From 141157116444ecb6226b95a01dd3f1d6ab0ddb58 Mon Sep 17 00:00:00 2001
From: Michal Nazarewicz <mina86@mina86.com>
Date: Thu, 3 Aug 2023 17:49:26 +0200
Subject: [PATCH] =?UTF-8?q?ser:=20don=E2=80=99t=20unnecessarily=20allocate?=
 =?UTF-8?q?=20a=20String=20when=20serialising=20a=20character?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Use on-stack buffer to encode a character rather than allocating a new
String.  It’s faster and more memory-efficient.
---
 src/ser/map.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/ser/map.rs b/src/ser/map.rs
index c82c2ee3..be69edf5 100644
--- a/src/ser/map.rs
+++ b/src/ser/map.rs
@@ -166,7 +166,8 @@ impl<'a> ser::Serializer for MapKeySerializer<'a> {
     }
 
     fn serialize_char(self, value: char) -> Result<()> {
-        self.ser.serialize_str(&value.to_string())
+        let mut buf = [0u8; 4];
+        self.ser.serialize_str(value.encode_utf8(&mut buf))
     }
 
     fn serialize_bytes(self, _value: &[u8]) -> Result<()> {