BSD 4_3 development

Work on file usr/contrib/emacs/lisp/compare-w.el

Synthesized-from: CSRG/cd1/4.3

diff --git a/usr/contrib/emacs/lisp/compare-w.el b/usr/contrib/emacs/lisp/compare-w.el
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+;; Compare text between windows for Emacs.
+;; Copyright (C) 1985 Richard M. Stallman.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY.  No author or distributor
+;; accepts responsibility to anyone for the consequences of using it
+;; or for whether it serves any particular purpose or works at all,
+;; unless he says so in writing.  Refer to the GNU Emacs General Public
+;; License for full details.
+
+;; Everyone is granted permission to copy, modify and redistribute
+;; GNU Emacs, but only under the conditions described in the
+;; GNU Emacs General Public License.   A copy of this license is
+;; supposed to have been given to you along with GNU Emacs so you
+;; can know your rights and responsibilities.  It should be in a
+;; file named COPYING.  Among other things, the copyright notice
+;; and this notice must be preserved on all copies.
+
+
+(defun compare-windows ()
+  "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."
+  (interactive)
+  (let (p1 p2 np1 np2 maxp1 maxp2 b1 b2 w2
+          success size
+          (opoint (point)))
+    (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 maxp1 (point-max))
+    (save-excursion
+     (set-buffer b2)
+     (setq maxp2 (point-max)))
+
+    (setq losep1 (+ 10 maxp1) losep2 (+ 10 maxp2))
+
+    ;; Try advancing comparing 1000 chars at a time.
+    ;; When that fails, go 500 chars at a time, and so on.
+    (setq size 1000)
+    (while (> size 0)
+      (setq success t)
+      (while success
+       (setq np2 (min (+ p2 size) maxp2))
+       (setq np1 (min (+ p1 size) maxp1))
+       (save-excursion
+        (set-buffer b2)
+        (setq s2 (buffer-substring p2 np2)))
+       (setq s1 (buffer-substring p1 np1))
+       (setq success (and (/= np1 p1) (equal s1 s2)))
+       ;; Don't bother retrying the last fraction of what already lost.
+       (and success
+            (or (> (+ p2 size) (- losep2 3))
+                (> (+ p1 size) (- losep1 3)))
+            (> size 1)
+            (setq success nil))
+       (if success
+           (setq p1 np1 p2 np2)
+         (setq losep1 np1 losep2 np2
+               maxp1 np1 maxp2 np2)))
+      (setq size (min (- maxp1 p1) (- maxp2 p2) (/ size 2))))
+
+    (goto-char p1)
+    (set-window-point w2 p2)
+    (if (= (point) opoint)
+       (ding))))