tools/aapt2/process/SymbolTable.cpp - platform/frameworks/base - Gitiles

 /*
  * Copyright (C) 2015 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 "process/SymbolTable.h"

 #include <iostream>

 #include "android-base/logging.h"
 #include "android-base/stringprintf.h"
 #include "androidfw/AssetManager.h"
 #include "androidfw/ResourceTypes.h"

 #include "ConfigDescription.h"
 #include "NameMangler.h"
 #include "Resource.h"
 #include "ResourceUtils.h"
 #include "ValueVisitor.h"
 #include "util/Util.h"

 using ::android::StringPiece;
 using ::android::StringPiece16;

 namespace aapt {

 SymbolTable::SymbolTable(NameMangler* mangler)
     : mangler_(mangler),
       delegate_(util::make_unique<DefaultSymbolTableDelegate>()),
       cache_(200),
       id_cache_(200) {
 }

 void SymbolTable::SetDelegate(std::unique_ptr<ISymbolTableDelegate> delegate) {
   CHECK(delegate != nullptr) << "can't set a nullptr delegate";
   delegate_ = std::move(delegate);

   // Clear the cache in case this delegate changes the order of lookup.
   cache_.clear();
 }

 void SymbolTable::AppendSource(std::unique_ptr<ISymbolSource> source) {
   sources_.push_back(std::move(source));

   // We do not clear the cache, because sources earlier in the list take
   // precedent.
 }

 void SymbolTable::PrependSource(std::unique_ptr<ISymbolSource> source) {
   sources_.insert(sources_.begin(), std::move(source));

   // We must clear the cache in case we did a lookup before adding this
   // resource.
   cache_.clear();
 }

 const SymbolTable::Symbol* SymbolTable::FindByName(const ResourceName& name) {
   const ResourceName* name_with_package = &name;

   // Fill in the package name if necessary.
   // If there is no package in `name`, we will need to copy the ResourceName
   // and store it somewhere; we use the Maybe<> class to reserve storage.
   Maybe<ResourceName> name_with_package_impl;
   if (name.package.empty()) {
     name_with_package_impl = ResourceName(mangler_->GetTargetPackageName(), name.type, name.entry);
     name_with_package = &name_with_package_impl.value();
   }

   // We store the name unmangled in the cache, so look it up as-is.
   if (const std::shared_ptr<Symbol>& s = cache_.get(*name_with_package)) {
     return s.get();
   }

   // The name was not found in the cache. Mangle it (if necessary) and find it in our sources.
   // Again, here we use a Maybe<> object to reserve storage if we need to mangle.
   const ResourceName* mangled_name = name_with_package;
   Maybe<ResourceName> mangled_name_impl;
   if (mangler_->ShouldMangle(name_with_package->package)) {
     mangled_name_impl = mangler_->MangleName(*name_with_package);
     mangled_name = &mangled_name_impl.value();
   }

   std::unique_ptr<Symbol> symbol = delegate_->FindByName(*mangled_name, sources_);
   if (symbol == nullptr) {
     return nullptr;
   }

   // Take ownership of the symbol into a shared_ptr. We do this because
   // LruCache doesn't support unique_ptr.
   std::shared_ptr<Symbol> shared_symbol(std::move(symbol));

   // Since we look in the cache with the unmangled, but package prefixed
   // name, we must put the same name into the cache.
   cache_.put(*name_with_package, shared_symbol);

   if (shared_symbol->id) {
     // The symbol has an ID, so we can also cache this!
     id_cache_.put(shared_symbol->id.value(), shared_symbol);
   }

   // Returns the raw pointer. Callers are not expected to hold on to this
   // between calls to Find*.
   return shared_symbol.get();
 }

 const SymbolTable::Symbol* SymbolTable::FindById(const ResourceId& id) {
   if (const std::shared_ptr<Symbol>& s = id_cache_.get(id)) {
     return s.get();
   }

   // We did not find it in the cache, so look through the sources.
   std::unique_ptr<Symbol> symbol = delegate_->FindById(id, sources_);
   if (symbol == nullptr) {
     return nullptr;
   }

   // Take ownership of the symbol into a shared_ptr. We do this because LruCache
   // doesn't support unique_ptr.
   std::shared_ptr<Symbol> shared_symbol(std::move(symbol));
   id_cache_.put(id, shared_symbol);

   // Returns the raw pointer. Callers are not expected to hold on to this
   // between calls to Find*.
   return shared_symbol.get();
 }

 const SymbolTable::Symbol* SymbolTable::FindByReference(const Reference& ref) {
   // First try the ID. This is because when we lookup by ID, we only fill in the ID cache.
   // Looking up by name fills in the name and ID cache. So a cache miss will cause a failed
   // ID lookup, then a successful name lookup. Subsequent look ups will hit immediately
   // because the ID is cached too.
   //
   // If we looked up by name first, a cache miss would mean we failed to lookup by name, then
   // succeeded to lookup by ID. Subsequent lookups will miss then hit.
   const SymbolTable::Symbol* symbol = nullptr;
   if (ref.id) {
     symbol = FindById(ref.id.value());
   }

   if (ref.name && !symbol) {
     symbol = FindByName(ref.name.value());
   }
   return symbol;
 }

 std::unique_ptr<SymbolTable::Symbol> DefaultSymbolTableDelegate::FindByName(
     const ResourceName& name, const std::vector<std::unique_ptr<ISymbolSource>>& sources) {
   for (auto& source : sources) {
     std::unique_ptr<SymbolTable::Symbol> symbol = source->FindByName(name);
     if (symbol) {
       return symbol;
     }
   }
   return {};
 }

 std::unique_ptr<SymbolTable::Symbol> DefaultSymbolTableDelegate::FindById(
     ResourceId id, const std::vector<std::unique_ptr<ISymbolSource>>& sources) {
   for (auto& source : sources) {
     std::unique_ptr<SymbolTable::Symbol> symbol = source->FindById(id);
     if (symbol) {
       return symbol;
     }
   }
   return {};
 }

 std::unique_ptr<SymbolTable::Symbol> ResourceTableSymbolSource::FindByName(
     const ResourceName& name) {
   Maybe<ResourceTable::SearchResult> result = table_->FindResource(name);
   if (!result) {
     if (name.type == ResourceType::kAttr) {
       // Recurse and try looking up a private attribute.
       return FindByName(ResourceName(name.package, ResourceType::kAttrPrivate, name.entry));
     }
     return {};
   }

   ResourceTable::SearchResult sr = result.value();

   std::unique_ptr<SymbolTable::Symbol> symbol = util::make_unique<SymbolTable::Symbol>();
   symbol->is_public = (sr.entry->visibility.level == Visibility::Level::kPublic);

   if (sr.package->id && sr.type->id && sr.entry->id) {
     symbol->id = ResourceId(sr.package->id.value(), sr.type->id.value(), sr.entry->id.value());
   }

   if (name.type == ResourceType::kAttr || name.type == ResourceType::kAttrPrivate) {
     const ConfigDescription kDefaultConfig;
     ResourceConfigValue* config_value = sr.entry->FindValue(kDefaultConfig);
     if (config_value) {
       // This resource has an Attribute.
       if (Attribute* attr = ValueCast<Attribute>(config_value->value.get())) {
         symbol->attribute = std::make_shared<Attribute>(*attr);
       } else {
         return {};
       }
     }
   }
   return symbol;
 }

 bool AssetManagerSymbolSource::AddAssetPath(const StringPiece& path) {
   int32_t cookie = 0;
   return assets_.addAssetPath(android::String8(path.data(), path.size()), &cookie);
 }

 std::map<size_t, std::string> AssetManagerSymbolSource::GetAssignedPackageIds() const {
   std::map<size_t, std::string> package_map;
   const android::ResTable& table = assets_.getResources(false);
   const size_t package_count = table.getBasePackageCount();
   for (size_t i = 0; i < package_count; i++) {
     package_map[table.getBasePackageId(i)] =
         util::Utf16ToUtf8(android::StringPiece16(table.getBasePackageName(i).string()));
   }
   return package_map;
 }

 static std::unique_ptr<SymbolTable::Symbol> LookupAttributeInTable(
     const android::ResTable& table, ResourceId id) {
   // Try as a bag.
   const android::ResTable::bag_entry* entry;
   ssize_t count = table.lockBag(id.id, &entry);
   if (count < 0) {
     table.unlockBag(entry);
     return nullptr;
   }

   // We found a resource.
   std::unique_ptr<SymbolTable::Symbol> s = util::make_unique<SymbolTable::Symbol>(id);

   // Check to see if it is an attribute.
   for (size_t i = 0; i < (size_t)count; i++) {
     if (entry[i].map.name.ident == android::ResTable_map::ATTR_TYPE) {
       s->attribute = std::make_shared<Attribute>(entry[i].map.value.data);
       break;
     }
   }

   if (s->attribute) {
     for (size_t i = 0; i < (size_t)count; i++) {
       const android::ResTable_map& map_entry = entry[i].map;
       if (Res_INTERNALID(map_entry.name.ident)) {
         switch (map_entry.name.ident) {
           case android::ResTable_map::ATTR_MIN:
             s->attribute->min_int = static_cast<int32_t>(map_entry.value.data);
             break;
           case android::ResTable_map::ATTR_MAX:
             s->attribute->max_int = static_cast<int32_t>(map_entry.value.data);
             break;
         }
         continue;
       }

       android::ResTable::resource_name entry_name;
       if (!table.getResourceName(map_entry.name.ident, false, &entry_name)) {
         table.unlockBag(entry);
         return nullptr;
       }

       Maybe<ResourceName> parsed_name = ResourceUtils::ToResourceName(entry_name);
       if (!parsed_name) {
         return nullptr;
       }

       Attribute::Symbol symbol;
       symbol.symbol.name = parsed_name.value();
       symbol.symbol.id = ResourceId(map_entry.name.ident);
       symbol.value = map_entry.value.data;
       s->attribute->symbols.push_back(std::move(symbol));
     }
   }
   table.unlockBag(entry);
   return s;
 }

 std::unique_ptr<SymbolTable::Symbol> AssetManagerSymbolSource::FindByName(
     const ResourceName& name) {
   const android::ResTable& table = assets_.getResources(false);

   const std::u16string package16 = util::Utf8ToUtf16(name.package);
   const std::u16string type16 = util::Utf8ToUtf16(to_string(name.type));
   const std::u16string entry16 = util::Utf8ToUtf16(name.entry);
   const std::u16string mangled_entry16 =
       util::Utf8ToUtf16(NameMangler::MangleEntry(name.package, name.entry));

   uint32_t type_spec_flags;
   ResourceId res_id;

   // There can be mangled resources embedded within other packages. Here we will
   // look into each package and look-up the mangled name until we find the resource.
   const size_t count = table.getBasePackageCount();
   for (size_t i = 0; i < count; i++) {
     const android::String16 package_name = table.getBasePackageName(i);
     StringPiece16 real_package16 = package16;
     StringPiece16 real_entry16 = entry16;
     std::u16string scratch_entry16;
     if (StringPiece16(package_name) != package16) {
       real_entry16 = mangled_entry16;
       real_package16 = package_name.string();
     }

     type_spec_flags = 0;
     res_id = table.identifierForName(real_entry16.data(), real_entry16.size(), type16.data(),
                                      type16.size(), real_package16.data(), real_package16.size(),
                                      &type_spec_flags);
     if (res_id.is_valid()) {
       break;
     }
   }

   if (!res_id.is_valid()) {
     return {};
   }

   std::unique_ptr<SymbolTable::Symbol> s;
   if (name.type == ResourceType::kAttr) {
     s = LookupAttributeInTable(table, res_id);
   } else {
     s = util::make_unique<SymbolTable::Symbol>();
     s->id = res_id;
   }

   if (s) {
     s->is_public = (type_spec_flags & android::ResTable_typeSpec::SPEC_PUBLIC) != 0;
     return s;
   }
   return {};
 }

 static Maybe<ResourceName> GetResourceName(const android::ResTable& table,
                                            ResourceId id) {
   android::ResTable::resource_name res_name = {};
   if (!table.getResourceName(id.id, true, &res_name)) {
     return {};
   }
   return ResourceUtils::ToResourceName(res_name);
 }

 std::unique_ptr<SymbolTable::Symbol> AssetManagerSymbolSource::FindById(
     ResourceId id) {
   if (!id.is_valid()) {
     // Exit early and avoid the error logs from AssetManager.
     return {};
   }

   const android::ResTable& table = assets_.getResources(false);
   Maybe<ResourceName> maybe_name = GetResourceName(table, id);
   if (!maybe_name) {
     return {};
   }

   uint32_t type_spec_flags = 0;
   table.getResourceFlags(id.id, &type_spec_flags);

   std::unique_ptr<SymbolTable::Symbol> s;
   if (maybe_name.value().type == ResourceType::kAttr) {
     s = LookupAttributeInTable(table, id);
   } else {
     s = util::make_unique<SymbolTable::Symbol>();
     s->id = id;
   }

   if (s) {
     s->is_public = (type_spec_flags & android::ResTable_typeSpec::SPEC_PUBLIC) != 0;
     return s;
   }
   return {};
 }

 std::unique_ptr<SymbolTable::Symbol> AssetManagerSymbolSource::FindByReference(
     const Reference& ref) {
   // AssetManager always prefers IDs.
   if (ref.id) {
     return FindById(ref.id.value());
   } else if (ref.name) {
     return FindByName(ref.name.value());
   }
   return {};
 }

 }  // namespace aapt
	/*
	* Copyright (C) 2015 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 "process/SymbolTable.h"

	#include <iostream>

	#include "android-base/logging.h"
	#include "android-base/stringprintf.h"
	#include "androidfw/AssetManager.h"
	#include "androidfw/ResourceTypes.h"

	#include "ConfigDescription.h"
	#include "NameMangler.h"
	#include "Resource.h"
	#include "ResourceUtils.h"
	#include "ValueVisitor.h"
	#include "util/Util.h"

	using ::android::StringPiece;
	using ::android::StringPiece16;

	namespace aapt {

	SymbolTable::SymbolTable(NameMangler* mangler)
	: mangler_(mangler),
	delegate_(util::make_unique<DefaultSymbolTableDelegate>()),
	cache_(200),
	id_cache_(200) {
	}

	void SymbolTable::SetDelegate(std::unique_ptr<ISymbolTableDelegate> delegate) {
	CHECK(delegate != nullptr) << "can't set a nullptr delegate";
	delegate_ = std::move(delegate);

	// Clear the cache in case this delegate changes the order of lookup.
	cache_.clear();
	}

	void SymbolTable::AppendSource(std::unique_ptr<ISymbolSource> source) {
	sources_.push_back(std::move(source));

	// We do not clear the cache, because sources earlier in the list take
	// precedent.
	}

	void SymbolTable::PrependSource(std::unique_ptr<ISymbolSource> source) {
	sources_.insert(sources_.begin(), std::move(source));

	// We must clear the cache in case we did a lookup before adding this
	// resource.
	cache_.clear();
	}

	const SymbolTable::Symbol* SymbolTable::FindByName(const ResourceName& name) {
	const ResourceName* name_with_package = &name;

	// Fill in the package name if necessary.
	// If there is no package in `name`, we will need to copy the ResourceName
	// and store it somewhere; we use the Maybe<> class to reserve storage.
	Maybe<ResourceName> name_with_package_impl;
	if (name.package.empty()) {
	name_with_package_impl = ResourceName(mangler_->GetTargetPackageName(), name.type, name.entry);
	name_with_package = &name_with_package_impl.value();
	}

	// We store the name unmangled in the cache, so look it up as-is.
	if (const std::shared_ptr<Symbol>& s = cache_.get(*name_with_package)) {
	return s.get();
	}

	// The name was not found in the cache. Mangle it (if necessary) and find it in our sources.
	// Again, here we use a Maybe<> object to reserve storage if we need to mangle.
	const ResourceName* mangled_name = name_with_package;
	Maybe<ResourceName> mangled_name_impl;
	if (mangler_->ShouldMangle(name_with_package->package)) {
	mangled_name_impl = mangler_->MangleName(*name_with_package);
	mangled_name = &mangled_name_impl.value();
	}

	std::unique_ptr<Symbol> symbol = delegate_->FindByName(*mangled_name, sources_);
	if (symbol == nullptr) {
	return nullptr;
	}

	// Take ownership of the symbol into a shared_ptr. We do this because
	// LruCache doesn't support unique_ptr.
	std::shared_ptr<Symbol> shared_symbol(std::move(symbol));

	// Since we look in the cache with the unmangled, but package prefixed
	// name, we must put the same name into the cache.
	cache_.put(*name_with_package, shared_symbol);

	if (shared_symbol->id) {
	// The symbol has an ID, so we can also cache this!
	id_cache_.put(shared_symbol->id.value(), shared_symbol);
	}

	// Returns the raw pointer. Callers are not expected to hold on to this
	// between calls to Find*.
	return shared_symbol.get();
	}

	const SymbolTable::Symbol* SymbolTable::FindById(const ResourceId& id) {
	if (const std::shared_ptr<Symbol>& s = id_cache_.get(id)) {
	return s.get();
	}

	// We did not find it in the cache, so look through the sources.
	std::unique_ptr<Symbol> symbol = delegate_->FindById(id, sources_);
	if (symbol == nullptr) {
	return nullptr;
	}

	// Take ownership of the symbol into a shared_ptr. We do this because LruCache
	// doesn't support unique_ptr.
	std::shared_ptr<Symbol> shared_symbol(std::move(symbol));
	id_cache_.put(id, shared_symbol);

	// Returns the raw pointer. Callers are not expected to hold on to this
	// between calls to Find*.
	return shared_symbol.get();
	}

	const SymbolTable::Symbol* SymbolTable::FindByReference(const Reference& ref) {
	// First try the ID. This is because when we lookup by ID, we only fill in the ID cache.
	// Looking up by name fills in the name and ID cache. So a cache miss will cause a failed
	// ID lookup, then a successful name lookup. Subsequent look ups will hit immediately
	// because the ID is cached too.
	//
	// If we looked up by name first, a cache miss would mean we failed to lookup by name, then
	// succeeded to lookup by ID. Subsequent lookups will miss then hit.
	const SymbolTable::Symbol* symbol = nullptr;
	if (ref.id) {
	symbol = FindById(ref.id.value());
	}

	if (ref.name && !symbol) {
	symbol = FindByName(ref.name.value());
	}
	return symbol;
	}

	std::unique_ptr<SymbolTable::Symbol> DefaultSymbolTableDelegate::FindByName(
	const ResourceName& name, const std::vector<std::unique_ptr<ISymbolSource>>& sources) {
	for (auto& source : sources) {
	std::unique_ptr<SymbolTable::Symbol> symbol = source->FindByName(name);
	if (symbol) {
	return symbol;
	}
	}
	return {};
	}

	std::unique_ptr<SymbolTable::Symbol> DefaultSymbolTableDelegate::FindById(
	ResourceId id, const std::vector<std::unique_ptr<ISymbolSource>>& sources) {
	for (auto& source : sources) {
	std::unique_ptr<SymbolTable::Symbol> symbol = source->FindById(id);
	if (symbol) {
	return symbol;
	}
	}
	return {};
	}

	std::unique_ptr<SymbolTable::Symbol> ResourceTableSymbolSource::FindByName(
	const ResourceName& name) {
	Maybe<ResourceTable::SearchResult> result = table_->FindResource(name);
	if (!result) {
	if (name.type == ResourceType::kAttr) {
	// Recurse and try looking up a private attribute.
	return FindByName(ResourceName(name.package, ResourceType::kAttrPrivate, name.entry));
	}
	return {};
	}

	ResourceTable::SearchResult sr = result.value();

	std::unique_ptr<SymbolTable::Symbol> symbol = util::make_unique<SymbolTable::Symbol>();
	symbol->is_public = (sr.entry->visibility.level == Visibility::Level::kPublic);

	if (sr.package->id && sr.type->id && sr.entry->id) {
	symbol->id = ResourceId(sr.package->id.value(), sr.type->id.value(), sr.entry->id.value());
	}

	if (name.type == ResourceType::kAttr \|\| name.type == ResourceType::kAttrPrivate) {
	const ConfigDescription kDefaultConfig;
	ResourceConfigValue* config_value = sr.entry->FindValue(kDefaultConfig);
	if (config_value) {
	// This resource has an Attribute.
	if (Attribute* attr = ValueCast<Attribute>(config_value->value.get())) {
	symbol->attribute = std::make_shared<Attribute>(*attr);
	} else {
	return {};
	}
	}
	}
	return symbol;
	}

	bool AssetManagerSymbolSource::AddAssetPath(const StringPiece& path) {
	int32_t cookie = 0;
	return assets_.addAssetPath(android::String8(path.data(), path.size()), &cookie);
	}

	std::map<size_t, std::string> AssetManagerSymbolSource::GetAssignedPackageIds() const {
	std::map<size_t, std::string> package_map;
	const android::ResTable& table = assets_.getResources(false);
	const size_t package_count = table.getBasePackageCount();
	for (size_t i = 0; i < package_count; i++) {
	package_map[table.getBasePackageId(i)] =
	util::Utf16ToUtf8(android::StringPiece16(table.getBasePackageName(i).string()));
	}
	return package_map;
	}

	static std::unique_ptr<SymbolTable::Symbol> LookupAttributeInTable(
	const android::ResTable& table, ResourceId id) {
	// Try as a bag.
	const android::ResTable::bag_entry* entry;
	ssize_t count = table.lockBag(id.id, &entry);
	if (count < 0) {
	table.unlockBag(entry);
	return nullptr;
	}

	// We found a resource.
	std::unique_ptr<SymbolTable::Symbol> s = util::make_unique<SymbolTable::Symbol>(id);

	// Check to see if it is an attribute.
	for (size_t i = 0; i < (size_t)count; i++) {
	if (entry[i].map.name.ident == android::ResTable_map::ATTR_TYPE) {
	s->attribute = std::make_shared<Attribute>(entry[i].map.value.data);
	break;
	}
	}

	if (s->attribute) {
	for (size_t i = 0; i < (size_t)count; i++) {
	const android::ResTable_map& map_entry = entry[i].map;
	if (Res_INTERNALID(map_entry.name.ident)) {
	switch (map_entry.name.ident) {
	case android::ResTable_map::ATTR_MIN:
	s->attribute->min_int = static_cast<int32_t>(map_entry.value.data);
	break;
	case android::ResTable_map::ATTR_MAX:
	s->attribute->max_int = static_cast<int32_t>(map_entry.value.data);
	break;
	}
	continue;
	}

	android::ResTable::resource_name entry_name;
	if (!table.getResourceName(map_entry.name.ident, false, &entry_name)) {
	table.unlockBag(entry);
	return nullptr;
	}

	Maybe<ResourceName> parsed_name = ResourceUtils::ToResourceName(entry_name);
	if (!parsed_name) {
	return nullptr;
	}

	Attribute::Symbol symbol;
	symbol.symbol.name = parsed_name.value();
	symbol.symbol.id = ResourceId(map_entry.name.ident);
	symbol.value = map_entry.value.data;
	s->attribute->symbols.push_back(std::move(symbol));
	}
	}
	table.unlockBag(entry);
	return s;
	}

	std::unique_ptr<SymbolTable::Symbol> AssetManagerSymbolSource::FindByName(
	const ResourceName& name) {
	const android::ResTable& table = assets_.getResources(false);

	const std::u16string package16 = util::Utf8ToUtf16(name.package);
	const std::u16string type16 = util::Utf8ToUtf16(to_string(name.type));
	const std::u16string entry16 = util::Utf8ToUtf16(name.entry);
	const std::u16string mangled_entry16 =
	util::Utf8ToUtf16(NameMangler::MangleEntry(name.package, name.entry));

	uint32_t type_spec_flags;
	ResourceId res_id;

	// There can be mangled resources embedded within other packages. Here we will
	// look into each package and look-up the mangled name until we find the resource.
	const size_t count = table.getBasePackageCount();
	for (size_t i = 0; i < count; i++) {
	const android::String16 package_name = table.getBasePackageName(i);
	StringPiece16 real_package16 = package16;
	StringPiece16 real_entry16 = entry16;
	std::u16string scratch_entry16;
	if (StringPiece16(package_name) != package16) {
	real_entry16 = mangled_entry16;
	real_package16 = package_name.string();
	}

	type_spec_flags = 0;
	res_id = table.identifierForName(real_entry16.data(), real_entry16.size(), type16.data(),
	type16.size(), real_package16.data(), real_package16.size(),
	&type_spec_flags);
	if (res_id.is_valid()) {
	break;
	}
	}

	if (!res_id.is_valid()) {
	return {};
	}

	std::unique_ptr<SymbolTable::Symbol> s;
	if (name.type == ResourceType::kAttr) {
	s = LookupAttributeInTable(table, res_id);
	} else {
	s = util::make_unique<SymbolTable::Symbol>();
	s->id = res_id;
	}

	if (s) {
	s->is_public = (type_spec_flags & android::ResTable_typeSpec::SPEC_PUBLIC) != 0;
	return s;
	}
	return {};
	}

	static Maybe<ResourceName> GetResourceName(const android::ResTable& table,
	ResourceId id) {
	android::ResTable::resource_name res_name = {};
	if (!table.getResourceName(id.id, true, &res_name)) {
	return {};
	}
	return ResourceUtils::ToResourceName(res_name);
	}

	std::unique_ptr<SymbolTable::Symbol> AssetManagerSymbolSource::FindById(
	ResourceId id) {
	if (!id.is_valid()) {
	// Exit early and avoid the error logs from AssetManager.
	return {};
	}

	const android::ResTable& table = assets_.getResources(false);
	Maybe<ResourceName> maybe_name = GetResourceName(table, id);
	if (!maybe_name) {
	return {};
	}

	uint32_t type_spec_flags = 0;
	table.getResourceFlags(id.id, &type_spec_flags);

	std::unique_ptr<SymbolTable::Symbol> s;
	if (maybe_name.value().type == ResourceType::kAttr) {
	s = LookupAttributeInTable(table, id);
	} else {
	s = util::make_unique<SymbolTable::Symbol>();
	s->id = id;
	}

	if (s) {
	s->is_public = (type_spec_flags & android::ResTable_typeSpec::SPEC_PUBLIC) != 0;
	return s;
	}
	return {};
	}

	std::unique_ptr<SymbolTable::Symbol> AssetManagerSymbolSource::FindByReference(
	const Reference& ref) {
	// AssetManager always prefers IDs.
	if (ref.id) {
	return FindById(ref.id.value());
	} else if (ref.name) {
	return FindByName(ref.name.value());
	}
	return {};
	}

	} // namespace aapt