unaligned

A #![no_std] crate containing types for encapsulating unaligned values.

The primary type this crate provides is Unaligned<T>, which stores a value of type T unaligned. Storing values unaligned can be an alternative to using #[repr(packed)] structs (which can only be used unsafely) or carefully-sized byte arrays. The Unaligned<T> type exposes a safe mutable API for working with unaligned values, while the companion type UnalignedCell<T> is an interior mutability type that provides a shared mutable API for working with unaligned values.

Because references are required to be aligned, it is unsafe to take a reference to a potentially unaligned value. The Unaligned<T> type therefore encapsulates the unaligned-ness of the value, letting code take (safe) references to Unaligned<T>. It also provides safe mutable APIs to set, replace, and access the value without taking an unaligned reference.

Note that, in general, a safe shared API is not possible for unaligned values, because in order to do anything useful with an unaligned value, the value must be moved into aligned storage - an inherently exclusive operation. The UnalignedCell<T> type somewhat alleviates this restriction by allowing exclusive access through a shared API using the power of interior mutability.

This crate is #![no_std] by default. The std feature can be enabled to access functionality that requires the full standard library.