(rmail-redecode-body): Don't encode/decode the message; instead, just rewrite

the X-Coding-System header with the new encoding, and let rmail-show-message
do the rest.  Remove unused argument RAW.  Fix doc string to be consistent
with the new implementation.
(rmail-show-message): Honor X-Coding-System header, if present, in preference
to Content-Type header.

2 files changed, 36 insertions, 62 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index d9ff7e63911..a15576965b5 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,13 @@
+2009-02-07  Eli Zaretskii  <eliz@gnu.org>
+
+        * mail/rmail.el (rmail-redecode-body): Don't encode/decode the
+        message; instead, just rewrite the X-Coding-System header with the
+        new encoding, and let rmail-show-message do the rest.  Remove
+        unused argument RAW.  Fix doc string to be consistent with the new
+        implementation.
+        (rmail-show-message): Honor X-Coding-System header, if present, in
+        preference to Content-Type header.
+
 2009-02-07  Stefan Monnier  <monnier@iro.umontreal.ca>
 
         * server.el (server-execute): Enable quit.
diff --git a/lisp/mail/rmail.el b/lisp/mail/rmail.el
index ab8490938d3..947564773ff 100644
--- a/lisp/mail/rmail.el
+++ b/lisp/mail/rmail.el
@@ -2549,9 +2549,12 @@ The current mail message becomes the message displayed."
         (setq body-start (search-forward "\n\n" nil t))
         (narrow-to-region beg (point))
         (goto-char beg)
+        (save-excursion
+          (if (re-search-forward "^X-Coding-System: *\\(.*\\)$" nil t)
+              (setq coding-system (intern (match-string 1)))
+            (setq coding-system (rmail-get-coding-system))))
         (setq character-coding (mail-fetch-field "content-transfer-encoding")
-              is-text-message (rmail-is-text-p)
-              coding-system (rmail-get-coding-system))
+              is-text-message (rmail-is-text-p))
         (if character-coding
             (setq character-coding (downcase character-coding)))
         (narrow-to-region beg end)
@@ -2666,40 +2669,22 @@ buffer to the end of the headers."
                 (goto-char lim))))
            (t (error "No headers selected for display!"))))))))
 
-(defun rmail-redecode-body (coding &optional raw)
+(defun rmail-redecode-body (coding)
   "Decode the body of the current message using coding system CODING.
 This is useful with mail messages that have malformed or missing
 charset= headers.
 
 This function assumes that the current message is already decoded
 and displayed in the RMAIL buffer, but the coding system used to
-decode it was incorrect.  It then encodes the message back to its
-original form, and decodes it again, using the coding system CODING.
-
-Optional argument RAW, if non-nil, means don't encode the message
-before decoding it with the new CODING.  This is useful if the current
-message text was produced by some function which invokes `insert',
-since `insert' leaves unibyte character codes 128 through 255 unconverted
-to multibyte.  One example of such a situation is when the text was
-produced by `base64-decode-region'.
-
-Interactively, invoke the function with a prefix argument to set RAW
-non-nil.
-
-Note that if Emacs erroneously auto-detected one of the iso-2022
-encodings in the message, this function might fail because the escape
-sequences that switch between character sets and also single-shift and
-locking-shift codes are impossible to recover.  This function is meant
-to be used to fix messages encoded with 8-bit encodings, such as
-iso-8859, koi8-r, etc."
+decode it was incorrect.  It then decodes the message again,
+using the coding system CODING."
   (interactive "zCoding system for re-decoding this message: ")
   (when (not rmail-enable-mime)
     (with-current-buffer rmail-buffer
       (rmail-swap-buffers-maybe)
       (save-restriction
         (widen)
-        (let ((raw (or raw current-prefix-arg))
-              (msgbeg (rmail-msgbeg rmail-current-message))
+        (let ((msgbeg (rmail-msgbeg rmail-current-message))
               (msgend (rmail-msgend rmail-current-message))
               (buffer-read-only nil)
               body-start x-coding-header old-coding)
@@ -2711,10 +2696,11 @@ iso-8859, koi8-r, etc."
           (save-restriction
             ;; Narrow to headers
             (narrow-to-region (point-min) body-start)
-            (goto-char (point-min))
-            (unless (re-search-forward "^X-Coding-System: *\\(.*\\)$" nil t)
-              (error "No X-Coding-System header found"))
-            (setq old-coding (intern (match-string 1)))
+            (setq x-coding-header (goto-char (point-min)))
+            (if (not (re-search-forward "^X-Coding-System: *\\(.*\\)$" nil t))
+                (setq old-coding (rmail-get-coding-system))
+              (setq old-coding (intern (match-string 1)))
+              (setq x-coding-header (point)))
             (check-coding-system old-coding)
             ;; Make sure the new coding system uses the same EOL
             ;; conversion, to prevent ^M characters from popping up
@@ -2723,40 +2709,18 @@ iso-8859, koi8-r, etc."
               (if (numberp eol-type)
                   (setq coding
                         (coding-system-change-eol-conversion coding eol-type))))
-            ;; If old-coding is `undecided', encode-coding-region
-            ;; will not encode the text at all.  Find a proper
-            ;; non-trivial encoding to use.
-            (when (memq (coding-system-base old-coding) '(nil undecided))
-              (setq old-coding
-                    (car (find-coding-systems-region msgbeg msgend))))
-            (setq x-coding-header (point)))
-
-          (save-restriction
-            ;; Narrow to message body
-            (narrow-to-region body-start (point-max))
-            (and (null raw)
-                 ;; If old and new encoding are the same, it
-                 ;; clearly doesn't make sense to encode.
-                 (not (coding-system-equal
-                       (coding-system-base old-coding)
-                       (coding-system-base coding)))
-                 ;; If the body includes only eight-bit characters,
-                 ;; encoding might fail, e.g. with UTF-8, and isn't
-                 ;; needed anyway.
-                 (> (length (delq 'ascii
-                                  (delq 'eight-bit
-                                        (find-charset-region
-                                         (point-min) (point-max)))))
-                    0)
-                 (encode-coding-region (point-min) (point-max) old-coding))
-            (decode-coding-region (point-min) (point-max) coding)
-            (setq last-coding-system-used coding))
-
-          ;; Rewrite the coding-system header.
-          (goto-char x-coding-header)
-          (delete-region (line-beginning-position) (point))
-          (insert "X-Coding-System: "
-                  (symbol-name last-coding-system-used))
+            (when (not (coding-system-equal
+                        (coding-system-base old-coding)
+                        (coding-system-base coding)))
+              ;; Rewrite the coding-system header.
+              (goto-char x-coding-header)
+              (if (> (point) (point-min))
+                  (delete-region (line-beginning-position) (point))
+                (forward-line)
+                (insert "\n")
+                (forward-line -1))
+              (insert "X-Coding-System: "
+                      (symbol-name coding))))
           (rmail-show-message-maybe))))))
 
 ;; Find all occurrences of certain fields, and highlight them.