# Struct hashbrown::hash_map::RawEntryBuilderMut

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    pub struct RawEntryBuilderMut<'a, K, V, S, A: Allocator + Clone = Global> { /* private fields */ }

Expand description

A builder for computing where in a `HashMap` a key-value pair would be stored.

See the `HashMap::raw_entry_mut` docs for usage examples.

## Examples

    use hashbrown::hash_map::{RawEntryBuilderMut, RawEntryMut::Vacant, RawEntryMut::Occupied};
    use hashbrown::HashMap;
    use core::hash::{BuildHasher, Hash};

    let mut map = HashMap::new();
    map.extend([(1, 11), (2, 12), (3, 13), (4, 14), (5, 15), (6, 16)]);
    assert_eq!(map.len(), 6);

    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 builder: RawEntryBuilderMut<_, _, _> = map.raw_entry_mut();

    // Existing key
    match builder.from_key(&6) {
        Vacant(_) => unreachable!(),
        Occupied(view) => assert_eq!(view.get(), &16),
    }

    for key in 0..12 {
        let hash = compute_hash(map.hasher(), &key);
        let value = map.get(&key).cloned();
        let key_value = value.as_ref().map(|v| (&key, v));

        println!("Key: {} and value: {:?}", key, value);

        match map.raw_entry_mut().from_key(&key) {
            Occupied(mut o) => assert_eq!(Some(o.get_key_value()), key_value),
            Vacant(_) => assert_eq!(value, None),
        }
        match map.raw_entry_mut().from_key_hashed_nocheck(hash, &key) {
            Occupied(mut o) => assert_eq!(Some(o.get_key_value()), key_value),
            Vacant(_) => assert_eq!(value, None),
        }
        match map.raw_entry_mut().from_hash(hash, |q| *q == key) {
            Occupied(mut o) => assert_eq!(Some(o.get_key_value()), key_value),
            Vacant(_) => assert_eq!(value, None),
        }
    }

    assert_eq!(map.len(), 6);

## Implementations

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### impl<'a, K, V, S, A: Allocator + Clone> RawEntryBuilderMut<'a, K, V, S, A>

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#### pub fn from_key<Q: ?Sized>(self, k: &Q) -> RawEntryMut<'a, K, V, S, A> where
S: BuildHasher,
K: Borrow<Q>,
Q: Hash + Eq,

Creates a `RawEntryMut` from the given key.

##### Examples

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

    let mut map: HashMap<&str, u32> = HashMap::new();
    let key = "a";
    let entry: RawEntryMut<&str, u32, _> = map.raw_entry_mut().from_key(&key);
    entry.insert(key, 100);
    assert_eq!(map[&"a"], 100);

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#### pub fn from_key_hashed_nocheck<Q: ?Sized>(
self,
hash: u64,
k: &Q
) -> RawEntryMut<'a, K, V, S, A> where
K: Borrow<Q>,
Q: Eq,

Creates a `RawEntryMut` from the given key and its hash.

##### 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> = HashMap::new();
    let key = "a";
    let hash = compute_hash(map.hasher(), &key);
    let entry: RawEntryMut<&str, u32, _> = map.raw_entry_mut().from_key_hashed_nocheck(hash, &key);
    entry.insert(key, 100);
    assert_eq!(map[&"a"], 100);

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### impl<'a, K, V, S, A: Allocator + Clone> RawEntryBuilderMut<'a, K, V, S, A>

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#### pub fn from_hash<F>(self, hash: u64, is_match: F) -> RawEntryMut<'a, K, V, S, A> where
for<'b> F: FnMut(&'b K) -> bool,

Creates a `RawEntryMut` from the given hash and matching function.

##### 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> = HashMap::new();
    let key = "a";
    let hash = compute_hash(map.hasher(), &key);
    let entry: RawEntryMut<&str, u32, _> = map.raw_entry_mut().from_hash(hash, |k| k == &key);
    entry.insert(key, 100);
    assert_eq!(map[&"a"], 100);

## Trait Implementations

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### impl<K, V, S, A: Allocator + Clone> Debug for RawEntryBuilderMut<'_, K, V, S, A>

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

Formats the value using the given formatter. Read more

## Auto Trait Implementations

### impl<'a, K, V, S, A> RefUnwindSafe for RawEntryBuilderMut<'a, K, V, S, A> where
A: RefUnwindSafe,
K: RefUnwindSafe,
S: RefUnwindSafe,
V: RefUnwindSafe,

### impl<'a, K, V, S, A> Send for RawEntryBuilderMut<'a, K, V, S, A> where
A: Send,
K: Send,
S: Send,
V: Send,

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

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

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

## Blanket Implementations

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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> Borrow<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more

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### impl<T> BorrowMut<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more

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### impl<T> From<T> for T

const: unstable · source

#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T where
U: From<T>,

const: unstable · source

#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T, U> TryFrom<U> for T where
U: Into<T>,

#### type Error = Infallible

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.

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### impl<T, U> TryInto<U> for T where
U: TryFrom<T>,

#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.