Avoid copying fragments (#3136)

* Avoid copying fragments

* Add slice / slices method

* Better documentation for fragment and slice methods

1 files changed, 19 insertions, 1 deletions

diff --git a/helix-core/src/selection.rs b/helix-core/src/selection.rs
index 83bab5e3..59bd736e 100644
--- a/helix-core/src/selection.rs
+++ b/helix-core/src/selection.rs
@@ -222,9 +222,23 @@ impl Range {
 
     // groupAt
 
+    /// Returns the text inside this range given the text of the whole buffer.
+    ///
+    /// The returned `Cow` is a reference if the range of text is inside a single
+    /// chunk of the rope. Otherwise a copy of the text is returned. Consider
+    /// using `slice` instead if you do not need a `Cow` or `String` to avoid copying.
     #[inline]
     pub fn fragment<'a, 'b: 'a>(&'a self, text: RopeSlice<'b>) -> Cow<'b, str> {
-        text.slice(self.from()..self.to()).into()
+        self.slice(text).into()
+    }
+
+    /// Returns the text inside this range given the text of the whole buffer.
+    ///
+    /// The returned value is a reference to the passed slice. This method never
+    /// copies any contents.
+    #[inline]
+    pub fn slice<'a, 'b: 'a>(&'a self, text: RopeSlice<'b>) -> RopeSlice<'b> {
+        text.slice(self.from()..self.to())
     }
 
     //--------------------------------
@@ -548,6 +562,10 @@ impl Selection {
         self.ranges.iter().map(move |range| range.fragment(text))
     }
 
+    pub fn slices<'a>(&'a self, text: RopeSlice<'a>) -> impl Iterator<Item = RopeSlice> + 'a {
+        self.ranges.iter().map(move |range| range.slice(text))
+    }
+
     #[inline(always)]
     pub fn iter(&self) -> std::slice::Iter<'_, Range> {
         self.ranges.iter()