Struct hashbrown::hash_table::VacantEntry

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

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

Examples

use ahash::AHasher;
use hashbrown::hash_table::{Entry, HashTable, VacantEntry};
use std::hash::{BuildHasher, BuildHasherDefault};

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

let entry_v: VacantEntry<_, _> = match table.entry(hasher(&"a"), |&x| x == "a", hasher) {
    Entry::Vacant(view) => view,
    Entry::Occupied(_) => unreachable!(),
};
entry_v.insert("a");
assert!(table.find(hasher(&"a"), |&x| x == "a").is_some() && table.len() == 1);

// Nonexistent key (insert)
match table.entry(hasher(&"b"), |&x| x == "b", hasher) {
    Entry::Vacant(view) => {
        view.insert("b");
    }
    Entry::Occupied(_) => unreachable!(),
}
assert!(table.find(hasher(&"b"), |&x| x == "b").is_some() && table.len() == 2);

Implementations

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

where A: Allocator,

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

Inserts a new element into the table with the hash that was used to obtain the VacantEntry.

An OccupiedEntry is returned for the newly inserted element.

Examples

use ahash::AHasher;
use hashbrown::hash_table::Entry;
use hashbrown::HashTable;
use std::hash::{BuildHasher, BuildHasherDefault};

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

if let Entry::Vacant(o) = table.entry(hasher(&"poneyland"), |&x| x == "poneyland", hasher) {
    o.insert("poneyland");
}
assert_eq!(
    table.find(hasher(&"poneyland"), |&x| x == "poneyland"),
    Some(&"poneyland")
);

pub fn into_table(self) -> &'a mut HashTable<T, A>

Converts the VacantEntry into a mutable reference to the underlying table.

Trait Implementations

impl<T: Debug, A: Allocator> Debug for VacantEntry<'_, 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: 24 bytes