From 21d497b77366bdf90e6fcc9a35ee8f24344622ca Mon Sep 17 00:00:00 2001
From: Moritz Vetter <mv@3yourmind.com>
Date: Sat, 26 Feb 2022 15:50:09 +0100
Subject: [PATCH] refact: edit text in place in TextEdit::apply

---
 crates/text_edit/src/lib.rs | 30 ++++++++++++------------------
 1 file changed, 12 insertions(+), 18 deletions(-)

diff --git a/crates/text_edit/src/lib.rs b/crates/text_edit/src/lib.rs
index f478e4dcf576..f9d3ff9b07f5 100644
--- a/crates/text_edit/src/lib.rs
+++ b/crates/text_edit/src/lib.rs
@@ -90,28 +90,22 @@ impl TextEdit {
             _ => (),
         }
 
-        let mut total_len = TextSize::of(&*text);
+        let text_size = TextSize::of(&*text);
+        let mut total_len = text_size.clone();
         for indel in &self.indels {
             total_len += TextSize::of(&indel.insert);
-            total_len -= indel.delete.end() - indel.delete.start();
+            total_len -= indel.delete.len();
         }
-        let mut buf = String::with_capacity(total_len.into());
-        let mut prev = 0;
-        for indel in &self.indels {
-            let start: usize = indel.delete.start().into();
-            let end: usize = indel.delete.end().into();
-            if start > prev {
-                buf.push_str(&text[prev..start]);
-            }
-            buf.push_str(&indel.insert);
-            prev = end;
-        }
-        buf.push_str(&text[prev..text.len()]);
-        assert_eq!(TextSize::of(&buf), total_len);
 
-        // FIXME: figure out a way to mutate the text in-place or reuse the
-        // memory in some other way
-        *text = buf;
+        if let Some(additional) = total_len.checked_sub(text_size.into()) {
+            text.reserve(additional.into());
+        }
+
+        for indel in self.indels.iter().rev() {
+            indel.apply(text);
+        }
+
+        assert_eq!(TextSize::of(&*text), total_len);
     }
 
     pub fn union(&mut self, other: TextEdit) -> Result<(), TextEdit> {