Axel Howind created PDFBOX-5575:
-----------------------------------
Summary: 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
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.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
