nearest

Self-relative pointers and region-based allocation for Rust.

Store entire data graphs in a single contiguous byte buffer where all internal pointers are 4-byte i32 offsets relative to their own address — cloning a region is a plain memcpy with no fixup.

Example

use nearest::{Flat, NearList, Region, empty};

#[derive(Flat, Debug)]
struct Block {
  id: u32,
  items: NearList<u32>,
}

// Build
let mut region = Region::new(Block::make(1, [10u32, 20, 30]));
assert_eq!(region.items.len(), 3);

// Read (Region<T>: Deref<Target = T>)
assert_eq!(region.id, 1);
assert_eq!(region.items[0], 10);

// Mutate via branded session
region.session(|s| {
  let items = s.nav(s.root(), |b| &b.items);
  s.splice_list(items, [40u32, 50]);
});
assert_eq!(region.items.len(), 2);

// Clone is memcpy
let cloned = region.clone();
assert_eq!(cloned.items[0], 40);

Highlights

Zero-cost clone — Region::clone is a memcpy; self-relative offsets need no fixup
Compile-time safety — ghost-cell branded sessions prevent Ref escape or cross-session use
Declarative construction — #[derive(Flat)] generates make() builders for tree-shaped data
Compaction — Region::trim reclaims dead bytes left by append-only mutations
Miri-validated — all unsafe code tested under Miri with permissive provenance

Getting started

Requires nightly Rust due to #![feature(offset_of_enum)].

[dependencies]
nearest = "0.1"

See the API documentation for comprehensive guides and examples.

Minimum Supported Rust Version

Nightly Rust (rust-version = "1.93.0"), pinned to nightly-2026-02-10.

License

Licensed under either of

Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.