decmpfs

decmpfs

Apply the operating system's transparent per-file filesystem compression to a file — smaller on disk, byte-identical on read, decompressed by the kernel at near-native speed. macOS APFS (decmpfs/LZVN), Linux btrfs (zstd→lzo→zlib), Windows NTFS (LZNT1).

The core does the bytes-to-compressed-file write in one pass — it never writes a file then reads it back to recompress.

use decmpfs::{compress_bytes, compress_file, Gate};

// Write `content` straight to an OS-compressed file (single pass).
let outcome = compress_bytes(path, &content, &Gate::any())?;

// Or compress a file that already exists, in place.
let outcome = compress_file(path)?;

Outcome, never a surprise error

Every call returns an Outcome — Compressed, NoGain (incompressible / sub-cluster), AlreadyCompressed, Unsupported (the FS has no per-file compression — ext4, xfs, ZFS, ReFS, FAT, tmpfs, network mounts), or Skipped (permission, lock, gate). An unsupported filesystem or a permission issue is a non-fatal Outcome, not an Err; Err is reserved for genuine I/O failures.

Gate

Gate decides which files to compress by glob and/or size:

let gate = Gate::new(Some("**/*.node"), Some(">= 1MB"))?;

Codecs (speed over ratio — a file is written once, read on load)

• macOS: LZVN (the fastest decmpfs codec to decompress).
• Linux btrfs: zstd, falling back to lzo then zlib on older kernels.
• Windows NTFS: LZNT1 (survives a reinstall's open-for-write, unlike WOF).

Features

The core is dependency-light (libc / windows-sys only). The optional addon feature pulls zstd + sha2 to unwrap a napi --compress hybrid .node back to the raw addon before compressing.

Node

An N-API binding (writeDecmpfsFile / writeDecmpfsFileSync, fs.writeFile-shaped, atomic by default) lives in node/.

License

MIT