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134 lines
4.7 KiB
EmacsLisp
134 lines
4.7 KiB
EmacsLisp
;;; userlock.el --- handle file access contention between multiple users
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;; Copyright (C) 1985, 1986 Free Software Foundation, inc.
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;; Maintainer: FSF
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;; Keywords: internal
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software; you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation; either version 2, or (at your option)
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;; any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs; see the file COPYING. If not, write to
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;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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;;; Commentary:
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;; This file is autoloaded to handle certain conditions
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;; detected by the file-locking code within Emacs.
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;; The two entry points are `ask-user-about-lock' and
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;; `ask-user-about-supersession-threat'.
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;;; Code:
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(put 'file-locked 'error-conditions '(file-locked file-error error))
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;;;###autoload
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(defun ask-user-about-lock (fn opponent)
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"Ask user what to do when he wants to edit FILE but it is locked by USER.
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This function has a choice of three things to do:
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do (signal 'buffer-file-locked (list FILE USER))
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to refrain from editing the file
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return t (grab the lock on the file)
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return nil (edit the file even though it is locked).
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You can rewrite it to use any criterion you like to choose which one to do."
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(discard-input)
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(save-window-excursion
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(let (answer)
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(while (null answer)
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(message "%s is locking %s: action (s, q, p, ?)? " opponent fn)
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(let ((tem (let ((inhibit-quit t)
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(cursor-in-echo-area t))
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(prog1 (downcase (read-char))
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(setq quit-flag nil)))))
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(if (= tem help-char)
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(ask-user-about-lock-help)
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(setq answer (assoc tem '((?s . t)
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(?q . yield)
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(?\C-g . yield)
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(?p . nil)
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(?? . help))))
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(cond ((null answer)
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(beep)
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(message "Please type q, s, or p; or ? for help")
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(sit-for 3))
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((eq (cdr answer) 'help)
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(ask-user-about-lock-help)
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(setq answer nil))
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((eq (cdr answer) 'yield)
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(signal 'file-locked (list "File is locked" fn opponent)))))))
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(cdr answer))))
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(defun ask-user-about-lock-help ()
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(with-output-to-temp-buffer "*Help*"
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(princ "It has been detected that you want to modify a file that someone else has
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already started modifying in EMACS.
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You can <s>teal the file; The other user becomes the
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intruder if (s)he ever unmodifies the file and then changes it again.
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You can <p>roceed; you edit at your own (and the other user's) risk.
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You can <q>uit; don't modify this file.")))
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(put
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'file-supersession 'error-conditions '(file-supersession file-error error))
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;;;###autoload
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(defun ask-user-about-supersession-threat (fn)
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"Ask a user who is about to modify an obsolete buffer what to do.
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This function has two choices: it can return, in which case the modification
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of the buffer will proceed, or it can (signal 'file-supersession (file)),
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in which case the proposed buffer modification will not be made.
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You can rewrite this to use any criterion you like to choose which one to do.
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The buffer in question is current when this function is called."
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(discard-input)
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(save-window-excursion
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(let (answer)
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(while (null answer)
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(message "File has changed on disk; really want to edit the buffer? (y, n or C-h) ")
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(let ((tem (downcase (let ((cursor-in-echo-area t))
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(read-char)))))
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(setq answer
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(if (= tem help-char)
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'help
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(cdr (assoc tem '((?n . yield)
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(?\C-g . yield)
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(?y . proceed)
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(?? . help))))))
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(cond ((null answer)
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(beep)
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(message "Please type y or n; or ? for help")
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(sit-for 3))
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((eq answer 'help)
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(ask-user-about-supersession-help)
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(setq answer nil))
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((eq answer 'yield)
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(signal 'file-supersession
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(list "File changed on disk" fn))))))
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(message
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"File on disk now will become a backup file if you save these changes.")
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(setq buffer-backed-up nil))))
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(defun ask-user-about-supersession-help ()
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(with-output-to-temp-buffer "*Help*"
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(princ "You want to modify a buffer whose disk file has changed
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since you last read it in or saved it with this buffer.
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If you say `y' to go ahead and modify this buffer,
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you risk ruining the work of whoever rewrote the file.
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If you say `n', the change you started to make will be aborted.
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Usually, you should type `n' and then `M-x revert-buffer',
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to get the latest version of the file, then make the change again.")))
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;;; userlock.el ends here
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