77 lines
2.0 KiB
Rust
77 lines
2.0 KiB
Rust
use crate::FxHasher;
|
|
|
|
/// Type alias for a hashmap using the `fx` hash algorithm with [`FxSeededState`].
|
|
#[cfg(feature = "std")]
|
|
pub type FxHashMapSeed<K, V> = std::collections::HashMap<K, V, FxSeededState>;
|
|
|
|
/// Type alias for a hashmap using the `fx` hash algorithm with [`FxSeededState`].
|
|
#[cfg(feature = "std")]
|
|
pub type FxHashSetSeed<V> = std::collections::HashSet<V, FxSeededState>;
|
|
|
|
/// [`FxSeededState`] is an alternative state for `HashMap` types, allowing to use [`FxHasher`] with a set seed.
|
|
///
|
|
/// ```
|
|
/// # use std::collections::HashMap;
|
|
/// use rustc_hash::FxSeededState;
|
|
///
|
|
/// let mut map = HashMap::with_hasher(FxSeededState::with_seed(12));
|
|
/// map.insert(15, 610);
|
|
/// assert_eq!(map[&15], 610);
|
|
/// ```
|
|
#[derive(Clone)]
|
|
pub struct FxSeededState {
|
|
seed: usize,
|
|
}
|
|
|
|
impl FxSeededState {
|
|
/// Constructs a new `FxSeededState` that is initialized with a `seed`.
|
|
pub const fn with_seed(seed: usize) -> FxSeededState {
|
|
Self { seed }
|
|
}
|
|
}
|
|
|
|
impl core::hash::BuildHasher for FxSeededState {
|
|
type Hasher = FxHasher;
|
|
|
|
fn build_hasher(&self) -> Self::Hasher {
|
|
FxHasher::with_seed(self.seed)
|
|
}
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use core::hash::BuildHasher;
|
|
|
|
use crate::FxSeededState;
|
|
|
|
#[test]
|
|
fn cloned_seeded_states_are_equal() {
|
|
let seed = 2;
|
|
let a = FxSeededState::with_seed(seed);
|
|
let b = a.clone();
|
|
|
|
assert_eq!(a.seed, b.seed);
|
|
assert_eq!(a.seed, seed);
|
|
|
|
assert_eq!(a.build_hasher().hash, b.build_hasher().hash);
|
|
}
|
|
|
|
#[test]
|
|
fn same_seed_produces_same_hasher() {
|
|
let seed = 1;
|
|
let a = FxSeededState::with_seed(seed);
|
|
let b = FxSeededState::with_seed(seed);
|
|
|
|
// The hashers should be the same, as they have the same seed.
|
|
assert_eq!(a.build_hasher().hash, b.build_hasher().hash);
|
|
}
|
|
|
|
#[test]
|
|
fn different_states_are_different() {
|
|
let a = FxSeededState::with_seed(1);
|
|
let b = FxSeededState::with_seed(2);
|
|
|
|
assert_ne!(a.build_hasher().hash, b.build_hasher().hash);
|
|
}
|
|
}
|