Subject: 28.0.50; uudecode-decode-region-internal is broken
From: Kazuhiro Ito <[email-masked]>
To: [email-masked]
Date: Tue, 03 Nov 2020 17:27:41 +0900
List-Id: <debbugs-submit.debbugs.gnu.org>

When I call uudecode-decode-region-internal in multibyte buffer, it
fails to decode eight-bit characters.

The function makes string from uuencoded text by passing unsigned char
vlue (0-255) to char-to-string function, which makes multibyte-string.
After that, string is decoded as binary.  But eight-bit characters are
never made in that way.

(let ((ch #xc8))
  (decode-coding-string (char-to-string ch) 'binary))

-> "8"

Additionally, concat and char-to-string functions are called so
frequently that deocder is very slow for large data.

Please see the below patch.

diff --git a/lisp/mail/uudecode.el b/lisp/mail/uudecode.el
index bcbd571b53..f9254aee75 100644
--- a/lisp/mail/uudecode.el
+++ b/lisp/mail/uudecode.el
@@ -149,12 +149,10 @@ uudecode-decode-region-internal
 	      (setq counter (1+ counter)
 		    inputpos (1+ inputpos))
 	      (cond ((= counter 4)
-		     (setq result (cons
-				   (concat
-				    (char-to-string (ash bits -16))
-				    (char-to-string (logand (ash bits -8) 255))
-				    (char-to-string (logand bits 255)))
-				   result))
+		     (setq result (cons (logand bits 255)
+					(cons (logand (ash bits -8) 255)
+					      (cons (ash bits -16)
+						    result))))
 		     (setq bits 0 counter 0))
 		    (t (setq bits (ash bits 6)))))))
 	  (cond
@@ -166,26 +164,21 @@ uudecode-decode-region-internal
 	    ;;(error "uucode ends unexpectedly")
 	    (setq done t))
 	   ((= counter 3)
-	    (setq result (cons
-			  (concat
-			   (char-to-string (logand (ash bits -16) 255))
-			   (char-to-string (logand (ash bits -8) 255)))
-			  result)))
+	    (setq result (cons (logand (ash bits -8) 255)
+			       (cons (logand (ash bits -16) 255)
+				     result))))
 	   ((= counter 2)
-	    (setq result (cons
-			  (char-to-string (logand (ash bits -10) 255))
-			  result))))
+	    (setq result (cons (logand (ash bits -10) 255)
+			       result))))
 	  (skip-chars-forward non-data-chars end))
+	(setq result (apply #'unibyte-string (nreverse result)))
 	(if file-name
             (with-temp-file file-name
               (set-buffer-multibyte nil)
-              (insert (apply #'concat (nreverse result))))
+              (insert result))
 	  (or (markerp end) (setq end (set-marker (make-marker) end)))
 	  (goto-char start)
-	  (if enable-multibyte-characters
-	      (dolist (x (nreverse result))
-                (insert (decode-coding-string x 'binary)))
-	    (insert (apply #'concat (nreverse result))))
+          (insert result)
 	  (delete-region (point) end))))))
 
 ;;;###autoload

-- 
Kazuhiro Ito