content: /*
   *  Licensed to the Apache Software Foundation (ASF) under one or more
   *  contributor license agreements.  See the NOTICE file distributed with
   *  this work for additional information regarding copyright ownership.
   *  The ASF licenses this file to You 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
   *
   *      https://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 org.apache.tools.ant.types.selectors.modifiedselector;
  
  import java.io.BufferedInputStream;
  import java.io.File;
  import java.nio.file.Files;
  import java.security.NoSuchAlgorithmException;
  import java.util.Locale;
  import java.util.zip.Adler32;
  import java.util.zip.CRC32;
  import java.util.zip.CheckedInputStream;
  import java.util.zip.Checksum;
  
  import org.apache.tools.ant.BuildException;
  
  
  /**
   * Computes a 'checksum' for the content of file using
   * java.util.zip.CRC32 and java.util.zip.Adler32.
   * Use of this algorithm doesn't require any additional nested &lt;param&gt;s.
   * Supported &lt;param&gt;s are:
   * <table>
   * <caption>Checksum algorithm parameters</caption>
   * <tr>
   *   <th>name</th><th>values</th><th>description</th><th>required</th>
   * </tr>
   * <tr>
   *   <td>algorithm.algorithm</td>
   *   <td>ADLER | CRC (default)</td>
   *   <td>name of the algorithm the checksum should use</td>
   *   <td>no, defaults to CRC</td>
   * </tr>
   * </table>
   *
   * @version 2004-06-17
   * @since  Ant 1.7
   */
  public class ChecksumAlgorithm implements Algorithm {
  
  
      // -----  member variables  -----
  
  
      /**
       * Checksum algorithm to be used.
       */
      private String algorithm = "CRC";
  
      /**
       * Checksum interface instance
       */
      private Checksum checksum = null;
  
  
      // -----  Algorithm-Configuration  -----
  
  
      /**
       * Specifies the algorithm to be used to compute the checksum.
       * Defaults to "CRC". Other popular algorithms like "ADLER" may be used as well.
       * @param algorithm the digest algorithm to use
       */
      public void setAlgorithm(String algorithm) {
          this.algorithm =
              algorithm != null ? algorithm.toUpperCase(Locale.ENGLISH) : null;
      }
  
  
      /** Initialize the checksum interface. */
      public void initChecksum() {
          if (checksum != null) {
              return;
          }
          if ("CRC".equals(algorithm)) {
              checksum = new CRC32();
          } else if ("ADLER".equals(algorithm)) {
              checksum = new Adler32();
          } else {
              throw new BuildException(new NoSuchAlgorithmException());
          }
      }
  
  
      // -----  Logic  -----
  
  
      /**
       * This algorithm supports only CRC and Adler.
       * @return <i>true</i> if all is ok, otherwise <i>false</i>.
       */
      @Override
      public boolean isValid() {
          return "CRC".equals(algorithm) || "ADLER".equals(algorithm);
      }
  
  
      /**
       * Computes a value for a file content with the specified checksum algorithm.
       * @param file    File object for which the value should be evaluated.
       * @return        The value for that file
       */
      @Override
      public String getValue(File file) {
          initChecksum();
  
          if (file.canRead()) {
              checksum.reset();
              try (CheckedInputStream check = new CheckedInputStream(
                  new BufferedInputStream(Files.newInputStream(file.toPath())), checksum)) {
                  // Read the file
                  while (check.read() != -1) {
                  }
                  return Long.toString(check.getChecksum().getValue());
              } catch (Exception ignored) {
              }
          }
          return null;
      }
  
  
      /**
       * Override Object.toString().
       * @return some information about this algorithm.
       */
      @Override
      public String toString() {
          return String.format("<ChecksumAlgorithm:algorithm=%s>", algorithm);
      }
  }
  