ROB: Flate decoding for streams with faulty tail bytes #3332
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Some FLATE encoded streams of early Adobe Distiller / Pitstop versions are written with additionally added CR bytes to the PDF and calculate the faulty tail bytes into Length value of stream dict. Later then decoding fails. Solved with removing step by step tail bytes until decoding is successful.
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faulty_stream_tail_example 1.pdf I added one sample file and will create a test from it later. I got another sample PDF but it is too large to add it here ... |
Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## main #3332 +/- ##
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Coverage 96.73% 96.73%
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Files 53 53
Lines 9054 9060 +6
Branches 1675 1676 +1
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+ Hits 8758 8764 +6
Misses 177 177
Partials 119 119 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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stefan6419846
changed the title
First paste of new code was wrong, so I corrected it and moved it from the "try" block into the "except" block because it is a fall back in case of an error and not a general new approach for decoding
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Sorry for the 2nd commit, did a mistake during code copy. Now it fits. |
stefan6419846
added
the
needs-test
simplified code + created test
…ertelgmg/pypdf into patch-FLATEperformance
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I am done with the suggestion to simplify code as requested above. |
Co-authored-by: Stefan <96178532+stefan6419846@users.noreply.github.com>
To make the asset download more robust the test PDF and the expected data have been move to test function body with the pitfall of needing a higher timeout now, what makes this test less precise for the performance check.
Co-authored-by: Stefan <96178532+stefan6419846@users.noreply.github.com>
Co-authored-by: Stefan <96178532+stefan6419846@users.noreply.github.com>
stefan6419846
approved these changes
Jun 27, 2025
stefan6419846
removed
the
needs-test
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Thanks for your support Stefan - was not easy for me because the lack of experience with your project and the tough style rules. |
stefan6419846
added a commit
that referenced
this pull request
Jun 29, 2025
## What's new ### Performance Improvements (PI) - Performance optimization for LZW decoding (#3329) by @henningkoertelgmg ### Robustness (ROB) - Flate decoding for streams with faulty tail bytes (#3332) by @henningkoertelgmg - dc_creator could be a Bag as well (#3333) by @stefan6419846 - Handle tree being NullObject when retrieving named destinations (#3331) by @stefan6419846 ### Maintenance (MAINT) - Move inline-image mappings to constants (#3328) by @stefan6419846 [Full Changelog](5.6.1...5.7.0)
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Some FLATE encoded streams of early Adobe Distiller / Pitstop versions are written with additionally added CR bytes to the PDF and calculate the faulty tail bytes into Length value of stream dict. Later then decoding fails. Solved with removing step by step tail bytes until decoding is successful.