Struct hashbrown::hash_map::RawEntryBuilderMut

pub struct RawEntryBuilderMut<'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_mut docs for usage examples.

Examples

use hashbrown::hash_map::{RawEntryBuilderMut, RawEntryMut::Vacant, RawEntryMut::Occupied};
use hashbrown::HashMap;
use core::hash::{BuildHasher, Hash};

let mut map = HashMap::new();
map.extend([(1, 11), (2, 12), (3, 13), (4, 14), (5, 15), (6, 16)]);
assert_eq!(map.len(), 6);

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 builder: RawEntryBuilderMut<_, _, _> = map.raw_entry_mut();

// Existing key
match builder.from_key(&6) {
    Vacant(_) => unreachable!(),
    Occupied(view) => assert_eq!(view.get(), &16),
}

for key in 0..12 {
    let hash = compute_hash(map.hasher(), &key);
    let value = map.get(&key).cloned();
    let key_value = value.as_ref().map(|v| (&key, v));

    println!("Key: {} and value: {:?}", key, value);

    match map.raw_entry_mut().from_key(&key) {
        Occupied(mut o) => assert_eq!(Some(o.get_key_value()), key_value),
        Vacant(_) => assert_eq!(value, None),
    }
    match map.raw_entry_mut().from_key_hashed_nocheck(hash, &key) {
        Occupied(mut o) => assert_eq!(Some(o.get_key_value()), key_value),
        Vacant(_) => assert_eq!(value, None),
    }
    match map.raw_entry_mut().from_hash(hash, |q| *q == key) {
        Occupied(mut o) => assert_eq!(Some(o.get_key_value()), key_value),
        Vacant(_) => assert_eq!(value, None),
    }
}

assert_eq!(map.len(), 6);

Implementations

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

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

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

Creates a RawEntryMut from the given key.

Examples

use hashbrown::hash_map::{HashMap, RawEntryMut};

let mut map: HashMap<&str, u32> = HashMap::new();
let key = "a";
let entry: RawEntryMut<&str, u32, _> = map.raw_entry_mut().from_key(&key);
entry.insert(key, 100);
assert_eq!(map[&"a"], 100);

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

where Q: Equivalent<K> + ?Sized,

Creates a RawEntryMut from the given key and its hash.

Examples

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

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 mut map: HashMap<&str, u32> = HashMap::new();
let key = "a";
let hash = compute_hash(map.hasher(), &key);
let entry: RawEntryMut<&str, u32, _> = map.raw_entry_mut().from_key_hashed_nocheck(hash, &key);
entry.insert(key, 100);
assert_eq!(map[&"a"], 100);

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

pub fn from_hash<F>(self, hash: u64, is_match: F) -> RawEntryMut<'a, K, V, S, A>

where for<'b> F: FnMut(&'b K) -> bool,

Creates a RawEntryMut from the given hash and matching function.

Examples

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

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 mut map: HashMap<&str, u32> = HashMap::new();
let key = "a";
let hash = compute_hash(map.hasher(), &key);
let entry: RawEntryMut<&str, u32, _> = map.raw_entry_mut().from_hash(hash, |k| k == &key);
entry.insert(key, 100);
assert_eq!(map[&"a"], 100);

Trait Implementations

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