Struct Context 

pub struct Context { /* private fields */ }

External information required to encode or decode a contextual value.

The context can record whether the current field is present, the length of an array field, and child contexts for array elements. This supports protocol fields described as Optional X or Array of X, where the required information is known from the enclosing packet or data structure.

A Context does not consume or produce any bytes. The enclosing codec must derive it from already-known protocol state and pass it to ContextualCodec.

Examples

use mcproto_types::contextual::Context;

let has_signature = true; // Derived from an earlier packet field.
let context = Context::new(has_signature);
assert!(context.is_present());
assert!(!Context::absent().is_present());

Implementations

impl Context

pub const PRESENT: Self

Context for a field that is present on the wire.

pub const ABSENT: Self

Context for a field that occupies zero bytes on the wire.

pub const fn new(present: bool) -> Self

Creates a context from a presence condition determined by the enclosing protocol structure.

pub const fn present() -> Self

Creates context for a field that is present on the wire.

pub const fn absent() -> Self

Creates context for a field that occupies zero bytes on the wire.

pub const fn for_array_length(length: usize) -> Self

Creates context containing the number of elements in an array field.

pub fn with_array_length(self, length: usize) -> Self

Adds an array length to this context, preserving any presence state.

pub fn with_element_contexts( self, contexts: impl IntoIterator<Item = Context>, ) -> Self

Adds a child context for each array element.

When child contexts are not supplied, an array passes its own context to every element. Supplying child contexts is required when different elements have different contextual metadata or when arrays are nested.

pub const fn presence(&self) -> Option<bool>

Returns the explicitly supplied presence state, if one exists.

pub const fn array_length(&self) -> Option<usize>

Returns the contextual array length, if one exists.

pub const fn is_present(&self) -> bool

Returns whether the contextual field is present on the wire.

Trait Implementations

impl Clone for Context

fn clone(&self) -> Context

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Context

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

Formats the value using the given formatter.

impl Eq for Context

impl Hash for Context

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 PartialEq for Context

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Context