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| 1 | /* | ||
| 2 | * Copyright (c) 1994, 2006, 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 | * This abstract class is the superclass of all classes representing | ||
| 30 | * an input stream of bytes. | ||
| 31 | * | ||
| 32 | * <p> Applications that need to define a subclass of <code>InputStream</code> | ||
| 33 | * must always provide a method that returns the next byte of input. | ||
| 34 | * | ||
| 35 | * @author Arthur van Hoff | ||
| 36 | * @see java.io.BufferedInputStream | ||
| 37 | * @see java.io.ByteArrayInputStream | ||
| 38 | * @see java.io.DataInputStream | ||
| 39 | * @see java.io.FilterInputStream | ||
| 40 | * @see java.io.InputStream#read() | ||
| 41 | * @see java.io.OutputStream | ||
| 42 | * @see java.io.PushbackInputStream | ||
| 43 | * @since JDK1.0 | ||
| 44 | */ | ||
| 45 | public abstract class InputStream implements Closeable { | ||
| 46 | |||
| 47 | // SKIP_BUFFER_SIZE is used to determine the size of skipBuffer | ||
| 48 | private static final int SKIP_BUFFER_SIZE = 2048; | ||
| 49 | // skipBuffer is initialized in skip(long), if needed. | ||
| 50 | private static byte[] skipBuffer; | ||
| 51 | |||
| 52 | /** | ||
| 53 | * Reads the next byte of data from the input stream. The value byte is | ||
| 54 | * returned as an <code>int</code> in the range <code>0</code> to | ||
| 55 | * <code>255</code>. If no byte is available because the end of the stream | ||
| 56 | * has been reached, the value <code>-1</code> is returned. This method | ||
| 57 | * blocks until input data is available, the end of the stream is detected, | ||
| 58 | * or an exception is thrown. | ||
| 59 | * | ||
| 60 | * <p> A subclass must provide an implementation of this method. | ||
| 61 | * | ||
| 62 | * @return the next byte of data, or <code>-1</code> if the end of the | ||
| 63 | * stream is reached. | ||
| 64 | * @exception IOException if an I/O error occurs. | ||
| 65 | */ | ||
| 66 | public abstract int read() throws IOException; | ||
| 67 | |||
| 68 | /** | ||
| 69 | * Reads some number of bytes from the input stream and stores them into | ||
| 70 | * the buffer array <code>b</code>. The number of bytes actually read is | ||
| 71 | * returned as an integer. This method blocks until input data is | ||
| 72 | * available, end of file is detected, or an exception is thrown. | ||
| 73 | * | ||
| 74 | * <p> If the length of <code>b</code> is zero, then no bytes are read and | ||
| 75 | * <code>0</code> is returned; otherwise, there is an attempt to read at | ||
| 76 | * least one byte. If no byte is available because the stream is at the | ||
| 77 | * end of the file, the value <code>-1</code> is returned; otherwise, at | ||
| 78 | * least one byte is read and stored into <code>b</code>. | ||
| 79 | * | ||
| 80 | * <p> The first byte read is stored into element <code>b[0]</code>, the | ||
| 81 | * next one into <code>b[1]</code>, and so on. The number of bytes read is, | ||
| 82 | * at most, equal to the length of <code>b</code>. Let <i>k</i> be the | ||
| 83 | * number of bytes actually read; these bytes will be stored in elements | ||
| 84 | * <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>, | ||
| 85 | * leaving elements <code>b[</code><i>k</i><code>]</code> through | ||
| 86 | * <code>b[b.length-1]</code> unaffected. | ||
| 87 | * | ||
| 88 | * <p> The <code>read(b)</code> method for class <code>InputStream</code> | ||
| 89 | * has the same effect as: <pre><code> read(b, 0, b.length) </code></pre> | ||
| 90 | * | ||
| 91 | * @param b the buffer into which the data is read. | ||
| 92 | * @return the total number of bytes read into the buffer, or | ||
| 93 | * <code>-1</code> if there is no more data because the end of | ||
| 94 | * the stream has been reached. | ||
| 95 | * @exception IOException If the first byte cannot be read for any reason | ||
| 96 | * other than the end of the file, if the input stream has been closed, or | ||
| 97 | * if some other I/O error occurs. | ||
| 98 | * @exception NullPointerException if <code>b</code> is <code>null</code>. | ||
| 99 | * @see java.io.InputStream#read(byte[], int, int) | ||
| 100 | */ | ||
| 101 | public int read(byte b[]) throws IOException { | ||
| 102 | return read(b, 0, b.length); | ||
| 103 | } | ||
| 104 | |||
| 105 | /** | ||
| 106 | * Reads up to <code>len</code> bytes of data from the input stream into | ||
| 107 | * an array of bytes. An attempt is made to read as many as | ||
| 108 | * <code>len</code> bytes, but a smaller number may be read. | ||
| 109 | * The number of bytes actually read is returned as an integer. | ||
| 110 | * | ||
| 111 | * <p> This method blocks until input data is available, end of file is | ||
| 112 | * detected, or an exception is thrown. | ||
| 113 | * | ||
| 114 | * <p> If <code>len</code> is zero, then no bytes are read and | ||
| 115 | * <code>0</code> is returned; otherwise, there is an attempt to read at | ||
| 116 | * least one byte. If no byte is available because the stream is at end of | ||
| 117 | * file, the value <code>-1</code> is returned; otherwise, at least one | ||
| 118 | * byte is read and stored into <code>b</code>. | ||
| 119 | * | ||
| 120 | * <p> The first byte read is stored into element <code>b[off]</code>, the | ||
| 121 | * next one into <code>b[off+1]</code>, and so on. The number of bytes read | ||
| 122 | * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of | ||
| 123 | * bytes actually read; these bytes will be stored in elements | ||
| 124 | * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>, | ||
| 125 | * leaving elements <code>b[off+</code><i>k</i><code>]</code> through | ||
| 126 | * <code>b[off+len-1]</code> unaffected. | ||
| 127 | * | ||
| 128 | * <p> In every case, elements <code>b[0]</code> through | ||
| 129 | * <code>b[off]</code> and elements <code>b[off+len]</code> through | ||
| 130 | * <code>b[b.length-1]</code> are unaffected. | ||
| 131 | * | ||
| 132 | * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method | ||
| 133 | * for class <code>InputStream</code> simply calls the method | ||
| 134 | * <code>read()</code> repeatedly. If the first such call results in an | ||
| 135 | * <code>IOException</code>, that exception is returned from the call to | ||
| 136 | * the <code>read(b,</code> <code>off,</code> <code>len)</code> method. If | ||
| 137 | * any subsequent call to <code>read()</code> results in a | ||
| 138 | * <code>IOException</code>, the exception is caught and treated as if it | ||
| 139 | * were end of file; the bytes read up to that point are stored into | ||
| 140 | * <code>b</code> and the number of bytes read before the exception | ||
| 141 | * occurred is returned. The default implementation of this method blocks | ||
| 142 | * until the requested amount of input data <code>len</code> has been read, | ||
| 143 | * end of file is detected, or an exception is thrown. Subclasses are encouraged | ||
| 144 | * to provide a more efficient implementation of this method. | ||
| 145 | * | ||
| 146 | * @param b the buffer into which the data is read. | ||
| 147 | * @param off the start offset in array <code>b</code> | ||
| 148 | * at which the data is written. | ||
| 149 | * @param len the maximum number of bytes to read. | ||
| 150 | * @return the total number of bytes read into the buffer, or | ||
| 151 | * <code>-1</code> if there is no more data because the end of | ||
| 152 | * the stream has been reached. | ||
| 153 | * @exception IOException If the first byte cannot be read for any reason | ||
| 154 | * other than end of file, or if the input stream has been closed, or if | ||
| 155 | * some other I/O error occurs. | ||
| 156 | * @exception NullPointerException If <code>b</code> is <code>null</code>. | ||
| 157 | * @exception IndexOutOfBoundsException If <code>off</code> is negative, | ||
| 158 | * <code>len</code> is negative, or <code>len</code> is greater than | ||
| 159 | * <code>b.length - off</code> | ||
| 160 | * @see java.io.InputStream#read() | ||
| 161 | */ | ||
| 162 | public int read(byte b[], int off, int len) throws IOException { | ||
| 163 | if (b == null) { | ||
| 164 | throw new NullPointerException(); | ||
| 165 | } else if (off < 0 || len < 0 || len > b.length - off) { | ||
| 166 | throw new IndexOutOfBoundsException(); | ||
| 167 | } else if (len == 0) { | ||
| 168 | return 0; | ||
| 169 | } | ||
| 170 | |||
| 171 | int c = read(); | ||
| 172 | if (c == -1) { | ||
| 173 | return -1; | ||
| 174 | } | ||
| 175 | b[off] = (byte)c; | ||
| 176 | |||
| 177 | int i = 1; | ||
| 178 | try { | ||
| 179 | for (; i < len ; i++) { | ||
| 180 | c = read(); | ||
| 181 | if (c == -1) { | ||
| 182 | break; | ||
| 183 | } | ||
| 184 | b[off + i] = (byte)c; | ||
| 185 | } | ||
| 186 | } catch (IOException ee) { | ||
| 187 | } | ||
| 188 | return i; | ||
| 189 | } | ||
| 190 | |||
| 191 | /** | ||
| 192 | * Skips over and discards <code>n</code> bytes of data from this input | ||
| 193 | * stream. The <code>skip</code> method may, for a variety of reasons, end | ||
| 194 | * up skipping over some smaller number of bytes, possibly <code>0</code>. | ||
| 195 | * This may result from any of a number of conditions; reaching end of file | ||
| 196 | * before <code>n</code> bytes have been skipped is only one possibility. | ||
| 197 | * The actual number of bytes skipped is returned. If <code>n</code> is | ||
| 198 | * negative, no bytes are skipped. | ||
| 199 | * | ||
| 200 | * <p> The <code>skip</code> method of this class creates a | ||
| 201 | * byte array and then repeatedly reads into it until <code>n</code> bytes | ||
| 202 | * have been read or the end of the stream has been reached. Subclasses are | ||
| 203 | * encouraged to provide a more efficient implementation of this method. | ||
| 204 | * For instance, the implementation may depend on the ability to seek. | ||
| 205 | * | ||
| 206 | * @param n the number of bytes to be skipped. | ||
| 207 | * @return the actual number of bytes skipped. | ||
| 208 | * @exception IOException if the stream does not support seek, | ||
| 209 | * or if some other I/O error occurs. | ||
| 210 | */ | ||
| 211 | public long skip(long n) throws IOException { | ||
| 212 | |||
| 213 | long remaining = n; | ||
| 214 | int nr; | ||
| 215 | if (skipBuffer == null) | ||
| 216 | skipBuffer = new byte[SKIP_BUFFER_SIZE]; | ||
| 217 | |||
| 218 | byte[] localSkipBuffer = skipBuffer; | ||
| 219 | |||
| 220 | if (n <= 0) { | ||
| 221 | return 0; | ||
| 222 | } | ||
| 223 | |||
| 224 | while (remaining > 0) { | ||
| 225 | nr = read(localSkipBuffer, 0, | ||
| 226 | (int) Math.min(SKIP_BUFFER_SIZE, remaining)); | ||
| 227 | if (nr < 0) { | ||
| 228 | break; | ||
| 229 | } | ||
| 230 | remaining -= nr; | ||
| 231 | } | ||
| 232 | |||
| 233 | return n - remaining; | ||
| 234 | } | ||
| 235 | |||
| 236 | /** | ||
| 237 | * Returns an estimate of the number of bytes that can be read (or | ||
| 238 | * skipped over) from this input stream without blocking by the next | ||
| 239 | * invocation of a method for this input stream. The next invocation | ||
| 240 | * might be the same thread or another thread. A single read or skip of this | ||
| 241 | * many bytes will not block, but may read or skip fewer bytes. | ||
| 242 | * | ||
| 243 | * <p> Note that while some implementations of {@code InputStream} will return | ||
| 244 | * the total number of bytes in the stream, many will not. It is | ||
| 245 | * never correct to use the return value of this method to allocate | ||
| 246 | * a buffer intended to hold all data in this stream. | ||
| 247 | * | ||
| 248 | * <p> A subclass' implementation of this method may choose to throw an | ||
| 249 | * {@link IOException} if this input stream has been closed by | ||
| 250 | * invoking the {@link #close()} method. | ||
| 251 | * | ||
| 252 | * <p> The {@code available} method for class {@code InputStream} always | ||
| 253 | * returns {@code 0}. | ||
| 254 | * | ||
| 255 | * <p> This method should be overridden by subclasses. | ||
| 256 | * | ||
| 257 | * @return an estimate of the number of bytes that can be read (or skipped | ||
| 258 | * over) from this input stream without blocking or {@code 0} when | ||
| 259 | * it reaches the end of the input stream. | ||
| 260 | * @exception IOException if an I/O error occurs. | ||
| 261 | */ | ||
| 262 | public int available() throws IOException { | ||
| 263 | return 0; | ||
| 264 | } | ||
| 265 | |||
| 266 | /** | ||
| 267 | * Closes this input stream and releases any system resources associated | ||
| 268 | * with the stream. | ||
| 269 | * | ||
| 270 | * <p> The <code>close</code> method of <code>InputStream</code> does | ||
| 271 | * nothing. | ||
| 272 | * | ||
| 273 | * @exception IOException if an I/O error occurs. | ||
| 274 | */ | ||
| 275 | public void close() throws IOException {} | ||
| 276 | |||
| 277 | /** | ||
| 278 | * Marks the current position in this input stream. A subsequent call to | ||
| 279 | * the <code>reset</code> method repositions this stream at the last marked | ||
| 280 | * position so that subsequent reads re-read the same bytes. | ||
| 281 | * | ||
| 282 | * <p> The <code>readlimit</code> arguments tells this input stream to | ||
| 283 | * allow that many bytes to be read before the mark position gets | ||
| 284 | * invalidated. | ||
| 285 | * | ||
| 286 | * <p> The general contract of <code>mark</code> is that, if the method | ||
| 287 | * <code>markSupported</code> returns <code>true</code>, the stream somehow | ||
| 288 | * remembers all the bytes read after the call to <code>mark</code> and | ||
| 289 | * stands ready to supply those same bytes again if and whenever the method | ||
| 290 | * <code>reset</code> is called. However, the stream is not required to | ||
| 291 | * remember any data at all if more than <code>readlimit</code> bytes are | ||
| 292 | * read from the stream before <code>reset</code> is called. | ||
| 293 | * | ||
| 294 | * <p> Marking a closed stream should not have any effect on the stream. | ||
| 295 | * | ||
| 296 | * <p> The <code>mark</code> method of <code>InputStream</code> does | ||
| 297 | * nothing. | ||
| 298 | * | ||
| 299 | * @param readlimit the maximum limit of bytes that can be read before | ||
| 300 | * the mark position becomes invalid. | ||
| 301 | * @see java.io.InputStream#reset() | ||
| 302 | */ | ||
| 303 | public synchronized void mark(int readlimit) {} | ||
| 304 | |||
| 305 | /** | ||
| 306 | * Repositions this stream to the position at the time the | ||
| 307 | * <code>mark</code> method was last called on this input stream. | ||
| 308 | * | ||
| 309 | * <p> The general contract of <code>reset</code> is: | ||
| 310 | * | ||
| 311 | * <p><ul> | ||
| 312 | * | ||
| 313 | * <li> If the method <code>markSupported</code> returns | ||
| 314 | * <code>true</code>, then: | ||
| 315 | * | ||
| 316 | * <ul><li> If the method <code>mark</code> has not been called since | ||
| 317 | * the stream was created, or the number of bytes read from the stream | ||
| 318 | * since <code>mark</code> was last called is larger than the argument | ||
| 319 | * to <code>mark</code> at that last call, then an | ||
| 320 | * <code>IOException</code> might be thrown. | ||
| 321 | * | ||
| 322 | * <li> If such an <code>IOException</code> is not thrown, then the | ||
| 323 | * stream is reset to a state such that all the bytes read since the | ||
| 324 | * most recent call to <code>mark</code> (or since the start of the | ||
| 325 | * file, if <code>mark</code> has not been called) will be resupplied | ||
| 326 | * to subsequent callers of the <code>read</code> method, followed by | ||
| 327 | * any bytes that otherwise would have been the next input data as of | ||
| 328 | * the time of the call to <code>reset</code>. </ul> | ||
| 329 | * | ||
| 330 | * <li> If the method <code>markSupported</code> returns | ||
| 331 | * <code>false</code>, then: | ||
| 332 | * | ||
| 333 | * <ul><li> The call to <code>reset</code> may throw an | ||
| 334 | * <code>IOException</code>. | ||
| 335 | * | ||
| 336 | * <li> If an <code>IOException</code> is not thrown, then the stream | ||
| 337 | * is reset to a fixed state that depends on the particular type of the | ||
| 338 | * input stream and how it was created. The bytes that will be supplied | ||
| 339 | * to subsequent callers of the <code>read</code> method depend on the | ||
| 340 | * particular type of the input stream. </ul></ul> | ||
| 341 | * | ||
| 342 | * <p>The method <code>reset</code> for class <code>InputStream</code> | ||
| 343 | * does nothing except throw an <code>IOException</code>. | ||
| 344 | * | ||
| 345 | * @exception IOException if this stream has not been marked or if the | ||
| 346 | * mark has been invalidated. | ||
| 347 | * @see java.io.InputStream#mark(int) | ||
| 348 | * @see java.io.IOException | ||
| 349 | */ | ||
| 350 | public synchronized void reset() throws IOException { | ||
| 351 | throw new IOException("mark/reset not supported"); | ||
| 352 | } | ||
| 353 | |||
| 354 | /** | ||
| 355 | * Tests if this input stream supports the <code>mark</code> and | ||
| 356 | * <code>reset</code> methods. Whether or not <code>mark</code> and | ||
| 357 | * <code>reset</code> are supported is an invariant property of a | ||
| 358 | * particular input stream instance. The <code>markSupported</code> method | ||
| 359 | * of <code>InputStream</code> returns <code>false</code>. | ||
| 360 | * | ||
| 361 | * @return <code>true</code> if this stream instance supports the mark | ||
| 362 | * and reset methods; <code>false</code> otherwise. | ||
| 363 | * @see java.io.InputStream#mark(int) | ||
| 364 | * @see java.io.InputStream#reset() | ||
| 365 | */ | ||
| 366 | public boolean markSupported() { | ||
| 367 | return false; | ||
| 368 | } | ||
| 369 | |||
| 370 | } | ||