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> | |
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 | 42 | extern char *egetenv (); |
d8cafeb5 | 43 | extern char *strcpy (); |
32676c08 | 44 | |
44b8251a | 45 | #ifndef __386bsd__ |
79941276 RS |
46 | extern struct passwd *getpwuid (); |
47 | #endif | |
48 | ||
8489eb67 RS |
49 | #ifdef CLASH_DETECTION |
50 | ||
51 | /* If system does not have symbolic links, it does not have lstat. | |
52 | In that case, use ordinary stat instead. */ | |
53 | ||
54 | #ifndef S_IFLNK | |
55 | #define lstat stat | |
56 | #endif | |
57 | ||
32676c08 JB |
58 | |
59 | /* The name of the directory in which we keep lock files, with a '/' | |
60 | appended. */ | |
61 | char *lock_path; | |
62 | ||
63 | /* The name of the file in the lock directory which is used to | |
64 | arbitrate access to the entire directory. */ | |
65 | #define SUPERLOCK_NAME "!!!SuperLock!!!" | |
66 | ||
67 | /* The path to the superlock file. This is SUPERLOCK_NAME appended to | |
68 | lock_path. */ | |
69 | char *superlock_path; | |
70 | ||
71 | /* Set LOCK to the name of the lock file for the filename FILE. | |
72 | char *LOCK; Lisp_Object FILE; */ | |
e31fbc7a | 73 | |
6c10d0cd | 74 | #ifndef HAVE_LONG_FILE_NAMES |
e31fbc7a RS |
75 | |
76 | #define MAKE_LOCK_PATH(lock, file) \ | |
77 | (lock = (char *) alloca (14 + strlen (lock_path) + 1), \ | |
78 | fill_in_lock_short_file_name (lock, (file))) | |
79 | ||
80 | ||
81 | fill_in_lock_short_file_name (lockfile, fn) | |
82 | register char *lockfile; | |
83 | register Lisp_Object fn; | |
84 | { | |
85 | register union | |
86 | { | |
87 | unsigned int word [2]; | |
88 | unsigned char byte [8]; | |
89 | } crc; | |
90 | register unsigned char *p, new; | |
91 | ||
92 | /* 7-bytes cyclic code for burst correction on byte-by-byte basis. | |
93 | the used polynomial is D^7 + D^6 + D^3 +1. pot@cnuce.cnr.it */ | |
94 | ||
95 | crc.word[0] = crc.word[1] = 0; | |
96 | ||
97 | for (p = XSTRING (fn)->data; new = *p++; ) | |
98 | { | |
99 | new += crc.byte[7]; | |
100 | crc.byte[7] = crc.byte[6]; | |
101 | crc.byte[6] = crc.byte[5] + new; | |
102 | crc.byte[5] = crc.byte[4]; | |
103 | crc.byte[4] = crc.byte[3]; | |
104 | crc.byte[3] = crc.byte[2] + new; | |
105 | crc.byte[2] = crc.byte[1]; | |
106 | crc.byte[1] = crc.byte[0]; | |
107 | crc.byte[0] = new; | |
108 | } | |
109 | sprintf (lockfile, "%s%.2x%.2x%.2x%.2x%.2x%.2x%.2x", lock_path, | |
110 | crc.byte[0], crc.byte[1], crc.byte[2], crc.byte[3], | |
111 | crc.byte[4], crc.byte[5], crc.byte[6]); | |
112 | } | |
113 | ||
6c10d0cd | 114 | #else /* defined HAVE_LONG_FILE_NAMES */ |
e31fbc7a | 115 | |
e065a56e | 116 | #define MAKE_LOCK_PATH(lock, file) \ |
32676c08 JB |
117 | (lock = (char *) alloca (XSTRING (file)->size + strlen (lock_path) + 1), \ |
118 | fill_in_lock_file_name (lock, (file))) | |
119 | ||
e31fbc7a | 120 | |
32676c08 JB |
121 | fill_in_lock_file_name (lockfile, fn) |
122 | register char *lockfile; | |
123 | register Lisp_Object fn; | |
124 | { | |
125 | register char *p; | |
126 | ||
127 | strcpy (lockfile, lock_path); | |
128 | ||
129 | p = lockfile + strlen (lockfile); | |
130 | ||
131 | strcpy (p, XSTRING (fn)->data); | |
132 | ||
133 | for (; *p; p++) | |
134 | { | |
135 | if (*p == '/') | |
136 | *p = '!'; | |
137 | } | |
138 | } | |
6c10d0cd | 139 | #endif /* !defined HAVE_LONG_FILE_NAMES */ |
32676c08 | 140 | |
8489eb67 RS |
141 | static Lisp_Object |
142 | lock_file_owner_name (lfname) | |
143 | char *lfname; | |
144 | { | |
145 | struct stat s; | |
146 | struct passwd *the_pw; | |
8489eb67 RS |
147 | |
148 | if (lstat (lfname, &s) == 0) | |
149 | the_pw = getpwuid (s.st_uid); | |
150 | return (the_pw == 0 ? Qnil : build_string (the_pw->pw_name)); | |
151 | } | |
152 | ||
153 | ||
154 | /* lock_file locks file fn, | |
155 | meaning it serves notice on the world that you intend to edit that file. | |
156 | This should be done only when about to modify a file-visiting | |
157 | buffer previously unmodified. | |
158 | Do not (normally) call lock_buffer for a buffer already modified, | |
159 | as either the file is already locked, or the user has already | |
160 | decided to go ahead without locking. | |
161 | ||
162 | When lock_buffer returns, either the lock is locked for us, | |
163 | or the user has said to go ahead without locking. | |
164 | ||
165 | If the file is locked by someone else, lock_buffer calls | |
166 | ask-user-about-lock (a Lisp function) with two arguments, | |
167 | the file name and the name of the user who did the locking. | |
168 | This function can signal an error, or return t meaning | |
169 | take away the lock, or return nil meaning ignore the lock. */ | |
170 | ||
171 | /* The lock file name is the file name with "/" replaced by "!" | |
172 | and put in the Emacs lock directory. */ | |
173 | /* (ie., /ka/king/junk.tex -> /!/!ka!king!junk.tex). */ | |
174 | ||
6c10d0cd | 175 | /* If HAVE_LONG_FILE_NAMES is not defined, the lock file name is the hex |
e31fbc7a RS |
176 | representation of a 14-bytes CRC generated from the file name |
177 | and put in the Emacs lock directory (not very nice, but it works). | |
178 | (ie., /ka/king/junk.tex -> /!/ec92d3ed24a8f0). */ | |
179 | ||
8489eb67 RS |
180 | void |
181 | lock_file (fn) | |
182 | register Lisp_Object fn; | |
183 | { | |
184 | register Lisp_Object attack; | |
185 | register char *lfname; | |
186 | ||
32676c08 | 187 | MAKE_LOCK_PATH (lfname, fn); |
8489eb67 | 188 | |
32676c08 JB |
189 | /* See if this file is visited and has changed on disk since it was |
190 | visited. */ | |
8489eb67 RS |
191 | { |
192 | register Lisp_Object subject_buf = Fget_file_buffer (fn); | |
265a9e55 JB |
193 | if (!NILP (subject_buf) |
194 | && NILP (Fverify_visited_file_modtime (subject_buf)) | |
195 | && !NILP (Ffile_exists_p (fn))) | |
8489eb67 RS |
196 | call1 (intern ("ask-user-about-supersession-threat"), fn); |
197 | } | |
198 | ||
199 | /* Try to lock the lock. */ | |
200 | if (lock_if_free (lfname) <= 0) | |
201 | /* Return now if we have locked it, or if lock dir does not exist */ | |
202 | return; | |
203 | ||
204 | /* Else consider breaking the lock */ | |
205 | attack = call2 (intern ("ask-user-about-lock"), fn, | |
206 | lock_file_owner_name (lfname)); | |
265a9e55 | 207 | if (!NILP (attack)) |
8489eb67 RS |
208 | /* User says take the lock */ |
209 | { | |
210 | lock_superlock (lfname); | |
211 | lock_file_1 (lfname, O_WRONLY) ; | |
32676c08 | 212 | unlink (superlock_path); |
8489eb67 RS |
213 | return; |
214 | } | |
215 | /* User says ignore the lock */ | |
216 | } | |
217 | ||
8489eb67 RS |
218 | /* Lock the lock file named LFNAME. |
219 | If MODE is O_WRONLY, we do so even if it is already locked. | |
220 | If MODE is O_WRONLY | O_EXCL | O_CREAT, we do so only if it is free. | |
221 | Return 1 if successful, 0 if not. */ | |
222 | ||
223 | int | |
224 | lock_file_1 (lfname, mode) | |
225 | int mode; char *lfname; | |
226 | { | |
227 | register int fd; | |
228 | char buf[20]; | |
229 | ||
230 | if ((fd = open (lfname, mode, 0666)) >= 0) | |
231 | { | |
232 | #ifdef USG | |
233 | chmod (lfname, 0666); | |
234 | #else | |
235 | fchmod (fd, 0666); | |
236 | #endif | |
237 | sprintf (buf, "%d ", getpid ()); | |
238 | write (fd, buf, strlen (buf)); | |
239 | close (fd); | |
240 | return 1; | |
241 | } | |
242 | else | |
243 | return 0; | |
244 | } | |
245 | ||
246 | /* Lock the lock named LFNAME if possible. | |
247 | Return 0 in that case. | |
248 | Return positive if lock is really locked by someone else. | |
249 | Return -1 if cannot lock for any other reason. */ | |
250 | ||
251 | int | |
252 | lock_if_free (lfname) | |
253 | register char *lfname; | |
254 | { | |
255 | register int clasher; | |
256 | ||
257 | while (lock_file_1 (lfname, O_WRONLY | O_EXCL | O_CREAT) == 0) | |
258 | { | |
259 | if (errno != EEXIST) | |
260 | return -1; | |
261 | clasher = current_lock_owner (lfname); | |
262 | if (clasher != 0) | |
263 | if (clasher != getpid ()) | |
264 | return (clasher); | |
265 | else return (0); | |
266 | /* Try again to lock it */ | |
267 | } | |
268 | return 0; | |
269 | } | |
270 | ||
271 | /* Return the pid of the process that claims to own the lock file LFNAME, | |
272 | or 0 if nobody does or the lock is obsolete, | |
273 | or -1 if something is wrong with the locking mechanism. */ | |
274 | ||
275 | int | |
276 | current_lock_owner (lfname) | |
277 | char *lfname; | |
278 | { | |
279 | int owner = current_lock_owner_1 (lfname); | |
280 | if (owner == 0 && errno == ENOENT) | |
281 | return (0); | |
282 | /* Is it locked by a process that exists? */ | |
283 | if (owner != 0 && (kill (owner, 0) >= 0 || errno == EPERM)) | |
284 | return (owner); | |
285 | if (unlink (lfname) < 0) | |
286 | return (-1); | |
287 | return (0); | |
288 | } | |
289 | ||
290 | int | |
291 | current_lock_owner_1 (lfname) | |
292 | char *lfname; | |
293 | { | |
294 | register int fd; | |
295 | char buf[20]; | |
296 | int tem; | |
297 | ||
298 | fd = open (lfname, O_RDONLY, 0666); | |
299 | if (fd < 0) | |
300 | return 0; | |
301 | tem = read (fd, buf, sizeof buf); | |
302 | close (fd); | |
303 | return (tem <= 0 ? 0 : atoi (buf)); | |
304 | } | |
305 | ||
306 | \f | |
307 | void | |
308 | unlock_file (fn) | |
309 | register Lisp_Object fn; | |
310 | { | |
311 | register char *lfname; | |
312 | ||
32676c08 | 313 | MAKE_LOCK_PATH (lfname, fn); |
8489eb67 RS |
314 | |
315 | lock_superlock (lfname); | |
316 | ||
317 | if (current_lock_owner_1 (lfname) == getpid ()) | |
318 | unlink (lfname); | |
319 | ||
32676c08 | 320 | unlink (superlock_path); |
8489eb67 RS |
321 | } |
322 | ||
323 | lock_superlock (lfname) | |
324 | char *lfname; | |
325 | { | |
326 | register int i, fd; | |
327 | ||
32676c08 | 328 | for (i = -20; i < 0 && (fd = open (superlock_path, |
8489eb67 RS |
329 | O_WRONLY | O_EXCL | O_CREAT, 0666)) < 0; |
330 | i++) | |
331 | { | |
332 | if (errno != EEXIST) | |
333 | return; | |
334 | sleep (1); | |
335 | } | |
336 | if (fd >= 0) | |
337 | { | |
338 | #ifdef USG | |
32676c08 | 339 | chmod (superlock_path, 0666); |
8489eb67 RS |
340 | #else |
341 | fchmod (fd, 0666); | |
342 | #endif | |
343 | write (fd, lfname, strlen (lfname)); | |
344 | close (fd); | |
345 | } | |
346 | } | |
347 | ||
348 | void | |
349 | unlock_all_files () | |
350 | { | |
351 | register Lisp_Object tail; | |
352 | register struct buffer *b; | |
353 | ||
354 | for (tail = Vbuffer_alist; XGCTYPE (tail) == Lisp_Cons; | |
355 | tail = XCONS (tail)->cdr) | |
356 | { | |
357 | b = XBUFFER (XCONS (XCONS (tail)->car)->cdr); | |
358 | if (XTYPE (b->filename) == Lisp_String && | |
359 | b->save_modified < BUF_MODIFF (b)) | |
360 | unlock_file (b->filename); | |
361 | } | |
362 | } | |
363 | ||
364 | \f | |
365 | DEFUN ("lock-buffer", Flock_buffer, Slock_buffer, | |
366 | 0, 1, 0, | |
367 | "Lock FILE, if current buffer is modified.\n\ | |
368 | FILE defaults to current buffer's visited file,\n\ | |
369 | or else nothing is done if current buffer isn't visiting a file.") | |
370 | (fn) | |
371 | Lisp_Object fn; | |
372 | { | |
265a9e55 | 373 | if (NILP (fn)) |
8489eb67 RS |
374 | fn = current_buffer->filename; |
375 | else | |
376 | CHECK_STRING (fn, 0); | |
377 | if (current_buffer->save_modified < MODIFF | |
265a9e55 | 378 | && !NILP (fn)) |
8489eb67 RS |
379 | lock_file (fn); |
380 | return Qnil; | |
381 | } | |
382 | ||
383 | DEFUN ("unlock-buffer", Funlock_buffer, Sunlock_buffer, | |
384 | 0, 0, 0, | |
385 | "Unlock the file visited in the current buffer,\n\ | |
386 | if it should normally be locked.") | |
387 | () | |
388 | { | |
389 | if (current_buffer->save_modified < MODIFF && | |
390 | XTYPE (current_buffer->filename) == Lisp_String) | |
391 | unlock_file (current_buffer->filename); | |
392 | return Qnil; | |
393 | } | |
394 | ||
395 | \f | |
396 | /* Unlock the file visited in buffer BUFFER. */ | |
397 | ||
398 | unlock_buffer (buffer) | |
399 | struct buffer *buffer; | |
400 | { | |
401 | if (buffer->save_modified < BUF_MODIFF (buffer) && | |
402 | XTYPE (buffer->filename) == Lisp_String) | |
403 | unlock_file (buffer->filename); | |
404 | } | |
405 | ||
406 | DEFUN ("file-locked-p", Ffile_locked_p, Sfile_locked_p, 0, 1, 0, | |
407 | "Return nil if the FILENAME is not locked,\n\ | |
408 | t if it is locked by you, else a string of the name of the locker.") | |
409 | (fn) | |
410 | Lisp_Object fn; | |
411 | { | |
412 | register char *lfname; | |
413 | int owner; | |
414 | ||
415 | fn = Fexpand_file_name (fn, Qnil); | |
416 | ||
32676c08 | 417 | MAKE_LOCK_PATH (lfname, fn); |
8489eb67 RS |
418 | |
419 | owner = current_lock_owner (lfname); | |
420 | if (owner <= 0) | |
421 | return (Qnil); | |
422 | else if (owner == getpid ()) | |
423 | return (Qt); | |
424 | ||
425 | return (lock_file_owner_name (lfname)); | |
426 | } | |
427 | ||
32676c08 JB |
428 | \f |
429 | /* Initialization functions. */ | |
430 | ||
431 | init_filelock () | |
432 | { | |
433 | lock_path = egetenv ("EMACSLOCKDIR"); | |
434 | if (! lock_path) | |
435 | lock_path = PATH_LOCK; | |
436 | ||
437 | /* Make sure it ends with a slash. */ | |
438 | if (lock_path[strlen (lock_path) - 1] != '/') | |
439 | { | |
440 | lock_path = strcpy ((char *) xmalloc (strlen (lock_path) + 2), | |
441 | lock_path); | |
442 | strcat (lock_path, "/"); | |
443 | } | |
444 | ||
445 | superlock_path = (char *) xmalloc ((strlen (lock_path) | |
446 | + sizeof (SUPERLOCK_NAME))); | |
447 | strcpy (superlock_path, lock_path); | |
448 | strcat (superlock_path, SUPERLOCK_NAME); | |
449 | } | |
450 | ||
8489eb67 RS |
451 | syms_of_filelock () |
452 | { | |
453 | defsubr (&Sunlock_buffer); | |
454 | defsubr (&Slock_buffer); | |
455 | defsubr (&Sfile_locked_p); | |
456 | } | |
457 | ||
458 | #endif /* CLASH_DETECTION */ |