1;;; userlock.el --- handle file access contention between multiple users 2 3;; Copyright (C) 1985, 1986, 2001, 2002, 2003, 2004, 4;; 2005, 2006, 2007 Free Software Foundation, Inc. 5 6;; Maintainer: FSF 7;; Keywords: internal 8 9;; This file is part of GNU Emacs. 10 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 2, or (at your option) 14;; any later version. 15 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. 20 21;; You should have received a copy of the GNU General Public License 22;; along with GNU Emacs; see the file COPYING. If not, write to the 23;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, 24;; Boston, MA 02110-1301, USA. 25 26;;; Commentary: 27 28;; This file is autoloaded to handle certain conditions 29;; detected by the file-locking code within Emacs. 30;; The two entry points are `ask-user-about-lock' and 31;; `ask-user-about-supersession-threat'. 32 33;;; Code: 34 35(put 'file-locked 'error-conditions '(file-locked file-error error)) 36(put 'file-locked 'error-message "File is locked") 37 38;;;###autoload 39(defun ask-user-about-lock (file opponent) 40 "Ask user what to do when he wants to edit FILE but it is locked by OPPONENT. 41This function has a choice of three things to do: 42 do (signal 'file-locked (list FILE OPPONENT)) 43 to refrain from editing the file 44 return t (grab the lock on the file) 45 return nil (edit the file even though it is locked). 46You can redefine this function to choose among those three alternatives 47in any way you like." 48 (discard-input) 49 (save-window-excursion 50 (let (answer short-opponent short-file) 51 (setq short-file 52 (if (> (length file) 22) 53 (concat "..." (substring file (- (length file) 22))) 54 file)) 55 (setq short-opponent 56 (if (> (length opponent) 25) 57 (save-match-data 58 (string-match " (pid [0-9]+)" opponent) 59 (concat (substring opponent 0 13) "..." 60 (match-string 0 opponent))) 61 opponent)) 62 (while (null answer) 63 (message "%s locked by %s: (s, q, p, ?)? " 64 short-file short-opponent) 65 (let ((tem (let ((inhibit-quit t) 66 (cursor-in-echo-area t)) 67 (prog1 (downcase (read-char)) 68 (setq quit-flag nil))))) 69 (if (= tem help-char) 70 (ask-user-about-lock-help) 71 (setq answer (assoc tem '((?s . t) 72 (?q . yield) 73 (?\C-g . yield) 74 (?p . nil) 75 (?? . help)))) 76 (cond ((null answer) 77 (beep) 78 (message "Please type q, s, or p; or ? for help") 79 (sit-for 3)) 80 ((eq (cdr answer) 'help) 81 (ask-user-about-lock-help) 82 (setq answer nil)) 83 ((eq (cdr answer) 'yield) 84 (signal 'file-locked (list file opponent))))))) 85 (cdr answer)))) 86 87(defun ask-user-about-lock-help () 88 (with-output-to-temp-buffer "*Help*" 89 (princ "It has been detected that you want to modify a file that someone else has 90already started modifying in Emacs. 91 92You can <s>teal the file; the other user becomes the 93 intruder if (s)he ever unmodifies the file and then changes it again. 94You can <p>roceed; you edit at your own (and the other user's) risk. 95You can <q>uit; don't modify this file.") 96 (save-excursion 97 (set-buffer standard-output) 98 (help-mode)))) 99 100(put 101 'file-supersession 'error-conditions '(file-supersession file-error error)) 102 103;;;###autoload 104(defun ask-user-about-supersession-threat (fn) 105 "Ask a user who is about to modify an obsolete buffer what to do. 106This function has two choices: it can return, in which case the modification 107of the buffer will proceed, or it can (signal 'file-supersession (file)), 108in which case the proposed buffer modification will not be made. 109 110You can rewrite this to use any criterion you like to choose which one to do. 111The buffer in question is current when this function is called." 112 (discard-input) 113 (save-window-excursion 114 (let (answer) 115 (while (null answer) 116 (message "%s changed on disk; really edit the buffer? (y, n, r or C-h) " 117 (file-name-nondirectory fn)) 118 (let ((tem (downcase (let ((cursor-in-echo-area t)) 119 (read-char-exclusive))))) 120 (setq answer 121 (if (= tem help-char) 122 'help 123 (cdr (assoc tem '((?n . yield) 124 (?\C-g . yield) 125 (?y . proceed) 126 (?r . revert) 127 (?? . help)))))) 128 (cond ((null answer) 129 (beep) 130 (message "Please type y, n or r; or ? for help") 131 (sit-for 3)) 132 ((eq answer 'help) 133 (ask-user-about-supersession-help) 134 (setq answer nil)) 135 ((eq answer 'revert) 136 (revert-buffer nil (not (buffer-modified-p))) 137 ; ask confirmation iff buffer modified 138 (signal 'file-supersession 139 (list "File reverted" fn))) 140 ((eq answer 'yield) 141 (signal 'file-supersession 142 (list "File changed on disk" fn)))))) 143 (message 144 "File on disk now will become a backup file if you save these changes.") 145 (setq buffer-backed-up nil)))) 146 147(defun ask-user-about-supersession-help () 148 (with-output-to-temp-buffer "*Help*" 149 (princ "You want to modify a buffer whose disk file has changed 150since you last read it in or saved it with this buffer. 151 152If you say `y' to go ahead and modify this buffer, 153you risk ruining the work of whoever rewrote the file. 154If you say `r' to revert, the contents of the buffer are refreshed 155from the file on disk. 156If you say `n', the change you started to make will be aborted. 157 158Usually, you should type `n' and then `M-x revert-buffer', 159to get the latest version of the file, then make the change again.") 160 (save-excursion 161 (set-buffer standard-output) 162 (help-mode)))) 163 164;;; arch-tag: a61c5b60-e1c8-44fd-894a-c617f4dfc639 165;;; userlock.el ends here 166