org.jlibrary.web.servlet.io.LimitedInputStream.java Source code

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Here is the source code for org.jlibrary.web.servlet.io.LimitedInputStream.java

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/*
* jLibrary, Open Source Document Management System
* 
* Copyright (c) 2003-2006, Martn Prez Marin, Blandware (represented by
* Andrey Grebnev), and individual contributors as indicated by the
* @authors tag. See copyright.txt in the distribution for a full listing of
* individual contributors. All rights reserved.
* 
* This is free software; you can redistribute it and/or modify it
* under the terms of the Modified BSD License as published by the Free 
* Software Foundation.
* 
* This software 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 Modified
* BSD License for more details.
* 
* You should have received a copy of the Modified BSD License along with 
* this software; if not, write to the Free Software Foundation, Inc., 
* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA, or see the
* FSF site: http://www.fsf.org.
*/
package org.jlibrary.web.servlet.io;

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

import org.apache.commons.io.input.ProxyInputStream;

/**
 * This input stream limits the amount of data that can be sent through it. The idea offer 
 * a way to avoid DOS attacks without having to touch the client side. If the caller tries 
 * to read too much data from this InputStream then an IOException will be called. The amount 
 * of data allowed to be read can be specified from the constructor.
 * 
 * @author mperez
 *
 */
public class LimitedInputStream extends FilterInputStream {

    private long byteCount;
    private long byteLimit;

    /**
     * Creates a limited input stream. This stream will just proxy all the calls to the 
     * input stream passed as parameter but it will count the amount of bytes readed. If the 
     * amount of bytes readed is bigger than the specified limit then an IOException will 
     * be thrown. 
     * 
     * @param proxy
     * @param byteLimit
     */
    public LimitedInputStream(InputStream proxy, long byteLimit) {

        super(proxy);
        this.byteLimit = byteLimit;
    }

    @Override
    public int available() throws IOException {
        // TODO Auto-generated method stub
        return super.available();
    }

    @Override
    public void close() throws IOException {
        // TODO Auto-generated method stub
        super.close();
    }

    @Override
    public synchronized void mark(int readlimit) {
        // TODO Auto-generated method stub
        super.mark(readlimit);
    }

    @Override
    public boolean markSupported() {
        // TODO Auto-generated method stub
        return super.markSupported();
    }

    @Override
    public synchronized void reset() throws IOException {
        // TODO Auto-generated method stub
        super.reset();
    }

    @Override
    public long skip(long n) throws IOException {
        // TODO Auto-generated method stub
        return super.skip(n);
    }

    @Override
    public int read() throws IOException {

        byteCount += 4;
        checkByteLimit();
        return super.read();
    }

    @Override
    public int read(byte[] bts) throws IOException {

        byteCount += bts.length;
        checkByteLimit();

        return super.read(bts);
    }

    @Override
    public int read(byte[] bts, int st, int end) throws IOException {

        byteCount += end - st + 1;
        checkByteLimit();
        return super.read(bts, st, end);
    }

    private void checkByteLimit() throws IOException {

        if (byteCount > byteLimit) {
            throw new IOException("This service is limited to " + byteLimit
                    + " bytes. The maximum allowed throughput has been exceeded.");
        }
    }

    /**
     * Returns the number of bytes that have been read through this Input Stream
     *  
     * @return long Number of bytes read
     */
    public long getByteCount() {
        return byteCount;
    }
}