Protocol std::hash::Hashable

Types that can be hashed.

The hash method can be implemented directly or an automatic implementation can be mixed in using the DefaultHashable protocol.

Examples

A default implementation

struct FancyI32 { a: i32 }

impl FancyI32 {
   use std::hash::{DefaultHashable, Hasher};

   mixin<H: Hasher<H>> DefaultHashable<FancyI32, H>;
}

use std::hash::hash_of;

let x = FancyI32 { a: 1 };
let y = FancyI32 { a: 1 };
let z = FancyI32 { a: 2 };

assert_eq!(x.hash_of(), y.hash_of());
assert_ne!(x.hash_of(), z.hash_of());
Run this example

A custom implementation

struct Foo { a: i32, b: &[u8], extra: u64 }

impl Foo {
    use std::hash::Hasher;
    fn hash<H: Hasher<H>>(self: &Foo, hasher: &mut H) {
        self.a.hash(hasher);
        self.b.hash(hasher);
        // Skip the `extra`, if two instances of `Foo` are otherwise equal,
        // but differ in the value of `extra`, they will hash to the same value.
    }
}

use std::hash::hash_of;

let v1 = Foo { a: 1, b: "foo", extra: 0 };
let v2 = Foo { a: 1, b: "foo", extra: 1 };
let v3 = Foo { a: 1, b: "bar", extra: 0 };

assert_eq!(v1.hash_of(), v2.hash_of());
assert_ne!(v1.hash_of(), v3.hash_of());
Run this example

Required methods

• fn hash(a: &Self, hasher: &mut H)

  source

  Update hasher state with the contents of this object.

  See Hashable for details.