(rfc2047-encoded-word-regexp): Support RFC 2231

[gnus] / lisp / rfc2047.el

diff --git a/lisp/rfc2047.el b/lisp/rfc2047.el
index ba25cfc..ebd8a4a 100644 (file)
--- a/lisp/rfc2047.el
+++ b/lisp/rfc2047.el
@@ -38,23 +38,12 @@
 (require 'base64)
 (autoload 'mm-body-7-or-8 "mm-bodies")
 
 (require 'base64)
 (autoload 'mm-body-7-or-8 "mm-bodies")
 

-;; Avoid gnus-util for mm- code.
-(defalias 'rfc2047-point-at-bol
-  (if (fboundp 'point-at-bol)
-      'point-at-bol
-    'line-beginning-position))
-
-(defalias 'rfc2047-point-at-eol
-  (if (fboundp 'point-at-eol)
-      'point-at-eol
-    'line-end-position))
-

 (defvar rfc2047-header-encoding-alist
   '(("Newsgroups" . nil)
     ("Followup-To" . nil)
     ("Message-ID" . nil)
 (defvar rfc2047-header-encoding-alist
   '(("Newsgroups" . nil)
     ("Followup-To" . nil)
     ("Message-ID" . nil)

-    ("\\(Resent-\\)?\\(From\\|Cc\\|To\\|Bcc\\|Reply-To\\|Sender\\)" .
-     address-mime)
+    ("\\(Resent-\\)?\\(From\\|Cc\\|To\\|Bcc\\|Reply-To\\|Sender\
+\\|Mail-Followup-To\\|Mail-Copies-To\\|Approved\\)" . address-mime)

     (t . mime))
   "*Header/encoding method alist.
 The list is traversed sequentially.  The keys can either be
     (t . mime))
   "*Header/encoding method alist.
 The list is traversed sequentially.  The keys can either be


@@ -92,7 +81,8 @@ The values can be:
     (cn-gb-2312 . B)
     (euc-kr . B)
     (iso-2022-jp-2 . B)
     (cn-gb-2312 . B)
     (euc-kr . B)
     (iso-2022-jp-2 . B)

-    (iso-2022-int-1 . B))
+    (iso-2022-int-1 . B)
+    (viscii . Q))

   "Alist of MIME charsets to RFC2047 encodings.
 Valid encodings are nil, `Q' and `B'.  These indicate binary (no) encoding,
 quoted-printable and base64 respectively.")
   "Alist of MIME charsets to RFC2047 encodings.
 Valid encodings are nil, `Q' and `B'.  These indicate binary (no) encoding,
 quoted-printable and base64 respectively.")


@@ -103,19 +93,29 @@ quoted-printable and base64 respectively.")
     (nil . ignore))
   "Alist of RFC2047 encodings to encoding functions.")
 
     (nil . ignore))
   "Alist of RFC2047 encodings to encoding functions.")
 

-(defvar rfc2047-q-encoding-alist
-  '(("\\(Resent-\\)?\\(From\\|Cc\\|To\\|Bcc\\|Reply-To\\|Sender\\):"
-     . "-A-Za-z0-9!*+/" )
-    ;; = (\075), _ (\137), ? (\077) are used in the encoded word.
-    ;; Avoid using 8bit characters.
-    ;; Equivalent to "^\000-\007\011\013\015-\037\200-\377=_?"
-    ("." . "\010\012\014\040-\074\076\100-\136\140-\177"))
-  "Alist of header regexps and valid Q characters.")
-

 ;;;
 ;;; Functions for encoding RFC2047 messages
 ;;;
 
 ;;;
 ;;; Functions for encoding RFC2047 messages
 ;;;
 

+(defun rfc2047-qp-or-base64 ()
+  "Return the type with which to encode the buffer.
+This is either `base64' or `quoted-printable'."
+  (save-excursion
+    (let ((limit (min (point-max) (+ 2000 (point-min))))
+         (n8bit 0))
+      (goto-char (point-min))
+      (skip-chars-forward "\x20-\x7f\r\n\t" limit)
+      (while (< (point) limit)
+       (incf n8bit)
+       (forward-char 1)
+       (skip-chars-forward "\x20-\x7f\r\n\t" limit))
+      (if (or (< (* 6 n8bit) (- limit (point-min)))
+             ;; Don't base64, say, a short line with a single
+             ;; non-ASCII char when splitting parts by charset.
+             (= n8bit 1))
+         'quoted-printable
+       'base64))))
+

 (defun rfc2047-narrow-to-field ()
   "Narrow the buffer to the header on the current line."
   (beginning-of-line)
 (defun rfc2047-narrow-to-field ()
   "Narrow the buffer to the header on the current line."
   (beginning-of-line)


@@ -124,9 +124,7 @@ quoted-printable and base64 respectively.")
    (progn
      (forward-line 1)
      (if (re-search-forward "^[^ \n\t]" nil t)
    (progn
      (forward-line 1)
      (if (re-search-forward "^[^ \n\t]" nil t)

-        (progn
-          (beginning-of-line)
-          (point))
+        (point-at-bol)

        (point-max))))
   (goto-char (point-min)))
 
        (point-max))))
   (goto-char (point-min)))
 


@@ -189,7 +187,7 @@ Should be called narrowed to the head of the message."
             ((eq method 'address-mime)
              (rfc2047-encode-region (point) (point-max)))
             ((eq method 'mime)
             ((eq method 'address-mime)
              (rfc2047-encode-region (point) (point-max)))
             ((eq method 'mime)

-             (let (rfc2047-encoding-type)
+             (let ((rfc2047-encoding-type 'mime))

                (rfc2047-encode-region (point) (point-max))))
             ((eq method 'default)
              (if (and (featurep 'mule)
                (rfc2047-encode-region (point) (point-max))))
             ((eq method 'default)
              (if (and (featurep 'mule)


@@ -237,7 +235,8 @@ The buffer may be narrowed."
   (require 'message)                   ; for message-posting-charset
   (let ((charsets
         (mm-find-mime-charset-region (point-min) (point-max))))
   (require 'message)                   ; for message-posting-charset
   (let ((charsets
         (mm-find-mime-charset-region (point-min) (point-max))))

-    (and charsets (not (equal charsets (list message-posting-charset))))))
+    (and charsets
+        (not (equal charsets (list (car message-posting-charset)))))))

 
 ;; Use this syntax table when parsing into regions that may need
 ;; encoding.  Double quotes are string delimiters, backslash is
 
 ;; Use this syntax table when parsing into regions that may need
 ;; encoding.  Double quotes are string delimiters, backslash is


@@ -246,7 +245,19 @@ The buffer may be narrowed."
 ;; skip to the end of regions appropriately.  Nb. ietf-drums does
 ;; things differently.
 (defconst rfc2047-syntax-table
 ;; skip to the end of regions appropriately.  Nb. ietf-drums does
 ;; things differently.
 (defconst rfc2047-syntax-table

-  (let ((table (make-char-table 'syntax-table '(2))))
+  ;; (make-char-table 'syntax-table '(2)) only works in Emacs.
+  (let ((table (make-syntax-table)))
+    ;; The following is done to work for setting all elements of the table
+    ;; in Emacs 21 and 22 and XEmacs; it appears to be the cleanest way.
+    ;; Play safe and don't assume the form of the word syntax entry --
+    ;; copy it from ?a.
+    (if (fboundp 'set-char-table-range)        ; Emacs
+       (funcall (intern "set-char-table-range")
+                table t (aref (standard-syntax-table) ?a))
+      (if (fboundp 'put-char-table)
+         (if (fboundp 'get-char-table) ; warning avoidance
+             (put-char-table t (get-char-table ?a (standard-syntax-table))
+                             table))))

     (modify-syntax-entry ?\\ "\\" table)
     (modify-syntax-entry ?\" "\"" table)
     (modify-syntax-entry ?\( "." table)
     (modify-syntax-entry ?\\ "\\" table)
     (modify-syntax-entry ?\" "\"" table)
     (modify-syntax-entry ?\( "." table)


@@ -268,13 +279,23 @@ Dynamically bind `rfc2047-encoding-type' to change that."
   (save-restriction
     (narrow-to-region b e)
     (if (eq 'mime rfc2047-encoding-type)
   (save-restriction
     (narrow-to-region b e)
     (if (eq 'mime rfc2047-encoding-type)

-       ;; Simple case -- treat as single word.
+       ;; Simple case.  Treat as single word after any initial ASCII
+       ;; part and before any tailing ASCII part.  The leading ASCII
+       ;; is relevant for instance in Subject headers with `Re:' for
+       ;; interoperability with non-MIME clients, and we might as
+       ;; well avoid the tail too.

        (progn
          (goto-char (point-min))
          ;; Does it need encoding?
        (progn
          (goto-char (point-min))
          ;; Does it need encoding?

-         (skip-chars-forward "\000-\177" e)
+         (skip-chars-forward "\000-\177")

          (unless (eobp)
          (unless (eobp)

-           (rfc2047-encode b e)))
+           (skip-chars-backward "^ \n") ; beginning of space-delimited word
+           (rfc2047-encode (point) (progn
+                                     (goto-char e)
+                                     (skip-chars-backward "\000-\177")
+                                     (skip-chars-forward "^ \n")
+                                     ;; end of space-delimited word
+                                     (point)))))

       ;; `address-mime' case -- take care of quoted words, comments.
       (with-syntax-table rfc2047-syntax-table
        (let ((start)                   ; start of current token
       ;; `address-mime' case -- take care of quoted words, comments.
       (with-syntax-table rfc2047-syntax-table
        (let ((start)                   ; start of current token


@@ -283,14 +304,14 @@ Dynamically bind `rfc2047-encoding-type' to change that."
              ;; token, either immediately or separated by space.
              last-encoded)
          (goto-char (point-min))
              ;; token, either immediately or separated by space.
              last-encoded)
          (goto-char (point-min))

-         (condition-case nil         ; in case of unbalanced quotes
+         (condition-case nil           ; in case of unbalanced quotes

              ;; Look for rfc2822-style: sequences of atoms, quoted
              ;; strings, specials, whitespace.  (Specials mustn't be
              ;; encoded.)
              (while (not (eobp))
                (setq start (point))
                ;; Skip whitespace.
              ;; Look for rfc2822-style: sequences of atoms, quoted
              ;; strings, specials, whitespace.  (Specials mustn't be
              ;; encoded.)
              (while (not (eobp))
                (setq start (point))
                ;; Skip whitespace.

-               (unless (= 0 (skip-chars-forward " \t"))
+               (unless (= 0 (skip-chars-forward " \t\n"))

                  (setq start (point)))
                (cond
                 ((not (char-after)))   ; eob
                  (setq start (point)))
                (cond
                 ((not (char-after)))   ; eob


@@ -346,14 +367,15 @@ Dynamically bind `rfc2047-encoding-type' to change that."
                            end (1+ end)))
                    (rfc2047-encode start end)
                    (setq last-encoded t)))))
                            end (1+ end)))
                    (rfc2047-encode start end)
                    (setq last-encoded t)))))

-           (error (error "Invalid data for rfc2047 encoding: %s"
-                         (buffer-substring b e)))))))
+           (error
+            (error "Invalid data for rfc2047 encoding: %s"
+                   (buffer-substring b e)))))))

     (rfc2047-fold-region b (point))))
 
 (defun rfc2047-encode-string (string)
   "Encode words in STRING.
 By default, the string is treated as containing addresses (see
     (rfc2047-fold-region b (point))))
 
 (defun rfc2047-encode-string (string)
   "Encode words in STRING.
 By default, the string is treated as containing addresses (see

-`rfc2047-special-chars')."
+`rfc2047-encoding-type')."

   (with-temp-buffer
     (insert string)
     (rfc2047-encode-region (point-min) (point-max))
   (with-temp-buffer
     (insert string)
     (rfc2047-encode-region (point-min) (point-max))


@@ -362,7 +384,7 @@ By default, the string is treated as containing addresses (see
 (defun rfc2047-encode (b e)
   "Encode the word(s) in the region B to E.
 By default, the region is treated as containing addresses (see
 (defun rfc2047-encode (b e)
   "Encode the word(s) in the region B to E.
 By default, the region is treated as containing addresses (see

-`rfc2047-special-chars')."
+`rfc2047-encoding-type')."

   (let* ((mime-charset (mm-find-mime-charset-region b e))
         (cs (if (> (length mime-charset) 1)
                 ;; Fixme: Instead of this, try to break region into
   (let* ((mime-charset (mm-find-mime-charset-region b e))
         (cs (if (> (length mime-charset) 1)
                 ;; Fixme: Instead of this, try to break region into


@@ -373,14 +395,36 @@ By default, the region is treated as containing addresses (see
               (mm-charset-to-coding-system mime-charset)))
         ;; Fixme: Better, calculate the number of non-ASCII
         ;; characters, at least for 8-bit charsets.
               (mm-charset-to-coding-system mime-charset)))
         ;; Fixme: Better, calculate the number of non-ASCII
         ;; characters, at least for 8-bit charsets.

-        (encoding (if (assq mime-charset
-                            rfc2047-charset-encoding-alist)
-                      (cdr (assq mime-charset
+        (encoding (or (cdr (assq mime-charset

                                  rfc2047-charset-encoding-alist))
                                  rfc2047-charset-encoding-alist))

-                    'B))
+                      ;; For the charsets that don't have a preferred
+                      ;; encoding, choose the one that's shorter.
+                      (save-restriction
+                        (narrow-to-region b e)
+                        (if (eq (rfc2047-qp-or-base64) 'base64)
+                            'B
+                          'Q))))

         (start (concat
                 "=?" (downcase (symbol-name mime-charset)) "?"
                 (downcase (symbol-name encoding)) "?"))
         (start (concat
                 "=?" (downcase (symbol-name mime-charset)) "?"
                 (downcase (symbol-name encoding)) "?"))

+        (factor (case mime-charset
+                  ((iso-8859-5 iso-8859-7 iso-8859-8 koi8-r) 1)
+                  ((big5 gb2312 euc-kr) 2)
+                  (utf-8 4)
+                  (t 8)))
+        (pre (- b (save-restriction
+                    (widen)
+                    (point-at-bol))))
+        ;; encoded-words must not be longer than 75 characters,
+        ;; including charset, encoding etc.  This leaves us with
+        ;; 75 - (length start) - 2 - 2 characters.  The last 2 is for
+        ;; possible base64 padding.  In the worst case (iso-2022-*)
+        ;; each character expands to 8 bytes which is expanded by a
+        ;; factor of 4/3 by base64 encoding.
+        (length (floor (- 75 (length start) 4) (* factor (/ 4.0 3.0))))
+        ;; Limit line length to 76 characters.
+        (length1 (max 1 (floor (- 76 (length start) 4 pre)
+                               (* factor (/ 4.0 3.0)))))

         (first t))
     (if mime-charset
        (save-restriction
         (first t))
     (if mime-charset
        (save-restriction


@@ -389,9 +433,14 @@ By default, the region is treated as containing addresses (see
            ;; break into lines before encoding
            (goto-char (point-min))
            (while (not (eobp))
            ;; break into lines before encoding
            (goto-char (point-min))
            (while (not (eobp))

-             (goto-char (min (point-max) (+ 15 (point))))
+             (if first
+                 (progn
+                   (goto-char (min (point-max) (+ length1 (point))))
+                   (setq first nil))
+               (goto-char (min (point-max) (+ length (point)))))

              (unless (eobp)
              (unless (eobp)

-               (insert ?\n))))
+               (insert ?\n)))
+           (setq first t))

          (if (and (mm-multibyte-p)
                   (mm-coding-system-p cs))
              (mm-encode-coding-region (point-min) (point-max) cs))
          (if (and (mm-multibyte-p)
                   (mm-coding-system-p cs))
              (mm-encode-coding-region (point-min) (point-max) cs))


@@ -424,7 +473,7 @@ By default, the region is treated as containing addresses (see
          (first t)
          (bol (save-restriction
                 (widen)
          (first t)
          (bol (save-restriction
                 (widen)

-                (rfc2047-point-at-bol))))
+                (point-at-bol))))

       (while (not (eobp))
        (when (and (or break qword-break)
                   (> (- (point) bol) 76))
       (while (not (eobp))
        (when (and (or break qword-break)
                   (> (- (point) bol) 76))


@@ -461,7 +510,9 @@ By default, the region is treated as containing addresses (see
              (if (eq (char-after) ?=)
                  (forward-char 1)
                (skip-chars-forward "^ \t\n\r="))
              (if (eq (char-after) ?=)
                  (forward-char 1)
                (skip-chars-forward "^ \t\n\r="))

-           (setq qword-break (point))
+           ;; Don't break at the start of the field.
+           (unless (= (point) b)
+             (setq qword-break (point)))

            (skip-chars-forward "^ \t\n\r")))
         (t
          (skip-chars-forward "^ \t\n\r"))))
            (skip-chars-forward "^ \t\n\r")))
         (t
          (skip-chars-forward "^ \t\n\r"))))


@@ -493,19 +544,18 @@ By default, the region is treated as containing addresses (see
     (goto-char (point-min))
     (let ((bol (save-restriction
                 (widen)
     (goto-char (point-min))
     (let ((bol (save-restriction
                 (widen)

-                (rfc2047-point-at-bol)))
-         (eol (rfc2047-point-at-eol))
-         leading)
+                (point-at-bol)))
+         (eol (point-at-eol)))

       (forward-line 1)
       (while (not (eobp))
        (if (and (looking-at "[ \t]")
       (forward-line 1)
       (while (not (eobp))
        (if (and (looking-at "[ \t]")

-                (< (- (rfc2047-point-at-eol) bol) 76))
+                (< (- (point-at-eol) bol) 76))

            (delete-region eol (progn
                                 (goto-char eol)
                                 (skip-chars-forward "\r\n")
                                 (point)))
            (delete-region eol (progn
                                 (goto-char eol)
                                 (skip-chars-forward "\r\n")
                                 (point)))

-         (setq bol (rfc2047-point-at-bol)))
-       (setq eol (rfc2047-point-at-eol))
+         (setq bol (point-at-bol)))
+       (setq eol (point-at-eol))

        (forward-line 1)))))
 
 (defun rfc2047-b-encode-region (b e)
        (forward-line 1)))))
 
 (defun rfc2047-b-encode-region (b e)


@@ -523,16 +573,21 @@ By default, the region is treated as containing addresses (see
   (save-excursion
     (save-restriction
       (narrow-to-region (goto-char b) e)
   (save-excursion
     (save-restriction
       (narrow-to-region (goto-char b) e)

-      (let ((alist rfc2047-q-encoding-alist)
-           (bol (save-restriction
+      (let ((bol (save-restriction

                   (widen)
                   (widen)

-                  (rfc2047-point-at-bol))))
-       (while alist
-         (when (looking-at (caar alist))
-           (quoted-printable-encode-region b e nil (cdar alist))
-           (subst-char-in-region (point-min) (point-max) ?  ?_)
-           (setq alist nil))
-         (pop alist))
+                  (point-at-bol))))
+       (quoted-printable-encode-region
+        b e nil
+        ;; = (\075), _ (\137), ? (\077) are used in the encoded word.
+        ;; Avoid using 8bit characters.
+        ;; This list excludes `especials' (see the RFC2047 syntax),
+        ;; meaning that some characters in non-structured fields will
+        ;; get encoded when they con't need to be.  The following is
+        ;; what it used to be.
+;;;     ;; Equivalent to "^\000-\007\011\013\015-\037\200-\377=_?"
+;;;     "\010\012\014\040-\074\076\100-\136\140-\177")
+        "-\b\n\f !#-'*+0-9A-Z\\^`-~\d")
+       (subst-char-in-region (point-min) (point-max) ?  ?_)

        ;; The size of QP encapsulation is about 20, so set limit to
        ;; 56=76-20.
        (unless (< (- (point-max) (point-min)) 56)
        ;; The size of QP encapsulation is about 20, so set limit to
        ;; 56=76-20.
        (unless (< (- (point-max) (point-min)) 56)


@@ -552,13 +607,19 @@ By default, the region is treated as containing addresses (see
 
 (eval-and-compile
   (defconst rfc2047-encoded-word-regexp
 
 (eval-and-compile
   (defconst rfc2047-encoded-word-regexp

-    "=\\?\\([^][\000-\040()<>@,\;:\\\"/?.=]+\\)\\?\\(B\\|Q\\)\
-\\?\\([!->@-~ +]*\\)\\?="))
+    "=\\?\\([^][\000-\040()<>@,\;:*\\\"/?.=]+\\)(?:\\*[^?]+\\)?\
+\\?\\(B\\|Q\\)\\?\\([!->@-~ +]*\\)\\?="))

 
 ;; Fixme: This should decode in place, not cons intermediate strings.
 ;; Also check whether it needs to worry about delimiting fields like
 ;; encoding.
 
 
 ;; Fixme: This should decode in place, not cons intermediate strings.
 ;; Also check whether it needs to worry about delimiting fields like
 ;; encoding.
 

+;; In fact it's reported that (invalid) encoding of mailboxes in
+;; addr-specs is in use, so delimiting fields might help.  Probably
+;; not decoding a word which isn't properly delimited is good enough
+;; and worthwhile (is it more correct or not?), e.g. something like
+;; `=?iso-8859-1?q?foo?=@'.
+

 (defun rfc2047-decode-region (start end)
   "Decode MIME-encoded words in region between START and END."
   (interactive "r")
 (defun rfc2047-decode-region (start end)
   "Decode MIME-encoded words in region between START and END."
   (interactive "r")


@@ -609,18 +670,38 @@ By default, the region is treated as containing addresses (see
   (let ((m (mm-multibyte-p)))
     (if (string-match "=\\?" string)
        (with-temp-buffer
   (let ((m (mm-multibyte-p)))
     (if (string-match "=\\?" string)
        (with-temp-buffer

+         ;; Fixme: This logic is wrong, but seems to be required by
+         ;; Gnus summary buffer generation.  The value of `m' depends
+         ;; on the current buffer, not global multibyteness or that
+         ;; of the string.  Also the string returned should always be
+         ;; multibyte in a multibyte session, i.e. the buffer should
+         ;; be multibyte before `buffer-string' is called.

          (when m
            (mm-enable-multibyte))
          (insert string)
          (inline
            (rfc2047-decode-region (point-min) (point-max)))
          (when m
            (mm-enable-multibyte))
          (insert string)
          (inline
            (rfc2047-decode-region (point-min) (point-max)))

-         (mm-enable-multibyte)
-         (buffer-string)))
-    (if (and mail-parse-charset
-            (not (eq mail-parse-charset 'us-ascii))
-            (not (eq mail-parse-charset 'gnus-decoded)))
-       (mm-decode-coding-string string mail-parse-charset)
-      (mm-string-as-multibyte string))))
+         (buffer-string))
+      ;; Fixme: As above, `m' here is inappropriate.
+      (if (and m
+              mail-parse-charset
+              (not (eq mail-parse-charset 'us-ascii))
+              (not (eq mail-parse-charset 'gnus-decoded)))
+         ;; `decode-coding-string' in Emacs offers a third optional
+         ;; arg NOCOPY to avoid consing a new string if the decoding
+         ;; is "trivial".  Unfortunately it currently doesn't
+         ;; consider anything else than a `nil' coding system
+         ;; trivial.
+         ;; `rfc2047-decode-string' is called multiple times for each
+         ;; article during summary buffer generation, and we really
+         ;; want to avoid unnecessary consing.  So we bypass
+         ;; `decode-coding-string' if the string is purely ASCII.
+         (if (and (fboundp 'detect-coding-string)
+                  ;; string is purely ASCII
+                  (eq (detect-coding-string string t) 'undecided))
+             string
+           (mm-decode-coding-string string mail-parse-charset))
+       (mm-string-as-multibyte string)))))

 
 (defun rfc2047-parse-and-decode (word)
   "Decode WORD and return it if it is an encoded word.
 
 (defun rfc2047-parse-and-decode (word)
   "Decode WORD and return it if it is an encoded word.


@@ -628,27 +709,33 @@ Return WORD if it is not not an encoded word or if the charset isn't
 decodable."
   (if (not (string-match rfc2047-encoded-word-regexp word))
       word
 decodable."
   (if (not (string-match rfc2047-encoded-word-regexp word))
       word

-    (condition-case nil
-       (rfc2047-decode
-        (match-string 1 word)
-        (upcase (match-string 2 word))
-        (match-string 3 word))
-      (error word))))
+    (or
+     (condition-case nil
+        (rfc2047-decode
+         (match-string 1 word)
+         (string-to-char (match-string 2 word))
+         (match-string 3 word))
+       (error word))
+     word)))                           ; un-decodable

 
 (defun rfc2047-pad-base64 (string)
   "Pad STRING to quartets."
   ;; Be more liberal to accept buggy base64 strings. If
   ;; base64-decode-string accepts buggy strings, this function could
   ;; be aliased to identity.
 
 (defun rfc2047-pad-base64 (string)
   "Pad STRING to quartets."
   ;; Be more liberal to accept buggy base64 strings. If
   ;; base64-decode-string accepts buggy strings, this function could
   ;; be aliased to identity.

-  (case (mod (length string) 4)
-    (0 string)
-    (1 string) ;; Error, don't pad it.
-    (2 (concat string "=="))
-    (3 (concat string "="))))
+  (if (= 0 (mod (length string) 4))
+      string
+    (when (string-match "=+$" string)
+      (setq string (substring string 0 (match-beginning 0))))
+    (case (mod (length string) 4)
+      (0 string)
+      (1 string) ;; Error, don't pad it.
+      (2 (concat string "=="))
+      (3 (concat string "=")))))

 
 (defun rfc2047-decode (charset encoding string)
   "Decode STRING from the given MIME CHARSET in the given ENCODING.
 
 (defun rfc2047-decode (charset encoding string)
   "Decode STRING from the given MIME CHARSET in the given ENCODING.

-Valid ENCODINGs are \"B\" and \"Q\".
+Valid ENCODINGs are the characters \"B\" and \"Q\".

 If your Emacs implementation can't decode CHARSET, return nil."
   (if (stringp charset)
       (setq charset (intern (downcase charset))))
 If your Emacs implementation can't decode CHARSET, return nil."
   (if (stringp charset)
       (setq charset (intern (downcase charset))))


@@ -666,19 +753,16 @@ If your Emacs implementation can't decode CHARSET, return nil."
       (when (and (eq cs 'ascii)
                 mail-parse-charset)
        (setq cs mail-parse-charset))
       (when (and (eq cs 'ascii)
                 mail-parse-charset)
        (setq cs mail-parse-charset))

-      ;; Fixme: What's this for?  The following comment makes no sense. -- fx
-      (mm-with-unibyte-current-buffer
-       ;; In Emacs Mule 4, decoding UTF-8 should be in unibyte mode.
-       (mm-decode-coding-string
-        (cond
-         ((equal "B" encoding)
-          (base64-decode-string
-           (rfc2047-pad-base64 string)))
-         ((equal "Q" encoding)
-          (quoted-printable-decode-string
-           (mm-replace-chars-in-string string ?_ ? )))
-         (t (error "Invalid encoding: %s" encoding)))
-        cs)))))
+      (mm-decode-coding-string
+       (cond
+       ((char-equal ?B encoding)
+        (base64-decode-string
+         (rfc2047-pad-base64 string)))
+       ((char-equal ?Q encoding)
+        (quoted-printable-decode-string
+         (mm-subst-char-in-string ?_ ? string t)))
+       (t (error "Invalid encoding: %c" encoding)))
+       cs))))

 
 (provide 'rfc2047)
 
 
 (provide 'rfc2047)