001/* FilterInputStream.java -- Base class for classes that filter input
002   Copyright (C) 1998, 1999, 2001, 2005  Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package java.io;
040
041/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
042 * "The Java Language Specification", ISBN 0-201-63451-1
043 * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
044 * Status:  Believed complete and correct.
045 */
046
047/**
048  * This is the common superclass of all standard classes that filter
049  * input.  It acts as a layer on top of an underlying <code>InputStream</code>
050  * and simply redirects calls made to it to the subordinate InputStream
051  * instead.  Subclasses of this class perform additional filtering
052  * functions in addition to simply redirecting the call.
053  * <p>
054  * This class is not abstract.  However, since it only redirects calls
055  * to a subordinate <code>InputStream</code> without adding any functionality
056  * on top of it, this class should not be used directly.  Instead, various
057  * subclasses of this class should be used.  This is enforced with a
058  * protected constructor.  Do not try to hack around it.
059  * <p>
060  * When creating a subclass of <code>FilterInputStream</code>, override the
061  * appropriate methods to implement the desired filtering.  However, note
062  * that the <code>read(byte[])</code> method does not need to be overridden
063  * as this class redirects calls to that method to
064  * <code>read(byte[], int, int)</code> instead of to the subordinate
065  * <code>InputStream read(byte[])</code> method.
066  *
067  * @author Aaron M. Renn (arenn@urbanophile.com)
068  * @author Warren Levy (warrenl@cygnus.com)
069  */
070public class FilterInputStream extends InputStream
071{
072  /**
073    * This is the subordinate <code>InputStream</code> to which method calls
074    * are redirected
075    */
076  protected InputStream in;
077
078  /**
079    * Create a <code>FilterInputStream</code> with the specified subordinate
080    * <code>InputStream</code>.
081    *
082    * @param in The subordinate <code>InputStream</code>
083    */
084  protected FilterInputStream(InputStream in)
085  {
086    this.in = in;
087  }
088
089  /**
090    * Calls the <code>in.mark(int)</code> method.
091    *
092    * @param readlimit The parameter passed to <code>in.mark(int)</code>
093    */
094  public void mark(int readlimit)
095  {
096    in.mark(readlimit);
097  }
098
099  /**
100    * Calls the <code>in.markSupported()</code> method.
101    *
102    * @return <code>true</code> if mark/reset is supported, <code>false</code>
103    *         otherwise
104    */
105  public boolean markSupported()
106  {
107    return in.markSupported();
108  }
109
110  /**
111    * Calls the <code>in.reset()</code> method.
112    *
113    * @exception IOException If an error occurs
114    */
115  public void reset() throws IOException
116  {
117    in.reset();
118  }
119
120  /**
121    * Calls the <code>in.available()</code> method.
122    *
123    * @return The value returned from <code>in.available()</code>
124    *
125    * @exception IOException If an error occurs
126    */
127  public int available() throws IOException
128  {
129    return in.available();
130  }
131
132  /**
133    * Calls the <code>in.skip(long)</code> method
134    *
135    * @param numBytes The requested number of bytes to skip.
136    *
137    * @return The value returned from <code>in.skip(long)</code>
138    *
139    * @exception IOException If an error occurs
140    */
141  public long skip(long numBytes) throws IOException
142  {
143    return in.skip(numBytes);
144  }
145
146  /**
147    * Calls the <code>in.read()</code> method
148    *
149    * @return The value returned from <code>in.read()</code>
150    *
151    * @exception IOException If an error occurs
152    */
153  public int read() throws IOException
154  {
155    return in.read();
156  }
157
158  /**
159    * Calls the <code>read(byte[], int, int)</code> overloaded method.
160    * Note that
161    * this method does not redirect its call directly to a corresponding
162    * method in <code>in</code>.  This allows subclasses to override only the
163    * three argument version of <code>read</code>.
164    *
165    * @param buf The buffer to read bytes into
166    *
167    * @return The value retured from <code>in.read(byte[], int, int)</code>
168    *
169    * @exception IOException If an error occurs
170    */
171  public int read(byte[] buf) throws IOException
172  {
173    return read(buf, 0, buf.length);
174  }
175
176  /**
177    * Calls the <code>in.read(byte[], int, int)</code> method.
178    *
179    * @param buf The buffer to read bytes into
180    * @param offset The index into the buffer to start storing bytes
181    * @param len The maximum number of bytes to read.
182    *
183    * @return The value retured from <code>in.read(byte[], int, int)</code>
184    *
185    * @exception IOException If an error occurs
186    */
187  public int read(byte[] buf, int offset, int len) throws IOException
188  {
189    return in.read(buf, offset, len);
190  }
191
192  /**
193    * This method closes the input stream by closing the input stream that
194    * this object is filtering.  Future attempts to access this stream may
195    * throw an exception.
196    *
197    * @exception IOException If an error occurs
198    */
199  public void close() throws IOException
200  {
201    in.close();
202  }
203}