Specification conform xref/trailer parsing + Fix
------------------------------------------------
Key: PDFBOX-1016
URL: https://issues.apache.org/jira/browse/PDFBOX-1016
Project: PDFBox
Issue Type: Bug
Components: Parsing
Affects Versions: 1.6.0
Reporter: Timo Boehme
PDFBOX currently reads xref table/trailer and XRef objects without using
startxref or 'Prev' information which results in applying not active data
resulting in using wrong objects or resulting in parsing exceptions because old
trailer settings do not apply anymore. This happens especially with updated PDF
documents where changes are simply appended and old objects/xref entries
remain but are not referenced. My last patch (PDFBOX-1014) tried to solve this
for a specific case but it was based on assumptions which do not hold in every
case.
The specification compliant way is to read the last startxref which points to
the last xref object which itself may reference further xref objects using
'Prev' attribute.
I have written a fix which works the standard way and can fall back to the old
behavior in case startxref is wrong or missing. The fix tries to be as
unobtrusive as possible. A new class (o.a.p.pdfparser.XrefTrailerResolver) is
filled with all xref table/trailer and XRef object data. After document is
parsed (and last startxref is read) this class creates xref table and trailer
using startxref and 'Prev' information. Beside this new class there are small
changes to PDFParser and COSDocument.
This bugfix/improvement should bring PDFBOX a good step closer to be PDF
specification conform - especially as long as the new specification conform
parser project is not finished.
This bugfix supersedes the fix from PDFBOX-1014.
--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira
