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| -rw-r--r-- | src/construct/character_reference.rs | 237 |
1 files changed, 237 insertions, 0 deletions
diff --git a/src/construct/character_reference.rs b/src/construct/character_reference.rs new file mode 100644 index 0000000..27275d5 --- /dev/null +++ b/src/construct/character_reference.rs @@ -0,0 +1,237 @@ +//! Character references are a construct that occurs in the string and text +//! content types. +//! +//! They’re formed with the following BNF: +//! +//! ```bnf +//! character_reference ::= '&' (numeric | named) ';' +//! +//! numeric ::= '#' (hexadecimal | decimal) +//! ; Note: Limit of `6` imposed as all bigger numbers are invalid: +//! hexadecimal ::= ('x' | 'X') 1*6(ascii_hexdigit) +//! ; Note: Limit of `7` imposed as all bigger numbers are invalid: +//! decimal ::= 1*7(ascii_digit) +//! ; Note: Limit of `31` imposed by `CounterClockwiseContourIntegral`: +//! ; Note: Limited to any known named character reference (see `constants.rs`) +//! named ::= 1*31(ascii_alphanumeric) +//! ``` +//! +//! Like much of markdown, there are no “invalid” character references. +//! However, for security reasons, several numeric character references parse +//! fine but are not rendered as their corresponding character and they are +//! instead replaced by a U+FFFD REPLACEMENT CHARACTER (`�`). +//! See [`decode_numeric_character_reference`][decode_numeric] for more info. +//! +//! To escape ASCII punctuation characters, use the terser +//! [character escape][character_escape] construct instead (as in, `\&`). +//! +//! Character references in markdown are not the same as character references +//! in HTML. +//! Notably, HTML allows several character references without a closing +//! semicolon. +//! See [*§ 13.2.5.72 Character reference state* in the HTML spec][html] for more info. +//! +//! Character references are parsed insensitive to casing. +//! The casing of hexadecimal numeric character references has no effect. +//! The casing of named character references does not matter when parsing them, +//! but does affect whether they match. +//! Depending on the name, one or more cases are allowed, such as that `AMP` +//! and `amp` are both allowed but other cases are not. +//! See [`CHARACTER_REFERENCE_NAMES`][character_reference_names] for which +//! names match. +//! +//! ## References +//! +//! * [`character-reference.js` in `micromark`](https://github.com/micromark/micromark/blob/main/packages/micromark-core-commonmark/dev/lib/character-reference.js) +//! * [*§ 2.5 Entity and numeric character references* in `CommonMark`](https://spec.commonmark.org/0.30/#entity-and-numeric-character-references) +//! +//! [character_escape]: crate::construct::character_reference +//! [decode_numeric]: crate::util::decode_numeric_character_reference +//! [character_reference_names]: crate::constant::CHARACTER_REFERENCE_NAMES +//! [html]: https://html.spec.whatwg.org/multipage/parsing.html#character-reference-state +//! +//! <!-- To do: link `string`, `text` --> + +use crate::constant::{ + CHARACTER_REFERENCE_DECIMAL_SIZE_MAX, CHARACTER_REFERENCE_HEXADECIMAL_SIZE_MAX, + CHARACTER_REFERENCE_NAMED_SIZE_MAX, CHARACTER_REFERENCE_NAMES, +}; +use crate::tokenizer::{Code, State, StateFnResult, TokenType, Tokenizer}; + +/// Kind of a character reference. +#[derive(Debug, Clone)] +pub enum Kind { + /// Numeric decimal character reference (`	`). + Decimal, + /// Numeric hexadecimal character reference (`{`). + Hexadecimal, + /// Named character reference (`&`). + Named, +} + +/// State needed to parse character references. +#[derive(Debug, Clone)] +struct Info { + /// All parsed characters. + buffer: Vec<char>, + /// Kind of character reference. + kind: Kind, +} + +/// Start of a character reference. +/// +/// ```markdown +/// a|&b +/// a|{b +/// a|	b +/// ``` +pub fn start(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult { + match code { + Code::Char('&') => { + tokenizer.enter(TokenType::CharacterReference); + tokenizer.enter(TokenType::CharacterReferenceMarker); + tokenizer.consume(code); + tokenizer.exit(TokenType::CharacterReferenceMarker); + (State::Fn(Box::new(open)), None) + } + _ => (State::Nok, None), + } +} + +/// Inside a character reference, after `&`, before `#` for numeric references +/// or an alphanumeric for named references. +/// +/// ```markdown +/// a&|amp;b +/// a&|#123;b +/// a&|#x9;b +/// ``` +fn open(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult { + if let Code::Char('#') = code { + tokenizer.enter(TokenType::CharacterReferenceMarkerNumeric); + tokenizer.consume(code); + tokenizer.exit(TokenType::CharacterReferenceMarkerNumeric); + (State::Fn(Box::new(numeric)), None) + } else { + tokenizer.enter(TokenType::CharacterReferenceValue); + value( + tokenizer, + code, + Info { + buffer: vec![], + kind: Kind::Named, + }, + ) + } +} + +/// Inside a numeric character reference, right before `x` for hexadecimals, +/// or a digit for decimals. +/// +/// ```markdown +/// a&#|123;b +/// a&#|x9;b +/// ``` +fn numeric(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult { + match code { + Code::Char(char) if char == 'x' || char == 'X' => { + tokenizer.enter(TokenType::CharacterReferenceMarkerHexadecimal); + tokenizer.consume(code); + tokenizer.exit(TokenType::CharacterReferenceMarkerHexadecimal); + tokenizer.enter(TokenType::CharacterReferenceValue); + + ( + State::Fn(Box::new(|tokenizer, code| { + value( + tokenizer, + code, + Info { + buffer: vec![], + kind: Kind::Hexadecimal, + }, + ) + })), + None, + ) + } + _ => { + tokenizer.enter(TokenType::CharacterReferenceValue); + + value( + tokenizer, + code, + Info { + buffer: vec![], + kind: Kind::Decimal, + }, + ) + } + } +} + +/// Inside a character reference value, after the markers (`&#x`, `&#`, or +/// `&`) that define its kind, but before the `;`. +/// The character reference kind defines what and how many characters are +/// allowed. +/// +/// ```markdown +/// a&a|mp;b +/// a|23;b +/// a&#x|9;b +/// ``` +fn value(tokenizer: &mut Tokenizer, code: Code, info: Info) -> StateFnResult { + match code { + Code::Char(';') if !info.buffer.is_empty() => { + tokenizer.exit(TokenType::CharacterReferenceValue); + let value = info.buffer.iter().collect::<String>(); + + if let Kind::Named = info.kind { + if !CHARACTER_REFERENCE_NAMES.contains(&value.as_str()) { + return (State::Nok, Some(vec![code])); + } + } + + tokenizer.enter(TokenType::CharacterReferenceMarkerSemi); + tokenizer.consume(code); + tokenizer.exit(TokenType::CharacterReferenceMarkerSemi); + tokenizer.exit(TokenType::CharacterReference); + (State::Ok, None) + } + Code::Char(char) => { + let len = info.buffer.len(); + + let cont = match info.kind { + Kind::Hexadecimal + if char.is_ascii_hexdigit() + && len < CHARACTER_REFERENCE_HEXADECIMAL_SIZE_MAX => + { + true + } + Kind::Decimal + if char.is_ascii_digit() && len < CHARACTER_REFERENCE_DECIMAL_SIZE_MAX => + { + true + } + Kind::Named + if char.is_ascii_alphanumeric() && len < CHARACTER_REFERENCE_NAMED_SIZE_MAX => + { + true + } + _ => false, + }; + + if cont { + let mut clone = info; + clone.buffer.push(char); + tokenizer.consume(code); + ( + State::Fn(Box::new(|tokenizer, code| value(tokenizer, code, clone))), + None, + ) + } else { + (State::Nok, None) + } + } + _ => (State::Nok, None), + } +} |