array-plus-extra

An array type that holds N+EXTRA elements using const generic parameters, providing safe slice access to contiguous memory.

This allows the creation of arrays that would require more powerful const-generics, e.g. [T; N+3].

Features

Specify both base size (N) and extra elements (EXTRA) at compile time
Deref to &{mut} [T] provides safe access to all N+EXTRA elements
as_slice() and as_mut_slice() work in const contexts
No runtime overhead compared to raw arrays
Works in embedded and bare-metal environments
All unsafe code verified with Miri for undefined behavior
Optional serde support for serialization/deserialization

Examples

Basic usage

use array_plus_extra::ArrayPlusExtra;

// Create an array with 5 base elements + 3 extra = 8 total elements.
let arr: ArrayPlusExtra<i32, 5, 3> = ArrayPlusExtra::new(42);

// Access via deref to slice.
assert_eq!(arr.len(), 8);
assert_eq!(arr[0], 42);
assert_eq!(arr[7], 42);

// Use slice methods.
let sum: i32 = arr.iter().sum();
assert_eq!(sum, 336); // 42 * 8

Mutable access

use array_plus_extra::ArrayPlusExtra;

let mut arr: ArrayPlusExtra<i32, 2, 2> = ArrayPlusExtra::new(0);

// Modify through deref_mut.
arr[0] = 10;
arr[1] = 20;
arr[2] = 30;
arr[3] = 40;

assert_eq!(arr[0], 10);
assert_eq!(arr[3], 40);

Const contexts

use array_plus_extra::ArrayPlusExtra;

const ARR: ArrayPlusExtra<u8, 3, 2> = ArrayPlusExtra::new(255);
const SLICE: &[u8] = ARR.as_slice();
const LEN: usize = SLICE.len();

assert_eq!(LEN, 5);
assert_eq!(SLICE[0], 255);

Testing

Run tests:

cargo test

Run tests with Miri (requires nightly):

cargo +nightly miri test

Minimum Supported Rust Version (MSRV)

This crate requires Rust 1.85 or later due to the use of Edition 2024 and const fn features.

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.

array-plus-extra 0.2.0