Enum gstd::prelude::collections::hash_map::RawEntryMut

pub enum RawEntryMut<'a, K, V, S, A = Global>
where
    A: Allocator,
{
    Occupied(RawOccupiedEntryMut<'a, K, V, S, A>),
    Vacant(RawVacantEntryMut<'a, K, V, S, A>),
}

A view into a single entry in a map, which may either be vacant or occupied.

This is a lower-level version of Entry.

This enum is constructed through the raw_entry_mut method on HashMap, then calling one of the methods of that RawEntryBuilderMut.

Examples

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

let mut map = HashMap::new();
map.extend([('a', 1), ('b', 2), ('c', 3)]);
assert_eq!(map.len(), 3);

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()
}

// Existing key (insert)
let raw: RawEntryMut<_, _, _> = map.raw_entry_mut().from_key(&'a');
let _raw_o: RawOccupiedEntryMut<_, _, _> = raw.insert('a', 10);
assert_eq!(map.len(), 3);

// Nonexistent key (insert)
map.raw_entry_mut().from_key(&'d').insert('d', 40);
assert_eq!(map.len(), 4);

// Existing key (or_insert)
let hash = compute_hash(map.hasher(), &'b');
let kv = map
    .raw_entry_mut()
    .from_key_hashed_nocheck(hash, &'b')
    .or_insert('b', 20);
assert_eq!(kv, (&mut 'b', &mut 2));
*kv.1 = 20;
assert_eq!(map.len(), 4);

// Nonexistent key (or_insert)
let hash = compute_hash(map.hasher(), &'e');
let kv = map
    .raw_entry_mut()
    .from_key_hashed_nocheck(hash, &'e')
    .or_insert('e', 50);
assert_eq!(kv, (&mut 'e', &mut 50));
assert_eq!(map.len(), 5);

// Existing key (or_insert_with)
let hash = compute_hash(map.hasher(), &'c');
let kv = map
    .raw_entry_mut()
    .from_hash(hash, |q| q == &'c')
    .or_insert_with(|| ('c', 30));
assert_eq!(kv, (&mut 'c', &mut 3));
*kv.1 = 30;
assert_eq!(map.len(), 5);

// Nonexistent key (or_insert_with)
let hash = compute_hash(map.hasher(), &'f');
let kv = map
    .raw_entry_mut()
    .from_hash(hash, |q| q == &'f')
    .or_insert_with(|| ('f', 60));
assert_eq!(kv, (&mut 'f', &mut 60));
assert_eq!(map.len(), 6);

println!("Our HashMap: {:?}", map);

let mut vec: Vec<_> = map.iter().map(|(&k, &v)| (k, v)).collect();
// The `Iter` iterator produces items in arbitrary order, so the
// items must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, [('a', 10), ('b', 20), ('c', 30), ('d', 40), ('e', 50), ('f', 60)]);

Variants

Occupied(RawOccupiedEntryMut<'a, K, V, S, A>)

An occupied entry.

Examples

use hashbrown::{hash_map::RawEntryMut, HashMap};
let mut map: HashMap<_, _> = [("a", 100), ("b", 200)].into();

match map.raw_entry_mut().from_key(&"a") {
    RawEntryMut::Vacant(_) => unreachable!(),
    RawEntryMut::Occupied(_) => { }
}

Vacant(RawVacantEntryMut<'a, K, V, S, A>)

A vacant entry.

Examples

use hashbrown::{hash_map::RawEntryMut, HashMap};
let mut map: HashMap<&str, i32> = HashMap::new();

match map.raw_entry_mut().from_key("a") {
    RawEntryMut::Occupied(_) => unreachable!(),
    RawEntryMut::Vacant(_) => { }
}

Implementations

impl<'a, K, V, S, A> RawEntryMut<'a, K, V, S, A>

where A: Allocator,

pub fn insert(self, key: K, value: V) -> RawOccupiedEntryMut<'a, K, V, S, A>

where K: Hash, S: BuildHasher,

Sets the value of the entry, and returns a RawOccupiedEntryMut.

Examples

use hashbrown::HashMap;

let mut map: HashMap<&str, u32> = HashMap::new();
let entry = map.raw_entry_mut().from_key("horseyland").insert("horseyland", 37);

assert_eq!(entry.remove_entry(), ("horseyland", 37));

pub fn or_insert(self, default_key: K, default_val: V) -> (&'a mut K, &'a mut V)

where K: Hash, S: BuildHasher,

Ensures a value is in the entry by inserting the default if empty, and returns mutable references to the key and value in the entry.

Examples

use hashbrown::HashMap;

let mut map: HashMap<&str, u32> = HashMap::new();

map.raw_entry_mut().from_key("poneyland").or_insert("poneyland", 3);
assert_eq!(map["poneyland"], 3);

*map.raw_entry_mut().from_key("poneyland").or_insert("poneyland", 10).1 *= 2;
assert_eq!(map["poneyland"], 6);

pub fn or_insert_with<F>(self, default: F) -> (&'a mut K, &'a mut V)

where F: FnOnce() -> (K, V), K: Hash, S: BuildHasher,

Ensures a value is in the entry by inserting the result of the default function if empty, and returns mutable references to the key and value in the entry.

Examples

use hashbrown::HashMap;

let mut map: HashMap<&str, String> = HashMap::new();

map.raw_entry_mut().from_key("poneyland").or_insert_with(|| {
    ("poneyland", "hoho".to_string())
});

assert_eq!(map["poneyland"], "hoho".to_string());

pub fn and_modify<F>(self, f: F) -> RawEntryMut<'a, K, V, S, A>

where F: FnOnce(&mut K, &mut V),

Provides in-place mutable access to an occupied entry before any potential inserts into the map.

Examples

use hashbrown::HashMap;

let mut map: HashMap<&str, u32> = HashMap::new();

map.raw_entry_mut()
   .from_key("poneyland")
   .and_modify(|_k, v| { *v += 1 })
   .or_insert("poneyland", 42);
assert_eq!(map["poneyland"], 42);

map.raw_entry_mut()
   .from_key("poneyland")
   .and_modify(|_k, v| { *v += 1 })
   .or_insert("poneyland", 0);
assert_eq!(map["poneyland"], 43);

pub fn and_replace_entry_with<F>(self, f: F) -> RawEntryMut<'a, K, V, S, A>

where F: FnOnce(&K, V) -> Option<V>,

Provides shared access to the key and owned access to the value of an occupied entry and allows to replace or remove it based on the value of the returned option.

Examples

use hashbrown::HashMap;
use hashbrown::hash_map::RawEntryMut;

let mut map: HashMap<&str, u32> = HashMap::new();

let entry = map
    .raw_entry_mut()
    .from_key("poneyland")
    .and_replace_entry_with(|_k, _v| panic!());

match entry {
    RawEntryMut::Vacant(_) => {},
    RawEntryMut::Occupied(_) => panic!(),
}

map.insert("poneyland", 42);

let entry = map
    .raw_entry_mut()
    .from_key("poneyland")
    .and_replace_entry_with(|k, v| {
        assert_eq!(k, &"poneyland");
        assert_eq!(v, 42);
        Some(v + 1)
    });

match entry {
    RawEntryMut::Occupied(e) => {
        assert_eq!(e.key(), &"poneyland");
        assert_eq!(e.get(), &43);
    },
    RawEntryMut::Vacant(_) => panic!(),
}

assert_eq!(map["poneyland"], 43);

let entry = map
    .raw_entry_mut()
    .from_key("poneyland")
    .and_replace_entry_with(|_k, _v| None);

match entry {
    RawEntryMut::Vacant(_) => {},
    RawEntryMut::Occupied(_) => panic!(),
}

assert!(!map.contains_key("poneyland"));

Trait Implementations

impl<K, V, S, A> Debug for RawEntryMut<'_, K, V, S, A>

where K: Debug, V: Debug, A: Allocator,

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

Formats the value using the given formatter.