;;; compare-w.el --- compare text between windows for Emacs.
-;; Copyright (C) 1986, 1989 Free Software Foundation, Inc.
+;; Copyright (C) 1986, 1989, 1993 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 1, or (at your option)
+;; 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,
;; along with GNU Emacs; see the file COPYING. If not, write to
;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
-(defvar compare-windows-whitespace " \t\n"
- "*String of characters considered whitespace for \\[compare-windows].
+;;; Commentary:
+
+;; This package provides one entry point, compare-windows. It compares
+;; text starting from point in two adjacent windows, advancing point
+;; until it finds a difference. Option variables permit you to ignore
+;; whitespace differences, or case differences, or both.
+
+;;; Code:
+
+(defvar compare-windows-whitespace "[ \t\n]+"
+ "*Regexp that defines whitespace sequences for \\[compare-windows].
Changes in whitespace are optionally ignored.
The value of `compare-windows-whitespace' may instead be a function; this
Compares the text starting at point in each window,
moving over text in each one as far as they match.
+This command pushes the mark in each window
+at the prior location of point in that window.
+If both windows display the same buffer,
+the mark is pushed twice in that buffer:
+first in the other window, then in the selected window.
+
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."
(opoint1 (point))
opoint2
(skip-whitespace (if ignore-whitespace
- compare-windows-whitespace))
- (skip-whitespace-regexp (concat "[" skip-whitespace "]+")))
+ compare-windows-whitespace)))
(setq p1 (point) b1 (current-buffer))
(setq w2 (next-window (selected-window)))
(if (eq w2 (selected-window))
(setq maxp1 (point-max))
(save-excursion
(set-buffer b2)
+ (push-mark p2 t)
(setq maxp2 (point-max)))
+ (push-mark)
(setq success t)
(while success
(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)))
+ (setq result1
+ (if (stringp skip-whitespace)
+ (compare-windows-skip-whitespace opoint1)
+ (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)))))
+ (setq result2
+ (if (stringp skip-whitespace)
+ (compare-windows-skip-whitespace opoint2)
+ (funcall skip-whitespace opoint2)))
+ (setq p2a (point))
+ (if (or (stringp skip-whitespace)
+ (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)
+ success-1
+ (case-fold-search compare-ignore-case))
(while (> size 0)
(setq success-1 t)
+ ;; Try comparing SIZE chars at a time, repeatedly, till that fails.
(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))))
+ (= 0 (compare-buffer-substrings b2 p2 (+ size p2)
+ b1 p1 (+ size p1)))))
(if success-1
(setq p1 (+ p1 size) p2 (+ p2 size)
success t)))
+ ;; If SIZE chars don't match, try fewer.
(setq size (/ size 2)))))
(goto-char p1)
(if (= (point) opoint1)
(ding))))
+;; Move forward over whatever might be called whitespace.
+;; compare-windows-whitespace is a regexp that matches whitespace.
+;; Match it at various starting points before the original point
+;; and find the latest point at which a match ends.
+;; Don't try starting points before START, though.
+;; Value is non-nil if whitespace is found.
+
+;; If there is whitespace before point, but none after,
+;; then return t, but don't advance point.
+(defun compare-windows-skip-whitespace (start)
+ (let ((end (point))
+ (beg (point))
+ (opoint (point)))
+ (while (or (and (looking-at compare-windows-whitespace)
+ (<= end (match-end 0))
+ ;; This match goes past END, so advance END.
+ (progn (setq end (match-end 0))
+ (> (point) start)))
+ (and (/= (point) start)
+ ;; Consider at least the char before point,
+ ;; unless it is also before START.
+ (= (point) opoint)))
+ ;; keep going back until whitespace
+ ;; doesn't extend to or past end
+ (forward-char -1))
+ (setq beg (point))
+ (goto-char end)
+ (or (/= beg opoint)
+ (/= end opoint))))
+
(provide 'compare-w)
;;; compare-w.el ends here