nx_zip.nx

nx_zip.nx -- ZIP archive writer + reader (STORED method): a COMPLETE pair. The tree could READ zips (nx_zip_read.nx) and could not write one. That is half a format: EPUB, OOXML, JAR and every download bundle are ZIP, and producing them was impossible. This closes it with a writer and an independent reader in one file, so it proves by exact round-trip. THE CRC IS THE REFLECTED ONE. ZIP uses CRC-32 with polynomial 0xEDB88320 (the reflected form of 0x04C11DB7), init and final-xor both 0xFFFFFFFF. This is a DIFFERENT algorithm from the one nx_ogg.nx uses, which is the same polynomial UNreflected with zero init. Two formats in this tree now use "CRC-32" and they are not interchangeable -- swapping them yields archives that every unzip rejects with a checksum error. T1 pins this one to the classic check value: CRC32("123456789") == 0xCBF43926. THE OFFSET IS WRITTEN TWICE. Each entry's metadata appears in BOTH the local header and the central directory, and the central directory also carries the local header's byte offset. Readers trust the CENTRAL DIRECTORY -- an archive whose local headers are fine but whose central offsets are wrong opens as empty or corrupt, and the local headers give no hint anything is off. STORED, NOT DEFLATED. Method 0 stores bytes verbatim. That is a fully valid ZIP that every tool opens; wiring nx_deflate_enc.nx in as method 8 is a compression improvement, not a correctness one. genealogy_id: pkware_appnote_zip lineage_id: nx_zip_v1 license_tier: ORIGINAL