tools/aapt2/xml/XmlDom.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 "XmlDom.h"
 #include "XmlPullParser.h"
 #include "util/Util.h"

 #include <cassert>
 #include <expat.h>
 #include <memory>
 #include <stack>
 #include <string>
 #include <tuple>

 namespace aapt {
 namespace xml {

 constexpr char kXmlNamespaceSep = 1;

 struct Stack {
     std::unique_ptr<xml::Node> root;
     std::stack<xml::Node*> nodeStack;
     std::u16string pendingComment;
 };

 /**
  * Extracts the namespace and name of an expanded element or attribute name.
  */
 static void splitName(const char* name, std::u16string* outNs, std::u16string* outName) {
     const char* p = name;
     while (*p != 0 && *p != kXmlNamespaceSep) {
         p++;
     }

     if (*p == 0) {
         outNs->clear();
         *outName = util::utf8ToUtf16(name);
     } else {
         *outNs = util::utf8ToUtf16(StringPiece(name, (p - name)));
         *outName = util::utf8ToUtf16(p + 1);
     }
 }

 static void addToStack(Stack* stack, XML_Parser parser, std::unique_ptr<Node> node) {
     node->lineNumber = XML_GetCurrentLineNumber(parser);
     node->columnNumber = XML_GetCurrentColumnNumber(parser);

     Node* thisNode = node.get();
     if (!stack->nodeStack.empty()) {
         stack->nodeStack.top()->addChild(std::move(node));
     } else {
         stack->root = std::move(node);
     }

     if (!nodeCast<Text>(thisNode)) {
         stack->nodeStack.push(thisNode);
     }
 }

 static void XMLCALL startNamespaceHandler(void* userData, const char* prefix, const char* uri) {
     XML_Parser parser = reinterpret_cast<XML_Parser>(userData);
     Stack* stack = reinterpret_cast<Stack*>(XML_GetUserData(parser));

     std::unique_ptr<Namespace> ns = util::make_unique<Namespace>();
     if (prefix) {
         ns->namespacePrefix = util::utf8ToUtf16(prefix);
     }

     if (uri) {
         ns->namespaceUri = util::utf8ToUtf16(uri);
     }

     addToStack(stack, parser, std::move(ns));
 }

 static void XMLCALL endNamespaceHandler(void* userData, const char* prefix) {
     XML_Parser parser = reinterpret_cast<XML_Parser>(userData);
     Stack* stack = reinterpret_cast<Stack*>(XML_GetUserData(parser));

     assert(!stack->nodeStack.empty());
     stack->nodeStack.pop();
 }

 static bool lessAttribute(const Attribute& lhs, const Attribute& rhs) {
     return std::tie(lhs.namespaceUri, lhs.name, lhs.value) <
             std::tie(rhs.namespaceUri, rhs.name, rhs.value);
 }

 static void XMLCALL startElementHandler(void* userData, const char* name, const char** attrs) {
     XML_Parser parser = reinterpret_cast<XML_Parser>(userData);
     Stack* stack = reinterpret_cast<Stack*>(XML_GetUserData(parser));

     std::unique_ptr<Element> el = util::make_unique<Element>();
     splitName(name, &el->namespaceUri, &el->name);

     while (*attrs) {
         Attribute attribute;
         splitName(*attrs++, &attribute.namespaceUri, &attribute.name);
         attribute.value = util::utf8ToUtf16(*attrs++);

         // Insert in sorted order.
         auto iter = std::lower_bound(el->attributes.begin(), el->attributes.end(), attribute,
                                      lessAttribute);
         el->attributes.insert(iter, std::move(attribute));
     }

     el->comment = std::move(stack->pendingComment);
     addToStack(stack, parser, std::move(el));
 }

 static void XMLCALL endElementHandler(void* userData, const char* name) {
     XML_Parser parser = reinterpret_cast<XML_Parser>(userData);
     Stack* stack = reinterpret_cast<Stack*>(XML_GetUserData(parser));

     assert(!stack->nodeStack.empty());
     //stack->nodeStack.top()->comment = std::move(stack->pendingComment);
     stack->nodeStack.pop();
 }

 static void XMLCALL characterDataHandler(void* userData, const char* s, int len) {
     XML_Parser parser = reinterpret_cast<XML_Parser>(userData);
     Stack* stack = reinterpret_cast<Stack*>(XML_GetUserData(parser));

     if (!s || len <= 0) {
         return;
     }

     // See if we can just append the text to a previous text node.
     if (!stack->nodeStack.empty()) {
         Node* currentParent = stack->nodeStack.top();
         if (!currentParent->children.empty()) {
             Node* lastChild = currentParent->children.back().get();
             if (Text* text = nodeCast<Text>(lastChild)) {
                 text->text += util::utf8ToUtf16(StringPiece(s, len));
                 return;
             }
         }
     }

     std::unique_ptr<Text> text = util::make_unique<Text>();
     text->text = util::utf8ToUtf16(StringPiece(s, len));
     addToStack(stack, parser, std::move(text));
 }

 static void XMLCALL commentDataHandler(void* userData, const char* comment) {
     XML_Parser parser = reinterpret_cast<XML_Parser>(userData);
     Stack* stack = reinterpret_cast<Stack*>(XML_GetUserData(parser));

     if (!stack->pendingComment.empty()) {
         stack->pendingComment += '\n';
     }
     stack->pendingComment += util::utf8ToUtf16(comment);
 }

 std::unique_ptr<XmlResource> inflate(std::istream* in, IDiagnostics* diag, const Source& source) {
     Stack stack;

     XML_Parser parser = XML_ParserCreateNS(nullptr, kXmlNamespaceSep);
     XML_SetUserData(parser, &stack);
     XML_UseParserAsHandlerArg(parser);
     XML_SetElementHandler(parser, startElementHandler, endElementHandler);
     XML_SetNamespaceDeclHandler(parser, startNamespaceHandler, endNamespaceHandler);
     XML_SetCharacterDataHandler(parser, characterDataHandler);
     XML_SetCommentHandler(parser, commentDataHandler);

     char buffer[1024];
     while (!in->eof()) {
         in->read(buffer, sizeof(buffer) / sizeof(buffer[0]));
         if (in->bad() && !in->eof()) {
             stack.root = {};
             diag->error(DiagMessage(source) << strerror(errno));
             break;
         }

         if (XML_Parse(parser, buffer, in->gcount(), in->eof()) == XML_STATUS_ERROR) {
             stack.root = {};
             diag->error(DiagMessage(source.withLine(XML_GetCurrentLineNumber(parser)))
                         << XML_ErrorString(XML_GetErrorCode(parser)));
             break;
         }
     }

     XML_ParserFree(parser);
     if (stack.root) {
         return util::make_unique<XmlResource>(ResourceFile{ {}, {}, source }, std::move(stack.root));
     }
     return {};
 }

 static void copyAttributes(Element* el, android::ResXMLParser* parser) {
     const size_t attrCount = parser->getAttributeCount();
     if (attrCount > 0) {
         el->attributes.reserve(attrCount);
         for (size_t i = 0; i < attrCount; i++) {
             Attribute attr;
             size_t len;
             const char16_t* str16 = parser->getAttributeNamespace(i, &len);
             if (str16) {
                 attr.namespaceUri.assign(str16, len);
             }

             str16 = parser->getAttributeName(i, &len);
             if (str16) {
                 attr.name.assign(str16, len);
             }

             str16 = parser->getAttributeStringValue(i, &len);
             if (str16) {
                 attr.value.assign(str16, len);
             }
             el->attributes.push_back(std::move(attr));
         }
     }
 }

 std::unique_ptr<XmlResource> inflate(const void* data, size_t dataLen, IDiagnostics* diag,
                                      const Source& source) {
     // We import the android namespace because on Windows NO_ERROR is a macro, not an enum, which
     // causes errors when qualifying it with android::
     using namespace android;

     std::unique_ptr<Node> root;
     std::stack<Node*> nodeStack;

     ResXMLTree tree;
     if (tree.setTo(data, dataLen) != NO_ERROR) {
         return {};
     }

     ResXMLParser::event_code_t code;
     while ((code = tree.next()) != ResXMLParser::BAD_DOCUMENT &&
             code != ResXMLParser::END_DOCUMENT) {
         std::unique_ptr<Node> newNode;
         switch (code) {
             case ResXMLParser::START_NAMESPACE: {
                 std::unique_ptr<Namespace> node = util::make_unique<Namespace>();
                 size_t len;
                 const char16_t* str16 = tree.getNamespacePrefix(&len);
                 if (str16) {
                     node->namespacePrefix.assign(str16, len);
                 }

                 str16 = tree.getNamespaceUri(&len);
                 if (str16) {
                     node->namespaceUri.assign(str16, len);
                 }
                 newNode = std::move(node);
                 break;
             }

             case ResXMLParser::START_TAG: {
                 std::unique_ptr<Element> node = util::make_unique<Element>();
                 size_t len;
                 const char16_t* str16 = tree.getElementNamespace(&len);
                 if (str16) {
                     node->namespaceUri.assign(str16, len);
                 }

                 str16 = tree.getElementName(&len);
                 if (str16) {
                     node->name.assign(str16, len);
                 }

                 copyAttributes(node.get(), &tree);

                 newNode = std::move(node);
                 break;
             }

             case ResXMLParser::TEXT: {
                 std::unique_ptr<Text> node = util::make_unique<Text>();
                 size_t len;
                 const char16_t* str16 = tree.getText(&len);
                 if (str16) {
                     node->text.assign(str16, len);
                 }
                 newNode = std::move(node);
                 break;
             }

             case ResXMLParser::END_NAMESPACE:
             case ResXMLParser::END_TAG:
                 assert(!nodeStack.empty());
                 nodeStack.pop();
                 break;

             default:
                 assert(false);
                 break;
         }

         if (newNode) {
             newNode->lineNumber = tree.getLineNumber();

             Node* thisNode = newNode.get();
             if (!root) {
                 assert(nodeStack.empty());
                 root = std::move(newNode);
             } else {
                 assert(!nodeStack.empty());
                 nodeStack.top()->addChild(std::move(newNode));
             }

             if (!nodeCast<Text>(thisNode)) {
                 nodeStack.push(thisNode);
             }
         }
     }
     return util::make_unique<XmlResource>(ResourceFile{}, std::move(root));
 }

 Element* findRootElement(XmlResource* doc) {
     return findRootElement(doc->root.get());
 }

 Element* findRootElement(Node* node) {
     if (!node) {
         return nullptr;
     }

     Element* el = nullptr;
     while ((el = nodeCast<Element>(node)) == nullptr) {
         if (node->children.empty()) {
             return nullptr;
         }
         // We are looking for the first element, and namespaces can only have one child.
         node = node->children.front().get();
     }
     return el;
 }

 void Node::addChild(std::unique_ptr<Node> child) {
     child->parent = this;
     children.push_back(std::move(child));
 }

 Attribute* Element::findAttribute(const StringPiece16& ns, const StringPiece16& name) {
     for (auto& attr : attributes) {
         if (ns == attr.namespaceUri && name == attr.name) {
             return &attr;
         }
     }
     return nullptr;
 }

 Element* Element::findChild(const StringPiece16& ns, const StringPiece16& name) {
     return findChildWithAttribute(ns, name, {}, {}, {});
 }

 Element* Element::findChildWithAttribute(const StringPiece16& ns, const StringPiece16& name,
                                          const StringPiece16& attrNs, const StringPiece16& attrName,
                                          const StringPiece16& attrValue) {
     for (auto& childNode : children) {
         Node* child = childNode.get();
         while (nodeCast<Namespace>(child)) {
             if (child->children.empty()) {
                 break;
             }
             child = child->children[0].get();
         }

         if (Element* el = nodeCast<Element>(child)) {
             if (ns == el->namespaceUri && name == el->name) {
                 if (attrNs.empty() && attrName.empty()) {
                     return el;
                 }

                 Attribute* attr = el->findAttribute(attrNs, attrName);
                 if (attr && attrValue == attr->value) {
                     return el;
                 }
             }
         }
     }
     return nullptr;
 }

 std::vector<Element*> Element::getChildElements() {
     std::vector<Element*> elements;
     for (auto& childNode : children) {
         Node* child = childNode.get();
         while (nodeCast<Namespace>(child)) {
             if (child->children.empty()) {
                 break;
             }
             child = child->children[0].get();
         }

         if (Element* el = nodeCast<Element>(child)) {
             elements.push_back(el);
         }
     }
     return elements;
 }

 void PackageAwareVisitor::visit(Namespace* ns) {
    bool added = false;
    if (Maybe<ExtractedPackage> maybePackage = extractPackageFromNamespace(ns->namespaceUri)) {
        ExtractedPackage& package = maybePackage.value();
        mPackageDecls.push_back(PackageDecl{ ns->namespacePrefix, std::move(package) });
        added = true;
    }

    Visitor::visit(ns);

    if (added) {
        mPackageDecls.pop_back();
    }
 }

 Maybe<ExtractedPackage> PackageAwareVisitor::transformPackageAlias(
        const StringPiece16& alias, const StringPiece16& localPackage) const {
    if (alias.empty()) {
        return ExtractedPackage{ localPackage.toString(), false /* private */ };
    }

    const auto rend = mPackageDecls.rend();
    for (auto iter = mPackageDecls.rbegin(); iter != rend; ++iter) {
        if (alias == iter->prefix) {
            if (iter->package.package.empty()) {
                return ExtractedPackage{ localPackage.toString(),
                                               iter->package.privateNamespace };
            }
            return iter->package;
        }
    }
    return {};
 }

 } // namespace xml
 } // 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 "XmlDom.h"
	#include "XmlPullParser.h"
	#include "util/Util.h"

	#include <cassert>
	#include <expat.h>
	#include <memory>
	#include <stack>
	#include <string>
	#include <tuple>

	namespace aapt {
	namespace xml {

	constexpr char kXmlNamespaceSep = 1;

	struct Stack {
	std::unique_ptr<xml::Node> root;
	std::stack<xml::Node*> nodeStack;
	std::u16string pendingComment;
	};

	/**
	* Extracts the namespace and name of an expanded element or attribute name.
	*/
	static void splitName(const char* name, std::u16string* outNs, std::u16string* outName) {
	const char* p = name;
	while (p != 0 && p != kXmlNamespaceSep) {
	p++;
	}

	if (*p == 0) {
	outNs->clear();
	*outName = util::utf8ToUtf16(name);
	} else {
	*outNs = util::utf8ToUtf16(StringPiece(name, (p - name)));
	*outName = util::utf8ToUtf16(p + 1);
	}
	}

	static void addToStack(Stack* stack, XML_Parser parser, std::unique_ptr<Node> node) {
	node->lineNumber = XML_GetCurrentLineNumber(parser);
	node->columnNumber = XML_GetCurrentColumnNumber(parser);

	Node* thisNode = node.get();
	if (!stack->nodeStack.empty()) {
	stack->nodeStack.top()->addChild(std::move(node));
	} else {
	stack->root = std::move(node);
	}

	if (!nodeCast<Text>(thisNode)) {
	stack->nodeStack.push(thisNode);
	}
	}

	static void XMLCALL startNamespaceHandler(void* userData, const char* prefix, const char* uri) {
	XML_Parser parser = reinterpret_cast<XML_Parser>(userData);
	Stack* stack = reinterpret_cast<Stack*>(XML_GetUserData(parser));

	std::unique_ptr<Namespace> ns = util::make_unique<Namespace>();
	if (prefix) {
	ns->namespacePrefix = util::utf8ToUtf16(prefix);
	}

	if (uri) {
	ns->namespaceUri = util::utf8ToUtf16(uri);
	}

	addToStack(stack, parser, std::move(ns));
	}

	static void XMLCALL endNamespaceHandler(void* userData, const char* prefix) {
	XML_Parser parser = reinterpret_cast<XML_Parser>(userData);
	Stack* stack = reinterpret_cast<Stack*>(XML_GetUserData(parser));

	assert(!stack->nodeStack.empty());
	stack->nodeStack.pop();
	}

	static bool lessAttribute(const Attribute& lhs, const Attribute& rhs) {
	return std::tie(lhs.namespaceUri, lhs.name, lhs.value) <
	std::tie(rhs.namespaceUri, rhs.name, rhs.value);
	}

	static void XMLCALL startElementHandler(void* userData, const char* name, const char** attrs) {
	XML_Parser parser = reinterpret_cast<XML_Parser>(userData);
	Stack* stack = reinterpret_cast<Stack*>(XML_GetUserData(parser));

	std::unique_ptr<Element> el = util::make_unique<Element>();
	splitName(name, &el->namespaceUri, &el->name);

	while (*attrs) {
	Attribute attribute;
	splitName(*attrs++, &attribute.namespaceUri, &attribute.name);
	attribute.value = util::utf8ToUtf16(*attrs++);

	// Insert in sorted order.
	auto iter = std::lower_bound(el->attributes.begin(), el->attributes.end(), attribute,
	lessAttribute);
	el->attributes.insert(iter, std::move(attribute));
	}

	el->comment = std::move(stack->pendingComment);
	addToStack(stack, parser, std::move(el));
	}

	static void XMLCALL endElementHandler(void* userData, const char* name) {
	XML_Parser parser = reinterpret_cast<XML_Parser>(userData);
	Stack* stack = reinterpret_cast<Stack*>(XML_GetUserData(parser));

	assert(!stack->nodeStack.empty());
	//stack->nodeStack.top()->comment = std::move(stack->pendingComment);
	stack->nodeStack.pop();
	}

	static void XMLCALL characterDataHandler(void* userData, const char* s, int len) {
	XML_Parser parser = reinterpret_cast<XML_Parser>(userData);
	Stack* stack = reinterpret_cast<Stack*>(XML_GetUserData(parser));

	if (!s \|\| len <= 0) {
	return;
	}

	// See if we can just append the text to a previous text node.
	if (!stack->nodeStack.empty()) {
	Node* currentParent = stack->nodeStack.top();
	if (!currentParent->children.empty()) {
	Node* lastChild = currentParent->children.back().get();
	if (Text* text = nodeCast<Text>(lastChild)) {
	text->text += util::utf8ToUtf16(StringPiece(s, len));
	return;
	}
	}
	}

	std::unique_ptr<Text> text = util::make_unique<Text>();
	text->text = util::utf8ToUtf16(StringPiece(s, len));
	addToStack(stack, parser, std::move(text));
	}

	static void XMLCALL commentDataHandler(void* userData, const char* comment) {
	XML_Parser parser = reinterpret_cast<XML_Parser>(userData);
	Stack* stack = reinterpret_cast<Stack*>(XML_GetUserData(parser));

	if (!stack->pendingComment.empty()) {
	stack->pendingComment += '\n';
	}
	stack->pendingComment += util::utf8ToUtf16(comment);
	}

	std::unique_ptr<XmlResource> inflate(std::istream* in, IDiagnostics* diag, const Source& source) {
	Stack stack;

	XML_Parser parser = XML_ParserCreateNS(nullptr, kXmlNamespaceSep);
	XML_SetUserData(parser, &stack);
	XML_UseParserAsHandlerArg(parser);
	XML_SetElementHandler(parser, startElementHandler, endElementHandler);
	XML_SetNamespaceDeclHandler(parser, startNamespaceHandler, endNamespaceHandler);
	XML_SetCharacterDataHandler(parser, characterDataHandler);
	XML_SetCommentHandler(parser, commentDataHandler);

	char buffer[1024];
	while (!in->eof()) {
	in->read(buffer, sizeof(buffer) / sizeof(buffer[0]));
	if (in->bad() && !in->eof()) {
	stack.root = {};
	diag->error(DiagMessage(source) << strerror(errno));
	break;
	}

	if (XML_Parse(parser, buffer, in->gcount(), in->eof()) == XML_STATUS_ERROR) {
	stack.root = {};
	diag->error(DiagMessage(source.withLine(XML_GetCurrentLineNumber(parser)))
	<< XML_ErrorString(XML_GetErrorCode(parser)));
	break;
	}
	}

	XML_ParserFree(parser);
	if (stack.root) {
	return util::make_unique<XmlResource>(ResourceFile{ {}, {}, source }, std::move(stack.root));
	}
	return {};
	}

	static void copyAttributes(Element* el, android::ResXMLParser* parser) {
	const size_t attrCount = parser->getAttributeCount();
	if (attrCount > 0) {
	el->attributes.reserve(attrCount);
	for (size_t i = 0; i < attrCount; i++) {
	Attribute attr;
	size_t len;
	const char16_t* str16 = parser->getAttributeNamespace(i, &len);
	if (str16) {
	attr.namespaceUri.assign(str16, len);
	}

	str16 = parser->getAttributeName(i, &len);
	if (str16) {
	attr.name.assign(str16, len);
	}

	str16 = parser->getAttributeStringValue(i, &len);
	if (str16) {
	attr.value.assign(str16, len);
	}
	el->attributes.push_back(std::move(attr));
	}
	}
	}

	std::unique_ptr<XmlResource> inflate(const void* data, size_t dataLen, IDiagnostics* diag,
	const Source& source) {
	// We import the android namespace because on Windows NO_ERROR is a macro, not an enum, which
	// causes errors when qualifying it with android::
	using namespace android;

	std::unique_ptr<Node> root;
	std::stack<Node*> nodeStack;

	ResXMLTree tree;
	if (tree.setTo(data, dataLen) != NO_ERROR) {
	return {};
	}

	ResXMLParser::event_code_t code;
	while ((code = tree.next()) != ResXMLParser::BAD_DOCUMENT &&
	code != ResXMLParser::END_DOCUMENT) {
	std::unique_ptr<Node> newNode;
	switch (code) {
	case ResXMLParser::START_NAMESPACE: {
	std::unique_ptr<Namespace> node = util::make_unique<Namespace>();
	size_t len;
	const char16_t* str16 = tree.getNamespacePrefix(&len);
	if (str16) {
	node->namespacePrefix.assign(str16, len);
	}

	str16 = tree.getNamespaceUri(&len);
	if (str16) {
	node->namespaceUri.assign(str16, len);
	}
	newNode = std::move(node);
	break;
	}

	case ResXMLParser::START_TAG: {
	std::unique_ptr<Element> node = util::make_unique<Element>();
	size_t len;
	const char16_t* str16 = tree.getElementNamespace(&len);
	if (str16) {
	node->namespaceUri.assign(str16, len);
	}

	str16 = tree.getElementName(&len);
	if (str16) {
	node->name.assign(str16, len);
	}

	copyAttributes(node.get(), &tree);

	newNode = std::move(node);
	break;
	}

	case ResXMLParser::TEXT: {
	std::unique_ptr<Text> node = util::make_unique<Text>();
	size_t len;
	const char16_t* str16 = tree.getText(&len);
	if (str16) {
	node->text.assign(str16, len);
	}
	newNode = std::move(node);
	break;
	}

	case ResXMLParser::END_NAMESPACE:
	case ResXMLParser::END_TAG:
	assert(!nodeStack.empty());
	nodeStack.pop();
	break;

	default:
	assert(false);
	break;
	}

	if (newNode) {
	newNode->lineNumber = tree.getLineNumber();

	Node* thisNode = newNode.get();
	if (!root) {
	assert(nodeStack.empty());
	root = std::move(newNode);
	} else {
	assert(!nodeStack.empty());
	nodeStack.top()->addChild(std::move(newNode));
	}

	if (!nodeCast<Text>(thisNode)) {
	nodeStack.push(thisNode);
	}
	}
	}
	return util::make_unique<XmlResource>(ResourceFile{}, std::move(root));
	}

	Element* findRootElement(XmlResource* doc) {
	return findRootElement(doc->root.get());
	}

	Element* findRootElement(Node* node) {
	if (!node) {
	return nullptr;
	}

	Element* el = nullptr;
	while ((el = nodeCast<Element>(node)) == nullptr) {
	if (node->children.empty()) {
	return nullptr;
	}
	// We are looking for the first element, and namespaces can only have one child.
	node = node->children.front().get();
	}
	return el;
	}

	void Node::addChild(std::unique_ptr<Node> child) {
	child->parent = this;
	children.push_back(std::move(child));
	}

	Attribute* Element::findAttribute(const StringPiece16& ns, const StringPiece16& name) {
	for (auto& attr : attributes) {
	if (ns == attr.namespaceUri && name == attr.name) {
	return &attr;
	}
	}
	return nullptr;
	}

	Element* Element::findChild(const StringPiece16& ns, const StringPiece16& name) {
	return findChildWithAttribute(ns, name, {}, {}, {});
	}

	Element* Element::findChildWithAttribute(const StringPiece16& ns, const StringPiece16& name,
	const StringPiece16& attrNs, const StringPiece16& attrName,
	const StringPiece16& attrValue) {
	for (auto& childNode : children) {
	Node* child = childNode.get();
	while (nodeCast<Namespace>(child)) {
	if (child->children.empty()) {
	break;
	}
	child = child->children[0].get();
	}

	if (Element* el = nodeCast<Element>(child)) {
	if (ns == el->namespaceUri && name == el->name) {
	if (attrNs.empty() && attrName.empty()) {
	return el;
	}

	Attribute* attr = el->findAttribute(attrNs, attrName);
	if (attr && attrValue == attr->value) {
	return el;
	}
	}
	}
	}
	return nullptr;
	}

	std::vector<Element*> Element::getChildElements() {
	std::vector<Element*> elements;
	for (auto& childNode : children) {
	Node* child = childNode.get();
	while (nodeCast<Namespace>(child)) {
	if (child->children.empty()) {
	break;
	}
	child = child->children[0].get();
	}

	if (Element* el = nodeCast<Element>(child)) {
	elements.push_back(el);
	}
	}
	return elements;
	}

	void PackageAwareVisitor::visit(Namespace* ns) {
	bool added = false;
	if (Maybe<ExtractedPackage> maybePackage = extractPackageFromNamespace(ns->namespaceUri)) {
	ExtractedPackage& package = maybePackage.value();
	mPackageDecls.push_back(PackageDecl{ ns->namespacePrefix, std::move(package) });
	added = true;
	}

	Visitor::visit(ns);

	if (added) {
	mPackageDecls.pop_back();
	}
	}

	Maybe<ExtractedPackage> PackageAwareVisitor::transformPackageAlias(
	const StringPiece16& alias, const StringPiece16& localPackage) const {
	if (alias.empty()) {
	return ExtractedPackage{ localPackage.toString(), false /* private */ };
	}

	const auto rend = mPackageDecls.rend();
	for (auto iter = mPackageDecls.rbegin(); iter != rend; ++iter) {
	if (alias == iter->prefix) {
	if (iter->package.package.empty()) {
	return ExtractedPackage{ localPackage.toString(),
	iter->package.privateNamespace };
	}
	return iter->package;
	}
	}
	return {};
	}

	} // namespace xml
	} // namespace aapt