118 lines
4.9 KiB
Rust
118 lines
4.9 KiB
Rust
use crate::gen::entities::{ENTITY, EntityType};
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use crate::pattern::TrieNodeMatch;
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use std::char::from_u32;
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use crate::spec::codepoint::{is_hex_digit, is_digit, is_lower_hex_digit, is_upper_hex_digit};
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use crate::proc::Processor;
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#[inline(always)]
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fn parse_numeric_entity(code: &mut [u8], read_start: usize, write_pos: usize, is_digit: fn(u8) -> bool, on_digit: fn(u32, u8) -> u32, max_digits: u8) -> (usize, usize) {
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let mut value = 0u32;
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let mut digits = 0;
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let mut read_next = read_start;
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// Skip initial zeros.
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while code.get(read_next).filter(|c| **c == b'0').is_some() {
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read_next += 1;
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};
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// Browser will still continue to consume digits past max_digits.
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loop {
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match code.get(read_next) {
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Some(&c) if is_digit(c) => {
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// We don't care about overflow, as it will be considered malformed past max_digits anyway.
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value = on_digit(value, c);
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read_next += 1;
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digits += 1;
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}
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_ => break,
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};
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};
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// Semicolon is required by spec but seems to be optional in actual browser behaviour.
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if let Some(b';') = code.get(read_next) {
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read_next += 1;
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};
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// Browsers decode to a replacement character (U+FFFD) if malformed.
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let char = Some(value)
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.filter(|_| digits <= max_digits)
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.and_then(|v| from_u32(v))
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.unwrap_or('\u{FFFD}');
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(read_next - read_start, char.encode_utf8(&mut code[write_pos..]).len())
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}
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// Parse the entity and write its decoded value at the beginning of {@param code}.
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// Return the (read_len, write_len).
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// If malformed, returns the longest matching entity prefix length as (len, len).
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fn parse_entity(code: &mut [u8], read_pos: usize, write_pos: usize) -> (usize, usize) {
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match ENTITY.longest_matching_prefix(&code[read_pos..]) {
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TrieNodeMatch::Found { len: match_len, value } => match value {
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EntityType::Dec => parse_numeric_entity(
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code,
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// Skip past '&#'. Note that match_len is 3 as it matches '&#[0-9]'.
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read_pos + 2,
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write_pos,
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is_digit,
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|value, c| value.wrapping_mul(10).wrapping_add((c - b'0') as u32),
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7,
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),
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EntityType::Hex => parse_numeric_entity(
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code,
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// Skip past '&#x'. Note that match_len is 4 as it matches '&#x[0-9a-fA-F]'.
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read_pos + 3,
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write_pos,
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is_hex_digit,
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|value, c| value.wrapping_mul(16).wrapping_add(match c {
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c if is_digit(c) => (c - b'0') as u32,
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c if is_lower_hex_digit(c) => (c - b'a') as u32,
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c if is_upper_hex_digit(c) => (c - b'A') as u32,
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_ => unreachable!(),
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}),
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6,
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),
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EntityType::Named(decoded) => {
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code[write_pos..write_pos + decoded.len()].copy_from_slice(decoded);
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(match_len, decoded.len())
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}
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},
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// The entity is malformed.
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TrieNodeMatch::NotFound { reached } => (reached, reached),
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}
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}
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// Normalise entity such that "< hello" becomes "___< hello" and the range of '<' is returned.
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// For something like "&amp hello", it becomes "_______&amp hello" and (7, 14) is returned.
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pub fn maybe_normalise_entity(proc: &mut Processor) -> bool {
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if proc.peek(0).filter(|c| *c == b'&').is_none() {
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return false;
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};
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let start = proc.read_next;
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// We want to look ahead in case this entity decodes to something beginning with '&' and following code are also
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// entities that would decode to form an unintentional entity once decoded.
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// For example, `&amq` would output as `&` which is an unintentional entity.
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let mut read_next = start;
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let mut write_next = start;
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let mut node = Some(ENTITY);
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while node.filter(|n| n.value.is_none()).is_some()
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&& proc.code.get(read_next).filter(|c| **c == b'&').is_some()
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{
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let (entity_read, entity_write) = parse_entity(proc.code, read_next, write_next);
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node = node.unwrap().next_matching_node(&proc.code[write_next..write_next + entity_write], 0).map(|(node, _)| node);
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debug_assert!(entity_read > 0);
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read_next += entity_read;
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write_next += entity_write;
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};
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// Need to encode initial '&', so add 'amp'.
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let undecodable = node.and_then(|n| n.value).is_some();
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// Shift decoded value down so that it ends at read_next (exclusive).
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let mut shifted_start = read_next - (write_next - start - undecodable as usize);
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proc.code.copy_within(start + undecodable as usize..write_next, shifted_start);
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if undecodable {
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debug_assert_eq!(proc.code.get(start), Some(&b'&'));
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proc.code[shifted_start - 4..shifted_start].copy_from_slice(b"&");
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shifted_start -= 4;
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};
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proc.read_next = shifted_start;
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return true;
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}
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