Getting PDF document outline

Question

I'm using Quartz 2D to render PDF on the iPad, this works fine.

Now I need a way to get the document outline (table of content), I found the following function CGPDFDocumentGetCatalog which seems to be relevant, but the returned info is an opaque dictionary from which I don't know the keys.

I want the outline in a tree with the page number for each entry.

I'm interested in any answer I can use on the iPad, even if it use an other library.