From 79b6b02e31510663a44c5c1b0991bcba845162da Mon Sep 17 00:00:00 2001
From: Armin Braun <me@obrown.io>
Date: Tue, 4 Aug 2020 11:20:22 +0200
Subject: [PATCH] Fix Java11 Streams Class Copy

In https://github.com/elastic/elasticsearch/pull/60608 we missed
aligning the Java11 version of this class and this is breaking BwC
tests now. This commit aligns Java11 and Java8 versions of it again.
---
 .../core/internal/io/Streams.java             | 45 ++++++++++++++++---
 1 file changed, 38 insertions(+), 7 deletions(-)

diff --git a/libs/core/src/main/java11/org/elasticsearch/core/internal/io/Streams.java b/libs/core/src/main/java11/org/elasticsearch/core/internal/io/Streams.java
index 34b3785765d87..1fc8392609d82 100644
--- a/libs/core/src/main/java11/org/elasticsearch/core/internal/io/Streams.java
+++ b/libs/core/src/main/java11/org/elasticsearch/core/internal/io/Streams.java
@@ -32,26 +32,57 @@
  */
 public abstract class Streams {
 
+    private static final ThreadLocal<byte[]> buffer = ThreadLocal.withInitial(() -> new byte[8 * 1024]);
+
     /**
-     * Copy the contents of the given InputStream to the given OutputStream.
-     * Closes both streams when done.
+     * Copy the contents of the given InputStream to the given OutputStream. Optionally, closes both streams when done.
      *
-     * @param in  the stream to copy from
-     * @param out the stream to copy to
+     * @param in     the stream to copy from
+     * @param out    the stream to copy to
+     * @param close  whether to close both streams after copying
+     * @param buffer buffer to use for copying
      * @return the number of bytes copied
      * @throws IOException in case of I/O errors
      */
-    public static long copy(final InputStream in, final OutputStream out) throws IOException {
+    public static long copy(final InputStream in, final OutputStream out, byte[] buffer, boolean close) throws IOException {
         Exception err = null;
         try {
-            final long byteCount = in.transferTo(out);
+            long byteCount = 0;
+            int bytesRead;
+            while ((bytesRead = in.read(buffer)) != -1) {
+                out.write(buffer, 0, bytesRead);
+                byteCount += bytesRead;
+            }
             out.flush();
             return byteCount;
         } catch (IOException | RuntimeException e) {
             err = e;
             throw e;
         } finally {
-            IOUtils.close(err, in, out);
+            if (close) {
+                IOUtils.close(err, in, out);
+            }
         }
     }
+
+    /**
+     * @see #copy(InputStream, OutputStream, byte[], boolean)
+     */
+    public static long copy(final InputStream in, final OutputStream out, boolean close) throws IOException {
+        return copy(in, out, buffer.get(), close);
+    }
+
+    /**
+     * @see #copy(InputStream, OutputStream, byte[], boolean)
+     */
+    public static long copy(final InputStream in, final OutputStream out, byte[] buffer) throws IOException {
+        return copy(in, out, buffer, true);
+    }
+
+    /**
+     * @see #copy(InputStream, OutputStream, byte[], boolean)
+     */
+    public static long copy(final InputStream in, final OutputStream out) throws IOException {
+        return copy(in, out, buffer.get(), true);
+    }
 }