inline-array

InlineArray is a stack-inlinable array of bytes that is intended for situations where many bytes are being shared in database-like scenarios, where optimizing for space usage is extremely important.

InlineArray uses 8 bytes on the stack. It will inline arrays of up to 7 bytes. If the bytes are longer than that, it will store them in an optimized reference-count-backed structure of two different variants. For arrays up to length 255, the data is stored with an AtomicU8 reference counter and u8 length field, for only two bytes of overhead. For values larger than that, they are stored with an AtomicU16 reference counter and a 48-bit length field. If the maximum counter is reached for either variant, the bytes are copied into a new InlineArray with a fresh reference count of 1. This is made with the assumption that most reference counts will be far lower than 2^16 and only rarely surpassing 255 in the small case.

The inline and both types of shared instances of InlineArray guarantee that the stored array is always aligned to 8-byte boundaries, regardless of if it is inline on the stack or shared on the heap. This is advantageous for using in combination with certain zero-copy serialization techniques that require alignment guarantees.

Byte arrays that require more than 48 bits to store their length (256 terabytes) are not supported.

InlineArray::make_mut can be used for getting a mutable reference to the bytes in this structure. If the shared reference counter is higher than 1, this acts like a Cow and will make self into a private copy that is safe for modification.

Features

• serde implements serde::Serialize and serde::Deserialize for InlineArray (disabled by default)

Examples

use inline_array::InlineArray;

let ia = InlineArray::from(b"yo!");

// then use it more or less like you would an Arc<[u8]>