Crate reinterpret

This crate provides convenient low-level utility functions for reinterpreting data. This includes Vecs and slices. These functions are intrinsically unsafe but are very useful in performance critical code since they avoid additional copies.

The goal of this crate is to provide some memory safety along the boundaries of Vecs and slices to reduce the boilerplate for reinterpreting data.

These functions check that the source and target arrays have the same size, however they don't check for safety of converting the contained types.

It is possible to write safe wrappers for converting collections of concrete types using these functions, however this is out of the scope of this crate.

Examples

    let points: Vec<[f64;2]> = vec![
        [0.1, 1.0],
        [1.2, 1.4],
        [0.5, 3.2],
    ];
    let coordinates: Vec<f64> = vec![0.1, 1.0, 1.2, 1.4, 0.5, 3.2];

    let point_coordinates: &[f64] = unsafe { reinterpret_slice(&points) };
    assert_eq!(*point_coordinates, *coordinates.as_slice()); // Same data.
    assert_eq!(point_coordinates, coordinates.as_slice()); // Same location in memory.

    let coordinate_points: &[[f64;2]] = unsafe { reinterpret_slice(&coordinates) };
    assert_eq!(*coordinate_points, *points.as_slice()); // Same data.
    assert_eq!(coordinate_points, points.as_slice()); // Same location in memory.

Undefined Behavior

There are ways to misuse these functions without causing panics that may produce undefined behavior. For instance:

    let a = 1;
    let b = 2;
    let v = vec![&a, &b];
    let mut m: Vec<&mut usize> = unsafe { reinterpret_vec(v) };
    *m[0] = 100; // Mutating an immutable variable a!

    assert_eq!(a, 100);

It is the users' responsibility to avoid these types of scenarios.

Functions

reinterpret_mut_slice⚠	Reinterpret a given slice as a slice of another type. This function checks that the resulting slice is appropriately sized.
reinterpret_slice⚠	Reinterpret a given slice as a slice of another type. This function checks that the resulting slice is appropriately sized.
reinterpret_vec⚠	Reinterpret a given Vec as a Vec of another type. This function checks that the resulting Vec is appropriately sized.