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https://issues.apache.org/jira/browse/PDFBOX-5575?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17702340#comment-17702340
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ASF subversion and git services commented on PDFBOX-5575:
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Commit 1908526 from Tilman Hausherr in branch 'pdfbox/branches/2.0'
[ https://svn.apache.org/r1908526 ]
PDFBOX-5575: optimize LZWFilter, by Axel Howind; fix javadoc
> optimize LZWFilter
> ------------------
>
> Key: PDFBOX-5575
> URL: https://issues.apache.org/jira/browse/PDFBOX-5575
> Project: PDFBox
> Issue Type: Improvement
> Affects Versions: 3.0.0 PDFBox
> Reporter: Axel Howind
> Priority: Minor
> Attachments: optimize_LZWFilter.patch
>
>
> I ran the PDFBox tests with a profiler and saw that LZWFilter used quite a
> bunch of time, so I thought I might look at the code. I just looked at it
> totally out of context and tried to understand what is done there and what
> could be changed without altering results.
> * made the private mehtods static
> * changed the variable/method parameter 'earlyChange' from integer to
> boolean because I thought tha would be more readable
> * some minor tweaks
> * it looks like codeTable is initialized quite often and everytime, 256
> length 1 byte arrays are created, so I pre-allocate those byte arrays so that
> they can be shared by all code tables. [~tilman] I assumed the contents of
> the codeTable entries will not be changed, and my analysis of the code seems
> to prove that (also the passing unit tests). Just please have a look at this
> so I don't break anything.
> * it took me some time to fully understand what findPatternCode() does and
> why it checks the codeTable in reverse order. I more or less recreated that
> method from scratch and I think it should now always be faster: for patterns
> of length 1 no iteration is done, and for longer patterns iteration stops
> once the correct entry is found. As this is the most notable change, please
> take a closer look. Unit tests pass.
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