perf: Make use of System.arraycopy directly. (#1001)

actor/src/main/scala-2.12/org/apache/pekko/util/ByteIterator.scala

@@ -123,7 +123,7 @@ object ByteIterator {
 
     def getBytes(xs: Array[Byte], offset: Int, n: Int): this.type = {
       if (n <= this.len) {
-        Array.copy(this.array, this.from, xs, offset, n)
+        System.arraycopy(this.array, this.from, xs, offset, n)
         this.drop(n)
       } else EmptyImmutableSeq.iterator.next()
     }

actor/src/main/scala-2.12/org/apache/pekko/util/ByteString.scala

@@ -1005,7 +1005,7 @@ object CompactByteString {
     if (copyLength == 0) empty
     else {
       val copyArray = new Array[Byte](copyLength)
-      Array.copy(array, copyOffset, copyArray, 0, copyLength)
+      System.arraycopy(array, copyOffset, copyArray, 0, copyLength)
       ByteString.ByteString1C(copyArray)
     }
   }
@@ -1065,15 +1065,15 @@ final class ByteStringBuilder extends Builder[Byte, ByteString] {
   private def clearTemp(): Unit = {
     if (_tempLength > 0) {
       val arr = new Array[Byte](_tempLength)
-      Array.copy(_temp, 0, arr, 0, _tempLength)
+      System.arraycopy(_temp, 0, arr, 0, _tempLength)
       _builder += ByteString1(arr)
       _tempLength = 0
     }
   }
 
   private def resizeTemp(size: Int): Unit = {
     val newtemp = new Array[Byte](size)
-    if (_tempLength > 0) Array.copy(_temp, 0, newtemp, 0, _tempLength)
+    if (_tempLength > 0) System.arraycopy(_temp, 0, newtemp, 0, _tempLength)
     _temp = newtemp
     _tempCapacity = _temp.length
   }
@@ -1257,7 +1257,7 @@ final class ByteStringBuilder extends Builder[Byte, ByteString] {
    * Add a number of Bytes from an array to this builder.
    */
   def putBytes(array: Array[Byte], start: Int, len: Int): this.type =
-    fillArray(len) { case (target, targetOffset) => Array.copy(array, start, target, targetOffset, len) }
+    fillArray(len) { case (target, targetOffset) => System.arraycopy(array, start, target, targetOffset, len) }
 
   /**
    * Add a number of Shorts from an array to this builder.

actor/src/main/scala-2.13/org/apache/pekko/util/ByteIterator.scala

@@ -135,7 +135,7 @@ object ByteIterator {
     @throws[NoSuchElementException]
     def getBytes(xs: Array[Byte], offset: Int, n: Int): this.type = {
       if (n <= this.len) {
-        Array.copy(this.array, this.from, xs, offset, n)
+        System.arraycopy(this.array, this.from, xs, offset, n)
         this.drop(n)
       } else throw new NoSuchElementException("next on empty iterator")
     }

actor/src/main/scala-2.13/org/apache/pekko/util/ByteString.scala

@@ -1055,7 +1055,7 @@ object CompactByteString {
     if (copyLength == 0) empty
     else {
       val copyArray = new Array[Byte](copyLength)
-      Array.copy(array, copyOffset, copyArray, 0, copyLength)
+      System.arraycopy(array, copyOffset, copyArray, 0, copyLength)
       ByteString.ByteString1C(copyArray)
     }
   }
@@ -1115,15 +1115,15 @@ final class ByteStringBuilder extends Builder[Byte, ByteString] {
   private def clearTemp(): Unit = {
     if (_tempLength > 0) {
       val arr = new Array[Byte](_tempLength)
-      Array.copy(_temp, 0, arr, 0, _tempLength)
+      System.arraycopy(_temp, 0, arr, 0, _tempLength)
       _builder += ByteString1(arr)
       _tempLength = 0
     }
   }
 
   private def resizeTemp(size: Int): Unit = {
     val newtemp = new Array[Byte](size)
-    if (_tempLength > 0) Array.copy(_temp, 0, newtemp, 0, _tempLength)
+    if (_tempLength > 0) System.arraycopy(_temp, 0, newtemp, 0, _tempLength)
     _temp = newtemp
     _tempCapacity = _temp.length
   }
@@ -1313,7 +1313,7 @@ final class ByteStringBuilder extends Builder[Byte, ByteString] {
    * Add a number of Bytes from an array to this builder.
    */
   def putBytes(array: Array[Byte], start: Int, len: Int): this.type =
-    fillArray(len) { case (target, targetOffset) => Array.copy(array, start, target, targetOffset, len) }
+    fillArray(len) { case (target, targetOffset) => System.arraycopy(array, start, target, targetOffset, len) }
 
   /**
    * Add a number of Shorts from an array to this builder.

actor/src/main/scala-3/org/apache/pekko/util/ByteIterator.scala

@@ -132,7 +132,7 @@ object ByteIterator {
     @throws[NoSuchElementException]
     def getBytes(xs: Array[Byte], offset: Int, n: Int): this.type = {
       if (n <= this.len) {
-        Array.copy(this.array, this.from, xs, offset, n)
+        System.arraycopy(this.array, this.from, xs, offset, n)
         this.drop(n)
       } else throw new NoSuchElementException("next on empty iterator")
     }

actor/src/main/scala-3/org/apache/pekko/util/ByteString.scala

@@ -1055,7 +1055,7 @@ object CompactByteString {
     if (copyLength == 0) empty
     else {
       val copyArray = new Array[Byte](copyLength)
-      Array.copy(array, copyOffset, copyArray, 0, copyLength)
+      System.arraycopy(array, copyOffset, copyArray, 0, copyLength)
       ByteString.ByteString1C(copyArray)
     }
   }
@@ -1115,15 +1115,15 @@ final class ByteStringBuilder extends Builder[Byte, ByteString] {
   private def clearTemp(): Unit = {
     if (_tempLength > 0) {
       val arr = new Array[Byte](_tempLength)
-      Array.copy(_temp, 0, arr, 0, _tempLength)
+      System.arraycopy(_temp, 0, arr, 0, _tempLength)
       _builder += ByteString1(arr)
       _tempLength = 0
     }
   }
 
   private def resizeTemp(size: Int): Unit = {
     val newtemp = new Array[Byte](size)
-    if (_tempLength > 0) Array.copy(_temp, 0, newtemp, 0, _tempLength)
+    if (_tempLength > 0) System.arraycopy(_temp, 0, newtemp, 0, _tempLength)
     _temp = newtemp
     _tempCapacity = _temp.length
   }
@@ -1313,7 +1313,7 @@ final class ByteStringBuilder extends Builder[Byte, ByteString] {
    * Add a number of Bytes from an array to this builder.
    */
   def putBytes(array: Array[Byte], start: Int, len: Int): this.type =
-    fillArray(len) { case (target, targetOffset) => Array.copy(array, start, target, targetOffset, len) }
+    fillArray(len) { case (target, targetOffset) => System.arraycopy(array, start, target, targetOffset, len) }
 
   /**
    * Add a number of Shorts from an array to this builder.

bench-jmh/src/main/scala/org/apache/pekko/util/ArrayCopyOf_Benchmark.scala

@@ -0,0 +1,56 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.pekko.util
+
+import org.openjdk.jmh.annotations._
+
+import java.util.concurrent.TimeUnit
+
+@State(Scope.Benchmark)
+@Measurement(timeUnit = TimeUnit.MILLISECONDS)
+class ArrayCopyOf_Benchmark {
+
+  var bs: Array[Byte] = _
+
+  @Param(Array("100", "1000"))
+  var kb = 0
+
+  /*
+    bench-jmh/jmh:run -f 1 -wi 10 -i 10 .*ArrayCopyOf_Benchmark.*
+   */
+
+  @Setup
+  def setup(): Unit = {
+    bs = Array.fill[Byte](1024 * kb)(1)
+  }
+
+  @Benchmark
+  def systemArrayCopy(): Unit = {
+    val len = bs.length
+    val buffer2 = new Array[Byte](bs.length)
+    System.arraycopy(bs, 0, buffer2, 0, len)
+  }
+
+  @Benchmark
+  def arrayCopyOf(): Unit = {
+    val len = bs.length
+    val buffer2 = new Array[Byte](bs.length)
+    Array.copy(bs, 0, buffer2, 0, len)
+  }
+
+}