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.cpp b/tools/aapt2/xml/XmlPullParser.cpp
new file mode 100644
index 0000000..323ec05
--- /dev/null
+++ b/tools/aapt2/xml/XmlPullParser.cpp
@@ -0,0 +1,308 @@
+/*
+ * 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 "util/Maybe.h"
+#include "util/Util.h"
+#include "xml/XmlPullParser.h"
+#include "xml/XmlUtil.h"
+
+#include <iostream>
+#include <string>
+
+namespace aapt {
+namespace xml {
+
+constexpr char kXmlNamespaceSep = 1;
+
+XmlPullParser::XmlPullParser(std::istream& in) : mIn(in), mEmpty(), mDepth(0) {
+    mParser = XML_ParserCreateNS(nullptr, kXmlNamespaceSep);
+    XML_SetUserData(mParser, this);
+    XML_SetElementHandler(mParser, startElementHandler, endElementHandler);
+    XML_SetNamespaceDeclHandler(mParser, startNamespaceHandler, endNamespaceHandler);
+    XML_SetCharacterDataHandler(mParser, characterDataHandler);
+    XML_SetCommentHandler(mParser, commentDataHandler);
+    mEventQueue.push(EventData{ Event::kStartDocument, 0, mDepth++ });
+}
+
+XmlPullParser::~XmlPullParser() {
+    XML_ParserFree(mParser);
+}
+
+XmlPullParser::Event XmlPullParser::next() {
+    const Event currentEvent = getEvent();
+    if (currentEvent == Event::kBadDocument || currentEvent == Event::kEndDocument) {
+        return currentEvent;
+    }
+
+    mEventQueue.pop();
+    while (mEventQueue.empty()) {
+        mIn.read(mBuffer, sizeof(mBuffer) / sizeof(*mBuffer));
+
+        const bool done = mIn.eof();
+        if (mIn.bad() && !done) {
+            mLastError = strerror(errno);
+            mEventQueue.push(EventData{ Event::kBadDocument });
+            continue;
+        }
+
+        if (XML_Parse(mParser, mBuffer, mIn.gcount(), done) == XML_STATUS_ERROR) {
+            mLastError = XML_ErrorString(XML_GetErrorCode(mParser));
+            mEventQueue.push(EventData{ Event::kBadDocument });
+            continue;
+        }
+
+        if (done) {
+            mEventQueue.push(EventData{ Event::kEndDocument, 0, 0 });
+        }
+    }
+
+    Event event = getEvent();
+
+    // Record namespace prefixes and package names so that we can do our own
+    // handling of references that use namespace aliases.
+    if (event == Event::kStartNamespace || event == Event::kEndNamespace) {
+        Maybe<ExtractedPackage> result = extractPackageFromNamespace(getNamespaceUri());
+        if (event == Event::kStartNamespace) {
+            if (result) {
+                mPackageAliases.emplace_back(
+                        PackageDecl{ getNamespacePrefix(), std::move(result.value()) });
+            }
+        } else {
+            if (result) {
+                mPackageAliases.pop_back();
+            }
+        }
+    }
+
+    return event;
+}
+
+XmlPullParser::Event XmlPullParser::getEvent() const {
+    return mEventQueue.front().event;
+}
+
+const std::string& XmlPullParser::getLastError() const {
+    return mLastError;
+}
+
+const std::u16string& XmlPullParser::getComment() const {
+    return mEventQueue.front().data1;
+}
+
+size_t XmlPullParser::getLineNumber() const {
+    return mEventQueue.front().lineNumber;
+}
+
+size_t XmlPullParser::getDepth() const {
+    return mEventQueue.front().depth;
+}
+
+const std::u16string& XmlPullParser::getText() const {
+    if (getEvent() != Event::kText) {
+        return mEmpty;
+    }
+    return mEventQueue.front().data1;
+}
+
+const std::u16string& XmlPullParser::getNamespacePrefix() const {
+    const Event currentEvent = getEvent();
+    if (currentEvent != Event::kStartNamespace && currentEvent != Event::kEndNamespace) {
+        return mEmpty;
+    }
+    return mEventQueue.front().data1;
+}
+
+const std::u16string& XmlPullParser::getNamespaceUri() const {
+    const Event currentEvent = getEvent();
+    if (currentEvent != Event::kStartNamespace && currentEvent != Event::kEndNamespace) {
+        return mEmpty;
+    }
+    return mEventQueue.front().data2;
+}
+
+Maybe<ExtractedPackage> XmlPullParser::transformPackageAlias(
+        const StringPiece16& alias, const StringPiece16& localPackage) const {
+    if (alias.empty()) {
+        return ExtractedPackage{ localPackage.toString(), false /* private */ };
+    }
+
+    const auto endIter = mPackageAliases.rend();
+    for (auto iter = mPackageAliases.rbegin(); iter != endIter; ++iter) {
+        if (alias == iter->prefix) {
+            if (iter->package.package.empty()) {
+                return ExtractedPackage{ localPackage.toString(),
+                                         iter->package.privateNamespace };
+            }
+            return iter->package;
+        }
+    }
+    return {};
+}
+
+const std::u16string& XmlPullParser::getElementNamespace() const {
+    const Event currentEvent = getEvent();
+    if (currentEvent != Event::kStartElement && currentEvent != Event::kEndElement) {
+        return mEmpty;
+    }
+    return mEventQueue.front().data1;
+}
+
+const std::u16string& XmlPullParser::getElementName() const {
+    const Event currentEvent = getEvent();
+    if (currentEvent != Event::kStartElement && currentEvent != Event::kEndElement) {
+        return mEmpty;
+    }
+    return mEventQueue.front().data2;
+}
+
+XmlPullParser::const_iterator XmlPullParser::beginAttributes() const {
+    return mEventQueue.front().attributes.begin();
+}
+
+XmlPullParser::const_iterator XmlPullParser::endAttributes() const {
+    return mEventQueue.front().attributes.end();
+}
+
+size_t XmlPullParser::getAttributeCount() const {
+    if (getEvent() != Event::kStartElement) {
+        return 0;
+    }
+    return mEventQueue.front().attributes.size();
+}
+
+/**
+ * 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 = std::u16string();
+        outName = util::utf8ToUtf16(name);
+    } else {
+        outNs = util::utf8ToUtf16(StringPiece(name, (p - name)));
+        outName = util::utf8ToUtf16(p + 1);
+    }
+}
+
+void XMLCALL XmlPullParser::startNamespaceHandler(void* userData, const char* prefix,
+        const char* uri) {
+    XmlPullParser* parser = reinterpret_cast<XmlPullParser*>(userData);
+    std::u16string namespaceUri = uri != nullptr ? util::utf8ToUtf16(uri) : std::u16string();
+    parser->mNamespaceUris.push(namespaceUri);
+    parser->mEventQueue.push(EventData{
+            Event::kStartNamespace,
+            XML_GetCurrentLineNumber(parser->mParser),
+            parser->mDepth++,
+            prefix != nullptr ? util::utf8ToUtf16(prefix) : std::u16string(),
+            namespaceUri
+    });
+}
+
+void XMLCALL XmlPullParser::startElementHandler(void* userData, const char* name,
+        const char** attrs) {
+    XmlPullParser* parser = reinterpret_cast<XmlPullParser*>(userData);
+
+    EventData data = {
+            Event::kStartElement, XML_GetCurrentLineNumber(parser->mParser), parser->mDepth++
+    };
+    splitName(name, data.data1, data.data2);
+
+    while (*attrs) {
+        Attribute attribute;
+        splitName(*attrs++, attribute.namespaceUri, attribute.name);
+        attribute.value = util::utf8ToUtf16(*attrs++);
+
+        // Insert in sorted order.
+        auto iter = std::lower_bound(data.attributes.begin(), data.attributes.end(), attribute);
+        data.attributes.insert(iter, std::move(attribute));
+    }
+
+    // Move the structure into the queue (no copy).
+    parser->mEventQueue.push(std::move(data));
+}
+
+void XMLCALL XmlPullParser::characterDataHandler(void* userData, const char* s, int len) {
+    XmlPullParser* parser = reinterpret_cast<XmlPullParser*>(userData);
+
+    parser->mEventQueue.push(EventData{
+            Event::kText,
+            XML_GetCurrentLineNumber(parser->mParser),
+            parser->mDepth,
+            util::utf8ToUtf16(StringPiece(s, len))
+    });
+}
+
+void XMLCALL XmlPullParser::endElementHandler(void* userData, const char* name) {
+    XmlPullParser* parser = reinterpret_cast<XmlPullParser*>(userData);
+
+    EventData data = {
+            Event::kEndElement, XML_GetCurrentLineNumber(parser->mParser), --(parser->mDepth)
+    };
+    splitName(name, data.data1, data.data2);
+
+    // Move the data into the queue (no copy).
+    parser->mEventQueue.push(std::move(data));
+}
+
+void XMLCALL XmlPullParser::endNamespaceHandler(void* userData, const char* prefix) {
+    XmlPullParser* parser = reinterpret_cast<XmlPullParser*>(userData);
+
+    parser->mEventQueue.push(EventData{
+            Event::kEndNamespace,
+            XML_GetCurrentLineNumber(parser->mParser),
+            --(parser->mDepth),
+            prefix != nullptr ? util::utf8ToUtf16(prefix) : std::u16string(),
+            parser->mNamespaceUris.top()
+    });
+    parser->mNamespaceUris.pop();
+}
+
+void XMLCALL XmlPullParser::commentDataHandler(void* userData, const char* comment) {
+    XmlPullParser* parser = reinterpret_cast<XmlPullParser*>(userData);
+
+    parser->mEventQueue.push(EventData{
+            Event::kComment,
+            XML_GetCurrentLineNumber(parser->mParser),
+            parser->mDepth,
+            util::utf8ToUtf16(comment)
+    });
+}
+
+Maybe<StringPiece16> findAttribute(const XmlPullParser* parser, const StringPiece16& name) {
+    auto iter = parser->findAttribute(u"", name);
+    if (iter != parser->endAttributes()) {
+        return StringPiece16(util::trimWhitespace(iter->value));
+    }
+    return {};
+}
+
+Maybe<StringPiece16> findNonEmptyAttribute(const XmlPullParser* parser, const StringPiece16& name) {
+    auto iter = parser->findAttribute(u"", name);
+    if (iter != parser->endAttributes()) {
+        StringPiece16 trimmed = util::trimWhitespace(iter->value);
+        if (!trimmed.empty()) {
+            return trimmed;
+        }
+    }
+    return {};
+}
+
+} // namespace xml
+} // namespace aapt