Struct Optional 

#[repr(transparent)]
pub struct Optional<T>(pub Option<T>);

A context-controlled optional value of protocol type T.

Optional<T> stores an Option<T>, but it does not encode a presence marker. When the supplied Context is present, the inner T is encoded using its ContextualCodec implementation. When the context is absent, the value occupies zero bytes.

The caller must derive the context from the enclosing packet or data structure. This type therefore implements ContextualCodec, not TypeCodec. A value/context mismatch is reported as an encoding error; it is never silently discarded.

Examples

use mcproto_types::{ContextualCodec, TypeCodec, basic::UnsignedByte};
use mcproto_types::contextual::{Context, Optional};

let value = Optional::some(UnsignedByte(0xab));
let mut encoded = Vec::new();
value.encode_with_context(&mut encoded, &Context::present())?;
assert_eq!(encoded, [0xab]);

let mut input = encoded.as_slice();
assert_eq!(
    Optional::<UnsignedByte>::decode_with_context(&mut input, &Context::present())?,
    value,
);

Tuple Fields

0: Option<T>

The optional value held in memory.

Implementations

impl<T> Optional<T>

pub const fn some(value: T) -> Self

Creates an optional value that is present.

pub const fn none() -> Self

Creates an optional value that is absent.

pub const fn is_some(&self) -> bool

Returns whether this wrapper contains a value.

pub const fn is_none(&self) -> bool

Returns whether this wrapper contains no value.

pub const fn as_ref(&self) -> Optional<&T>

Returns the contained value by reference, if present.

pub fn into_option(self) -> Option<T>

Extracts the wrapped Option<T>.

Trait Implementations

impl<T: Clone> Clone for Optional<T>

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

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T> ContextualCodec for Optional<T>

where T: ContextualCodec,

fn encode_with_context( &self, writer: &mut impl Write, context: &Context, ) -> Result<(), CodecError>

Encodes this value using context supplied by its enclosing structure.

fn decode_with_context( reader: &mut impl Read, context: &Context, ) -> Result<Self, CodecError>

Decodes this value using context supplied by its enclosing structure.

impl<T: Debug> Debug for Optional<T>

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

Formats the value using the given formatter.

impl<T: Default> Default for Optional<T>

fn default() -> Optional<T>

Returns the “default value” for a type.

impl<T: Eq> Eq for Optional<T>

impl<T> From<Option<T>> for Optional<T>

fn from(value: Option<T>) -> Self

Converts to this type from the input type.

impl<T> From<Optional<T>> for Option<T>

fn from(value: Optional<T>) -> Self

Converts to this type from the input type.

impl<T> From<Optional<T>> for PrefixedOptional<T>

fn from(value: Optional<T>) -> Self

Converts to this type from the input type.

impl<T: Hash> Hash for Optional<T>

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: PartialEq> PartialEq for Optional<T>

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

Equality operator ==.

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

Inequality operator !=.

impl<T: PartialEq> StructuralPartialEq for Optional<T>