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add ArbitraryVariableMachine 
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‎crates/oxide/src/extractor/arbitrary_variable_machine.rs

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use crate::cursor;
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use crate::extractor::bracket_stack::BracketStack;
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use crate::extractor::css_variable_machine::CssVariableMachine;
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use crate::extractor::machine::{Machine, MachineState};
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use crate::extractor::string_machine::StringMachine;
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/// Extracts arbitrary variables including the parens.
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///
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/// E.g.:
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///
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/// ```text
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/// (--my-value)
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/// ^^^^^^^^^^^^
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///
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/// bg-red-500/(--my-opacity)
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/// ^^^^^^^^^^^^^^
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/// ```
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#[derive(Debug, Default)]
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pub struct ArbitraryVariableMachine {
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/// Start position of the arbitrary variable
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start_pos: usize,
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/// Track brackets to ensure they are balanced
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bracket_stack: BracketStack,
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/// Current state of the machine
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state: State,
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string_machine: StringMachine,
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css_variable_machine: CssVariableMachine,
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}
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#[derive(Debug, Default)]
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enum State {
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#[default]
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Idle,
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/// Currently parsing the inside of the arbitrary variable
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///
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/// ```text
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/// (--my-opacity)
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/// ^^^^^^^^^^^^
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/// ```
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Parsing,
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/// Currently parsing the fallback of the arbitrary variable
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///
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/// ```text
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/// (--my-opacity,50%)
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/// ^^^^
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/// ```
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ParsingFallback,
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}
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impl Machine for ArbitraryVariableMachine {
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#[inline(always)]
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fn reset(&mut self) {
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self.start_pos = 0;
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self.state = State::Idle;
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self.bracket_stack.reset();
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}
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#[inline]
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fn next(&mut self, cursor: &mut cursor::Cursor<'_>) -> MachineState {
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let class_curr = CLASS_TABLE[cursor.curr as usize];
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let len = cursor.input.len();
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match self.state {
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State::Idle => match class_curr {
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// Arbitrary variables start with `(` followed by a CSS variable
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//
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// E.g.: `(--my-variable)`
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// ^^
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//
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Class::OpenParen => match CLASS_TABLE[cursor.next as usize] {
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Class::Dash => {
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self.start_pos = cursor.pos;
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self.state = State::Parsing;
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cursor.advance();
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self.next(cursor)
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}
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_ => MachineState::Idle,
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},
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// Everything else, is not a valid start of the arbitrary variable. But the next
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// character might be a valid start for a new utility.
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_ => MachineState::Idle,
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},
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State::Parsing => match self.css_variable_machine.next(cursor) {
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MachineState::Idle => self.restart(),
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MachineState::Done(_) => match CLASS_TABLE[cursor.next as usize] {
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// A CSS variable followed by a `,` means that there is a fallback
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//
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// E.g.: `(--my-color,red)`
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// ^
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Class::Comma => {
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self.state = State::ParsingFallback;
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cursor.advance_by(2); // Skip the `,`
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self.next(cursor)
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}
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// End of the CSS variable
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//
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// E.g.: `(--my-color)`
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// ^
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_ => {
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cursor.advance();
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match CLASS_TABLE[cursor.curr as usize] {
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// End of an arbitrary variable, must be followed by `)`
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Class::CloseParen => self.done(self.start_pos, cursor),
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// Invalid arbitrary variable, not ending at `)`
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_ => self.restart(),
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}
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}
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},
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},
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State::ParsingFallback => {
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while cursor.pos < len {
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match CLASS_TABLE[cursor.curr as usize] {
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Class::Escape => match CLASS_TABLE[cursor.next as usize] {
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// An escaped whitespace character is not allowed
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//
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// E.g.: `(--my-\ color)`
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// ^^
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Class::Whitespace => return self.restart(),
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// An escaped character, skip the next character, resume after
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//
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// E.g.: `(--my-\#color)`
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// ^^
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_ => cursor.advance_by(2),
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},
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Class::OpenParen | Class::OpenBracket | Class::OpenCurly => {
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if !self.bracket_stack.push(cursor.curr) {
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return self.restart();
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}
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cursor.advance();
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}
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Class::CloseParen | Class::CloseBracket | Class::CloseCurly
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if !self.bracket_stack.is_empty() =>
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{
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if !self.bracket_stack.pop(cursor.curr) {
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return self.restart();
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}
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cursor.advance();
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}
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// End of an arbitrary variable
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Class::CloseParen => return self.done(self.start_pos, cursor),
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// Start of a string
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Class::Quote => match self.string_machine.next(cursor) {
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MachineState::Idle => return self.restart(),
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MachineState::Done(_) => {
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self.state = State::ParsingFallback;
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cursor.advance();
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return self.next(cursor);
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}
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},
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// A `:` inside of a fallback value is only valid inside of brackets or inside of a
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// string. Everywhere else, it's invalid.
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//
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// E.g.: `(--foo,bar:baz)`
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// ^ Not valid
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//
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// E.g.: `(--url,url(https://example.com))`
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// ^ Valid
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//
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// E.g.: `(--my-content:'a:b:c:')`
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// ^ ^ ^ Valid
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Class::Colon if self.bracket_stack.is_empty() => return self.restart(),
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// Any kind of whitespace is not allowed
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Class::Whitespace => return self.restart(),
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// Everything else is valid
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_ => cursor.advance(),
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};
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}
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self.restart()
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}
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}
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}
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}
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#[derive(Clone, Copy, PartialEq)]
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enum Class {
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/// `'a'..='z'`
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AlphaLower,
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/// `'A'..='Z'`
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AlphaUpper,
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/// `@`
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At,
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// `:`
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Colon,
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/// `,`
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Comma,
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/// `-`
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Dash,
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/// `:`
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Dot,
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/// `\\`
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Escape,
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/// `0x00`
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End,
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/// `'0'..='9'`
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Number,
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/// `[`
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OpenBracket,
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/// `]`
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CloseBracket,
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/// `(`
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OpenParen,
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/// `)`
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CloseParen,
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/// `{`
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OpenCurly,
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/// `}`
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CloseCurly,
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/// ', ", or `
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Quote,
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/// _
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Underscore,
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/// Whitespace characters: ' ', '\t', '\n', '\r', '\x0C'
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Whitespace,
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/// Anything else
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Other,
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}
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const CLASS_TABLE: [Class; 256] = {
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let mut table = [Class::Other; 256];
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macro_rules! set {
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($class:expr, $($byte:expr),+ $(,)?) => {
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$(table[$byte as usize] = $class;)+
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};
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}
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macro_rules! set_range {
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($class:expr, $start:literal ..= $end:literal) => {
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let mut i = $start;
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while i <= $end {
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table[i as usize] = $class;
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i += 1;
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}
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};
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}
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set!(Class::At, b'@');
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set!(Class::Underscore, b'_');
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set!(Class::Dash, b'-');
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set!(Class::Whitespace, b' ', b'\t', b'\n', b'\r', b'\x0C');
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set!(Class::Comma, b',');
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set!(Class::Escape, b'\\');
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set!(Class::OpenBracket, b'[');
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set!(Class::CloseBracket, b']');
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set!(Class::OpenParen, b'(');
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set!(Class::CloseParen, b')');
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set!(Class::OpenCurly, b'{');
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set!(Class::CloseCurly, b'}');
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set!(Class::Dot, b'.');
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set!(Class::Colon, b':');
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set!(Class::Quote, b'"', b'\'', b'`');
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set_range!(Class::AlphaLower, b'a'..=b'z');
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set_range!(Class::AlphaUpper, b'A'..=b'Z');
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set_range!(Class::Number, b'0'..=b'9');
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set!(Class::End, 0x00);
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table
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};
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#[cfg(test)]
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mod tests {
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use super::ArbitraryVariableMachine;
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use crate::extractor::machine::Machine;
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#[test]
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#[ignore]
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fn test_arbitrary_variable_machine_performance() {
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let input = r#"<div class="(--foo) (--my-color,red,blue) (--my-img,url('https://example.com?q=(][)'))"></div>"#.repeat(100);
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ArbitraryVariableMachine::test_throughput(100_000, &input);
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ArbitraryVariableMachine::test_duration_once(&input);
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todo!()
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}
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#[test]
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fn test_arbitrary_variable_extraction() {
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for (input, expected) in [
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// Simple utility
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("(--foo)", vec!["(--foo)"]),
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// With dashes
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("(--my-color)", vec!["(--my-color)"]),
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// With a fallback
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("(--my-color,red,blue)", vec!["(--my-color,red,blue)"]),
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// With a fallback containing a string with unbalanced brackets
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(
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"(--my-img,url('https://example.com?q=(][)'))",
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vec!["(--my-img,url('https://example.com?q=(][)'))"],
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),
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// --------------------------------------------------------
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// Exceptions:
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// Arbitrary variable must start with a CSS variable
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(r"(bar)", vec![]),
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// Arbitrary variables must be valid CSS variables
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(r"(--my-\ color)", vec![]),
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(r"(--my#color)", vec![]),
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// Fallbacks cannot have spaces
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(r"(--my-color, red)", vec![]),
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// Fallbacks cannot have escaped spaces
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(r"(--my-color,\ red)", vec![]),
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// Variables must have at least one character after the `--`
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(r"(--)", vec![]),
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(r"(--,red)", vec![]),
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] {
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assert_eq!(ArbitraryVariableMachine::test_extract_all(input), expected);
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}
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}
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}

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