Relaxed QP decoder

app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -32,7 +32,6 @@ import com.sun.mail.util.ASCIIUtility;
 import com.sun.mail.util.BASE64DecoderStream;
 import com.sun.mail.util.FolderClosedIOException;
 import com.sun.mail.util.MessageRemovedIOException;
-import com.sun.mail.util.QDecoderStream;
 
 import org.jsoup.nodes.Document;
 import org.jsoup.nodes.Element;
@@ -1315,8 +1314,8 @@ public class MessageHelper {
             if (p1.charset != null && p1.charset.equalsIgnoreCase(p2.charset) &&
                     p1.encoding != null && p1.encoding.equalsIgnoreCase(p2.encoding)) {
                 try {
-                    byte[] b1 = decodeWord(p1.text, p1.encoding);
-                    byte[] b2 = decodeWord(p2.text, p2.encoding);
+                    byte[] b1 = decodeWord(p1.text, p1.encoding, p1.charset);
+                    byte[] b2 = decodeWord(p2.text, p2.encoding, p2.charset);
                     byte[] b = new byte[b1.length + b2.length];
                     System.arraycopy(b1, 0, b, 0, b1.length);
                     System.arraycopy(b2, 0, b, b1.length, b2.length);
@@ -1340,16 +1339,18 @@ public class MessageHelper {
         return sb.toString();
     }
 
-    static byte[] decodeWord(String word, String encoding) throws IOException {
+    static byte[] decodeWord(String word, String encoding, String charset) throws IOException {
         ByteArrayInputStream bis = new ByteArrayInputStream(ASCIIUtility.getBytes(word));
 
         InputStream is;
         if (encoding.equalsIgnoreCase("B"))
             is = new BASE64DecoderStream(bis);
         else if (encoding.equalsIgnoreCase("Q"))
-            is = new QDecoderStream(bis);
-        else
-            throw new UnsupportedEncodingException("Encoding=" + encoding);
+            is = new QDecoderStreamEx(bis);
+        else {
+            Log.e(new UnsupportedEncodingException("Encoding=" + encoding));
+            return word.getBytes(charset);
+        }
 
         int count = bis.available();
         byte[] bytes = new byte[count];
@@ -1379,10 +1380,10 @@ public class MessageHelper {
                 return text;
 
             try {
-                return decodeMime(new String(decodeWord(text, encoding), charset));
+                return decodeMime(new String(decodeWord(text, encoding, charset), charset));
             } catch (Throwable ex) {
                 String word = "=?" + charset + "?" + encoding + "?" + text + "?=";
-                Log.w(new IllegalArgumentException(word, ex));
+                Log.e(new IllegalArgumentException(word, ex));
                 return word;
             }
         }

app/src/main/java/eu/faircode/email/QDecoderStreamEx.java

@@ -0,0 +1,54 @@
+package eu.faircode.email;
+
+/*
+ * Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
+ * Copyright 2018-2020 by Marcel Bokhorst (M66B)
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0, which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * This Source Code may also be made available under the following Secondary
+ * Licenses when the conditions for such availability set forth in the
+ * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
+ * version 2 with the GNU Classpath Exception, which is available at
+ * https://www.gnu.org/software/classpath/license.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+ */
+
+import com.sun.mail.util.ASCIIUtility;
+import com.sun.mail.util.QPDecoderStream;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+public class QDecoderStreamEx extends QPDecoderStream {
+    private Byte pushed = null;
+
+    public QDecoderStreamEx(InputStream in) {
+        super(in);
+    }
+
+    @Override
+    public int read() throws IOException {
+        int c = (pushed == null ? in.read() : pushed);
+        pushed = null;
+
+        if (c == '_')
+            return ' ';
+        else if (c == '=') {
+            ba[0] = (byte) in.read();
+            ba[1] = (byte) in.read();
+            try {
+                return ASCIIUtility.parseInt(ba, 0, 2, 16);
+            } catch (NumberFormatException ex) {
+                Log.w(ex);
+                pushed = ba[1];
+                return ba[0];
+            }
+        } else
+            return c;
+    }
+}
+