content: /*
   * Copyright (C) 2017 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.net.watchlist;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  
  /**
   * Utils for calculating digests.
   */
  public class DigestUtils {
  
      private static final int FILE_READ_BUFFER_SIZE = 16 * 1024;
  
      private DigestUtils() {}
  
      /** @return SHA256 hash of the provided file */
      public static byte[] getSha256Hash(File apkFile) throws IOException, NoSuchAlgorithmException {
          try (InputStream stream = new FileInputStream(apkFile)) {
              return getSha256Hash(stream);
          }
      }
  
      /** @return SHA256 hash of data read from the provided input stream */
      public static byte[] getSha256Hash(InputStream stream)
              throws IOException, NoSuchAlgorithmException {
          MessageDigest digester = MessageDigest.getInstance("SHA256");
  
          int bytesRead;
          byte[] buf = new byte[FILE_READ_BUFFER_SIZE];
          while ((bytesRead = stream.read(buf)) >= 0) {
              digester.update(buf, 0, bytesRead);
          }
          return digester.digest();
      }
  }