/*

  * Copyright (c) 1994, 2010, 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</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);

     }

     /**

      * Skips over and discards <code>n</code> bytes of data from the

      * input stream. The <code>skip</code> method may, for a variety of

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

      * possibly <code>0</code>. The actual number of bytes skipped is

      * returned.

      * <p>

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

      *

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

      * @return     the actual number of bytes skipped.

      * @exception  IOException  if the stream does not support seek,

      *                          or if some other I/O error occurs.

      */

     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();

     }

 }