package gnu.crypto.sasl;

// ----------------------------------------------------------------------------
// $Id: OutputBuffer.java,v 1.5 2005/10/06 04:24:18 rsdio Exp $
//
// Copyright (C) 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto 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, or (at your option)
// any later version.
//
// GNU Crypto 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 program; see the file COPYING.  If not, write to the
//
//    Free Software Foundation Inc.,
//    51 Franklin Street, Fifth Floor,
//    Boston, MA 02110-1301
//    USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
// license of that module.  An independent module is a module which is
// not derived from or based on this library.  If you modify this
// library, you may extend this exception to your version of the
// library, but you are not obligated to do so.  If you do not wish to
// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------

import gnu.crypto.Registry;
import gnu.crypto.util.Util;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.math.BigInteger;

/**
 * <p>The implementation of an outgoing SASL buffer.</p>
 *
 * <p>The data elements this class caters for are described in [1].</p>
 *
 * <p>References:</p>
 * <ol>
 *    <li><a href="http://www.ietf.org/internet-drafts/draft-burdis-cat-srp-sasl-09.txt">
 *    Secure Remote Password Authentication Mechanism</a>;<br/>
 *    draft-burdis-cat-srp-sasl-09,<br/>
 *    <a href="mailto:keith@rucus.ru.ac.za">Keith Burdis</a> and
 *    <a href="mailto:raif@forge.com.au">Ra&iuml;f S. Naffah</a>.</li>
 * </ol>
 *
 * @version $Revision: 1.5 $
 */
public class OutputBuffer {

   // Constants and variables
   // -------------------------------------------------------------------------

   /** The internal output stream. */
   private ByteArrayOutputStream out;

   // Constructor(s)
   // -------------------------------------------------------------------------

   public OutputBuffer() {
      super();

      out = new ByteArrayOutputStream();
   }

   // Class methods
   // -------------------------------------------------------------------------

   // Instance methods
   // -------------------------------------------------------------------------

   /**
    * <p>Encodes a SASL scalar quantity, <code>count</code>-octet long, to the
    * current buffer.</p>
    *
    * @param count number of octets to encode <code>b</code> with.
    * @param b the scalar quantity.
    * @throws SaslEncodingException if an encoding size constraint is violated.
    * @throws IOException if any other I/O exception occurs during the operation.
    */
   public void setScalar(int count, int b) throws IOException {
      if (count < 0 || count > 4) {
         throw new SaslEncodingException("Invalid SASL scalar octet count: "
            +String.valueOf(count));
      }
      byte[] element = new byte[count];
      for (int i = count; --i >= 0; b >>>= 8) {
         element[i] = (byte) b;
      }
      out.write(element);
   }

   /**
    * <p>Encodes a SASL OS to the current buffer.</p>
    *
    * @param b the OS element.
    * @throws SaslEncodingException if an encoding size constraint is violated.
    * @throws IOException if any other I/O exception occurs during the operation.
    */
   public void setOS(byte[] b) throws IOException {
      final int length = b.length;
      if (length > Registry.SASL_ONE_BYTE_MAX_LIMIT) {
         throw new SaslEncodingException("SASL octet-sequence too long");
      }
      out.write(length & 0xFF);
      out.write(b);
   }

   /**
    * <p>Encodes a SASL EOS to the current buffer.</p>
    *
    * @param b the EOS element.
    * @throws SaslEncodingException if an encoding size constraint is violated.
    * @throws IOException if any other I/O exception occurs during the operation.
    */
   public void setEOS(byte[] b) throws IOException {
      final int length = b.length;
      if (length > Registry.SASL_TWO_BYTE_MAX_LIMIT) {
         throw new SaslEncodingException("SASL extended octet-sequence too long");
      }
      byte[] lengthBytes = { (byte)(length >>> 8), (byte) length };
      out.write(lengthBytes);
      out.write(b);
   }

   /**
    * <p>Encodes a SASL MPI to the current buffer.</p>
    *
    * @param val the MPI element.
    * @throws SaslEncodingException if an encoding size constraint is violated.
    * @throws IOException if any other I/O exception occurs during the operation.
    */
   public void setMPI(BigInteger val) throws IOException {
      byte[] b = Util.trim(val);
      final int length = b.length;
      if (length > Registry.SASL_TWO_BYTE_MAX_LIMIT) {
         throw new SaslEncodingException("SASL multi-precision integer too long");
      }
      byte[] lengthBytes = { (byte)(length >>> 8), (byte) length };
      out.write(lengthBytes);
      out.write(b);
   }

   /**
    * <p>Encodes a SASL Text to the current buffer.</p>
    *
    * @param str the Text element.
    * @throws SaslEncodingException if an encoding size constraint is violated.
    * @throws SaslEncodingException if the UTF-8 encoding is not supported on
    * this platform.
    * @throws IOException if any other I/O exception occurs during the operation.
    */
   public void setText(String str) throws IOException {
      byte[] b = str.getBytes("UTF8");
      final int length = b.length;
      if (length > Registry.SASL_TWO_BYTE_MAX_LIMIT) {
         throw new SaslEncodingException("SASL text too long");
      }
      byte[] lengthBytes = { (byte)(length >>> 8), (byte) length };
      out.write(lengthBytes);
      out.write(b);
   }

   /**
    * <p>Returns the encoded form of the current buffer including the 4-byte
    * length header.</p>
    *
    * @throws SaslEncodingException if an encoding size constraint is violated.
    */
   public byte[] encode() throws SaslEncodingException {
      byte[] buffer = wrap();
      final int length = buffer.length;
      byte[] result = new byte[length+4];
      result[0] = (byte)(length >>> 24);
      result[1] = (byte)(length >>> 16);
      result[2] = (byte)(length >>>  8);
      result[3] = (byte) length;
      System.arraycopy(buffer, 0, result, 4, length);

      return result;
   }

   /**
    * <p>Returns the encoded form of the current buffer excluding the 4-byte
    * length header.</p>
    *
    * @throws SaslEncodingException if an encoding size constraint is violated.
    */
   public byte[] wrap() throws SaslEncodingException {
      final int length = out.size();
      if (length > Registry.SASL_BUFFER_MAX_LIMIT || length < 0) {
         throw new SaslEncodingException("SASL buffer too long");
      }
      return out.toByteArray();
   }
}
