001/* FilterInputStream.java -- Base class for classes that filter input 002 Copyright (C) 1998, 1999, 2001, 2005 Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038 039package 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 */ 070public 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}