bendns' repos / helix
Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'helix-stdx/src/range.rs')
-rw-r--r--helix-stdx/src/range.rs103
1 files changed, 103 insertions, 0 deletions
diff --git a/helix-stdx/src/range.rs b/helix-stdx/src/range.rs
new file mode 100644
index 00000000..0b241199
--- /dev/null
+++ b/helix-stdx/src/range.rs
@@ -0,0 +1,103 @@
+use std::ops::{self, RangeBounds};
+
+/// A range of `char`s within the text.
+#[derive(Debug, Clone, Copy, PartialOrd, Ord, PartialEq, Eq)]
+pub struct Range<T = usize> {
+ pub start: T,
+ pub end: T,
+}
+
+impl<T: PartialOrd> Range<T> {
+ pub fn contains(&self, other: Self) -> bool {
+ self.start <= other.start && other.end <= self.end
+ }
+ pub fn is_empty(&self) -> bool {
+ self.end <= self.start
+ }
+}
+
+impl<T> RangeBounds<T> for Range<T> {
+ fn start_bound(&self) -> ops::Bound<&T> {
+ ops::Bound::Included(&self.start)
+ }
+
+ fn end_bound(&self) -> ops::Bound<&T> {
+ ops::Bound::Excluded(&self.end)
+ }
+}
+
+/// Returns true if all ranges yielded by `sub_set` are contained by
+/// `super_set`. This is essentially an optimized implementation of
+/// `sub_set.all(|rb| super_set.any(|ra| ra.contains(rb)))` that runs in O(m+n)
+/// instead of O(mn) (and in many cases faster).
+///
+/// Both iterators must uphold a the following invariants:
+/// * ranges must not overlap (but they can be adjacent)
+/// * ranges must be sorted
+pub fn is_subset<const ALLOW_EMPTY: bool>(
+ mut super_set: impl Iterator<Item = Range>,
+ mut sub_set: impl Iterator<Item = Range>,
+) -> bool {
+ let (mut super_range, mut sub_range) = (super_set.next(), sub_set.next());
+ loop {
+ match (super_range, sub_range) {
+ // skip over irrelevant ranges
+ (Some(ra), Some(rb))
+ if ra.end <= rb.start && (ra.start != rb.start || !ALLOW_EMPTY) =>
+ {
+ super_range = super_set.next();
+ }
+ (Some(ra), Some(rb)) => {
+ if ra.contains(rb) {
+ sub_range = sub_set.next();
+ } else {
+ return false;
+ }
+ }
+ (None, Some(_)) => {
+ // exhausted `super_set`, we can't match the reminder of `sub_set`
+ return false;
+ }
+ (_, None) => {
+ // no elements from `sub_sut` left to match, `super_set` contains `sub_set`
+ return true;
+ }
+ }
+ }
+}
+
+pub fn is_exact_subset(
+ mut super_set: impl Iterator<Item = Range>,
+ mut sub_set: impl Iterator<Item = Range>,
+) -> bool {
+ let (mut super_range, mut sub_range) = (super_set.next(), sub_set.next());
+ let mut super_range_matched = true;
+ loop {
+ match (super_range, sub_range) {
+ // skip over irrelevant ranges
+ (Some(ra), Some(rb)) if ra.end <= rb.start && ra.start < rb.start => {
+ if !super_range_matched {
+ return false;
+ }
+ super_range_matched = false;
+ super_range = super_set.next();
+ }
+ (Some(ra), Some(rb)) => {
+ if ra.contains(rb) {
+ super_range_matched = true;
+ sub_range = sub_set.next();
+ } else {
+ return false;
+ }
+ }
+ (None, Some(_)) => {
+ // exhausted `super_set`, we can't match the reminder of `sub_set`
+ return false;
+ }
+ (_, None) => {
+ // no elements from `sub_sut` left to match, `super_set` contains `sub_set`
+ return super_set.next().is_none();
+ }
+ }
+ }
+}