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/*
 * CRLFOutputStream.java
 * 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
 *
 * 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
 * obliged to do so.  If you do not wish to do so, delete this
 * exception statement from your version.
 */

package gnu.inet.util;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;

/** 
 * An output stream that filters LFs into CR/LF pairs.
 *
 * @author Chris Burdess
 */
public class CRLFOutputStream
  extends FilterOutputStream
{

  static final String US_ASCII = "US-ASCII";

  /**
   * The CR octet.
   */
  public static final int CR = 13;

  /**
   * The LF octet.
   */
  public static final int LF = 10;

  /**
   * The CR/LF pair.
   */
  public static final byte[] CRLF = { CR, LF };

  /**
   * The last byte read.
   */
  protected int last;

  /**
   * Constructs a CR/LF output stream connected to the specified output stream.
   */
  public CRLFOutputStream(OutputStream out)
  {
    super(out);
    last = -1;
  }

  /**
   * Writes a character to the underlying stream.
   * @exception IOException if an I/O error occurred
   */
  public void write(int ch) throws IOException
  {
    if (ch == CR)
      {
        out.write(CRLF);
      }
    else if (ch == LF)
      {
        if (last != CR)
          {
            out.write(CRLF);
          }
      }
    else
      {
        out.write(ch);
      }
    last = ch;
  }
  
  /**
   * Writes a byte array to the underlying stream.
   * @exception IOException if an I/O error occurred
   */
  public void write(byte[] b)
    throws IOException
  {
    write(b, 0, b.length);
  }

  /**
   * Writes a portion of a byte array to the underlying stream.
   * @exception IOException if an I/O error occurred
   */
  public void write(byte[] b, int off, int len)
    throws IOException
  {
    int d = off;
    len += off;
    for (int i = off; i < len; i++)
      {
        switch (b[i])
          {
          case CR:
            out.write (b, d, i - d);
            out.write (CRLF, 0, 2);
            d = i + 1;
            break;
          case LF:
            if (last != CR)
              {
                out.write (b, d, i - d);
                out.write (CRLF, 0, 2);
              }
            d = i + 1;
            break;
          }
        last = b[i];
      }
    if (len - d > 0)
      {
        out.write (b, d, len - d);
      }
  }
  
  /**
   * Writes the specified ASCII string to the underlying stream.
   * @exception IOException if an I/O error occurred
   */
  public void write(String text)
    throws IOException
  {
    try
      {
        byte[] bytes = text.getBytes(US_ASCII);
        write(bytes, 0, bytes.length);
        }
    catch (UnsupportedEncodingException e)
      {
        throw new IOException("The US-ASCII encoding is not supported " +
                              "on this system");
      }
  }

  /**
   * Writes a newline to the underlying stream.
   * @exception IOException if an I/O error occurred
   */
  public void writeln()
    throws IOException
  {
    out.write(CRLF, 0, 2);
  }

}