jfrimmel / partial-array

A rust crate providing a potentially partial-filled array

partial-array - potentially partial-filled arrays for #![no_std]

This crate provides a central new data type, similar to an array: the PartialArray<N>. It is equivalent to an array, but the number of entries might be anywhere from 0 to N. While this has similarities to a Vec<T> keep in mind, that a PartialArray does not grow its memory: it always takes up the memory for the fully array (with some additional counter) and it cannot ever hold more than N elements. This means that its memory is fully static and on the stack, making it usable from #![no_std] crates.

// some filter function, even numbers as an easy example
let f = |x: &i32| x % 2 == 0;

let array: partial_array::PartialArray<i32, 32> = (0..).take(32).filter(f).collect();

Features

This crate is rather simple, but has a few key features, that might enable this crate to be considered:

• zero dependencies
• #![no_std] (enabled for embedded targets without dynamic memory)
• only few unsafe code, can be audited easily
• open source
• permissive license

Example usage

This new data type is most likely to be used for collecting iterators into arrays, when then length is not known, but has an upper bound, e.g.:

use partial_array::PartialArray;

/// Take the first 10 elements of an iterator, that match the condition.
///
/// This can return less than 10 elements if the iterator has fewer than 10
/// items or there are less than 10 matching elements.
fn first_10_matching<T, I, F>(iter: I, check: F) -> PartialArray<T, 10>
    where I: IntoIterator<Item = T>,
          F: FnMut(&T) -> bool,
{
    iter.into_iter().filter(check).take(10).collect()
}