Add ResourceLoader API with .apk and .arsc support

ResourceLoaders allow inserting another .apk/.arsc into AssetManager's
resource resolution search. The effect is similar to overlays,
where a entry of >= config later in the path list will return that
ApkAsset's resource value instead.

Because loading from an .arsc is supported, which doesn't contain
any actual files, ResourceLoader exposes loadDrawable and
loadXmlResourceParser to allow an application load those files from
anywhere or create them in code.

The data being loaded is either pushed into an .apk or .arsc that
mocks itself as the package being "overlaid" and is passed in
through ResourcesProvider, an interface with static methods that
supports loading from a readable path on disk or a FileDescriptor.

The APIs are accessed through a Context's getResources(), which
has been changed to be unique per "Context-scope", which is usually
the lifetime of the Java object. The exception is that Activities
who get their Resources object persisted across recreations
maintain that logic for persisting ResourceLoaders.

Bug: 135270223

Test: atest FrameworksResourceLoaderTests

Change-Id: I6929f0828629ad39a21fa155e7fec73bd75eec7d

3 files changed, 40 insertions, 0 deletions

diff --git a/libs/androidfw/tests/LoadedArsc_test.cpp b/libs/androidfw/tests/LoadedArsc_test.cpp
index d58e8d20c8aa..fd57a92c216b 100644
--- a/libs/androidfw/tests/LoadedArsc_test.cpp
+++ b/libs/androidfw/tests/LoadedArsc_test.cpp
@@ -25,6 +25,7 @@
 #include "data/overlayable/R.h"
 #include "data/sparse/R.h"
 #include "data/styles/R.h"
+#include "data/system/R.h"
 
 namespace app = com::android::app;
 namespace basic = com::android::basic;
@@ -387,6 +388,39 @@ TEST(LoadedArscTest, GetOverlayableMap) {
   ASSERT_EQ(map.at("OverlayableResources2"), "overlay://com.android.overlayable");
 }
 
+TEST(LoadedArscTest, LoadCustomLoader) {
+  std::string contents;
+
+  std::unique_ptr<Asset>
+      asset = ApkAssets::CreateAssetFromFile(GetTestDataPath() + "/loader/resources.arsc");
+
+  MockLoadedIdmap loaded_idmap;
+  const StringPiece data(
+      reinterpret_cast<const char*>(asset->getBuffer(true /*wordAligned*/)),
+      asset->getLength());
+
+  std::unique_ptr<const LoadedArsc> loaded_arsc =
+      LoadedArsc::Load(data, nullptr, false, false, true);
+  ASSERT_THAT(loaded_arsc, NotNull());
+
+  const LoadedPackage* package =
+      loaded_arsc->GetPackageById(get_package_id(android::R::string::cancel));
+  ASSERT_THAT(package, NotNull());
+  EXPECT_THAT(package->GetPackageName(), StrEq("android"));
+  EXPECT_THAT(package->GetPackageId(), Eq(0x01));
+
+  const uint8_t type_index = get_type_id(android::R::string::cancel) - 1;
+  const uint16_t entry_index = get_entry_id(android::R::string::cancel);
+
+  const TypeSpec* type_spec = package->GetTypeSpecByTypeIndex(type_index);
+  ASSERT_THAT(type_spec, NotNull());
+  ASSERT_THAT(type_spec->type_count, Ge(1u));
+
+  const ResTable_type* type = type_spec->types[0];
+  ASSERT_THAT(type, NotNull());
+  ASSERT_THAT(LoadedPackage::GetEntry(type, entry_index), NotNull());
+}
+
 // structs with size fields (like Res_value, ResTable_entry) should be
 // backwards and forwards compatible (aka checking the size field against
 // sizeof(Res_value) might not be backwards compatible.
diff --git a/libs/androidfw/tests/data/loader/resources.arsc b/libs/androidfw/tests/data/loader/resources.arsc
new file mode 100644
index 000000000000..2c881f2cdfe5
--- /dev/null
+++ b/libs/androidfw/tests/data/loader/resources.arsc
diff --git a/libs/androidfw/tests/data/system/R.h b/libs/androidfw/tests/data/system/R.h
index becb38830fb3..374107484784 100644
--- a/libs/androidfw/tests/data/system/R.h
+++ b/libs/androidfw/tests/data/system/R.h
@@ -40,6 +40,12 @@ struct R {
       number = 0x01030000,  // sv
     };
   };
+
+  struct string {
+    enum : uint32_t {
+      cancel = 0x01040000,
+    };
+  };
 };
 
 }  // namespace android