Avoid copying fragments (#3136)

* Avoid copying fragments

* Add slice / slices method

* Better documentation for fragment and slice methods

4 files changed, 42 insertions, 18 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()
diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index 7e757ce1..cd79cfb8 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -766,7 +766,7 @@ fn trim_selections(cx: &mut Context) {
         .selection(view.id)
         .iter()
         .filter_map(|range| {
-            if range.is_empty() || range.fragment(text).chars().all(|ch| ch.is_whitespace()) {
+            if range.is_empty() || range.slice(text).chars().all(|ch| ch.is_whitespace()) {
                 return None;
             }
             let mut start = range.from();
@@ -1289,12 +1289,12 @@ fn replace(cx: &mut Context) {
 
 fn switch_case_impl<F>(cx: &mut Context, change_fn: F)
 where
-    F: Fn(Cow<str>) -> Tendril,
+    F: Fn(RopeSlice) -> Tendril,
 {
     let (view, doc) = current!(cx.editor);
     let selection = doc.selection(view.id);
     let transaction = Transaction::change_by_selection(doc.text(), selection, |range| {
-        let text: Tendril = change_fn(range.fragment(doc.text().slice(..)));
+        let text: Tendril = change_fn(range.slice(doc.text().slice(..)));
 
         (range.from(), range.to(), Some(text))
     });
@@ -1320,11 +1320,15 @@ fn switch_case(cx: &mut Context) {
 }
 
 fn switch_to_uppercase(cx: &mut Context) {
-    switch_case_impl(cx, |string| string.to_uppercase().into());
+    switch_case_impl(cx, |string| {
+        string.chunks().map(|chunk| chunk.to_uppercase()).collect()
+    });
 }
 
 fn switch_to_lowercase(cx: &mut Context) {
-    switch_case_impl(cx, |string| string.to_lowercase().into());
+    switch_case_impl(cx, |string| {
+        string.chunks().map(|chunk| chunk.to_lowercase()).collect()
+    });
 }
 
 pub fn scroll(cx: &mut Context, offset: usize, direction: Direction) {
@@ -3903,8 +3907,8 @@ fn rotate_selection_contents(cx: &mut Context, direction: Direction) {
 
     let selection = doc.selection(view.id);
     let mut fragments: Vec<_> = selection
-        .fragments(text)
-        .map(|fragment| Tendril::from(fragment.as_ref()))
+        .slices(text)
+        .map(|fragment| fragment.chunks().collect())
         .collect();
 
     let group = count
@@ -4510,8 +4514,8 @@ fn shell_keep_pipe(cx: &mut Context) {
             let text = doc.text().slice(..);
 
             for (i, range) in selection.ranges().iter().enumerate() {
-                let fragment = range.fragment(text);
-                let (_output, success) = match shell_impl(shell, input, Some(fragment.as_bytes())) {
+                let fragment = range.slice(text);
+                let (_output, success) = match shell_impl(shell, input, Some(fragment)) {
                     Ok(result) => result,
                     Err(err) => {
                         cx.editor.set_error(err.to_string());
@@ -4542,7 +4546,7 @@ fn shell_keep_pipe(cx: &mut Context) {
 fn shell_impl(
     shell: &[String],
     cmd: &str,
-    input: Option<&[u8]>,
+    input: Option<RopeSlice>,
 ) -> anyhow::Result<(Tendril, bool)> {
     use std::io::Write;
     use std::process::{Command, Stdio};
@@ -4564,7 +4568,9 @@ fn shell_impl(
     };
     if let Some(input) = input {
         let mut stdin = process.stdin.take().unwrap();
-        stdin.write_all(input)?;
+        for chunk in input.chunks() {
+            stdin.write_all(chunk.as_bytes())?;
+        }
     }
     let output = process.wait_with_output()?;
 
@@ -4593,8 +4599,8 @@ fn shell(cx: &mut compositor::Context, cmd: &str, behavior: &ShellBehavior) {
     let text = doc.text().slice(..);
 
     for range in selection.ranges() {
-        let fragment = range.fragment(text);
-        let (output, success) = match shell_impl(shell, cmd, pipe.then(|| fragment.as_bytes())) {
+        let fragment = range.slice(text);
+        let (output, success) = match shell_impl(shell, cmd, pipe.then(|| fragment)) {
             Ok(result) => result,
             Err(err) => {
                 cx.editor.set_error(err.to_string());
diff --git a/helix-term/src/commands/typed.rs b/helix-term/src/commands/typed.rs
index f6eedea9..dbf7cb24 100644
--- a/helix-term/src/commands/typed.rs
+++ b/helix-term/src/commands/typed.rs
@@ -1291,8 +1291,8 @@ fn sort_impl(
     let selection = doc.selection(view.id);
 
     let mut fragments: Vec<_> = selection
-        .fragments(text)
-        .map(|fragment| Tendril::from(fragment.as_ref()))
+        .slices(text)
+        .map(|fragment| fragment.chunks().collect())
         .collect();
 
     fragments.sort_by(match reverse {
diff --git a/helix-term/src/ui/editor.rs b/helix-term/src/ui/editor.rs
index f5598095..d99f1a4e 100644
--- a/helix-term/src/ui/editor.rs
+++ b/helix-term/src/ui/editor.rs
@@ -1029,8 +1029,8 @@ impl EditorView {
                 if doc
                     .selection(view.id)
                     .primary()
-                    .fragment(doc.text().slice(..))
-                    .width()
+                    .slice(doc.text().slice(..))
+                    .len_chars()
                     <= 1
                 {
                     return EventResult::Ignored(None);