/*

 * Copyright 1994-2006 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package java.io;

/**

 * A <code>FilterInputStream</code> contains

 * some other input stream, which it uses as

 * its  basic source of data, possibly transforming

 * the data along the way or providing  additional

 * functionality. The class <code>FilterInputStream</code>

 * itself simply overrides all  methods of

 * <code>InputStream</code> with versions that

 * pass all requests to the contained  input

 * stream. Subclasses of <code>FilterInputStream</code>

 * may further override some of  these methods

 * and may also provide additional methods

 * and fields.

 *

 * @author  Jonathan Payne

 * @since   JDK1.0

 */

public

class FilterInputStream extends InputStream {

    /**

     * The input stream to be filtered.

     */

    protected volatile InputStream in;

    /**

     * Creates a <code>FilterInputStream</code>

     * by assigning the  argument <code>in</code>

     * to the field <code>this.in</code> so as

     * to remember it for later use.

     *

     * @param   in   the underlying input stream, or <code>null</code> if

     *          this instance is to be created without an underlying stream.

     */

    protected FilterInputStream(InputStream in) {

        this.in = in;

    }

    /**

     * 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

     */

    public int read() throws IOException {

        return in.read();

    }

    /**

     * Reads up to <code>byte.length</code> bytes of data from this

     * input stream into an array of bytes. This method blocks until some

     * input is available.

     * <p>

     * This method simply performs the call

     * <code>read(b, 0, b.length)</code> and returns

     * the  result. It is important that it does

     * <i>not</i> do <code>in.read(b)</code> instead;

     * certain subclasses of  <code>FilterInputStream</code>

     * depend on the implementation strategy actually

     * used.

     *

     * @param      b   the buffer into which the data is 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  IOException  if an I/O error occurs.

     * @see        java.io.FilterInputStream#read(byte[], int, int)

     */

    public int read(byte b[]) throws IOException {

        return read(b, 0, b.length);

    }

    /**

     * 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

     */

    public int read(byte b[], int off, int len) throws IOException {

        return in.read(b, off, len);

    }

    /**

     * {@inheritDoc}

     * <p>

     * This method simply performs <code>in.skip(n)</code>.

     */

    public long skip(long n) throws IOException {

        return in.skip(n);

    }

    /**

     * Returns an estimate of the number of bytes that can be read (or

     * skipped over) from this input stream without blocking by the next

     * caller of a method for this input stream. The next caller might be

     * the same thread or another thread.  A single read or skip of this

     * many bytes will not block, but may read or skip fewer bytes.

     * <p>

     * This method returns the result of {@link #in in}.available().

     *

     * @return     an estimate of the number of bytes that can be read (or skipped

     *             over) from this input stream without blocking.

     * @exception  IOException  if an I/O error occurs.

     */

    public int available() throws IOException {

        return in.available();

    }

    /**

     * 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

     */

    public void close() throws IOException {

        in.close();

    }

    /**

     * Marks the current position in this input stream. A subsequent

     * call to the <code>reset</code> method repositions this stream at

     * the last marked position so that subsequent reads re-read the same bytes.

     * <p>

     * The <code>readlimit</code> argument tells this input stream to

     * allow that many bytes to be read before the mark position gets

     * invalidated.

     * <p>

     * This method simply performs <code>in.mark(readlimit)</code>.

     *

     * @param   readlimit   the maximum limit of bytes that can be read before

     *                      the mark position becomes invalid.

     * @see     java.io.FilterInputStream#in

     * @see     java.io.FilterInputStream#reset()

     */

    public synchronized void mark(int readlimit) {

        in.mark(readlimit);

    }

    /**

     * Repositions this stream to the position at the time the

     * <code>mark</code> method was last called on this input stream.

     * <p>

     * This method

     * simply performs <code>in.reset()</code>.

     * <p>

     * Stream marks are intended to be used in

     * situations where you need to read ahead a little to see what's in

     * the stream. Often this is most easily done by invoking some

     * general parser. If the stream is of the type handled by the

     * parse, it just chugs along happily. If the stream is not of

     * that type, the parser should toss an exception when it fails.

     * If this happens within readlimit bytes, it allows the outer

     * code to reset the stream and try another parser.

     *

     * @exception  IOException  if the stream has not been marked or if the

     *               mark has been invalidated.

     * @see        java.io.FilterInputStream#in

     * @see        java.io.FilterInputStream#mark(int)

     */

    public synchronized void reset() throws IOException {

        in.reset();

    }

    /**

     * Tests if this input stream supports the <code>mark</code>

     * and <code>reset</code> methods.

     * This method

     * simply performs <code>in.markSupported()</code>.

     *

     * @return  <code>true</code> if this stream type supports the

     *          <code>mark</code> and <code>reset</code> method;

     *          <code>false</code> otherwise.

     * @see     java.io.FilterInputStream#in

     * @see     java.io.InputStream#mark(int)

     * @see     java.io.InputStream#reset()

     */

    public boolean markSupported() {

        return in.markSupported();

    }

}