Struct ahash::AHasher

pub struct AHasher { /* private fields */ }

A Hasher for hashing an arbitrary stream of bytes.

Instances of AHasher represent state that is updated while hashing data.

Each method updates the internal state based on the new data provided. Once all of the data has been provided, the resulting hash can be obtained by calling finish()

Clone is also provided in case you wish to calculate hashes for two different items that start with the same data.

Implementations

impl AHasher

pub fn new_with_keys(key1: u128, key2: u128) -> Self

Creates a new hasher keyed to the provided keys.

Normally hashers are created via AHasher::default() for fixed keys or RandomState::new() for randomly generated keys and RandomState::with_seeds(a,b) for seeds that are set and can be reused. All of these work at map creation time (and hence don’t have any overhead on a per-item bais).

This method directly creates the hasher instance and performs no transformation on the provided seeds. This may be useful where a HashBuilder is not desired, such as for testing purposes.

Example

use std::hash::Hasher;
use ahash::AHasher;

let mut hasher = AHasher::new_with_keys(1234, 5678);

hasher.write_u32(1989);
hasher.write_u8(11);
hasher.write_u8(9);
hasher.write(b"Huh?");

println!("Hash is {:x}!", hasher.finish());

Trait Implementations

impl Clone for AHasher

fn clone(&self) -> AHasher

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for AHasher

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for AHasher

Provides a default Hasher with fixed keys. This is typically used in conjunction with BuildHasherDefault to create AHashers in order to hash the keys of the map.

Generally it is preferable to use RandomState instead, so that different hashmaps will have different keys. However if fixed keys are desireable this may be used instead.

Example

use std::hash::BuildHasherDefault;
use ahash::{AHasher, RandomState};
use std::collections::HashMap;

let mut map: HashMap<i32, i32, BuildHasherDefault<AHasher>> = HashMap::default();
map.insert(12, 34);

fn default() -> AHasher

Constructs a new AHasher with fixed keys. If std is enabled these will be generated upon first invocation. Otherwise if the compile-time-rngfeature is enabled these will be generated at compile time. If neither of these features are available, hardcoded constants will be used.

Because the values are fixed, different hashers will all hash elements the same way. This could make hash values predictable, if DOS attacks are a concern. If this behaviour is not required, it may be preferable to use RandomState instead.

Examples

use ahash::AHasher;
use std::hash::Hasher;

let mut hasher_1 = AHasher::default();
let mut hasher_2 = AHasher::default();

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

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

impl Hasher for AHasher

Provides Hasher methods to hash all of the primitive types.

fn write_u8(&mut self, i: u8)

Writes a single u8 into this hasher.

fn write_u16(&mut self, i: u16)

Writes a single u16 into this hasher.

fn write_u32(&mut self, i: u32)

Writes a single u32 into this hasher.

fn write_u128(&mut self, i: u128)

Writes a single u128 into this hasher.

fn write_usize(&mut self, i: usize)

Writes a single usize into this hasher.

fn write_u64(&mut self, i: u64)

Writes a single u64 into this hasher.

fn write(&mut self, input: &[u8])

Writes some data into this Hasher.

fn finish(&self) -> u64

Returns the hash value for the values written so far.

fn write_i8(&mut self, i: i8)

Writes a single i8 into this hasher.

fn write_i16(&mut self, i: i16)

Writes a single i16 into this hasher.

fn write_i32(&mut self, i: i32)

Writes a single i32 into this hasher.

fn write_i64(&mut self, i: i64)

Writes a single i64 into this hasher.

fn write_i128(&mut self, i: i128)

Writes a single i128 into this hasher.

fn write_isize(&mut self, i: isize)

Writes a single isize into this hasher.

fn write_length_prefix(&mut self, len: usize)

🔬This is a nightly-only experimental API. (hasher_prefixfree_extras)

Writes a length prefix into this hasher, as part of being prefix-free.

fn write_str(&mut self, s: &str)

🔬This is a nightly-only experimental API. (hasher_prefixfree_extras)

Writes a single str into this hasher.