1 /* 2 * Copyright (c) 1994, 2010, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.io; 27 28 /** 29 * A <code>FilterInputStream</code> contains 30 * some other input stream, which it uses as 31 * its basic source of data, possibly transforming 32 * the data along the way or providing additional 33 * functionality. The class <code>FilterInputStream</code> 34 * itself simply overrides all methods of 35 * <code>InputStream</code> with versions that 36 * pass all requests to the contained input 37 * stream. Subclasses of <code>FilterInputStream</code> 38 * may further override some of these methods 39 * and may also provide additional methods 40 * and fields. 41 * 42 * @author Jonathan Payne 43 * @since JDK1.0 44 */ 45 public 46 class FilterInputStream extends InputStream { 47 /** 48 * The input stream to be filtered. 49 */ 50 protected volatile InputStream in; 51 52 /** 53 * Creates a <code>FilterInputStream</code> 54 * by assigning the argument <code>in</code> 55 * to the field <code>this.in</code> so as 56 * to remember it for later use. 57 * 58 * @param in the underlying input stream, or <code>null</code> if 59 * this instance is to be created without an underlying stream. 60 */ 61 protected FilterInputStream(InputStream in) { 62 this.in = in; 63 } 64 65 /** 66 * Reads the next byte of data from this input stream. The value 67 * byte is returned as an <code>int</code> in the range 68 * <code>0</code> to <code>255</code>. If no byte is available 69 * because the end of the stream has been reached, the value 70 * <code>-1</code> is returned. This method blocks until input data 71 * is available, the end of the stream is detected, or an exception 72 * is thrown. 73 * <p> 74 * This method 75 * simply performs <code>in.read()</code> and returns the result. 76 * 77 * @return the next byte of data, or <code>-1</code> if the end of the 78 * stream is reached. 79 * @exception IOException if an I/O error occurs. 80 * @see java.io.FilterInputStream#in 81 */ 82 public int read() throws IOException { 83 return in.read(); 84 } 85 86 /** 87 * Reads up to <code>byte.length</code> bytes of data from this 88 * input stream into an array of bytes. This method blocks until some 89 * input is available. 90 * <p> 91 * This method simply performs the call 92 * <code>read(b, 0, b.length)</code> and returns 93 * the result. It is important that it does 94 * <i>not</i> do <code>in.read(b)</code> instead; 95 * certain subclasses of <code>FilterInputStream</code> 96 * depend on the implementation strategy actually 97 * used. 98 * 99 * @param b the buffer into which the data is read. 100 * @return the total number of bytes read into the buffer, or 101 * <code>-1</code> if there is no more data because the end of 102 * the stream has been reached. 103 * @exception IOException if an I/O error occurs. 104 * @see java.io.FilterInputStream#read(byte[], int, int) 105 */ 106 public int read(byte b[]) throws IOException { 107 return read(b, 0, b.length); 108 } 109 110 /** 111 * Reads up to <code>len</code> bytes of data from this input stream 112 * into an array of bytes. If <code>len</code> is not zero, the method 113 * blocks until some input is available; otherwise, no 114 * bytes are read and <code>0</code> is returned. 115 * <p> 116 * This method simply performs <code>in.read(b, off, len)</code> 117 * and returns the result. 118 * 119 * @param b the buffer into which the data is read. 120 * @param off the start offset in the destination array <code>b</code> 121 * @param len the maximum number of bytes read. 122 * @return the total number of bytes read into the buffer, or 123 * <code>-1</code> if there is no more data because the end of 124 * the stream has been reached. 125 * @exception NullPointerException If <code>b</code> is <code>null</code>. 126 * @exception IndexOutOfBoundsException If <code>off</code> is negative, 127 * <code>len</code> is negative, or <code>len</code> is greater than 128 * <code>b.length - off</code> 129 * @exception IOException if an I/O error occurs. 130 * @see java.io.FilterInputStream#in 131 */ 132 public int read(byte b[], int off, int len) throws IOException { 133 return in.read(b, off, len); 134 } 135 136 /** 137 * Skips over and discards <code>n</code> bytes of data from the 138 * input stream. The <code>skip</code> method may, for a variety of 139 * reasons, end up skipping over some smaller number of bytes, 140 * possibly <code>0</code>. The actual number of bytes skipped is 141 * returned. 142 * <p> 143 * This method simply performs <code>in.skip(n)</code>. 144 * 145 * @param n the number of bytes to be skipped. 146 * @return the actual number of bytes skipped. 147 * @exception IOException if the stream does not support seek, 148 * or if some other I/O error occurs. 149 */ 150 public long skip(long n) throws IOException { 151 return in.skip(n); 152 } 153 154 /** 155 * Returns an estimate of the number of bytes that can be read (or 156 * skipped over) from this input stream without blocking by the next 157 * caller of a method for this input stream. The next caller might be 158 * the same thread or another thread. A single read or skip of this 159 * many bytes will not block, but may read or skip fewer bytes. 160 * <p> 161 * This method returns the result of {@link #in in}.available(). 162 * 163 * @return an estimate of the number of bytes that can be read (or skipped 164 * over) from this input stream without blocking. 165 * @exception IOException if an I/O error occurs. 166 */ 167 public int available() throws IOException { 168 return in.available(); 169 } 170 171 /** 172 * Closes this input stream and releases any system resources 173 * associated with the stream. 174 * This 175 * method simply performs <code>in.close()</code>. 176 * 177 * @exception IOException if an I/O error occurs. 178 * @see java.io.FilterInputStream#in 179 */ 180 public void close() throws IOException { 181 in.close(); 182 } 183 184 /** 185 * Marks the current position in this input stream. A subsequent 186 * call to the <code>reset</code> method repositions this stream at 187 * the last marked position so that subsequent reads re-read the same bytes. 188 * <p> 189 * The <code>readlimit</code> argument tells this input stream to 190 * allow that many bytes to be read before the mark position gets 191 * invalidated. 192 * <p> 193 * This method simply performs <code>in.mark(readlimit)</code>. 194 * 195 * @param readlimit the maximum limit of bytes that can be read before 196 * the mark position becomes invalid. 197 * @see java.io.FilterInputStream#in 198 * @see java.io.FilterInputStream#reset() 199 */ 200 public synchronized void mark(int readlimit) { 201 in.mark(readlimit); 202 } 203 204 /** 205 * Repositions this stream to the position at the time the 206 * <code>mark</code> method was last called on this input stream. 207 * <p> 208 * This method 209 * simply performs <code>in.reset()</code>. 210 * <p> 211 * Stream marks are intended to be used in 212 * situations where you need to read ahead a little to see what's in 213 * the stream. Often this is most easily done by invoking some 214 * general parser. If the stream is of the type handled by the 215 * parse, it just chugs along happily. If the stream is not of 216 * that type, the parser should toss an exception when it fails. 217 * If this happens within readlimit bytes, it allows the outer 218 * code to reset the stream and try another parser. 219 * 220 * @exception IOException if the stream has not been marked or if the 221 * mark has been invalidated. 222 * @see java.io.FilterInputStream#in 223 * @see java.io.FilterInputStream#mark(int) 224 */ 225 public synchronized void reset() throws IOException { 226 in.reset(); 227 } 228 229 /** 230 * Tests if this input stream supports the <code>mark</code> 231 * and <code>reset</code> methods. 232 * This method 233 * simply performs <code>in.markSupported()</code>. 234 * 235 * @return <code>true</code> if this stream type supports the 236 * <code>mark</code> and <code>reset</code> method; 237 * <code>false</code> otherwise. 238 * @see java.io.FilterInputStream#in 239 * @see java.io.InputStream#mark(int) 240 * @see java.io.InputStream#reset() 241 */ 242 public boolean markSupported() { 243 return in.markSupported(); 244 } 245 } 246
