Struct NodeId 

pub struct NodeId(/* private fields */);

A stage-local node identity.

Why NonZeroU32 rather than a reserved sentinel

Both give Option<NodeId> a 4-byte layout, which is the requirement (an L2 op holding several optional child references pays 4 bytes per slot, not 8). NonZeroU32 is chosen because it makes “no such node” unrepresentable inside NodeId itself: with a reserved-sentinel u32 every consumer must remember that NodeId(0) is not a node, and nothing stops one from constructing it. The niche is also stable-Rust: reserving a range on a plain u32 needs rustc_layout_scalar_valid_range, which is unstable.

The cost is that the raw value and the index differ by one, so the conversion is explicit and single-sourced: NodeId::from_index and NodeId::index. Nothing else may do the arithmetic.

Implementations

impl NodeId

pub const FIRST: NodeId

The first id a stage mints, equivalent to from_index(0).

pub const fn from_index(index: u32) -> Option<NodeId>

The id for a 0-based node index.

Returns None only for u32::MAX, whose successor does not fit — a stage with more than u32::MAX - 1 nodes in one artifact, which no real input reaches. Callers minting ids in sequence should propagate the None rather than unwrap it: exhaustion is a diagnostic, not a panic.

pub const fn index(self) -> u32

The 0-based index this id denotes.

This is the dense-side-table subscript, and the only place the off-by-one between the niche representation and the index lives.

pub const fn index_usize(self) -> usize

The 0-based index as a usize, for indexing a dense table.

pub const fn to_raw(self) -> NonZeroU32

The niche representation, for a folio page that serializes ids.

pub const fn from_raw(raw: NonZeroU32) -> NodeId

Rebuild an id from its niche representation.

pub const fn next(self) -> Option<NodeId>

The next id in sequence, or None at exhaustion.

Trait Implementations

impl Clone for NodeId

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for NodeId

impl Debug for NodeId

Prints the index, not the niche value, because the index is what folio pages and diagnostics show: NodeId(0) is the first node.

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

Formats the value using the given formatter.

impl Display for NodeId

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

Formats the value using the given formatter.

impl Eq for NodeId

impl Hash for NodeId

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 NodeId

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.

fn clamp_to<R>(self, range: R) -> Self

where Self: Sized, R: ClampBounds<Self>,

🔬This is a nightly-only experimental API. (clamp_to)

Restrict a value to a certain range.

impl PartialEq for NodeId

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

Equality operator ==.

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

Inequality operator !=.

impl PartialOrd for NodeId

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 StructuralPartialEq for NodeId

impl WitnessKeyed for NodeId

fn to_witness_key(&self) -> WitnessKey

This key, erased.

fn from_witness_key(key: &WitnessKey) -> Option<Self>

The typed key key erases, or None when key has another shape.