urn-rs

A small, allocation-conscious Rust crate for RFC 8141 / RFC 2141 URNs — parse, build, compare, percent-encode.

use urn_rs::{Urn, UrnBuilder};

let u: Urn = "urn:example:weather/zurich?+ttl=60#frag".parse()?;
assert_eq!(u.nid(), "example");
assert_eq!(u.nss(), "weather/zurich");

let built = UrnBuilder::new("isbn", "0451450523").build()?;
assert_eq!(built.as_str(), "urn:isbn:0451450523");

Why this fork

Fork of urn by chayleaf. RFC behavior unchanged; this fork adds:

• SWAR fast path and hex lookup tables for percent decode/encode.
• Fewer allocations in builder, accessors, setters, serde.
• Ord / PartialOrd on Urn and UrnSlice.
• Criterion bench suite under benches/.
• Rust 2024 edition, MSRV 1.85.
• Renamed to urn-rs.

Credit and history preserved — see Attribution.

Install

cargo add urn-rs

Feature flags

For no_std, disable default features. You get UrnSlice<'a> (borrowed, zero-alloc). Add alloc back for Urn and the builder.

Equivalence

By default, equality compares only the significant portion of the URN:

• NID is ASCII-case-insensitive.
• NSS percent-encoding is normalized before comparison.
• r-/q-/f-components are ignored.
• Per-namespace lexical-equivalence rules from individual RFCs are not applied.

Enable exact-eq when distinct r/q/f components must produce distinct map keys — equality then covers the whole normalized URN.

Benchmarks

cargo bench
cargo bench --bench parse
cargo bench --features serde --bench serde

Criterion output: target/criterion/.

MSRV

Rust 1.85 (edition 2024).

Attribution

Original crate: urn by chayleaf. Upstream commits are preserved in this repo's history under their original authorship. This fork is a thin layer of performance and ergonomics work on top of their design.

License

Triple-licensed, same as upstream. Pick whichever fits:

• 0BSD
• Apache-2.0
• MIT