432 | int owner; | |
8dbbc384 | 433 | lock_info_type locker; |
8489eb67 | 434 | |
e9319ef2 | 435 | filename = Fexpand_file_name (filename, Qnil); |
8489eb67 | 436 | |
e9319ef2 | 437 | MAKE_LOCK_NAME (lfname, filename); |
8489eb67 | 438 | |
8dbbc384 | 439 | owner = current_lock_owner (&locker, lfname); |
8489eb67 | 440 | if (owner <= 0) |
8dbbc384 RS |
441 | ret = Qnil; |
442 | else if (owner == 2) | |
443 | ret = Qt; | |
444 | else | |
445 | ret = build_string (locker.user); | |
446 | ||
447 | if (owner > 0) | |
448 | FREE_LOCK_INFO (locker); | |
449 | ||
450 | return ret; | |
8489eb67 RS |
451 | } |
452 | ||
32676c08 JB |
453 | \f |
454 | /* Initialization functions. */ | |
455 | ||
456 | init_filelock () | |
457 | { | |
8dbbc384 | 458 | #if 0 |
66e7fd46 | 459 | char *new_name; |
8600e6ed | 460 | |
7b92975f RS |
461 | lock_dir = egetenv ("EMACSLOCKDIR"); |
462 | if (! lock_dir) | |
463 | lock_dir = PATH_LOCK; | |
32676c08 | 464 | |
7b92975f RS |
465 | /* Copy the name in case egetenv got it from a Lisp string. */ |
466 | new_name = (char *) xmalloc (strlen (lock_dir) + 2); | |
467 | strcpy (new_name, lock_dir); | |
468 | lock_dir = new_name; | |
8600e6ed | 469 | |
32676c08 | 470 | /* Make sure it ends with a slash. */ |
7b92975f RS |
471 | if (lock_dir[strlen (lock_dir) - 1] != '/') |
472 | strcat (lock_dir, "/"); | |
32676c08 | 473 | |
7b92975f | 474 | superlock_file = (char *) xmalloc ((strlen (lock_dir) |
32676c08 | 475 | + sizeof (SUPERLOCK_NAME))); |
7b92975f RS |
476 | strcpy (superlock_file, lock_dir); |
477 | strcat (superlock_file, SUPERLOCK_NAME); | |
8dbbc384 | 478 | #endif |
32676c08 JB |
479 | } |
480 | ||
8489eb67 RS |
481 | syms_of_filelock () |
482 | { | |
483 | defsubr (&Sunlock_buffer); | |
484 | defsubr (&Slock_buffer); | |
485 | defsubr (&Sfile_locked_p); | |
486 | } | |
487 | ||
488 | #endif /* CLASH_DETECTION */ |