From 8c37737cbc5d5a11d78defd330e532a6c3dcdaeb Mon Sep 17 00:00:00 2001
From: Tim Murray <timmurray@google.com>
Date: Thu, 24 Jun 2021 17:13:06 -0700
Subject: [PATCH] FileBridge: use a ByteBuffer for the temp buffer

Using a direct ByteBuffer allows the buffer to be passed to/from JNI
without intermediate copies.

Test: FileBridgeTests, apps get installed without allocation churn
Bug: 192020559
Change-Id: Ic5965c94ba14de6599af67d2e3bba33cd9996046
---
 core/java/android/os/FileBridge.java | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/core/java/android/os/FileBridge.java b/core/java/android/os/FileBridge.java
index 7b84575a89558..9dcdbf93f2961 100644
--- a/core/java/android/os/FileBridge.java
+++ b/core/java/android/os/FileBridge.java
@@ -32,6 +32,7 @@ import libcore.io.Streams;
 import java.io.FileDescriptor;
 import java.io.IOException;
 import java.io.OutputStream;
+import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 
 /**
@@ -95,9 +96,11 @@ public class FileBridge extends Thread {
 
     @Override
     public void run() {
-        final byte[] temp = new byte[8192];
+        final ByteBuffer tempBuffer = ByteBuffer.allocateDirect(8192);
+        final byte[] temp = tempBuffer.hasArray() ? tempBuffer.array() : new byte[8192];
         try {
-            while (IoBridge.read(mServer.getFileDescriptor(), temp, 0, MSG_LENGTH) == MSG_LENGTH) {
+            while (IoBridge.read(mServer.getFileDescriptor(), temp,
+                                 0, MSG_LENGTH) == MSG_LENGTH) {
                 final int cmd = Memory.peekInt(temp, 0, ByteOrder.BIG_ENDIAN);
                 if (cmd == CMD_WRITE) {
                     // Shuttle data into local file
@@ -138,7 +141,10 @@ public class FileBridge extends Thread {
     public static class FileBridgeOutputStream extends OutputStream {
         private final ParcelFileDescriptor mClientPfd;
         private final FileDescriptor mClient;
-        private final byte[] mTemp = new byte[MSG_LENGTH];
+        private final ByteBuffer mTempBuffer = ByteBuffer.allocateDirect(MSG_LENGTH);
+        private final byte[] mTemp = mTempBuffer.hasArray()
+                                     ? mTempBuffer.array()
+                                     : new byte[MSG_LENGTH];
 
         public FileBridgeOutputStream(ParcelFileDescriptor clientPfd) {
             mClientPfd = clientPfd;