Struct Node 

pub struct Node {
    pub first: u64,
    pub a: u32,
    pub b: u32,
    pub op: Op,
    pub flags: u8,
}

One node. Twenty four bytes, and everything the matcher needs to decide what to do with it.

The FIRST set and the nullable bit live in here rather than in two arrays beside it. They used to be parallel tables, on the theory that the filter could read eight bytes of FIRST and skip the node entirely, and that theory was wrong in the case that matters. A node that survives the filter is loaded immediately afterwards, and surviving is the common case: the filter is there to cut the thirty six alternatives of Statement down, and the one that matches still has to be walked. So the old layout paid three cache lines on every node it did not reject and saved two on every node it did, and the walk visits far more of the first kind.

Fields

first: u64

What this node can start with, as a set of token keys. A superset, always.

a: u32

b: u32

op: Op

flags: u8

Per op, plus NULLABLE, which every op can carry.

Implementations

impl Node

pub const RESERVED: u8

On an Identifier node: the keyword check is dropped, so any word matches.

This is the whole of ReservedIdentifierMatcher. It is worth knowing that upstream applies it to the rule named ReservedKeyword, so a grammar rule that reads ColLabel <- ReservedKeyword / ... does not test for a reserved word, it accepts any word at all. Reading the grammar text alone would get that backwards.

pub const NULLABLE: u8

This node can match without consuming a token, so its FIRST set says nothing about whether it applies and the filter has to let it through.

pub fn can_start(self, key: u64) -> bool

Whether a node could possibly begin with this token.

False means it cannot, and that is the only answer the caller may act on. True means try it. A nullable node always answers true.

pub fn children(self) -> &'static [u32]

The children of a sequence or a choice.

Trait Implementations

impl Clone for Node

fn clone(&self) -> Node

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Node

impl Debug for Node

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

Formats the value using the given formatter.

impl Eq for Node

impl PartialEq for Node

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Node