001 /* FilterInputStream.java -- Base class for classes that filter input
002 Copyright (C) 1998, 1999, 2001, 2005 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038
039 package 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>InputStream</code>
050 * and simply redirects calls made to it to the subordinate InputStream
051 * instead. Subclasses of this class perform additional filtering
052 * functions in addition to simply redirecting the call.
053 * <p>
054 * This class is not abstract. However, since it only redirects calls
055 * to a subordinate <code>InputStream</code> without adding any functionality
056 * on top of it, this class should not be used directly. Instead, various
057 * subclasses of this class should be used. This is enforced with a
058 * protected constructor. Do not try to hack around it.
059 * <p>
060 * When creating a subclass of <code>FilterInputStream</code>, override the
061 * appropriate methods to implement the desired filtering. However, note
062 * that the <code>read(byte[])</code> method does not need to be overridden
063 * as this class redirects calls to that method to
064 * <code>read(byte[], int, int)</code> instead of to the subordinate
065 * <code>InputStream read(byte[])</code> method.
066 *
067 * @author Aaron M. Renn (arenn@urbanophile.com)
068 * @author Warren Levy (warrenl@cygnus.com)
069 */
070 public class FilterInputStream extends InputStream
071 {
072 /**
073 * This is the subordinate <code>InputStream</code> to which method calls
074 * are redirected
075 */
076 protected InputStream in;
077
078 /**
079 * Create a <code>FilterInputStream</code> with the specified subordinate
080 * <code>InputStream</code>.
081 *
082 * @param in The subordinate <code>InputStream</code>
083 */
084 protected FilterInputStream(InputStream in)
085 {
086 this.in = in;
087 }
088
089 /**
090 * Calls the <code>in.mark(int)</code> method.
091 *
092 * @param readlimit The parameter passed to <code>in.mark(int)</code>
093 */
094 public void mark(int readlimit)
095 {
096 in.mark(readlimit);
097 }
098
099 /**
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 }