Overview of the inverted index

Hi,
I've been using htdig for a while, and I'll like to get an overview of the internals of htdig.
Especially the inverted index in mifluz.
I can't figure out how the inverted index is stored.

Is it like:
InvertedIndex:
WordId    DocId    flags   ..
  1             8          2

And the wordList
WordId     Word
   1             foo
   2             apple

Or does it uses another method?

/Lalle