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emacs/lisp/compare-w.el
1992-07-22 04:22:30 +00:00

137 lines
4.5 KiB
EmacsLisp

;;; compare-w.el --- compare text between windows for Emacs.
;; Copyright (C) 1986, 1989 Free Software Foundation, Inc.
;; Maintainer: FSF
;; This file is part of GNU Emacs.
;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING. If not, write to
;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
;;; Code:
(defvar compare-windows-whitespace " \t\n"
"*String of characters considered whitespace for \\[compare-windows].
Changes in whitespace are optionally ignored.
The value of `compare-windows-whitespace' may instead be a function; this
function is called in each buffer, with point at the current scanning point.
The function's job is to categorize any whitespace around (including before)
point; it should also advance past any whitespace.
The function is passed one argument, the point where `compare-windows'
was originally called; it should not consider any text before that point.
If the function returns the same value for both buffers, then the
whitespace is considered to match, and is skipped.")
(defvar compare-ignore-case nil
"*Non-nil means \\[compare-windows] ignores case differences.")
;;;###autoload
(defun compare-windows (ignore-whitespace)
"Compare text in current window with text in next window.
Compares the text starting at point in each window,
moving over text in each one as far as they match.
A prefix arg means ignore changes in whitespace.
The variable `compare-windows-whitespace' controls how whitespace is skipped.
If `compare-ignore-case' is non-nil, changes in case are also ignored."
(interactive "P")
(let* (p1 p2 maxp1 maxp2 b1 b2 w2
success size
(opoint1 (point))
opoint2
(skip-whitespace (if ignore-whitespace
compare-windows-whitespace))
(skip-whitespace-regexp (concat "[" skip-whitespace "]+")))
(setq p1 (point) b1 (current-buffer))
(setq w2 (next-window (selected-window)))
(if (eq w2 (selected-window))
(error "No other window"))
(setq p2 (window-point w2)
b2 (window-buffer w2))
(setq opoint2 p2)
(setq maxp1 (point-max))
(save-excursion
(set-buffer b2)
(setq maxp2 (point-max)))
(setq success t)
(while success
(setq success nil)
;; if interrupted, show how far we've gotten
(goto-char p1)
(set-window-point w2 p2)
;; If both buffers have whitespace next to point,
;; optionally skip over it.
(and skip-whitespace
(save-excursion
(let (p1a p2a w1 w2 result1 result2)
(if (stringp skip-whitespace)
(progn
(if (not (eobp))
(skip-chars-backward skip-whitespace opoint1))
(and (looking-at skip-whitespace-regexp)
(setq p1a (match-end 0) result1 t)))
(setq result1 (funcall skip-whitespace opoint1))
(setq p1a (point)))
(set-buffer b2)
(goto-char p2)
(if (stringp skip-whitespace)
(progn
(if (not (eobp))
(skip-chars-backward skip-whitespace opoint2))
(and (looking-at skip-whitespace-regexp)
(setq p2a (match-end 0) result2 t)))
(setq result2 (funcall skip-whitespace opoint2))
(setq p2a (point)))
(and result1 result2 (eq result1 result2)
(setq p1 p1a
p2 p2a)))))
;; Try advancing comparing 1000 chars at a time.
;; When that fails, go 500 chars at a time, and so on.
(let ((size 1000)
success-1)
(while (> size 0)
(setq success-1 t)
(while success-1
(setq size (min size (- maxp1 p1) (- maxp2 p2)))
(save-excursion
(set-buffer b2)
(setq s2 (buffer-substring p2 (+ size p2))))
(setq success-1
(and (> size 0)
(if compare-ignore-case
(let ((case-fold-search t))
(save-excursion
(search-forward s2 (+ p1 size) t)))
(equal (buffer-substring p1 (+ size p1)) s2))))
(if success-1
(setq p1 (+ p1 size) p2 (+ p2 size)
success t)))
(setq size (/ size 2)))))
(goto-char p1)
(set-window-point w2 p2)
(if (= (point) opoint1)
(ding))))
(provide 'compare-w)
;;; compare-w.el ends here