Struct hashbrown::hash_table::OccupiedEntry

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pub struct OccupiedEntry<'a, T, A = Global>where
    A: Allocator,
{ /* private fields */ }

Expand description

A view into an occupied entry in a HashTable. It is part of the Entry enum.

§Examples

use hashbrown::hash_table::{Entry, OccupiedEntry};
use hashbrown::{HashTable, DefaultHashBuilder};
use std::hash::BuildHasher;

let mut table = HashTable::new();
let hasher = DefaultHashBuilder::default();
let hasher = |val: &_| hasher.hash_one(val);
for x in ["a", "b", "c"] {
    table.insert_unique(hasher(&x), x, hasher);
}
assert_eq!(table.len(), 3);

let _entry_o: OccupiedEntry<_, _> = table.find_entry(hasher(&"a"), |&x| x == "a").unwrap();
assert_eq!(table.len(), 3);

// Existing key
match table.entry(hasher(&"a"), |&x| x == "a", hasher) {
    Entry::Vacant(_) => unreachable!(),
    Entry::Occupied(view) => {
        assert_eq!(view.get(), &"a");
    }
}

assert_eq!(table.len(), 3);

// Existing key (take)
match table.entry(hasher(&"c"), |&x| x == "c", hasher) {
    Entry::Vacant(_) => unreachable!(),
    Entry::Occupied(view) => {
        assert_eq!(view.remove().0, "c");
    }
}
assert_eq!(table.find(hasher(&"c"), |&x| x == "c"), None);
assert_eq!(table.len(), 2);

Implementations§

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impl<'a, T, A> OccupiedEntry<'a, T, A>
where A: Allocator,

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pub fn remove(self) -> (T, VacantEntry<'a, T, A>)

Takes the value out of the entry, and returns it along with a VacantEntry that can be used to insert another value with the same hash as the one that was just removed.

§Examples

use hashbrown::hash_table::Entry;
use hashbrown::{HashTable, DefaultHashBuilder};
use std::hash::BuildHasher;

let mut table: HashTable<&str> = HashTable::new();
let hasher = DefaultHashBuilder::default();
let hasher = |val: &_| hasher.hash_one(val);
// The table is empty
assert!(table.is_empty() && table.capacity() == 0);

table.insert_unique(hasher(&"poneyland"), "poneyland", hasher);
let capacity_before_remove = table.capacity();

if let Entry::Occupied(o) = table.entry(hasher(&"poneyland"), |&x| x == "poneyland", hasher) {
    assert_eq!(o.remove().0, "poneyland");
}

assert!(table
    .find(hasher(&"poneyland"), |&x| x == "poneyland")
    .is_none());
// Now table hold none elements but capacity is equal to the old one
assert!(table.len() == 0 && table.capacity() == capacity_before_remove);

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pub fn get(&self) -> &T

Gets a reference to the value in the entry.

§Examples

use hashbrown::hash_table::Entry;
use hashbrown::{HashTable, DefaultHashBuilder};
use std::hash::BuildHasher;

let mut table: HashTable<&str> = HashTable::new();
let hasher = DefaultHashBuilder::default();
let hasher = |val: &_| hasher.hash_one(val);
table.insert_unique(hasher(&"poneyland"), "poneyland", hasher);

match table.entry(hasher(&"poneyland"), |&x| x == "poneyland", hasher) {
    Entry::Vacant(_) => panic!(),
    Entry::Occupied(entry) => assert_eq!(entry.get(), &"poneyland"),
}

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pub fn get_mut(&mut self) -> &mut T

Gets a mutable reference to the value in the entry.

If you need a reference to the OccupiedEntry which may outlive the destruction of the Entry value, see into_mut.

§Examples

use hashbrown::hash_table::Entry;
use hashbrown::{HashTable, DefaultHashBuilder};
use std::hash::BuildHasher;

let mut table: HashTable<(&str, u32)> = HashTable::new();
let hasher = DefaultHashBuilder::default();
let hasher = |val: &_| hasher.hash_one(val);
table.insert_unique(hasher(&"poneyland"), ("poneyland", 12), |(k, _)| hasher(&k));

assert_eq!(
    table.find(hasher(&"poneyland"), |&(x, _)| x == "poneyland",),
    Some(&("poneyland", 12))
);

if let Entry::Occupied(mut o) = table.entry(
    hasher(&"poneyland"),
    |&(x, _)| x == "poneyland",
    |(k, _)| hasher(&k),
) {
    o.get_mut().1 += 10;
    assert_eq!(o.get().1, 22);

    // We can use the same Entry multiple times.
    o.get_mut().1 += 2;
}

assert_eq!(
    table.find(hasher(&"poneyland"), |&(x, _)| x == "poneyland",),
    Some(&("poneyland", 24))
);

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pub fn into_mut(self) -> &'a mut T

Converts the OccupiedEntry into a mutable reference to the value in the entry with a lifetime bound to the table itself.

If you need multiple references to the OccupiedEntry, see get_mut.

§Examples

use hashbrown::hash_table::Entry;
use hashbrown::{HashTable, DefaultHashBuilder};
use std::hash::BuildHasher;

let mut table: HashTable<(&str, u32)> = HashTable::new();
let hasher = DefaultHashBuilder::default();
let hasher = |val: &_| hasher.hash_one(val);
table.insert_unique(hasher(&"poneyland"), ("poneyland", 12), |(k, _)| hasher(&k));

assert_eq!(
    table.find(hasher(&"poneyland"), |&(x, _)| x == "poneyland",),
    Some(&("poneyland", 12))
);

let value: &mut (&str, u32);
match table.entry(
    hasher(&"poneyland"),
    |&(x, _)| x == "poneyland",
    |(k, _)| hasher(&k),
) {
    Entry::Occupied(entry) => value = entry.into_mut(),
    Entry::Vacant(_) => panic!(),
}
value.1 += 10;

assert_eq!(
    table.find(hasher(&"poneyland"), |&(x, _)| x == "poneyland",),
    Some(&("poneyland", 22))
);