1 ;;; userlock.el --- handle file access contention between multiple users
3 ;; Copyright (C) 1985, 1986, 2001, 2002, 2003, 2004,
4 ;; 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Free Software Foundation, Inc.
9 ;; This file is part of GNU Emacs.
11 ;; GNU Emacs is free software: you can redistribute it and/or modify
12 ;; it under the terms of the GNU General Public License as published by
13 ;; the Free Software Foundation, either version 3 of the License, or
14 ;; (at your option) any later version.
16 ;; GNU Emacs is distributed in the hope that it will be useful,
17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 ;; GNU General Public License for more details.
21 ;; You should have received a copy of the GNU General Public License
22 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
26 ;; This file is autoloaded to handle certain conditions
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'.
33 (put 'file-locked
'error-conditions
'(file-locked file-error error
))
34 (put 'file-locked
'error-message
"File is locked")
37 (defun ask-user-about-lock (file opponent
)
38 "Ask user what to do when he wants to edit FILE but it is locked by OPPONENT.
39 This function has a choice of three things to do:
40 do (signal 'file-locked (list FILE OPPONENT))
41 to refrain from editing the file
42 return t (grab the lock on the file)
43 return nil (edit the file even though it is locked).
44 You can redefine this function to choose among those three alternatives
47 (save-window-excursion
48 (let (answer short-opponent short-file
)
50 (if (> (length file
) 22)
51 (concat "..." (substring file
(- (length file
) 22)))
54 (if (> (length opponent
) 25)
56 (string-match " (pid [0-9]+)" opponent
)
57 (concat (substring opponent
0 13) "..."
58 (match-string 0 opponent
)))
61 (message "%s locked by %s: (s, q, p, ?)? "
62 short-file short-opponent
)
63 (let ((tem (let ((inhibit-quit t
)
64 (cursor-in-echo-area t
))
65 (prog1 (downcase (read-char))
66 (setq quit-flag nil
)))))
68 (ask-user-about-lock-help)
69 (setq answer
(assoc tem
'((?s . t
)
76 (message "Please type q, s, or p; or ? for help")
78 ((eq (cdr answer
) 'help
)
79 (ask-user-about-lock-help)
81 ((eq (cdr answer
) 'yield
)
82 (signal 'file-locked
(list file opponent
)))))))
85 (defun ask-user-about-lock-help ()
86 (with-output-to-temp-buffer "*Help*"
87 (princ "It has been detected that you want to modify a file that someone else has
88 already started modifying in Emacs.
90 You can <s>teal the file; the other user becomes the
91 intruder if (s)he ever unmodifies the file and then changes it again.
92 You can <p>roceed; you edit at your own (and the other user's) risk.
93 You can <q>uit; don't modify this file.")
94 (with-current-buffer standard-output
98 'file-supersession
'error-conditions
'(file-supersession file-error error
))
101 (defun ask-user-about-supersession-threat (fn)
102 "Ask a user who is about to modify an obsolete buffer what to do.
103 This function has two choices: it can return, in which case the modification
104 of the buffer will proceed, or it can (signal 'file-supersession (file)),
105 in which case the proposed buffer modification will not be made.
107 You can rewrite this to use any criterion you like to choose which one to do.
108 The buffer in question is current when this function is called."
110 (save-window-excursion
113 (message "%s changed on disk; really edit the buffer? (y, n, r or C-h) "
114 (file-name-nondirectory fn
))
115 (let ((tem (downcase (let ((cursor-in-echo-area t
))
116 (read-char-exclusive)))))
118 (if (= tem help-char
)
120 (cdr (assoc tem
'((?n . yield
)
127 (message "Please type y, n or r; or ? for help")
130 (ask-user-about-supersession-help)
133 (revert-buffer nil
(not (buffer-modified-p)))
134 ; ask confirmation if buffer modified
135 (signal 'file-supersession
136 (list "File reverted" fn
)))
138 (signal 'file-supersession
139 (list "File changed on disk" fn
))))))
141 "File on disk now will become a backup file if you save these changes.")
142 (setq buffer-backed-up nil
))))
144 (defun ask-user-about-supersession-help ()
145 (with-output-to-temp-buffer "*Help*"
146 (princ "You want to modify a buffer whose disk file has changed
147 since you last read it in or saved it with this buffer.
149 If you say `y' to go ahead and modify this buffer,
150 you risk ruining the work of whoever rewrote the file.
151 If you say `r' to revert, the contents of the buffer are refreshed
152 from the file on disk.
153 If you say `n', the change you started to make will be aborted.
155 Usually, you should type `n' and then `M-x revert-buffer',
156 to get the latest version of the file, then make the change again.")
157 (with-current-buffer standard-output
160 ;; arch-tag: a61c5b60-e1c8-44fd-894a-c617f4dfc639
161 ;;; userlock.el ends here