Resetting the hash

[darleybarreto]

Hi, thanks for porting this to Rust! Is there anything similar to XXH64_reset to reset/reuse the hash? Or should I make a new one using new? Thanks in advance!

Regards,

[shepmaster]

I don't see a particular benefit to having a reset function — I'd just replace the hash value directly and expect the compiler to make up the difference.

[darleybarreto]

Hmm, suppose I have the following operations:

let mut hash = XxHash64::with_seed(0);
hash.write(...);
// reset here

How would I replace the internal hash value with a new one based on a seed S?

[shepmaster]

I must be missing something. Wouldn't you do

let mut hash = XxHash64::with_seed(0);
hash.write(...);
// reset here
let mut hash = XxHash64::with_seed(0);

[darleybarreto]

Oh, I see, basically creating a new one. So if I need to use in a struct, that would be:

struct MyObject{
    hash: Cell<XxHash64>, // or something else with interior mutability
}

Right?

[shepmaster]

if I need to use in a struct

I'd expect that you'd make the methods take &mut self so there's no need for interior mutability:

struct MyObject{
    hash: XxHash64,
}

impl MyObject {
    fn foo(&mut self) {
        self.hash.write(...);
        self.hash = XxHash64::new();
    }
}

but sure, if you need interior mutability for some other reason, that also works.

[darleybarreto]

That's one option indeed. Thanks for your quick responses! Stay safe.