# 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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