My application memory-maps a large block of binary data into memory. That binary data consists of fixed structures with 20 bytes each. I have a function that performs all the unsafe reinterpreting: fn reinterpret_hashblock<'a>(s: &'a [u8]) -> &'a [[u8; 20]] { const ELEM_SIZE: usize = 20; as…

This is usually called a self-referential type, which Rust doesn't safely support, but it is possible with the help of something like rental or owning_ref .

I've seen owning_ref (probably should've mentioned that in my initial post), but I was kind of put off by the fact that it doesn't seem maintained and that people found lots of unsoundness within it and nobody seemed to actually deal with it. rental seems abandonend (its GitHub is archived and the a…

The best way to fix this issue is to restructure your code. For example: struct HashSet<'a> { mmap: &'a Mmap, sorted_hashes: &'a [[u8; 20]], } impl<'a> HashSet<'a> { fn new(hash_block_data: &'a Mmap) -> Self { let hash_block = reinterpret_hashblock(hash_block_data); Sel…

Another way is to separate out the checks and the creation of the slice, something like // This can be used in `[u8; HASHBLOCK_ELEM_SIZE]` too, to elide some checks // against `[u8; 20]` pub const HASHBLOCK_ELEM_SIZE: usize = 20; pub struct HashSet { mmap: Mmap, count: usize, } // TODO: P…

Thanks everyone for your answers. I ended up just moving the Mmap out of the structure entirely since I only really needed the sorted_hashes field, the mmap field was just there because I knew that I needed it in that struct for lifetime purposes. I didn't want to go for enforcing invariants at crea…

Self referential types are difficult to reconcile with how Rust's current best effort aliasing model: Stacked Borrows ( see why here ).

[image] lorenz: Out of curiosity: Is this something Rust eventually wants to support or is this in some way fundamentally incompatible with Rust's way of doing lifetimes? As far as I know there is an interest, but no dedicated team and it would be a large effort. I.e. if it does come to be, …

Rental isn't maintained anymore, Ouroboros is its successor.

Storing reference together with owner

help

qaopm February 19, 2021, 9:33am 10

Topic		Replies	Views
Mmap and references to Mmap in same struct help	2	438	September 3, 2023
Help with lifetimes and references	2	498	February 20, 2021
How to write software without self-referential structs? help	15	7587	November 26, 2017
New to Lifetimes: borrowing and ownership help	4	168	December 4, 2024
Lifetimes of references in HashMaps help	7	1108	October 24, 2019

Storing reference together with owner

Related topics