fix(filters): handle sync-flush terminated zlib streams in FlateDecode #20
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pako.inflate() returns undefined (rather than throwing) for zlib streams terminated with a sync-flush marker (00 00 FF FF) instead of a proper final block. Some PDF generators like PDFium produce these streams. The undefined result propagated through FilterPipeline and caused a TypeError in downstream code trying to access .length on undefined chunks. FlateFilter.decode() now detects this case and recovers the decompressed data from pako's internal output buffer. Truly corrupt streams return empty rather than throwing, consistent with the library's lenient approach to malformed PDFs. Closes #16
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Summary
Fixes #16 —
TypeError: Cannot read properties of undefined (reading 'length')when extracting text from PDFs generated by PDFium.pako.inflate()silently returnsundefined(instead of throwing) for zlib streams terminated with a sync-flush marker (00 00 FF FF) instead of a proper final block and Adler-32 checksum. Some PDF generators (notably PDFium) produce these streams. Theundefinedpropagated throughFilterPipelineintoconcatenateChunks()which crashed on.length.FlateFilternow detects whenpako.inflate()returnsundefinedor throws, and falls back to recovering partial output from pako's internalInflatestate. Truly unrecoverable streams return emptyUint8Arrayrather than throwing, consistent with our lenient approach to malformed PDFs.