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

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

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)));

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)));

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

Formats the value using the given formatter. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.