PoC for sponsored fees

src/libxrpl/protocol/STTx.cpp

@@ -233,6 +233,25 @@ STTx::getSeqValue() const
     return getSeqProxy().value();
 }
 
+AccountID
+STTx::getFeePayer() const
+{
+    if (isFieldPresent(sfSponsor))
+    {
+        if (getFieldObject(sfSponsor)[sfFlags] & tfSponsorFee)
+        {
+            return getFieldObject(sfSponsor)[sfAccount];
+        }
+    }
+
+    if (isFieldPresent(sfDelegate))
+    {
+        return getAccountID(sfDelegate);
+    }
+
+    return getAccountID(sfAccount);
+}
+
 void
 STTx::sign(PublicKey const& publicKey, SecretKey const& secretKey)
 {