import java.io.*;
import java.security.*;
import java.util.*;

public class ListCallbackDigest implements Runnable {

  private File input;
  List listenerList = new Vector();

  public ListCallbackDigest(File input) {
   this.input = input;
  }
 
  public synchronized void addDigestListener(DigestListener l) {
    listenerList.add(l);
  }
  
  public synchronized void removeDigestListener(DigestListener l) {
    listenerList.remove(l);
  } 
    
  private synchronized  void sendDigest(byte[] digest) {

    ListIterator iterator = listenerList.listIterator();
    while (iterator.hasNext()) {
      DigestListener dl = (DigestListener) iterator.next();
      dl.digestCalculated(digest);
    }

  }  

  public void run() {

    try {
      FileInputStream in = new FileInputStream(input);
      MessageDigest sha = MessageDigest.getInstance("SHA");
      DigestInputStream din = new DigestInputStream(in, sha);
      int b;
      while ((b = din.read()) != -1) ;
      din.close();
      byte[] digest = sha.digest();
      this.sendDigest(digest);
    }
    catch (IOException ex) {
      System.err.println(ex);
    }
    catch (NoSuchAlgorithmException ex) {
      System.err.println(ex);
    }
    
  }

}