XmlNodeChunk.java

/*
 * Copyright 2016 Google Inc. All Rights Reserved.
 *
 * 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.google.devrel.gmscore.tools.apk.arsc;

import java.nio.ByteBuffer;

import javax.annotation.Nullable;

/** The common superclass for the various types of XML nodes. */
public abstract class XmlNodeChunk extends Chunk {

  /** The line number in the original source at which this node appeared. */
  private final int lineNumber;

  /** A string reference of this node's comment. If this is -1, then there is no comment. */
  private final int comment;

  protected XmlNodeChunk(ByteBuffer buffer, @Nullable Chunk parent) {
    super(buffer, parent);
    lineNumber = buffer.getInt();
    comment = buffer.getInt();
  }

  /** Returns true if this XML node contains a comment. Else, returns false. */
  public boolean hasComment() {
    return comment != -1;
  }

  /** Returns the line number in the original source at which this node appeared. */
  public int getLineNumber() {
    return lineNumber;
  }

  /** Returns the comment associated with this node, if any. Else, returns the empty string. */
  public String getComment() {
    return getString(comment);
  }

  /**
   * An {@link XmlNodeChunk} does not know by itself what strings its indices reference. In order
   * to get the actual string, the first {@link XmlChunk} ancestor is found. The
   * {@link XmlChunk} ancestor should have a string pool which {@code index} references.
   *
   * @param index The index of the string.
   * @return String that the given {@code index} references, or empty string if {@code index} is -1.
   */
  protected String getString(int index) {
    if (index == -1) {  // Special case. Packed XML files use -1 for "no string entry"
      return "";
    }
    Chunk parent = getParent();
    while (parent != null) {
      if (parent instanceof XmlChunk) {
        return ((XmlChunk) parent).getString(index);
      }
      parent = parent.getParent();
    }
    throw new IllegalStateException("XmlNodeChunk did not have an XmlChunk parent.");
  }

  /**
   * An {@link XmlNodeChunk} and anything that is itself an {@link XmlNodeChunk} has a header size
   * of 16. Anything else is, interestingly, considered to be a payload. For that reason, this
   * method is final.
   */
  @Override
  protected final void writeHeader(ByteBuffer output) {
    super.writeHeader(output);
    output.putInt(lineNumber);
    output.putInt(comment);
  }

  /**
   * Returns a brief description of this XML node. The representation of this information is
   * subject to change, but below is a typical example:
   *
   * <pre>"XmlNodeChunk{line=1234, comment=My awesome comment.}"</pre>
   */
  @Override
  public String toString() {
    return String.format("XmlNodeChunk{line=%d, comment=%s}", getLineNumber(), getComment());
  }
}