1;;; userlock.el --- handle file access contention between multiple users 2 3;; Copyright (C) 1985, 1986 Free Software Foundation, inc. 4 5;; Maintainer: FSF 6;; Keywords: internal 7 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 12;; the Free Software Foundation; either version 2, or (at your option) 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 24;;; Commentary: 25 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'. 30 31;;; Code: 32 33(put 'file-locked 'error-conditions '(file-locked file-error error)) 34 35;;;###autoload 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. 38This 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). 43You 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 74already started modifying in EMACS. 75 76You can <s>teal the file; The other user becomes the 77 intruder if (s)he ever unmodifies the file and then changes it again. 78You can <p>roceed; you edit at your own (and the other user's) risk. 79You can <q>uit; don't modify this file."))) 80 81(put 82 'file-supersession 'error-conditions '(file-supersession file-error error)) 83 84;;;###autoload 85(defun ask-user-about-supersession-threat (fn) 86 "Ask a user who is about to modify an obsolete buffer what to do. 87This function has two choices: it can return, in which case the modification 88of the buffer will proceed, or it can (signal 'file-supersession (file)), 89in which case the proposed buffer modification will not be made. 90 91You can rewrite this to use any criterion you like to choose which one to do. 92The 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 "%s changed on disk; really edit the buffer? (y, n or C-h) " 98 (file-name-nondirectory fn)) 99 (let ((tem (downcase (let ((cursor-in-echo-area t)) 100 (read-char))))) 101 (setq answer 102 (if (= tem help-char) 103 'help 104 (cdr (assoc tem '((?n . yield) 105 (?\C-g . yield) 106 (?y . proceed) 107 (?? . help)))))) 108 (cond ((null answer) 109 (beep) 110 (message "Please type y or n; or ? for help") 111 (sit-for 3)) 112 ((eq answer 'help) 113 (ask-user-about-supersession-help) 114 (setq answer nil)) 115 ((eq answer 'yield) 116 (signal 'file-supersession 117 (list "File changed on disk" fn)))))) 118 (message 119 "File on disk now will become a backup file if you save these changes.") 120 (setq buffer-backed-up nil)))) 121 122(defun ask-user-about-supersession-help () 123 (with-output-to-temp-buffer "*Help*" 124 (princ "You want to modify a buffer whose disk file has changed 125since you last read it in or saved it with this buffer. 126 127If you say `y' to go ahead and modify this buffer, 128you risk ruining the work of whoever rewrote the file. 129If you say `n', the change you started to make will be aborted. 130 131Usually, you should type `n' and then `M-x revert-buffer', 132to get the latest version of the file, then make the change again."))) 133 134;;; userlock.el ends here 135