wifi: hotspot2: omadm: add XML parser for parsing OMA-DM XML string

The XML parser will parse an XML string into a tree-like structure
represented by XMLNode, which will be used by an object specific parser
(e.g. PerProviderSubscription Management Object tree parser) for further
processing.

Bug: 32129686
Test: frameworks/base/wifi/tests/runtests.sh

Change-Id: I69c1931b2e8a6f3551e4eba5cffa3d2d0877872a

wifi/java/android/net/wifi/hotspot2/omadm/XMLNode.java

@@ -0,0 +1,103 @@
+/**
+ * Copyright (c) 2016, 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.
+ */
+
+package android.net.wifi.hotspot2.omadm;
+
+import android.text.TextUtils;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * A class represent a node in an XML tree. Each node is an XML element.
+ * Used by {@link XMLParser} for parsing/converting each XML element to XMLNode.
+ *
+ * @hide
+ */
+public class XMLNode {
+    private final String mTag;
+    private final List<XMLNode> mChildren;
+    private final XMLNode mParent;
+    private StringBuilder mTextBuilder;
+    private String mText;
+
+    public XMLNode(XMLNode parent, String tag) {
+        mTag = tag;
+        mParent = parent;
+        mChildren = new ArrayList<>();
+        mTextBuilder = new StringBuilder();
+        mText = null;
+    }
+
+    /**
+     * Adding a text to this node. Invoked by {@link XMLParser#characters}.
+     *
+     * @param text String to be added
+     */
+    public void addText(String text) {
+        mTextBuilder.append(text);
+    }
+
+    /**
+     * Adding a child node to this node. Invoked by {@link XMLParser#startElement}.
+     *
+     * @param child XMLNode to be added
+     */
+    public void addChild(XMLNode child) {
+        mChildren.add(child);
+    }
+
+    /**
+     * Invoked when the end of the XML element is detected. Used for further processing
+     * of the text enclosed within this XML element. Invoked by {@link XMLParser#endElement}.
+     */
+    public void close() {
+        // Remove the leading and the trailing whitespaces.
+        mText = mTextBuilder.toString().trim();
+        mTextBuilder = null;
+    }
+
+    public String getTag() {
+        return mTag;
+    }
+
+    public XMLNode getParent() {
+        return mParent;
+    }
+
+    public String getText() {
+        return mText;
+    }
+
+    public List<XMLNode> getChildren() {
+        return mChildren;
+    }
+
+    @Override
+    public boolean equals(Object thatObject) {
+        if (this == thatObject) {
+            return true;
+        }
+        if (!(thatObject instanceof XMLNode)) {
+            return false;
+        }
+        XMLNode that = (XMLNode) thatObject;
+
+        return TextUtils.equals(mTag, that.mTag) &&
+                TextUtils.equals(mText, that.mText) &&
+                mChildren.equals(that.mChildren);
+    }
+}

wifi/java/android/net/wifi/hotspot2/omadm/XMLParser.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+package android.net.wifi.hotspot2.omadm;
+
+import org.xml.sax.Attributes;
+import org.xml.sax.InputSource;
+import org.xml.sax.SAXException;
+import org.xml.sax.helpers.DefaultHandler;
+
+import android.text.TextUtils;
+
+import java.io.IOException;
+import java.io.StringReader;
+
+import javax.xml.parsers.ParserConfigurationException;
+import javax.xml.parsers.SAXParser;
+import javax.xml.parsers.SAXParserFactory;
+
+/**
+ * Class for parsing an XML string to an XML tree represented by {@link XMLNode}.
+ *
+ * The original XML string:
+ * <root>
+ *   <tag1>text1</tag1>
+ *   <tag2>
+ *     <tag3>text3</tag3>
+ *   </tag2>
+ * </root>
+ *
+ * The XML tree representation:
+ *                  [root]
+ *                     |
+ *                     |
+ *   [tag1, text1]-----|-----[tag2]
+ *                             |
+ *                             |
+ *                       [tag3, text3]
+ *
+ * @hide
+ */
+public class XMLParser extends DefaultHandler {
+    private XMLNode mRoot = null;
+    private XMLNode mCurrent = null;
+
+    public XMLNode parse(String text) throws IOException, SAXException {
+        if (TextUtils.isEmpty(text)) {
+            throw new IOException("XML string not provided");
+        }
+
+        // Reset pointers.
+        mRoot = null;
+        mCurrent = null;
+
+        try {
+            SAXParser parser = SAXParserFactory.newInstance().newSAXParser();
+            parser.parse(new InputSource(new StringReader(text)), this);
+            return mRoot;
+        } catch (ParserConfigurationException pce) {
+            throw new SAXException(pce);
+        }
+    }
+
+    @Override
+    public void startElement(String uri, String localName, String qName, Attributes attributes)
+            throws SAXException {
+        XMLNode parent = mCurrent;
+
+        mCurrent = new XMLNode(parent, qName);
+
+        if (mRoot == null) {
+            mRoot = mCurrent;
+        } else if (parent == null) {
+            throw new SAXException("More than one root nodes");
+        } else {
+            parent.addChild(mCurrent);
+        }
+    }
+
+    @Override
+    public void endElement(String uri, String localName, String qName) throws SAXException {
+        if (!qName.equals(mCurrent.getTag())) {
+            throw new SAXException("End tag '" + qName + "' doesn't match current node: " +
+                    mCurrent);
+        }
+
+        mCurrent.close();
+        mCurrent = mCurrent.getParent();
+    }
+
+    @Override
+    public void characters(char[] ch, int start, int length) throws SAXException {
+        mCurrent.addText(new String(ch, start, length));
+    }
+}

wifi/tests/src/android/net/wifi/hotspot2/omadm/XMLParserTest.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+package android.net.wifi.hotspot2.omadm;
+
+import static org.junit.Assert.assertTrue;
+
+import android.net.wifi.hotspot2.omadm.XMLNode;
+import android.net.wifi.hotspot2.omadm.XMLParser;
+import android.test.suitebuilder.annotation.SmallTest;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.xml.sax.SAXException;
+
+import java.io.IOException;
+
+/**
+ * Unit tests for {@link android.net.wifi.hotspot2.omadm.XMLParser}.
+ */
+@SmallTest
+public class XMLParserTest {
+    XMLParser mParser;
+
+    private static XMLNode createNode(XMLNode parent, String tag, String text) {
+        XMLNode node = new XMLNode(parent, tag);
+        node.addText(text);
+        if (parent != null)
+            parent.addChild(node);
+        node.close();
+        return node;
+    }
+
+    /**
+     * Setup before tests.
+     */
+    @Before
+    public void setUp() throws Exception {
+        mParser = new XMLParser();
+    }
+
+    @Test(expected = IOException.class)
+    public void parseNullXML() throws Exception {
+        mParser.parse(null);
+    }
+
+    @Test(expected = IOException.class)
+    public void parseEmptyXML() throws Exception {
+        mParser.parse(new String());
+    }
+
+    @Test(expected = SAXException.class)
+    public void parseMalformedXML() throws Exception {
+        String malformedXmlTree = "<root><child1>test1</child2></root>";
+        mParser.parse(malformedXmlTree);
+    }
+
+    @Test
+    public void parseValidXMLTree() throws Exception {
+        String xmlTree = "<root><child1>test1</child1><child2>test2</child2></root>";
+
+        // Construct the expected XML tree.
+        XMLNode expectedRoot = createNode(null, "root", "");
+        createNode(expectedRoot, "child1", "test1");
+        createNode(expectedRoot, "child2", "test2");
+
+        XMLNode actualRoot = mParser.parse(xmlTree);
+        assertTrue(actualRoot.equals(expectedRoot));
+    }
+}