Struct ahash::RandomState

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pub struct RandomState { /* private fields */ }

Expand description

Provides a Hasher factory. This is typically used (e.g. by HashMap) to create AHashers in order to hash the keys of the map. See build_hasher below.

Implementations

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impl RandomState

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pub fn set_random_source(
source: impl RandomSource + Send + Sync + 'static
) -> Result<(), bool>

Provides an optional way to manually supply a source of randomness for Hasher keys.

The provided [RandomSource] will be used to be used as a source of randomness by RandomState to generate new states. If this method is not invoked the standard source of randomness is used as described in the Readme.

The source of randomness can only be set once, and must be set before the first RandomState is created. If the source has already been specified Err is returned with a bool indicating if the set failed because method was previously invoked (true) or if the default source is already being used (false).

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pub fn new() -> RandomState

Use randomly generated keys

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pub fn generate_with(k0: u64, k1: u64, k2: u64, k3: u64) -> RandomState

Allows for supplying seeds, but each time it is called the resulting state will be different. This is done using a static counter, so it can safely be used with a fixed keys.

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pub fn with_seed(key: usize) -> RandomState

Allows for explicitly setting a seed to used.

Note: This method does not require the provided seed to be strong.

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pub const fn with_seeds(k0: u64, k1: u64, k2: u64, k3: u64) -> RandomState

Allows for explicitly setting the seeds to used.

Note: This method is robust against 0s being passed for one or more of the parameters or the same value being passed for more than one parameter.

Trait Implementations

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impl BuildHasher for RandomState

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fn build_hasher(&self) -> AHasher

Constructs a new AHasher with keys based on this RandomState object. This means that two different RandomStates will will generate AHashers that will return different hashcodes, but Hashers created from the same BuildHasher will generate the same hashes for the same input data.

Examples

use ahash::{AHasher, RandomState};
use std::hash::{Hasher, BuildHasher};

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

hasher_1.write_u32(1234);
hasher_2.write_u32(1234);

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

let other_build_hasher = RandomState::new();
let mut different_hasher = other_build_hasher.build_hasher();
different_hasher.write_u32(1234);
assert_ne!(different_hasher.finish(), hasher_1.finish());