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.File;
  import java.io.IOException;
  import java.nio.file.Files;
  import java.security.DigestInputStream;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  import java.security.NoSuchProviderException;
  import java.util.Locale;
  
  import org.apache.tools.ant.BuildException;
  
  
  /**
   * Computes a 'hashvalue' for the content of file using
   * java.security.MessageDigest.
   * Use of this algorithm doesn't require any additional nested &lt;param&gt;s.
   * Supported &lt;param&gt;s are:
   * <table>
   * <caption>Digest algorithm parameters</caption>
   * <tr>
   *   <th>name</th><th>values</th><th>description</th><th>required</th>
   * </tr>
   * <tr>
   *   <td>algorithm.algorithm</td>
   *   <td>MD5 | SHA (default provider)</td>
   *   <td>name of the algorithm the provider should use</td>
   *   <td>no, defaults to MD5</td>
   * </tr>
   * <tr>
   *   <td> algorithm.provider</td>
   *   <td></td>
   *   <td>name of the provider to use</td>
   *   <td>no, defaults to <i>null</i></td>
   * </tr>
   * </table>
   *
   * @version 2004-07-08
   * @since  Ant 1.6
   */
  public class DigestAlgorithm implements Algorithm {
  
      private static final int BYTE_MASK = 0xFF;
      private static final int BUFFER_SIZE = 8192;
  
      // -----  member variables  -----
  
  
      /**
       * MessageDigest algorithm to be used.
       */
      private String algorithm = "MD5";
  
      /**
       * MessageDigest Algorithm provider
       */
      private String provider = null;
  
      /**
       * Message Digest instance
       */
      private MessageDigest messageDigest = null;
  
      /**
       * Size of the read buffer to use.
       */
      private int readBufferSize = BUFFER_SIZE;
  
  
      // -----  Algorithm-Configuration  -----
  
  
      /**
       * Specifies the algorithm to be used to compute the checksum.
       * Defaults to "MD5". Other popular algorithms like "SHA" 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;
      }
  
  
      /**
       * Sets the MessageDigest algorithm provider to be used
       * to calculate the checksum.
       * @param provider provider to use
       */
      public void setProvider(String provider) {
          this.provider = provider;
      }
  
  
      /** Initialize the security message digest. */
      public void initMessageDigest() {
          if (messageDigest != null) {
              return;
          }
  
          if (provider != null && !provider.isEmpty() && !"null".equals(provider)) {
              try {
                  messageDigest = MessageDigest.getInstance(algorithm, provider);
              } catch (NoSuchAlgorithmException | NoSuchProviderException e) {
                  throw new BuildException(e);
              }
          } else {
              try {
                  messageDigest = MessageDigest.getInstance(algorithm);
              } catch (NoSuchAlgorithmException noalgo) {
                  throw new BuildException(noalgo);
              }
          }
      }
  
  
      // -----  Logic  -----
  
  
      /**
       * This algorithm supports only MD5 and SHA.
       * @return <i>true</i> if all is ok, otherwise <i>false</i>.
       */
      @Override
      public boolean isValid() {
          return "SHA".equals(algorithm) || "MD5".equals(algorithm);
      }
  
      /**
       * Computes a value for a file content with the specified digest algorithm.
       * @param file    File object for which the value should be evaluated.
       * @return        The value for that file
       */
      // implementation adapted from ...taskdefs.Checksum, thanks to Magesh for hint
      @Override
      public String getValue(File file) {
          if (!file.canRead()) {
              return null;
          }
          initMessageDigest();
          byte[] buf = new byte[readBufferSize];
          messageDigest.reset();
          try (DigestInputStream dis = new DigestInputStream(Files.newInputStream(file.toPath()),
                  messageDigest)) {
              // read the whole stream
              while (dis.read(buf, 0, readBufferSize) != -1) {
              }
              StringBuilder checksumSb = new StringBuilder();
              for (byte digestByte : messageDigest.digest()) {
                  checksumSb.append(String.format("%02x", BYTE_MASK & digestByte));
              }
              return checksumSb.toString();
          } catch (IOException ignored) {
              return null;
          }
      }
  
      /**
       * Override Object.toString().
       * @return some information about this algorithm.
       */
      @Override
      public String toString() {
          return String.format("<DigestAlgorithm:algorithm=%s;provider=%s>",
              algorithm, provider);
      }
  }
  