Linked list in repeating group encoder/decoder

[vad0]

I am new to artio, but i see a strange pattern: repeating groups have a bunch of encoders/decoders linked with each other. Why is it implemented this way? Would it be more efficient to use an array based structure? This is how it looks now:

public MDEntriesGroupEncoder next()
    {
        if (next == null)
        {
            next = new MDEntriesGroupEncoder();
        }
        return next;
    }