More efficient serialization for ArraySeqOfBooleansWriting.sprayJson benchmark

Author: plokhotnyuk

jsoniter-scala-benchmark/shared/src/main/scala/com/github/plokhotnyuk/jsoniter_scala/benchmark/SprayFormats.scala

@@ -1272,9 +1272,15 @@ object SprayFormats extends DefaultJsonProtocol {
     new RootJsonFormat[ArraySeq[T]] {
       def read(json: JsValue): ArraySeq[T] = json match {
         case ja: JsArray =>
-          val b = ArraySeq.newBuilder[T]
-          ja.elements.foreach(e => b.addOne(e.convertTo[T]))
-          b.result()
+          val v = ja.elements
+          val a = new Array[T](v.size)
+          v.foreach {
+            var i = 0
+            e =>
+              a(i) = e.convertTo[T]
+              i += 1
+          }
+          ArraySeq.unsafeWrapArray(a)
         case _ => deserializationError(s"Expected JSON array")
       }