Fix AssetManager2 isUpToDate check

This logic was lost in the AssetManager1 -> 2 migration.

The old AM1 checked the last modification time of the file
and compared it to a previously stored value. This re-adds the
logic to ApkAssets and fixes the checks in the JNI/Java layer.

Unfortunately I couldn't find a failing/practical case where
this check mattered. It only came up when diagnosing an issue
which ended up being unrelated.

Test: manually ran with other overlay changes

Change-Id: I758e4af1d32a9c03b2204a8a3a26e82b7e83feda

core/java/android/content/res/AssetManager.java

@@ -1263,12 +1263,19 @@ public final class AssetManager implements AutoCloseable {
      */
     @UnsupportedAppUsage
     public boolean isUpToDate() {
-        for (ApkAssets apkAssets : getApkAssets()) {
-            if (!apkAssets.isUpToDate()) {
+        synchronized (this) {
+            if (!mOpen) {
                 return false;
             }
+
+            for (ApkAssets apkAssets : mApkAssets) {
+                if (!apkAssets.isUpToDate()) {
+                    return false;
+                }
+            }
+
+            return true;
         }
-        return true;
     }
 
     /**

core/jni/android_content_res_ApkAssets.cpp

@@ -106,8 +106,7 @@ static jlong NativeGetStringBlock(JNIEnv* /*env*/, jclass /*clazz*/, jlong ptr)
 
 static jboolean NativeIsUpToDate(JNIEnv* /*env*/, jclass /*clazz*/, jlong ptr) {
   const ApkAssets* apk_assets = reinterpret_cast<const ApkAssets*>(ptr);
-  (void)apk_assets;
-  return JNI_TRUE;
+  return apk_assets->IsUpToDate() ? JNI_TRUE : JNI_FALSE;
 }
 
 static jlong NativeOpenXml(JNIEnv* env, jclass /*clazz*/, jlong ptr, jstring file_name) {

libs/androidfw/ApkAssets.cpp

@@ -29,6 +29,7 @@
 
 #include "androidfw/Asset.h"
 #include "androidfw/Idmap.h"
+#include "androidfw/misc.h"
 #include "androidfw/ResourceTypes.h"
 #include "androidfw/Util.h"
 
@@ -39,8 +40,10 @@ using base::unique_fd;
 
 static const std::string kResourcesArsc("resources.arsc");
 
-ApkAssets::ApkAssets(ZipArchiveHandle unmanaged_handle, const std::string& path)
-    : zip_handle_(unmanaged_handle, ::CloseArchive), path_(path) {
+ApkAssets::ApkAssets(ZipArchiveHandle unmanaged_handle,
+                     const std::string& path,
+                     time_t last_mod_time)
+    : zip_handle_(unmanaged_handle, ::CloseArchive), path_(path), last_mod_time_(last_mod_time) {
 }
 
 std::unique_ptr<const ApkAssets> ApkAssets::Load(const std::string& path, bool system) {
@@ -116,8 +119,10 @@ std::unique_ptr<const ApkAssets> ApkAssets::LoadImpl(
     return {};
   }
 
+  time_t last_mod_time = getFileModDate(path.c_str());
+
   // Wrap the handle in a unique_ptr so it gets automatically closed.
-  std::unique_ptr<ApkAssets> loaded_apk(new ApkAssets(unmanaged_handle, path));
+  std::unique_ptr<ApkAssets> loaded_apk(new ApkAssets(unmanaged_handle, path, last_mod_time));
 
   // Find the resource table.
   ::ZipString entry_name(kResourcesArsc.c_str());
@@ -248,4 +253,8 @@ bool ApkAssets::ForEachFile(const std::string& root_path,
   return result == -1;
 }
 
+bool ApkAssets::IsUpToDate() const {
+  return last_mod_time_ == getFileModDate(path_.c_str());
+}
+
 }  // namespace android

libs/androidfw/include/androidfw/ApkAssets.h

@@ -84,6 +84,8 @@ class ApkAssets {
     return idmap_asset_.get() != nullptr;
   }
 
+  bool IsUpToDate() const;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(ApkAssets);
 
@@ -95,12 +97,13 @@ class ApkAssets {
   // Creates an Asset from any file on the file system.
   static std::unique_ptr<Asset> CreateAssetFromFile(const std::string& path);
 
-  ApkAssets(ZipArchiveHandle unmanaged_handle, const std::string& path);
+  ApkAssets(ZipArchiveHandle unmanaged_handle, const std::string& path, time_t last_mod_time);
 
   using ZipArchivePtr = std::unique_ptr<ZipArchive, void(*)(ZipArchiveHandle)>;
 
   ZipArchivePtr zip_handle_;
   const std::string path_;
+  time_t last_mod_time_;
   std::unique_ptr<Asset> resources_asset_;
   std::unique_ptr<Asset> idmap_asset_;
   std::unique_ptr<const LoadedArsc> loaded_arsc_;