figure out fallbacks with omemo source id

1 files changed, 12 insertions, 0 deletions

diff --git a/src/main/java/de/pixart/messenger/crypto/axolotl/XmppAxolotlMessage.java b/src/main/java/de/pixart/messenger/crypto/axolotl/XmppAxolotlMessage.java
index 603eedde8..f5a41e6b3 100644
--- a/src/main/java/de/pixart/messenger/crypto/axolotl/XmppAxolotlMessage.java
+++ b/src/main/java/de/pixart/messenger/crypto/axolotl/XmppAxolotlMessage.java
@@ -88,6 +88,18 @@ public class XmppAxolotlMessage {
         }
     }
 
+    public static int parseSourceId(final Element axolotlMessage) throws IllegalArgumentException {
+        final Element header = axolotlMessage.findChild(HEADER);
+        if (header == null) {
+            throw new IllegalArgumentException("No header found");
+        }
+        try {
+            return Integer.parseInt(header.getAttribute(SOURCEID));
+        } catch (NumberFormatException e) {
+            throw new IllegalArgumentException("invalid source id");
+        }
+    }
+
     private XmppAxolotlMessage(final Element axolotlMessage, final Jid from) throws IllegalArgumentException {
         this.from = from;
         Element header = axolotlMessage.findChild(HEADER);