feat: Implement fixed length hash functions and optimize existing imlementations

[austinabell]

• Adds fixed length array versions of env hash functions (no reason to allocate if we know the length)
• Optimizes the existing impl to use this to avoid an extra syscall to register_len
  • I am assuming the compiler can optimize the creation on stack and copy to heap, but if not the cost should be trivial and these functions will probably be deprecated in future
• Added helper functions for reading to fixed-length arrays for re-use

I don't necessarily like suffixing _hash, but ideally this is a smooth transition to avoid hard-breaking changes if users expect a Vec<u8> over the array, even though this comes with a major version bump. Name suggestions welcome!

closes #645

[ChaoticTempest]

how about something like _unboxed instead of _hash? I think at least that would convey the difference, and even if we deprecate the one without the postfix, I think it still makes sense

[austinabell]

how about something like _unboxed instead of _hash? I think at least that would convey the difference, and even if we deprecate the one without the postfix, I think it still makes sense

I personally am confused with this wording, because I don't see what boxed refers to here or what unboxed means. What do you mean by this?

[ChaoticTempest]

@austinabell ahh my bad, I meant to say that _unboxed would show that you're returning something that isn't boxed/allocated inside something like a Vec<u8>, which would show the difference between the two functions. If you're confused by it, then it probably isn't good naming either then

[austinabell]

@austinabell ahh my bad, I meant to say that _unboxed would show that you're returning something that isn't boxed/allocated inside something like a Vec<u8>, which would show the difference between the two functions. If you're confused by it, then it probably isn't good naming either then

Could also suffix something like _array, to be descriptive, but I just thought that _hash would be most clear because at least it's explaining that these are hashes which might not be intuitive for those unfamiliar.

[ChaoticTempest]

Could also suffix something like _array, to be descriptive, but I just thought that _hash would be most clear because at least it's explaining that these are hashes which might not be intuitive for those unfamiliar.

But aren't they both hashes though? I think _array works since it should distinguish what's the different between the two return types

[austinabell]

Could also suffix something like _array, to be descriptive, but I just thought that _hash would be most clear because at least it's explaining that these are hashes which might not be intuitive for those unfamiliar.

But aren't they both hashes though? I think _array works since it should distinguish what's the different between the two return types

Was just giving a benefit to using hash suffix. I'll switch to array suffix since it might be more clear :)

[ChaoticTempest]

New changes LGTM