78 lines
2.5 KiB
Rust
78 lines
2.5 KiB
Rust
//! See [`Output`]
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use crate::SyntaxKind;
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/// Output of the parser -- a DFS traversal of a concrete syntax tree.
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///
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/// Use the [`Output::iter`] method to iterate over traversal steps and consume
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/// a syntax tree.
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///
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/// In a sense, this is just a sequence of [`SyntaxKind`]-colored parenthesis
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/// interspersed into the original [`crate::Input`]. The output is fundamentally
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/// coordinated with the input and `n_input_tokens` refers to the number of
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/// times [`crate::Input::push`] was called.
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#[derive(Default)]
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pub struct Output {
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/// 32-bit encoding of events. If LSB is zero, then that's an index into the
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/// error vector. Otherwise, it's one of the thee other variants, with data encoded as
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///
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/// |16 bit kind|8 bit n_input_tokens|4 bit tag|4 bit leftover|
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///
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event: Vec<u32>,
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error: Vec<String>,
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}
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#[derive(Debug)]
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pub enum Step<'a> {
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Token { kind: SyntaxKind, n_input_tokens: u8 },
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Enter { kind: SyntaxKind },
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Exit,
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Error { msg: &'a str },
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}
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impl Output {
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pub fn iter(&self) -> impl Iterator<Item = Step<'_>> {
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self.event.iter().map(|&event| {
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if event & 0b1 == 0 {
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return Step::Error { msg: self.error[(event as usize) >> 1].as_str() };
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}
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let tag = ((event & 0x0000_00F0) >> 4) as u8;
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match tag {
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0 => {
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let kind: SyntaxKind = (((event & 0xFFFF_0000) >> 16) as u16).into();
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let n_input_tokens = ((event & 0x0000_FF00) >> 8) as u8;
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Step::Token { kind, n_input_tokens }
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}
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1 => {
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let kind: SyntaxKind = (((event & 0xFFFF_0000) >> 16) as u16).into();
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Step::Enter { kind }
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}
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2 => Step::Exit,
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_ => unreachable!(),
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}
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})
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}
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pub(crate) fn token(&mut self, kind: SyntaxKind, n_tokens: u8) {
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let e = ((kind as u16 as u32) << 16) | ((n_tokens as u32) << 8) | (0 << 4) | 1;
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self.event.push(e)
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}
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pub(crate) fn enter_node(&mut self, kind: SyntaxKind) {
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let e = ((kind as u16 as u32) << 16) | (1 << 4) | 1;
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self.event.push(e)
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}
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pub(crate) fn leave_node(&mut self) {
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let e = 2 << 4 | 1;
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self.event.push(e)
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}
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pub(crate) fn error(&mut self, error: String) {
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let idx = self.error.len();
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self.error.push(error);
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let e = (idx as u32) << 1;
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self.event.push(e);
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}
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}
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