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Diffstat (limited to 'vendor/unicode-bidi/src/implicit.rs')
| -rw-r--r-- | vendor/unicode-bidi/src/implicit.rs | 239 |
1 files changed, 239 insertions, 0 deletions
diff --git a/vendor/unicode-bidi/src/implicit.rs b/vendor/unicode-bidi/src/implicit.rs new file mode 100644 index 000000000..bf37f17e6 --- /dev/null +++ b/vendor/unicode-bidi/src/implicit.rs @@ -0,0 +1,239 @@ +// 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 +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your +// 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. + +use alloc::vec::Vec; +use core::cmp::max; + +use super::char_data::BidiClass::{self, *}; +use super::level::Level; +use super::prepare::{not_removed_by_x9, removed_by_x9, IsolatingRunSequence, LevelRun}; + +/// 3.3.4 Resolving Weak Types +/// +/// <http://www.unicode.org/reports/tr9/#Resolving_Weak_Types> +#[cfg_attr(feature = "flame_it", flamer::flame)] +pub fn resolve_weak(sequence: &IsolatingRunSequence, processing_classes: &mut [BidiClass]) { + // FIXME (#8): This function applies steps W1-W6 in a single pass. This can produce + // incorrect results in cases where a "later" rule changes the value of `prev_class` seen + // by an "earlier" rule. We should either split this into separate passes, or preserve + // extra state so each rule can see the correct previous class. + + // FIXME: Also, this could be the cause of increased failure for using longer-UTF-8 chars in + // conformance tests, like BidiTest:69635 (AL ET EN) + + let mut prev_class = sequence.sos; + let mut last_strong_is_al = false; + let mut et_run_indices = Vec::new(); // for W5 + + // Like sequence.runs.iter().flat_map(Clone::clone), but make indices itself clonable. + fn id(x: LevelRun) -> LevelRun { + x + } + let mut indices = sequence + .runs + .iter() + .cloned() + .flat_map(id as fn(LevelRun) -> LevelRun); + + while let Some(i) = indices.next() { + match processing_classes[i] { + // <http://www.unicode.org/reports/tr9/#W1> + NSM => { + processing_classes[i] = match prev_class { + RLI | LRI | FSI | PDI => ON, + _ => prev_class, + }; + } + EN => { + if last_strong_is_al { + // W2. If previous strong char was AL, change EN to AN. + processing_classes[i] = AN; + } else { + // 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(); + } + } + // <http://www.unicode.org/reports/tr9/#W3> + AL => processing_classes[i] = R, + + // <http://www.unicode.org/reports/tr9/#W4> + ES | CS => { + let next_class = indices + .clone() + .map(|j| processing_classes[j]) + .find(not_removed_by_x9) + .unwrap_or(sequence.eos); + processing_classes[i] = match (prev_class, processing_classes[i], next_class) { + (EN, ES, EN) | (EN, CS, EN) => EN, + (AN, CS, AN) => AN, + (_, _, _) => ON, + } + } + // <http://www.unicode.org/reports/tr9/#W5> + ET => { + match prev_class { + EN => processing_classes[i] = EN, + _ => et_run_indices.push(i), // In case this is followed by an EN. + } + } + class => { + if removed_by_x9(class) { + continue; + } + } + } + + prev_class = processing_classes[i]; + match prev_class { + L | R => { + last_strong_is_al = false; + } + AL => { + last_strong_is_al = true; + } + _ => {} + } + if prev_class != 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(); + } + } + + // W7. If the previous strong char was L, change EN to L. + let mut last_strong_is_l = sequence.sos == L; + for run in &sequence.runs { + for i in run.clone() { + 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; + } + _ => {} + } + } + } +} + +/// 3.3.5 Resolving Neutral Types +/// +/// <http://www.unicode.org/reports/tr9/#Resolving_Neutral_Types> +#[cfg_attr(feature = "flame_it", flamer::flame)] +pub fn resolve_neutral( + sequence: &IsolatingRunSequence, + levels: &[Level], + processing_classes: &mut [BidiClass], +) { + let e: BidiClass = levels[sequence.runs[0].start].bidi_class(); + let mut indices = sequence.runs.iter().flat_map(Clone::clone); + let mut prev_class = sequence.sos; + + while let Some(mut i) = indices.next() { + // N0. Process bracket pairs. + // TODO + + // Process sequences of NI characters. + let mut ni_run = Vec::new(); + if is_NI(processing_classes[i]) { + // Consume a run of consecutive NI characters. + ni_run.push(i); + let mut next_class; + loop { + match indices.next() { + Some(j) => { + i = j; + if removed_by_x9(processing_classes[i]) { + continue; + } + next_class = processing_classes[j]; + if is_NI(next_class) { + ni_run.push(i); + } else { + break; + } + } + None => { + next_class = sequence.eos; + break; + } + }; + } + + // N1-N2. + // + // <http://www.unicode.org/reports/tr9/#N1> + // <http://www.unicode.org/reports/tr9/#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]; + } +} + +/// 3.3.6 Resolving Implicit Levels +/// +/// Returns the maximum embedding level in the paragraph. +/// +/// <http://www.unicode.org/reports/tr9/#Resolving_Implicit_Levels> +#[cfg_attr(feature = "flame_it", flamer::flame)] +pub fn resolve_levels(original_classes: &[BidiClass], levels: &mut [Level]) -> Level { + let mut max_level = Level::ltr(); + + assert_eq!(original_classes.len(), levels.len()); + for i in 0..levels.len() { + match (levels[i].is_rtl(), original_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) +/// +/// <http://www.unicode.org/reports/tr9/#NI> +#[allow(non_snake_case)] +fn is_NI(class: BidiClass) -> bool { + match class { + B | S | WS | ON | FSI | LRI | RLI | PDI => true, + _ => false, + } +} |