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https://issues.apache.org/jira/browse/PDFBOX-1000?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13177994#comment-13177994
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Maruan Sahyoun commented on PDFBOX-1000:
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I'm looking for a suggestion when dealing with different kinds of PDFs. The
idea behind the ConformingParser (if I understood it correctly) was to parse
files which are inline with the PDF spec. But even Acrobat is relaxed when it
comes to certain deviations from the spec e.g. startxref is expected to be
within the last 1024 bytes. In the real world there might also be PDFs which
can not be read by Acrobat.
They way I think I could deal with it is to introduce (gradually) three parsing
modes within the ConformingParser: Strict, Acrobat, Relaxed.
Strict will fail the parsing as soon as a deviation from the spec is
encountered.
Acrobat will take the Acrobat implementation notes as outlined in the spec into
account.
Relaxed will try to continue processing if there are issues.
WDYT
> Conforming parser
> -----------------
>
> Key: PDFBOX-1000
> URL: https://issues.apache.org/jira/browse/PDFBOX-1000
> Project: PDFBox
> Issue Type: New Feature
> Components: Parsing
> Reporter: Adam Nichols
> Assignee: Adam Nichols
> Attachments: COSUnread.java, ConformingPDDocument.java,
> ConformingPDFParser.java, ConformingPDFParserTest.java, XrefEntry.java,
> conforming-parser.patch, gdb-refcard.pdf
>
>
> A conforming parser will start at the end of the file and read backward until
> it has read the EOF marker, the xref location, and trailer[1]. Once this is
> read, it will read in the xref table so it can locate other objects and
> revisions. This also allows skipping objects which have been rendered
> obsolete (per the xref table)[2]. It also allows the minimum amount of
> information to be read when the file is loaded, and then subsequent
> information will be loaded if and when it is requested. This is all laid out
> in the official PDF specification, ISO 32000-1:2008.
> Existing code will be re-used where possible, but this will require new
> classes in order to accommodate the lazy reading which is a very different
> paradigm from the existing parser. Using separate classes will also
> eliminate the possibility of regression bugs from making their way into the
> PDDocument or BaseParser classes. Changes to existing classes will be kept
> to a minimum in order to prevent regression bugs.
> [1] Section 7.5.5 "Conforming readers should read a PDF file from its end"
> [2] Section 7.5.4 "the entire file need not be read to locate any particular
> object"
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