Cuckoo filter is a Bloom filter replacement for approximated set-membership queries. While Bloom filters are well-known space-efficient data structures to serve queries like "if item x is in a set?", they do not support deletion. Their variances to enable deletion (like counting Bloom filters) usually require much more space.
Cuckoo filters provide the flexibility to add and remove items dynamically. A cuckoo filter is based on cuckoo hashing (and therefore named as cuckoo filter). It is essentially a cuckoo hash table storing each key's fingerprint. Cuckoo hash tables can be highly compact, thus a cuckoo filter could use less space than conventional Bloom filters, for applications that require low false positive rates (< 3%).
For details about the algorithm and citations please use this article for now
"Cuckoo Filter: Better Than Bloom" by Bin Fan, Dave Andersen and Michael Kaminsky
```rust extern crate cuckoofilter;
...
let value: &str = "hello world";
// Create cuckoo filter with default max capacity of 1000000 items let mut cf = cuckoofilter::new();
// Add data to the filter let success = cf.add(value).unwrap(); // success ==> Ok(())
// Lookup if data is in the filter let success = cf.contains(value); // success ==> true
// Test and add to the filter (if data does not exists then add) let success = cf.testandadd(value).unwrap(); // success ==> Ok(false)
// Remove data from the filter. let success = cf.delete(value); // success ==> true ```
This crate has a C interface for embedding it into other languages than Rust. See the C Interface Documentation for more details.
NotEnoughSpace, the element given is actually added to the filter, but some random other
element gets removed. This could be improved by implementing a single-item eviction cache for that removed item.