src/tools/rust-analyzer/crates/parser/src/output.rs

   1 //! See [`Output`]
   2
   3 use crate::SyntaxKind;
   4
   5 /// Output of the parser -- a DFS traversal of a concrete syntax tree.
   6 ///
   7 /// Use the [`Output::iter`] method to iterate over traversal steps and consume
   8 /// a syntax tree.
   9 ///
  10 /// In a sense, this is just a sequence of [`SyntaxKind`]-colored parenthesis
  11 /// interspersed into the original [`crate::Input`]. The output is fundamentally
  12 /// coordinated with the input and `n_input_tokens` refers to the number of
  13 /// times [`crate::Input::push`] was called.
  14 #[derive(Default)]
  15 pub struct Output {
  16     /// 32-bit encoding of events. If LSB is zero, then that's an index into the
  17     /// error vector. Otherwise, it's one of the thee other variants, with data encoded as
  18     ///
  19     ///     |16 bit kind|8 bit n_input_tokens|4 bit tag|4 bit leftover|
  20     ///
  21     event: Vec<u32>,
  22     error: Vec<String>,
  23 }
  24
  25 #[derive(Debug)]
  26 pub enum Step<'a> {
  27     Token { kind: SyntaxKind, n_input_tokens: u8 },
  28     Enter { kind: SyntaxKind },
  29     Exit,
  30     Error { msg: &'a str },
  31 }
  32
  33 impl Output {
  34     pub fn iter(&self) -> impl Iterator<Item = Step<'_>> {
  35         self.event.iter().map(|&event| {
  36             if event & 0b1 == 0 {
  37                 return Step::Error { msg: self.error[(event as usize) >> 1].as_str() };
  38             }
  39             let tag = ((event & 0x0000_00F0) >> 4) as u8;
  40             match tag {
  41                 0 => {
  42                     let kind: SyntaxKind = (((event & 0xFFFF_0000) >> 16) as u16).into();
  43                     let n_input_tokens = ((event & 0x0000_FF00) >> 8) as u8;
  44                     Step::Token { kind, n_input_tokens }
  45                 }
  46                 1 => {
  47                     let kind: SyntaxKind = (((event & 0xFFFF_0000) >> 16) as u16).into();
  48                     Step::Enter { kind }
  49                 }
  50                 2 => Step::Exit,
  51                 _ => unreachable!(),
  52             }
  53         })
  54     }
  55
  56     pub(crate) fn token(&mut self, kind: SyntaxKind, n_tokens: u8) {
  57         let e = ((kind as u16 as u32) << 16) | ((n_tokens as u32) << 8) | 1;
  58         self.event.push(e)
  59     }
  60
  61     pub(crate) fn enter_node(&mut self, kind: SyntaxKind) {
  62         let e = ((kind as u16 as u32) << 16) | (1 << 4) | 1;
  63         self.event.push(e)
  64     }
  65
  66     pub(crate) fn leave_node(&mut self) {
  67         let e = 2 << 4 | 1;
  68         self.event.push(e)
  69     }
  70
  71     pub(crate) fn error(&mut self, error: String) {
  72         let idx = self.error.len();
  73         self.error.push(error);
  74         let e = (idx as u32) << 1;
  75         self.event.push(e);
  76     }
  77 }