HashCow

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HashCow is a Rust HashMap implementation with copy-on-write keys and values.

Originally built for optimizing the Purple Protocol, this library provides a way to link HashMaps in memory that have duplicate entries. Instead of the duplicate data, it is instead borrowed and it is only cloned when mutation is needed.

Using HashCow

```rust use hashcow::{Form, CowHashMap};

let mut hm: CowHashMap

// We insert an owned value in the map hm.insertowned("key".toowned(), vec![1, 2, 3]); asserteq!(hm.entryform(&"key").unwrap(), Form::Owned);

// We now create a clone with borrowed fields let mut hmclone = hm.borrowfields(); asserteq!(hmclone.entry_form(&"key").unwrap(), Form::Borrowed);

// On mutation, the borrowed entry is cloned let entry = hmclone.getmut(&"key").unwrap();

// We now mutate the cloned value *entry = vec![4, 5, 6]; asserteq!(hmclone.entry_form(&"key").unwrap(), Form::Owned);

// The two maps now have different entries for the same key asserteq!(hm.get(&"key").unwrap(), &[1, 2, 3]); asserteq!(hm_clone.get(&"key").unwrap(), &[4, 5, 6]); ```

Contributing

We welcome anyone wishing to contribute to HashCow! Check out the issues section of the repository before starting out.

License

HashCow is licensed under the MIT license.