Struct How

pub struct How<T: ?Sized, H = DefaultHasher, S = Cell<u64>> { /* private fields */ }

A wrapper for storing hash results to avoid running costly hash functions multiple times without modifying the value

Examples

let mut x = How::new_default("foo".to_owned());

assert!(! How::is_hashed(&x));
HashSet::new().insert(&x);
assert!(How::is_hashed(&x));

How::make_mut(&mut x).push('!');
assert!(! How::is_hashed(&x));
assert_eq!(*x, "foo!");

---

Due to the inability of the stored hashcode to replicate the action of T::hash, it is not possible to implement Borrow<T>

Implementations

impl<T> How<T>

pub fn new_default(value: T) -> Self

new, but use DefaultHasher

impl<T, H, S: Default> How<T, H, S>

pub fn new(value: T) -> Self

New a wrapped value

impl<T, H, S> How<T, H, S>

pub fn into_inner(this: Self) -> T

Consume self into wrapped value

impl<T: ?Sized, H, S: HashStorer> How<T, H, S>

pub fn make_mut(this: &mut Self) -> &mut T

Get mutable and clear hash cache

pub fn hash_code(this: &Self) -> Option<u64>

Get hash cache status

pub fn is_hashed(this: &Self) -> bool

Get hash cache status is cached, like How::hash_code(&value).is_some()

impl<T, H, S> How<T, H, S>

where T: ?Sized + Hash, H: Default + Hasher, S: HashStorer,

pub fn make_hash(this: &Self) -> u64

Get or init hash cache

Trait Implementations

impl<T: ?Sized, H, S> AsMut<How<T, H, S>> for How<T, H, S>

fn as_mut(&mut self) -> &mut Self

Converts this type into a mutable reference of the (usually inferred) input type.

impl<T: ?Sized, H, S: HashStorer> AsMut<T> for How<T, H, S>

fn as_mut(&mut self) -> &mut T

Converts this type into a mutable reference of the (usually inferred) input type.

impl<T: ?Sized, H, S> AsRef<How<T, H, S>> for How<T, H, S>

fn as_ref(&self) -> &Self

Converts this type into a shared reference of the (usually inferred) input type.

impl<T: ?Sized, H, S> AsRef<T> for How<T, H, S>

fn as_ref(&self) -> &T

Converts this type into a shared reference of the (usually inferred) input type.

impl<T, Q, H, S> Borrow<Borrowed<Q, H, S>> for How<T, H, S>

where T: ?Sized + Borrow<Q>, Q: ?Sized,

fn borrow(&self) -> &Borrowed<Q, H, S>

Immutably borrows from an owned value.

impl<T, Q, H, S> BorrowMut<Borrowed<Q, H, S>> for How<T, H, S>

where T: ?Sized + BorrowMut<Q>, Q: ?Sized,

fn borrow_mut(&mut self) -> &mut Borrowed<Q, H, S>

Mutably borrows from an owned value.

impl<T: ?Sized + Clone, H, S: Clone> Clone for How<T, H, S>

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T: ?Sized + Debug, H, S: Debug> Debug for How<T, H, S>

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

Formats the value using the given formatter.

impl<T, H, S> Default for How<T, H, S>

where T: Default, S: Default,

fn default() -> Self

Returns the “default value” for a type.

impl<T: ?Sized, H, S> Deref for How<T, H, S>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<T, H, S> DerefMut for How<T, H, S>

where T: ?Sized + Hash, H: Hasher + Default, S: HashStorer,

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

impl<T, H, S> From<T> for How<T, H, S>

where H: Hasher + Default, S: HashStorer + Default,

fn from(value: T) -> Self

Converts to this type from the input type.

impl<T, IH, S> Hash for How<T, IH, S>

where T: ?Sized + Hash, IH: Hasher + Default, S: HashStorer,

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T: ?Sized + Ord, H, S: HashStorer> Ord for How<T, H, S>

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<T: ?Sized + PartialEq, H, S> PartialEq<T> for How<T, H, S>

fn eq(&self, other: &T) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: ?Sized + PartialEq, H, S: HashStorer> PartialEq for How<T, H, S>

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: ?Sized + PartialOrd, H, S> PartialOrd<T> for How<T, H, S>

fn partial_cmp(&self, other: &T) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T: ?Sized + PartialOrd, H, S: HashStorer> PartialOrd for How<T, H, S>

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T: ?Sized + Eq, H, S: HashStorer> Eq for How<T, H, S>