LimitedInputStream.java

/*
 * Copyright 2004-2010 the Seasar Foundation and the Others.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */
package org.slim3.controller.upload;

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

/**
 * An input stream, which limits its data size. This stream is used, if the
 * content length is unknown.
 * 
 * @author higa
 * @since 1.0.0
 */
public abstract class LimitedInputStream extends FilterInputStream {

    /**
     * The maximum size of an item, in bytes.
     */
    protected long sizeMax;

    /**
     * The current number of bytes.
     */
    protected long count;

    /**
     * Creates a new instance.
     * 
     * @param pIn
     *            The input stream, which shall be limited.
     * @param pSizeMax
     *            The limit; no more than this number of bytes shall be returned
     *            by the source stream.
     */
    public LimitedInputStream(InputStream pIn, long pSizeMax) {
        super(pIn);
        sizeMax = pSizeMax;
    }

    /**
     * Called to indicate, that the input streams limit has been exceeded.
     * 
     * @param pSizeMax
     *            The input streams limit, in bytes.
     * @param pCount
     *            The actual number of bytes.
     * @throws IOException
     *             The called method is expected to raise an IOException.
     */
    protected abstract void raiseError(long pSizeMax, long pCount)
            throws IOException;

    /**
     * Called to check, whether the input streams limit is reached.
     * 
     * @throws IOException
     *             The given limit is exceeded.
     */
    protected void checkLimit() throws IOException {
        if (count > sizeMax) {
            raiseError(sizeMax, count);
        }
    }

    /**
     * Reads the next byte of data from this input stream. The value byte is
     * returned as an <code>int</code> in the range <code>0</code> to
     * <code>255</code>. If no byte is available because the end of the stream
     * has been reached, the value <code>-1</code> is returned. This method
     * blocks until input data is available, the end of the stream is detected,
     * or an exception is thrown.
     * <p>
     * This method simply performs <code>in.read()</code> and returns the
     * result.
     * 
     * @return the next byte of data, or <code>-1</code> if the end of the
     *         stream is reached.
     * @exception IOException
     *                if an I/O error occurs.
     * @see java.io.FilterInputStream#in
     */
    @Override
    public int read() throws IOException {
        int res = super.read();
        if (res != -1) {
            count++;
            checkLimit();
        }
        return res;
    }

    /**
     * Reads up to <code>len</code> bytes of data from this input stream into an
     * array of bytes. If <code>len</code> is not zero, the method blocks until
     * some input is available; otherwise, no bytes are read and <code>0</code>
     * is returned.
     * <p>
     * This method simply performs <code>in.read(b, off, len)</code> and returns
     * the result.
     * 
     * @param b
     *            the buffer into which the data is read.
     * @param off
     *            The start offset in the destination array <code>b</code>.
     * @param len
     *            the maximum number of bytes read.
     * @return the total number of bytes read into the buffer, or
     *         <code>-1</code> if there is no more data because the end of the
     *         stream has been reached.
     * @exception NullPointerException
     *                If <code>b</code> is <code>null</code>.
     * @exception IndexOutOfBoundsException
     *                If <code>off</code> is negative, <code>len</code> is
     *                negative, or <code>len</code> is greater than
     *                <code>b.length - off</code>
     * @exception IOException
     *                if an I/O error occurs.
     * @see java.io.FilterInputStream#in
     */
    @Override
    public int read(byte[] b, int off, int len) throws IOException {
        int res = super.read(b, off, len);
        if (res > 0) {
            count += res;
            checkLimit();
        }
        return res;
    }

    /**
     * Closes this input stream and releases any system resources associated
     * with the stream. This method simply performs <code>in.close()</code>.
     * 
     * @exception IOException
     *                if an I/O error occurs.
     * @see java.io.FilterInputStream#in
     */
    @Override
    public void close() throws IOException {
        super.close();
    }
}