From d8cc55d5cd3135b68ca38e11a0aa21f28ede98da Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sa=C5=A1a=20Tomi=C4=87?= <sasa.tomic@dfinity.org>
Date: Fri, 13 Mar 2026 09:38:36 +0100
Subject: [PATCH] perf: avoid copying concatenated type tables

Write serialized type-table entries directly into the output buffer instead of materializing an intermediate concatenated Vec.
---
 rust/candid/src/ser.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/rust/candid/src/ser.rs b/rust/candid/src/ser.rs
index 2ed78e7a9..8505ee514 100644
--- a/rust/candid/src/ser.rs
+++ b/rust/candid/src/ser.rs
@@ -427,7 +427,9 @@ impl TypeSerialize {
     #[doc(hidden)]
     pub fn serialize(&mut self) -> Result<()> {
         leb128_encode(&mut self.result, self.type_table.len() as u64)?;
-        self.result.append(&mut self.type_table.concat());
+        for entry in &self.type_table {
+            self.result.extend_from_slice(entry);
+        }
 
         leb128_encode(&mut self.result, self.args.len() as u64)?;
         let mut ty_encode = Vec::new();