AAPT2: Fail compiling when private symbols are referenced

Also moved some XML specific stuff into its own directory,
and refactored ReferenceLinker a bit.

Change-Id: I912247a82023c1bbf72dc191fbdaf62858cbec0c
diff --git a/tools/aapt2/xml/XmlPullParser.h b/tools/aapt2/xml/XmlPullParser.h
new file mode 100644
index 0000000..7e7070e
--- /dev/null
+++ b/tools/aapt2/xml/XmlPullParser.h
@@ -0,0 +1,298 @@
+/*
+ * 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.
+ */
+
+#ifndef AAPT_XML_PULL_PARSER_H
+#define AAPT_XML_PULL_PARSER_H
+
+#include "Resource.h"
+#include "process/IResourceTableConsumer.h"
+#include "util/Maybe.h"
+#include "util/StringPiece.h"
+#include "xml/XmlUtil.h"
+
+#include <algorithm>
+#include <expat.h>
+#include <istream>
+#include <ostream>
+#include <queue>
+#include <stack>
+#include <string>
+#include <vector>
+
+namespace aapt {
+namespace xml {
+
+class XmlPullParser : public IPackageDeclStack {
+public:
+    enum class Event {
+        kBadDocument,
+        kStartDocument,
+        kEndDocument,
+
+        kStartNamespace,
+        kEndNamespace,
+        kStartElement,
+        kEndElement,
+        kText,
+        kComment,
+    };
+
+    /**
+     * Skips to the next direct descendant node of the given startDepth,
+     * skipping namespace nodes.
+     *
+     * When nextChildNode returns true, you can expect Comments, Text, and StartElement events.
+     */
+    static bool nextChildNode(XmlPullParser* parser, size_t startDepth);
+    static bool skipCurrentElement(XmlPullParser* parser);
+    static bool isGoodEvent(Event event);
+
+    XmlPullParser(std::istream& in);
+    ~XmlPullParser();
+
+    /**
+     * Returns the current event that is being processed.
+     */
+    Event getEvent() const;
+
+    const std::string& getLastError() const;
+
+    /**
+     * Note, unlike XmlPullParser, the first call to next() will return
+     * StartElement of the first element.
+     */
+    Event next();
+
+    //
+    // These are available for all nodes.
+    //
+
+    const std::u16string& getComment() const;
+    size_t getLineNumber() const;
+    size_t getDepth() const;
+
+    /**
+     * Returns the character data for a Text event.
+     */
+    const std::u16string& getText() const;
+
+    //
+    // Namespace prefix and URI are available for StartNamespace and EndNamespace.
+    //
+
+    const std::u16string& getNamespacePrefix() const;
+    const std::u16string& getNamespaceUri() const;
+
+    //
+    // These are available for StartElement and EndElement.
+    //
+
+    const std::u16string& getElementNamespace() const;
+    const std::u16string& getElementName() const;
+
+    /*
+     * Uses the current stack of namespaces to resolve the package. Eg:
+     * xmlns:app = "http://schemas.android.com/apk/res/com.android.app"
+     * ...
+     * android:text="@app:string/message"
+     *
+     * In this case, 'app' will be converted to 'com.android.app'.
+     *
+     * If xmlns:app="http://schemas.android.com/apk/res-auto", then
+     * 'package' will be set to 'defaultPackage'.
+     */
+    Maybe<ExtractedPackage> transformPackageAlias(
+            const StringPiece16& alias, const StringPiece16& localPackage) const override;
+
+    //
+    // Remaining methods are for retrieving information about attributes
+    // associated with a StartElement.
+    //
+    // Attributes must be in sorted order (according to the less than operator
+    // of struct Attribute).
+    //
+
+    struct Attribute {
+        std::u16string namespaceUri;
+        std::u16string name;
+        std::u16string value;
+
+        int compare(const Attribute& rhs) const;
+        bool operator<(const Attribute& rhs) const;
+        bool operator==(const Attribute& rhs) const;
+        bool operator!=(const Attribute& rhs) const;
+    };
+
+    using const_iterator = std::vector<Attribute>::const_iterator;
+
+    const_iterator beginAttributes() const;
+    const_iterator endAttributes() const;
+    size_t getAttributeCount() const;
+    const_iterator findAttribute(StringPiece16 namespaceUri, StringPiece16 name) const;
+
+private:
+    static void XMLCALL startNamespaceHandler(void* userData, const char* prefix, const char* uri);
+    static void XMLCALL startElementHandler(void* userData, const char* name, const char** attrs);
+    static void XMLCALL characterDataHandler(void* userData, const char* s, int len);
+    static void XMLCALL endElementHandler(void* userData, const char* name);
+    static void XMLCALL endNamespaceHandler(void* userData, const char* prefix);
+    static void XMLCALL commentDataHandler(void* userData, const char* comment);
+
+    struct EventData {
+        Event event;
+        size_t lineNumber;
+        size_t depth;
+        std::u16string data1;
+        std::u16string data2;
+        std::vector<Attribute> attributes;
+    };
+
+    std::istream& mIn;
+    XML_Parser mParser;
+    char mBuffer[16384];
+    std::queue<EventData> mEventQueue;
+    std::string mLastError;
+    const std::u16string mEmpty;
+    size_t mDepth;
+    std::stack<std::u16string> mNamespaceUris;
+
+    struct PackageDecl {
+        std::u16string prefix;
+        ExtractedPackage package;
+    };
+    std::vector<PackageDecl> mPackageAliases;
+};
+
+/**
+ * Finds the attribute in the current element within the global namespace.
+ */
+Maybe<StringPiece16> findAttribute(const XmlPullParser* parser, const StringPiece16& name);
+
+/**
+ * Finds the attribute in the current element within the global namespace. The attribute's value
+ * must not be the empty string.
+ */
+Maybe<StringPiece16> findNonEmptyAttribute(const XmlPullParser* parser, const StringPiece16& name);
+
+//
+// Implementation
+//
+
+inline ::std::ostream& operator<<(::std::ostream& out, XmlPullParser::Event event) {
+    switch (event) {
+        case XmlPullParser::Event::kBadDocument: return out << "BadDocument";
+        case XmlPullParser::Event::kStartDocument: return out << "StartDocument";
+        case XmlPullParser::Event::kEndDocument: return out << "EndDocument";
+        case XmlPullParser::Event::kStartNamespace: return out << "StartNamespace";
+        case XmlPullParser::Event::kEndNamespace: return out << "EndNamespace";
+        case XmlPullParser::Event::kStartElement: return out << "StartElement";
+        case XmlPullParser::Event::kEndElement: return out << "EndElement";
+        case XmlPullParser::Event::kText: return out << "Text";
+        case XmlPullParser::Event::kComment: return out << "Comment";
+    }
+    return out;
+}
+
+inline bool XmlPullParser::nextChildNode(XmlPullParser* parser, size_t startDepth) {
+    Event event;
+
+    // First get back to the start depth.
+    while (isGoodEvent(event = parser->next()) && parser->getDepth() > startDepth + 1) {}
+
+    // Now look for the first good node.
+    while ((event != Event::kEndElement || parser->getDepth() > startDepth) && isGoodEvent(event)) {
+        switch (event) {
+        case Event::kText:
+        case Event::kComment:
+        case Event::kStartElement:
+            return true;
+        default:
+            break;
+        }
+        event = parser->next();
+    }
+    return false;
+}
+
+inline bool XmlPullParser::skipCurrentElement(XmlPullParser* parser) {
+    int depth = 1;
+    while (depth > 0) {
+        switch (parser->next()) {
+            case Event::kEndDocument:
+                return true;
+            case Event::kBadDocument:
+                return false;
+            case Event::kStartElement:
+                depth++;
+                break;
+            case Event::kEndElement:
+                depth--;
+                break;
+            default:
+                break;
+        }
+    }
+    return true;
+}
+
+inline bool XmlPullParser::isGoodEvent(XmlPullParser::Event event) {
+    return event != Event::kBadDocument && event != Event::kEndDocument;
+}
+
+inline int XmlPullParser::Attribute::compare(const Attribute& rhs) const {
+    int cmp = namespaceUri.compare(rhs.namespaceUri);
+    if (cmp != 0) return cmp;
+    return name.compare(rhs.name);
+}
+
+inline bool XmlPullParser::Attribute::operator<(const Attribute& rhs) const {
+    return compare(rhs) < 0;
+}
+
+inline bool XmlPullParser::Attribute::operator==(const Attribute& rhs) const {
+    return compare(rhs) == 0;
+}
+
+inline bool XmlPullParser::Attribute::operator!=(const Attribute& rhs) const {
+    return compare(rhs) != 0;
+}
+
+inline XmlPullParser::const_iterator XmlPullParser::findAttribute(StringPiece16 namespaceUri,
+                                                                  StringPiece16 name) const {
+    const auto endIter = endAttributes();
+    const auto iter = std::lower_bound(beginAttributes(), endIter,
+            std::pair<StringPiece16, StringPiece16>(namespaceUri, name),
+            [](const Attribute& attr, const std::pair<StringPiece16, StringPiece16>& rhs) -> bool {
+                int cmp = attr.namespaceUri.compare(0, attr.namespaceUri.size(),
+                        rhs.first.data(), rhs.first.size());
+                if (cmp < 0) return true;
+                if (cmp > 0) return false;
+                cmp = attr.name.compare(0, attr.name.size(), rhs.second.data(), rhs.second.size());
+                if (cmp < 0) return true;
+                return false;
+            }
+    );
+
+    if (iter != endIter && namespaceUri == iter->namespaceUri && name == iter->name) {
+        return iter;
+    }
+    return endIter;
+}
+
+} // namespace xml
+} // namespace aapt
+
+#endif // AAPT_XML_PULL_PARSER_H