use optimised ByteString.asInputStream

Update Http2FrameHpackSupport.scala

Update ByteStringInputStream.scala

revert Http2FrameHpackSupport change

Update ByteStringInputStream.scala

Update ByteStringInputStream.scala

http-core/src/main/scala/org/apache/pekko/http/impl/engine/http2/hpack/ByteStringInputStream.scala

@@ -14,6 +14,9 @@
 package org.apache.pekko.http.impl.engine.http2.hpack
 
 import java.io.{ ByteArrayInputStream, InputStream }
+import java.lang.invoke.{ MethodHandles, MethodType }
+
+import scala.util.Try
 
 import org.apache.pekko
 import pekko.annotation.InternalApi
@@ -24,10 +27,22 @@ import pekko.util.ByteString.ByteString1C
 @InternalApi
 private[http2] object ByteStringInputStream {
 
+  private lazy val byteStringInputStreamMethodTypeOpt = Try {
+    val lookup = MethodHandles.publicLookup()
+    val inputStreamMethodType = MethodType.methodType(classOf[InputStream])
+    lookup.findVirtual(classOf[ByteString], "asInputStream", inputStreamMethodType)
+  }.toOption
+
   def apply(bs: ByteString): InputStream =
+    byteStringInputStreamMethodTypeOpt.map { mh =>
+      mh.invoke(bs).asInstanceOf[InputStream]
+    }.getOrElse {
+      legacyConvert(bs)
+    }
+
+  private def legacyConvert(bs: ByteString): InputStream =
     bs match {
       case cs: ByteString1C =>
-        // TODO optimise, ByteString needs to expose InputStream (esp if array backed, nice!)
         new ByteArrayInputStream(cs.toArrayUnsafe())
       case _ =>
         // NOTE: We actually measured recently, and compact + use array was pretty good usually