mirror of https://github.com/helix-editor/helix
104 lines
3.3 KiB
Rust
104 lines
3.3 KiB
Rust
use std::ops::{self, RangeBounds};
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/// A range of `char`s within the text.
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#[derive(Debug, Clone, Copy, PartialOrd, Ord, PartialEq, Eq)]
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pub struct Range<T = usize> {
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pub start: T,
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pub end: T,
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}
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impl<T: PartialOrd> Range<T> {
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pub fn contains(&self, other: Self) -> bool {
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self.start <= other.start && other.end <= self.end
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}
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pub fn is_empty(&self) -> bool {
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self.end <= self.start
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}
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}
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impl<T> RangeBounds<T> for Range<T> {
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fn start_bound(&self) -> ops::Bound<&T> {
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ops::Bound::Included(&self.start)
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}
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fn end_bound(&self) -> ops::Bound<&T> {
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ops::Bound::Excluded(&self.end)
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}
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}
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/// Returns true if all ranges yielded by `sub_set` are contained by
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/// `super_set`. This is essentially an optimized implementation of
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/// `sub_set.all(|rb| super_set.any(|ra| ra.contains(rb)))` that runs in O(m+n)
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/// instead of O(mn) (and in many cases faster).
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///
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/// Both iterators must uphold a the follwong invariants:
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/// * ranges must not overlap (but they can be adjecent)
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/// * ranges must be sorted
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pub fn is_subset<const ALLOW_EMPTY: bool>(
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mut super_set: impl Iterator<Item = Range>,
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mut sub_set: impl Iterator<Item = Range>,
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) -> bool {
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let (mut super_range, mut sub_range) = (super_set.next(), sub_set.next());
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loop {
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match (super_range, sub_range) {
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// skip over irrelevant ranges
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(Some(ra), Some(rb))
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if ra.end <= rb.start && (ra.start != rb.start || !ALLOW_EMPTY) =>
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{
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super_range = super_set.next();
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}
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(Some(ra), Some(rb)) => {
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if ra.contains(rb) {
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sub_range = sub_set.next();
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} else {
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return false;
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}
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}
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(None, Some(_)) => {
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// exhausted `super_set`, we can't match the reminder of `sub_set`
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return false;
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}
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(_, None) => {
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// no elements from `sub_sut` left to match, `super_set` contains `sub_set`
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return true;
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}
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}
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}
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}
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pub fn is_exact_subset(
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mut super_set: impl Iterator<Item = Range>,
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mut sub_set: impl Iterator<Item = Range>,
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) -> bool {
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let (mut super_range, mut sub_range) = (super_set.next(), sub_set.next());
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let mut super_range_matched = true;
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loop {
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match (super_range, sub_range) {
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// skip over irrelevant ranges
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(Some(ra), Some(rb)) if ra.end <= rb.start && ra.start < rb.start => {
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if !super_range_matched {
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return false;
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}
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super_range_matched = false;
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super_range = super_set.next();
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}
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(Some(ra), Some(rb)) => {
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if ra.contains(rb) {
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super_range_matched = true;
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sub_range = sub_set.next();
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} else {
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return false;
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}
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}
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(None, Some(_)) => {
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// exhausted `super_set`, we can't match the reminder of `sub_set`
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return false;
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}
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(_, None) => {
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// no elements from `sub_sut` left to match, `super_set` contains `sub_set`
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return super_set.next().is_none();
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}
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}
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}
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}
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