Optimize memory allocation in appendRune function (#1988)

* Optimize memory allocation in appendRune function

* Add benchmark tests for appendRune function memory allocation

* remove function

* remove old

types/append.go

@@ -160,7 +160,9 @@ func appendRune(b []byte, r rune) []byte {
 	}
 	l := len(b)
 	if cap(b)-l < utf8.UTFMax {
-		b = append(b, make([]byte, utf8.UTFMax)...)
+		nb := make([]byte, l, 2*l+utf8.UTFMax)
+		copy(nb, b)
+		b = nb
 	}
 	n := utf8.EncodeRune(b[l:l+utf8.UTFMax], r)
 	return b[:l+n]

types/append_test.go

@@ -0,0 +1,17 @@
+package types
+
+import (
+	"testing"
+)
+
+func BenchmarkAppendRuneNew(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		b.StopTimer()
+		s := make([]byte, 0, 1024)
+		b.StartTimer()
+
+		for j := 0; j < 1000000; j++ {
+			s = appendRune(s, '世')
+		}
+	}
+}