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From "christopher.begley@outlook.com"<christopher.beg...@outlook.com>
Subject Re: cosDocument.getXrefTable() returns negative offsets
Date Tue, 01 Nov 2016 14:58:16 GMT

On 2016-10-31 12:44 (-0400), Andreas Lehmkuehler <andreas@lehmi.de> wrote: 
> Am 31.10.2016 um 16:10 schrieb christopher.begley@outlook.com:
> >
> >>> OBJ_NUMBER , OFFSET
> >>> 49,12769
> >>> 50,25217
> >>> 51,25502
> >>> 52,26034
> >>> 53,116
> >>> 54,-36
> >>> 55,-36
> >>> 56,-36
> >
> >> A negative offset indicates that the given object is part of a compressed object
> >> stream. In your case that stream is object 36 0.
> >>
> >>> Thanks in advance for your time.
> >>
> >> BR
> >> Andreas
> >
> > Thanks Andreas. Where can I find more documentation on compressed objects with respect
to negative offsets?
> PDF spec, chapter "7.5.7 Object Streams"
> 
> BR
> Andreas
> 
> Thanks. I read that section. I also read about cross-reference streams. Nowhere in the
entire PDF Spec does it mention negative offsets. I'm relatively new to pdf parsing and where
I'm stumped is I don't know exactly how to handle these negative offsets.  

> >>> OBJ_NUMBER , OFFSET
> >>> 49,12769
> >>> 50,25217
> >>> 51,25502
> >>> 52,26034
> >>> 53,116
> >>> 54,-36
> >>> 55,-36
> >>> 56,-36

Let's take Object Number 54 for example. In your answer you stated that this would be Object
[36,0] and that it is compressed. How did you know it's object 36,0? Where did  you find this
information?How - using the PDFBox API, would I retrieve this object and decode it? I wish
I could find documentation (somewhere) on how to handle this scenario - maybe I'm missing
something or not searching for the right keywords.

I appreciate your patience in helping me out. I'm more than willing to read/research anything
necessary, but I just got through reading 3 sections of the PDF Reference and while it discussed
at length the structure of objects, object streams, cross reference streams , it did not help
me in dealing with how to handle/ locate / parse objects with a negative offset.
> 
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