Struct hashbrown::rustc_entry::RustcOccupiedEntry

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pub struct RustcOccupiedEntry<'a, K, V, A = Global>where
    A: Allocator + Clone,{
    key: Option<K>,
    elem: Bucket<(K, V)>,
    table: &'a mut RawTable<(K, V), A>,
}

Expand description

A view into an occupied entry in a HashMap. It is part of the RustcEntry enum.

Fields§

§key: Option<K>§elem: Bucket<(K, V)>§table: &'a mut RawTable<(K, V), A>

Implementations§

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impl<'a, K, V, A: Allocator + Clone> RustcOccupiedEntry<'a, K, V, A>

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pub fn key(&self) -> &K

Gets a reference to the key in the entry.

Examples

use hashbrown::HashMap;

let mut map: HashMap<&str, u32> = HashMap::new();
map.rustc_entry("poneyland").or_insert(12);
assert_eq!(map.rustc_entry("poneyland").key(), &"poneyland");

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pub fn remove_entry(self) -> (K, V)

Take the ownership of the key and value from the map.

Examples

use hashbrown::HashMap;
use hashbrown::hash_map::RustcEntry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.rustc_entry("poneyland").or_insert(12);

if let RustcEntry::Occupied(o) = map.rustc_entry("poneyland") {
    // We delete the entry from the map.
    o.remove_entry();
}

assert_eq!(map.contains_key("poneyland"), false);

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pub fn get(&self) -> &V

Gets a reference to the value in the entry.

Examples

use hashbrown::HashMap;
use hashbrown::hash_map::RustcEntry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.rustc_entry("poneyland").or_insert(12);

if let RustcEntry::Occupied(o) = map.rustc_entry("poneyland") {
    assert_eq!(o.get(), &12);
}

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

Gets a mutable reference to the value in the entry.

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

Examples

use hashbrown::HashMap;
use hashbrown::hash_map::RustcEntry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.rustc_entry("poneyland").or_insert(12);

assert_eq!(map["poneyland"], 12);
if let RustcEntry::Occupied(mut o) = map.rustc_entry("poneyland") {
    *o.get_mut() += 10;
    assert_eq!(*o.get(), 22);

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

assert_eq!(map["poneyland"], 24);

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pub fn into_mut(self) -> &'a mut V

Converts the RustcOccupiedEntry into a mutable reference to the value in the entry with a lifetime bound to the map itself.

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

Examples

use hashbrown::HashMap;
use hashbrown::hash_map::RustcEntry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.rustc_entry("poneyland").or_insert(12);

assert_eq!(map["poneyland"], 12);
if let RustcEntry::Occupied(o) = map.rustc_entry("poneyland") {
    *o.into_mut() += 10;
}

assert_eq!(map["poneyland"], 22);

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pub fn insert(&mut self, value: V) -> V

Sets the value of the entry, and returns the entry’s old value.

Examples

use hashbrown::HashMap;
use hashbrown::hash_map::RustcEntry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.rustc_entry("poneyland").or_insert(12);

if let RustcEntry::Occupied(mut o) = map.rustc_entry("poneyland") {
    assert_eq!(o.insert(15), 12);
}

assert_eq!(map["poneyland"], 15);

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pub fn remove(self) -> V

Takes the value out of the entry, and returns it.

Examples

use hashbrown::HashMap;
use hashbrown::hash_map::RustcEntry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.rustc_entry("poneyland").or_insert(12);

if let RustcEntry::Occupied(o) = map.rustc_entry("poneyland") {
    assert_eq!(o.remove(), 12);
}

assert_eq!(map.contains_key("poneyland"), false);

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pub fn replace_entry(self, value: V) -> (K, V)

Replaces the entry, returning the old key and value. The new key in the hash map will be the key used to create this entry.

Examples

use hashbrown::hash_map::{RustcEntry, HashMap};
use std::rc::Rc;

let mut map: HashMap<Rc<String>, u32> = HashMap::new();
map.insert(Rc::new("Stringthing".to_string()), 15);

let my_key = Rc::new("Stringthing".to_string());

if let RustcEntry::Occupied(entry) = map.rustc_entry(my_key) {
    // Also replace the key with a handle to our other key.
    let (old_key, old_value): (Rc<String>, u32) = entry.replace_entry(16);
}

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pub fn replace_key(self) -> K

Replaces the key in the hash map with the key used to create this entry.

Examples

use hashbrown::hash_map::{RustcEntry, HashMap};
use std::rc::Rc;

let mut map: HashMap<Rc<String>, u32> = HashMap::new();
let mut known_strings: Vec<Rc<String>> = Vec::new();

// Initialise known strings, run program, etc.

reclaim_memory(&mut map, &known_strings);

fn reclaim_memory(map: &mut HashMap<Rc<String>, u32>, known_strings: &[Rc<String>] ) {
    for s in known_strings {
        if let RustcEntry::Occupied(entry) = map.rustc_entry(s.clone()) {
            // Replaces the entry's key with our version of it in `known_strings`.
            entry.replace_key();
        }
    }
}