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d501f516 ER |
1 | ;;; userlock.el --- handle file access contention between multiple users |
2 | ||
58142744 ER |
3 | ;; Copyright (C) 1985, 1986 Free Software Foundation, inc. |
4 | ||
6251ee24 | 5 | ;; Maintainer: FSF |
6251ee24 | 6 | ;; Keywords: internal |
e5167999 | 7 | |
a2535589 JA |
8 | ;; This file is part of GNU Emacs. |
9 | ||
10 | ;; GNU Emacs is free software; you can redistribute it and/or modify | |
11 | ;; it under the terms of the GNU General Public License as published by | |
e5167999 | 12 | ;; the Free Software Foundation; either version 2, or (at your option) |
a2535589 JA |
13 | ;; any later version. |
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 | |
21 | ;; along with GNU Emacs; see the file COPYING. If not, write to | |
22 | ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. | |
23 | ||
e5167999 | 24 | ;;; Commentary: |
a2535589 | 25 | |
e5167999 | 26 | ;; This file is autoloaded to handle certain conditions |
a2535589 JA |
27 | ;; detected by the file-locking code within Emacs. |
28 | ;; The two entry points are `ask-user-about-lock' and | |
29 | ;; `ask-user-about-supersession-threat'. | |
30 | ||
e5167999 | 31 | ;;; Code: |
a2535589 JA |
32 | |
33 | (put 'file-locked 'error-conditions '(file-locked file-error error)) | |
34 | ||
f9f9507e | 35 | ;;;###autoload |
a2535589 JA |
36 | (defun ask-user-about-lock (fn opponent) |
37 | "Ask user what to do when he wants to edit FILE but it is locked by USER. | |
38 | This function has a choice of three things to do: | |
39 | do (signal 'buffer-file-locked (list FILE USER)) | |
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). | |
43 | You can rewrite it to use any criterion you like to choose which one to do." | |
44 | (discard-input) | |
45 | (save-window-excursion | |
46 | (let (answer) | |
47 | (while (null answer) | |
48 | (message "%s is locking %s: action (s, q, p, ?)? " opponent fn) | |
49 | (let ((tem (let ((inhibit-quit t) | |
50 | (cursor-in-echo-area t)) | |
51 | (prog1 (downcase (read-char)) | |
52 | (setq quit-flag nil))))) | |
53 | (if (= tem help-char) | |
54 | (ask-user-about-lock-help) | |
55 | (setq answer (assoc tem '((?s . t) | |
56 | (?q . yield) | |
57 | (?\C-g . yield) | |
58 | (?p . nil) | |
59 | (?? . help)))) | |
60 | (cond ((null answer) | |
61 | (beep) | |
62 | (message "Please type q, s, or p; or ? for help") | |
63 | (sit-for 3)) | |
64 | ((eq (cdr answer) 'help) | |
65 | (ask-user-about-lock-help) | |
66 | (setq answer nil)) | |
67 | ((eq (cdr answer) 'yield) | |
68 | (signal 'file-locked (list "File is locked" fn opponent))))))) | |
69 | (cdr answer)))) | |
70 | ||
71 | (defun ask-user-about-lock-help () | |
72 | (with-output-to-temp-buffer "*Help*" | |
73 | (princ "It has been detected that you want to modify a file that someone else has | |
74 | already started modifying in EMACS. | |
75 | ||
76 | You can <s>teal the file; The other user becomes the | |
77 | intruder if (s)he ever unmodifies the file and then changes it again. | |
78 | You can <p>roceed; you edit at your own (and the other user's) risk. | |
79 | You can <q>uit; don't modify this file."))) | |
80 | ||
81 | (put | |
82 | 'file-supersession 'error-conditions '(file-supersession file-error error)) | |
83 | ||
f9f9507e | 84 | ;;;###autoload |
a2535589 JA |
85 | (defun ask-user-about-supersession-threat (fn) |
86 | "Ask a user who is about to modify an obsolete buffer what to do. | |
87 | This function has two choices: it can return, in which case the modification | |
88 | of the buffer will proceed, or it can (signal 'file-supersession (file)), | |
89 | in which case the proposed buffer modification will not be made. | |
90 | ||
91 | You can rewrite this to use any criterion you like to choose which one to do. | |
92 | The buffer in question is current when this function is called." | |
93 | (discard-input) | |
94 | (save-window-excursion | |
95 | (let (answer) | |
96 | (while (null answer) | |
97 | (message "File has changed on disk; really want to edit the buffer? (y, n or C-h) ") | |
98 | (let ((tem (downcase (let ((cursor-in-echo-area t)) | |
99 | (read-char))))) | |
100 | (setq answer | |
101 | (if (= tem help-char) | |
102 | 'help | |
103 | (cdr (assoc tem '((?n . yield) | |
104 | (?\C-g . yield) | |
105 | (?y . proceed) | |
106 | (?? . help)))))) | |
107 | (cond ((null answer) | |
108 | (beep) | |
109 | (message "Please type y or n; or ? for help") | |
110 | (sit-for 3)) | |
111 | ((eq answer 'help) | |
112 | (ask-user-about-supersession-help) | |
113 | (setq answer nil)) | |
114 | ((eq answer 'yield) | |
115 | (signal 'file-supersession | |
116 | (list "File changed on disk" fn)))))) | |
117 | (message | |
118 | "File on disk now will become a backup file if you save these changes.") | |
119 | (setq buffer-backed-up nil)))) | |
120 | ||
121 | (defun ask-user-about-supersession-help () | |
122 | (with-output-to-temp-buffer "*Help*" | |
123 | (princ "You want to modify a buffer whose disk file has changed | |
124 | since you last read it in or saved it with this buffer. | |
125 | ||
126 | If you say `y' to go ahead and modify this buffer, | |
127 | you risk ruining the work of whoever rewrote the file. | |
128 | If you say `n', the change you started to make will be aborted. | |
129 | ||
130 | Usually, you should type `n' and then `M-x revert-buffer', | |
131 | to get the latest version of the file, then make the change again."))) | |
132 | ||
d501f516 | 133 | ;;; userlock.el ends here |