@Override
    public void read(FieldBase field, ReferenceFieldValue value) {
        final boolean documentIdPresent = (buf.get() != 0);
        if (documentIdPresent) {
            value.assign(readDocumentId());
        } else {
            value.clear();
        }
    }
Class used for de-serializing documents on the Vespa 6.x document format.

@author baldersheim
document/src/main/java/com/yahoo/document/serialization/VespaDocumentDeserializer6.java