Source code
Revision control
Copy as Markdown
Other Tools
// Copyright 2015 The Servo Project Developers. See the
// COPYRIGHT file at the top-level directory of this distribution.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! 3.3.4 - 3.3.6. Resolve implicit levels and types.
#[cfg(not(feature = "smallvec"))]
use alloc::vec::Vec;
use core::cmp::max;
#[cfg(feature = "smallvec")]
use smallvec::SmallVec;
use super::char_data::BidiClass::{self, *};
use super::level::Level;
use super::prepare::{not_removed_by_x9, IsolatingRunSequence};
use super::{BidiDataSource, TextSource};
/// 3.3.4 Resolving Weak Types
///
#[cfg_attr(feature = "flame_it", flamer::flame)]
pub fn resolve_weak<'a, T: TextSource<'a> + ?Sized>(
text: &'a T,
sequence: &IsolatingRunSequence,
processing_classes: &mut [BidiClass],
) {
// Note: The spec treats these steps as individual passes that are applied one after the other
// on the entire IsolatingRunSequence at once. We instead collapse it into a single iteration,
// which is straightforward for rules that are based on the state of the current character, but not
// for rules that care about surrounding characters. To deal with them, we retain additional state
// about previous character classes that may have since been changed by later rules.
// The previous class for the purposes of rule W4/W6, not tracking changes made after or during W4.
let mut prev_class_before_w4 = sequence.sos;
// The previous class for the purposes of rule W5.
let mut prev_class_before_w5 = sequence.sos;
// The previous class for the purposes of rule W1, not tracking changes from any other rules.
let mut prev_class_before_w1 = sequence.sos;
let mut last_strong_is_al = false;
#[cfg(feature = "smallvec")]
let mut et_run_indices = SmallVec::<[usize; 8]>::new(); // for W5
#[cfg(not(feature = "smallvec"))]
let mut et_run_indices = Vec::new(); // for W5
#[cfg(feature = "smallvec")]
let mut bn_run_indices = SmallVec::<[usize; 8]>::new(); // for W5 + <https://www.unicode.org/reports/tr9/#Retaining_Explicit_Formatting_Characters>
#[cfg(not(feature = "smallvec"))]
let mut bn_run_indices = Vec::new(); // for W5 + <https://www.unicode.org/reports/tr9/#Retaining_Explicit_Formatting_Characters>
for (run_index, level_run) in sequence.runs.iter().enumerate() {
for i in &mut level_run.clone() {
if processing_classes[i] == BN {
// Keeps track of bn runs for W5 in case we see an ET.
bn_run_indices.push(i);
// BNs aren't real, skip over them.
continue;
}
// Store the processing class of all rules before W2/W1.
// Used to keep track of the last strong character for W2. W3 is able to insert new strong
// characters, so we don't want to be misled by it.
let mut w2_processing_class = processing_classes[i];
//
if processing_classes[i] == NSM {
processing_classes[i] = match prev_class_before_w1 {
RLI | LRI | FSI | PDI => ON,
_ => prev_class_before_w1,
};
// W1 occurs before W2, update this.
w2_processing_class = processing_classes[i];
}
prev_class_before_w1 = processing_classes[i];
//
match processing_classes[i] {
EN => {
if last_strong_is_al {
// W2. If previous strong char was AL, change EN to AN.
processing_classes[i] = AN;
}
}
// W3.
AL => processing_classes[i] = R,
_ => {}
}
// update last_strong_is_al.
match w2_processing_class {
L | R => {
last_strong_is_al = false;
}
AL => {
last_strong_is_al = true;
}
_ => {}
}
let class_before_w456 = processing_classes[i];
// (see below for W6 terminator code)
//
match processing_classes[i] {
EN => {
// W5. If a run of ETs is adjacent to an EN, change the ETs to EN.
for j in &et_run_indices {
processing_classes[*j] = EN;
}
et_run_indices.clear();
}
ES | CS => {
// We want to make sure we check the correct next character by skipping past the rest
// of this one.
if let Some((_, char_len)) = text.char_at(i) {
let mut next_class = sequence
.iter_forwards_from(i + char_len, run_index)
.map(|j| processing_classes[j])
.find(not_removed_by_x9)
.unwrap_or(sequence.eos);
if next_class == EN && last_strong_is_al {
// Apply W2 to next_class. We know that last_strong_is_al
// has no chance of changing on this character so we can still assume its value
// will be the same by the time we get to it.
next_class = AN;
}
processing_classes[i] =
match (prev_class_before_w4, processing_classes[i], next_class) {
// W4
(EN, ES, EN) | (EN, CS, EN) => EN,
// W4
(AN, CS, AN) => AN,
// W6 (separators only)
(_, _, _) => ON,
};
// We have to do this before W5 gets its grubby hands on these characters and thinks
// they're part of an ET run.
// We check for ON to ensure that we had hit the W6 branch above, since this `ES | CS` match
// arm handles both W4 and W6.
if processing_classes[i] == ON {
for idx in sequence.iter_backwards_from(i, run_index) {
let class = &mut processing_classes[idx];
if *class != BN {
break;
}
*class = ON;
}
for idx in sequence.iter_forwards_from(i + char_len, run_index) {
let class = &mut processing_classes[idx];
if *class != BN {
break;
}
*class = ON;
}
}
} else {
// We're in the middle of a character, copy over work done for previous bytes
// since it's going to be the same answer.
processing_classes[i] = processing_classes[i - 1];
}
}
ET => {
match prev_class_before_w5 {
EN => processing_classes[i] = EN,
_ => {
// If there was a BN run before this, that's now a part of this ET run.
et_run_indices.extend(bn_run_indices.clone());
// In case this is followed by an EN.
et_run_indices.push(i);
}
}
}
_ => {}
}
// Common loop iteration code
//
// BN runs would have already continued the loop, clear them before we get to the next one.
bn_run_indices.clear();
// W6 above only deals with separators, so it doesn't change anything W5 cares about,
// so we still can update this after running that part of W6.
prev_class_before_w5 = processing_classes[i];
// (see above for W6 separator code)
//
if prev_class_before_w5 != ET {
// W6. If we didn't find an adjacent EN, turn any ETs into ON instead.
for j in &et_run_indices {
processing_classes[*j] = ON;
}
et_run_indices.clear();
}
// We stashed this before W4/5/6 could get their grubby hands on it, and it's not
// used in the W6 terminator code below so we can update it now.
prev_class_before_w4 = class_before_w456;
}
}
// Rerun this check in case we ended with a sequence of BNs (i.e., we'd never
// hit the end of the for loop above).
// W6. If we didn't find an adjacent EN, turn any ETs into ON instead.
for j in &et_run_indices {
processing_classes[*j] = ON;
}
et_run_indices.clear();
// W7. If the previous strong char was L, change EN to L.
let mut last_strong_is_l = sequence.sos == L;
for i in sequence.runs.iter().cloned().flatten() {
match processing_classes[i] {
EN if last_strong_is_l => {
processing_classes[i] = L;
}
L => {
last_strong_is_l = true;
}
R | AL => {
last_strong_is_l = false;
}
// Already scanning past BN here.
_ => {}
}
}
}
#[cfg(feature = "smallvec")]
type BracketPairVec = SmallVec<[BracketPair; 8]>;
#[cfg(not(feature = "smallvec"))]
type BracketPairVec = Vec<BracketPair>;
/// 3.3.5 Resolving Neutral Types
///
#[cfg_attr(feature = "flame_it", flamer::flame)]
pub fn resolve_neutral<'a, D: BidiDataSource, T: TextSource<'a> + ?Sized>(
text: &'a T,
data_source: &D,
sequence: &IsolatingRunSequence,
levels: &[Level],
original_classes: &[BidiClass],
processing_classes: &mut [BidiClass],
) {
// e = embedding direction
let e: BidiClass = levels[sequence.runs[0].start].bidi_class();
let not_e = if e == BidiClass::L {
BidiClass::R
} else {
BidiClass::L
};
// N0. Process bracket pairs.
// > Identify the bracket pairs in the current isolating run sequence according to BD16.
// We use processing_classes, not original_classes, due to BD14/BD15
let mut bracket_pairs = BracketPairVec::new();
identify_bracket_pairs(
text,
data_source,
sequence,
processing_classes,
&mut bracket_pairs,
);
// > For each bracket-pair element in the list of pairs of text positions
//
// Note: Rust ranges are interpreted as [start..end), be careful using `pair` directly
// for indexing as it will include the opening bracket pair but not the closing one.
for pair in bracket_pairs {
#[cfg(feature = "std")]
debug_assert!(
pair.start < processing_classes.len(),
"identify_bracket_pairs returned a range that is out of bounds!"
);
#[cfg(feature = "std")]
debug_assert!(
pair.end < processing_classes.len(),
"identify_bracket_pairs returned a range that is out of bounds!"
);
let mut found_e = false;
let mut found_not_e = false;
let mut class_to_set = None;
let start_char_len =
T::char_len(text.subrange(pair.start..pair.end).chars().next().unwrap());
// > Inspect the bidirectional types of the characters enclosed within the bracket pair.
//
// `pair` is [start, end) so we will end up processing the opening character but not the closing one.
//
for enclosed_i in sequence.iter_forwards_from(pair.start + start_char_len, pair.start_run) {
if enclosed_i >= pair.end {
#[cfg(feature = "std")]
debug_assert!(
enclosed_i == pair.end,
"If we skipped past this, the iterator is broken"
);
break;
}
let class = processing_classes[enclosed_i];
if class == e {
found_e = true;
} else if class == not_e {
found_not_e = true;
} else if matches!(class, BidiClass::EN | BidiClass::AN) {
// > Within this scope, bidirectional types EN and AN are treated as R.
if e == BidiClass::L {
found_not_e = true;
} else {
found_e = true;
}
}
// If we have found a character with the class of the embedding direction
// we can bail early.
if found_e {
break;
}
}
// > If any strong type (either L or R) matching the embedding direction is found
if found_e {
// > .. set the type for both brackets in the pair to match the embedding direction
class_to_set = Some(e);
// > Otherwise, if there is a strong type it must be opposite the embedding direction
} else if found_not_e {
// > Therefore, test for an established context with a preceding strong type by
// > checking backwards before the opening paired bracket
// > until the first strong type (L, R, or sos) is found.
// (see note above about processing_classes and character boundaries)
let mut previous_strong = sequence
.iter_backwards_from(pair.start, pair.start_run)
.map(|i| processing_classes[i])
.find(|class| {
matches!(
class,
BidiClass::L | BidiClass::R | BidiClass::EN | BidiClass::AN
)
})
.unwrap_or(sequence.sos);
// > Within this scope, bidirectional types EN and AN are treated as R.
if matches!(previous_strong, BidiClass::EN | BidiClass::AN) {
previous_strong = BidiClass::R;
}
// > If the preceding strong type is also opposite the embedding direction,
// > context is established,
// > so set the type for both brackets in the pair to that direction.
// AND
// > Otherwise set the type for both brackets in the pair to the embedding direction.
// > Either way it gets set to previous_strong
//
// Both branches amount to setting the type to the strong type.
class_to_set = Some(previous_strong);
}
if let Some(class_to_set) = class_to_set {
// Update all processing classes corresponding to the start and end elements, as requested.
// We should include all bytes of the character, not the first one.
let end_char_len =
T::char_len(text.subrange(pair.end..text.len()).chars().next().unwrap());
for class in &mut processing_classes[pair.start..pair.start + start_char_len] {
*class = class_to_set;
}
for class in &mut processing_classes[pair.end..pair.end + end_char_len] {
*class = class_to_set;
}
for idx in sequence.iter_backwards_from(pair.start, pair.start_run) {
let class = &mut processing_classes[idx];
if *class != BN {
break;
}
*class = class_to_set;
}
// > Any number of characters that had original bidirectional character type NSM prior to the application of
// > W1 that immediately follow a paired bracket which changed to L or R under N0 should change to match the type of their preceding bracket.
// This rule deals with sequences of NSMs, so we can just update them all at once, we don't need to worry
// about character boundaries. We do need to be careful to skip the full set of bytes for the parentheses characters.
let nsm_start = pair.start + start_char_len;
for idx in sequence.iter_forwards_from(nsm_start, pair.start_run) {
let class = original_classes[idx];
if class == BidiClass::NSM || processing_classes[idx] == BN {
processing_classes[idx] = class_to_set;
} else {
break;
}
}
let nsm_end = pair.end + end_char_len;
for idx in sequence.iter_forwards_from(nsm_end, pair.end_run) {
let class = original_classes[idx];
if class == BidiClass::NSM || processing_classes[idx] == BN {
processing_classes[idx] = class_to_set;
} else {
break;
}
}
}
// > Otherwise, there are no strong types within the bracket pair
// > Therefore, do not set the type for that bracket pair
}
// N1 and N2.
// Indices of every byte in this isolating run sequence
let mut indices = sequence.runs.iter().flat_map(Clone::clone);
let mut prev_class = sequence.sos;
while let Some(mut i) = indices.next() {
// Process sequences of NI characters.
#[cfg(feature = "smallvec")]
let mut ni_run = SmallVec::<[usize; 8]>::new();
#[cfg(not(feature = "smallvec"))]
let mut ni_run = Vec::new();
if is_NI(processing_classes[i]) || processing_classes[i] == BN {
// Consume a run of consecutive NI characters.
ni_run.push(i);
let mut next_class;
loop {
match indices.next() {
Some(j) => {
i = j;
next_class = processing_classes[j];
if is_NI(next_class) || next_class == BN {
ni_run.push(i);
} else {
break;
}
}
None => {
next_class = sequence.eos;
break;
}
};
}
// N1-N2.
//
let new_class = match (prev_class, next_class) {
(L, L) => L,
(R, R)
| (R, AN)
| (R, EN)
| (AN, R)
| (AN, AN)
| (AN, EN)
| (EN, R)
| (EN, AN)
| (EN, EN) => R,
(_, _) => e,
};
for j in &ni_run {
processing_classes[*j] = new_class;
}
ni_run.clear();
}
prev_class = processing_classes[i];
}
}
struct BracketPair {
/// The text-relative index of the opening bracket.
start: usize,
/// The text-relative index of the closing bracket.
end: usize,
/// The index of the run (in the run sequence) that the opening bracket is in.
start_run: usize,
/// The index of the run (in the run sequence) that the closing bracket is in.
end_run: usize,
}
/// 3.1.3 Identifying Bracket Pairs
///
/// Returns all paired brackets in the source, as indices into the
/// text source.
///
fn identify_bracket_pairs<'a, T: TextSource<'a> + ?Sized, D: BidiDataSource>(
text: &'a T,
data_source: &D,
run_sequence: &IsolatingRunSequence,
original_classes: &[BidiClass],
bracket_pairs: &mut BracketPairVec,
) {
#[cfg(feature = "smallvec")]
let mut stack = SmallVec::<[(char, usize, usize); 8]>::new();
#[cfg(not(feature = "smallvec"))]
let mut stack = Vec::new();
for (run_index, level_run) in run_sequence.runs.iter().enumerate() {
for (i, ch) in text.subrange(level_run.clone()).char_indices() {
let actual_index = level_run.start + i;
// All paren characters are ON.
// From BidiBrackets.txt:
// > The Unicode property value stability policy guarantees that characters
// > which have bpt=o or bpt=c also have bc=ON and Bidi_M=Y
if original_classes[actual_index] != BidiClass::ON {
continue;
}
if let Some(matched) = data_source.bidi_matched_opening_bracket(ch) {
if matched.is_open {
// > If an opening paired bracket is found ...
// > ... and there is no room in the stack,
// > stop processing BD16 for the remainder of the isolating run sequence.
if stack.len() >= 63 {
break;
}
// > ... push its Bidi_Paired_Bracket property value and its text position onto the stack
stack.push((matched.opening, actual_index, run_index))
} else {
// > If a closing paired bracket is found, do the following
// > Declare a variable that holds a reference to the current stack element
// > and initialize it with the top element of the stack.
// AND
// > Else, if the current stack element is not at the bottom of the stack
for (stack_index, element) in stack.iter().enumerate().rev() {
// > Compare the closing paired bracket being inspected or its canonical
// > equivalent to the bracket in the current stack element.
if element.0 == matched.opening {
// > If the values match, meaning the two characters form a bracket pair, then
// > Append the text position in the current stack element together with the
// > text position of the closing paired bracket to the list.
let pair = BracketPair {
start: element.1,
end: actual_index,
start_run: element.2,
end_run: run_index,
};
bracket_pairs.push(pair);
// > Pop the stack through the current stack element inclusively.
stack.truncate(stack_index);
break;
}
}
}
}
}
}
// > Sort the list of pairs of text positions in ascending order based on
// > the text position of the opening paired bracket.
bracket_pairs.sort_by_key(|r| r.start);
}
/// 3.3.6 Resolving Implicit Levels
///
/// Returns the maximum embedding level in the paragraph.
///
#[cfg_attr(feature = "flame_it", flamer::flame)]
pub fn resolve_levels(processing_classes: &[BidiClass], levels: &mut [Level]) -> Level {
let mut max_level = Level::ltr();
assert_eq!(processing_classes.len(), levels.len());
for i in 0..levels.len() {
match (levels[i].is_rtl(), processing_classes[i]) {
(false, AN) | (false, EN) => levels[i].raise(2).expect("Level number error"),
(false, R) | (true, L) | (true, EN) | (true, AN) => {
levels[i].raise(1).expect("Level number error")
}
(_, _) => {}
}
max_level = max(max_level, levels[i]);
}
max_level
}
/// Neutral or Isolate formatting character (B, S, WS, ON, FSI, LRI, RLI, PDI)
///
#[allow(non_snake_case)]
fn is_NI(class: BidiClass) -> bool {
matches!(class, B | S | WS | ON | FSI | LRI | RLI | PDI)
}