services/core/java/com/android/server/pm/SettingsXml.java - platform/frameworks/base - Git at Google

 /*
  * Copyright (C) 2020 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 com.android.server.pm;

 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.util.Slog;
 import android.util.Xml;

 import com.android.modules.utils.TypedXmlPullParser;
 import com.android.modules.utils.TypedXmlSerializer;

 import org.xmlpull.v1.XmlPullParser;
 import org.xmlpull.v1.XmlPullParserException;

 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.charset.StandardCharsets;
 import java.util.Stack;

 /**
  * A very specialized serialization/parsing wrapper around {@link TypedXmlSerializer} and {@link
  * TypedXmlPullParser} intended for use with PackageManager related settings files.
  * Assumptions/chosen behaviors:
  * <ul>
  *     <li>No namespace support</li>
  *     <li>Data for a parent object is stored as attributes</li>
  *     <li>All attribute read methods return a default false, -1, or null</li>
  *     <li>Default values will not be written</li>
  *     <li>Children are sub-elements</li>
  *     <li>Collections are repeated sub-elements, no attribute support for collections</li>
  * </ul>
  */
 public class SettingsXml {

     private static final String TAG = "SettingsXml";

     private static final boolean DEBUG_THROW_EXCEPTIONS = false;

     private static final String FEATURE_INDENT =
             "http://xmlpull.org/v1/doc/features.html#indent-output";

     private static final int DEFAULT_NUMBER = -1;

     public static Serializer serializer(TypedXmlSerializer serializer) {
         return new Serializer(serializer);
     }

     public static ReadSection parser(TypedXmlPullParser parser)
             throws IOException, XmlPullParserException {
         return new ReadSectionImpl(parser);
     }

     public static class Serializer implements AutoCloseable {

         @NonNull
         private final TypedXmlSerializer mXmlSerializer;

         private final WriteSectionImpl mWriteSection;

         private Serializer(TypedXmlSerializer serializer) {
             mXmlSerializer = serializer;
             mWriteSection = new WriteSectionImpl(mXmlSerializer);
         }

         public WriteSection startSection(@NonNull String sectionName) throws IOException {
             return mWriteSection.startSection(sectionName);
         }

         @Override
         public void close() throws IOException {
             mWriteSection.closeCompletely();
             mXmlSerializer.flush();
         }
     }

     public interface ReadSection extends AutoCloseable {

         @NonNull
         String getName();

         @NonNull
         String getDescription();

         boolean has(String attrName);

         @Nullable
         String getString(String attrName);

         /**
          * @return value as String or {@param defaultValue} if doesn't exist
          */
         @NonNull
         String getString(String attrName, @NonNull String defaultValue);

         /**
          * @return value as boolean or false if doesn't exist
          */
         boolean getBoolean(String attrName);

         /**
          * @return value as boolean or {@param defaultValue} if doesn't exist
          */
         boolean getBoolean(String attrName, boolean defaultValue);

         /**
          * @return value as int or {@link #DEFAULT_NUMBER} if doesn't exist
          */
         int getInt(String attrName);

         /**
          * @return value as int or {@param defaultValue} if doesn't exist
          */
         int getInt(String attrName, int defaultValue);

         /**
          * @return value as long or {@link #DEFAULT_NUMBER} if doesn't exist
          */
         long getLong(String attrName);

         /**
          * @return value as long or {@param defaultValue} if doesn't exist
          */
         long getLong(String attrName, int defaultValue);

         ChildSection children();
     }

     /**
      * <pre><code>
      * ChildSection child = parentSection.children();
      * while (child.moveToNext(TAG_CHILD)) {
      *     String readValue = child.getString(...);
      *     ...
      * }
      * </code></pre>
      */
     public interface ChildSection extends ReadSection {
         boolean moveToNext();

         boolean moveToNext(@NonNull String expectedChildTagName);
     }

     public static class ReadSectionImpl implements ChildSection {

         @Nullable
         private final InputStream mInput;

         @NonNull
         private final TypedXmlPullParser mParser;

         @NonNull
         private final Stack<Integer> mDepthStack = new Stack<>();

         public ReadSectionImpl(@NonNull InputStream input)
                 throws IOException, XmlPullParserException {
             mInput = input;
             mParser = Xml.newFastPullParser();
             mParser.setInput(mInput, StandardCharsets.UTF_8.name());
             moveToFirstTag();
         }

         public ReadSectionImpl(@NonNull TypedXmlPullParser parser)
                 throws IOException, XmlPullParserException {
             mInput = null;
             mParser = parser;
             moveToFirstTag();
         }

         private void moveToFirstTag() throws IOException, XmlPullParserException {
             if (mParser.getEventType() == XmlPullParser.START_TAG) {
                 return;
             }

             int type;
             //noinspection StatementWithEmptyBody
             while ((type = mParser.next()) != XmlPullParser.START_TAG
                     && type != XmlPullParser.END_DOCUMENT) {
             }
         }

         @NonNull
         @Override
         public String getName() {
             return mParser.getName();
         }

         @NonNull
         @Override
         public String getDescription() {
             return mParser.getPositionDescription();
         }

         @Override
         public boolean has(String attrName) {
             return mParser.getAttributeValue(null, attrName) != null;
         }

         @Nullable
         @Override
         public String getString(String attrName) {
             return mParser.getAttributeValue(null, attrName);
         }

         @NonNull
         @Override
         public String getString(String attrName, @NonNull String defaultValue) {
             String value = mParser.getAttributeValue(null, attrName);
             if (value == null) {
                 return defaultValue;
             }
             return value;
         }

         @Override
         public boolean getBoolean(String attrName) {
             return getBoolean(attrName, false);
         }

         @Override
         public boolean getBoolean(String attrName, boolean defaultValue) {
             return mParser.getAttributeBoolean(null, attrName, defaultValue);
         }

         @Override
         public int getInt(String attrName) {
             return getInt(attrName, DEFAULT_NUMBER);
         }

         @Override
         public int getInt(String attrName, int defaultValue) {
             return mParser.getAttributeInt(null, attrName, defaultValue);
         }

         @Override
         public long getLong(String attrName) {
             return getLong(attrName, DEFAULT_NUMBER);
         }

         @Override
         public long getLong(String attrName, int defaultValue) {
             return mParser.getAttributeLong(null, attrName, defaultValue);
         }

         @Override
         public ChildSection children() {
             mDepthStack.push(mParser.getDepth());
             return this;
         }

         @Override
         public boolean moveToNext() {
             return moveToNextInternal(null);
         }

         @Override
         public boolean moveToNext(@NonNull String expectedChildTagName) {
             return moveToNextInternal(expectedChildTagName);
         }

         private boolean moveToNextInternal(@Nullable String expectedChildTagName) {
             try {
                 int depth = mDepthStack.peek();
                 boolean hasTag = false;
                 int type;
                 while (!hasTag
                         && (type = mParser.next()) != XmlPullParser.END_DOCUMENT
                         && (type != XmlPullParser.END_TAG || mParser.getDepth() > depth)) {
                     if (type != XmlPullParser.START_TAG) {
                         continue;
                     }

                     if (expectedChildTagName != null
                             && !expectedChildTagName.equals(mParser.getName())) {
                         continue;
                     }

                     hasTag = true;
                 }

                 if (!hasTag) {
                     mDepthStack.pop();
                 }

                 return hasTag;
             } catch (Exception ignored) {
                 return false;
             }
         }

         @Override
         public void close() throws Exception {
             if (mDepthStack.isEmpty()) {
                 Slog.wtf(TAG, "Children depth stack was not empty, data may have been lost",
                         new Exception());
             }
             if (mInput != null) {
                 mInput.close();
             }
         }
     }

     public interface WriteSection extends AutoCloseable {

         WriteSection startSection(@NonNull String sectionName) throws IOException;

         WriteSection attribute(String attrName, @Nullable String value) throws IOException;

         WriteSection attribute(String attrName, int value) throws IOException;

         WriteSection attribute(String attrName, long value) throws IOException;

         WriteSection attribute(String attrName, boolean value) throws IOException;

         @Override
         void close() throws IOException;

         void finish() throws IOException;
     }

     private static class WriteSectionImpl implements WriteSection {

         @NonNull
         private final TypedXmlSerializer mXmlSerializer;

         @NonNull
         private final Stack<String> mTagStack = new Stack<>();

         private WriteSectionImpl(@NonNull TypedXmlSerializer xmlSerializer) {
             mXmlSerializer = xmlSerializer;
         }

         @Override
         public WriteSection startSection(@NonNull String sectionName) throws IOException {
             // Try to start the tag first before we push it to the stack
             mXmlSerializer.startTag(null, sectionName);
             mTagStack.push(sectionName);
             return this;
         }

         @Override
         public WriteSection attribute(String attrName, String value) throws IOException {
             if (value != null) {
                 mXmlSerializer.attribute(null, attrName, value);
             }
             return this;
         }

         @Override
         public WriteSection attribute(String attrName, int value) throws IOException {
             if (value != DEFAULT_NUMBER) {
                 mXmlSerializer.attributeInt(null, attrName, value);
             }
             return this;
         }

         @Override
         public WriteSection attribute(String attrName, long value) throws IOException {
             if (value != DEFAULT_NUMBER) {
                 mXmlSerializer.attributeLong(null, attrName, value);
             }
             return this;
         }

         @Override
         public WriteSection attribute(String attrName, boolean value) throws IOException {
             if (value) {
                 mXmlSerializer.attributeBoolean(null, attrName, value);
             }
             return this;
         }

         @Override
         public void finish() throws IOException {
             close();
         }

         @Override
         public void close() throws IOException {
             mXmlSerializer.endTag(null, mTagStack.pop());
         }

         private void closeCompletely() throws IOException {
             if (DEBUG_THROW_EXCEPTIONS && mTagStack != null && !mTagStack.isEmpty()) {
                 throw new IllegalStateException(
                         "tag stack is not empty when closing, contains " + mTagStack);
             } else if (mTagStack != null) {
                 while (!mTagStack.isEmpty()) {
                     close();
                 }
             }
         }
     }
 }
	/*
	* Copyright (C) 2020 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 com.android.server.pm;

	import android.annotation.NonNull;
	import android.annotation.Nullable;
	import android.util.Slog;
	import android.util.Xml;

	import com.android.modules.utils.TypedXmlPullParser;
	import com.android.modules.utils.TypedXmlSerializer;

	import org.xmlpull.v1.XmlPullParser;
	import org.xmlpull.v1.XmlPullParserException;

	import java.io.IOException;
	import java.io.InputStream;
	import java.nio.charset.StandardCharsets;
	import java.util.Stack;

	/**
	* A very specialized serialization/parsing wrapper around {@link TypedXmlSerializer} and {@link
	* TypedXmlPullParser} intended for use with PackageManager related settings files.
	* Assumptions/chosen behaviors:
	* <ul>
	* <li>No namespace support</li>
	* <li>Data for a parent object is stored as attributes</li>
	* <li>All attribute read methods return a default false, -1, or null</li>
	* <li>Default values will not be written</li>
	* <li>Children are sub-elements</li>
	* <li>Collections are repeated sub-elements, no attribute support for collections</li>
	* </ul>
	*/
	public class SettingsXml {

	private static final String TAG = "SettingsXml";

	private static final boolean DEBUG_THROW_EXCEPTIONS = false;

	private static final String FEATURE_INDENT =
	"http://xmlpull.org/v1/doc/features.html#indent-output";

	private static final int DEFAULT_NUMBER = -1;

	public static Serializer serializer(TypedXmlSerializer serializer) {
	return new Serializer(serializer);
	}

	public static ReadSection parser(TypedXmlPullParser parser)
	throws IOException, XmlPullParserException {
	return new ReadSectionImpl(parser);
	}

	public static class Serializer implements AutoCloseable {

	@NonNull
	private final TypedXmlSerializer mXmlSerializer;

	private final WriteSectionImpl mWriteSection;

	private Serializer(TypedXmlSerializer serializer) {
	mXmlSerializer = serializer;
	mWriteSection = new WriteSectionImpl(mXmlSerializer);
	}

	public WriteSection startSection(@NonNull String sectionName) throws IOException {
	return mWriteSection.startSection(sectionName);
	}

	@Override
	public void close() throws IOException {
	mWriteSection.closeCompletely();
	mXmlSerializer.flush();
	}
	}

	public interface ReadSection extends AutoCloseable {

	@NonNull
	String getName();

	@NonNull
	String getDescription();

	boolean has(String attrName);

	@Nullable
	String getString(String attrName);

	/**
	* @return value as String or {@param defaultValue} if doesn't exist
	*/
	@NonNull
	String getString(String attrName, @NonNull String defaultValue);

	/**
	* @return value as boolean or false if doesn't exist
	*/
	boolean getBoolean(String attrName);

	/**
	* @return value as boolean or {@param defaultValue} if doesn't exist
	*/
	boolean getBoolean(String attrName, boolean defaultValue);

	/**
	* @return value as int or {@link #DEFAULT_NUMBER} if doesn't exist
	*/
	int getInt(String attrName);

	/**
	* @return value as int or {@param defaultValue} if doesn't exist
	*/
	int getInt(String attrName, int defaultValue);

	/**
	* @return value as long or {@link #DEFAULT_NUMBER} if doesn't exist
	*/
	long getLong(String attrName);

	/**
	* @return value as long or {@param defaultValue} if doesn't exist
	*/
	long getLong(String attrName, int defaultValue);

	ChildSection children();
	}

	/**
	* <pre><code>
	* ChildSection child = parentSection.children();
	* while (child.moveToNext(TAG_CHILD)) {
	* String readValue = child.getString(...);
	* ...
	* }
	* </code></pre>
	*/
	public interface ChildSection extends ReadSection {
	boolean moveToNext();

	boolean moveToNext(@NonNull String expectedChildTagName);
	}

	public static class ReadSectionImpl implements ChildSection {

	@Nullable
	private final InputStream mInput;

	@NonNull
	private final TypedXmlPullParser mParser;

	@NonNull
	private final Stack<Integer> mDepthStack = new Stack<>();

	public ReadSectionImpl(@NonNull InputStream input)
	throws IOException, XmlPullParserException {
	mInput = input;
	mParser = Xml.newFastPullParser();
	mParser.setInput(mInput, StandardCharsets.UTF_8.name());
	moveToFirstTag();
	}

	public ReadSectionImpl(@NonNull TypedXmlPullParser parser)
	throws IOException, XmlPullParserException {
	mInput = null;
	mParser = parser;
	moveToFirstTag();
	}

	private void moveToFirstTag() throws IOException, XmlPullParserException {
	if (mParser.getEventType() == XmlPullParser.START_TAG) {
	return;
	}

	int type;
	//noinspection StatementWithEmptyBody
	while ((type = mParser.next()) != XmlPullParser.START_TAG
	&& type != XmlPullParser.END_DOCUMENT) {
	}
	}

	@NonNull
	@Override
	public String getName() {
	return mParser.getName();
	}

	@NonNull
	@Override
	public String getDescription() {
	return mParser.getPositionDescription();
	}

	@Override
	public boolean has(String attrName) {
	return mParser.getAttributeValue(null, attrName) != null;
	}

	@Nullable
	@Override
	public String getString(String attrName) {
	return mParser.getAttributeValue(null, attrName);
	}

	@NonNull
	@Override
	public String getString(String attrName, @NonNull String defaultValue) {
	String value = mParser.getAttributeValue(null, attrName);
	if (value == null) {
	return defaultValue;
	}
	return value;
	}

	@Override
	public boolean getBoolean(String attrName) {
	return getBoolean(attrName, false);
	}

	@Override
	public boolean getBoolean(String attrName, boolean defaultValue) {
	return mParser.getAttributeBoolean(null, attrName, defaultValue);
	}

	@Override
	public int getInt(String attrName) {
	return getInt(attrName, DEFAULT_NUMBER);
	}

	@Override
	public int getInt(String attrName, int defaultValue) {
	return mParser.getAttributeInt(null, attrName, defaultValue);
	}

	@Override
	public long getLong(String attrName) {
	return getLong(attrName, DEFAULT_NUMBER);
	}

	@Override
	public long getLong(String attrName, int defaultValue) {
	return mParser.getAttributeLong(null, attrName, defaultValue);
	}

	@Override
	public ChildSection children() {
	mDepthStack.push(mParser.getDepth());
	return this;
	}

	@Override
	public boolean moveToNext() {
	return moveToNextInternal(null);
	}

	@Override
	public boolean moveToNext(@NonNull String expectedChildTagName) {
	return moveToNextInternal(expectedChildTagName);
	}

	private boolean moveToNextInternal(@Nullable String expectedChildTagName) {
	try {
	int depth = mDepthStack.peek();
	boolean hasTag = false;
	int type;
	while (!hasTag
	&& (type = mParser.next()) != XmlPullParser.END_DOCUMENT
	&& (type != XmlPullParser.END_TAG \|\| mParser.getDepth() > depth)) {
	if (type != XmlPullParser.START_TAG) {
	continue;
	}

	if (expectedChildTagName != null
	&& !expectedChildTagName.equals(mParser.getName())) {
	continue;
	}

	hasTag = true;
	}

	if (!hasTag) {
	mDepthStack.pop();
	}

	return hasTag;
	} catch (Exception ignored) {
	return false;
	}
	}

	@Override
	public void close() throws Exception {
	if (mDepthStack.isEmpty()) {
	Slog.wtf(TAG, "Children depth stack was not empty, data may have been lost",
	new Exception());
	}
	if (mInput != null) {
	mInput.close();
	}
	}
	}

	public interface WriteSection extends AutoCloseable {

	WriteSection startSection(@NonNull String sectionName) throws IOException;

	WriteSection attribute(String attrName, @Nullable String value) throws IOException;

	WriteSection attribute(String attrName, int value) throws IOException;

	WriteSection attribute(String attrName, long value) throws IOException;

	WriteSection attribute(String attrName, boolean value) throws IOException;

	@Override
	void close() throws IOException;

	void finish() throws IOException;
	}

	private static class WriteSectionImpl implements WriteSection {

	@NonNull
	private final TypedXmlSerializer mXmlSerializer;

	@NonNull
	private final Stack<String> mTagStack = new Stack<>();

	private WriteSectionImpl(@NonNull TypedXmlSerializer xmlSerializer) {
	mXmlSerializer = xmlSerializer;
	}

	@Override
	public WriteSection startSection(@NonNull String sectionName) throws IOException {
	// Try to start the tag first before we push it to the stack
	mXmlSerializer.startTag(null, sectionName);
	mTagStack.push(sectionName);
	return this;
	}

	@Override
	public WriteSection attribute(String attrName, String value) throws IOException {
	if (value != null) {
	mXmlSerializer.attribute(null, attrName, value);
	}
	return this;
	}

	@Override
	public WriteSection attribute(String attrName, int value) throws IOException {
	if (value != DEFAULT_NUMBER) {
	mXmlSerializer.attributeInt(null, attrName, value);
	}
	return this;
	}

	@Override
	public WriteSection attribute(String attrName, long value) throws IOException {
	if (value != DEFAULT_NUMBER) {
	mXmlSerializer.attributeLong(null, attrName, value);
	}
	return this;
	}

	@Override
	public WriteSection attribute(String attrName, boolean value) throws IOException {
	if (value) {
	mXmlSerializer.attributeBoolean(null, attrName, value);
	}
	return this;
	}

	@Override
	public void finish() throws IOException {
	close();
	}

	@Override
	public void close() throws IOException {
	mXmlSerializer.endTag(null, mTagStack.pop());
	}

	private void closeCompletely() throws IOException {
	if (DEBUG_THROW_EXCEPTIONS && mTagStack != null && !mTagStack.isEmpty()) {
	throw new IllegalStateException(
	"tag stack is not empty when closing, contains " + mTagStack);
	} else if (mTagStack != null) {
	while (!mTagStack.isEmpty()) {
	close();
	}
	}
	}
	}
	}