Struct HashContext 

pub struct HashContext<T> {
    pub hash: fn(&T, &mut dyn Hasher),
}

A context providing a custom hash function.

When used with WithContext, implements Hash by dispatching through the stored hash function. The function receives a &mut dyn Hasher so it can work with any hasher type.

Examples

use context_trait::{WithContext, HashContext};
use std::collections::hash_map::DefaultHasher;
use std::hash::{Hash, Hasher};

let ctx = HashContext { hash: |v: &(i32, i32), h: &mut dyn Hasher| {
    h.write_i32(v.0);
}};
let a = WithContext { inner: (1, 100), ctx };

let mut hasher = DefaultHasher::new();
a.hash(&mut hasher);
let hash_a = hasher.finish();

let b = WithContext { inner: (1, 200), ctx };
let mut hasher = DefaultHasher::new();
b.hash(&mut hasher);
let hash_b = hasher.finish();

// Same hash because only first element is hashed
assert_eq!(hash_a, hash_b);

Fields

hash: fn(&T, &mut dyn Hasher)

The hash function.

Trait Implementations

impl<T> Clone for HashContext<T>

fn clone(&self) -> HashContext<T>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T> Debug for HashContext<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<T> Copy for HashContext<T>