libjava/java/io/FilterInputStream.java

   1 /* FilterInputStream.java -- Base class for 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>InputStream</code>
  50   * and simply redirects calls made to it to the subordinate InputStream
  51   * instead.  Subclasses of this class perform additional filtering
  52   * functions in addition to simply redirecting the call.
  53   * <p>
  54   * This class is not abstract.  However, since it only redirects calls
  55   * to a subordinate <code>InputStream</code> without adding any functionality
  56   * on top of it, this class should not be used directly.  Instead, various
  57   * subclasses of this class should be used.  This is enforced with a
  58   * protected constructor.  Do not try to hack around it.
  59   * <p>
  60   * When creating a subclass of <code>FilterInputStream</code>, override the
  61   * appropriate methods to implement the desired filtering.  However, note
  62   * that the <code>read(byte[])</code> method does not need to be overridden
  63   * as this class redirects calls to that method to
  64   * <code>read(byte[], int, int)</code> instead of to the subordinate
  65   * <code>InputStream read(byte[])</code> method.
  66   *
  67   * @author Aaron M. Renn (arenn@urbanophile.com)
  68   * @author Warren Levy <warrenl@cygnus.com>
  69   */
  70 public class FilterInputStream extends InputStream
  71 {
  72
  73 /*************************************************************************/
  74
  75 /*
  76  * Instance Variables
  77  */
  78
  79 /**
  80   * This is the subordinate <code>InputStream</code> to which method calls
  81   * are redirected
  82   */
  83 protected InputStream in;
  84
  85 /*************************************************************************/
  86
  87 /*
  88  * Constructors
  89  */
  90
  91 /**
  92   * Create a <code>FilterInputStream</code> with the specified subordinate
  93   * <code>InputStream</code>.
  94   *
  95   * @param in The subordinate <code>InputStream</code>
  96   */
  97 protected
  98 FilterInputStream(InputStream in)
  99 {
 100   this.in = in;
 101 }
 102
 103 /*************************************************************************/
 104
 105 /*
 106  * Instance Methods
 107  */
 108
 109 /**
 110   * Calls the <code>in.mark(int)</code> method.
 111   *
 112   * @param readlimit The parameter passed to <code>in.mark(int)</code>
 113   */
 114 public void
 115 mark(int readlimit)
 116 {
 117   in.mark(readlimit);
 118 }
 119
 120 /*************************************************************************/
 121
 122 /**
 123   * Calls the <code>in.markSupported()</code> method.
 124   *
 125   * @return <code>true</code> if mark/reset is supported, <code>false</code>
 126   *         otherwise
 127   */
 128 public boolean
 129 markSupported()
 130 {
 131   return(in.markSupported());
 132 }
 133
 134 /*************************************************************************/
 135
 136 /**
 137   * Calls the <code>in.reset()</code> method.
 138   *
 139   * @exception IOException If an error occurs
 140   */
 141 public void
 142 reset() throws IOException
 143 {
 144   in.reset();
 145 }
 146
 147 /*************************************************************************/
 148
 149 /**
 150   * Calls the <code>in.available()</code> method.
 151   *
 152   * @return The value returned from <code>in.available()</code>
 153   *
 154   * @exception IOException If an error occurs
 155   */
 156 public int
 157 available() throws IOException
 158 {
 159   return(in.available());
 160 }
 161
 162 /*************************************************************************/
 163
 164 /**
 165   * Calls the <code>in.skip(long)</code> method
 166   *
 167   * @param The requested number of bytes to skip.
 168   *
 169   * @return The value returned from <code>in.skip(long)</code>
 170   *
 171   * @exception IOException If an error occurs
 172   */
 173 public long
 174 skip(long num_bytes) throws IOException
 175 {
 176   return(in.skip(num_bytes));
 177 }
 178
 179 /*************************************************************************/
 180
 181 /**
 182   * Calls the <code>in.read()</code> method
 183   *
 184   * @return The value returned from <code>in.read()</code>
 185   *
 186   * @exception IOException If an error occurs
 187   */
 188 public int
 189 read() throws IOException
 190 {
 191   return(in.read());
 192 }
 193
 194 /*************************************************************************/
 195
 196 /**
 197   * Calls the <code>read(byte[], int, int)</code> overloaded method.  Note that
 198   * this method does not redirect its call directly to a corresponding
 199   * method in <code>in</code>.  This allows subclasses to override only the
 200   * three argument version of <code>read</code>.
 201   *
 202   * @param buf The buffer to read bytes into
 203   *
 204   * @return The value retured from <code>in.read(byte[], int, int)</code>
 205   *
 206   * @exception IOException If an error occurs
 207   */
 208 public int
 209 read(byte[] buf) throws IOException
 210 {
 211   return(read(buf, 0, buf.length));
 212 }
 213
 214 /*************************************************************************/
 215
 216 /**
 217   * Calls the <code>in.read(byte[], int, int)</code> method.
 218   *
 219   * @param buf The buffer to read bytes into
 220   * @param offset The index into the buffer to start storing bytes
 221   * @param len The maximum number of bytes to read.
 222   *
 223   * @return The value retured from <code>in.read(byte[], int, int)</code>
 224   *
 225   * @exception IOException If an error occurs
 226   */
 227 public int
 228 read(byte[] buf, int offset, int len) throws IOException
 229 {
 230   return(in.read(buf, offset, len));
 231 }
 232
 233 /*************************************************************************/
 234
 235 /**
 236   * This method closes the input stream by closing the input stream that
 237   * this object is filtering.  Future attempts to access this stream may
 238   * throw an exception.
 239   *
 240   * @exception IOException If an error occurs
 241   */
 242 public void
 243 close() throws IOException
 244 {
 245   in.close();
 246 }
 247
 248 } // class FilterInputStream