# Struct hashbrown::hash_map::RawEntryBuilder

source · [−]

    pub struct RawEntryBuilder<'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` docs for usage examples.

## Examples

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

    let mut map = HashMap::new();
    map.extend([(1, 10), (2, 20), (3, 30)]);

    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()
    }

    for k in 0..6 {
        let hash = compute_hash(map.hasher(), &k);
        let v = map.get(&k).cloned();
        let kv = v.as_ref().map(|v| (&k, v));

        println!("Key: {} and value: {:?}", k, v);
        let builder: RawEntryBuilder<_, _, _> = map.raw_entry();
        assert_eq!(builder.from_key(&k), kv);
        assert_eq!(map.raw_entry().from_hash(hash, |q| *q == k), kv);
        assert_eq!(map.raw_entry().from_key_hashed_nocheck(hash, &k), kv);
    }

## Implementations

source

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

source

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

Access an immutable entry by key.

##### Examples

    use hashbrown::HashMap;

    let map: HashMap<&str, u32> = [("a", 100), ("b", 200)].into();
    let key = "a";
    assert_eq!(map.raw_entry().from_key(&key), Some((&"a", &100)));

source

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

Access an immutable entry by a key and its hash.

##### Examples

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

    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 map: HashMap<&str, u32> = [("a", 100), ("b", 200)].into();
    let key = "a";
    let hash = compute_hash(map.hasher(), &key);
    assert_eq!(map.raw_entry().from_key_hashed_nocheck(hash, &key), Some((&"a", &100)));

source

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

Access an immutable entry by hash and matching function.

##### Examples

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

    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 map: HashMap<&str, u32> = [("a", 100), ("b", 200)].into();
    let key = "a";
    let hash = compute_hash(map.hasher(), &key);
    assert_eq!(map.raw_entry().from_hash(hash, |k| k == &key), Some((&"a", &100)));

## Trait Implementations

source

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

source

#### 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 RawEntryBuilder<'a, K, V, S, A> where
A: RefUnwindSafe,
K: RefUnwindSafe,
S: RefUnwindSafe,
V: RefUnwindSafe,

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

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

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

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

## Blanket Implementations

source

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

source

#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more

source

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

const: unstable · source

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

Immutably borrows from an owned value. Read more

source

### 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

source

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

const: unstable · source

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

Returns the argument unchanged.

source

### 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.

source

### 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.

source

### 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.