libjava/java/io/FilterReader.java

   1 /* FilterReader.java -- Base class for char stream classes that filter input
   2    Copyright (C) 1998, 1999, 2001 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package java.io;
  40
  41 /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
  42  * "The Java Language Specification", ISBN 0-201-63451-1
  43  * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
  44  * Status:  Believed complete and correct.
  45  */
  46
  47 /**
  48   * This is the common superclass of all standard classes that filter
  49   * input.  It acts as a layer on top of an underlying <code>Reader</code>
  50   * and simply redirects calls made to it to the subordinate Reader
  51   * instead.  Subclasses of this class perform additional filtering
  52   * functions in addition to simply redirecting the call.
  53   * <p>
  54   * When creating a subclass of <code>FilterReader</code>, override the
  55   * appropriate methods to implement the desired filtering.  However, note
  56   * that the <code>read(char[])</code> method does not need to be overridden
  57   * as this class redirects calls to that method to
  58   * <code>read(yte[], int, int)</code> instead of to the subordinate
  59   * <code>Reader} read(yte[])</code> method.
  60   *
  61   * @author Aaron M. Renn (arenn@urbanophile.com)
  62   * @author Warren Levy <warrenl@cygnus.com>
  63   */
  64 public abstract class FilterReader extends Reader
  65 {
  66
  67 /*************************************************************************/
  68
  69 /*
  70  * Instance Variables
  71  */
  72
  73 /**
  74   * This is the subordinate <code>Reader</code> to which method calls
  75   * are redirected
  76   */
  77 protected Reader in;
  78
  79 /*************************************************************************/
  80
  81 /*
  82  * Constructors
  83  */
  84
  85 /**
  86   * Create a <code>FilterReader</code> with the specified subordinate
  87   * <code>Reader</code>.
  88   * The <code>lock</code> of the new <code>FilterReader</code> will be set
  89   * to <code>in.lock</code>.
  90   *
  91   * @param in The subordinate <code>Reader</code>
  92   */
  93 protected
  94 FilterReader(Reader in)
  95 {
  96   super(in.lock);
  97   this.in = in;
  98 }
  99
 100 /*************************************************************************/
 101
 102 /*
 103  * Instance Methods
 104  */
 105
 106 /**
 107   * Calls the <code>in.mark(int)</code> method.
 108   *
 109   * @param readlimit The parameter passed to <code>in.mark(int)</code>
 110   *
 111   * @exception IOException If an error occurs
 112   */
 113 public void
 114 mark(int readlimit) throws IOException
 115 {
 116   in.mark(readlimit);
 117 }
 118
 119 /*************************************************************************/
 120
 121 /**
 122   * Calls the <code>in.markSupported()</code> method.
 123   *
 124   * @return <code>true</code> if mark/reset is supported, <code>false</code> otherwise
 125   */
 126 public boolean
 127 markSupported()
 128 {
 129   return(in.markSupported());
 130 }
 131
 132 /*************************************************************************/
 133
 134 /**
 135   * Calls the <code>in.reset()</code> method.
 136   *
 137   * @exception IOException If an error occurs
 138   */
 139 public void
 140 reset() throws IOException
 141 {
 142   in.reset();
 143 }
 144
 145 /*************************************************************************/
 146
 147 /**
 148   * Calls the <code>in.read()</code> method.
 149   *
 150   * @return The value returned from <code>in.available()</code>
 151   *
 152   * @exception IOException If an error occurs
 153   */
 154 public boolean
 155 ready() throws IOException
 156 {
 157   return(in.ready());
 158 }
 159
 160 /*************************************************************************/
 161
 162 /**
 163   * Calls the <code>in.skip(long)</code> method
 164   *
 165   * @param The requested number of chars to skip.
 166   *
 167   * @return The value returned from <code>in.skip(long)</code>
 168   *
 169   * @exception IOException If an error occurs
 170   */
 171 public long
 172 skip(long num_chars) throws IOException
 173 {
 174   return(in.skip(num_chars));
 175 }
 176
 177 /*************************************************************************/
 178
 179 /**
 180   * Calls the <code>in.read()</code> method
 181   *
 182   * @return The value returned from <code>in.read()</code>
 183   *
 184   * @exception IOException If an error occurs
 185   */
 186 public int
 187 read() throws IOException
 188 {
 189   return(in.read());
 190 }
 191
 192 /*************************************************************************/
 193
 194 /**
 195   * Calls the <code>in.read(char[], int, int)</code> method.
 196   *
 197   * @param buf The buffer to read chars into
 198   * @param offset The index into the buffer to start storing chars
 199   * @param len The maximum number of chars to read.
 200   *
 201   * @return The value retured from <code>in.read(char[], int, int)</code>
 202   *
 203   * @exception IOException If an error occurs
 204   */
 205 public int
 206 read(char[] buf, int offset, int len) throws IOException
 207 {
 208   return(in.read(buf, offset, len));
 209 }
 210
 211 /*************************************************************************/
 212
 213 /**
 214   * This method closes the stream by calling the <code>close()</code> method
 215   * of the underlying stream.
 216   *
 217   * @exception IOException If an error occurs
 218   */
 219 public void
 220 close() throws IOException
 221 {
 222   in.close();
 223 }
 224
 225 } // class FilterReader