μCOBS

The COBS implementation for Rust.

Consistent Overhead Byte Stuffing (COBS) encodes arbitrary bytes so that 0x00 never appears in the output, allowing 0x00 to serve as an unambiguous frame delimiter. Overhead is exactly 1 byte per 254 input bytes (worst case).

Features

• no_std, zero-alloc — runs anywhere, from 8-bit MCUs to servers
• ~140 lines of implementation — small, auditable, easy to verify
• 100% spec-compliant — Cheshire & Baker, IEEE/ACM Transactions on Networking, 1999
• Proven interoperability — cross-validated against corncobs, cobs, and Python cobs
• Insanely tested — canonical vectors, property-based tests, fuzz targets, cross-crate interop, randomized payloads, and more coming

Usage

// Encode
let mut buf = [0u8; 16];
let n = ucobs::encode(&[0x11, 0x00, 0x33], &mut buf).unwrap();
assert_eq!(&buf[..n], &[0x02, 0x11, 0x02, 0x33]);

// Decode
let mut out = [0u8; 16];
let n = ucobs::decode(&[0x02, 0x11, 0x02, 0x33], &mut out).unwrap();
assert_eq!(&out[..n], &[0x11, 0x00, 0x33]);

// Buffer sizing
let max = ucobs::max_encoded_len(256); // 258

API

Function	Signature	Description
encode	(src: &[u8], dest: &mut [u8]) -> Option<usize>	COBS-encode src into dest. Returns byte count or None if buffer too small.
decode	(src: &[u8], dest: &mut [u8]) -> Option<usize>	Decode COBS data. Returns byte count or None if input is malformed.
max_encoded_len	const fn(src_len: usize) -> usize	Maximum encoded size for a given input length.

Note: The encoder does not append a trailing 0x00 sentinel. Append it yourself when framing for transport.

Testing

# Unit + property + interop tests
cargo test

# Fuzz testing (requires nightly + cargo-fuzz)
cd fuzz
cargo +nightly fuzz run fuzz_decode -- -max_total_time=60
cargo +nightly fuzz run fuzz_roundtrip -- -max_total_time=60

License

MIT — Stephen Waits