1 files changed, 64 insertions, 68 deletions

diff --git a/lisp/international/mule.el b/lisp/international/mule.el
index a1a863c064c..b085b90b70f 100644
--- a/lisp/international/mule.el
+++ b/lisp/international/mule.el
@@ -774,82 +774,78 @@ LIST is a list of coding categories ordered by priority."
 
 ;;; FILE I/O
 
-(defun set-auto-coding (size)
-  "Return coding system for a file of which SIZE bytes follow point.
+(defun set-auto-coding (string)
+  "Return coding system for a file which has STRING at the head and tail.
+STRING is a concatination of the first 1K-byte and
+ the last 3K-byte of the file.
 
-It checks for a -*- coding: tag in the first one or two lines
-following point.  If no coding: tag is found, it checks local
-variables spec in the last 3K-byte of SIZE bytes.
+It checks for a -*- coding: tag in the first one or two lines of STRING.
+If there's no coding: tag in the head, it checks local variables spec
+in the tailing 3K-byte oof STRING.
 
 The return value is the specified coding system,
 or nil if nothing specified.
 
 The variable `set-auto-coding-function' (which see) is set to this
 function by default."
-  (let* ((case-fold-search t)
-         (head-start (point))
-         (head-end (+ head-start (min size 1024)))
-         (tail-start (+ head-start (max (- size 3072) 0)))
-         (tail-end (+ head-start size))
-         coding-system head-found tail-found pos)
-    ;; Try a short cut by searching for the string "coding:" at the
-    ;; head and tail of SIZE bytes.
-    (setq head-found (search-forward "coding:" head-end t))
-    (if (and head-found (> head-found tail-start))
-        ;; Head and tail are overlapped.
-        (setq tail-found head-found)
-      (goto-char tail-start)
-      (setq tail-found (search-forward "coding:" tail-end t)))
-
-    ;; At first check the head.
-    (when head-found
-      (goto-char head-start)
-      (setq pos (re-search-forward "[\n\r]" head-end t))
-      (if (and pos
-               (= (char-after head-start) ?#)
-               (= (char-after (1+ head-start)) ?!))
-          ;; If the file begins with "#!" (exec interpreter magic),
-          ;; look for coding frobs in the first two lines.  You cannot
-          ;; necessarily put them in the first line of such a file
-          ;; without screwing up the interpreter invocation.
-          (setq pos (search-forward "\n" head-end t)))
-      (if pos (setq head-end pos))
-      (when (< head-found head-end)
-        (goto-char head-start)
-        (if (re-search-forward
-             "-\\*-\\(.*;\\)?[ \t]*coding:[ \t]*\\([^ ;]+\\)" head-end t)
-            (progn
-              (setq coding-system (intern (match-string 2)))
+  (condition-case nil
+      (let ((case-fold-search t)
+            (len (length string))
+            (limit (string-match "\n" string))
+            (coding-system nil))
+
+        ;; At first check the head.
+        (if limit
+            (when (string-match "^#!" string)
+              ;; If the file begins with "#!" (exec interpreter
+              ;; magic), look for coding frobs in the first two lines.
+              ;; You cannot necessarily put them in the first line of
+              ;; such a file without screwing up the interpreter
+              ;; invocation.
+              (setq limit (string-match "\n" string limit))
+              (or limit
+                  (setq limit len)))
+          (setq limit len))
+        (when (and (string-match "-\\*-\\(.*;\\)?[ \t]*coding:[ \t]*\\([^ ;]+\\)" string)
+                   (< (match-beginning 2) limit))
+          (setq coding-system
+                (intern (substring string (match-beginning 2) (match-end 2))))
+          (if (not (coding-system-p coding-system))
+              (setq coding-system nil)))
+
+        ;; If no coding system is specified in the head, check the tail.
+        (when (and (not coding-system)
+                   (let ((idx (if (> len 3000) (- len 3000) 0))
+                         start)
+                     (while (setq start (string-match "\n\^L" string idx))
+                       (setq idx (+ start 2)))
+                     (string-match
+                      "^\\(.*\\)[ \t]*Local Variables:[ \t]*\\(.*\\)$"
+                      string idx)))
+          ;; The prefix is what comes before "local variables:" in its line.
+          ;; The suffix is what comes after "local variables:" in its line.
+          (let* ((idx (1+ (match-end 0)))
+                 (prefix (regexp-quote
+                          (substring string
+                                     (match-beginning 1) (match-end 1))))
+                 (suffix (regexp-quote
+                          (substring string
+                                     (match-beginning 2) (match-end 2))))
+                 (re-coding (concat "^" prefix
+                                    "coding[ \t]*:[ \t]*\\([^ \t\n]+\\)[ \t]*"
+                                    suffix "$"))
+                 (re-end (concat "^" prefix "end *:[ \t]*" suffix "$"))
+                 (limit (or (string-match re-end string idx) len)))
+            (when (and (setq idx (string-match re-coding string idx))
+                       (< idx limit))
+              (setq coding-system
+                    (intern (substring string
+                                       (match-beginning 1) (match-end 1))))
               (or (coding-system-p coding-system)
-                  (setq coding-system nil))))))
-
-    ;; If no coding: tag in the head, check the tail.
-    (when (and tail-found (not coding-system))
-      (goto-char tail-start)
-      (search-forward "\n\^L" nil t)
-      (if (re-search-forward
-           "^\\(.*\\)[ \t]*Local Variables:[ \t]*\\(.*\\)$" tail-end t)
-          ;; The prefix is what comes before "local variables:" in its
-          ;; line.  The suffix is what comes after "local variables:"
-          ;; in its line.
-          (let* ((prefix (regexp-quote (match-string 1)))
-                 (suffix (regexp-quote (match-string 2)))
-                 (re-coding (concat
-                             "^" prefix
-                             "coding[ \t]*:[ \t]*\\([^ \t]+\\)[ \t]*"
-                             suffix "$"))
-                 (re-end (concat
-                          "^" prefix "end *:[ \t]*" suffix "$"))
-                 (pos (point)))
-            (re-search-forward re-end tail-end 'move)
-            (setq tail-end (point))
-            (goto-char pos)
-            (if (re-search-forward re-coding tail-end t)
-                (progn
-                  (setq coding-system (intern (match-string 1)))
-                  (or (coding-system-p coding-system)
-                      (setq coding-system nil)))))))
-    coding-system))
+                  (setq coding-system nil)))))
+
+        coding-system)
+    (error nil)))
 
 (setq set-auto-coding-function 'set-auto-coding)