add unsafe string casting

json/json.go

@@ -87,7 +87,7 @@ func unquote(s []byte) (string, error) {
 	var ok bool
 	var t string
 	s, ok = unquoteBytes(s)
-	t = string(s)
+	t = castToString(s)
 	if !ok {
 		return "", errUnquote
 	}

json/string_unsafe.go

@@ -0,0 +1,27 @@
+//  Copyright 2025 Walter Schulze
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+
+package json
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+// castToString uses unsafe to cast a byte slice to a string without copying or allocating memory.
+func castToString(buf []byte) string {
+	header := (*reflect.SliceHeader)(unsafe.Pointer(&buf))
+	strHeader := reflect.StringHeader{Data: header.Data, Len: header.Len}
+	return *(*string)(unsafe.Pointer(&strHeader))
+}