/***************************************************************************
 *   Copyright (C) 2006-2010 by Fabrizio Montesi <famontesi@gmail.com>     *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU Library General Public License as       *
 *   published by the Free Software Foundation; either version 2 of the    *
 *   License, or (at your option) any later version.                       *
 *                                                                         *
 *   This program 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 Library General Public     *
 *   License along with this program; if not, write to the                 *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 *                                                                         *
 *   For details about the authors of this software, see the AUTHORS file. *
 ***************************************************************************/


package jolie.net;

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

public class PreBufferedInputStream extends InputStream
{
	private static final int INITIAL_BUFFER_SIZE = 10;
	private final InputStream istream;
	private byte[] buffer = new byte[ INITIAL_BUFFER_SIZE ];
	private int writePos = 0;
	private int readPos = 0;
	private int count = 0;

	public PreBufferedInputStream( InputStream istream )
	{
		this.istream = istream;
	}

	public synchronized boolean hasCachedData()
	{
		return count > 0;
	}

	public synchronized int read()
		throws IOException
	{
		if ( buffer == null ) {
			throw new IOException( "Stream closed" );
		}

		if ( count < 1 ) { // No bytes to read
			return istream.read();
		}

		count--;
		if ( readPos >= buffer.length ) {
			readPos = 0;
		}

		return buffer[ readPos++ ];
	}

	public synchronized void append( byte b )
		throws IOException
	{
		if ( buffer == null ) {
			throw new IOException( "Stream closed" );
		}

		count++;
		if ( count >= buffer.length ) { // We need to enlarge the buffer
			byte[] newBuffer = new byte[ buffer.length * 2 ];
			System.arraycopy( buffer, 0, newBuffer, 0, buffer.length );
			buffer = newBuffer;
		}
		if ( writePos >= buffer.length ) {
			writePos = 0;
		}
		buffer[ writePos ] = b;

		writePos++;
	}

	@Override
	public synchronized void close()
		throws IOException
	{
		buffer = null;
	}
}