Enum Entry

pub enum Entry<'a, T, A = Global>
where
    A: Allocator,
{
    Occupied(OccupiedEntry<'a, T, A>),
    Vacant(VacantEntry<'a, T, A>),
}

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

This enum is constructed from the entry method on HashTable.

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);

// Existing value (insert)
let entry: Entry<_> = table.entry(hasher(&"a"), |&x| x == "a", hasher);
let _raw_o: OccupiedEntry<_, _> = entry.insert("a");
assert_eq!(table.len(), 3);
// Nonexistent value (insert)
table.entry(hasher(&"d"), |&x| x == "d", hasher).insert("d");

// Existing value (or_insert)
table
    .entry(hasher(&"b"), |&x| x == "b", hasher)
    .or_insert("b");
// Nonexistent value (or_insert)
table
    .entry(hasher(&"e"), |&x| x == "e", hasher)
    .or_insert("e");

println!("Our HashTable: {:?}", table);

let mut vec: Vec<_> = table.iter().copied().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", "b", "c", "d", "e"]);

Variants

Occupied(OccupiedEntry<'a, T, A>)

An occupied entry.

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"] {
    table.insert_unique(hasher(&x), x, hasher);
}

match table.entry(hasher(&"a"), |&x| x == "a", hasher) {
    Entry::Vacant(_) => unreachable!(),
    Entry::Occupied(_) => {}
}

Vacant(VacantEntry<'a, T, A>)

A vacant entry.

Examples

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

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

match table.entry(hasher(&"a"), |&x| x == "a", hasher) {
    Entry::Vacant(_) => {}
    Entry::Occupied(_) => unreachable!(),
}

Implementations

impl<'a, T, A> Entry<'a, T, A>

where A: Allocator,

pub fn insert(self, value: T) -> OccupiedEntry<'a, T, A>

Sets the value of the entry, replacing any existing value if there is one, and returns an OccupiedEntry.

Examples

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);

let entry = table
    .entry(hasher(&"horseyland"), |&x| x == "horseyland", hasher)
    .insert("horseyland");

assert_eq!(entry.get(), &"horseyland");

pub fn or_insert(self, default: T) -> OccupiedEntry<'a, T, A>

Ensures a value is in the entry by inserting if it was vacant.

Returns an OccupiedEntry pointing to the now-occupied entry.

Examples

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);

// nonexistent key
table
    .entry(hasher(&"poneyland"), |&x| x == "poneyland", hasher)
    .or_insert("poneyland");
assert!(table
    .find(hasher(&"poneyland"), |&x| x == "poneyland")
    .is_some());

// existing key
table
    .entry(hasher(&"poneyland"), |&x| x == "poneyland", hasher)
    .or_insert("poneyland");
assert!(table
    .find(hasher(&"poneyland"), |&x| x == "poneyland")
    .is_some());
assert_eq!(table.len(), 1);

pub fn or_insert_with( self, default: impl FnOnce() -> T, ) -> OccupiedEntry<'a, T, A>

Ensures a value is in the entry by inserting the result of the default function if empty..

Returns an OccupiedEntry pointing to the now-occupied entry.

Examples

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

let mut table: HashTable<String> = HashTable::new();
let hasher = DefaultHashBuilder::default();
let hasher = |val: &_| hasher.hash_one(val);

table
    .entry(hasher("poneyland"), |x| x == "poneyland", |val| hasher(val))
    .or_insert_with(|| "poneyland".to_string());

assert!(table
    .find(hasher(&"poneyland"), |x| x == "poneyland")
    .is_some());

pub fn and_modify(self, f: impl FnOnce(&mut T)) -> Self

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

Examples

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
    .entry(
        hasher(&"poneyland"),
        |&(x, _)| x == "poneyland",
        |(k, _)| hasher(&k),
    )
    .and_modify(|(_, v)| *v += 1)
    .or_insert(("poneyland", 42));
assert_eq!(
    table.find(hasher(&"poneyland"), |&(k, _)| k == "poneyland"),
    Some(&("poneyland", 42))
);

table
    .entry(
        hasher(&"poneyland"),
        |&(x, _)| x == "poneyland",
        |(k, _)| hasher(&k),
    )
    .and_modify(|(_, v)| *v += 1)
    .or_insert(("poneyland", 42));
assert_eq!(
    table.find(hasher(&"poneyland"), |&(k, _)| k == "poneyland"),
    Some(&("poneyland", 43))
);

Trait Implementations

impl<T: Debug, A: Allocator> Debug for Entry<'_, T, 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: 32 bytes

Size for each variant:

• Occupied: 24 bytes
• Vacant: 24 bytes