/*
 * $Id: SaslInputStream.java,v 1.3 2004/06/08 19:05:28 dog Exp $
 * Copyright (C) 2002 The Free Software Foundation
 * 
 * This file is part of GNU inetlib, a library.
 * 
 * GNU inetlib is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * GNU inetlib is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * As a special exception, if you link this library with other files to
 * produce an executable, this library does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
 * This exception does not however invalidate any other reasons why the
 * executable file might be covered by the GNU General Public License.
 */

package gnu.inet.util;

import java.io.FilterInputStream;
import java.io.InputStream;
import java.io.IOException;

import javax.security.sasl.SaslClient;

/**
 * A filter input stream that decodes all its received input using a SASL
 * client.
 *
 * @author <a href="mailto:dog@gnu.org">Chris Burdess</a>
 * @version $Revision: 1.3 $ $Date: 2004/06/08 19:05:28 $
 */
public class SaslInputStream extends FilterInputStream
{

  /*
   * The SASL client.
   */
  private final SaslClient sasl;

  /*
   * Overflow buffer.
   */
  private byte[] buf;

  /*
   * Offset in overflow buffer.
   */
  private int pos;

  /**
   * Constructor.
   * @param sasl the SASL client
   * @param in the underlying input stream
   */
  public SaslInputStream (SaslClient sasl, InputStream in)
    {
      super (in);
      this.sasl = sasl;
    }

  /**
   * Reads a single character.
   */
  public int read () throws IOException
    {
      if (buf != null)
        {
          // Return next characer in buffer
          int c = (int) buf[pos++];
          if (pos == buf.length)
            {
              buf = null;
            }
          return c;
        }
      int c = super.read ();
      if (c == -1)
        {
          return c;
        }
      byte[] bytes = new byte[1];
      byte[] unwrapped = sasl.unwrap (bytes, 0, 1);
      // FIXME if we get 0 bytes, we have a problem
      c = (int) unwrapped[0];
      if (unwrapped.length > 1)
        {
          // Store in overflow buffer
          int l = unwrapped.length - 1;
          buf = new byte[l];
          System.arraycopy (unwrapped, 1, buf, 0, l);
          pos = 0;
        }
      return c;
    }

  public int read (byte[] bytes) throws IOException
    {
      return read (bytes, 0, bytes.length);
    }

  /**
   * Block read.
   */
  public int read (byte[] bytes, int off, int len) throws IOException
    {
      if (buf != null)
        {
          // Return bytes from buffer
          int l = buf.length;
          if (l - pos <= len)
            {
              System.arraycopy (buf, pos, bytes, off, l);
              buf = null;
              return l;
            }
          else
            {
              System.arraycopy (buf, pos, bytes, off, len);
              pos += len;
              return len;
            }
        }
      int l = super.read (bytes, off, len);
      if (l == -1)
        {
          return l;
        }
      byte[] unwrapped = sasl.unwrap (bytes, off, l);
      int l2 = unwrapped.length;
      if (l2 > len)
        {
          // Store excess bytes in buffer
          int d = l2 - len;
          buf = new byte[d];
          System.arraycopy (unwrapped, 0, bytes, off, len);
          System.arraycopy (unwrapped, len, buf, 0, d);
          pos = 0;
          return len;
        }
      else
        {
          System.arraycopy (unwrapped, 0, bytes, off, l2);
          // Zero bytes from l2..l to ensure none of the original
          // bytes received can be read by the caller
          for (int i = l2; i < l; i++)
            {
              bytes[off + l2] = 0;
            }
          return l2;
        }
    }

}