Source for java.io.FilterInputStream

   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., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 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: }