pub struct RawVacantEntryMut<'a, K, V, S, A = Global>
where A: Allocator,
{ /* private fields */ }
Expand description

A view into a vacant entry in a HashMap. It is part of the RawEntryMut enum.

Examples

use core::hash::{BuildHasher, Hash};
use hashbrown::hash_map::{HashMap, RawEntryMut, RawVacantEntryMut};

let mut map = HashMap::<&str, i32>::new();

fn compute_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
    use core::hash::Hasher;
    let mut state = hash_builder.build_hasher();
    key.hash(&mut state);
    state.finish()
}

let raw_v: RawVacantEntryMut<_, _, _> = match map.raw_entry_mut().from_key(&"a") {
    RawEntryMut::Vacant(view) => view,
    RawEntryMut::Occupied(_) => unreachable!(),
};
raw_v.insert("a", 10);
assert!(map[&"a"] == 10 && map.len() == 1);

// Nonexistent key (insert and update)
let hash = compute_hash(map.hasher(), &"b");
match map.raw_entry_mut().from_key_hashed_nocheck(hash, &"b") {
    RawEntryMut::Occupied(_) => unreachable!(),
    RawEntryMut::Vacant(view) => {
        let (k, value) = view.insert("b", 2);
        assert_eq!((*k, *value), ("b", 2));
        *value = 20;
    }
}
assert!(map[&"b"] == 20 && map.len() == 2);

let hash = compute_hash(map.hasher(), &"c");
match map.raw_entry_mut().from_hash(hash, |q| *q == "c") {
    RawEntryMut::Occupied(_) => unreachable!(),
    RawEntryMut::Vacant(view) => {
        assert_eq!(view.insert("c", 30), (&mut "c", &mut 30));
    }
}
assert!(map[&"c"] == 30 && map.len() == 3);

Implementations§

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impl<'a, K, V, S, A> RawVacantEntryMut<'a, K, V, S, A>
where A: Allocator,

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pub fn insert(self, key: K, value: V) -> (&'a mut K, &'a mut V)
where K: Hash, S: BuildHasher,

Sets the value of the entry with the VacantEntry’s key, and returns a mutable reference to it.

Examples
use hashbrown::hash_map::{HashMap, RawEntryMut};

let mut map: HashMap<&str, u32> = [("a", 100), ("b", 200)].into();

match map.raw_entry_mut().from_key(&"c") {
    RawEntryMut::Occupied(_) => panic!(),
    RawEntryMut::Vacant(v) => assert_eq!(v.insert("c", 300), (&mut "c", &mut 300)),
}

assert_eq!(map[&"c"], 300);
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pub fn insert_hashed_nocheck( self, hash: u64, key: K, value: V ) -> (&'a mut K, &'a mut V)
where K: Hash, S: BuildHasher,

Sets the value of the entry with the VacantEntry’s key, and returns a mutable reference to it.

Examples
use core::hash::{BuildHasher, Hash};
use hashbrown::hash_map::{HashMap, RawEntryMut};

fn compute_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
    use core::hash::Hasher;
    let mut state = hash_builder.build_hasher();
    key.hash(&mut state);
    state.finish()
}

let mut map: HashMap<&str, u32> = [("a", 100), ("b", 200)].into();
let key = "c";
let hash = compute_hash(map.hasher(), &key);

match map.raw_entry_mut().from_key_hashed_nocheck(hash, &key) {
    RawEntryMut::Occupied(_) => panic!(),
    RawEntryMut::Vacant(v) => assert_eq!(
        v.insert_hashed_nocheck(hash, key, 300),
        (&mut "c", &mut 300)
    ),
}

assert_eq!(map[&"c"], 300);
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pub fn insert_with_hasher<H>( self, hash: u64, key: K, value: V, hasher: H ) -> (&'a mut K, &'a mut V)
where H: Fn(&K) -> u64,

Set the value of an entry with a custom hasher function.

Examples
use core::hash::{BuildHasher, Hash};
use hashbrown::hash_map::{HashMap, RawEntryMut};

fn make_hasher<K, S>(hash_builder: &S) -> impl Fn(&K) -> u64 + '_
where
    K: Hash + ?Sized,
    S: BuildHasher,
{
    move |key: &K| {
        use core::hash::Hasher;
        let mut state = hash_builder.build_hasher();
        key.hash(&mut state);
        state.finish()
    }
}

let mut map: HashMap<&str, u32> = HashMap::new();
let key = "a";
let hash_builder = map.hasher().clone();
let hash = make_hasher(&hash_builder)(&key);

match map.raw_entry_mut().from_hash(hash, |q| q == &key) {
    RawEntryMut::Occupied(_) => panic!(),
    RawEntryMut::Vacant(v) => assert_eq!(
        v.insert_with_hasher(hash, key, 100, make_hasher(&hash_builder)),
        (&mut "a", &mut 100)
    ),
}
map.extend([("b", 200), ("c", 300), ("d", 400), ("e", 500), ("f", 600)]);
assert_eq!(map[&"a"], 100);

Trait Implementations§

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impl<K, V, S, A> Debug for RawVacantEntryMut<'_, K, V, S, A>
where A: Allocator,

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

Formats the value using the given formatter. Read more

Auto Trait Implementations§

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impl<'a, K, V, S, A> RefUnwindSafe for RawVacantEntryMut<'a, K, V, S, A>

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impl<'a, K, V, S, A> Send for RawVacantEntryMut<'a, K, V, S, A>
where A: Send, K: Send, S: Sync, V: Send,

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impl<'a, K, V, S, A> Sync for RawVacantEntryMut<'a, K, V, S, A>
where A: Sync, K: Sync, S: Sync, V: Sync,

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impl<'a, K, V, S, A> Unpin for RawVacantEntryMut<'a, K, V, S, A>

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impl<'a, K, V, S, A = Global> !UnwindSafe for RawVacantEntryMut<'a, K, V, S, A>

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T, U> AsBindGroupShaderType<U> for T
where U: ShaderType, &'a T: for<'a> Into<U>,

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fn as_bind_group_shader_type(&self, _images: &RenderAssets<Image>) -> U

Return the T ShaderType for self. When used in AsBindGroup derives, it is safe to assume that all images in self exist.
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> Downcast<T> for T

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fn downcast(&self) -> &T

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impl<T> Downcast for T
where T: Any,

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Convert Box<dyn Trait> (where Trait: Downcast) to Box<dyn Any>. Box<dyn Any> can then be further downcast into Box<ConcreteType> where ConcreteType implements Trait.
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Convert Rc<Trait> (where Trait: Downcast) to Rc<Any>. Rc<Any> can then be further downcast into Rc<ConcreteType> where ConcreteType implements Trait.
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fn as_any(&self) -> &(dyn Any + 'static)

Convert &Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &Any’s vtable from &Trait’s.
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fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)

Convert &mut Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &mut Any’s vtable from &mut Trait’s.
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impl<T> DowncastSync for T
where T: Any + Send + Sync,

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fn into_any_arc(self: Arc<T>) -> Arc<dyn Any + Send + Sync>

Convert Arc<Trait> (where Trait: Downcast) to Arc<Any>. Arc<Any> can then be further downcast into Arc<ConcreteType> where ConcreteType implements Trait.
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<S> FromSample<S> for S

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fn from_sample_(s: S) -> S

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for T
where U: From<T>,

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Calls U::from(self).

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The type returned in the event of a conversion error.
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Performs the conversion.
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type Error = <U as TryFrom<T>>::Error

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Performs the conversion.
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fn upcast(&self) -> Option<&T>

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where S: Into<Dispatch>,

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