X-Git-Url: https://code.delx.au/gnu-emacs/blobdiff_plain/f36d46caffc209065f29e7e7fa8daa01994d2e88..1bf6d4b5c112dbf6233ff2cfc3b85adfa6cbd291:/lisp/files.el

diff --git a/lisp/files.el b/lisp/files.el
index 112056e4f9..fee3a5ea65 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -1,7 +1,8 @@
 ;;; files.el --- file input and output commands for Emacs
 
-;; Copyright (C) 1985, 1986, 1987, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
-;;   1999, 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
+;; Copyright (C) 1985, 1986, 1987, 1992, 1993, 1994, 1995, 1996,
+;;   1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
+;;   2006 Free Software Foundation, Inc.
 
 ;; Maintainer: FSF
 
@@ -2047,6 +2048,9 @@ to decide the buffer's major mode.
 If FUNCTION is nil, then it is not called.  (That is a way of saying
 \"allow `auto-mode-alist' to decide for these files.\")")
 
+(defvar magic-mode-regexp-match-limit 4000
+  "Upper limit on `magic-mode-alist' regexp matches.")
+
 (defun set-auto-mode (&optional keep-mode-if-same)
   "Select major mode appropriate for current buffer.
 
@@ -2120,9 +2124,13 @@ only set the major mode, if that would change it."
     (unless done
       (if (setq done (save-excursion
 		       (goto-char (point-min))
-		       (assoc-default nil magic-mode-alist
-				      (lambda (re dummy)
-					(looking-at re)))))
+		       (save-restriction
+			 (narrow-to-region (point-min)
+					   (min (point-max)
+						(+ (point-min) magic-mode-regexp-match-limit)))
+			 (assoc-default nil magic-mode-alist
+					(lambda (re dummy)
+					  (looking-at re))))))
 	  (set-auto-mode-0 done keep-mode-if-same)
 	;; Compare the filename against the entries in auto-mode-alist.
 	(if buffer-file-name