core::hash::BuildHasherDefault - Rust
Description: API documentation for the Rust `BuildHasherDefault` struct in crate `core`.
Keywords: rust, rustlang, rust-lang, BuildHasherDefault

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

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

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

Formats the value using the given formatter.

### `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`

Creates a new hasher. Read more

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

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

Returns a copy of the value. Read more

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

Performs copy-assignment from `source`. Read more

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

#### `fn default() -> BuildHasherDefault<H>`

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

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result
+
  Collapse/expand all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)