How to use flatbuffers `key` attribute to simulate HashMap with flatbuffers in Rust?

Asked Mar 16 '21 at 13:05

Active Mar 16 '21 at 13:36

Viewed 904 times

I need to create a string to string map with flatbuffers in Rust similar to:

pub struct HashMapIndex {
    keyword_by_filter: HashMap<String, String> // filter text -> keyword
}

I've found some key flatbuffers attribute that can be put on array item, but it seems to be neither documented nor shown in samples:

Can be used for in-place binary search

table KeywordToFilters {
  filter_text: string (key);
  keyword: string;
}

table Index {
  map: [KeywordToFilters];
}

How can i use it (get value by key)? The problem is that no map-like methods are generated - it's just a vector:

pub map: Option<flatbuffers::WIPOffset<flatbuffers::Vector<'a , flatbuffers::ForwardsUOffset<KeywordToFilters<'a >>>>>,

Is there more efficient way to have a map with flatbuffers in Rust?

PS. flatbuffers crate version is 0.8.3

edited Mar 16 '21 at 13:36

Stargateur

asked Mar 16 '21 at 13:05

4ntoine

I guess there is not https://stackoverflow.com/questions/51437592/how-to-store-dictionariesmap-in-flatbuffer-in-java – Stargateur Mar 16 '21 at 13:35
it's about Java, i guess the generated file can be different a lot – 4ntoine Mar 16 '21 at 13:36
I think there is no concept of hashmap in flatbuffers, that not surprising hashmap is not very memory efficient to parse and so I guess google want people to use vector putting the key and the value in one item, but that just supposition – Stargateur Mar 16 '21 at 13:38
2

https://github.com/google/flatbuffers/issues/5713 as I said – Stargateur Mar 16 '21 at 13:40
Yup, not implemented yet. – Aardappel Mar 16 '21 at 15:50
@Aardappel Please convert to the answer to be accepted – 4ntoine Mar 16 '21 at 19:26

0 Answers0