Allow Hash object reuse

[kwasimensah]

What is the problem this feature will solve?

#25857 (comment)

I'm creating the hash of many small objects and need to keep track of these individual hashes so #29903 doesn't work.

My specific use case is that I'm hashing directory layouts to setup a file layout that's optimal about symlinking entire directories when its filled with symlinked entries that all point to the same source directory. I can get into specifics if that matters.

What is the feature you are proposing to solve the problem?

crypto.Hash.reset() - reset the internal state of the hasher and allows it to be reused with any new allocations

What alternatives have you considered?

-not use crypto.hash in this case and write my own hasher
-create a native add on that lets me manage to hash context according to my needs

[kwasimensah]

This was discussed before at #25857 but with #25857 (comment) it seems there was an assumption that people don't need to hash a lot of small strings.

There were worries about what the UX of allowing resets of this object but there seems to be several APIs in node that have a reset function now.

[mscdex]

Have you actually determined that createHash() is bottlenecking your application?

[kwasimensah]

It’s not a bottle neck but it’s showing up enough on cpu-prof profiles that it’d be great to remove it. I’m doing some profiling/writing benchmarks and this came up as a possible win

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[kwasimensah]

I'm happy to try and contribute this myself if people are ok with the idea of adding this function

[bnoordhuis]

I think a .reset() method would be okay.

The lack of orthogonality w.r.t. HMAC or Cipher (who you can't meaningfully reset) is a little jarring but 🤷

[tniessen]

IMHO an approach such as #42233 would be better assuming that this is about hashing small amounts of data.