(set-auto-coding): Argument is changed to SIZE.

1 files changed, 68 insertions, 64 deletions

diff --git a/lisp/international/mule.el b/lisp/international/mule.el
index b085b90b70f..a1a863c064c 100644
--- a/lisp/international/mule.el
+++ b/lisp/international/mule.el
@@ -774,78 +774,82 @@ LIST is a list of coding categories ordered by priority."
 
 ;;; FILE I/O
 
-(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.
+(defun set-auto-coding (size)
+  "Return coding system for a file of which SIZE bytes follow point.
 
-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.
+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.
 
 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."
-  (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))))
+  (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)))
               (or (coding-system-p coding-system)
-                  (setq coding-system nil)))))
-
-        coding-system)
-    (error nil)))
+                  (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 set-auto-coding-function 'set-auto-coding)