Wolvereness / dst

Data structures for Rust Dynamically Sized Types

This crate is intended to provide data structures that use DSTs (dynamically sized types).

Overview

The goal of this crate is to provide data structures that can store DSTs in a contiguous allocation. Some applications may have a performance benefit for using a contiguous allocation as opposed to multiple pointers.

Currently, the only implementation is a Vec where the DST-tails are slices of the same length.

Usage

Add to dependencies:

[dependencies]
dst = "0.1.0"

Use in the code:

use dst::FixedVec;
fn main() {
    let mut vec = FixedVec::<Option<&str>, usize>::new(4);
    vec.push_default();
    let item = vec.get(0).unwrap();
    assert_eq!(item.value, None);
    assert_eq!(item.tail, [0, 0, 0, 0]);
    
    vec.push(Some("Name"), [1, 2, 3, 4].iter().copied());
    let item = vec.get(1).unwrap();
    assert_eq!(item.value, Some("Name"));
    assert_eq!(item.tail, [1, 2, 3, 4]);
}

Flags

• undefined_behavior (disabled by default)

  This flag enables the project to build on stable Rust, but by utilizing code with UB. Specifically, invalid intermediate references are used to obtain a pointer to initialize data and to obtain layout information. See:

  • Raw-reference to value by syntax, rust-lang/rust#64490
  • Raw-reference to value by macro, rust-lang/rust#73394
  • Size of value, rust-lang/rust#69835
  • Layout of value, rust-lang/rust#69835

• unstable (enabled by default)

  This flag enables use of unstable Rust APIs. Specifically it allows UB to be avoided, but also changes some of the crate's layout and size API to use const functions (presumably giving a runtime performance benefit). See rust-lang/rust#46571