keep track of max written in PacketPayload

libraries/networking/src/PacketPayload.cpp

@@ -31,9 +31,12 @@ qint64 PacketPayload::writeData(const char* data, qint64 maxSize) {
         // good to go - write the data
         memcpy(_data + currentPos, src, srcBytes);
 
-        // should this cause us to push our index (is this the farthest we've written in data)?
+        // seek to the new position based on where our write just finished
         seek(currentPos + srcBytes);
 
+        // keep track of _maxWritten so we can just write the actual data when packet is about to be sent
+        _maxWritten = std::max(pos() + 1, _maxWritten);
+
         // return the number of bytes written
         return srcBytes;
     } else {

libraries/networking/src/PacketPayload.h

@@ -30,6 +30,7 @@ protected:
 private:
     char* _data;
     qint64 _size = 0;
+    qint64 _maxWritten = 0;
 };
 
 #endif // hifi_PacketByteArray_h