Importing Gnus v5.8.3.

[elisp/gnus.git-] / lisp / mm-encode.el

diff --git a/lisp/mm-encode.el b/lisp/mm-encode.el
index 251ed57..7d8763b 100644 (file)
--- a/lisp/mm-encode.el
+++ b/lisp/mm-encode.el
@@ -38,6 +38,18 @@
 If the encoding is `qp-or-base64', then either quoted-printable
 or base64 will be used, depending on what is more efficient.")
 
+(defvar mm-use-ultra-safe-encoding nil
+  "If non-nil, use encodings aimed at Procrustean bed survival.
+
+This means that textual parts are encoded as quoted-printable if they
+contain lines longer than 76 characters or starting with \"From \" in
+the body.  Non-7bit encodings (8bit, binary) are generally disallowed.
+This is to reduce the probability that a broken MTA or MDA changes the
+message.
+
+This variable should never be set directly, but bound before a call to
+`mml-generate-mime' or similar functions.")
+
 (defun mm-insert-rfc822-headers (charset encoding)
   "Insert text/plain headers with CHARSET and ENCODING."
   (insert "MIME-Version: 1.0\n")
@@ -60,6 +72,14 @@ or base64 will be used, depending on what is more efficient.")
       "application/octet-stream"
     (mailcap-extension-to-mime (match-string 0 file))))
 
+(defun mm-safer-encoding (encoding)
+  "Return a safer but similar encoding."
+  (cond
+   ((memq encoding '(7bit 8bit quoted-printable)) 'quoted-printable)
+   ;; The remaing encodings are binary and base64 (and perhaps some
+   ;; non-standard ones), which are both turned into base64.
+   (t 'base64)))
+
 (defun mm-encode-content-transfer-encoding (encoding &optional type)
   (cond
    ((eq encoding 'quoted-printable)
@@ -75,8 +95,10 @@ or base64 will be used, depending on what is more efficient.")
        (message "Error while decoding: %s" error)
        nil)))
    ((memq encoding '(7bit 8bit binary))
+    ;; Do nothing.
     )
    ((null encoding)
+    ;; Do nothing.
     )
    ((functionp encoding)
     (ignore-errors (funcall encoding (point-min) (point-max))))
@@ -119,9 +141,13 @@ The encoding used is returned."
       (while rules
        (when (string-match (caar rules) type)
          (throw 'found
-                (if (eq (cadar rules) 'qp-or-base64)
-                    (mm-qp-or-base64)
-                  (cadar rules))))
+                (let ((encoding 
+                       (if (eq (cadar rules) 'qp-or-base64)
+                           (mm-qp-or-base64)
+                         (cadar rules))))
+                  (if mm-use-ultra-safe-encoding
+                      (mm-safer-encoding encoding)
+                    encoding))))
        (pop rules)))))
 
 (defun mm-qp-or-base64 ()