fix: accept EOCD central-directory offsets above 16MB in zip - #180
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ZIP based formats could fail validation for otherwise valid files when the EOCD "start of central directory offset" exceeded 0x00FFFFFF (~16MB). The previous EOCD tail check in Zip.EndsWith hardcoded 0x00 at byte 19 (MSB of the 4byte offset field), causing false negatives for large files. Update the EOCD end pattern to treat the full offset bytes as variable (wildcards) instead of forcing a fixed MSB. Impact: - Fixes false negatives for large ZIP containers and ZIP-based formats such as XLSX, DOCX, PPTX, ODS, ODT, and ODP. Tests: - Add regression test for ZIP with EOCD central directory offset > 16MB. - Add regression test for XLSX with EOCD central directory offset > 16MB. issues #178
kryptobi
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TeQ2102
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Jul 31, 2026
maxbreuker
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@kryptobi Verified manually against this branch with two real files whose EOCD central-directory offset is above 16 MiB:
Both are detected correctly now. Console output below 👍 
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ZIP based formats could fail validation for otherwise valid files when the EOCD "start of central directory offset" exceeded 0x00FFFFFF (~16MB). The previous EOCD tail check in Zip.EndsWith hardcoded 0x00 at byte 19 (MSB of the 4byte offset field), causing false negatives for large files.
Update the EOCD end pattern to treat the full offset bytes as variable (wildcards) instead of forcing a fixed MSB.
Impact:
Tests:
issues #178