Re: application/octet-stream sent as 7bit

[Katsumi Yamaoka <yamaoka@jpl.org>]

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>>>>> Dmitri Paduchikh wrote:
[...]
>> Agreed.  Aren't there any other application/* types that should
>> not be forced to be encoded by 7bit?  Otherwise, is it better not
>> to force the 7bit encoding to all application/* types?

> Hmm... It is unclear to me whether other application/* (or audio/*,
> image/*, video/*) require protection from this behavior. Although binary
> data most likely isn't 7-bit, it may be 7-bit in principle. IMO, in such
> case it would be preferable to provide safe default behavior and means
> to change it if user wants to. 7bit enforcement breaks both of these
> principles (safe default and user control) thus I would rather remove it
> completely as in the patch below. Are there any situations when it is
> desirable to enforce 7bit?

>> Here are two patches; one is for excluding application/octet-stream,
>> the other is for excluding application/*.

> Thank you. The following patch is a variation of your patches.
[...]

I like it.  I think removing the 7bit enforcement makes it simple,
necessary and sufficient.  Even so, it can be controlled by
customizing `mm-content-transfer-encoding-defaults' if necessary
(though I don't think so).

I'd like to make one more change, which enables a user to change
the encoding by adding the `encoding=' component to a MIME tag
manually like this:

< #part type="application/octet-stream" disposition=inline encoding=7bit>

It will be useful for testing with various encodings.  The patch:


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--- mm-encode.el~	2009-01-22 08:09:02 +0000
+++ mm-encode.el	2009-09-04 00:28:48 +0000
@@ -137,22 +137,19 @@
    (t
     (error "Unknown encoding %s" encoding))))
 
-(defun mm-encode-buffer (type)
-  "Encode the buffer which contains data of MIME type TYPE.
+(defun mm-encode-buffer (type &optional encoding)
+  "Encode the buffer which contains data of MIME type TYPE by ENCODING.
 TYPE is a string or a list of the components.
+The optional ENCODING overrides the encoding determined according to
+TYPE and `mm-content-transfer-encoding-defaults'.
 The encoding used is returned."
-  (let* ((mime-type (if (stringp type) type (car type)))
-	 (encoding
-	  (or (and (listp type)
-		   (cadr (assq 'encoding type)))
-	      (mm-content-transfer-encoding mime-type)))
-	 (bits (mm-body-7-or-8)))
-    ;; We force buffers that are 7bit to be unencoded, no matter
-    ;; what the preferred encoding is.
-    ;; Only if the buffers don't contain lone lines.
-    (when (and (eq bits '7bit) (not (mm-long-lines-p 76)))
-      (setq encoding bits))
-    (mm-encode-content-transfer-encoding encoding mime-type)
+  (let ((mime-type (if (stringp type) type (car type))))
+    (mm-encode-content-transfer-encoding
+     (or encoding
+	 (setq encoding (or (and (listp type)
+				 (cadr (assq 'encoding type)))
+			    (mm-content-transfer-encoding mime-type))))
+     mime-type)
     encoding))
 
 (defun mm-insert-headers (type encoding &optional file)
--- mml.el~	2009-08-31 00:08:11 +0000
+++ mml.el	2009-09-04 00:28:48 +0000
@@ -585,7 +585,9 @@
 			(unless raw
 			  (setq charset	(mm-encode-body charset))))
 		    (insert contents)))))
-	      (setq encoding (mm-encode-buffer type)
+	      (if (setq encoding (cdr (assq 'encoding cont)))
+		  (setq encoding (intern (downcase encoding))))
+	      (setq encoding (mm-encode-buffer type encoding)
 		    coded (mm-string-as-multibyte (buffer-string))))
 	    (mml-insert-mime-headers cont type charset encoding nil)
 	    (insert "\n" coded))))