mashmap/

lib.rs

#![cfg_attr(feature = "nightly", feature(core_intrinsics))]

//! A flat HashMap that supports multiple entries per key.
//!
//! This is an adaptation of Rust's standard `HashMap` (using [hashbrown](https://github.com/rust-lang/hashbrown)'s [`RawTable`](https://docs.rs/hashbrown/0.14.5/hashbrown/raw/struct.RawTable.html)) to support multiple entries with the same key.
//! While a common approach is to use a `HashMap<K, Vec<V>>` to store the entries corresponding to a key in a `Vec`, [`MashMap`] keeps a flat layout and stores all entries in the same table using probing to select the slots.
//! This approach avoids the memory indirection caused by vector pointers, and reduces memory overhead since it avoids storing the pointer + length + capacity of a vector for each key.
//!
//! ```rust
//! use mashmap::MashMap;
//!
//! let mut map = MashMap::<usize, usize>::new();
//! map.insert(1, 10);
//! map.insert(1, 11);
//! map.insert(1, 12);
//! map.insert(2, 20);
//! map.insert(2, 21);
//!
//! // iterate over the values with key `1` with mutable references and increment them
//! for val in map.get_mut_iter(&1) {
//!     *val += 1;
//! }
//!
//! // collect the values with keys `1` and `2`
//! // note that the order may differ from the insertion order
//! let mut values_1: Vec<_> = map.get_iter(&1).copied().collect();
//! let mut values_2: Vec<_> = map.get_iter(&2).copied().collect();
//! values_1.sort_unstable();
//! values_2.sort_unstable();
//!
//! assert_eq!(values_1, vec![11, 12, 13]);
//! assert_eq!(values_2, vec![20, 21]);
//! ```

pub(crate) mod exhaust;
mod map;

pub use map::*;