113 lines
3.9 KiB
Rust
113 lines
3.9 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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FloatSplit { ends_in_dot: bool },
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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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const EVENT_MASK: u32 = 0b1;
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const TAG_MASK: u32 = 0x0000_00F0;
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const N_INPUT_TOKEN_MASK: u32 = 0x0000_FF00;
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const KIND_MASK: u32 = 0xFFFF_0000;
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const ERROR_SHIFT: u32 = Self::EVENT_MASK.trailing_ones();
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const TAG_SHIFT: u32 = Self::TAG_MASK.trailing_zeros();
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const N_INPUT_TOKEN_SHIFT: u32 = Self::N_INPUT_TOKEN_MASK.trailing_zeros();
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const KIND_SHIFT: u32 = Self::KIND_MASK.trailing_zeros();
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const TOKEN_EVENT: u8 = 0;
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const ENTER_EVENT: u8 = 1;
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const EXIT_EVENT: u8 = 2;
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const SPLIT_EVENT: u8 = 3;
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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 & Self::EVENT_MASK == 0 {
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return Step::Error {
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msg: self.error[(event as usize) >> Self::ERROR_SHIFT].as_str(),
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};
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}
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let tag = ((event & Self::TAG_MASK) >> Self::TAG_SHIFT) as u8;
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match tag {
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Self::TOKEN_EVENT => {
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let kind: SyntaxKind =
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(((event & Self::KIND_MASK) >> Self::KIND_SHIFT) as u16).into();
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let n_input_tokens =
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((event & Self::N_INPUT_TOKEN_MASK) >> Self::N_INPUT_TOKEN_SHIFT) as u8;
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Step::Token { kind, n_input_tokens }
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}
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Self::ENTER_EVENT => {
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let kind: SyntaxKind =
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(((event & Self::KIND_MASK) >> Self::KIND_SHIFT) as u16).into();
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Step::Enter { kind }
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}
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Self::EXIT_EVENT => Step::Exit,
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Self::SPLIT_EVENT => {
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Step::FloatSplit { ends_in_dot: event & Self::N_INPUT_TOKEN_MASK != 0 }
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}
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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) << Self::KIND_SHIFT)
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| ((n_tokens as u32) << Self::N_INPUT_TOKEN_SHIFT)
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| Self::EVENT_MASK;
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self.event.push(e)
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}
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pub(crate) fn float_split_hack(&mut self, ends_in_dot: bool) {
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let e = (Self::SPLIT_EVENT as u32) << Self::TAG_SHIFT
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| ((ends_in_dot as u32) << Self::N_INPUT_TOKEN_SHIFT)
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| Self::EVENT_MASK;
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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) << Self::KIND_SHIFT)
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| ((Self::ENTER_EVENT as u32) << Self::TAG_SHIFT)
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| Self::EVENT_MASK;
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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 = (Self::EXIT_EVENT as u32) << Self::TAG_SHIFT | Self::EVENT_MASK;
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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) << Self::ERROR_SHIFT;
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self.event.push(e);
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}
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}
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