From 5c64b957dd710cce27134cd480e0b83563c50d7f Mon Sep 17 00:00:00 2001
From: Alan Viverette <alanv@google.com>
Date: Sun, 28 Feb 2016 15:16:05 -0500
Subject: [PATCH] Use asset cookie in XML block cache key

Ensure we're using file paths from the correct package. Also cleans up
synchronization to avoid synchronizing on local variables which, while
not an issue in the current implementation, is generally unsafe.

Bug: 27313689
Change-Id: Ib8550909e7b02ea88d19ce2fc43756a16f9664ab
---
 core/java/android/content/res/Resources.java | 33 ++++++++++++--------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/core/java/android/content/res/Resources.java b/core/java/android/content/res/Resources.java
index a9150e88701f6..a54f40fc08147 100644
--- a/core/java/android/content/res/Resources.java
+++ b/core/java/android/content/res/Resources.java
@@ -68,6 +68,7 @@ import org.xmlpull.v1.XmlPullParserException;
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.util.Arrays;
 import java.util.Locale;
 
 /**
@@ -119,6 +120,9 @@ public class Resources {
     private static final LongSparseArray<android.content.res.ConstantState<ComplexColor>>
             sPreloadedComplexColors = new LongSparseArray<>();
 
+    /** Size of the cyclical cache used to map XML files to blocks. */
+    private static final int XML_BLOCK_CACHE_SIZE = 4;
+
     // Pool of TypedArrays targeted to this Resources object.
     final SynchronizedPool<TypedArray> mTypedArrayPool = new SynchronizedPool<>(5);
 
@@ -154,8 +158,9 @@ public class Resources {
 
     // Cyclical cache used for recently-accessed XML files.
     private int mLastCachedXmlBlockIndex = -1;
-    private final String[] mCachedXmlBlockFiles = new String[4];
-    private final XmlBlock[] mCachedXmlBlocks = new XmlBlock[4];
+    private final int[] mCachedXmlBlockCookies = new int[XML_BLOCK_CACHE_SIZE];
+    private final String[] mCachedXmlBlockFiles = new String[XML_BLOCK_CACHE_SIZE];
+    private final XmlBlock[] mCachedXmlBlocks = new XmlBlock[XML_BLOCK_CACHE_SIZE];
 
     final AssetManager mAssets;
     final ClassLoader mClassLoader;
@@ -2339,18 +2344,18 @@ public class Resources {
      * tools.
      */
     public final void flushLayoutCache() {
-        final String[] cachedXmlBlockFiles = mCachedXmlBlockFiles;
-        final XmlBlock[] cachedXmlBlocks = mCachedXmlBlocks;
-        synchronized (cachedXmlBlockFiles) {
-            final int num = cachedXmlBlockFiles.length;
-            for (int i = 0; i < num; i++) {
+        synchronized (mCachedXmlBlocks) {
+            Arrays.fill(mCachedXmlBlockCookies, 0);
+            Arrays.fill(mCachedXmlBlockFiles, null);
+
+            final XmlBlock[] cachedXmlBlocks = mCachedXmlBlocks;
+            for (int i = 0; i < XML_BLOCK_CACHE_SIZE; i++) {
                 final XmlBlock oldBlock = cachedXmlBlocks[i];
                 if (oldBlock != null) {
                     oldBlock.close();
                 }
-                cachedXmlBlockFiles[i] = null;
-                cachedXmlBlocks[i] = null;
             }
+            Arrays.fill(cachedXmlBlocks, null);
         }
     }
 
@@ -2852,13 +2857,14 @@ public class Resources {
             int assetCookie, @NonNull String type) throws NotFoundException {
         if (id != 0) {
             try {
-                final String[] cachedXmlBlockFiles = mCachedXmlBlockFiles;
-                final XmlBlock[] cachedXmlBlocks = mCachedXmlBlocks;
-                synchronized (cachedXmlBlockFiles) {
+                synchronized (mCachedXmlBlocks) {
+                    final int[] cachedXmlBlockCookies = mCachedXmlBlockCookies;
+                    final String[] cachedXmlBlockFiles = mCachedXmlBlockFiles;
+                    final XmlBlock[] cachedXmlBlocks = mCachedXmlBlocks;
                     // First see if this block is in our cache.
                     final int num = cachedXmlBlockFiles.length;
                     for (int i = 0; i < num; i++) {
-                        if (cachedXmlBlockFiles[i] != null
+                        if (cachedXmlBlockCookies[i] == assetCookie && cachedXmlBlockFiles[i] != null
                                 && cachedXmlBlockFiles[i].equals(file)) {
                             return cachedXmlBlocks[i].newParser();
                         }
@@ -2874,6 +2880,7 @@ public class Resources {
                         if (oldBlock != null) {
                             oldBlock.close();
                         }
+                        cachedXmlBlockCookies[pos] = assetCookie;
                         cachedXmlBlockFiles[pos] = file;
                         cachedXmlBlocks[pos] = block;
                         return block.newParser();