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authorLibravatar Titus Wormer <tituswormer@gmail.com>2022-06-14 13:47:32 +0200
committerLibravatar Titus Wormer <tituswormer@gmail.com>2022-06-14 13:55:03 +0200
commita1ce43e428754084474a7ecf88ae6debf88b9164 (patch)
treea1df0ec515f624431d3e398f7d24e7b411c18e6e /src/util.rs
parentc587aee9512119e61918bfbe81c3cca3de7e70aa (diff)
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-//! Some utilities helpful when parsing and compiling markdown.
-
-use crate::constant::{CHARACTER_REFERENCE_NAMES, CHARACTER_REFERENCE_VALUES};
-use crate::tokenizer::{Code, Event, EventType};
-
-/// Encode dangerous html characters.
-///
-/// This ensures that certain characters which have special meaning in HTML are
-/// dealt with.
-/// Technically, we can skip `>` and `"` in many cases, but CM includes them.
-///
-/// This behavior is not explained in prose in `CommonMark` but can be inferred
-/// from the input/output test cases.
-///
-/// ## Examples
-///
-/// ```rust ignore
-/// use micromark::util::encode;
-///
-/// assert_eq!(encode("I <3 🦀"), "I &lt;3 🦀");
-/// ```
-///
-/// ## References
-///
-/// * [`micromark-util-encode` in `micromark`](https://github.com/micromark/micromark/tree/main/packages/micromark-util-encode)
-pub fn encode(value: &str) -> String {
- value
- .replace('&', "&amp;")
- .replace('"', "&quot;")
- .replace('<', "&lt;")
- .replace('>', "&gt;")
-}
-
-/// Make a value safe for injection as a URL.
-///
-/// This encodes unsafe characters with percent-encoding and skips already
-/// encoded sequences (see `normalize_uri` below).
-/// Further unsafe characters are encoded as character references (see
-/// `encode`).
-///
-/// Then, a vec of (lowercase) allowed protocols can be given, in which case
-/// the URL is sanitized.
-///
-/// For example, `Some(vec!["http", "https", "irc", "ircs", "mailto", "xmpp"])`
-/// can be used for `a[href]`, or `Some(vec!["http", "https"])` for `img[src]`.
-/// If the URL includes an unknown protocol (one not matched by `protocol`, such
-/// as a dangerous example, `javascript:`), the value is ignored.
-pub fn sanitize_uri(value: &str, protocols: &Option<Vec<&str>>) -> String {
- let value = encode(&normalize_uri(value));
-
- if let Some(protocols) = protocols {
- let chars: Vec<char> = value.chars().collect();
- let mut index = 0;
- let mut colon: Option<usize> = None;
-
- while index < chars.len() {
- let char = chars[index];
-
- match char {
- ':' => {
- colon = Some(index);
- break;
- }
- '?' | '#' | '/' => break,
- _ => {}
- }
-
- index += 1;
- }
-
- // If there is no protocol, or the first colon is after `?`, `#`, or `/`, it’s relative.
- // It is a protocol, it should be allowed.
- if let Some(colon) = colon {
- let protocol = chars[0..colon].iter().collect::<String>().to_lowercase();
- if !protocols.contains(&protocol.as_str()) {
- return "".to_string();
- }
- }
- }
-
- value
-}
-
-/// Normalize a URL (such as used in definitions).
-///
-/// Encode unsafe characters with percent-encoding, skipping already encoded
-/// sequences.
-fn normalize_uri(value: &str) -> String {
- let chars: Vec<char> = value.chars().collect();
- let mut result: Vec<String> = vec![];
- let mut index = 0;
- let mut start = 0;
- let mut buff = [0; 4];
-
- while index < chars.len() {
- let char = chars[index];
-
- // A correct percent encoded value.
- if char == '%'
- && index + 2 < chars.len()
- && chars[index + 1].is_ascii_alphanumeric()
- && chars[index + 2].is_ascii_alphanumeric()
- {
- index += 3;
- continue;
- }
-
- // Note: Rust already takes care of lone astral surrogates.
- // Non-ascii or not allowed ascii.
- if char >= '\u{0080}'
- || !matches!(char, '!' | '#' | '$' | '&'..=';' | '=' | '?'..='Z' | '_' | 'a'..='z' | '~')
- {
- result.push(chars[start..index].iter().collect::<String>());
-
- char.encode_utf8(&mut buff);
- result.push(
- buff[0..char.len_utf8()]
- .iter()
- .map(|&byte| format!("%{:X}", byte))
- .collect::<String>(),
- );
-
- start = index + 1;
- }
-
- index += 1;
- }
-
- result.push(chars[start..].iter().collect::<String>());
-
- result.join("")
-}
-
-/// Decode numeric character references.
-///
-/// Turn the number (in string form as either hexadecimal or decimal) coming
-/// from a numeric character reference into a character.
-/// Whether the base of the string form is `10` (decimal) or `16` (hexadecimal)
-/// must be passed as the `radix` parameter.
-///
-/// This returns the `char` associated with that number or a replacement
-/// character for C0 control characters (except for ASCII whitespace), C1
-/// control characters, lone surrogates, noncharacters, and out of range
-/// characters.
-///
-/// ## Examples
-///
-/// ```rust ignore
-/// use micromark::util::decode_numeric_character_reference;
-///
-/// assert_eq!(decode_numeric_character_reference("123", 10), '{');
-/// assert_eq!(decode_numeric_character_reference("9", 16), '\t');
-/// assert_eq!(decode_numeric_character_reference("0", 10), '�'); // Not allowed.
-/// ```
-///
-/// ## Panics
-///
-/// This function panics if a invalid string or an out of bounds valid string
-/// is given.
-/// It is expected that figuring out whether a number is allowed is handled in
-/// the parser.
-/// When `micromark` is used, this function never panics.
-///
-/// ## References
-///
-/// * [`micromark-util-decode-numeric-character-reference` in `micromark`](https://github.com/micromark/micromark/tree/main/packages/micromark-util-decode-numeric-character-reference)
-/// * [*§ 2.5 Entity and numeric character references* in `CommonMark`](https://spec.commonmark.org/0.30/#entity-and-numeric-character-references)
-pub fn decode_numeric_character_reference(value: &str, radix: u32) -> char {
- let code = u32::from_str_radix(value, radix).expect("expected `value` to be an int");
-
- if
- // C0 except for HT, LF, FF, CR, space
- code < 0x09 ||
- code == 0x0B ||
- (code > 0x0D && code < 0x20) ||
- // Control character (DEL) of the basic block and C1 controls.
- (code > 0x7E && code < 0xA0) ||
- // Lone high surrogates and low surrogates.
- (code > 0xd7ff && code < 0xe000) ||
- // Noncharacters.
- (code > 0xfdcf && code < 0xfdf0) ||
- ((code & 0xffff) == 0xffff) ||
- ((code & 0xffff) == 0xfffe) ||
- // Out of range
- code > 0x0010_ffff
- {
- '�'
- } else {
- char::from_u32(code).expect("expected valid `code`")
- }
-}
-
-/// Decode named character references.
-///
-/// Turn the name coming from a named character reference (without the `&` or
-/// `;`) into a string.
-/// This looks the given string up in [`CHARACTER_REFERENCE_NAMES`][] and then
-/// takes the corresponding value from [`CHARACTER_REFERENCE_VALUES`][].
-///
-/// The result is `String` instead of `char` because named character references
-/// can expand into multiple characters.
-///
-/// ## Examples
-///
-/// ```rust ignore
-/// use micromark::util::decode_named_character_reference;
-///
-/// assert_eq!(decode_named_character_reference("amp"), "&");
-/// assert_eq!(decode_named_character_reference("AElig"), "Æ");
-/// assert_eq!(decode_named_character_reference("aelig"), "æ");
-/// ```
-///
-/// ## Panics
-///
-/// This function panics if a name not in [`CHARACTER_REFERENCE_NAMES`][] is
-/// given.
-/// It is expected that figuring out whether a name is allowed is handled in
-/// the parser.
-/// When `micromark` is used, this function never panics.
-///
-/// ## References
-///
-/// * [`wooorm/decode-named-character-reference`](https://github.com/wooorm/decode-named-character-reference)
-/// * [*§ 2.5 Entity and numeric character references* in `CommonMark`](https://spec.commonmark.org/0.30/#entity-and-numeric-character-references)
-pub fn decode_named_character_reference(value: &str) -> String {
- let position = CHARACTER_REFERENCE_NAMES.iter().position(|&x| x == value);
- if let Some(index) = position {
- CHARACTER_REFERENCE_VALUES[index].to_string()
- } else {
- unreachable!("expected valid `name`")
- }
-}
-
-/// A struct representing the span of an opening and closing event of a token.
-#[derive(Debug)]
-pub struct Span {
- // To do: probably needed in the future.
- // start: Point,
- /// Absolute offset (and `index` in `codes`) of where this span starts.
- pub start_index: usize,
- // To do: probably needed in the future.
- // end: Point,
- /// Absolute offset (and `index` in `codes`) of where this span ends.
- pub end_index: usize,
- // To do: probably needed in the future.
- // token_type: TokenType,
-}
-
-/// Get a span from an event.
-///
-/// Get the span of an `exit` event, by looking backwards through the events to
-/// find the corresponding `enter` event.
-/// This assumes that tokens with the same are not nested.
-///
-/// ## Panics
-///
-/// This function panics if an enter event is given.
-/// When `micromark` is used, this function never panics.
-pub fn get_span(events: &[Event], index: usize) -> Span {
- let exit = &events[index];
- // let end = exit.point.clone();
- let end_index = exit.index;
- let token_type = exit.token_type.clone();
- // To do: support `enter` events if needed and walk forwards?
- assert_eq!(
- exit.event_type,
- EventType::Exit,
- "expected `get_span` to be called on `exit` event"
- );
- let mut enter_index = index - 1;
-
- loop {
- let enter = &events[enter_index];
- if enter.event_type == EventType::Enter && enter.token_type == token_type {
- return Span {
- // start: enter.point.clone(),
- start_index: enter.index,
- // end,
- end_index,
- // token_type,
- };
- }
-
- enter_index -= 1;
- }
-}
-
-/// Serialize a span, optionally expanding tabs.
-pub fn slice_serialize(codes: &[Code], span: &Span, expand_tabs: bool) -> String {
- serialize_chunks(slice_codes(codes, span), expand_tabs)
-}
-
-/// Get a slice of codes from a span.
-pub fn slice_codes<'a>(codes: &'a [Code], span: &Span) -> &'a [Code] {
- &codes[span.start_index..span.end_index]
-}
-
-/// Serialize a slice of codes, optionally expanding tabs.
-pub fn serialize_chunks(codes: &[Code], expand_tabs: bool) -> String {
- let mut at_tab = false;
- let mut index = 0;
- let mut value: Vec<char> = vec![];
-
- while index < codes.len() {
- let code = codes[index];
- let mut at_tab_next = false;
-
- match code {
- Code::CarriageReturnLineFeed => {
- value.push('\r');
- value.push('\n');
- }
- Code::Char(char) if char == '\n' || char == '\r' => {
- value.push(char);
- }
- Code::Char(char) if char == '\t' => {
- at_tab_next = true;
- value.push(if expand_tabs { ' ' } else { char });
- }
- Code::VirtualSpace => {
- if !expand_tabs && at_tab {
- index += 1;
- continue;
- }
- value.push(' ');
- }
- Code::Char(char) => {
- value.push(char);
- }
- Code::None => {
- unreachable!("unexpected EOF code in codes");
- }
- }
-
- at_tab = at_tab_next;
-
- index += 1;
- }
-
- value.into_iter().collect()
-}