cmds/idmap2/libidmap2/ResourceContainer.cpp - platform/frameworks/base - Git at Google

 /*
  * Copyright (C) 2021 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "idmap2/ResourceContainer.h"

 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>

 #include "androidfw/ApkAssets.h"
 #include "androidfw/AssetManager.h"
 #include "androidfw/Util.h"
 #include "idmap2/FabricatedOverlay.h"
 #include "idmap2/XmlParser.h"

 namespace android::idmap2 {
 namespace {
 #define REWRITE_PACKAGE(resid, package_id) \
   (((resid)&0x00ffffffU) | (((uint32_t)(package_id)) << 24U))

 #define EXTRACT_PACKAGE(resid) ((0xff000000 & (resid)) >> 24)

 constexpr ResourceId kAttrName = 0x01010003;
 constexpr ResourceId kAttrResourcesMap = 0x01010609;
 constexpr ResourceId kAttrTargetName = 0x0101044d;
 constexpr ResourceId kAttrTargetPackage = 0x01010021;

 // idmap version 0x01 naively assumes that the package to use is always the first ResTable_package
 // in the resources.arsc blob. In most cases, there is only a single ResTable_package anyway, so
 // this assumption tends to work out. That said, the correct thing to do is to scan
 // resources.arsc for a package with a given name as read from the package manifest instead of
 // relying on a hard-coded index. This however requires storing the package name in the idmap
 // header, which in turn requires incrementing the idmap version. Because the initial version of
 // idmap2 is compatible with idmap, this will have to wait for now.
 const LoadedPackage* GetPackageAtIndex0(const LoadedArsc* loaded_arsc) {
   const std::vector<std::unique_ptr<const LoadedPackage>>& packages = loaded_arsc->GetPackages();
   if (packages.empty()) {
     return nullptr;
   }
   return loaded_arsc->GetPackageById(packages[0]->GetPackageId());
 }

 Result<uint32_t> CalculateCrc(const ZipAssetsProvider* zip_assets) {
   constexpr const char* kResourcesArsc = "resources.arsc";
   std::optional<uint32_t> res_crc = zip_assets->GetCrc(kResourcesArsc);
   if (!res_crc) {
     return Error("failed to get CRC for '%s'", kResourcesArsc);
   }

   constexpr const char* kManifest = "AndroidManifest.xml";
   std::optional<uint32_t> man_crc = zip_assets->GetCrc(kManifest);
   if (!man_crc) {
     return Error("failed to get CRC for '%s'", kManifest);
   }

   return *res_crc ^ *man_crc;
 }

 Result<XmlParser> OpenXmlParser(const std::string& entry_path, const ZipAssetsProvider* zip) {
   auto manifest = zip->Open(entry_path);
   if (manifest == nullptr) {
     return Error("failed to find %s ", entry_path.c_str());
   }

   auto size = manifest->getLength();
   auto buffer = manifest->getIncFsBuffer(true /* aligned */).convert<uint8_t>();
   if (!buffer.verify(size)) {
     return Error("failed to read entire %s", entry_path.c_str());
   }

   return XmlParser::Create(buffer.unsafe_ptr(), size, true /* copyData */);
 }

 Result<XmlParser> OpenXmlParser(ResourceId id, const ZipAssetsProvider* zip,
                                 const AssetManager2* am) {
   const auto ref_table = am->GetDynamicRefTableForCookie(0);
   if (ref_table == nullptr) {
     return Error("failed to find dynamic ref table for cookie 0");
   }

   ref_table->lookupResourceId(&id);
   auto value = am->GetResource(id);
   if (!value.has_value()) {
     return Error("failed to find resource for id 0x%08x", id);
   }

   if (value->type != Res_value::TYPE_STRING) {
     return Error("resource for is 0x%08x is not a file", id);
   }

   auto string_pool = am->GetStringPoolForCookie(value->cookie);
   auto file = string_pool->string8ObjectAt(value->data);
   if (!file.has_value()) {
     return Error("failed to find string for index %d", value->data);
   }

   return OpenXmlParser(file->c_str(), zip);
 }

 Result<OverlayManifestInfo> ExtractOverlayManifestInfo(const ZipAssetsProvider* zip,
                                                        const std::string& name) {
   Result<XmlParser> xml = OpenXmlParser("AndroidManifest.xml", zip);
   if (!xml) {
     return xml.GetError();
   }

   auto manifest_it = xml->tree_iterator();
   if (manifest_it->event() != XmlParser::Event::START_TAG || manifest_it->name() != "manifest") {
     return Error("root element tag is not <manifest> in AndroidManifest.xml");
   }

   std::string package_name;
   if (auto result_str = manifest_it->GetAttributeStringValue("package")) {
     package_name = *result_str;
   } else {
     return result_str.GetError();
   }

   for (auto&& it : manifest_it) {
     if (it.event() != XmlParser::Event::START_TAG || it.name() != "overlay") {
       continue;
     }

     OverlayManifestInfo info{};
     info.package_name = package_name;
     if (auto result_str = it.GetAttributeStringValue(kAttrName, "android:name")) {
       if (*result_str != name) {
         // A value for android:name was found, but either a the name does not match the requested
         // name, or an <overlay> tag with no name was requested.
         continue;
       }
       info.name = *result_str;
     } else if (!name.empty()) {
       // This tag does not have a value for android:name, but an <overlay> tag with a specific name
       // has been requested.
       continue;
     }

     if (auto result_str = it.GetAttributeStringValue(kAttrTargetPackage, "android:targetPackage")) {
       info.target_package = *result_str;
     } else {
       return Error("android:targetPackage missing from <overlay> in AndroidManifest.xml");
     }

     if (auto result_str = it.GetAttributeStringValue(kAttrTargetName, "android:targetName")) {
       info.target_name = *result_str;
     }

     if (auto result_value = it.GetAttributeValue(kAttrResourcesMap, "android:resourcesMap")) {
       if (utils::IsReference((*result_value).dataType)) {
         info.resource_mapping = (*result_value).data;
       } else {
         return Error("android:resourcesMap is not a reference in AndroidManifest.xml");
       }
     }
     return info;
   }

   return Error("<overlay> with android:name \"%s\" missing from AndroidManifest.xml", name.c_str());
 }

 Result<OverlayData> CreateResourceMapping(ResourceId id, const ZipAssetsProvider* zip,
                                           const AssetManager2* overlay_am,
                                           const LoadedArsc* overlay_arsc,
                                           const LoadedPackage* overlay_package) {
   auto parser = OpenXmlParser(id, zip, overlay_am);
   if (!parser) {
     return parser.GetError();
   }

   OverlayData overlay_data{};
   const uint32_t string_pool_offset = overlay_arsc->GetStringPool()->size();
   const uint8_t package_id = overlay_package->GetPackageId();
   auto root_it = parser->tree_iterator();
   if (root_it->event() != XmlParser::Event::START_TAG || root_it->name() != "overlay") {
     return Error("root element is not <overlay> tag");
   }

   auto overlay_it_end = root_it.end();
   for (auto overlay_it = root_it.begin(); overlay_it != overlay_it_end; ++overlay_it) {
     if (overlay_it->event() == XmlParser::Event::BAD_DOCUMENT) {
       return Error("failed to parse overlay xml document");
     }

     if (overlay_it->event() != XmlParser::Event::START_TAG) {
       continue;
     }

     if (overlay_it->name() != "item") {
       return Error("unexpected tag <%s> in <overlay>", overlay_it->name().c_str());
     }

     Result<std::string> target_resource = overlay_it->GetAttributeStringValue("target");
     if (!target_resource) {
       return Error(R"(<item> tag missing expected attribute "target")");
     }

     Result<android::Res_value> overlay_resource = overlay_it->GetAttributeValue("value");
     if (!overlay_resource) {
       return Error(R"(<item> tag missing expected attribute "value")");
     }

     if (overlay_resource->dataType == Res_value::TYPE_STRING) {
       overlay_resource->data += string_pool_offset;
     }

     if (utils::IsReference(overlay_resource->dataType)) {
       // Only rewrite resources defined within the overlay package to their corresponding target
       // resource ids at runtime.
       bool rewrite_id = package_id == EXTRACT_PACKAGE(overlay_resource->data);
       overlay_data.pairs.emplace_back(OverlayData::Value{
           *target_resource, OverlayData::ResourceIdValue{overlay_resource->data, rewrite_id}});
     } else {
       overlay_data.pairs.emplace_back(
           OverlayData::Value{*target_resource, TargetValue{.data_type = overlay_resource->dataType,
                                                            .data_value = overlay_resource->data}});
     }
   }

   const auto& string_pool = parser->get_strings();
   const uint32_t string_pool_data_length = string_pool.bytes();
   overlay_data.string_pool_data = OverlayData::InlineStringPoolData{
       .data = std::unique_ptr<uint8_t[]>(new uint8_t[string_pool_data_length]),
       .data_length = string_pool_data_length,
       .string_pool_offset = string_pool_offset,
   };

   // Overlays should not be incrementally installed, so calling unsafe_ptr is fine here.
   memcpy(overlay_data.string_pool_data->data.get(), string_pool.data().unsafe_ptr(),
          string_pool_data_length);
   return overlay_data;
 }

 OverlayData CreateResourceMappingLegacy(const AssetManager2* overlay_am,
                                         const LoadedPackage* overlay_package) {
   OverlayData overlay_data{};
   for (const ResourceId overlay_resid : *overlay_package) {
     if (auto name = utils::ResToTypeEntryName(*overlay_am, overlay_resid)) {
       // Disable rewriting. Overlays did not support internal references before
       // android:resourcesMap. Do not introduce new behavior.
       overlay_data.pairs.emplace_back(OverlayData::Value{
           *name, OverlayData::ResourceIdValue{overlay_resid, false /* rewrite_id */}});
     }
   }
   return overlay_data;
 }

 struct ResState {
   std::unique_ptr<ApkAssets> apk_assets;
   const LoadedArsc* arsc;
   const LoadedPackage* package;
   std::unique_ptr<AssetManager2> am;
   ZipAssetsProvider* zip_assets;

   static Result<ResState> Initialize(std::unique_ptr<ZipAssetsProvider> zip) {
     ResState state;
     state.zip_assets = zip.get();
     if ((state.apk_assets = ApkAssets::Load(std::move(zip))) == nullptr) {
       return Error("failed to load apk asset");
     }

     if ((state.arsc = state.apk_assets->GetLoadedArsc()) == nullptr) {
       return Error("failed to retrieve loaded arsc");
     }

     if ((state.package = GetPackageAtIndex0(state.arsc)) == nullptr) {
       return Error("failed to retrieve loaded package at index 0");
     }

     state.am = std::make_unique<AssetManager2>();
     if (!state.am->SetApkAssets({state.apk_assets.get()})) {
       return Error("failed to create asset manager");
     }

     return state;
   }
 };

 }  // namespace

 struct ApkResourceContainer : public TargetResourceContainer, public OverlayResourceContainer {
   static Result<std::unique_ptr<ApkResourceContainer>> FromPath(const std::string& path);

   // inherited from TargetResourceContainer
   Result<bool> DefinesOverlayable() const override;
   Result<const android::OverlayableInfo*> GetOverlayableInfo(ResourceId id) const override;
   Result<ResourceId> GetResourceId(const std::string& name) const override;

   // inherited from OverlayResourceContainer
   Result<OverlayData> GetOverlayData(const OverlayManifestInfo& info) const override;
   Result<OverlayManifestInfo> FindOverlayInfo(const std::string& name) const override;

   // inherited from ResourceContainer
   Result<uint32_t> GetCrc() const override;
   Result<std::string> GetResourceName(ResourceId id) const override;
   const std::string& GetPath() const override;

   ~ApkResourceContainer() override = default;

  private:
   ApkResourceContainer(std::unique_ptr<ZipAssetsProvider> zip_assets, std::string path);

   Result<const ResState*> GetState() const;
   ZipAssetsProvider* GetZipAssets() const;

   mutable std::variant<std::unique_ptr<ZipAssetsProvider>, ResState> state_;
   std::string path_;
 };

 ApkResourceContainer::ApkResourceContainer(std::unique_ptr<ZipAssetsProvider> zip_assets,
                                            std::string path)
     : state_(std::move(zip_assets)), path_(std::move(path)) {
 }

 Result<std::unique_ptr<ApkResourceContainer>> ApkResourceContainer::FromPath(
     const std::string& path) {
   auto zip_assets = ZipAssetsProvider::Create(path, 0 /* flags */);
   if (zip_assets == nullptr) {
     return Error("failed to load zip assets");
   }
   return std::unique_ptr<ApkResourceContainer>(
       new ApkResourceContainer(std::move(zip_assets), path));
 }

 Result<const ResState*> ApkResourceContainer::GetState() const {
   if (auto state = std::get_if<ResState>(&state_); state != nullptr) {
     return state;
   }

   auto state =
       ResState::Initialize(std::move(std::get<std::unique_ptr<ZipAssetsProvider>>(state_)));
   if (!state) {
     return state.GetError();
   }

   state_ = std::move(*state);
   return &std::get<ResState>(state_);
 }

 ZipAssetsProvider* ApkResourceContainer::GetZipAssets() const {
   if (auto zip = std::get_if<std::unique_ptr<ZipAssetsProvider>>(&state_); zip != nullptr) {
     return zip->get();
   }
   return std::get<ResState>(state_).zip_assets;
 }

 Result<bool> ApkResourceContainer::DefinesOverlayable() const {
   auto state = GetState();
   if (!state) {
     return state.GetError();
   }
   return (*state)->package->DefinesOverlayable();
 }

 Result<const android::OverlayableInfo*> ApkResourceContainer::GetOverlayableInfo(
     ResourceId id) const {
   auto state = GetState();
   if (!state) {
     return state.GetError();
   }
   return (*state)->package->GetOverlayableInfo(id);
 }

 Result<OverlayManifestInfo> ApkResourceContainer::FindOverlayInfo(const std::string& name) const {
   return ExtractOverlayManifestInfo(GetZipAssets(), name);
 }

 Result<OverlayData> ApkResourceContainer::GetOverlayData(const OverlayManifestInfo& info) const {
   const auto state = GetState();
   if (!state) {
     return state.GetError();
   }

   if (info.resource_mapping != 0) {
     return CreateResourceMapping(info.resource_mapping, GetZipAssets(), (*state)->am.get(),
                                  (*state)->arsc, (*state)->package);
   }
   return CreateResourceMappingLegacy((*state)->am.get(), (*state)->package);
 }

 Result<uint32_t> ApkResourceContainer::GetCrc() const {
   return CalculateCrc(GetZipAssets());
 }

 const std::string& ApkResourceContainer::GetPath() const {
   return path_;
 }

 Result<ResourceId> ApkResourceContainer::GetResourceId(const std::string& name) const {
   auto state = GetState();
   if (!state) {
     return state.GetError();
   }
   auto id = (*state)->am->GetResourceId(name, "", (*state)->package->GetPackageName());
   if (!id.has_value()) {
     return Error("failed to find resource '%s'", name.c_str());
   }

   // Retrieve the compile-time resource id of the target resource.
   return REWRITE_PACKAGE(*id, (*state)->package->GetPackageId());
 }

 Result<std::string> ApkResourceContainer::GetResourceName(ResourceId id) const {
   auto state = GetState();
   if (!state) {
     return state.GetError();
   }
   return utils::ResToTypeEntryName(*(*state)->am, id);
 }

 Result<std::unique_ptr<TargetResourceContainer>> TargetResourceContainer::FromPath(
     std::string path) {
   auto result = ApkResourceContainer::FromPath(path);
   if (!result) {
     return result.GetError();
   }
   return std::unique_ptr<TargetResourceContainer>(result->release());
 }

 Result<std::unique_ptr<OverlayResourceContainer>> OverlayResourceContainer::FromPath(
     std::string path) {
   // Load the path as a fabricated overlay if the file magic indicates this is a fabricated overlay.
   if (android::IsFabricatedOverlay(path)) {
     auto result = FabricatedOverlayContainer::FromPath(path);
     if (!result) {
       return result.GetError();
     }
     return std::unique_ptr<OverlayResourceContainer>(result->release());
   }

   // Fallback to loading the container as an APK.
   auto result = ApkResourceContainer::FromPath(path);
   if (!result) {
     return result.GetError();
   }
   return std::unique_ptr<OverlayResourceContainer>(result->release());
 }

 }  // namespace android::idmap2
	/*
	* Copyright (C) 2021 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "idmap2/ResourceContainer.h"

	#include <memory>
	#include <string>
	#include <utility>
	#include <vector>

	#include "androidfw/ApkAssets.h"
	#include "androidfw/AssetManager.h"
	#include "androidfw/Util.h"
	#include "idmap2/FabricatedOverlay.h"
	#include "idmap2/XmlParser.h"

	namespace android::idmap2 {
	namespace {
	#define REWRITE_PACKAGE(resid, package_id) \
	(((resid)&0x00ffffffU) \| (((uint32_t)(package_id)) << 24U))

	#define EXTRACT_PACKAGE(resid) ((0xff000000 & (resid)) >> 24)

	constexpr ResourceId kAttrName = 0x01010003;
	constexpr ResourceId kAttrResourcesMap = 0x01010609;
	constexpr ResourceId kAttrTargetName = 0x0101044d;
	constexpr ResourceId kAttrTargetPackage = 0x01010021;

	// idmap version 0x01 naively assumes that the package to use is always the first ResTable_package
	// in the resources.arsc blob. In most cases, there is only a single ResTable_package anyway, so
	// this assumption tends to work out. That said, the correct thing to do is to scan
	// resources.arsc for a package with a given name as read from the package manifest instead of
	// relying on a hard-coded index. This however requires storing the package name in the idmap
	// header, which in turn requires incrementing the idmap version. Because the initial version of
	// idmap2 is compatible with idmap, this will have to wait for now.
	const LoadedPackage* GetPackageAtIndex0(const LoadedArsc* loaded_arsc) {
	const std::vector<std::unique_ptr<const LoadedPackage>>& packages = loaded_arsc->GetPackages();
	if (packages.empty()) {
	return nullptr;
	}
	return loaded_arsc->GetPackageById(packages[0]->GetPackageId());
	}

	Result<uint32_t> CalculateCrc(const ZipAssetsProvider* zip_assets) {
	constexpr const char* kResourcesArsc = "resources.arsc";
	std::optional<uint32_t> res_crc = zip_assets->GetCrc(kResourcesArsc);
	if (!res_crc) {
	return Error("failed to get CRC for '%s'", kResourcesArsc);
	}

	constexpr const char* kManifest = "AndroidManifest.xml";
	std::optional<uint32_t> man_crc = zip_assets->GetCrc(kManifest);
	if (!man_crc) {
	return Error("failed to get CRC for '%s'", kManifest);
	}

	return res_crc ^ man_crc;
	}

	Result<XmlParser> OpenXmlParser(const std::string& entry_path, const ZipAssetsProvider* zip) {
	auto manifest = zip->Open(entry_path);
	if (manifest == nullptr) {
	return Error("failed to find %s ", entry_path.c_str());
	}

	auto size = manifest->getLength();
	auto buffer = manifest->getIncFsBuffer(true /* aligned */).convert<uint8_t>();
	if (!buffer.verify(size)) {
	return Error("failed to read entire %s", entry_path.c_str());
	}

	return XmlParser::Create(buffer.unsafe_ptr(), size, true /* copyData */);
	}

	Result<XmlParser> OpenXmlParser(ResourceId id, const ZipAssetsProvider* zip,
	const AssetManager2* am) {
	const auto ref_table = am->GetDynamicRefTableForCookie(0);
	if (ref_table == nullptr) {
	return Error("failed to find dynamic ref table for cookie 0");
	}

	ref_table->lookupResourceId(&id);
	auto value = am->GetResource(id);
	if (!value.has_value()) {
	return Error("failed to find resource for id 0x%08x", id);
	}

	if (value->type != Res_value::TYPE_STRING) {
	return Error("resource for is 0x%08x is not a file", id);
	}

	auto string_pool = am->GetStringPoolForCookie(value->cookie);
	auto file = string_pool->string8ObjectAt(value->data);
	if (!file.has_value()) {
	return Error("failed to find string for index %d", value->data);
	}

	return OpenXmlParser(file->c_str(), zip);
	}

	Result<OverlayManifestInfo> ExtractOverlayManifestInfo(const ZipAssetsProvider* zip,
	const std::string& name) {
	Result<XmlParser> xml = OpenXmlParser("AndroidManifest.xml", zip);
	if (!xml) {
	return xml.GetError();
	}

	auto manifest_it = xml->tree_iterator();
	if (manifest_it->event() != XmlParser::Event::START_TAG \|\| manifest_it->name() != "manifest") {
	return Error("root element tag is not <manifest> in AndroidManifest.xml");
	}

	std::string package_name;
	if (auto result_str = manifest_it->GetAttributeStringValue("package")) {
	package_name = *result_str;
	} else {
	return result_str.GetError();
	}

	for (auto&& it : manifest_it) {
	if (it.event() != XmlParser::Event::START_TAG \|\| it.name() != "overlay") {
	continue;
	}

	OverlayManifestInfo info{};
	info.package_name = package_name;
	if (auto result_str = it.GetAttributeStringValue(kAttrName, "android:name")) {
	if (*result_str != name) {
	// A value for android:name was found, but either a the name does not match the requested
	// name, or an <overlay> tag with no name was requested.
	continue;
	}
	info.name = *result_str;
	} else if (!name.empty()) {
	// This tag does not have a value for android:name, but an <overlay> tag with a specific name
	// has been requested.
	continue;
	}

	if (auto result_str = it.GetAttributeStringValue(kAttrTargetPackage, "android:targetPackage")) {
	info.target_package = *result_str;
	} else {
	return Error("android:targetPackage missing from <overlay> in AndroidManifest.xml");
	}

	if (auto result_str = it.GetAttributeStringValue(kAttrTargetName, "android:targetName")) {
	info.target_name = *result_str;
	}

	if (auto result_value = it.GetAttributeValue(kAttrResourcesMap, "android:resourcesMap")) {
	if (utils::IsReference((*result_value).dataType)) {
	info.resource_mapping = (*result_value).data;
	} else {
	return Error("android:resourcesMap is not a reference in AndroidManifest.xml");
	}
	}
	return info;
	}

	return Error("<overlay> with android:name \"%s\" missing from AndroidManifest.xml", name.c_str());
	}

	Result<OverlayData> CreateResourceMapping(ResourceId id, const ZipAssetsProvider* zip,
	const AssetManager2* overlay_am,
	const LoadedArsc* overlay_arsc,
	const LoadedPackage* overlay_package) {
	auto parser = OpenXmlParser(id, zip, overlay_am);
	if (!parser) {
	return parser.GetError();
	}

	OverlayData overlay_data{};
	const uint32_t string_pool_offset = overlay_arsc->GetStringPool()->size();
	const uint8_t package_id = overlay_package->GetPackageId();
	auto root_it = parser->tree_iterator();
	if (root_it->event() != XmlParser::Event::START_TAG \|\| root_it->name() != "overlay") {
	return Error("root element is not <overlay> tag");
	}

	auto overlay_it_end = root_it.end();
	for (auto overlay_it = root_it.begin(); overlay_it != overlay_it_end; ++overlay_it) {
	if (overlay_it->event() == XmlParser::Event::BAD_DOCUMENT) {
	return Error("failed to parse overlay xml document");
	}

	if (overlay_it->event() != XmlParser::Event::START_TAG) {
	continue;
	}

	if (overlay_it->name() != "item") {
	return Error("unexpected tag <%s> in <overlay>", overlay_it->name().c_str());
	}

	Result<std::string> target_resource = overlay_it->GetAttributeStringValue("target");
	if (!target_resource) {
	return Error(R"(<item> tag missing expected attribute "target")");
	}

	Result<android::Res_value> overlay_resource = overlay_it->GetAttributeValue("value");
	if (!overlay_resource) {
	return Error(R"(<item> tag missing expected attribute "value")");
	}

	if (overlay_resource->dataType == Res_value::TYPE_STRING) {
	overlay_resource->data += string_pool_offset;
	}

	if (utils::IsReference(overlay_resource->dataType)) {
	// Only rewrite resources defined within the overlay package to their corresponding target
	// resource ids at runtime.
	bool rewrite_id = package_id == EXTRACT_PACKAGE(overlay_resource->data);
	overlay_data.pairs.emplace_back(OverlayData::Value{
	*target_resource, OverlayData::ResourceIdValue{overlay_resource->data, rewrite_id}});
	} else {
	overlay_data.pairs.emplace_back(
	OverlayData::Value{*target_resource, TargetValue{.data_type = overlay_resource->dataType,
	.data_value = overlay_resource->data}});
	}
	}

	const auto& string_pool = parser->get_strings();
	const uint32_t string_pool_data_length = string_pool.bytes();
	overlay_data.string_pool_data = OverlayData::InlineStringPoolData{
	.data = std::unique_ptr<uint8_t[]>(new uint8_t[string_pool_data_length]),
	.data_length = string_pool_data_length,
	.string_pool_offset = string_pool_offset,
	};

	// Overlays should not be incrementally installed, so calling unsafe_ptr is fine here.
	memcpy(overlay_data.string_pool_data->data.get(), string_pool.data().unsafe_ptr(),
	string_pool_data_length);
	return overlay_data;
	}

	OverlayData CreateResourceMappingLegacy(const AssetManager2* overlay_am,
	const LoadedPackage* overlay_package) {
	OverlayData overlay_data{};
	for (const ResourceId overlay_resid : *overlay_package) {
	if (auto name = utils::ResToTypeEntryName(*overlay_am, overlay_resid)) {
	// Disable rewriting. Overlays did not support internal references before
	// android:resourcesMap. Do not introduce new behavior.
	overlay_data.pairs.emplace_back(OverlayData::Value{
	name, OverlayData::ResourceIdValue{overlay_resid, false / rewrite_id */}});
	}
	}
	return overlay_data;
	}

	struct ResState {
	std::unique_ptr<ApkAssets> apk_assets;
	const LoadedArsc* arsc;
	const LoadedPackage* package;
	std::unique_ptr<AssetManager2> am;
	ZipAssetsProvider* zip_assets;

	static Result<ResState> Initialize(std::unique_ptr<ZipAssetsProvider> zip) {
	ResState state;
	state.zip_assets = zip.get();
	if ((state.apk_assets = ApkAssets::Load(std::move(zip))) == nullptr) {
	return Error("failed to load apk asset");
	}

	if ((state.arsc = state.apk_assets->GetLoadedArsc()) == nullptr) {
	return Error("failed to retrieve loaded arsc");
	}

	if ((state.package = GetPackageAtIndex0(state.arsc)) == nullptr) {
	return Error("failed to retrieve loaded package at index 0");
	}

	state.am = std::make_unique<AssetManager2>();
	if (!state.am->SetApkAssets({state.apk_assets.get()})) {
	return Error("failed to create asset manager");
	}

	return state;
	}
	};

	} // namespace

	struct ApkResourceContainer : public TargetResourceContainer, public OverlayResourceContainer {
	static Result<std::unique_ptr<ApkResourceContainer>> FromPath(const std::string& path);

	// inherited from TargetResourceContainer
	Result<bool> DefinesOverlayable() const override;
	Result<const android::OverlayableInfo*> GetOverlayableInfo(ResourceId id) const override;
	Result<ResourceId> GetResourceId(const std::string& name) const override;

	// inherited from OverlayResourceContainer
	Result<OverlayData> GetOverlayData(const OverlayManifestInfo& info) const override;
	Result<OverlayManifestInfo> FindOverlayInfo(const std::string& name) const override;

	// inherited from ResourceContainer
	Result<uint32_t> GetCrc() const override;
	Result<std::string> GetResourceName(ResourceId id) const override;
	const std::string& GetPath() const override;

	~ApkResourceContainer() override = default;

	private:
	ApkResourceContainer(std::unique_ptr<ZipAssetsProvider> zip_assets, std::string path);

	Result<const ResState*> GetState() const;
	ZipAssetsProvider* GetZipAssets() const;

	mutable std::variant<std::unique_ptr<ZipAssetsProvider>, ResState> state_;
	std::string path_;
	};

	ApkResourceContainer::ApkResourceContainer(std::unique_ptr<ZipAssetsProvider> zip_assets,
	std::string path)
	: state_(std::move(zip_assets)), path_(std::move(path)) {
	}

	Result<std::unique_ptr<ApkResourceContainer>> ApkResourceContainer::FromPath(
	const std::string& path) {
	auto zip_assets = ZipAssetsProvider::Create(path, 0 /* flags */);
	if (zip_assets == nullptr) {
	return Error("failed to load zip assets");
	}
	return std::unique_ptr<ApkResourceContainer>(
	new ApkResourceContainer(std::move(zip_assets), path));
	}

	Result<const ResState*> ApkResourceContainer::GetState() const {
	if (auto state = std::get_if<ResState>(&state_); state != nullptr) {
	return state;
	}

	auto state =
	ResState::Initialize(std::move(std::get<std::unique_ptr<ZipAssetsProvider>>(state_)));
	if (!state) {
	return state.GetError();
	}

	state_ = std::move(*state);
	return &std::get<ResState>(state_);
	}

	ZipAssetsProvider* ApkResourceContainer::GetZipAssets() const {
	if (auto zip = std::get_if<std::unique_ptr<ZipAssetsProvider>>(&state_); zip != nullptr) {
	return zip->get();
	}
	return std::get<ResState>(state_).zip_assets;
	}

	Result<bool> ApkResourceContainer::DefinesOverlayable() const {
	auto state = GetState();
	if (!state) {
	return state.GetError();
	}
	return (*state)->package->DefinesOverlayable();
	}

	Result<const android::OverlayableInfo*> ApkResourceContainer::GetOverlayableInfo(
	ResourceId id) const {
	auto state = GetState();
	if (!state) {
	return state.GetError();
	}
	return (*state)->package->GetOverlayableInfo(id);
	}

	Result<OverlayManifestInfo> ApkResourceContainer::FindOverlayInfo(const std::string& name) const {
	return ExtractOverlayManifestInfo(GetZipAssets(), name);
	}

	Result<OverlayData> ApkResourceContainer::GetOverlayData(const OverlayManifestInfo& info) const {
	const auto state = GetState();
	if (!state) {
	return state.GetError();
	}

	if (info.resource_mapping != 0) {
	return CreateResourceMapping(info.resource_mapping, GetZipAssets(), (*state)->am.get(),
	(state)->arsc, (state)->package);
	}
	return CreateResourceMappingLegacy((state)->am.get(), (state)->package);
	}

	Result<uint32_t> ApkResourceContainer::GetCrc() const {
	return CalculateCrc(GetZipAssets());
	}

	const std::string& ApkResourceContainer::GetPath() const {
	return path_;
	}

	Result<ResourceId> ApkResourceContainer::GetResourceId(const std::string& name) const {
	auto state = GetState();
	if (!state) {
	return state.GetError();
	}
	auto id = (state)->am->GetResourceId(name, "", (state)->package->GetPackageName());
	if (!id.has_value()) {
	return Error("failed to find resource '%s'", name.c_str());
	}

	// Retrieve the compile-time resource id of the target resource.
	return REWRITE_PACKAGE(id, (state)->package->GetPackageId());
	}

	Result<std::string> ApkResourceContainer::GetResourceName(ResourceId id) const {
	auto state = GetState();
	if (!state) {
	return state.GetError();
	}
	return utils::ResToTypeEntryName((state)->am, id);
	}

	Result<std::unique_ptr<TargetResourceContainer>> TargetResourceContainer::FromPath(
	std::string path) {
	auto result = ApkResourceContainer::FromPath(path);
	if (!result) {
	return result.GetError();
	}
	return std::unique_ptr<TargetResourceContainer>(result->release());
	}

	Result<std::unique_ptr<OverlayResourceContainer>> OverlayResourceContainer::FromPath(
	std::string path) {
	// Load the path as a fabricated overlay if the file magic indicates this is a fabricated overlay.
	if (android::IsFabricatedOverlay(path)) {
	auto result = FabricatedOverlayContainer::FromPath(path);
	if (!result) {
	return result.GetError();
	}
	return std::unique_ptr<OverlayResourceContainer>(result->release());
	}

	// Fallback to loading the container as an APK.
	auto result = ApkResourceContainer::FromPath(path);
	if (!result) {
	return result.GetError();
	}
	return std::unique_ptr<OverlayResourceContainer>(result->release());
	}

	} // namespace android::idmap2