| 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 the |
| 22 | ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330, |
| 23 | ;; Boston, MA 02111-1307, USA. |
| 24 | |
| 25 | ;;; Commentary: |
| 26 | |
| 27 | ;; This file is autoloaded to handle certain conditions |
| 28 | ;; detected by the file-locking code within Emacs. |
| 29 | ;; The two entry points are `ask-user-about-lock' and |
| 30 | ;; `ask-user-about-supersession-threat'. |
| 31 | |
| 32 | ;;; Code: |
| 33 | |
| 34 | (put 'file-locked 'error-conditions '(file-locked file-error error)) |
| 35 | |
| 36 | ;;;###autoload |
| 37 | (defun ask-user-about-lock (fn opponent) |
| 38 | "Ask user what to do when he wants to edit FILE but it is locked by USER. |
| 39 | This function has a choice of three things to do: |
| 40 | do (signal 'buffer-file-locked (list FILE USER)) |
| 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 rewrite it to use any criterion you like to choose which one to do." |
| 45 | (discard-input) |
| 46 | (save-window-excursion |
| 47 | (let (answer) |
| 48 | (while (null answer) |
| 49 | (message "%s is locking %s: action (s, q, p, ?)? " opponent fn) |
| 50 | (let ((tem (let ((inhibit-quit t) |
| 51 | (cursor-in-echo-area t)) |
| 52 | (prog1 (downcase (read-char)) |
| 53 | (setq quit-flag nil))))) |
| 54 | (if (= tem help-char) |
| 55 | (ask-user-about-lock-help) |
| 56 | (setq answer (assoc tem '((?s . t) |
| 57 | (?q . yield) |
| 58 | (?\C-g . yield) |
| 59 | (?p . nil) |
| 60 | (?? . help)))) |
| 61 | (cond ((null answer) |
| 62 | (beep) |
| 63 | (message "Please type q, s, or p; or ? for help") |
| 64 | (sit-for 3)) |
| 65 | ((eq (cdr answer) 'help) |
| 66 | (ask-user-about-lock-help) |
| 67 | (setq answer nil)) |
| 68 | ((eq (cdr answer) 'yield) |
| 69 | (signal 'file-locked (list "File is locked" fn opponent))))))) |
| 70 | (cdr answer)))) |
| 71 | |
| 72 | (defun ask-user-about-lock-help () |
| 73 | (with-output-to-temp-buffer "*Help*" |
| 74 | (princ "It has been detected that you want to modify a file that someone else has |
| 75 | already started modifying in EMACS. |
| 76 | |
| 77 | You can <s>teal the file; The other user becomes the |
| 78 | intruder if (s)he ever unmodifies the file and then changes it again. |
| 79 | You can <p>roceed; you edit at your own (and the other user's) risk. |
| 80 | You can <q>uit; don't modify this file.") |
| 81 | (save-excursion |
| 82 | (set-buffer standard-output) |
| 83 | (help-mode)))) |
| 84 | |
| 85 | (put |
| 86 | 'file-supersession 'error-conditions '(file-supersession file-error error)) |
| 87 | |
| 88 | ;;;###autoload |
| 89 | (defun ask-user-about-supersession-threat (fn) |
| 90 | "Ask a user who is about to modify an obsolete buffer what to do. |
| 91 | This function has two choices: it can return, in which case the modification |
| 92 | of the buffer will proceed, or it can (signal 'file-supersession (file)), |
| 93 | in which case the proposed buffer modification will not be made. |
| 94 | |
| 95 | You can rewrite this to use any criterion you like to choose which one to do. |
| 96 | The buffer in question is current when this function is called." |
| 97 | (discard-input) |
| 98 | (save-window-excursion |
| 99 | (let (answer) |
| 100 | (while (null answer) |
| 101 | (message "%s changed on disk; really edit the buffer? (y, n or C-h) " |
| 102 | (file-name-nondirectory fn)) |
| 103 | (let ((tem (downcase (let ((cursor-in-echo-area t)) |
| 104 | (read-char))))) |
| 105 | (setq answer |
| 106 | (if (= tem help-char) |
| 107 | 'help |
| 108 | (cdr (assoc tem '((?n . yield) |
| 109 | (?\C-g . yield) |
| 110 | (?y . proceed) |
| 111 | (?? . help)))))) |
| 112 | (cond ((null answer) |
| 113 | (beep) |
| 114 | (message "Please type y or n; or ? for help") |
| 115 | (sit-for 3)) |
| 116 | ((eq answer 'help) |
| 117 | (ask-user-about-supersession-help) |
| 118 | (setq answer nil)) |
| 119 | ((eq answer 'yield) |
| 120 | (signal 'file-supersession |
| 121 | (list "File changed on disk" fn)))))) |
| 122 | (message |
| 123 | "File on disk now will become a backup file if you save these changes.") |
| 124 | (setq buffer-backed-up nil)))) |
| 125 | |
| 126 | (defun ask-user-about-supersession-help () |
| 127 | (with-output-to-temp-buffer "*Help*" |
| 128 | (princ "You want to modify a buffer whose disk file has changed |
| 129 | since you last read it in or saved it with this buffer. |
| 130 | |
| 131 | If you say `y' to go ahead and modify this buffer, |
| 132 | you risk ruining the work of whoever rewrote the file. |
| 133 | If you say `n', the change you started to make will be aborted. |
| 134 | |
| 135 | Usually, you should type `n' and then `M-x revert-buffer', |
| 136 | to get the latest version of the file, then make the change again.") |
| 137 | (save-excursion |
| 138 | (set-buffer standard-output) |
| 139 | (help-mode)))) |
| 140 | |
| 141 | ;;; userlock.el ends here |