tools/aapt2/flatten/XmlFlattener.cpp - platform/frameworks/base - Git at Google

 /*
  * 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 "flatten/XmlFlattener.h"

 #include <algorithm>
 #include <map>
 #include <vector>

 #include "android-base/logging.h"
 #include "android-base/macros.h"
 #include "androidfw/ResourceTypes.h"
 #include "utils/misc.h"

 #include "SdkConstants.h"
 #include "flatten/ChunkWriter.h"
 #include "flatten/ResourceTypeExtensions.h"
 #include "xml/XmlDom.h"

 using namespace android;

 namespace aapt {

 namespace {

 constexpr uint32_t kLowPriority = 0xffffffffu;

 static bool cmp_xml_attribute_by_id(const xml::Attribute* a, const xml::Attribute* b) {
   if (a->compiled_attribute && a->compiled_attribute.value().id) {
     if (b->compiled_attribute && b->compiled_attribute.value().id) {
       return a->compiled_attribute.value().id.value() < b->compiled_attribute.value().id.value();
     }
     return true;
   } else if (!b->compiled_attribute) {
     int diff = a->namespace_uri.compare(b->namespace_uri);
     if (diff < 0) {
       return true;
     } else if (diff > 0) {
       return false;
     }
     return a->name < b->name;
   }
   return false;
 }

 class XmlFlattenerVisitor : public xml::Visitor {
  public:
   using xml::Visitor::Visit;

   StringPool pool;
   std::map<uint8_t, StringPool> package_pools;

   struct StringFlattenDest {
     StringPool::Ref ref;
     ResStringPool_ref* dest;
   };

   std::vector<StringFlattenDest> string_refs;

   XmlFlattenerVisitor(BigBuffer* buffer, XmlFlattenerOptions options)
       : buffer_(buffer), options_(options) {}

   void Visit(xml::Text* node) override {
     if (util::TrimWhitespace(node->text).empty()) {
       // Skip whitespace only text nodes.
       return;
     }

     ChunkWriter writer(buffer_);
     ResXMLTree_node* flat_node = writer.StartChunk<ResXMLTree_node>(RES_XML_CDATA_TYPE);
     flat_node->lineNumber = util::HostToDevice32(node->line_number);
     flat_node->comment.index = util::HostToDevice32(-1);

     ResXMLTree_cdataExt* flat_text = writer.NextBlock<ResXMLTree_cdataExt>();

     // Process plain strings to make sure they get properly escaped.
     util::StringBuilder builder;
     builder.Append(node->text);
     AddString(builder.ToString(), kLowPriority, &flat_text->data);

     writer.Finish();
   }

   void Visit(xml::Element* node) override {
     for (const xml::NamespaceDecl& decl : node->namespace_decls) {
       // Skip dedicated tools namespace.
       if (decl.uri != xml::kSchemaTools) {
         WriteNamespace(decl, android::RES_XML_START_NAMESPACE_TYPE);
       }
     }

     {
       ChunkWriter start_writer(buffer_);
       ResXMLTree_node* flat_node =
           start_writer.StartChunk<ResXMLTree_node>(RES_XML_START_ELEMENT_TYPE);
       flat_node->lineNumber = util::HostToDevice32(node->line_number);
       flat_node->comment.index = util::HostToDevice32(-1);

       ResXMLTree_attrExt* flat_elem = start_writer.NextBlock<ResXMLTree_attrExt>();

       // A missing namespace must be null, not an empty string. Otherwise the runtime complains.
       AddString(node->namespace_uri, kLowPriority, &flat_elem->ns,
                 true /* treat_empty_string_as_null */);
       AddString(node->name, kLowPriority, &flat_elem->name, true /* treat_empty_string_as_null */);

       flat_elem->attributeStart = util::HostToDevice16(sizeof(*flat_elem));
       flat_elem->attributeSize = util::HostToDevice16(sizeof(ResXMLTree_attribute));

       WriteAttributes(node, flat_elem, &start_writer);

       start_writer.Finish();
     }

     xml::Visitor::Visit(node);

     {
       ChunkWriter end_writer(buffer_);
       ResXMLTree_node* flat_end_node =
           end_writer.StartChunk<ResXMLTree_node>(RES_XML_END_ELEMENT_TYPE);
       flat_end_node->lineNumber = util::HostToDevice32(node->line_number);
       flat_end_node->comment.index = util::HostToDevice32(-1);

       ResXMLTree_endElementExt* flat_end_elem = end_writer.NextBlock<ResXMLTree_endElementExt>();
       AddString(node->namespace_uri, kLowPriority, &flat_end_elem->ns,
                 true /* treat_empty_string_as_null */);
       AddString(node->name, kLowPriority, &flat_end_elem->name);

       end_writer.Finish();
     }

     for (auto iter = node->namespace_decls.rbegin(); iter != node->namespace_decls.rend(); ++iter) {
       // Skip dedicated tools namespace.
       if (iter->uri != xml::kSchemaTools) {
         WriteNamespace(*iter, android::RES_XML_END_NAMESPACE_TYPE);
       }
     }
   }

  private:
   DISALLOW_COPY_AND_ASSIGN(XmlFlattenerVisitor);

   void AddString(const StringPiece& str, uint32_t priority,
                  android::ResStringPool_ref* dest,
                  bool treat_empty_string_as_null = false) {
     if (str.empty() && treat_empty_string_as_null) {
       // Some parts of the runtime treat null differently than empty string.
       dest->index = util::DeviceToHost32(-1);
     } else {
       string_refs.push_back(StringFlattenDest{
           pool.MakeRef(str, StringPool::Context(priority)), dest});
     }
   }

   void AddString(const StringPool::Ref& ref, android::ResStringPool_ref* dest) {
     string_refs.push_back(StringFlattenDest{ref, dest});
   }

   void WriteNamespace(const xml::NamespaceDecl& decl, uint16_t type) {
     ChunkWriter writer(buffer_);

     ResXMLTree_node* flatNode = writer.StartChunk<ResXMLTree_node>(type);
     flatNode->lineNumber = util::HostToDevice32(decl.line_number);
     flatNode->comment.index = util::HostToDevice32(-1);

     ResXMLTree_namespaceExt* flat_ns = writer.NextBlock<ResXMLTree_namespaceExt>();
     AddString(decl.prefix, kLowPriority, &flat_ns->prefix);
     AddString(decl.uri, kLowPriority, &flat_ns->uri);

     writer.Finish();
   }

   void WriteAttributes(xml::Element* node, ResXMLTree_attrExt* flat_elem, ChunkWriter* writer) {
     filtered_attrs_.clear();
     filtered_attrs_.reserve(node->attributes.size());

     // Filter the attributes.
     for (xml::Attribute& attr : node->attributes) {
       if (attr.namespace_uri != xml::kSchemaTools) {
         filtered_attrs_.push_back(&attr);
       }
     }

     if (filtered_attrs_.empty()) {
       return;
     }

     const ResourceId kIdAttr(0x010100d0);

     std::sort(filtered_attrs_.begin(), filtered_attrs_.end(), cmp_xml_attribute_by_id);

     flat_elem->attributeCount = util::HostToDevice16(filtered_attrs_.size());

     ResXMLTree_attribute* flat_attr =
         writer->NextBlock<ResXMLTree_attribute>(filtered_attrs_.size());
     uint16_t attribute_index = 1;
     for (const xml::Attribute* xml_attr : filtered_attrs_) {
       // Assign the indices for specific attributes.
       if (xml_attr->compiled_attribute &&
           xml_attr->compiled_attribute.value().id &&
           xml_attr->compiled_attribute.value().id.value() == kIdAttr) {
         flat_elem->idIndex = util::HostToDevice16(attribute_index);
       } else if (xml_attr->namespace_uri.empty()) {
         if (xml_attr->name == "class") {
           flat_elem->classIndex = util::HostToDevice16(attribute_index);
         } else if (xml_attr->name == "style") {
           flat_elem->styleIndex = util::HostToDevice16(attribute_index);
         }
       }
       attribute_index++;

       // Add the namespaceUri to the list of StringRefs to encode. Use null if the namespace
       // is empty (doesn't exist).
       AddString(xml_attr->namespace_uri, kLowPriority, &flat_attr->ns,
                 true /* treat_empty_string_as_null */);

       flat_attr->rawValue.index = util::HostToDevice32(-1);

       if (!xml_attr->compiled_attribute || !xml_attr->compiled_attribute.value().id) {
         // The attribute has no associated ResourceID, so the string order doesn't matter.
         AddString(xml_attr->name, kLowPriority, &flat_attr->name);
       } else {
         // Attribute names are stored without packages, but we use
         // their StringPool index to lookup their resource IDs.
         // This will cause collisions, so we can't dedupe
         // attribute names from different packages. We use separate
         // pools that we later combine.
         //
         // Lookup the StringPool for this package and make the reference there.
         const xml::AaptAttribute& aapt_attr = xml_attr->compiled_attribute.value();

         StringPool::Ref name_ref =
             package_pools[aapt_attr.id.value().package_id()].MakeRef(
                 xml_attr->name, StringPool::Context(aapt_attr.id.value().id));

         // Add it to the list of strings to flatten.
         AddString(name_ref, &flat_attr->name);
       }

       // Process plain strings to make sure they get properly escaped.
       StringPiece raw_value = xml_attr->value;

       util::StringBuilder str_builder(true /*preserve_spaces*/);
       str_builder.Append(xml_attr->value);

       if (!options_.keep_raw_values) {
         raw_value = str_builder.ToString();
       }

       if (options_.keep_raw_values || !xml_attr->compiled_value) {
         // Keep raw values if the value is not compiled or
         // if we're building a static library (need symbols).
         AddString(raw_value, kLowPriority, &flat_attr->rawValue);
       }

       if (xml_attr->compiled_value) {
         CHECK(xml_attr->compiled_value->Flatten(&flat_attr->typedValue));
       } else {
         // Flatten as a regular string type.
         flat_attr->typedValue.dataType = android::Res_value::TYPE_STRING;

         AddString(str_builder.ToString(), kLowPriority,
                   (ResStringPool_ref*) &flat_attr->typedValue.data);
       }

       flat_attr->typedValue.size = util::HostToDevice16(sizeof(flat_attr->typedValue));
       flat_attr++;
     }
   }

   BigBuffer* buffer_;
   XmlFlattenerOptions options_;

   // Scratch vector to filter attributes. We avoid allocations making this a member.
   std::vector<xml::Attribute*> filtered_attrs_;
 };

 }  // namespace

 bool XmlFlattener::Flatten(IAaptContext* context, xml::Node* node) {
   BigBuffer node_buffer(1024);
   XmlFlattenerVisitor visitor(&node_buffer, options_);
   node->Accept(&visitor);

   // Merge the package pools into the main pool.
   for (auto& package_pool_entry : visitor.package_pools) {
     visitor.pool.Merge(std::move(package_pool_entry.second));
   }

   // Sort the string pool so that attribute resource IDs show up first.
   visitor.pool.Sort([](const StringPool::Context& a, const StringPool::Context& b) -> int {
     return util::compare(a.priority, b.priority);
   });

   // Now we flatten the string pool references into the correct places.
   for (const auto& ref_entry : visitor.string_refs) {
     ref_entry.dest->index = util::HostToDevice32(ref_entry.ref.index());
   }

   // Write the XML header.
   ChunkWriter xml_header_writer(buffer_);
   xml_header_writer.StartChunk<ResXMLTree_header>(RES_XML_TYPE);

   // Flatten the StringPool.
   if (options_.use_utf16) {
     StringPool::FlattenUtf16(buffer_, visitor.pool);
   } else {
     StringPool::FlattenUtf8(buffer_, visitor.pool);
   }

   {
     // Write the array of resource IDs, indexed by StringPool order.
     ChunkWriter res_id_map_writer(buffer_);
     res_id_map_writer.StartChunk<ResChunk_header>(RES_XML_RESOURCE_MAP_TYPE);
     for (const auto& str : visitor.pool.strings()) {
       ResourceId id(str->context.priority);
       if (str->context.priority == kLowPriority || !id.is_valid()) {
         // When we see the first non-resource ID, we're done.
         break;
       }
       *res_id_map_writer.NextBlock<uint32_t>() = util::HostToDevice32(id.id);
     }
     res_id_map_writer.Finish();
   }

   // Move the nodeBuffer and append it to the out buffer.
   buffer_->AppendBuffer(std::move(node_buffer));

   // Finish the xml header.
   xml_header_writer.Finish();
   return true;
 }

 bool XmlFlattener::Consume(IAaptContext* context, xml::XmlResource* resource) {
   if (!resource->root) {
     return false;
   }
   return Flatten(context, resource->root.get());
 }

 }  // 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 "flatten/XmlFlattener.h"

	#include <algorithm>
	#include <map>
	#include <vector>

	#include "android-base/logging.h"
	#include "android-base/macros.h"
	#include "androidfw/ResourceTypes.h"
	#include "utils/misc.h"

	#include "SdkConstants.h"
	#include "flatten/ChunkWriter.h"
	#include "flatten/ResourceTypeExtensions.h"
	#include "xml/XmlDom.h"

	using namespace android;

	namespace aapt {

	namespace {

	constexpr uint32_t kLowPriority = 0xffffffffu;

	static bool cmp_xml_attribute_by_id(const xml::Attribute* a, const xml::Attribute* b) {
	if (a->compiled_attribute && a->compiled_attribute.value().id) {
	if (b->compiled_attribute && b->compiled_attribute.value().id) {
	return a->compiled_attribute.value().id.value() < b->compiled_attribute.value().id.value();
	}
	return true;
	} else if (!b->compiled_attribute) {
	int diff = a->namespace_uri.compare(b->namespace_uri);
	if (diff < 0) {
	return true;
	} else if (diff > 0) {
	return false;
	}
	return a->name < b->name;
	}
	return false;
	}

	class XmlFlattenerVisitor : public xml::Visitor {
	public:
	using xml::Visitor::Visit;

	StringPool pool;
	std::map<uint8_t, StringPool> package_pools;

	struct StringFlattenDest {
	StringPool::Ref ref;
	ResStringPool_ref* dest;
	};

	std::vector<StringFlattenDest> string_refs;

	XmlFlattenerVisitor(BigBuffer* buffer, XmlFlattenerOptions options)
	: buffer_(buffer), options_(options) {}

	void Visit(xml::Text* node) override {
	if (util::TrimWhitespace(node->text).empty()) {
	// Skip whitespace only text nodes.
	return;
	}

	ChunkWriter writer(buffer_);
	ResXMLTree_node* flat_node = writer.StartChunk<ResXMLTree_node>(RES_XML_CDATA_TYPE);
	flat_node->lineNumber = util::HostToDevice32(node->line_number);
	flat_node->comment.index = util::HostToDevice32(-1);

	ResXMLTree_cdataExt* flat_text = writer.NextBlock<ResXMLTree_cdataExt>();

	// Process plain strings to make sure they get properly escaped.
	util::StringBuilder builder;
	builder.Append(node->text);
	AddString(builder.ToString(), kLowPriority, &flat_text->data);

	writer.Finish();
	}

	void Visit(xml::Element* node) override {
	for (const xml::NamespaceDecl& decl : node->namespace_decls) {
	// Skip dedicated tools namespace.
	if (decl.uri != xml::kSchemaTools) {
	WriteNamespace(decl, android::RES_XML_START_NAMESPACE_TYPE);
	}
	}

	{
	ChunkWriter start_writer(buffer_);
	ResXMLTree_node* flat_node =
	start_writer.StartChunk<ResXMLTree_node>(RES_XML_START_ELEMENT_TYPE);
	flat_node->lineNumber = util::HostToDevice32(node->line_number);
	flat_node->comment.index = util::HostToDevice32(-1);

	ResXMLTree_attrExt* flat_elem = start_writer.NextBlock<ResXMLTree_attrExt>();

	// A missing namespace must be null, not an empty string. Otherwise the runtime complains.
	AddString(node->namespace_uri, kLowPriority, &flat_elem->ns,
	true /* treat_empty_string_as_null */);
	AddString(node->name, kLowPriority, &flat_elem->name, true /* treat_empty_string_as_null */);

	flat_elem->attributeStart = util::HostToDevice16(sizeof(*flat_elem));
	flat_elem->attributeSize = util::HostToDevice16(sizeof(ResXMLTree_attribute));

	WriteAttributes(node, flat_elem, &start_writer);

	start_writer.Finish();
	}

	xml::Visitor::Visit(node);

	{
	ChunkWriter end_writer(buffer_);
	ResXMLTree_node* flat_end_node =
	end_writer.StartChunk<ResXMLTree_node>(RES_XML_END_ELEMENT_TYPE);
	flat_end_node->lineNumber = util::HostToDevice32(node->line_number);
	flat_end_node->comment.index = util::HostToDevice32(-1);

	ResXMLTree_endElementExt* flat_end_elem = end_writer.NextBlock<ResXMLTree_endElementExt>();
	AddString(node->namespace_uri, kLowPriority, &flat_end_elem->ns,
	true /* treat_empty_string_as_null */);
	AddString(node->name, kLowPriority, &flat_end_elem->name);

	end_writer.Finish();
	}

	for (auto iter = node->namespace_decls.rbegin(); iter != node->namespace_decls.rend(); ++iter) {
	// Skip dedicated tools namespace.
	if (iter->uri != xml::kSchemaTools) {
	WriteNamespace(*iter, android::RES_XML_END_NAMESPACE_TYPE);
	}
	}
	}

	private:
	DISALLOW_COPY_AND_ASSIGN(XmlFlattenerVisitor);

	void AddString(const StringPiece& str, uint32_t priority,
	android::ResStringPool_ref* dest,
	bool treat_empty_string_as_null = false) {
	if (str.empty() && treat_empty_string_as_null) {
	// Some parts of the runtime treat null differently than empty string.
	dest->index = util::DeviceToHost32(-1);
	} else {
	string_refs.push_back(StringFlattenDest{
	pool.MakeRef(str, StringPool::Context(priority)), dest});
	}
	}

	void AddString(const StringPool::Ref& ref, android::ResStringPool_ref* dest) {
	string_refs.push_back(StringFlattenDest{ref, dest});
	}

	void WriteNamespace(const xml::NamespaceDecl& decl, uint16_t type) {
	ChunkWriter writer(buffer_);

	ResXMLTree_node* flatNode = writer.StartChunk<ResXMLTree_node>(type);
	flatNode->lineNumber = util::HostToDevice32(decl.line_number);
	flatNode->comment.index = util::HostToDevice32(-1);

	ResXMLTree_namespaceExt* flat_ns = writer.NextBlock<ResXMLTree_namespaceExt>();
	AddString(decl.prefix, kLowPriority, &flat_ns->prefix);
	AddString(decl.uri, kLowPriority, &flat_ns->uri);

	writer.Finish();
	}

	void WriteAttributes(xml::Element* node, ResXMLTree_attrExt* flat_elem, ChunkWriter* writer) {
	filtered_attrs_.clear();
	filtered_attrs_.reserve(node->attributes.size());

	// Filter the attributes.
	for (xml::Attribute& attr : node->attributes) {
	if (attr.namespace_uri != xml::kSchemaTools) {
	filtered_attrs_.push_back(&attr);
	}
	}

	if (filtered_attrs_.empty()) {
	return;
	}

	const ResourceId kIdAttr(0x010100d0);

	std::sort(filtered_attrs_.begin(), filtered_attrs_.end(), cmp_xml_attribute_by_id);

	flat_elem->attributeCount = util::HostToDevice16(filtered_attrs_.size());

	ResXMLTree_attribute* flat_attr =
	writer->NextBlock<ResXMLTree_attribute>(filtered_attrs_.size());
	uint16_t attribute_index = 1;
	for (const xml::Attribute* xml_attr : filtered_attrs_) {
	// Assign the indices for specific attributes.
	if (xml_attr->compiled_attribute &&
	xml_attr->compiled_attribute.value().id &&
	xml_attr->compiled_attribute.value().id.value() == kIdAttr) {
	flat_elem->idIndex = util::HostToDevice16(attribute_index);
	} else if (xml_attr->namespace_uri.empty()) {
	if (xml_attr->name == "class") {
	flat_elem->classIndex = util::HostToDevice16(attribute_index);
	} else if (xml_attr->name == "style") {
	flat_elem->styleIndex = util::HostToDevice16(attribute_index);
	}
	}
	attribute_index++;

	// Add the namespaceUri to the list of StringRefs to encode. Use null if the namespace
	// is empty (doesn't exist).
	AddString(xml_attr->namespace_uri, kLowPriority, &flat_attr->ns,
	true /* treat_empty_string_as_null */);

	flat_attr->rawValue.index = util::HostToDevice32(-1);

	if (!xml_attr->compiled_attribute \|\| !xml_attr->compiled_attribute.value().id) {
	// The attribute has no associated ResourceID, so the string order doesn't matter.
	AddString(xml_attr->name, kLowPriority, &flat_attr->name);
	} else {
	// Attribute names are stored without packages, but we use
	// their StringPool index to lookup their resource IDs.
	// This will cause collisions, so we can't dedupe
	// attribute names from different packages. We use separate
	// pools that we later combine.
	//
	// Lookup the StringPool for this package and make the reference there.
	const xml::AaptAttribute& aapt_attr = xml_attr->compiled_attribute.value();

	StringPool::Ref name_ref =
	package_pools[aapt_attr.id.value().package_id()].MakeRef(
	xml_attr->name, StringPool::Context(aapt_attr.id.value().id));

	// Add it to the list of strings to flatten.
	AddString(name_ref, &flat_attr->name);
	}

	// Process plain strings to make sure they get properly escaped.
	StringPiece raw_value = xml_attr->value;

	util::StringBuilder str_builder(true /preserve_spaces/);
	str_builder.Append(xml_attr->value);

	if (!options_.keep_raw_values) {
	raw_value = str_builder.ToString();
	}

	if (options_.keep_raw_values \|\| !xml_attr->compiled_value) {
	// Keep raw values if the value is not compiled or
	// if we're building a static library (need symbols).
	AddString(raw_value, kLowPriority, &flat_attr->rawValue);
	}

	if (xml_attr->compiled_value) {
	CHECK(xml_attr->compiled_value->Flatten(&flat_attr->typedValue));
	} else {
	// Flatten as a regular string type.
	flat_attr->typedValue.dataType = android::Res_value::TYPE_STRING;

	AddString(str_builder.ToString(), kLowPriority,
	(ResStringPool_ref*) &flat_attr->typedValue.data);
	}

	flat_attr->typedValue.size = util::HostToDevice16(sizeof(flat_attr->typedValue));
	flat_attr++;
	}
	}

	BigBuffer* buffer_;
	XmlFlattenerOptions options_;

	// Scratch vector to filter attributes. We avoid allocations making this a member.
	std::vector<xml::Attribute*> filtered_attrs_;
	};

	} // namespace

	bool XmlFlattener::Flatten(IAaptContext* context, xml::Node* node) {
	BigBuffer node_buffer(1024);
	XmlFlattenerVisitor visitor(&node_buffer, options_);
	node->Accept(&visitor);

	// Merge the package pools into the main pool.
	for (auto& package_pool_entry : visitor.package_pools) {
	visitor.pool.Merge(std::move(package_pool_entry.second));
	}

	// Sort the string pool so that attribute resource IDs show up first.
	visitor.pool.Sort([](const StringPool::Context& a, const StringPool::Context& b) -> int {
	return util::compare(a.priority, b.priority);
	});

	// Now we flatten the string pool references into the correct places.
	for (const auto& ref_entry : visitor.string_refs) {
	ref_entry.dest->index = util::HostToDevice32(ref_entry.ref.index());
	}

	// Write the XML header.
	ChunkWriter xml_header_writer(buffer_);
	xml_header_writer.StartChunk<ResXMLTree_header>(RES_XML_TYPE);

	// Flatten the StringPool.
	if (options_.use_utf16) {
	StringPool::FlattenUtf16(buffer_, visitor.pool);
	} else {
	StringPool::FlattenUtf8(buffer_, visitor.pool);
	}

	{
	// Write the array of resource IDs, indexed by StringPool order.
	ChunkWriter res_id_map_writer(buffer_);
	res_id_map_writer.StartChunk<ResChunk_header>(RES_XML_RESOURCE_MAP_TYPE);
	for (const auto& str : visitor.pool.strings()) {
	ResourceId id(str->context.priority);
	if (str->context.priority == kLowPriority \|\| !id.is_valid()) {
	// When we see the first non-resource ID, we're done.
	break;
	}
	*res_id_map_writer.NextBlock<uint32_t>() = util::HostToDevice32(id.id);
	}
	res_id_map_writer.Finish();
	}

	// Move the nodeBuffer and append it to the out buffer.
	buffer_->AppendBuffer(std::move(node_buffer));

	// Finish the xml header.
	xml_header_writer.Finish();
	return true;
	}

	bool XmlFlattener::Consume(IAaptContext* context, xml::XmlResource* resource) {
	if (!resource->root) {
	return false;
	}
	return Flatten(context, resource->root.get());
	}

	} // namespace aapt