[xml] xmlReader: Possibility for cloning an xmlTextReader (or multi-pass reading)

["Martin B." <0xCDCDCDCD gmx at>]

{Re-sending this. Never got anywhere it seems.}

Hi!

I currently have to fix an existing application to use something other 
than the DOM interface of libxml2 because it turns out it gets passed 
XML files so large that they can't be loaded into memory.

I have rewritten the data loading from iterating over the DOM tree to 
using xmlTextReader for the most part now without too much problems.

It turns out however, that the subtree where the large data resides has 
to be read not in-order, but I have to collect some (small amount of) 
data before the other. (And the problem is exactly that it is this 
subtree that contains the large volume of data, so loading only this 
subtree into memory doesn't make much sense either.)

The easiest thing would be to just "clone" / "copy" my current reader, 
read ahead and then return to the original instance to continue reading 
there.

There doesn't appear to be any way however to "copy" the state of an 
xmlTextReader.

If I can't re-read part of a file, I could also re-read the whole file, 
which, although wasteful, would be OK here, but I still would need to 
remember where I was beforehand?

Is there maybe a simple way to remember for a xmlTextReader where it is 
in the current document, so that I can later find that position again 
when reading the document/file a second time?

cheers,
Martin