ReplayableInputStream.java

/**
 *  Copyright (C) 2002-2012   The FreeCol Team
 *
 *  This file is part of FreeCol.
 *
 *  FreeCol 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.
 *
 *  FreeCol 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 FreeCol.  If not, see <http://www.gnu.org/licenses/>.
 */


package net.sf.freecol.common.util;


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


/**
 * Wraps a {@link java.io.InputStream} and adds
 * {@link java.io.InputStream#mark(int)} and {@link java.io.InputStream#reset()}
 * support.
 */
public final class ReplayableInputStream extends InputStream {

    private static final  int  NORMAL    = 0;
    private static final  int  RECORDING = 1;
    private static final  int  REPLAYING = 2;

    private final  InputStream  underlyingStream;

    private  int     state;
    private  byte[]  replayBuffer;
    private  int     recordedBytes;
    private  int     replayedBytes;


    public ReplayableInputStream( InputStream in ) {

        underlyingStream = in;
    }


    public int read() throws IOException {

        int  i;
        if ( REPLAYING == state  &&  replayedBytes < recordedBytes) {

            i = replayBuffer[replayedBytes ++];
        }
        else {
            i = underlyingStream.read();
            // if the end of the stream has not been reached and a mark has been
            // set..
            if (i != -1  &&  RECORDING == state) {
                // if there is enough space in the replay buffer..
                if ( recordedBytes < replayBuffer.length) {
                    replayBuffer[recordedBytes ++] = (byte) i;
                }
                else {
                    // the mark has been invalidated
                    state = NORMAL;
                }
            }
        }
        return i;
    }


    public boolean markSupported() {

        return true;
    }


    public synchronized void mark( int readlimit) {

        replayBuffer = new byte[readlimit];
        state = RECORDING;
        recordedBytes = 0;
    }


    public synchronized void reset() throws IOException {

        if ( state != RECORDING) {
            throw new IOException( "no mark set" );
        }
        state = REPLAYING;
        replayedBytes = 0;
    }

}