Commit | Line | Data |
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c6c5df7f | 1 | /* Copyright (C) 1985, 1986, 1987, 1993 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> | |
18160b98 | 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 | 36 | #include "lisp.h" |
2a6b3537 | 37 | #include <paths.h> |
8489eb67 RS |
38 | #include "buffer.h" |
39 | ||
25bef3dd KH |
40 | #ifdef SYSV_SYSTEM_DIR |
41 | #include <dirent.h> | |
42 | #else /* not SYSV_SYSTEM_DIR */ | |
43 | #ifdef NONSYSTEM_DIR_LIBRARY | |
44 | #include "ndir.h" | |
45 | #else /* not NONSYSTEM_DIR_LIBRARY */ | |
46 | #ifdef MSDOS | |
47 | #include <dirent.h> | |
48 | #else | |
49 | #include <sys/dir.h> | |
50 | #endif | |
51 | #endif /* not NONSYSTEM_DIR_LIBRARY */ | |
52 | #ifndef MSDOS | |
53 | extern DIR *opendir (); | |
54 | #endif /* not MSDOS */ | |
55 | #endif /* not SYSV_SYSTEM_DIR */ | |
56 | ||
8489eb67 RS |
57 | extern int errno; |
58 | ||
32676c08 | 59 | extern char *egetenv (); |
d8cafeb5 | 60 | extern char *strcpy (); |
32676c08 | 61 | |
46013500 RS |
62 | #if defined (__bsdi__) || defined (DECLARE_GETPWUID_WITH_UID_T) |
63 | extern struct passwd *getpwuid (uid_t); | |
64 | #else | |
79941276 RS |
65 | extern struct passwd *getpwuid (); |
66 | #endif | |
67 | ||
8489eb67 RS |
68 | #ifdef CLASH_DETECTION |
69 | ||
70 | /* If system does not have symbolic links, it does not have lstat. | |
71 | In that case, use ordinary stat instead. */ | |
72 | ||
73 | #ifndef S_IFLNK | |
74 | #define lstat stat | |
75 | #endif | |
76 | ||
32676c08 JB |
77 | |
78 | /* The name of the directory in which we keep lock files, with a '/' | |
79 | appended. */ | |
80 | char *lock_path; | |
81 | ||
82 | /* The name of the file in the lock directory which is used to | |
83 | arbitrate access to the entire directory. */ | |
84 | #define SUPERLOCK_NAME "!!!SuperLock!!!" | |
85 | ||
86 | /* The path to the superlock file. This is SUPERLOCK_NAME appended to | |
87 | lock_path. */ | |
88 | char *superlock_path; | |
89 | ||
90 | /* Set LOCK to the name of the lock file for the filename FILE. | |
91 | char *LOCK; Lisp_Object FILE; */ | |
e31fbc7a | 92 | |
6c10d0cd | 93 | #ifndef HAVE_LONG_FILE_NAMES |
e31fbc7a RS |
94 | |
95 | #define MAKE_LOCK_PATH(lock, file) \ | |
96 | (lock = (char *) alloca (14 + strlen (lock_path) + 1), \ | |
97 | fill_in_lock_short_file_name (lock, (file))) | |
98 | ||
99 | ||
100 | fill_in_lock_short_file_name (lockfile, fn) | |
101 | register char *lockfile; | |
102 | register Lisp_Object fn; | |
103 | { | |
104 | register union | |
105 | { | |
106 | unsigned int word [2]; | |
107 | unsigned char byte [8]; | |
108 | } crc; | |
109 | register unsigned char *p, new; | |
110 | ||
111 | /* 7-bytes cyclic code for burst correction on byte-by-byte basis. | |
112 | the used polynomial is D^7 + D^6 + D^3 +1. pot@cnuce.cnr.it */ | |
113 | ||
114 | crc.word[0] = crc.word[1] = 0; | |
115 | ||
116 | for (p = XSTRING (fn)->data; new = *p++; ) | |
117 | { | |
953d263e | 118 | new += crc.byte[6]; |
e31fbc7a RS |
119 | crc.byte[6] = crc.byte[5] + new; |
120 | crc.byte[5] = crc.byte[4]; | |
121 | crc.byte[4] = crc.byte[3]; | |
122 | crc.byte[3] = crc.byte[2] + new; | |
123 | crc.byte[2] = crc.byte[1]; | |
124 | crc.byte[1] = crc.byte[0]; | |
125 | crc.byte[0] = new; | |
126 | } | |
127 | sprintf (lockfile, "%s%.2x%.2x%.2x%.2x%.2x%.2x%.2x", lock_path, | |
128 | crc.byte[0], crc.byte[1], crc.byte[2], crc.byte[3], | |
129 | crc.byte[4], crc.byte[5], crc.byte[6]); | |
130 | } | |
131 | ||
6c10d0cd | 132 | #else /* defined HAVE_LONG_FILE_NAMES */ |
e31fbc7a | 133 | |
e065a56e | 134 | #define MAKE_LOCK_PATH(lock, file) \ |
32676c08 JB |
135 | (lock = (char *) alloca (XSTRING (file)->size + strlen (lock_path) + 1), \ |
136 | fill_in_lock_file_name (lock, (file))) | |
137 | ||
e31fbc7a | 138 | |
32676c08 JB |
139 | fill_in_lock_file_name (lockfile, fn) |
140 | register char *lockfile; | |
141 | register Lisp_Object fn; | |
142 | { | |
143 | register char *p; | |
144 | ||
145 | strcpy (lockfile, lock_path); | |
146 | ||
147 | p = lockfile + strlen (lockfile); | |
148 | ||
149 | strcpy (p, XSTRING (fn)->data); | |
150 | ||
151 | for (; *p; p++) | |
152 | { | |
153 | if (*p == '/') | |
154 | *p = '!'; | |
155 | } | |
156 | } | |
6c10d0cd | 157 | #endif /* !defined HAVE_LONG_FILE_NAMES */ |
32676c08 | 158 | |
8489eb67 RS |
159 | static Lisp_Object |
160 | lock_file_owner_name (lfname) | |
161 | char *lfname; | |
162 | { | |
163 | struct stat s; | |
164 | struct passwd *the_pw; | |
8489eb67 RS |
165 | |
166 | if (lstat (lfname, &s) == 0) | |
167 | the_pw = getpwuid (s.st_uid); | |
168 | return (the_pw == 0 ? Qnil : build_string (the_pw->pw_name)); | |
169 | } | |
170 | ||
171 | ||
172 | /* lock_file locks file fn, | |
173 | meaning it serves notice on the world that you intend to edit that file. | |
174 | This should be done only when about to modify a file-visiting | |
175 | buffer previously unmodified. | |
176 | Do not (normally) call lock_buffer for a buffer already modified, | |
177 | as either the file is already locked, or the user has already | |
178 | decided to go ahead without locking. | |
179 | ||
180 | When lock_buffer returns, either the lock is locked for us, | |
181 | or the user has said to go ahead without locking. | |
182 | ||
183 | If the file is locked by someone else, lock_buffer calls | |
184 | ask-user-about-lock (a Lisp function) with two arguments, | |
185 | the file name and the name of the user who did the locking. | |
186 | This function can signal an error, or return t meaning | |
187 | take away the lock, or return nil meaning ignore the lock. */ | |
188 | ||
189 | /* The lock file name is the file name with "/" replaced by "!" | |
190 | and put in the Emacs lock directory. */ | |
191 | /* (ie., /ka/king/junk.tex -> /!/!ka!king!junk.tex). */ | |
192 | ||
6c10d0cd | 193 | /* If HAVE_LONG_FILE_NAMES is not defined, the lock file name is the hex |
e31fbc7a RS |
194 | representation of a 14-bytes CRC generated from the file name |
195 | and put in the Emacs lock directory (not very nice, but it works). | |
953d263e | 196 | (ie., /ka/king/junk.tex -> /!/12a82c62f1c6da). */ |
e31fbc7a | 197 | |
8489eb67 RS |
198 | void |
199 | lock_file (fn) | |
200 | register Lisp_Object fn; | |
201 | { | |
202 | register Lisp_Object attack; | |
203 | register char *lfname; | |
204 | ||
32676c08 | 205 | MAKE_LOCK_PATH (lfname, fn); |
8489eb67 | 206 | |
32676c08 JB |
207 | /* See if this file is visited and has changed on disk since it was |
208 | visited. */ | |
8489eb67 RS |
209 | { |
210 | register Lisp_Object subject_buf = Fget_file_buffer (fn); | |
265a9e55 JB |
211 | if (!NILP (subject_buf) |
212 | && NILP (Fverify_visited_file_modtime (subject_buf)) | |
213 | && !NILP (Ffile_exists_p (fn))) | |
8489eb67 RS |
214 | call1 (intern ("ask-user-about-supersession-threat"), fn); |
215 | } | |
216 | ||
217 | /* Try to lock the lock. */ | |
218 | if (lock_if_free (lfname) <= 0) | |
219 | /* Return now if we have locked it, or if lock dir does not exist */ | |
220 | return; | |
221 | ||
222 | /* Else consider breaking the lock */ | |
223 | attack = call2 (intern ("ask-user-about-lock"), fn, | |
224 | lock_file_owner_name (lfname)); | |
265a9e55 | 225 | if (!NILP (attack)) |
8489eb67 RS |
226 | /* User says take the lock */ |
227 | { | |
228 | lock_superlock (lfname); | |
229 | lock_file_1 (lfname, O_WRONLY) ; | |
32676c08 | 230 | unlink (superlock_path); |
8489eb67 RS |
231 | return; |
232 | } | |
233 | /* User says ignore the lock */ | |
234 | } | |
235 | ||
8489eb67 RS |
236 | /* Lock the lock file named LFNAME. |
237 | If MODE is O_WRONLY, we do so even if it is already locked. | |
238 | If MODE is O_WRONLY | O_EXCL | O_CREAT, we do so only if it is free. | |
239 | Return 1 if successful, 0 if not. */ | |
240 | ||
241 | int | |
242 | lock_file_1 (lfname, mode) | |
243 | int mode; char *lfname; | |
244 | { | |
245 | register int fd; | |
246 | char buf[20]; | |
247 | ||
248 | if ((fd = open (lfname, mode, 0666)) >= 0) | |
249 | { | |
250 | #ifdef USG | |
251 | chmod (lfname, 0666); | |
252 | #else | |
253 | fchmod (fd, 0666); | |
254 | #endif | |
255 | sprintf (buf, "%d ", getpid ()); | |
256 | write (fd, buf, strlen (buf)); | |
257 | close (fd); | |
258 | return 1; | |
259 | } | |
260 | else | |
261 | return 0; | |
262 | } | |
263 | ||
264 | /* Lock the lock named LFNAME if possible. | |
265 | Return 0 in that case. | |
266 | Return positive if lock is really locked by someone else. | |
267 | Return -1 if cannot lock for any other reason. */ | |
268 | ||
269 | int | |
270 | lock_if_free (lfname) | |
271 | register char *lfname; | |
272 | { | |
273 | register int clasher; | |
274 | ||
275 | while (lock_file_1 (lfname, O_WRONLY | O_EXCL | O_CREAT) == 0) | |
276 | { | |
277 | if (errno != EEXIST) | |
278 | return -1; | |
279 | clasher = current_lock_owner (lfname); | |
280 | if (clasher != 0) | |
281 | if (clasher != getpid ()) | |
282 | return (clasher); | |
283 | else return (0); | |
284 | /* Try again to lock it */ | |
285 | } | |
286 | return 0; | |
287 | } | |
288 | ||
289 | /* Return the pid of the process that claims to own the lock file LFNAME, | |
290 | or 0 if nobody does or the lock is obsolete, | |
291 | or -1 if something is wrong with the locking mechanism. */ | |
292 | ||
293 | int | |
294 | current_lock_owner (lfname) | |
295 | char *lfname; | |
296 | { | |
297 | int owner = current_lock_owner_1 (lfname); | |
298 | if (owner == 0 && errno == ENOENT) | |
299 | return (0); | |
300 | /* Is it locked by a process that exists? */ | |
301 | if (owner != 0 && (kill (owner, 0) >= 0 || errno == EPERM)) | |
302 | return (owner); | |
303 | if (unlink (lfname) < 0) | |
304 | return (-1); | |
305 | return (0); | |
306 | } | |
307 | ||
308 | int | |
309 | current_lock_owner_1 (lfname) | |
310 | char *lfname; | |
311 | { | |
312 | register int fd; | |
313 | char buf[20]; | |
314 | int tem; | |
315 | ||
316 | fd = open (lfname, O_RDONLY, 0666); | |
317 | if (fd < 0) | |
318 | return 0; | |
319 | tem = read (fd, buf, sizeof buf); | |
320 | close (fd); | |
321 | return (tem <= 0 ? 0 : atoi (buf)); | |
322 | } | |
323 | ||
324 | \f | |
325 | void | |
326 | unlock_file (fn) | |
327 | register Lisp_Object fn; | |
328 | { | |
329 | register char *lfname; | |
330 | ||
32676c08 | 331 | MAKE_LOCK_PATH (lfname, fn); |
8489eb67 RS |
332 | |
333 | lock_superlock (lfname); | |
334 | ||
335 | if (current_lock_owner_1 (lfname) == getpid ()) | |
336 | unlink (lfname); | |
337 | ||
32676c08 | 338 | unlink (superlock_path); |
8489eb67 RS |
339 | } |
340 | ||
341 | lock_superlock (lfname) | |
342 | char *lfname; | |
343 | { | |
344 | register int i, fd; | |
25bef3dd | 345 | DIR *lockdir; |
8489eb67 | 346 | |
32676c08 | 347 | for (i = -20; i < 0 && (fd = open (superlock_path, |
8489eb67 RS |
348 | O_WRONLY | O_EXCL | O_CREAT, 0666)) < 0; |
349 | i++) | |
350 | { | |
351 | if (errno != EEXIST) | |
352 | return; | |
25bef3dd KH |
353 | |
354 | /* This seems to be necessary to prevent Emacs from hanging when the | |
355 | competing process has already deleted the superlock, but it's still | |
356 | in the NFS cache. So we force NFS to synchronize the cache. */ | |
357 | if (lockdir = opendir (lock_path)) | |
358 | closedir (lockdir); | |
359 | ||
8489eb67 RS |
360 | sleep (1); |
361 | } | |
362 | if (fd >= 0) | |
363 | { | |
364 | #ifdef USG | |
32676c08 | 365 | chmod (superlock_path, 0666); |
8489eb67 RS |
366 | #else |
367 | fchmod (fd, 0666); | |
368 | #endif | |
369 | write (fd, lfname, strlen (lfname)); | |
370 | close (fd); | |
371 | } | |
372 | } | |
373 | ||
374 | void | |
375 | unlock_all_files () | |
376 | { | |
377 | register Lisp_Object tail; | |
378 | register struct buffer *b; | |
379 | ||
380 | for (tail = Vbuffer_alist; XGCTYPE (tail) == Lisp_Cons; | |
381 | tail = XCONS (tail)->cdr) | |
382 | { | |
383 | b = XBUFFER (XCONS (XCONS (tail)->car)->cdr); | |
384 | if (XTYPE (b->filename) == Lisp_String && | |
385 | b->save_modified < BUF_MODIFF (b)) | |
386 | unlock_file (b->filename); | |
387 | } | |
388 | } | |
389 | ||
390 | \f | |
391 | DEFUN ("lock-buffer", Flock_buffer, Slock_buffer, | |
392 | 0, 1, 0, | |
393 | "Lock FILE, if current buffer is modified.\n\ | |
394 | FILE defaults to current buffer's visited file,\n\ | |
395 | or else nothing is done if current buffer isn't visiting a file.") | |
396 | (fn) | |
397 | Lisp_Object fn; | |
398 | { | |
265a9e55 | 399 | if (NILP (fn)) |
8489eb67 RS |
400 | fn = current_buffer->filename; |
401 | else | |
402 | CHECK_STRING (fn, 0); | |
403 | if (current_buffer->save_modified < MODIFF | |
265a9e55 | 404 | && !NILP (fn)) |
8489eb67 RS |
405 | lock_file (fn); |
406 | return Qnil; | |
407 | } | |
408 | ||
409 | DEFUN ("unlock-buffer", Funlock_buffer, Sunlock_buffer, | |
410 | 0, 0, 0, | |
411 | "Unlock the file visited in the current buffer,\n\ | |
412 | if it should normally be locked.") | |
413 | () | |
414 | { | |
415 | if (current_buffer->save_modified < MODIFF && | |
416 | XTYPE (current_buffer->filename) == Lisp_String) | |
417 | unlock_file (current_buffer->filename); | |
418 | return Qnil; | |
419 | } | |
420 | ||
421 | \f | |
422 | /* Unlock the file visited in buffer BUFFER. */ | |
423 | ||
424 | unlock_buffer (buffer) | |
425 | struct buffer *buffer; | |
426 | { | |
427 | if (buffer->save_modified < BUF_MODIFF (buffer) && | |
428 | XTYPE (buffer->filename) == Lisp_String) | |
429 | unlock_file (buffer->filename); | |
430 | } | |
431 | ||
432 | DEFUN ("file-locked-p", Ffile_locked_p, Sfile_locked_p, 0, 1, 0, | |
433 | "Return nil if the FILENAME is not locked,\n\ | |
434 | t if it is locked by you, else a string of the name of the locker.") | |
435 | (fn) | |
436 | Lisp_Object fn; | |
437 | { | |
438 | register char *lfname; | |
439 | int owner; | |
440 | ||
441 | fn = Fexpand_file_name (fn, Qnil); | |
442 | ||
32676c08 | 443 | MAKE_LOCK_PATH (lfname, fn); |
8489eb67 RS |
444 | |
445 | owner = current_lock_owner (lfname); | |
446 | if (owner <= 0) | |
447 | return (Qnil); | |
448 | else if (owner == getpid ()) | |
449 | return (Qt); | |
450 | ||
451 | return (lock_file_owner_name (lfname)); | |
452 | } | |
453 | ||
32676c08 JB |
454 | \f |
455 | /* Initialization functions. */ | |
456 | ||
457 | init_filelock () | |
458 | { | |
459 | lock_path = egetenv ("EMACSLOCKDIR"); | |
460 | if (! lock_path) | |
461 | lock_path = PATH_LOCK; | |
462 | ||
463 | /* Make sure it ends with a slash. */ | |
464 | if (lock_path[strlen (lock_path) - 1] != '/') | |
465 | { | |
46013500 RS |
466 | char *new_path = (char *) xmalloc (strlen (lock_path) + 2); |
467 | strcpy (new_path, lock_path); | |
468 | lock_path = new_path; | |
32676c08 JB |
469 | strcat (lock_path, "/"); |
470 | } | |
471 | ||
472 | superlock_path = (char *) xmalloc ((strlen (lock_path) | |
473 | + sizeof (SUPERLOCK_NAME))); | |
474 | strcpy (superlock_path, lock_path); | |
475 | strcat (superlock_path, SUPERLOCK_NAME); | |
476 | } | |
477 | ||
8489eb67 RS |
478 | syms_of_filelock () |
479 | { | |
480 | defsubr (&Sunlock_buffer); | |
481 | defsubr (&Slock_buffer); | |
482 | defsubr (&Sfile_locked_p); | |
483 | } | |
484 | ||
485 | #endif /* CLASH_DETECTION */ |