FilterInputStream.java

/* FilterInputStream.java -- Base class for classes that filter input
   Copyright (C) 1998, 1999, 2001, 2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
 
GNU Classpath 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 for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */


package java.io;

/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
 * "The Java Language Specification", ISBN 0-201-63451-1
 * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
 * Status:  Believed complete and correct.
 */

/**
  * This is the common superclass of all standard classes that filter 
  * input.  It acts as a layer on top of an underlying <code>InputStream</code>
  * and simply redirects calls made to it to the subordinate InputStream
  * instead.  Subclasses of this class perform additional filtering
  * functions in addition to simply redirecting the call.
  * <p>
  * This class is not abstract.  However, since it only redirects calls
  * to a subordinate <code>InputStream</code> without adding any functionality
  * on top of it, this class should not be used directly.  Instead, various
  * subclasses of this class should be used.  This is enforced with a
  * protected constructor.  Do not try to hack around it.
  * <p>
  * When creating a subclass of <code>FilterInputStream</code>, override the
  * appropriate methods to implement the desired filtering.  However, note
  * that the <code>read(byte[])</code> method does not need to be overridden
  * as this class redirects calls to that method to 
  * <code>read(byte[], int, int)</code> instead of to the subordinate
  * <code>InputStream read(byte[])</code> method.
  *
  * @author Aaron M. Renn (arenn@urbanophile.com)
  * @author Warren Levy (warrenl@cygnus.com)
  */
public class FilterInputStream extends InputStream
{
  /**
    * This is the subordinate <code>InputStream</code> to which method calls
    * are redirected
    */
  protected InputStream in;

  /**
    * Create a <code>FilterInputStream</code> with the specified subordinate
    * <code>InputStream</code>.
    *
    * @param in The subordinate <code>InputStream</code>
    */
  protected FilterInputStream(InputStream in)
  {
    this.in = in;
  }

  /**
    * Calls the <code>in.mark(int)</code> method.
    *
    * @param readlimit The parameter passed to <code>in.mark(int)</code>
    */
  public void mark(int readlimit)
  {
    in.mark(readlimit);
  }

  /**
    * Calls the <code>in.markSupported()</code> method.
    *
    * @return <code>true</code> if mark/reset is supported, <code>false</code>
    *         otherwise
    */
  public boolean markSupported()
  {
    return in.markSupported();
  }

  /**
    * Calls the <code>in.reset()</code> method.
    *
    * @exception IOException If an error occurs
    */
  public void reset() throws IOException
  {
    in.reset();
  }

  /**
    * Calls the <code>in.available()</code> method.
    *
    * @return The value returned from <code>in.available()</code>
    *
    * @exception IOException If an error occurs
    */
  public int available() throws IOException
  {
    return in.available();
  }

  /**
    * Calls the <code>in.skip(long)</code> method
    *
    * @param numBytes The requested number of bytes to skip. 
    *
    * @return The value returned from <code>in.skip(long)</code>
    *
    * @exception IOException If an error occurs
    */
  public long skip(long numBytes) throws IOException
  {
    return in.skip(numBytes);
  }

  /**
    * Calls the <code>in.read()</code> method
    *
    * @return The value returned from <code>in.read()</code>
    *
    * @exception IOException If an error occurs
    */
  public int read() throws IOException
  {
    return in.read();
  }

  /**
    * Calls the <code>read(byte[], int, int)</code> overloaded method.  
    * Note that 
    * this method does not redirect its call directly to a corresponding
    * method in <code>in</code>.  This allows subclasses to override only the
    * three argument version of <code>read</code>.
    *
    * @param buf The buffer to read bytes into
    *
    * @return The value retured from <code>in.read(byte[], int, int)</code>
    *
    * @exception IOException If an error occurs
    */
  public int read(byte[] buf) throws IOException
  {
    return read(buf, 0, buf.length);
  }

  /**
    * Calls the <code>in.read(byte[], int, int)</code> method.
    *
    * @param buf The buffer to read bytes into
    * @param offset The index into the buffer to start storing bytes
    * @param len The maximum number of bytes to read.
    *
    * @return The value retured from <code>in.read(byte[], int, int)</code>
    *
    * @exception IOException If an error occurs
    */
  public int read(byte[] buf, int offset, int len) throws IOException
  {
    return in.read(buf, offset, len);
  }

  /**
    * This method closes the input stream by closing the input stream that
    * this object is filtering.  Future attempts to access this stream may
    * throw an exception.
    * 
    * @exception IOException If an error occurs
    */
  public void close() throws IOException
  {
    in.close();
  }
}