COW HashMap

This crate takes the original hashmap implementation that was ported from Google's high-performance [SwissTable] hash map and wraps it in AtomicPtr compare and replace operations which give it copy-on-write sementics.

Note: That inserting values into the hashmap will copy the entire hashmap every time thus inserts are no where near as fast as the original swishtable implementation however they do execute the operation lock-free while concurrent reads can happen in parallel. Essentially this construct is really good for read intensive operations.

Access the values at the leafs of the hashmap are also copy-on-write thus readonly access is very fast however writes will copy the original value and perform a compare-and-swap operation.

Many of the constructs that use lamda functions to perform write operations have been implemented inside the compare-and-swap loop thus they allow for concurrent writes without losing data however when accessing a value using get_mut the value you be entirely replaced when it falls out of scope.

Usage

Add this to your Cargo.toml:

[dependencies]
cow_hashbrown = "0.1"

Then:

use cow_hashmap::CowHashMap;

let map = CowHashMap::new();
map.insert(1, "one");

License

Licensed under either of:

• Apache License, Version 2.0, (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.