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prataprc / jsondata

JSON processor
https://docs.rs/jsondata
MIT License
9 stars 3 forks source link

Hash stability #17

Open prataprc opened 2 years ago

prataprc commented 2 years ago

Values in jsondata::Json should not change in its hash value for any given hashing algorithm. Also the serialized form of jsondata::Json should not affect its hash value for any give hashing algorithm.

List of common hashing algorithm:

fasthash::city fasthash::murmur3 SHA1

Roenbaeck commented 2 years ago

Json currently does not implement Hash. Given that it's internally sorted, from what I understand, I added this impl.

impl Hash for Json{
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.to_string().hash(state);
    }
}

Under what circumstances would two semantically equal JSON documents produce different hashes using this approach?

prataprc commented 2 years ago

to_string is part of ToString trait, which in turn is consumed by fmt::Display, which is meant for human consumption of data. So we cannot make any guarantees on the output of ToString, it might change later.