nordisk/znippy-zoomies

lgz — guide

Class: guide · Function: lgz. Build, run, tune. The shape is in lgz-design.md; the why in lgz-reasoning.md.

Build

CARGO_TARGET_DIR=/mnt/work4t/cargo-target/zoomies cargo build --release -p lgz

Binary lands at target/release/lgz.

Run

lgz input.gz            # → stdout (streaming, ordered)
lgz input.gz -o out     # → file (positional pwrite fast path when multi-member)
lgz < input.gz > out    # stdin (streaming only; no random-access fast path)

Any file gzip/pigz wrote decodes — lgz reads the stock format. A concatenated / --independent / member-per-file .tar.gz takes the fully-parallel member path; a pigz full-flush stream splits at flush points; a plain gzip foo.gz falls back to a correct single-threaded decode (gzip's format has no interior split point — see reasoning).

Tune

• LGZ_THREADS=N pins the worker count (mirrors LBZIP2_THREADS). LGZ_THREADS=1 forces the single-worker _st bench row; unset ⇒ physical core count (lgz/src/bin/lgz.rs:100, physical_cores).
• Watch htop: on a multi-member -o run cores should sit near-flat; a plain single-member .gz will show one busy core (format-forced, not a bug).

Library

// in-memory decode (parallel when large + flush points, else flate2):
let out = lgz::decompress_gz(&bytes)?;                       // lgz/src/parallel.rs:108
// bomb-safe capped decode (streaming, single-thread by design):
let out = lgz::decompress_gz_capped(&bytes, 64 << 20)?;      // OUTPUT_TOO_LARGE on overflow
// tar.gz member filter:
let members = lgz::decompress_tar_gz_filter(&bytes, "config")?;  // Vec<(name, bytes)>

Bench

Driven by nornir through the shared harness — see decompressors-guide.md. HEAVY only (no smoke): nornir bench run znippy-zoomies, then nornir docs book znippy-zoomies to fill the A/B/C mashup.