On 1/11/07, Jeff Muizelaar <[EMAIL PROTECTED]> wrote:
On Thu, Jan 11, 2007 at 08:45:48AM -0500, Kristian Høgsberg wrote:
...
> And the problem in this case is how to prevent looping when we have
> circular references in the page tree. To prevent this we can do two
> things: the one idea that Albert doesn't like is to just limit the
> depth of the page tree. We can either choose a fixed limit or use the
> total number of references as a limit. If there is a page tree chain
> longer than, say, 1000, the document is most certainly malicious. On
> the other hand, we can easily handle a recusion level of 1000, so we
> can detect it and bail out safely in that case.
>
> The other idea is to just put a 'visited' bit in each node of the page
> tree. If wee see a page that already has the 'visited' bit set we
> know something is wrong and we can bail out right away.
I looked at this idea first. However, I didn't see how it could fit
easily with the exisiting code structure. The solution I came with is to
have a bitmap of size XRef->size(), then for each object we visit mark
the bit corresponding to that object. If the bit is already set we know
that we have a loop in the tree.
But why not just limit the recursion depth to XRef->size() calls?
Kristian
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