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 | 209 | { |
a57bc488 KH |
210 | register Lisp_Object subject_buf; |
211 | subject_buf = Fget_file_buffer (fn); | |
265a9e55 JB |
212 | if (!NILP (subject_buf) |
213 | && NILP (Fverify_visited_file_modtime (subject_buf)) | |
214 | && !NILP (Ffile_exists_p (fn))) | |
8489eb67 RS |
215 | call1 (intern ("ask-user-about-supersession-threat"), fn); |
216 | } | |
217 | ||
218 | /* Try to lock the lock. */ | |
219 | if (lock_if_free (lfname) <= 0) | |
220 | /* Return now if we have locked it, or if lock dir does not exist */ | |
221 | return; | |
222 | ||
223 | /* Else consider breaking the lock */ | |
224 | attack = call2 (intern ("ask-user-about-lock"), fn, | |
225 | lock_file_owner_name (lfname)); | |
265a9e55 | 226 | if (!NILP (attack)) |
8489eb67 RS |
227 | /* User says take the lock */ |
228 | { | |
229 | lock_superlock (lfname); | |
230 | lock_file_1 (lfname, O_WRONLY) ; | |
32676c08 | 231 | unlink (superlock_path); |
8489eb67 RS |
232 | return; |
233 | } | |
234 | /* User says ignore the lock */ | |
235 | } | |
236 | ||
8489eb67 RS |
237 | /* Lock the lock file named LFNAME. |
238 | If MODE is O_WRONLY, we do so even if it is already locked. | |
239 | If MODE is O_WRONLY | O_EXCL | O_CREAT, we do so only if it is free. | |
240 | Return 1 if successful, 0 if not. */ | |
241 | ||
242 | int | |
243 | lock_file_1 (lfname, mode) | |
244 | int mode; char *lfname; | |
245 | { | |
246 | register int fd; | |
247 | char buf[20]; | |
248 | ||
249 | if ((fd = open (lfname, mode, 0666)) >= 0) | |
250 | { | |
251 | #ifdef USG | |
252 | chmod (lfname, 0666); | |
253 | #else | |
254 | fchmod (fd, 0666); | |
255 | #endif | |
256 | sprintf (buf, "%d ", getpid ()); | |
257 | write (fd, buf, strlen (buf)); | |
258 | close (fd); | |
259 | return 1; | |
260 | } | |
261 | else | |
262 | return 0; | |
263 | } | |
264 | ||
265 | /* Lock the lock named LFNAME if possible. | |
266 | Return 0 in that case. | |
267 | Return positive if lock is really locked by someone else. | |
268 | Return -1 if cannot lock for any other reason. */ | |
269 | ||
270 | int | |
271 | lock_if_free (lfname) | |
272 | register char *lfname; | |
273 | { | |
274 | register int clasher; | |
275 | ||
276 | while (lock_file_1 (lfname, O_WRONLY | O_EXCL | O_CREAT) == 0) | |
277 | { | |
278 | if (errno != EEXIST) | |
279 | return -1; | |
280 | clasher = current_lock_owner (lfname); | |
281 | if (clasher != 0) | |
282 | if (clasher != getpid ()) | |
283 | return (clasher); | |
284 | else return (0); | |
285 | /* Try again to lock it */ | |
286 | } | |
287 | return 0; | |
288 | } | |
289 | ||
290 | /* Return the pid of the process that claims to own the lock file LFNAME, | |
291 | or 0 if nobody does or the lock is obsolete, | |
292 | or -1 if something is wrong with the locking mechanism. */ | |
293 | ||
294 | int | |
295 | current_lock_owner (lfname) | |
296 | char *lfname; | |
297 | { | |
298 | int owner = current_lock_owner_1 (lfname); | |
299 | if (owner == 0 && errno == ENOENT) | |
300 | return (0); | |
301 | /* Is it locked by a process that exists? */ | |
302 | if (owner != 0 && (kill (owner, 0) >= 0 || errno == EPERM)) | |
303 | return (owner); | |
304 | if (unlink (lfname) < 0) | |
305 | return (-1); | |
306 | return (0); | |
307 | } | |
308 | ||
309 | int | |
310 | current_lock_owner_1 (lfname) | |
311 | char *lfname; | |
312 | { | |
313 | register int fd; | |
314 | char buf[20]; | |
315 | int tem; | |
316 | ||
317 | fd = open (lfname, O_RDONLY, 0666); | |
318 | if (fd < 0) | |
319 | return 0; | |
320 | tem = read (fd, buf, sizeof buf); | |
321 | close (fd); | |
322 | return (tem <= 0 ? 0 : atoi (buf)); | |
323 | } | |
324 | ||
325 | \f | |
326 | void | |
327 | unlock_file (fn) | |
328 | register Lisp_Object fn; | |
329 | { | |
330 | register char *lfname; | |
331 | ||
32676c08 | 332 | MAKE_LOCK_PATH (lfname, fn); |
8489eb67 RS |
333 | |
334 | lock_superlock (lfname); | |
335 | ||
336 | if (current_lock_owner_1 (lfname) == getpid ()) | |
337 | unlink (lfname); | |
338 | ||
32676c08 | 339 | unlink (superlock_path); |
8489eb67 RS |
340 | } |
341 | ||
342 | lock_superlock (lfname) | |
343 | char *lfname; | |
344 | { | |
345 | register int i, fd; | |
25bef3dd | 346 | DIR *lockdir; |
8489eb67 | 347 | |
32676c08 | 348 | for (i = -20; i < 0 && (fd = open (superlock_path, |
8489eb67 RS |
349 | O_WRONLY | O_EXCL | O_CREAT, 0666)) < 0; |
350 | i++) | |
351 | { | |
352 | if (errno != EEXIST) | |
353 | return; | |
25bef3dd KH |
354 | |
355 | /* This seems to be necessary to prevent Emacs from hanging when the | |
356 | competing process has already deleted the superlock, but it's still | |
357 | in the NFS cache. So we force NFS to synchronize the cache. */ | |
358 | if (lockdir = opendir (lock_path)) | |
359 | closedir (lockdir); | |
360 | ||
8489eb67 RS |
361 | sleep (1); |
362 | } | |
363 | if (fd >= 0) | |
364 | { | |
365 | #ifdef USG | |
32676c08 | 366 | chmod (superlock_path, 0666); |
8489eb67 RS |
367 | #else |
368 | fchmod (fd, 0666); | |
369 | #endif | |
370 | write (fd, lfname, strlen (lfname)); | |
371 | close (fd); | |
372 | } | |
373 | } | |
374 | ||
375 | void | |
376 | unlock_all_files () | |
377 | { | |
378 | register Lisp_Object tail; | |
379 | register struct buffer *b; | |
380 | ||
381 | for (tail = Vbuffer_alist; XGCTYPE (tail) == Lisp_Cons; | |
382 | tail = XCONS (tail)->cdr) | |
383 | { | |
384 | b = XBUFFER (XCONS (XCONS (tail)->car)->cdr); | |
385 | if (XTYPE (b->filename) == Lisp_String && | |
386 | b->save_modified < BUF_MODIFF (b)) | |
387 | unlock_file (b->filename); | |
388 | } | |
389 | } | |
390 | ||
391 | \f | |
392 | DEFUN ("lock-buffer", Flock_buffer, Slock_buffer, | |
393 | 0, 1, 0, | |
394 | "Lock FILE, if current buffer is modified.\n\ | |
395 | FILE defaults to current buffer's visited file,\n\ | |
396 | or else nothing is done if current buffer isn't visiting a file.") | |
397 | (fn) | |
398 | Lisp_Object fn; | |
399 | { | |
265a9e55 | 400 | if (NILP (fn)) |
8489eb67 RS |
401 | fn = current_buffer->filename; |
402 | else | |
403 | CHECK_STRING (fn, 0); | |
404 | if (current_buffer->save_modified < MODIFF | |
265a9e55 | 405 | && !NILP (fn)) |
8489eb67 RS |
406 | lock_file (fn); |
407 | return Qnil; | |
408 | } | |
409 | ||
410 | DEFUN ("unlock-buffer", Funlock_buffer, Sunlock_buffer, | |
411 | 0, 0, 0, | |
412 | "Unlock the file visited in the current buffer,\n\ | |
413 | if it should normally be locked.") | |
414 | () | |
415 | { | |
416 | if (current_buffer->save_modified < MODIFF && | |
417 | XTYPE (current_buffer->filename) == Lisp_String) | |
418 | unlock_file (current_buffer->filename); | |
419 | return Qnil; | |
420 | } | |
421 | ||
422 | \f | |
423 | /* Unlock the file visited in buffer BUFFER. */ | |
424 | ||
425 | unlock_buffer (buffer) | |
426 | struct buffer *buffer; | |
427 | { | |
428 | if (buffer->save_modified < BUF_MODIFF (buffer) && | |
429 | XTYPE (buffer->filename) == Lisp_String) | |
430 | unlock_file (buffer->filename); | |
431 | } | |
432 | ||
433 | DEFUN ("file-locked-p", Ffile_locked_p, Sfile_locked_p, 0, 1, 0, | |
434 | "Return nil if the FILENAME is not locked,\n\ | |
435 | t if it is locked by you, else a string of the name of the locker.") | |
436 | (fn) | |
437 | Lisp_Object fn; | |
438 | { | |
439 | register char *lfname; | |
440 | int owner; | |
441 | ||
442 | fn = Fexpand_file_name (fn, Qnil); | |
443 | ||
32676c08 | 444 | MAKE_LOCK_PATH (lfname, fn); |
8489eb67 RS |
445 | |
446 | owner = current_lock_owner (lfname); | |
447 | if (owner <= 0) | |
448 | return (Qnil); | |
449 | else if (owner == getpid ()) | |
450 | return (Qt); | |
451 | ||
452 | return (lock_file_owner_name (lfname)); | |
453 | } | |
454 | ||
32676c08 JB |
455 | \f |
456 | /* Initialization functions. */ | |
457 | ||
458 | init_filelock () | |
459 | { | |
460 | lock_path = egetenv ("EMACSLOCKDIR"); | |
461 | if (! lock_path) | |
462 | lock_path = PATH_LOCK; | |
463 | ||
464 | /* Make sure it ends with a slash. */ | |
465 | if (lock_path[strlen (lock_path) - 1] != '/') | |
466 | { | |
46013500 RS |
467 | char *new_path = (char *) xmalloc (strlen (lock_path) + 2); |
468 | strcpy (new_path, lock_path); | |
469 | lock_path = new_path; | |
32676c08 JB |
470 | strcat (lock_path, "/"); |
471 | } | |
472 | ||
473 | superlock_path = (char *) xmalloc ((strlen (lock_path) | |
474 | + sizeof (SUPERLOCK_NAME))); | |
475 | strcpy (superlock_path, lock_path); | |
476 | strcat (superlock_path, SUPERLOCK_NAME); | |
477 | } | |
478 | ||
8489eb67 RS |
479 | syms_of_filelock () |
480 | { | |
481 | defsubr (&Sunlock_buffer); | |
482 | defsubr (&Slock_buffer); | |
483 | defsubr (&Sfile_locked_p); | |
484 | } | |
485 | ||
486 | #endif /* CLASH_DETECTION */ |