From 96b4f4d5acf673df777add1980344b4fd7a4ca05 Mon Sep 17 00:00:00 2001
From: anb <anb@dev.null>
Date: Mon, 9 Oct 2023 12:33:42 -0700
Subject: [PATCH] add Composer implementation for reference types

The use case is to share the underlying Composer buffer between
builders to avoid allocation, via a thread local variable for example.
Without the reference type implements, the ownership could be
transferred by memory swap operation, but that's not quite ideal. Plus
some methods like MessageBuilder::from_target would drop the Composer
on error, which makes it even difficult to share.
---
 src/base/wire.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/base/wire.rs b/src/base/wire.rs
index a1ef839e2..5e4f61bf4 100644
--- a/src/base/wire.rs
+++ b/src/base/wire.rs
@@ -46,6 +46,15 @@ impl Composer for bytes::BytesMut {}
 #[cfg(feature = "smallvec")]
 impl<A: smallvec::Array<Item = u8>> Composer for smallvec::SmallVec<A> {}
 
+impl<T: Composer> Composer for &mut T {
+    fn append_compressed_dname<N: ToDname + ?Sized>(
+        &mut self,
+        name: &N,
+    ) -> Result<(), Self::AppendError> {
+        Composer::append_compressed_dname(*self, name)
+    }
+}
+
 //------------ Compose -------------------------------------------------------
 
 /// An extension trait to add composing to foreign types.