Improved BASE64 to update has_error when decoding.

Added manual tests.

library/text/encoder/tests/test_base64.e

@@ -34,6 +34,38 @@ feature -- Test routines
 			assert ("decoded encoded string is same", u ~ s)
 		end
 
+feature -- Tests
+
+	test_valid_64_encoding
+		do
+			assert ("Expected encoded True:", is_valid_base64_encoding ((create {BASE64}).encoded_string ("content")))
+		end
+
+	test_not_valid64_encoding
+		do
+			assert ("Expected encoded False:", not is_valid_base64_encoding ("content"))
+			assert ("Expected encoded False:", not is_valid_base64_encoding ("!@#$%%^"))
+		end
+
+feature {NONE} -- Implementation
+
+	is_valid_base64_encoding (a_string: STRING): BOOLEAN
+			-- is `a_string' base64 encoded?
+		local
+			l_encoder: BASE64
+			l_string: STRING
+			l_retry: BOOLEAN
+		do
+			if not l_retry then
+				create l_encoder
+				l_string := l_encoder.decoded_string (a_string)
+				Result := not l_encoder.has_error
+			end
+		rescue
+			l_retry := True
+			retry
+		end		
+
 note
 	copyright: "Copyright (c) 1984-2011, Eiffel Software and others"
 	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"