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d501f516 ER |
1 | ;;; userlock.el --- handle file access contention between multiple users |
2 | ||
73b0cd50 | 3 | ;; Copyright (C) 1985-1986, 2001-2011 Free Software Foundation, Inc. |
58142744 | 4 | |
6251ee24 | 5 | ;; Maintainer: FSF |
6251ee24 | 6 | ;; Keywords: internal |
e5167999 | 7 | |
a2535589 JA |
8 | ;; This file is part of GNU Emacs. |
9 | ||
eb3fa2cf | 10 | ;; GNU Emacs is free software: you can redistribute it and/or modify |
a2535589 | 11 | ;; it under the terms of the GNU General Public License as published by |
eb3fa2cf GM |
12 | ;; the Free Software Foundation, either version 3 of the License, or |
13 | ;; (at your option) any later version. | |
a2535589 JA |
14 | |
15 | ;; GNU Emacs is distributed in the hope that it will be useful, | |
16 | ;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
18 | ;; GNU General Public License for more details. | |
19 | ||
20 | ;; You should have received a copy of the GNU General Public License | |
eb3fa2cf | 21 | ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. |
a2535589 | 22 | |
e5167999 | 23 | ;;; Commentary: |
a2535589 | 24 | |
e5167999 | 25 | ;; This file is autoloaded to handle certain conditions |
a2535589 JA |
26 | ;; detected by the file-locking code within Emacs. |
27 | ;; The two entry points are `ask-user-about-lock' and | |
28 | ;; `ask-user-about-supersession-threat'. | |
29 | ||
e5167999 | 30 | ;;; Code: |
a2535589 JA |
31 | |
32 | (put 'file-locked 'error-conditions '(file-locked file-error error)) | |
bdca5405 | 33 | (put 'file-locked 'error-message "File is locked") |
a2535589 | 34 | |
f9f9507e | 35 | ;;;###autoload |
bdca5405 RS |
36 | (defun ask-user-about-lock (file opponent) |
37 | "Ask user what to do when he wants to edit FILE but it is locked by OPPONENT. | |
a2535589 | 38 | This function has a choice of three things to do: |
5f60927d | 39 | do (signal 'file-locked (list FILE OPPONENT)) |
a2535589 JA |
40 | to refrain from editing the file |
41 | return t (grab the lock on the file) | |
42 | return nil (edit the file even though it is locked). | |
bdca5405 RS |
43 | You can redefine this function to choose among those three alternatives |
44 | in any way you like." | |
a2535589 JA |
45 | (discard-input) |
46 | (save-window-excursion | |
bdca5405 RS |
47 | (let (answer short-opponent short-file) |
48 | (setq short-file | |
49 | (if (> (length file) 22) | |
50 | (concat "..." (substring file (- (length file) 22))) | |
51 | file)) | |
52 | (setq short-opponent | |
53 | (if (> (length opponent) 25) | |
54 | (save-match-data | |
55 | (string-match " (pid [0-9]+)" opponent) | |
56 | (concat (substring opponent 0 13) "..." | |
57 | (match-string 0 opponent))) | |
58 | opponent)) | |
a2535589 | 59 | (while (null answer) |
bdca5405 RS |
60 | (message "%s locked by %s: (s, q, p, ?)? " |
61 | short-file short-opponent) | |
a2535589 JA |
62 | (let ((tem (let ((inhibit-quit t) |
63 | (cursor-in-echo-area t)) | |
64 | (prog1 (downcase (read-char)) | |
65 | (setq quit-flag nil))))) | |
66 | (if (= tem help-char) | |
67 | (ask-user-about-lock-help) | |
68 | (setq answer (assoc tem '((?s . t) | |
69 | (?q . yield) | |
70 | (?\C-g . yield) | |
71 | (?p . nil) | |
72 | (?? . help)))) | |
73 | (cond ((null answer) | |
74 | (beep) | |
75 | (message "Please type q, s, or p; or ? for help") | |
76 | (sit-for 3)) | |
77 | ((eq (cdr answer) 'help) | |
78 | (ask-user-about-lock-help) | |
79 | (setq answer nil)) | |
80 | ((eq (cdr answer) 'yield) | |
bdca5405 | 81 | (signal 'file-locked (list file opponent))))))) |
a2535589 JA |
82 | (cdr answer)))) |
83 | ||
84 | (defun ask-user-about-lock-help () | |
85 | (with-output-to-temp-buffer "*Help*" | |
86 | (princ "It has been detected that you want to modify a file that someone else has | |
95d2516a | 87 | already started modifying in Emacs. |
a2535589 | 88 | |
95d2516a | 89 | You can <s>teal the file; the other user becomes the |
a2535589 JA |
90 | intruder if (s)he ever unmodifies the file and then changes it again. |
91 | You can <p>roceed; you edit at your own (and the other user's) risk. | |
0dc07483 | 92 | You can <q>uit; don't modify this file.") |
7fdbcd83 | 93 | (with-current-buffer standard-output |
0dc07483 | 94 | (help-mode)))) |
a2535589 JA |
95 | |
96 | (put | |
97 | 'file-supersession 'error-conditions '(file-supersession file-error error)) | |
98 | ||
f9f9507e | 99 | ;;;###autoload |
a2535589 JA |
100 | (defun ask-user-about-supersession-threat (fn) |
101 | "Ask a user who is about to modify an obsolete buffer what to do. | |
102 | This function has two choices: it can return, in which case the modification | |
103 | of the buffer will proceed, or it can (signal 'file-supersession (file)), | |
104 | in which case the proposed buffer modification will not be made. | |
105 | ||
106 | You can rewrite this to use any criterion you like to choose which one to do. | |
107 | The buffer in question is current when this function is called." | |
108 | (discard-input) | |
109 | (save-window-excursion | |
110 | (let (answer) | |
111 | (while (null answer) | |
11fc9165 | 112 | (message "%s changed on disk; really edit the buffer? (y, n, r or C-h) " |
a217e08a | 113 | (file-name-nondirectory fn)) |
a2535589 | 114 | (let ((tem (downcase (let ((cursor-in-echo-area t)) |
91568070 | 115 | (read-char-exclusive))))) |
a2535589 JA |
116 | (setq answer |
117 | (if (= tem help-char) | |
118 | 'help | |
119 | (cdr (assoc tem '((?n . yield) | |
120 | (?\C-g . yield) | |
121 | (?y . proceed) | |
11fc9165 | 122 | (?r . revert) |
a2535589 JA |
123 | (?? . help)))))) |
124 | (cond ((null answer) | |
125 | (beep) | |
11fc9165 | 126 | (message "Please type y, n or r; or ? for help") |
a2535589 JA |
127 | (sit-for 3)) |
128 | ((eq answer 'help) | |
129 | (ask-user-about-supersession-help) | |
130 | (setq answer nil)) | |
11fc9165 RS |
131 | ((eq answer 'revert) |
132 | (revert-buffer nil (not (buffer-modified-p))) | |
4837b516 | 133 | ; ask confirmation if buffer modified |
11fc9165 RS |
134 | (signal 'file-supersession |
135 | (list "File reverted" fn))) | |
a2535589 JA |
136 | ((eq answer 'yield) |
137 | (signal 'file-supersession | |
138 | (list "File changed on disk" fn)))))) | |
139 | (message | |
140 | "File on disk now will become a backup file if you save these changes.") | |
141 | (setq buffer-backed-up nil)))) | |
142 | ||
143 | (defun ask-user-about-supersession-help () | |
144 | (with-output-to-temp-buffer "*Help*" | |
145 | (princ "You want to modify a buffer whose disk file has changed | |
146 | since you last read it in or saved it with this buffer. | |
147 | ||
148 | If you say `y' to go ahead and modify this buffer, | |
149 | you risk ruining the work of whoever rewrote the file. | |
11fc9165 RS |
150 | If you say `r' to revert, the contents of the buffer are refreshed |
151 | from the file on disk. | |
a2535589 JA |
152 | If you say `n', the change you started to make will be aborted. |
153 | ||
154 | Usually, you should type `n' and then `M-x revert-buffer', | |
0dc07483 | 155 | to get the latest version of the file, then make the change again.") |
7fdbcd83 | 156 | (with-current-buffer standard-output |
0dc07483 | 157 | (help-mode)))) |
a2535589 | 158 | |
d501f516 | 159 | ;;; userlock.el ends here |