nordisk/znippy

znippy-common — crate card

Reverse-engineered (from source — verify, don't trust the name)

• One-line pitch: The shared core of the znippy workspace — plugin trait, Arrow-IPC index/manifest schema, codec, decompress engine, and the native package handlers all live here.
• Does: Defines the ZnippyPlugin/ArchiveTypePlugin trait and metadata model (plugin.rs), the on-disk .znippy index/manifest/footer schema and reader/writer (index.rs, archive.rs), the ArchiveMetaSink abstraction with its default ArrowIpcSink (meta_sink.rs, meta_sink_append.rs), the OpenZL/zstd codec (codec.rs), the decompress path (decompress.rs), the slot-pool CUT POLICY (poolplan.rs — the pool itself is upstream, znippy_zoomies::chunk_revolver), typed query views over sub-indexes (views.rs), and the native handlers under plugins/ (cargo, npm, gem, conda, rpm, deb, wasm_loader, skeletons). Optional sign feature adds detached CMS provenance signatures.
• Key deps: arrow/arrow-array/arrow-select 58 (index schema, re-exported so plugins compile against the exact version), openzl-sys-rs (codec), blake3 (checksums), crossbeam-channel, fst; optional host-decompressors pull sibling zoomies crates ljar/lgz/lbzip2 plus lzma-rs/ruzstd/tar; optional wasmtime for WASM plugins; RustCrypto stack behind sign.
• Shape: lib, ~9.4k LOC, largest modules views.rs (1462), sign.rs (1200), index.rs (1061), meta_sink_append.rs (860), plus a plugins/ subtree of native handlers.
• Observed role in the workspace: Foundation crate — depended on by znippy-compress, znippy-decompress, all plugins, znippy-iceberg, and the CLI. It re-exports arrow and owns the format contract everyone else implements against.

Fill in (one line each — only the human knows these)

• Primary consumer(s):
• Why it exists (vs the obvious alternative):
• Hard constraint (airgap / no-C-deps / no-FFI / pure-Rust / etc.):
• Release cadence & independence (rides a parent? own repo someday?):
• Status (production / prototype / experimental / stubbed):
• Must-NOT-change invariant:
• Biggest known gap or TODO:
• Anything a newcomer would get wrong about it: