bloomfilter.erl

-module(bloomfilter).

-export([new/1, insert/2, contains/2]).

-define(PREFIX, [<<"foo">>, <<"bar">>, <<"baz">>]).

new(Size) ->
    {bf, Size, atomics:new(Size, [])}.

insert({bf, Size, Ref}, Key) ->
    [atomics:put(Ref, Index, 1) || Index <- indexes(Key, Size)].

contains({bf, Size, Ref}, Key) ->
    lists:all(fun (Index) -> atomics:get(Ref, Index) =:= 1 end, indexes(Key, Size)).

%% private
indexes(Key, Size) ->
    [binary:decode_unsigned(crypto:hash(blake2b, <<Prefix/binary, Key/binary>>)) rem Size || Prefix <- ?PREFIX].