Add range type to helix stdx

helix-core/src/diagnostic.rs

@@ -1,6 +1,7 @@
 //! LSP diagnostic utility types.
 use std::fmt;
 
+pub use helix_stdx::range::Range;
 use serde::{Deserialize, Serialize};
 
 /// Describes the severity level of a [`Diagnostic`].
@@ -19,19 +20,6 @@ impl Default for Severity {
     }
 }
 
-/// A range of `char`s within the text.
-#[derive(Debug, Clone, Copy, PartialOrd, Ord, PartialEq, Eq)]
-pub struct Range {
-    pub start: usize,
-    pub end: usize,
-}
-
-impl Range {
-    pub fn contains(self, pos: usize) -> bool {
-        (self.start..self.end).contains(&pos)
-    }
-}
-
 #[derive(Debug, Eq, Hash, PartialEq, Clone, Deserialize, Serialize)]
 pub enum NumberOrString {
     Number(i32),

helix-core/src/selection.rs

@@ -11,6 +11,7 @@ use crate::{
     movement::Direction,
     Assoc, ChangeSet, RopeGraphemes, RopeSlice,
 };
+use helix_stdx::range::is_subset;
 use helix_stdx::rope::{self, RopeSliceExt};
 use smallvec::{smallvec, SmallVec};
 use std::{borrow::Cow, iter, slice};
@@ -401,6 +402,15 @@ impl From<(usize, usize)> for Range {
     }
 }
 
+impl From<Range> for helix_stdx::Range {
+    fn from(range: Range) -> Self {
+        Self {
+            start: range.from(),
+            end: range.to(),
+        }
+    }
+}
+
 /// A selection consists of one or more selection ranges.
 /// invariant: A selection can never be empty (always contains at least primary range).
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -513,6 +523,10 @@ impl Selection {
         }
     }
 
+    pub fn range_bounds(&self) -> impl Iterator<Item = helix_stdx::Range> + '_ {
+        self.ranges.iter().map(|&range| range.into())
+    }
+
     pub fn primary_index(&self) -> usize {
         self.primary_index
     }
@@ -683,32 +697,9 @@ impl Selection {
         self.ranges.len()
     }
 
-    // returns true if self ⊇ other
+    /// returns true if self ⊇ other
     pub fn contains(&self, other: &Selection) -> bool {
-        let (mut iter_self, mut iter_other) = (self.iter(), other.iter());
+        is_subset::<true>(self.range_bounds(), other.range_bounds())
-        let (mut ele_self, mut ele_other) = (iter_self.next(), iter_other.next());
-
-        loop {
-            match (ele_self, ele_other) {
-                (Some(ra), Some(rb)) => {
-                    if !ra.contains_range(rb) {
-                        // `self` doesn't contain next element from `other`, advance `self`, we need to match all from `other`
-                        ele_self = iter_self.next();
-                    } else {
-                        // matched element from `other`, advance `other`
-                        ele_other = iter_other.next();
-                    };
-                }
-                (None, Some(_)) => {
-                    // exhausted `self`, we can't match the reminder of `other`
-                    return false;
-                }
-                (_, None) => {
-                    // no elements from `other` left to match, `self` contains `other`
-                    return true;
-                }
-            }
-        }
     }
 }
 

helix-stdx/src/lib.rs

@@ -1,4 +1,7 @@
 pub mod env;
 pub mod faccess;
 pub mod path;
+pub mod range;
 pub mod rope;
+
+pub use range::Range;

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 follwong invariants:
+/// * ranges must not overlap (but they can be adjecent)
+/// * 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();
+            }
+        }
+    }
+}