Struct ProcessingStack 

pub struct ProcessingStack<I> { /* private fields */ }

The chain of remote context URLs currently being processed.

This is the specification’s remote contexts array. It serves two purposes: spotting a context that includes itself, and bounding the length of a remote context chain at MAX_REMOTE_CONTEXTS. Whether it is empty also tells the algorithm whether the context being processed came from a remote document, which is what decides if its @base entry applies.

Implemented as an immutable singly-linked list behind Arcs, so the copy each recursive call receives is a pointer bump rather than a clone of the chain.

Every copy of a stack also shares one record of the contexts dereferenced since the stack was created, which is how one run of the algorithm honours step 5.2.4: “If context was previously dereferenced, then the processor MUST NOT do a further dereference”. The chain is per branch of the recursion; the record is per run.

Implementations

impl<I> ProcessingStack<I>

pub fn new() -> Self

Creates an empty stack, meaning no remote context is being processed, with an empty record of dereferenced contexts.

pub fn is_empty(&self) -> bool

Checks whether no remote context has been entered, i.e. the context being processed is not itself remote.

pub fn len(&self) -> usize

Returns the number of remote contexts on the stack.

Walks the chain, so this is linear in the stack depth.

pub fn cycle(&self, url: &I) -> bool

where I: PartialEq,

Checks whether url is already on the stack, meaning entering it would close a loop.

pub fn push(&mut self, url: I) -> bool

where I: PartialEq,

Pushes url onto the stack, unless it is already there.

Returns true when the URL was added, and false when it was already on the stack and nothing changed. What false means is version-dependent: JSON-LD 1.0 treats it as a recursive context inclusion error, while 1.1 skips the context only while validating a scoped context (step 5.2.2) and otherwise processes it again, which is Self::enter.

pub fn enter(&mut self, url: I)

Pushes url onto the stack whether or not it is already there.

This is step 5.2.3’s “add context to remote contexts”: under JSON-LD 1.1 a context named again outside scoped-context validation is processed again, and each processing counts toward MAX_REMOTE_CONTEXTS.

pub fn dereferenced(&self, url: &I) -> Option<Arc<Context>>

where I: Eq + Hash,

The @context of the document dereferenced for url earlier in this run, if there was one (step 5.2.4).

pub fn remember_dereferenced(&self, url: I, context: Arc<Context>)

where I: Eq + Hash,

Records the @context dereferenced for url, so the rest of this run reuses it instead of dereferencing url again (step 5.2.4).

Trait Implementations

impl<I> Clone for ProcessingStack<I>

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<I> Default for ProcessingStack<I>

fn default() -> Self

Returns the “default value” for a type.