From c3f57a85a503f43df28f6efb3e6363b543f7c4eb Mon Sep 17 00:00:00 2001
From: James Deng <james.deng@alumni.ubc.ca>
Date: Mon, 8 Sep 2025 05:48:44 -0700
Subject: [PATCH] Add non mut spare_capacity().

---
 src/bytes_mut.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/bytes_mut.rs b/src/bytes_mut.rs
index 333a0ae1e..03c0da493 100644
--- a/src/bytes_mut.rs
+++ b/src/bytes_mut.rs
@@ -1117,6 +1117,17 @@ impl BytesMut {
             slice::from_raw_parts_mut(ptr.cast(), len)
         }
     }
+
+    /// Returns the remaining spare capacity of the buffer.
+    #[inline]
+    pub fn spare_capacity(&self) -> &[MaybeUninit<u8>] {
+        unsafe {
+            let ptr = self.ptr.as_ptr().add(self.len);
+            let len = self.cap - self.len;
+
+            slice::from_raw_parts(ptr.cast(), len)
+        }
+    }
 }
 
 impl Drop for BytesMut {