# 1.7.0[−][src]Struct core::hash::BuildHasherDefault

    pub struct BuildHasherDefault<H>(_);

Used to create a default `BuildHasher` instance for types that implement `Hasher` and `Default`.

`BuildHasherDefault<H>` can be used when a type `H` implements `Hasher` and `Default`, and you need a corresponding `BuildHasher` instance, but none is defined.

Any `BuildHasherDefault` is zero-sized. It can be created with `default`. When using `BuildHasherDefault` with `HashMap` or `HashSet`, this doesn't need to be done, since they implement appropriate `Default` instances themselves.

# Examples

Using `BuildHasherDefault` to specify a custom `BuildHasher` for `HashMap`:

    use std::collections::HashMap;
    use std::hash::{BuildHasherDefault, Hasher};

    #[derive(Default)]
    struct MyHasher;

    impl Hasher for MyHasher {
        fn write(&mut self, bytes: &[u8]) {
            // Your hashing algorithm goes here!
           unimplemented!()
        }

        fn finish(&self) -> u64 {
            // Your hashing algorithm goes here!
            unimplemented!()
        }
    }

    type MyBuildHasher = BuildHasherDefault<MyHasher>;

    let hash_map = HashMap::<u32, u32, MyBuildHasher>::default();Run

## Trait Implementations

### `impl<H> PartialEq<BuildHasherDefault<H>> for BuildHasherDefault<H>`
1.29.0
[src]

#### `fn eq(&self, _other: &BuildHasherDefault<H>) -> bool`[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

#### `
#[must_use]
fn ne(&self, other: &Rhs) -> bool`
1.0.0
[src]

This method tests for `!=`.

### `impl<H> Eq for BuildHasherDefault<H>`
1.29.0
[src]

### `impl<H> Clone for BuildHasherDefault<H>`[src]

#### `fn clone(&self) -> BuildHasherDefault<H>`[src]

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, source: &Self)`
1.0.0
[src]

Performs copy-assignment from `source`. Read more

### `impl<H> Default for BuildHasherDefault<H>`[src]

#### `fn default() -> BuildHasherDefault<H>`[src]

Returns the "default value" for a type. Read more

### `impl<H: Default + Hasher> BuildHasher for BuildHasherDefault<H>`[src]

#### `type Hasher = H`

Type of the hasher that will be created.

#### `fn build_hasher(&self) -> H`[src]

Creates a new hasher. Read more

### `impl<H> Debug for BuildHasherDefault<H>`
1.9.0
[src]

#### `fn fmt(&self, f: &mut Formatter) -> Result`[src]

Formats the value using the given formatter. Read more

## Auto Trait Implementations

### `impl<H> Send for BuildHasherDefault<H> where
H: Send,`

### `impl<H> Sync for BuildHasherDefault<H> where
H: Sync,`

## Blanket Implementations

### `impl<T, U> Into for T where
U: From<T>,` [src]

#### `fn into(Self) -> U`[src]

Performs the conversion.

### `impl<T> From for T`[src]

#### `fn from(T) -> T`[src]

Performs the conversion.

### `impl<T, U> TryInto for T where
U: TryFrom<T>,` [src]

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

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

#### `fn try_into(Self) -> Result<U, <U as TryFrom<T>>::Error>`[src]

🔬 This is a nightly-only experimental API. (`try_from` #33417)

Performs the conversion.

### `impl<T, U> TryFrom for T where
T: From<U>,` [src]

#### `type Error = !`

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

#### `fn try_from(U) -> Result<T, <T as TryFrom<U>>::Error>`[src]

🔬 This is a nightly-only experimental API. (`try_from` #33417)

Performs the conversion.

### `impl<T> Borrow for T where
T: ?Sized,` [src]

#### `fn borrow(&Self) -> &T`[src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut for T where
T: ?Sized,` [src]

#### `fn borrow_mut(&mut Self) -> &mut T`[src]

Mutably borrows from an owned value. Read more

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `fn get_type_id(&Self) -> TypeId`[src]

🔬 This is a nightly-only experimental API. (`get_type_id` #27745)

this method will likely be replaced by an associated static

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

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