Enum Entry

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

Available on crate features dep_hashbrown and alloc only.

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)) -> Entry<'a, T, A>

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, A> Debug for Entry<'_, T, A>

where T: Debug, A: Allocator,

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

Formats the value using the given formatter.