Struct std::hash::BuildHasherDefault

pub struct BuildHasherDefault<H>(PhantomData<fn() -> H>);

Used to create a default BuildHasher instance for types that implement Hasher and Default.

BuildHasherDefault<H> can be used when a type H implements Hasher and Default, and you need a corresponding BuildHasher instance, but none is defined.

Any BuildHasherDefault is zero-sized. It can be created with default. When using BuildHasherDefault with HashMap or HashSet, this doesn’t need to be done, since they implement appropriate Default instances themselves.

Examples

Using BuildHasherDefault to specify a custom BuildHasher for HashMap:

use std::collections::HashMap;
use std::hash::{BuildHasherDefault, Hasher};

#[derive(Default)]
struct MyHasher;

impl Hasher for MyHasher {
    fn write(&mut self, bytes: &[u8]) {
        // Your hashing algorithm goes here!
       unimplemented!()
    }

    fn finish(&self) -> u64 {
        // Your hashing algorithm goes here!
        unimplemented!()
    }
}

type MyBuildHasher = BuildHasherDefault<MyHasher>;

let hash_map = HashMap::<u32, u32, MyBuildHasher>::default();

Tuple Fields

0: PhantomData<fn() -> H>

Trait Implementations

impl<H> BuildHasher for BuildHasherDefault<H>where H: Default + Hasher,

type Hasher = H

Type of the hasher that will be created.

fn build_hasher(&self) -> H

Creates a new hasher.

impl<H> Clone for BuildHasherDefault<H>

fn clone(&self) -> BuildHasherDefault<H>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<H> Debug for BuildHasherDefault<H>

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

Formats the value using the given formatter.

impl<H> Default for BuildHasherDefault<H>

fn default() -> BuildHasherDefault<H>

Returns the “default value” for a type.

impl<H> Eq for BuildHasherDefault<H>

fn assert_receiver_is_total_eq(&self)

impl<H> PartialEq<BuildHasherDefault<H>> for BuildHasherDefault<H>

fn eq(&self, _other: &BuildHasherDefault<H>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.