libjava/java/io/FilterInputStream.java

   1 /* FilterInputStream.java -- Base class for classes that filter input
   2    Copyright (C) 1998, 1999, 2001, 2005  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     * This is the subordinate <code>InputStream</code> to which method calls
  74     * are redirected
  75     */
  76   protected InputStream in;
  77
  78   /**
  79     * Create a <code>FilterInputStream</code> with the specified subordinate
  80     * <code>InputStream</code>.
  81     *
  82     * @param in The subordinate <code>InputStream</code>
  83     */
  84   protected FilterInputStream(InputStream in)
  85   {
  86     this.in = in;
  87   }
  88
  89   /**
  90     * Calls the <code>in.mark(int)</code> method.
  91     *
  92     * @param readlimit The parameter passed to <code>in.mark(int)</code>
  93     */
  94   public void mark(int readlimit)
  95   {
  96     in.mark(readlimit);
  97   }
  98
  99   /**
 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 }