/*
 * $Id: CRLFInputStream.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;

/**
 * An input stream that filters out CR/LF pairs into LFs.
 *
 * @author <a href="mailto:dog@gnu.org">Chris Burdess</a>
 * @version $Revision: 1.3 $ $Date: 2004/06/08 19:05:28 $
 */
public class CRLFInputStream extends FilterInputStream
{

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

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

  /**
   * Buffer.
   */
  protected int buf = -1;

  /**
   * Buffer at time of mark.
   */
  protected int markBuf = -1;

  /**
   * Constructs a CR/LF input stream connected to the specified input
   * stream.
   */
  public CRLFInputStream (InputStream in)
    {
      super (in);
    }

  /**
   * Reads the next byte of data from this input stream.
   * Returns -1 if the end of the stream has been reached.
   * @exception IOException if an I/O error occurs
   */
  public int read () throws IOException
    {
      int c;
      if (buf != -1)
        {
          c = buf;
          buf = -1;
          return c;
        }
      else
        {
          c = super.read ();
          if (c == CR)
            {
              buf = super.read ();
              if (buf == LF)
                {
                  c = buf;
                  buf = -1;
                }
            }
        }
      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
    {
      int shift = 0;
      if (buf != -1)
        {
          // Push buf onto start of byte array
          b[off] = (byte) buf;
          off++;
          len--;
          buf = -1;
          shift++;
        }
      int l = super.read (b, off, len);
      l = removeCRLF (b, off - shift, l);
      return l;
    }

  /**
   * Indicates whether this stream supports the mark and reset methods.
   */
  public boolean markSupported ()
    {
      return in.markSupported ();
    }

  /**
   * Marks the current position in this stream.
   */
  public void mark (int readlimit)
    {
      in.mark (readlimit);
      markBuf = buf;
    }

  /**
   * Repositions this stream to the position at the time the mark method was
   * called.
   */
  public void reset () throws IOException
    {
      in.reset ();
      buf = markBuf;
    }

  private int removeCRLF (byte[] b, int off, int len)
    {
      int end = off + len;
      for (int i = off; i < end; i++)
        {
          if (b[i] == CR)
            {
              if (i + 1 == end)
                {
                  // This is the last byte, impossible to determine whether CRLF
                  buf = CR;
                  len--;
                }
              else if (b[i + 1] == LF)
                {
                  // Shift left
                  end--;
                  for (int j = i; j < end; j++)
                    {
                      b[j] = b[j + 1];
                    }
                  len--;
                  end = off + len;
                }
            }
        }
      return len;
    }

}
