/*
 * MessageInputStream.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., 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
 * 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.FilterInputStream;
import java.io.InputStream;
import java.io.IOException;

/**
 * A utility class for feeding message contents to messages.
 * This stream returns -1 from <code>read</code> when the stream termination
 * sequence LF,END,LF is read from the underlying stream.
 *
 * @author <a href="mailto:dog@gnu.org">Chris Burdess</a>
 */
public class MessageInputStream
  extends FilterInputStream
{

  /**
   * The stream termination octet ('.').
   */
  public static final int END = 46;

  /**
   * The line termination octet ('\n').
   */
  public static final int LF = 10;

  protected boolean eof;

  protected int buf1 = -1;
  protected int buf2 = -1;

  protected int markBuf1;
  protected int markBuf2;

  /**
   * Constructs a message input stream connected to the specified input stream.
   */
  public MessageInputStream(InputStream in)
  {
    super(in);
    eof = false;
  }

  /**
   * Reads the next byte of data from this message input stream.
   * Returns -1 if the end of the message stream has been reached.
   * @exception IOException if an I/O error occurs
   */
  public int read()
    throws IOException
  {
    if (eof)
      {
        return -1;
      }
    int c;
    if (buf1 != -1)
      {
        c = buf1;
        buf1 = buf2;
        buf2 = -1;
      }
    else
      {
        c = super.read();
      }
    if (c == LF)
      {
        if (buf1 == -1)
          {
            buf1 = super.read();
            if (buf1 == END)
              {
                buf2 = super.read();
                if (buf2 == LF)
                  {
                    eof = true;
                    // Allow the final LF to be read
                  }
              }
          }
        else if (buf1 == END)
          {
            if (buf2 == -1)
              {
                buf2 = super.read();
                if (buf2 == LF)
                  {
                    eof = true;
                  }
              }
            else if (buf2 == LF)
              {
                eof = true;
              }
          }
      }
    return c;
  }
  
  /**
   * Reads up to b.length bytes of data from this input stream into
   * an array of bytes.
   * Returns -1 if the end of the stream has been reached.
   * @exception IOException if an I/O error occurs
   */
  public int read(byte[] b)
    throws IOException
  {
    return read(b, 0, b.length);
  }

  /**
   * Reads up to len bytes of data from this input stream into an
   * array of bytes, starting at the specified offset.
   * Returns -1 if the end of the stream has been reached.
   * @exception IOException if an I/O error occurs
   */
  public int read(byte[] b, int off, int len)
    throws IOException
  {
    if (eof)
      {
        return -1;
      }
    int c, end = off + len;
    for (int i = off; i < end; i++)
      {
        c = read();
        if (c == -1)
          {
            len = i - off;
            break;
          }
        else
          {
            b[i] = (byte) c;
          }
      }
    return len;
  }
  
  public boolean markSupported()
  {
    return in.markSupported();
  }

  public void mark(int readlimit)
  {
    in.mark(readlimit);
    markBuf1 = buf1;
    markBuf2 = buf2;
  }

  public void reset()
    throws IOException
  {
    in.reset();
    buf1 = markBuf1;
    buf2 = markBuf2;
    eof = false;
  }

}