State for xxhash3_64 and oneshot for `T: Hash`

[tisonkun]

Hi @shepmaster!

I wonder if it's reasonable to add State hasher builder for xxhash3_64 variant as well, since it's available for xxhash64.

Besides, the current oneshot convenient methods are for &[u8]. I have a use case where, if it works for T: Hash, it can simplify code further.

If either or both are valid, I'm glad to submit a patch.

[shepmaster]

I wonder if it's reasonable to add State hasher builder for xxhash3_64 variant as well,

I do not understand what you mean. Can you provide some pseudocode that shows what you'd be able to do with the new functionality?

Are you trying to say that BuildHasher should be implemented? If so, some decision would need to be made about which seed and secret would be provided.

since it's available for xxhash64

Just because one hasher does something doesn't imply that another should also. XxHash{32,64} were created years ago and my skill and experience have increased since then.

For example, if I wrote it today, XxHash32 would not implement Hasher because it only creates a 32-bit value. You can see that XxHash3_128 learned that lesson.

the current oneshot convenient methods are for &[u8]. I have a use case where, if it works for T: Hash, it can simplify code further.

I don't believe I understand your suggestion here. The oneshot methods exist because they are given the entire stream of bytes to hash and thus can avoid keeping around intermediate state and buffers. If you don't have the entire set of bytes in a slice (e.g. an arbitrary T), then you will need somewhere to keep the bytes and related state. It sounds like you may be looking for BuildHasher::hash_one?

[tisonkun]

It sounds like you may be looking for BuildHasher::hash_one?

Yes. This is what I want, for xxhash3_64.

Currently, xxhash3_64 provides only Hasher. And I noticed that xxhash64 has State, so I ask if we can implement something similar to xxhash3_64.