Trait std::hash::BuildHasher

pub trait BuildHasher {
    type Hasher: Hasher;
    fn build_hasher(&self) -> Self::Hasher;
}

A trait for creating instances of Hasher.

A BuildHasher is typically used (e.g. by HashMap) to create Hashers for each key such that they are hashed independently of one another, since Hashers contain state.

For each instance of BuildHasher, the Hashers created by build_hasher should be identical. That is, if the same stream of bytes is fed into each hasher, the same output will also be generated.

Examples

use std::collections::hash_map::RandomState;
use std::hash::{BuildHasher, Hasher};

let s = RandomState::new();
let mut hasher_1 = s.build_hasher();
let mut hasher_2 = s.build_hasher();

hasher_1.write_u32(8128);
hasher_2.write_u32(8128);

assert_eq!(hasher_1.finish(), hasher_2.finish());

Associated Types

type Hasher: Hasher

Type of the hasher that will be created.

Required Methods

fn build_hasher(&self) -> Self::Hasher

Creates a new hasher.

Each call to build_hasher on the same instance should produce identical Hashers.

Examples

use std::collections::hash_map::RandomState;
use std::hash::BuildHasher;

let s = RandomState::new();
let new_s = s.build_hasher();

Implementors

• impl<H> BuildHasher for BuildHasherDefault<H> where
    H: Default + Hasher,  type Hasher = H;
• impl BuildHasher for RandomState type Hasher = DefaultHasher;