001/* FilterReader.java -- Base class for char stream classes that filter input
002   Copyright (C) 1998, 1999, 2001, 2003, 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>Reader</code>
050  * and simply redirects calls made to it to the subordinate Reader
051  * instead.  Subclasses of this class perform additional filtering
052  * functions in addition to simply redirecting the call.
053  * <p>
054  * When creating a subclass of <code>FilterReader</code>, override the
055  * appropriate methods to implement the desired filtering.  However, note
056  * that the <code>read(char[])</code> method does not need to be overridden
057  * as this class redirects calls to that method to 
058  * <code>read(yte[], int, int)</code> instead of to the subordinate
059  * <code>Reader} read(yte[])</code> method.
060  *
061  * @author Aaron M. Renn (arenn@urbanophile.com)
062  * @author Warren Levy (warrenl@cygnus.com)
063  */
064public abstract class FilterReader extends Reader
065{
066  /**
067    * This is the subordinate <code>Reader</code> to which method calls
068    * are redirected
069    */
070  protected Reader in;
071
072  /**
073    * Create a <code>FilterReader</code> with the specified subordinate
074    * <code>Reader</code>.
075    * The <code>lock</code> of the new <code>FilterReader</code> will be set
076    * to <code>in.lock</code>.
077    *
078    * @param in The subordinate <code>Reader</code>
079    */
080  protected FilterReader(Reader in)
081  {
082    super(in.lock);
083    this.in = in;
084  }
085
086  /**
087    * Calls the <code>in.mark(int)</code> method.
088    *
089    * @param readlimit The parameter passed to <code>in.mark(int)</code>
090    *
091    * @exception IOException If an error occurs
092    */
093  public void mark(int readlimit) throws IOException
094  {
095    in.mark(readlimit);
096  }
097
098  /**
099    * Calls the <code>in.markSupported()</code> method.
100    *
101    * @return <code>true</code> if mark/reset is supported, 
102    * <code>false</code> otherwise
103    */
104  public boolean markSupported()
105  {
106    return(in.markSupported());
107  }
108
109  /**
110    * Calls the <code>in.reset()</code> method.
111    *
112    * @exception IOException If an error occurs
113    */
114  public void reset() throws IOException
115  {
116    in.reset();
117  }
118
119  /**
120    * Calls the <code>in.read()</code> method.
121    *
122    * @return The value returned from <code>in.available()</code>
123    *
124    * @exception IOException If an error occurs
125    */
126  public boolean ready() throws IOException
127  {
128    return(in.ready());
129  }
130
131  /**
132    * Calls the <code>in.skip(long)</code> method
133    *
134    * @param num_chars The requested number of chars to skip. 
135    *
136    * @return The value returned from <code>in.skip(long)</code>
137    *
138    * @exception IOException If an error occurs
139    */
140  public long skip(long num_chars) throws IOException
141  {
142    return(in.skip(num_chars));
143  }
144
145  /**
146    * Calls the <code>in.read()</code> method
147    *
148    * @return The value returned from <code>in.read()</code>
149    *
150    * @exception IOException If an error occurs
151    */
152  public int read() throws IOException
153  {
154    return(in.read());
155  }
156
157  /**
158    * Calls the <code>in.read(char[], int, int)</code> method.
159    *
160    * @param buf The buffer to read chars into
161    * @param offset The index into the buffer to start storing chars
162    * @param len The maximum number of chars to read.
163    *
164    * @return The value retured from <code>in.read(char[], int, int)</code>
165    *
166    * @exception IOException If an error occurs
167    */
168  public int read(char[] buf, int offset, int len) throws IOException
169  {
170    return(in.read(buf, offset, len));
171  }
172
173  /**
174    * This method closes the stream by calling the <code>close()</code> method
175    * of the underlying stream.
176    *
177    * @exception IOException If an error occurs
178    */
179  public void close() throws IOException
180  {
181    in.close();
182  }
183
184} // class FilterReader
185