Struct wnf::OpaqueData

pub struct OpaqueData { /* private fields */ }

A placeholder for state data whose content is irrelevant

This type can be “read” from any state regardless of the size of the state data. It doesn’t contain the actual data but just their size, which can be obtained via the OpaqueData::size method. This is useful on different occasions, for instance:

• If you want to query the size of state data without querying the actual data:

let state = OwnedState::<u32>::create_temporary()?;
state.set(&42)?;

assert_eq!(state.as_state().cast::<OpaqueData>().get()?.size(), 4);

// Less efficient alternative:
assert_eq!(state.as_state().cast::<[u8]>().get_boxed()?.len(), 4);

• If you want to check if a state can be read without querying its actual data:

// Here we could have used any type `T: NoUninit` in place of `u32`
let state = OwnedState::<u32>::create_temporary()?;
state.set(&42)?;

let can_read = state.cast::<OpaqueData>().get().is_ok();

assert!(can_read);

Another use case is reading the change stamp of a state without knowing what the actual data look like, but that is already implemented in OwnedState::change_stamp.

Implementations

impl OpaqueData

pub const fn size(self) -> usize

Returns the size in bytes of this OpaqueData

Trait Implementations

impl Clone for OpaqueData

fn clone(&self) -> OpaqueData

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for OpaqueData

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

Formats the value using the given formatter.

impl Hash for OpaqueData

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 Ord for OpaqueData

fn cmp(&self, other: &OpaqueData) -> 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 + PartialOrd,

Restrict a value to a certain interval.

impl PartialEq for OpaqueData

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

This method tests for self and other values to be equal, and is used by ==.

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

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

impl PartialOrd for OpaqueData

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

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

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

This method tests less than (for self and other) and is used by the < operator.

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

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

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

This method tests greater than (for self and other) and is used by the > operator.

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

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

impl Copy for OpaqueData

impl Eq for OpaqueData

impl Read<OpaqueData> for OpaqueData

impl StructuralPartialEq for OpaqueData