private void reset(int op) {
done();
_buffer.reset();
set(_buffer);
_id = ID.getAndIncrement();
writeInt(0); // length: will set this later
writeInt(_id);
writeInt(0); // response to
writeInt(op);
}
void append(String db, WriteConcern c) {
_id = ID.getAndIncrement();
int loc = size();
writeInt(0); // will set this later
writeInt(_id);
writeInt(0); // response to
writeInt(2004);
_appendQuery(0, db + ".$cmd", 0, -1, c.getCommand(), null);
_buf.writeInt(loc, size() - loc);
}