types/json: replace binary.Read with binary.BigEndian.Uint16 (#23845)

types/json/binary_functions.go

@@ -137,11 +137,8 @@ func decodeEscapedUnicode(s []byte) (char [4]byte, size int, err error) {
 		// The unicode must can be represented in 2 bytes.
 		return char, 0, errors.Trace(err)
 	}
-	var unicode uint16
-	err = binary.Read(bytes.NewReader(char[0:2]), binary.BigEndian, &unicode)
-	if err != nil {
-		return char, 0, errors.Trace(err)
-	}
+
+	unicode := binary.BigEndian.Uint16(char[0:2])
 	size = utf8.RuneLen(rune(unicode))
 	utf8.EncodeRune(char[0:size], rune(unicode))
 	return

types/json/binary_functions_test.go

@@ -13,6 +13,8 @@
 package json
 
 import (
+	"testing"
+
 	. "github.com/pingcap/check"
 )
 
@@ -29,3 +31,10 @@ func (s *testJSONFuncSuite) TestdecodeEscapedUnicode(c *C) {
 	c.Assert(err, IsNil)
 
 }
+
+func BenchmarkDecodeEscapedUnicode(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		in := "597d"
+		decodeEscapedUnicode([]byte(in))
+	}
+}