tools/aapt2/format/binary/TableFlattener.cpp - LeafOS-Project/android_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 "format/binary/TableFlattener.h"

 #include <algorithm>
 #include <numeric>
 #include <sstream>
 #include <type_traits>

 #include "android-base/logging.h"
 #include "android-base/macros.h"
 #include "android-base/stringprintf.h"

 #include "ResourceTable.h"
 #include "ResourceValues.h"
 #include "SdkConstants.h"
 #include "ValueVisitor.h"
 #include "format/binary/ChunkWriter.h"
 #include "format/binary/ResourceTypeExtensions.h"
 #include "util/BigBuffer.h"

 using namespace android;

 namespace aapt {

 namespace {

 template <typename T>
 static bool cmp_ids(const T* a, const T* b) {
   return a->id.value() < b->id.value();
 }

 static void strcpy16_htod(uint16_t* dst, size_t len, const StringPiece16& src) {
   if (len == 0) {
     return;
   }

   size_t i;
   const char16_t* src_data = src.data();
   for (i = 0; i < len - 1 && i < src.size(); i++) {
     dst[i] = util::HostToDevice16((uint16_t)src_data[i]);
   }
   dst[i] = 0;
 }

 static bool cmp_style_entries(const Style::Entry& a, const Style::Entry& b) {
   if (a.key.id) {
     if (b.key.id) {
       return a.key.id.value() < b.key.id.value();
     }
     return true;
   } else if (!b.key.id) {
     return a.key.name.value() < b.key.name.value();
   }
   return false;
 }

 struct FlatEntry {
   ResourceEntry* entry;
   Value* value;

   // The entry string pool index to the entry's name.
   uint32_t entry_key;
 };

 class MapFlattenVisitor : public ValueVisitor {
  public:
   using ValueVisitor::Visit;

   MapFlattenVisitor(ResTable_entry_ext* out_entry, BigBuffer* buffer)
       : out_entry_(out_entry), buffer_(buffer) {
   }

   void Visit(Attribute* attr) override {
     {
       Reference key = Reference(ResourceId(ResTable_map::ATTR_TYPE));
       BinaryPrimitive val(Res_value::TYPE_INT_DEC, attr->type_mask);
       FlattenEntry(&key, &val);
     }

     if (attr->min_int != std::numeric_limits<int32_t>::min()) {
       Reference key = Reference(ResourceId(ResTable_map::ATTR_MIN));
       BinaryPrimitive val(Res_value::TYPE_INT_DEC, static_cast<uint32_t>(attr->min_int));
       FlattenEntry(&key, &val);
     }

     if (attr->max_int != std::numeric_limits<int32_t>::max()) {
       Reference key = Reference(ResourceId(ResTable_map::ATTR_MAX));
       BinaryPrimitive val(Res_value::TYPE_INT_DEC, static_cast<uint32_t>(attr->max_int));
       FlattenEntry(&key, &val);
     }

     for (Attribute::Symbol& s : attr->symbols) {
       BinaryPrimitive val(Res_value::TYPE_INT_DEC, s.value);
       FlattenEntry(&s.symbol, &val);
     }
   }

   void Visit(Style* style) override {
     if (style->parent) {
       const Reference& parent_ref = style->parent.value();
       CHECK(bool(parent_ref.id)) << "parent has no ID";
       out_entry_->parent.ident = util::HostToDevice32(parent_ref.id.value().id);
     }

     // Sort the style.
     std::sort(style->entries.begin(), style->entries.end(), cmp_style_entries);

     for (Style::Entry& entry : style->entries) {
       FlattenEntry(&entry.key, entry.value.get());
     }
   }

   void Visit(Styleable* styleable) override {
     for (auto& attr_ref : styleable->entries) {
       BinaryPrimitive val(Res_value{});
       FlattenEntry(&attr_ref, &val);
     }
   }

   void Visit(Array* array) override {
     const size_t count = array->elements.size();
     for (size_t i = 0; i < count; i++) {
       Reference key(android::ResTable_map::ATTR_MIN + i);
       FlattenEntry(&key, array->elements[i].get());
     }
   }

   void Visit(Plural* plural) override {
     const size_t count = plural->values.size();
     for (size_t i = 0; i < count; i++) {
       if (!plural->values[i]) {
         continue;
       }

       ResourceId q;
       switch (i) {
         case Plural::Zero:
           q.id = android::ResTable_map::ATTR_ZERO;
           break;

         case Plural::One:
           q.id = android::ResTable_map::ATTR_ONE;
           break;

         case Plural::Two:
           q.id = android::ResTable_map::ATTR_TWO;
           break;

         case Plural::Few:
           q.id = android::ResTable_map::ATTR_FEW;
           break;

         case Plural::Many:
           q.id = android::ResTable_map::ATTR_MANY;
           break;

         case Plural::Other:
           q.id = android::ResTable_map::ATTR_OTHER;
           break;

         default:
           LOG(FATAL) << "unhandled plural type";
           break;
       }

       Reference key(q);
       FlattenEntry(&key, plural->values[i].get());
     }
   }

   /**
    * Call this after visiting a Value. This will finish any work that
    * needs to be done to prepare the entry.
    */
   void Finish() {
     out_entry_->count = util::HostToDevice32(entry_count_);
   }

  private:
   DISALLOW_COPY_AND_ASSIGN(MapFlattenVisitor);

   void FlattenKey(Reference* key, ResTable_map* out_entry) {
     CHECK(bool(key->id)) << "key has no ID";
     out_entry->name.ident = util::HostToDevice32(key->id.value().id);
   }

   void FlattenValue(Item* value, ResTable_map* out_entry) {
     CHECK(value->Flatten(&out_entry->value)) << "flatten failed";
   }

   void FlattenEntry(Reference* key, Item* value) {
     ResTable_map* out_entry = buffer_->NextBlock<ResTable_map>();
     FlattenKey(key, out_entry);
     FlattenValue(value, out_entry);
     out_entry->value.size = util::HostToDevice16(sizeof(out_entry->value));
     entry_count_++;
   }

   ResTable_entry_ext* out_entry_;
   BigBuffer* buffer_;
   size_t entry_count_ = 0;
 };

 class PackageFlattener {
  public:
   PackageFlattener(IAaptContext* context, ResourceTablePackage* package,
                    const std::map<size_t, std::string>* shared_libs, bool use_sparse_entries,
                    bool collapse_key_stringpool, const std::set<std::string>& whitelisted_resources)
       : context_(context),
         diag_(context->GetDiagnostics()),
         package_(package),
         shared_libs_(shared_libs),
         use_sparse_entries_(use_sparse_entries),
         collapse_key_stringpool_(collapse_key_stringpool),
         whitelisted_resources_(whitelisted_resources) {
   }

   bool FlattenPackage(BigBuffer* buffer) {
     ChunkWriter pkg_writer(buffer);
     ResTable_package* pkg_header = pkg_writer.StartChunk<ResTable_package>(RES_TABLE_PACKAGE_TYPE);
     pkg_header->id = util::HostToDevice32(package_->id.value());

     // AAPT truncated the package name, so do the same.
     // Shared libraries require full package names, so don't truncate theirs.
     if (context_->GetPackageType() != PackageType::kApp &&
         package_->name.size() >= arraysize(pkg_header->name)) {
       diag_->Error(DiagMessage() << "package name '" << package_->name
                                  << "' is too long. "
                                     "Shared libraries cannot have truncated package names");
       return false;
     }

     // Copy the package name in device endianness.
     strcpy16_htod(pkg_header->name, arraysize(pkg_header->name), util::Utf8ToUtf16(package_->name));

     // Serialize the types. We do this now so that our type and key strings
     // are populated. We write those first.
     BigBuffer type_buffer(1024);
     FlattenTypes(&type_buffer);

     pkg_header->typeStrings = util::HostToDevice32(pkg_writer.size());
     StringPool::FlattenUtf16(pkg_writer.buffer(), type_pool_, diag_);

     pkg_header->keyStrings = util::HostToDevice32(pkg_writer.size());
     StringPool::FlattenUtf8(pkg_writer.buffer(), key_pool_, diag_);

     // Append the types.
     buffer->AppendBuffer(std::move(type_buffer));

     // If there are libraries (or if the package ID is 0x00), encode a library chunk.
     if (package_->id.value() == 0x00 || !shared_libs_->empty()) {
       FlattenLibrarySpec(buffer);
     }

     pkg_writer.Finish();
     return true;
   }

  private:
   DISALLOW_COPY_AND_ASSIGN(PackageFlattener);

   template <typename T, bool IsItem>
   T* WriteEntry(FlatEntry* entry, BigBuffer* buffer) {
     static_assert(
         std::is_same<ResTable_entry, T>::value || std::is_same<ResTable_entry_ext, T>::value,
         "T must be ResTable_entry or ResTable_entry_ext");

     T* result = buffer->NextBlock<T>();
     ResTable_entry* out_entry = (ResTable_entry*)result;
     if (entry->entry->visibility.level == Visibility::Level::kPublic) {
       out_entry->flags |= ResTable_entry::FLAG_PUBLIC;
     }

     if (entry->value->IsWeak()) {
       out_entry->flags |= ResTable_entry::FLAG_WEAK;
     }

     if (!IsItem) {
       out_entry->flags |= ResTable_entry::FLAG_COMPLEX;
     }

     out_entry->flags = util::HostToDevice16(out_entry->flags);
     out_entry->key.index = util::HostToDevice32(entry->entry_key);
     out_entry->size = util::HostToDevice16(sizeof(T));
     return result;
   }

   bool FlattenValue(FlatEntry* entry, BigBuffer* buffer) {
     if (Item* item = ValueCast<Item>(entry->value)) {
       WriteEntry<ResTable_entry, true>(entry, buffer);
       Res_value* outValue = buffer->NextBlock<Res_value>();
       CHECK(item->Flatten(outValue)) << "flatten failed";
       outValue->size = util::HostToDevice16(sizeof(*outValue));
     } else {
       ResTable_entry_ext* out_entry = WriteEntry<ResTable_entry_ext, false>(entry, buffer);
       MapFlattenVisitor visitor(out_entry, buffer);
       entry->value->Accept(&visitor);
       visitor.Finish();
     }
     return true;
   }

   bool FlattenConfig(const ResourceTableType* type, const ConfigDescription& config,
                      const size_t num_total_entries, std::vector<FlatEntry>* entries,
                      BigBuffer* buffer) {
     CHECK(num_total_entries != 0);
     CHECK(num_total_entries <= std::numeric_limits<uint16_t>::max());

     ChunkWriter type_writer(buffer);
     ResTable_type* type_header = type_writer.StartChunk<ResTable_type>(RES_TABLE_TYPE_TYPE);
     type_header->id = type->id.value();
     type_header->config = config;
     type_header->config.swapHtoD();

     std::vector<uint32_t> offsets;
     offsets.resize(num_total_entries, 0xffffffffu);

     BigBuffer values_buffer(512);
     for (FlatEntry& flat_entry : *entries) {
       CHECK(static_cast<size_t>(flat_entry.entry->id.value()) < num_total_entries);
       offsets[flat_entry.entry->id.value()] = values_buffer.size();
       if (!FlattenValue(&flat_entry, &values_buffer)) {
         diag_->Error(DiagMessage()
                      << "failed to flatten resource '"
                      << ResourceNameRef(package_->name, type->type, flat_entry.entry->name)
                      << "' for configuration '" << config << "'");
         return false;
       }
     }

     bool sparse_encode = use_sparse_entries_;

     // Only sparse encode if the entries will be read on platforms O+.
     sparse_encode =
         sparse_encode && (context_->GetMinSdkVersion() >= SDK_O || config.sdkVersion >= SDK_O);

     // Only sparse encode if the offsets are representable in 2 bytes.
     sparse_encode =
         sparse_encode && (values_buffer.size() / 4u) <= std::numeric_limits<uint16_t>::max();

     // Only sparse encode if the ratio of populated entries to total entries is below some
     // threshold.
     sparse_encode =
         sparse_encode && ((100 * entries->size()) / num_total_entries) < kSparseEncodingThreshold;

     if (sparse_encode) {
       type_header->entryCount = util::HostToDevice32(entries->size());
       type_header->flags |= ResTable_type::FLAG_SPARSE;
       ResTable_sparseTypeEntry* indices =
           type_writer.NextBlock<ResTable_sparseTypeEntry>(entries->size());
       for (size_t i = 0; i < num_total_entries; i++) {
         if (offsets[i] != ResTable_type::NO_ENTRY) {
           CHECK((offsets[i] & 0x03) == 0);
           indices->idx = util::HostToDevice16(i);
           indices->offset = util::HostToDevice16(offsets[i] / 4u);
           indices++;
         }
       }
     } else {
       type_header->entryCount = util::HostToDevice32(num_total_entries);
       uint32_t* indices = type_writer.NextBlock<uint32_t>(num_total_entries);
       for (size_t i = 0; i < num_total_entries; i++) {
         indices[i] = util::HostToDevice32(offsets[i]);
       }
     }

     type_header->entriesStart = util::HostToDevice32(type_writer.size());
     type_writer.buffer()->AppendBuffer(std::move(values_buffer));
     type_writer.Finish();
     return true;
   }

   std::vector<ResourceTableType*> CollectAndSortTypes() {
     std::vector<ResourceTableType*> sorted_types;
     for (auto& type : package_->types) {
       if (type->type == ResourceType::kStyleable) {
         // Styleables aren't real Resource Types, they are represented in the
         // R.java file.
         continue;
       }

       CHECK(bool(type->id)) << "type must have an ID set";

       sorted_types.push_back(type.get());
     }
     std::sort(sorted_types.begin(), sorted_types.end(), cmp_ids<ResourceTableType>);
     return sorted_types;
   }

   std::vector<ResourceEntry*> CollectAndSortEntries(ResourceTableType* type) {
     // Sort the entries by entry ID.
     std::vector<ResourceEntry*> sorted_entries;
     for (auto& entry : type->entries) {
       CHECK(bool(entry->id)) << "entry must have an ID set";
       sorted_entries.push_back(entry.get());
     }
     std::sort(sorted_entries.begin(), sorted_entries.end(), cmp_ids<ResourceEntry>);
     return sorted_entries;
   }

   bool FlattenTypeSpec(ResourceTableType* type, std::vector<ResourceEntry*>* sorted_entries,
                        BigBuffer* buffer) {
     ChunkWriter type_spec_writer(buffer);
     ResTable_typeSpec* spec_header =
         type_spec_writer.StartChunk<ResTable_typeSpec>(RES_TABLE_TYPE_SPEC_TYPE);
     spec_header->id = type->id.value();

     if (sorted_entries->empty()) {
       type_spec_writer.Finish();
       return true;
     }

     // We can't just take the size of the vector. There may be holes in the
     // entry ID space.
     // Since the entries are sorted by ID, the last one will be the biggest.
     const size_t num_entries = sorted_entries->back()->id.value() + 1;

     spec_header->entryCount = util::HostToDevice32(num_entries);

     // Reserve space for the masks of each resource in this type. These
     // show for which configuration axis the resource changes.
     uint32_t* config_masks = type_spec_writer.NextBlock<uint32_t>(num_entries);

     const size_t actual_num_entries = sorted_entries->size();
     for (size_t entryIndex = 0; entryIndex < actual_num_entries; entryIndex++) {
       ResourceEntry* entry = sorted_entries->at(entryIndex);

       // Populate the config masks for this entry.

       if (entry->visibility.level == Visibility::Level::kPublic) {
         config_masks[entry->id.value()] |= util::HostToDevice32(ResTable_typeSpec::SPEC_PUBLIC);
       }

       if (!entry->overlayable_declarations.empty()) {
         config_masks[entry->id.value()] |=
             util::HostToDevice32(ResTable_typeSpec::SPEC_OVERLAYABLE);
       }

       const size_t config_count = entry->values.size();
       for (size_t i = 0; i < config_count; i++) {
         const ConfigDescription& config = entry->values[i]->config;
         for (size_t j = i + 1; j < config_count; j++) {
           config_masks[entry->id.value()] |=
               util::HostToDevice32(config.diff(entry->values[j]->config));
         }
       }
     }
     type_spec_writer.Finish();
     return true;
   }

   bool FlattenTypes(BigBuffer* buffer) {
     // Sort the types by their IDs. They will be inserted into the StringPool in
     // this order.
     std::vector<ResourceTableType*> sorted_types = CollectAndSortTypes();

     size_t expected_type_id = 1;
     for (ResourceTableType* type : sorted_types) {
       // If there is a gap in the type IDs, fill in the StringPool
       // with empty values until we reach the ID we expect.
       while (type->id.value() > expected_type_id) {
         std::stringstream type_name;
         type_name << "?" << expected_type_id;
         type_pool_.MakeRef(type_name.str());
         expected_type_id++;
       }
       expected_type_id++;
       type_pool_.MakeRef(to_string(type->type));

       std::vector<ResourceEntry*> sorted_entries = CollectAndSortEntries(type);
       if (sorted_entries.empty()) {
         continue;
       }

       if (!FlattenTypeSpec(type, &sorted_entries, buffer)) {
         return false;
       }

       // Since the entries are sorted by ID, the last ID will be the largest.
       const size_t num_entries = sorted_entries.back()->id.value() + 1;

       // The binary resource table lists resource entries for each
       // configuration.
       // We store them inverted, where a resource entry lists the values for
       // each
       // configuration available. Here we reverse this to match the binary
       // table.
       std::map<ConfigDescription, std::vector<FlatEntry>> config_to_entry_list_map;

       // hardcoded string uses characters which make it an invalid resource name
       const std::string obfuscated_resource_name = "0_resource_name_obfuscated";

       for (ResourceEntry* entry : sorted_entries) {
         uint32_t local_key_index;
         if (!collapse_key_stringpool_ ||
             whitelisted_resources_.find(entry->name) != whitelisted_resources_.end()) {
           local_key_index = (uint32_t)key_pool_.MakeRef(entry->name).index();
         } else {
           // resource isn't whitelisted, add it as obfuscated value
           local_key_index = (uint32_t)key_pool_.MakeRef(obfuscated_resource_name).index();
         }
         // Group values by configuration.
         for (auto& config_value : entry->values) {
           config_to_entry_list_map[config_value->config].push_back(
               FlatEntry{entry, config_value->value.get(), local_key_index});
         }
       }

       // Flatten a configuration value.
       for (auto& entry : config_to_entry_list_map) {
         if (!FlattenConfig(type, entry.first, num_entries, &entry.second, buffer)) {
           return false;
         }
       }
     }
     return true;
   }

   void FlattenLibrarySpec(BigBuffer* buffer) {
     ChunkWriter lib_writer(buffer);
     ResTable_lib_header* lib_header =
         lib_writer.StartChunk<ResTable_lib_header>(RES_TABLE_LIBRARY_TYPE);

     const size_t num_entries = (package_->id.value() == 0x00 ? 1 : 0) + shared_libs_->size();
     CHECK(num_entries > 0);

     lib_header->count = util::HostToDevice32(num_entries);

     ResTable_lib_entry* lib_entry = buffer->NextBlock<ResTable_lib_entry>(num_entries);
     if (package_->id.value() == 0x00) {
       // Add this package
       lib_entry->packageId = util::HostToDevice32(0x00);
       strcpy16_htod(lib_entry->packageName, arraysize(lib_entry->packageName),
                     util::Utf8ToUtf16(package_->name));
       ++lib_entry;
     }

     for (auto& map_entry : *shared_libs_) {
       lib_entry->packageId = util::HostToDevice32(map_entry.first);
       strcpy16_htod(lib_entry->packageName, arraysize(lib_entry->packageName),
                     util::Utf8ToUtf16(map_entry.second));
       ++lib_entry;
     }
     lib_writer.Finish();
   }

   IAaptContext* context_;
   IDiagnostics* diag_;
   ResourceTablePackage* package_;
   const std::map<size_t, std::string>* shared_libs_;
   bool use_sparse_entries_;
   StringPool type_pool_;
   StringPool key_pool_;
   bool collapse_key_stringpool_;
   const std::set<std::string>& whitelisted_resources_;
 };

 }  // namespace

 bool TableFlattener::Consume(IAaptContext* context, ResourceTable* table) {
   if (options_.sort_stringpool_entries) {
     // We must do this before writing the resources, since the string pool IDs may change.
     table->string_pool.Prune();
     table->string_pool.Sort([](const StringPool::Context &a, const StringPool::Context &b) -> int {
       int diff = util::compare(a.priority, b.priority);
       if (diff == 0) {
         diff = a.config.compare(b.config);
       }
       return diff;
     });
   }

   // Write the ResTable header.
   ChunkWriter table_writer(buffer_);
   ResTable_header* table_header = table_writer.StartChunk<ResTable_header>(RES_TABLE_TYPE);
   table_header->packageCount = util::HostToDevice32(table->packages.size());

   // Flatten the values string pool.
   StringPool::FlattenUtf8(table_writer.buffer(), table->string_pool,
       context->GetDiagnostics());

   BigBuffer package_buffer(1024);

   // Flatten each package.
   for (auto& package : table->packages) {
     if (context->GetPackageType() == PackageType::kApp) {
       // Write a self mapping entry for this package if the ID is non-standard (0x7f).
       const uint8_t package_id = package->id.value();
       if (package_id != kFrameworkPackageId && package_id != kAppPackageId) {
         auto result = table->included_packages_.insert({package_id, package->name});
         if (!result.second && result.first->second != package->name) {
           // A mapping for this package ID already exists, and is a different package. Error!
           context->GetDiagnostics()->Error(
               DiagMessage() << android::base::StringPrintf(
                   "can't map package ID %02x to '%s'. Already mapped to '%s'", package_id,
                   package->name.c_str(), result.first->second.c_str()));
           return false;
         }
       }
     }

     PackageFlattener flattener(context, package.get(), &table->included_packages_,
                                options_.use_sparse_entries, options_.collapse_key_stringpool,
                                options_.whitelisted_resources);
     if (!flattener.FlattenPackage(&package_buffer)) {
       return false;
     }
   }

   // Finally merge all the packages into the main buffer.
   table_writer.buffer()->AppendBuffer(std::move(package_buffer));
   table_writer.Finish();
   return true;
 }

 }  // 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 "format/binary/TableFlattener.h"

	#include <algorithm>
	#include <numeric>
	#include <sstream>
	#include <type_traits>

	#include "android-base/logging.h"
	#include "android-base/macros.h"
	#include "android-base/stringprintf.h"

	#include "ResourceTable.h"
	#include "ResourceValues.h"
	#include "SdkConstants.h"
	#include "ValueVisitor.h"
	#include "format/binary/ChunkWriter.h"
	#include "format/binary/ResourceTypeExtensions.h"
	#include "util/BigBuffer.h"

	using namespace android;

	namespace aapt {

	namespace {

	template <typename T>
	static bool cmp_ids(const T* a, const T* b) {
	return a->id.value() < b->id.value();
	}

	static void strcpy16_htod(uint16_t* dst, size_t len, const StringPiece16& src) {
	if (len == 0) {
	return;
	}

	size_t i;
	const char16_t* src_data = src.data();
	for (i = 0; i < len - 1 && i < src.size(); i++) {
	dst[i] = util::HostToDevice16((uint16_t)src_data[i]);
	}
	dst[i] = 0;
	}

	static bool cmp_style_entries(const Style::Entry& a, const Style::Entry& b) {
	if (a.key.id) {
	if (b.key.id) {
	return a.key.id.value() < b.key.id.value();
	}
	return true;
	} else if (!b.key.id) {
	return a.key.name.value() < b.key.name.value();
	}
	return false;
	}

	struct FlatEntry {
	ResourceEntry* entry;
	Value* value;

	// The entry string pool index to the entry's name.
	uint32_t entry_key;
	};

	class MapFlattenVisitor : public ValueVisitor {
	public:
	using ValueVisitor::Visit;

	MapFlattenVisitor(ResTable_entry_ext* out_entry, BigBuffer* buffer)
	: out_entry_(out_entry), buffer_(buffer) {
	}

	void Visit(Attribute* attr) override {
	{
	Reference key = Reference(ResourceId(ResTable_map::ATTR_TYPE));
	BinaryPrimitive val(Res_value::TYPE_INT_DEC, attr->type_mask);
	FlattenEntry(&key, &val);
	}

	if (attr->min_int != std::numeric_limits<int32_t>::min()) {
	Reference key = Reference(ResourceId(ResTable_map::ATTR_MIN));
	BinaryPrimitive val(Res_value::TYPE_INT_DEC, static_cast<uint32_t>(attr->min_int));
	FlattenEntry(&key, &val);
	}

	if (attr->max_int != std::numeric_limits<int32_t>::max()) {
	Reference key = Reference(ResourceId(ResTable_map::ATTR_MAX));
	BinaryPrimitive val(Res_value::TYPE_INT_DEC, static_cast<uint32_t>(attr->max_int));
	FlattenEntry(&key, &val);
	}

	for (Attribute::Symbol& s : attr->symbols) {
	BinaryPrimitive val(Res_value::TYPE_INT_DEC, s.value);
	FlattenEntry(&s.symbol, &val);
	}
	}

	void Visit(Style* style) override {
	if (style->parent) {
	const Reference& parent_ref = style->parent.value();
	CHECK(bool(parent_ref.id)) << "parent has no ID";
	out_entry_->parent.ident = util::HostToDevice32(parent_ref.id.value().id);
	}

	// Sort the style.
	std::sort(style->entries.begin(), style->entries.end(), cmp_style_entries);

	for (Style::Entry& entry : style->entries) {
	FlattenEntry(&entry.key, entry.value.get());
	}
	}

	void Visit(Styleable* styleable) override {
	for (auto& attr_ref : styleable->entries) {
	BinaryPrimitive val(Res_value{});
	FlattenEntry(&attr_ref, &val);
	}
	}

	void Visit(Array* array) override {
	const size_t count = array->elements.size();
	for (size_t i = 0; i < count; i++) {
	Reference key(android::ResTable_map::ATTR_MIN + i);
	FlattenEntry(&key, array->elements[i].get());
	}
	}

	void Visit(Plural* plural) override {
	const size_t count = plural->values.size();
	for (size_t i = 0; i < count; i++) {
	if (!plural->values[i]) {
	continue;
	}

	ResourceId q;
	switch (i) {
	case Plural::Zero:
	q.id = android::ResTable_map::ATTR_ZERO;
	break;

	case Plural::One:
	q.id = android::ResTable_map::ATTR_ONE;
	break;

	case Plural::Two:
	q.id = android::ResTable_map::ATTR_TWO;
	break;

	case Plural::Few:
	q.id = android::ResTable_map::ATTR_FEW;
	break;

	case Plural::Many:
	q.id = android::ResTable_map::ATTR_MANY;
	break;

	case Plural::Other:
	q.id = android::ResTable_map::ATTR_OTHER;
	break;

	default:
	LOG(FATAL) << "unhandled plural type";
	break;
	}

	Reference key(q);
	FlattenEntry(&key, plural->values[i].get());
	}
	}

	/**
	* Call this after visiting a Value. This will finish any work that
	* needs to be done to prepare the entry.
	*/
	void Finish() {
	out_entry_->count = util::HostToDevice32(entry_count_);
	}

	private:
	DISALLOW_COPY_AND_ASSIGN(MapFlattenVisitor);

	void FlattenKey(Reference* key, ResTable_map* out_entry) {
	CHECK(bool(key->id)) << "key has no ID";
	out_entry->name.ident = util::HostToDevice32(key->id.value().id);
	}

	void FlattenValue(Item* value, ResTable_map* out_entry) {
	CHECK(value->Flatten(&out_entry->value)) << "flatten failed";
	}

	void FlattenEntry(Reference* key, Item* value) {
	ResTable_map* out_entry = buffer_->NextBlock<ResTable_map>();
	FlattenKey(key, out_entry);
	FlattenValue(value, out_entry);
	out_entry->value.size = util::HostToDevice16(sizeof(out_entry->value));
	entry_count_++;
	}

	ResTable_entry_ext* out_entry_;
	BigBuffer* buffer_;
	size_t entry_count_ = 0;
	};

	class PackageFlattener {
	public:
	PackageFlattener(IAaptContext* context, ResourceTablePackage* package,
	const std::map<size_t, std::string>* shared_libs, bool use_sparse_entries,
	bool collapse_key_stringpool, const std::set<std::string>& whitelisted_resources)
	: context_(context),
	diag_(context->GetDiagnostics()),
	package_(package),
	shared_libs_(shared_libs),
	use_sparse_entries_(use_sparse_entries),
	collapse_key_stringpool_(collapse_key_stringpool),
	whitelisted_resources_(whitelisted_resources) {
	}

	bool FlattenPackage(BigBuffer* buffer) {
	ChunkWriter pkg_writer(buffer);
	ResTable_package* pkg_header = pkg_writer.StartChunk<ResTable_package>(RES_TABLE_PACKAGE_TYPE);
	pkg_header->id = util::HostToDevice32(package_->id.value());

	// AAPT truncated the package name, so do the same.
	// Shared libraries require full package names, so don't truncate theirs.
	if (context_->GetPackageType() != PackageType::kApp &&
	package_->name.size() >= arraysize(pkg_header->name)) {
	diag_->Error(DiagMessage() << "package name '" << package_->name
	<< "' is too long. "
	"Shared libraries cannot have truncated package names");
	return false;
	}

	// Copy the package name in device endianness.
	strcpy16_htod(pkg_header->name, arraysize(pkg_header->name), util::Utf8ToUtf16(package_->name));

	// Serialize the types. We do this now so that our type and key strings
	// are populated. We write those first.
	BigBuffer type_buffer(1024);
	FlattenTypes(&type_buffer);

	pkg_header->typeStrings = util::HostToDevice32(pkg_writer.size());
	StringPool::FlattenUtf16(pkg_writer.buffer(), type_pool_, diag_);

	pkg_header->keyStrings = util::HostToDevice32(pkg_writer.size());
	StringPool::FlattenUtf8(pkg_writer.buffer(), key_pool_, diag_);

	// Append the types.
	buffer->AppendBuffer(std::move(type_buffer));

	// If there are libraries (or if the package ID is 0x00), encode a library chunk.
	if (package_->id.value() == 0x00 \|\| !shared_libs_->empty()) {
	FlattenLibrarySpec(buffer);
	}

	pkg_writer.Finish();
	return true;
	}

	private:
	DISALLOW_COPY_AND_ASSIGN(PackageFlattener);

	template <typename T, bool IsItem>
	T* WriteEntry(FlatEntry* entry, BigBuffer* buffer) {
	static_assert(
	std::is_same<ResTable_entry, T>::value \|\| std::is_same<ResTable_entry_ext, T>::value,
	"T must be ResTable_entry or ResTable_entry_ext");

	T* result = buffer->NextBlock<T>();
	ResTable_entry* out_entry = (ResTable_entry*)result;
	if (entry->entry->visibility.level == Visibility::Level::kPublic) {
	out_entry->flags \|= ResTable_entry::FLAG_PUBLIC;
	}

	if (entry->value->IsWeak()) {
	out_entry->flags \|= ResTable_entry::FLAG_WEAK;
	}

	if (!IsItem) {
	out_entry->flags \|= ResTable_entry::FLAG_COMPLEX;
	}

	out_entry->flags = util::HostToDevice16(out_entry->flags);
	out_entry->key.index = util::HostToDevice32(entry->entry_key);
	out_entry->size = util::HostToDevice16(sizeof(T));
	return result;
	}

	bool FlattenValue(FlatEntry* entry, BigBuffer* buffer) {
	if (Item* item = ValueCast<Item>(entry->value)) {
	WriteEntry<ResTable_entry, true>(entry, buffer);
	Res_value* outValue = buffer->NextBlock<Res_value>();
	CHECK(item->Flatten(outValue)) << "flatten failed";
	outValue->size = util::HostToDevice16(sizeof(*outValue));
	} else {
	ResTable_entry_ext* out_entry = WriteEntry<ResTable_entry_ext, false>(entry, buffer);
	MapFlattenVisitor visitor(out_entry, buffer);
	entry->value->Accept(&visitor);
	visitor.Finish();
	}
	return true;
	}

	bool FlattenConfig(const ResourceTableType* type, const ConfigDescription& config,
	const size_t num_total_entries, std::vector<FlatEntry>* entries,
	BigBuffer* buffer) {
	CHECK(num_total_entries != 0);
	CHECK(num_total_entries <= std::numeric_limits<uint16_t>::max());

	ChunkWriter type_writer(buffer);
	ResTable_type* type_header = type_writer.StartChunk<ResTable_type>(RES_TABLE_TYPE_TYPE);
	type_header->id = type->id.value();
	type_header->config = config;
	type_header->config.swapHtoD();

	std::vector<uint32_t> offsets;
	offsets.resize(num_total_entries, 0xffffffffu);

	BigBuffer values_buffer(512);
	for (FlatEntry& flat_entry : *entries) {
	CHECK(static_cast<size_t>(flat_entry.entry->id.value()) < num_total_entries);
	offsets[flat_entry.entry->id.value()] = values_buffer.size();
	if (!FlattenValue(&flat_entry, &values_buffer)) {
	diag_->Error(DiagMessage()
	<< "failed to flatten resource '"
	<< ResourceNameRef(package_->name, type->type, flat_entry.entry->name)
	<< "' for configuration '" << config << "'");
	return false;
	}
	}

	bool sparse_encode = use_sparse_entries_;

	// Only sparse encode if the entries will be read on platforms O+.
	sparse_encode =
	sparse_encode && (context_->GetMinSdkVersion() >= SDK_O \|\| config.sdkVersion >= SDK_O);

	// Only sparse encode if the offsets are representable in 2 bytes.
	sparse_encode =
	sparse_encode && (values_buffer.size() / 4u) <= std::numeric_limits<uint16_t>::max();

	// Only sparse encode if the ratio of populated entries to total entries is below some
	// threshold.
	sparse_encode =
	sparse_encode && ((100 * entries->size()) / num_total_entries) < kSparseEncodingThreshold;

	if (sparse_encode) {
	type_header->entryCount = util::HostToDevice32(entries->size());
	type_header->flags \|= ResTable_type::FLAG_SPARSE;
	ResTable_sparseTypeEntry* indices =
	type_writer.NextBlock<ResTable_sparseTypeEntry>(entries->size());
	for (size_t i = 0; i < num_total_entries; i++) {
	if (offsets[i] != ResTable_type::NO_ENTRY) {
	CHECK((offsets[i] & 0x03) == 0);
	indices->idx = util::HostToDevice16(i);
	indices->offset = util::HostToDevice16(offsets[i] / 4u);
	indices++;
	}
	}
	} else {
	type_header->entryCount = util::HostToDevice32(num_total_entries);
	uint32_t* indices = type_writer.NextBlock<uint32_t>(num_total_entries);
	for (size_t i = 0; i < num_total_entries; i++) {
	indices[i] = util::HostToDevice32(offsets[i]);
	}
	}

	type_header->entriesStart = util::HostToDevice32(type_writer.size());
	type_writer.buffer()->AppendBuffer(std::move(values_buffer));
	type_writer.Finish();
	return true;
	}

	std::vector<ResourceTableType*> CollectAndSortTypes() {
	std::vector<ResourceTableType*> sorted_types;
	for (auto& type : package_->types) {
	if (type->type == ResourceType::kStyleable) {
	// Styleables aren't real Resource Types, they are represented in the
	// R.java file.
	continue;
	}

	CHECK(bool(type->id)) << "type must have an ID set";

	sorted_types.push_back(type.get());
	}
	std::sort(sorted_types.begin(), sorted_types.end(), cmp_ids<ResourceTableType>);
	return sorted_types;
	}

	std::vector<ResourceEntry> CollectAndSortEntries(ResourceTableType type) {
	// Sort the entries by entry ID.
	std::vector<ResourceEntry*> sorted_entries;
	for (auto& entry : type->entries) {
	CHECK(bool(entry->id)) << "entry must have an ID set";
	sorted_entries.push_back(entry.get());
	}
	std::sort(sorted_entries.begin(), sorted_entries.end(), cmp_ids<ResourceEntry>);
	return sorted_entries;
	}

	bool FlattenTypeSpec(ResourceTableType* type, std::vector<ResourceEntry> sorted_entries,
	BigBuffer* buffer) {
	ChunkWriter type_spec_writer(buffer);
	ResTable_typeSpec* spec_header =
	type_spec_writer.StartChunk<ResTable_typeSpec>(RES_TABLE_TYPE_SPEC_TYPE);
	spec_header->id = type->id.value();

	if (sorted_entries->empty()) {
	type_spec_writer.Finish();
	return true;
	}

	// We can't just take the size of the vector. There may be holes in the
	// entry ID space.
	// Since the entries are sorted by ID, the last one will be the biggest.
	const size_t num_entries = sorted_entries->back()->id.value() + 1;

	spec_header->entryCount = util::HostToDevice32(num_entries);

	// Reserve space for the masks of each resource in this type. These
	// show for which configuration axis the resource changes.
	uint32_t* config_masks = type_spec_writer.NextBlock<uint32_t>(num_entries);

	const size_t actual_num_entries = sorted_entries->size();
	for (size_t entryIndex = 0; entryIndex < actual_num_entries; entryIndex++) {
	ResourceEntry* entry = sorted_entries->at(entryIndex);

	// Populate the config masks for this entry.

	if (entry->visibility.level == Visibility::Level::kPublic) {
	config_masks[entry->id.value()] \|= util::HostToDevice32(ResTable_typeSpec::SPEC_PUBLIC);
	}

	if (!entry->overlayable_declarations.empty()) {
	config_masks[entry->id.value()] \|=
	util::HostToDevice32(ResTable_typeSpec::SPEC_OVERLAYABLE);
	}

	const size_t config_count = entry->values.size();
	for (size_t i = 0; i < config_count; i++) {
	const ConfigDescription& config = entry->values[i]->config;
	for (size_t j = i + 1; j < config_count; j++) {
	config_masks[entry->id.value()] \|=
	util::HostToDevice32(config.diff(entry->values[j]->config));
	}
	}
	}
	type_spec_writer.Finish();
	return true;
	}

	bool FlattenTypes(BigBuffer* buffer) {
	// Sort the types by their IDs. They will be inserted into the StringPool in
	// this order.
	std::vector<ResourceTableType*> sorted_types = CollectAndSortTypes();

	size_t expected_type_id = 1;
	for (ResourceTableType* type : sorted_types) {
	// If there is a gap in the type IDs, fill in the StringPool
	// with empty values until we reach the ID we expect.
	while (type->id.value() > expected_type_id) {
	std::stringstream type_name;
	type_name << "?" << expected_type_id;
	type_pool_.MakeRef(type_name.str());
	expected_type_id++;
	}
	expected_type_id++;
	type_pool_.MakeRef(to_string(type->type));

	std::vector<ResourceEntry*> sorted_entries = CollectAndSortEntries(type);
	if (sorted_entries.empty()) {
	continue;
	}

	if (!FlattenTypeSpec(type, &sorted_entries, buffer)) {
	return false;
	}

	// Since the entries are sorted by ID, the last ID will be the largest.
	const size_t num_entries = sorted_entries.back()->id.value() + 1;

	// The binary resource table lists resource entries for each
	// configuration.
	// We store them inverted, where a resource entry lists the values for
	// each
	// configuration available. Here we reverse this to match the binary
	// table.
	std::map<ConfigDescription, std::vector<FlatEntry>> config_to_entry_list_map;

	// hardcoded string uses characters which make it an invalid resource name
	const std::string obfuscated_resource_name = "0_resource_name_obfuscated";

	for (ResourceEntry* entry : sorted_entries) {
	uint32_t local_key_index;
	if (!collapse_key_stringpool_ \|\|
	whitelisted_resources_.find(entry->name) != whitelisted_resources_.end()) {
	local_key_index = (uint32_t)key_pool_.MakeRef(entry->name).index();
	} else {
	// resource isn't whitelisted, add it as obfuscated value
	local_key_index = (uint32_t)key_pool_.MakeRef(obfuscated_resource_name).index();
	}
	// Group values by configuration.
	for (auto& config_value : entry->values) {
	config_to_entry_list_map[config_value->config].push_back(
	FlatEntry{entry, config_value->value.get(), local_key_index});
	}
	}

	// Flatten a configuration value.
	for (auto& entry : config_to_entry_list_map) {
	if (!FlattenConfig(type, entry.first, num_entries, &entry.second, buffer)) {
	return false;
	}
	}
	}
	return true;
	}

	void FlattenLibrarySpec(BigBuffer* buffer) {
	ChunkWriter lib_writer(buffer);
	ResTable_lib_header* lib_header =
	lib_writer.StartChunk<ResTable_lib_header>(RES_TABLE_LIBRARY_TYPE);

	const size_t num_entries = (package_->id.value() == 0x00 ? 1 : 0) + shared_libs_->size();
	CHECK(num_entries > 0);

	lib_header->count = util::HostToDevice32(num_entries);

	ResTable_lib_entry* lib_entry = buffer->NextBlock<ResTable_lib_entry>(num_entries);
	if (package_->id.value() == 0x00) {
	// Add this package
	lib_entry->packageId = util::HostToDevice32(0x00);
	strcpy16_htod(lib_entry->packageName, arraysize(lib_entry->packageName),
	util::Utf8ToUtf16(package_->name));
	++lib_entry;
	}

	for (auto& map_entry : *shared_libs_) {
	lib_entry->packageId = util::HostToDevice32(map_entry.first);
	strcpy16_htod(lib_entry->packageName, arraysize(lib_entry->packageName),
	util::Utf8ToUtf16(map_entry.second));
	++lib_entry;
	}
	lib_writer.Finish();
	}

	IAaptContext* context_;
	IDiagnostics* diag_;
	ResourceTablePackage* package_;
	const std::map<size_t, std::string>* shared_libs_;
	bool use_sparse_entries_;
	StringPool type_pool_;
	StringPool key_pool_;
	bool collapse_key_stringpool_;
	const std::set<std::string>& whitelisted_resources_;
	};

	} // namespace

	bool TableFlattener::Consume(IAaptContext* context, ResourceTable* table) {
	if (options_.sort_stringpool_entries) {
	// We must do this before writing the resources, since the string pool IDs may change.
	table->string_pool.Prune();
	table->string_pool.Sort([](const StringPool::Context &a, const StringPool::Context &b) -> int {
	int diff = util::compare(a.priority, b.priority);
	if (diff == 0) {
	diff = a.config.compare(b.config);
	}
	return diff;
	});
	}

	// Write the ResTable header.
	ChunkWriter table_writer(buffer_);
	ResTable_header* table_header = table_writer.StartChunk<ResTable_header>(RES_TABLE_TYPE);
	table_header->packageCount = util::HostToDevice32(table->packages.size());

	// Flatten the values string pool.
	StringPool::FlattenUtf8(table_writer.buffer(), table->string_pool,
	context->GetDiagnostics());

	BigBuffer package_buffer(1024);

	// Flatten each package.
	for (auto& package : table->packages) {
	if (context->GetPackageType() == PackageType::kApp) {
	// Write a self mapping entry for this package if the ID is non-standard (0x7f).
	const uint8_t package_id = package->id.value();
	if (package_id != kFrameworkPackageId && package_id != kAppPackageId) {
	auto result = table->included_packages_.insert({package_id, package->name});
	if (!result.second && result.first->second != package->name) {
	// A mapping for this package ID already exists, and is a different package. Error!
	context->GetDiagnostics()->Error(
	DiagMessage() << android::base::StringPrintf(
	"can't map package ID %02x to '%s'. Already mapped to '%s'", package_id,
	package->name.c_str(), result.first->second.c_str()));
	return false;
	}
	}
	}

	PackageFlattener flattener(context, package.get(), &table->included_packages_,
	options_.use_sparse_entries, options_.collapse_key_stringpool,
	options_.whitelisted_resources);
	if (!flattener.FlattenPackage(&package_buffer)) {
	return false;
	}
	}

	// Finally merge all the packages into the main buffer.
	table_writer.buffer()->AppendBuffer(std::move(package_buffer));
	table_writer.Finish();
	return true;
	}

	} // namespace aapt