From 47d00200fa0a7c0e9925acfb669ac8c3a3887298 Mon Sep 17 00:00:00 2001
From: Stepan Koltsov <stepan.koltsov@gmail.com>
Date: Mon, 18 Aug 2025 19:41:00 +0100
Subject: [PATCH] Reserve capacity in BytesMut::put

Copy-paste code from Vec::put
https://github.com/tokio-rs/bytes/blob/3e44f88f5fae6dfcd3aa0779b804b3ff18afdee3/src/buf/buf_mut.rs#L1645-L1646
---
 src/bytes_mut.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/bytes_mut.rs b/src/bytes_mut.rs
index ad3aa775d..d8d04d37b 100644
--- a/src/bytes_mut.rs
+++ b/src/bytes_mut.rs
@@ -1210,6 +1210,9 @@ unsafe impl BufMut for BytesMut {
                 Err(bytes) => self.extend_from_slice(&bytes),
             }
         } else {
+            // In case the src isn't contiguous, reserve upfront.
+            self.reserve(src.remaining());
+
             while src.has_remaining() {
                 let s = src.chunk();
                 let l = s.len();