ApkUtils.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.common;

import com.google.common.io.ByteStreams;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.Enumeration;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.regex.Pattern;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;

/**
 * Utilities for working with apk files.
 */
public final class ApkUtils {

  private ApkUtils() {}  // Prevent instantiation

  /**
   * Returns a file whose name matches {@code filename}, or null if no file was found.
   *
   * @param apkFile The file containing the apk zip archive.
   * @param filename The full filename (e.g. res/raw/foo.bar).
   * @return A byte array containing the contents of the matching file, or null if not found.
   * @throws IOException Thrown if there's a matching file, but it cannot be read from the apk.
   */
  public static byte[] getFile(File apkFile, String filename) throws IOException {
    Map<String, byte[]> files = getFiles(apkFile, Pattern.quote(filename));
    return files.get(filename);
  }

  /**
   * Returns all files in an apk that match a given regular expression.
   *
   * @param apkFile The file containing the apk zip archive.
   * @param regex A regular expression to match the requested filenames.
   * @return A mapping of the matched filenames to their byte contents.
   * @throws IOException Thrown if a matching file cannot be read from the apk.
   */
  public static Map<String, byte[]> getFiles(File apkFile, String regex) throws IOException {
    return getFiles(apkFile, Pattern.compile(regex));
  }

  /**
   * Returns all files in an apk that match a given regular expression.
   *
   * @param apkFile The file containing the apk zip archive.
   * @param regex A regular expression to match the requested filenames.
   * @return A mapping of the matched filenames to their byte contents.
   * @throws IOException Thrown if a matching file cannot be read from the apk.
   */
  public static Map<String, byte[]> getFiles(File apkFile, Pattern regex) throws IOException {
    Map<String, byte[]> files = new LinkedHashMap<>();  // Retain insertion order
    // Extract apk
    try (ZipFile apkZip = new ZipFile(apkFile)) {
      Enumeration<? extends ZipEntry> zipEntries = apkZip.entries();
      while (zipEntries.hasMoreElements()) {
        ZipEntry zipEntry = zipEntries.nextElement();
        // Visit all files with the given extension
        if (regex.matcher(zipEntry.getName()).matches()) {
          // Map class name to definition
          try (InputStream is = new BufferedInputStream(apkZip.getInputStream(zipEntry))) {
            files.put(zipEntry.getName(), ByteStreams.toByteArray(is));
          }
        }
      }
    }
    return files;
  }
}