Struct hashbrown::hash_map::RawEntryBuilder

pub struct RawEntryBuilder<'a, K, V, S, A: Allocator = Global> { /* private fields */ }

A builder for computing where in a HashMap a key-value pair would be stored.

See the HashMap::raw_entry docs for usage examples.

Examples

use hashbrown::hash_map::{HashMap, RawEntryBuilder};
use core::hash::{BuildHasher, Hash};

let mut map = HashMap::new();
map.extend([(1, 10), (2, 20), (3, 30)]);

fn compute_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
    use core::hash::Hasher;
    let mut state = hash_builder.build_hasher();
    key.hash(&mut state);
    state.finish()
}

for k in 0..6 {
    let hash = compute_hash(map.hasher(), &k);
    let v = map.get(&k).cloned();
    let kv = v.as_ref().map(|v| (&k, v));

    println!("Key: {} and value: {:?}", k, v);
    let builder: RawEntryBuilder<_, _, _> = map.raw_entry();
    assert_eq!(builder.from_key(&k), kv);
    assert_eq!(map.raw_entry().from_hash(hash, |q| *q == k), kv);
    assert_eq!(map.raw_entry().from_key_hashed_nocheck(hash, &k), kv);
}

Implementations

impl<'a, K, V, S, A: Allocator> RawEntryBuilder<'a, K, V, S, A>

pub fn from_key<Q>(self, k: &Q) -> Option<(&'a K, &'a V)>

where S: BuildHasher, Q: Hash + Equivalent<K> + ?Sized,

Access an immutable entry by key.

Examples

use hashbrown::HashMap;

let map: HashMap<&str, u32> = [("a", 100), ("b", 200)].into();
let key = "a";
assert_eq!(map.raw_entry().from_key(&key), Some((&"a", &100)));

pub fn from_key_hashed_nocheck<Q>( self, hash: u64, k: &Q, ) -> Option<(&'a K, &'a V)>

where Q: Equivalent<K> + ?Sized,

Access an immutable entry by a key and its hash.

Examples

use core::hash::{BuildHasher, Hash};
use hashbrown::HashMap;

fn compute_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
    use core::hash::Hasher;
    let mut state = hash_builder.build_hasher();
    key.hash(&mut state);
    state.finish()
}

let map: HashMap<&str, u32> = [("a", 100), ("b", 200)].into();
let key = "a";
let hash = compute_hash(map.hasher(), &key);
assert_eq!(map.raw_entry().from_key_hashed_nocheck(hash, &key), Some((&"a", &100)));

pub fn from_hash<F>(self, hash: u64, is_match: F) -> Option<(&'a K, &'a V)>

where F: FnMut(&K) -> bool,

Access an immutable entry by hash and matching function.

Examples

use core::hash::{BuildHasher, Hash};
use hashbrown::HashMap;

fn compute_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
    use core::hash::Hasher;
    let mut state = hash_builder.build_hasher();
    key.hash(&mut state);
    state.finish()
}

let map: HashMap<&str, u32> = [("a", 100), ("b", 200)].into();
let key = "a";
let hash = compute_hash(map.hasher(), &key);
assert_eq!(map.raw_entry().from_hash(hash, |k| k == &key), Some((&"a", &100)));

Trait Implementations

impl<K, V, S, A: Allocator> Debug for RawEntryBuilder<'_, K, V, S, A>

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

Formats the value using the given formatter.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 8 bytes