/*

 * Copyright (c) 1994, 2019, Oracle and/or its affiliates. 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.  Oracle designates this

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

 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package java.io;

/**

 * A {@code FilterInputStream} 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}

 * itself simply overrides all  methods of

 * {@code InputStream} with versions that

 * pass all requests to the contained  input

 * stream. Subclasses of {@code FilterInputStream}

 * may further override some of  these methods

 * and may also provide additional methods

 * and fields.

 *

 * @author  Jonathan Payne

 * @since   1.0

 */

public

class FilterInputStream extends InputStream {

    /**

     * The input stream to be filtered.

     */

    protected volatile InputStream in;

    /**

     * Creates a {@code FilterInputStream}

     * by assigning the  argument {@code in}

     * to the field {@code this.in} so as

     * to remember it for later use.

     *

     * @param   in   the underlying input stream, or {@code null} 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} in the range

     * {@code 0} to {@code 255}. If no byte is available

     * because the end of the stream has been reached, the value

     * {@code -1} 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()} and returns the result.

     *

     * @return     the next byte of data, or {@code -1} if the end of the

     *             stream is reached.

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

     * @see        java.io.FilterInputStream#in

     */

    public int read() throws IOException {

        return in.read();

    }

    /**

     * Reads up to {@code b.length} 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)} and returns

     * the  result. It is important that it does

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

     * certain subclasses of  {@code FilterInputStream}

     * 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} if there is no more data because the end of

     *             the stream has been reached.

     * @throws     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} bytes of data from this input stream

     * into an array of bytes. If {@code len} is not zero, the method

     * blocks until some input is available; otherwise, no

     * bytes are read and {@code 0} is returned.

     * <p>

     * This method simply performs {@code in.read(b, off, len)}

     * 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}

     * @param      len   the maximum number of bytes read.

     * @return     the total number of bytes read into the buffer, or

     *             {@code -1} if there is no more data because the end of

     *             the stream has been reached.

     * @throws     NullPointerException If {@code b} is {@code null}.

     * @throws     IndexOutOfBoundsException If {@code off} is negative,

     *             {@code len} is negative, or {@code len} is greater than

     *             {@code b.length - off}

     * @throws     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);

    }

    /**

     * Skips over and discards {@code n} bytes of data from the

     * input stream. The {@code skip} method may, for a variety of

     * reasons, end up skipping over some smaller number of bytes,

     * possibly {@code 0}. The actual number of bytes skipped is

     * returned.

     * <p>

     * This method simply performs {@code in.skip(n)}.

     *

     * @param      n   the number of bytes to be skipped.

     * @return     the actual number of bytes skipped.

     * @throws     IOException  if {@code in.skip(n)} throws an IOException.

     */

    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.

     * @throws     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()}.

     *

     * @throws     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} method repositions this stream at

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

     * <p>

     * The {@code readlimit} 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)}.

     *

     * @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} method was last called on this input stream.

     * <p>

     * This method

     * simply performs {@code in.reset()}.

     * <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.

     *

     * @throws     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}

     * and {@code reset} methods.

     * This method

     * simply performs {@code in.markSupported()}.

     *

     * @return  {@code true} if this stream type supports the

     *          {@code mark} and {@code reset} method;

     *          {@code false} otherwise.

     * @see     java.io.FilterInputStream#in

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

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

     */

    public boolean markSupported() {

        return in.markSupported();

    }

}