From 6f085692209f06c3427c475322786be06e45160f Mon Sep 17 00:00:00 2001
From: Rose Hogenson <rosehogenson@posteo.net>
Date: Sun, 7 Jan 2024 00:47:06 -0800
Subject: Avoid an extra copy.

---
 src/rope.rs | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/src/rope.rs b/src/rope.rs
index 6c1cad6..60a3fe8 100644
--- a/src/rope.rs
+++ b/src/rope.rs
@@ -73,7 +73,7 @@ enum Node {
 #[derive(Debug, Clone)]
 pub struct Rope(Node);
 
-fn leaf(buf: Vec<u8>) -> Rope {
+fn leaf(buf: &[u8]) -> Rope {
     let len = buf.len();
     return Rope(Node::Leaf(Leaf {
         buf: Rc::from(buf),
@@ -221,17 +221,13 @@ impl Rope {
                 let mut buf = Vec::new();
                 buf.extend_from_slice(&l.bytes());
                 buf.extend_from_slice(&r.bytes());
-                return Insert::Node(leaf(buf));
+                return Insert::Node(leaf(&buf));
             }
             if self.len() < MAX_NODE_SIZE / 2 || other.len() < MAX_NODE_SIZE / 2 {
                 let mut buf = Vec::new();
                 buf.extend_from_slice(&l.bytes());
                 buf.extend_from_slice(&r.bytes());
-                let mut buf1 = Vec::new();
-                buf1.extend_from_slice(&buf[..buf.len() / 2]);
-                let mut buf2 = Vec::new();
-                buf2.extend_from_slice(&buf[buf.len() / 2..]);
-                return Insert::Split(leaf(buf1), leaf(buf2));
+                return Insert::Split(leaf(&buf[..buf.len() / 2]), leaf(&buf[buf.len() / 2..]));
             }
         }
         if self.height() == other.height() {
@@ -290,7 +286,7 @@ impl Rope {
     pub fn insert(&self, pos: usize, c: u8) -> Rope {
         let res = self
             .slice(0, pos)
-            .concat(&leaf(vec![c]))
+            .concat(&leaf(&vec![c]))
             .concat(&self.slice(pos, self.len()));
         return res;
     }
@@ -319,7 +315,7 @@ impl Rope {
             Rope(Node::Branch(b)) => {
                 let mut start = start;
                 let mut end = end;
-                let mut slice = leaf(Vec::new());
+                let mut slice = leaf(&Vec::new());
                 for child in b.children() {
                     if start < child.len() {
                         slice = slice.concat(&child.slice(start, std::cmp::min(end, child.len())));
@@ -340,7 +336,7 @@ impl Rope {
     pub fn open(path: &Path) -> Result<Rope, Box<dyn Error>> {
         let mut f =
             File::open(path).map_err(|err| format!("open file {}: {}", path.display(), err))?;
-        let mut rope = leaf(Vec::new());
+        let mut rope = leaf(&Vec::new());
         loop {
             let mut buf = vec![0; MAX_NODE_SIZE];
             let n = match f.read(&mut buf) {
@@ -356,7 +352,7 @@ impl Rope {
                 break;
             }
             buf.truncate(n);
-            rope = rope.concat(&leaf(buf));
+            rope = rope.concat(&leaf(&buf));
         }
         return Ok(rope);
     }
-- 
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