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De-magic number parser::Output encoding

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This commit is contained in:
Lukas Wirth 2023-02-03 11:47:33 +01:00
parent bfe82cda48
commit dab685dd87
1 changed files with 36 additions and 13 deletions
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49
crates/parser/src/output.rs
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@ -31,47 +31,70 @@ pub enum Step<'a> {
} }
impl Output { impl Output {
const EVENT_MASK: u32 = 0b1;
const TAG_MASK: u32 = 0x0000_00F0;
const N_INPUT_TOKEN_MASK: u32 = 0x0000_FF00;
const KIND_MASK: u32 = 0xFFFF_0000;
const ERROR_SHIFT: u32 = Self::EVENT_MASK.trailing_ones();
const TAG_SHIFT: u32 = Self::TAG_MASK.trailing_zeros();
const N_INPUT_TOKEN_SHIFT: u32 = Self::N_INPUT_TOKEN_MASK.trailing_zeros();
const KIND_SHIFT: u32 = Self::KIND_MASK.trailing_zeros();
const TOKEN_EVENT: u8 = 0;
const ENTER_EVENT: u8 = 1;
const EXIT_EVENT: u8 = 2;
pub fn iter(&self) -> impl Iterator<Item = Step<'_>> { pub fn iter(&self) -> impl Iterator<Item = Step<'_>> {
self.event.iter().map(|&event| { self.event.iter().map(|&event| {
if event & 0b1 == 0 { if event & Self::EVENT_MASK == 0 {
return Step::Error { msg: self.error[(event as usize) >> 1].as_str() }; return Step::Error {
msg: self.error[(event as usize) >> Self::ERROR_SHIFT].as_str(),
};
} }
let tag = ((event & 0x0000_00F0) >> 4) as u8; let tag = ((event & Self::TAG_MASK) >> Self::TAG_SHIFT) as u8;
match tag { match tag {
0 => { Self::TOKEN_EVENT => {
let kind: SyntaxKind = (((event & 0xFFFF_0000) >> 16) as u16).into(); let kind: SyntaxKind =
let n_input_tokens = ((event & 0x0000_FF00) >> 8) as u8; (((event & Self::KIND_MASK) >> Self::KIND_SHIFT) as u16).into();
let n_input_tokens =
((event & Self::N_INPUT_TOKEN_MASK) >> Self::N_INPUT_TOKEN_SHIFT) as u8;
Step::Token { kind, n_input_tokens } Step::Token { kind, n_input_tokens }
} }
1 => { Self::ENTER_EVENT => {
let kind: SyntaxKind = (((event & 0xFFFF_0000) >> 16) as u16).into(); let kind: SyntaxKind =
(((event & Self::KIND_MASK) >> Self::KIND_SHIFT) as u16).into();
Step::Enter { kind } Step::Enter { kind }
} }
2 => Step::Exit, Self::EXIT_EVENT => Step::Exit,
_ => unreachable!(), _ => unreachable!(),
} }
}) })
} }
pub(crate) fn token(&mut self, kind: SyntaxKind, n_tokens: u8) { pub(crate) fn token(&mut self, kind: SyntaxKind, n_tokens: u8) {
let e = ((kind as u16 as u32) << 16) | ((n_tokens as u32) << 8) | 1; let e = ((kind as u16 as u32) << Self::KIND_SHIFT)
| ((n_tokens as u32) << Self::N_INPUT_TOKEN_SHIFT)
| Self::EVENT_MASK;
self.event.push(e) self.event.push(e)
} }
pub(crate) fn enter_node(&mut self, kind: SyntaxKind) { pub(crate) fn enter_node(&mut self, kind: SyntaxKind) {
let e = ((kind as u16 as u32) << 16) | (1 << 4) | 1; let e = ((kind as u16 as u32) << Self::KIND_SHIFT)
| ((Self::ENTER_EVENT as u32) << Self::TAG_SHIFT)
| Self::EVENT_MASK;
self.event.push(e) self.event.push(e)
} }
pub(crate) fn leave_node(&mut self) { pub(crate) fn leave_node(&mut self) {
let e = 2 << 4 | 1; let e = (Self::EXIT_EVENT as u32) << Self::TAG_SHIFT | Self::EVENT_MASK;
self.event.push(e) self.event.push(e)
} }
pub(crate) fn error(&mut self, error: String) { pub(crate) fn error(&mut self, error: String) {
let idx = self.error.len(); let idx = self.error.len();
self.error.push(error); self.error.push(error);
let e = (idx as u32) << 1; let e = (idx as u32) << Self::ERROR_SHIFT;
self.event.push(e); self.event.push(e);
} }
} }