getRangeSize / getRangeCount to get number of bytes or record count

[nemanja-boric-sociomantic]

Sometimes when implementing features of a DLS reader we want to know exactly how much data we're dealing with for a certain range. It guides us in how we end up implementing our algorithms, whether we can keep some X range of data in memory, etc.

The current workaround is that we do these tests manually with getRange. But that of course causes a lot of network traffic for data which is ultimately just discarded.

Ideally it would be supported for for getRange and its filter/regex equivalents.

[gavin-norman-sociomantic]

A good way to do this would be as an option for GetRange. Similar to the DHT GetAll keys only option.