1 /* 2 * Copyright (c) 1994, 2013, 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 import java.util.Arrays; 29 import java.util.Objects; 30 31 /** 32 * This abstract class is the superclass of all classes representing 33 * an input stream of bytes. 34 * 35 * <p> Applications that need to define a subclass of <code>InputStream</code> 36 * must always provide a method that returns the next byte of input. 37 * 38 * @author Arthur van Hoff 39 * @see java.io.BufferedInputStream 40 * @see java.io.ByteArrayInputStream 41 * @see java.io.DataInputStream 42 * @see java.io.FilterInputStream 43 * @see java.io.InputStream#read() 44 * @see java.io.OutputStream 45 * @see java.io.PushbackInputStream 46 * @since 1.0 47 */ 48 public abstract class InputStream implements Closeable { 49 50 // MAX_SKIP_BUFFER_SIZE is used to determine the maximum buffer size to 51 // use when skipping. 52 private static final int MAX_SKIP_BUFFER_SIZE = 2048; 53 54 private static final int DEFAULT_BUFFER_SIZE = 8192; 55 56 /** 57 * Reads the next byte of data from the input stream. The value byte is 58 * returned as an <code>int</code> in the range <code>0</code> to 59 * <code>255</code>. If no byte is available because the end of the stream 60 * has been reached, the value <code>-1</code> is returned. This method 61 * blocks until input data is available, the end of the stream is detected, 62 * or an exception is thrown. 63 * 64 * <p> A subclass must provide an implementation of this method. 65 * 66 * @return the next byte of data, or <code>-1</code> if the end of the 67 * stream is reached. 68 * @exception IOException if an I/O error occurs. 69 */ 70 public abstract int read() throws IOException; 71 72 /** 73 * Reads some number of bytes from the input stream and stores them into 74 * the buffer array <code>b</code>. The number of bytes actually read is 75 * returned as an integer. This method blocks until input data is 76 * available, end of file is detected, or an exception is thrown. 77 * 78 * <p> If the length of <code>b</code> is zero, then no bytes are read and 79 * <code>0</code> is returned; otherwise, there is an attempt to read at 80 * least one byte. If no byte is available because the stream is at the 81 * end of the file, the value <code>-1</code> is returned; otherwise, at 82 * least one byte is read and stored into <code>b</code>. 83 * 84 * <p> The first byte read is stored into element <code>b[0]</code>, the 85 * next one into <code>b[1]</code>, and so on. The number of bytes read is, 86 * at most, equal to the length of <code>b</code>. Let <i>k</i> be the 87 * number of bytes actually read; these bytes will be stored in elements 88 * <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>, 89 * leaving elements <code>b[</code><i>k</i><code>]</code> through 90 * <code>b[b.length-1]</code> unaffected. 91 * 92 * <p> The <code>read(b)</code> method for class <code>InputStream</code> 93 * has the same effect as: <pre><code> read(b, 0, b.length) </code></pre> 94 * 95 * @param b the buffer into which the data is read. 96 * @return the total number of bytes read into the buffer, or 97 * <code>-1</code> if there is no more data because the end of 98 * the stream has been reached. 99 * @exception IOException If the first byte cannot be read for any reason 100 * other than the end of the file, if the input stream has been closed, or 101 * if some other I/O error occurs. 102 * @exception NullPointerException if <code>b</code> is <code>null</code>. 103 * @see java.io.InputStream#read(byte[], int, int) 104 */ 105 public int read(byte b[]) throws IOException { 106 return read(b, 0, b.length); 107 } 108 109 /** 110 * Reads up to <code>len</code> bytes of data from the input stream into 111 * an array of bytes. An attempt is made to read as many as 112 * <code>len</code> bytes, but a smaller number may be read. 113 * The number of bytes actually read is returned as an integer. 114 * 115 * <p> This method blocks until input data is available, end of file is 116 * detected, or an exception is thrown. 117 * 118 * <p> If <code>len</code> is zero, then no bytes are read and 119 * <code>0</code> is returned; otherwise, there is an attempt to read at 120 * least one byte. If no byte is available because the stream is at end of 121 * file, the value <code>-1</code> is returned; otherwise, at least one 122 * byte is read and stored into <code>b</code>. 123 * 124 * <p> The first byte read is stored into element <code>b[off]</code>, the 125 * next one into <code>b[off+1]</code>, and so on. The number of bytes read 126 * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of 127 * bytes actually read; these bytes will be stored in elements 128 * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>, 129 * leaving elements <code>b[off+</code><i>k</i><code>]</code> through 130 * <code>b[off+len-1]</code> unaffected. 131 * 132 * <p> In every case, elements <code>b[0]</code> through 133 * <code>b[off]</code> and elements <code>b[off+len]</code> through 134 * <code>b[b.length-1]</code> are unaffected. 135 * 136 * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method 137 * for class <code>InputStream</code> simply calls the method 138 * <code>read()</code> repeatedly. If the first such call results in an 139 * <code>IOException</code>, that exception is returned from the call to 140 * the <code>read(b,</code> <code>off,</code> <code>len)</code> method. If 141 * any subsequent call to <code>read()</code> results in a 142 * <code>IOException</code>, the exception is caught and treated as if it 143 * were end of file; the bytes read up to that point are stored into 144 * <code>b</code> and the number of bytes read before the exception 145 * occurred is returned. The default implementation of this method blocks 146 * until the requested amount of input data <code>len</code> has been read, 147 * end of file is detected, or an exception is thrown. Subclasses are encouraged 148 * to provide a more efficient implementation of this method. 149 * 150 * @param b the buffer into which the data is read. 151 * @param off the start offset in array <code>b</code> 152 * at which the data is written. 153 * @param len the maximum number of bytes to read. 154 * @return the total number of bytes read into the buffer, or 155 * <code>-1</code> if there is no more data because the end of 156 * the stream has been reached. 157 * @exception IOException If the first byte cannot be read for any reason 158 * other than end of file, or if the input stream has been closed, or if 159 * some other I/O error occurs. 160 * @exception NullPointerException If <code>b</code> is <code>null</code>. 161 * @exception IndexOutOfBoundsException If <code>off</code> is negative, 162 * <code>len</code> is negative, or <code>len</code> is greater than 163 * <code>b.length - off</code> 164 * @see java.io.InputStream#read() 165 */ 166 public int read(byte b[], int off, int len) throws IOException { 167 if (b == null) { 168 throw new NullPointerException(); 169 } else if (off < 0 || len < 0 || len > b.length - off) { 170 throw new IndexOutOfBoundsException(); 171 } else if (len == 0) { 172 return 0; 173 } 174 175 int c = read(); 176 if (c == -1) { 177 return -1; 178 } 179 b[off] = (byte)c; 180 181 int i = 1; 182 try { 183 for (; i < len ; i++) { 184 c = read(); 185 if (c == -1) { 186 break; 187 } 188 b[off + i] = (byte)c; 189 } 190 } catch (IOException ee) { 191 } 192 return i; 193 } 194 195 /** 196 * The maximum size of array to allocate. 197 * Some VMs reserve some header words in an array. 198 * Attempts to allocate larger arrays may result in 199 * OutOfMemoryError: Requested array size exceeds VM limit 200 */ 201 private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8; 202 203 /** 204 * Reads all remaining bytes from the input stream. This method blocks until 205 * all remaining bytes have been read and end of stream is detected, or an 206 * exception is thrown. This method does not close the input stream. 207 * 208 * <p> When this stream reaches end of stream, further invocations of this 209 * method will return an empty byte array. 210 * 211 * <p> Note that this method is intended for simple cases where it is 212 * convenient to read all bytes into a byte array. It is not intended for 213 * reading input streams with large amounts of data. 214 * 215 * <p> The behavior for the case where the input stream is <i>asynchronously 216 * closed</i>, or the thread interrupted during the read, is highly input 217 * stream specific, and therefore not specified. 218 * 219 * <p> If an I/O error occurs reading from the input stream, then it may do 220 * so after some, but not all, bytes have been read. Consequently the input 221 * stream may not be at end of stream and may be in an inconsistent state. 222 * It is strongly recommended that the stream be promptly closed if an I/O 223 * error occurs. 224 * 225 * @return a byte array containing the bytes read from this input stream 226 * @throws IOException if an I/O error occurs 227 * @throws OutOfMemoryError if an array of the required size cannot be 228 * allocated. For example, if an array larger than {@code 2GB} would 229 * be required to store the bytes. 230 * 231 * @since 1.9 232 */ 233 public byte[] readAllBytes() throws IOException { 234 byte[] buf = new byte[DEFAULT_BUFFER_SIZE]; 235 int capacity = buf.length; 236 int nread = 0; 237 int n; 238 for (;;) { 239 // read to EOF which may read more or less than initial buffer size 240 while ((n = read(buf, nread, capacity - nread)) > 0) 241 nread += n; 242 243 // if the last call to read returned -1, then we're done 244 if (n < 0) 245 break; 246 247 // need to allocate a larger buffer 248 if (capacity <= MAX_BUFFER_SIZE - capacity) { 249 capacity = capacity << 1; 250 } else { 251 if (capacity == MAX_BUFFER_SIZE) 252 throw new OutOfMemoryError("Required array size too large"); 253 capacity = MAX_BUFFER_SIZE; 254 } 255 buf = Arrays.copyOf(buf, capacity); 256 } 257 return (capacity == nread) ? buf : Arrays.copyOf(buf, nread); 258 } 259 260 /** 261 * Reads the requested number of bytes from the input stream into the given 262 * byte array. This method blocks until {@code len} bytes of input data have 263 * been read, end of stream is detected, or an exception is thrown. The 264 * number of bytes actually read, possibly zero, is returned. This method 265 * does not close the input stream. 266 * 267 * <p> In the case where end of stream is reached before {@code len} bytes 268 * have been read, then the actual number of bytes read will be returned. 269 * When this stream reaches end of stream, further invocations of this 270 * method will return zero. 271 * 272 * <p> If {@code len} is zero, then no bytes are read and {@code 0} is 273 * returned; otherwise, there is an attempt to read up to {@code len} bytes. 274 * 275 * <p> The first byte read is stored into element {@code b[off]}, the next 276 * one in to {@code b[off+1]}, and so on. The number of bytes read is, at 277 * most, equal to {@code len}. Let <i>k</i> be the number of bytes actually 278 * read; these bytes will be stored in elements {@code b[off]} through 279 * {@code b[off+}<i>k</i>{@code -1]}, leaving elements {@code b[off+}<i>k</i> 280 * {@code ]} through {@code b[off+len-1]} unaffected. 281 * 282 * <p> In the case where {@code off > 0}, elements {@code b[0]} through 283 * {@code b[off-1]} are unaffected. In every case, elements 284 * {@code b[off+len]} through {@code b[b.length-1]} are unaffected. 285 * 286 * <p> The behavior for the case where the input stream is <i>asynchronously 287 * closed</i>, or the thread interrupted during the read, is highly input 288 * stream specific, and therefore not specified. 289 * 290 * <p> If an I/O error occurs reading from the input stream, then it may do 291 * so after some, but not all, bytes of {@code b} have been updated with 292 * data from the input stream. Consequently the input stream and {@code b} 293 * may be in an inconsistent state. It is strongly recommended that the 294 * stream be promptly closed if an I/O error occurs. 295 * 296 * @param b the buffer into which the data is read 297 * @param off the start offset in {@code b} at which the data is written 298 * @param len the maximum number of bytes to read 299 * @return the actual number of bytes read into the buffer 300 * @throws IOException if an I/O error occurs 301 * @throws NullPointerException if {@code b} is {@code null} 302 * @throws IndexOutOfBoundsException If {@code off} is negative, {@code len} 303 * is negative, or {@code len} is greater than {@code b.length - off} 304 * 305 * @since 1.9 306 */ 307 public int readNBytes(byte[] b, int off, int len) throws IOException { 308 Objects.requireNonNull(b); 309 if (off < 0 || len < 0 || len > b.length - off) 310 throw new IndexOutOfBoundsException(); 311 int n = 0; 312 while (n < len) { 313 int count = read(b, off + n, len - n); 314 if (count < 0) 315 break; 316 n += count; 317 } 318 return n; 319 } 320 321 /** 322 * Skips over and discards <code>n</code> bytes of data from this input 323 * stream. The <code>skip</code> method may, for a variety of reasons, end 324 * up skipping over some smaller number of bytes, possibly <code>0</code>. 325 * This may result from any of a number of conditions; reaching end of file 326 * before <code>n</code> bytes have been skipped is only one possibility. 327 * The actual number of bytes skipped is returned. If {@code n} is 328 * negative, the {@code skip} method for class {@code InputStream} always 329 * returns 0, and no bytes are skipped. Subclasses may handle the negative 330 * value differently. 331 * 332 * <p> The <code>skip</code> method of this class creates a 333 * byte array and then repeatedly reads into it until <code>n</code> bytes 334 * have been read or the end of the stream has been reached. Subclasses are 335 * encouraged to provide a more efficient implementation of this method. 336 * For instance, the implementation may depend on the ability to seek. 337 * 338 * @param n the number of bytes to be skipped. 339 * @return the actual number of bytes skipped. 340 * @exception IOException if the stream does not support seek, 341 * or if some other I/O error occurs. 342 */ 343 public long skip(long n) throws IOException { 344 345 long remaining = n; 346 int nr; 347 348 if (n <= 0) { 349 return 0; 350 } 351 352 int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining); 353 byte[] skipBuffer = new byte[size]; 354 while (remaining > 0) { 355 nr = read(skipBuffer, 0, (int)Math.min(size, remaining)); 356 if (nr < 0) { 357 break; 358 } 359 remaining -= nr; 360 } 361 362 return n - remaining; 363 } 364 365 /** 366 * Returns an estimate of the number of bytes that can be read (or 367 * skipped over) from this input stream without blocking by the next 368 * invocation of a method for this input stream. The next invocation 369 * might be the same thread or another thread. A single read or skip of this 370 * many bytes will not block, but may read or skip fewer bytes. 371 * 372 * <p> Note that while some implementations of {@code InputStream} will return 373 * the total number of bytes in the stream, many will not. It is 374 * never correct to use the return value of this method to allocate 375 * a buffer intended to hold all data in this stream. 376 * 377 * <p> A subclass' implementation of this method may choose to throw an 378 * {@link IOException} if this input stream has been closed by 379 * invoking the {@link #close()} method. 380 * 381 * <p> The {@code available} method for class {@code InputStream} always 382 * returns {@code 0}. 383 * 384 * <p> This method should be overridden by subclasses. 385 * 386 * @return an estimate of the number of bytes that can be read (or skipped 387 * over) from this input stream without blocking or {@code 0} when 388 * it reaches the end of the input stream. 389 * @exception IOException if an I/O error occurs. 390 */ 391 public int available() throws IOException { 392 return 0; 393 } 394 395 /** 396 * Closes this input stream and releases any system resources associated 397 * with the stream. 398 * 399 * <p> The <code>close</code> method of <code>InputStream</code> does 400 * nothing. 401 * 402 * @exception IOException if an I/O error occurs. 403 */ 404 public void close() throws IOException {} 405 406 /** 407 * Marks the current position in this input stream. A subsequent call to 408 * the <code>reset</code> method repositions this stream at the last marked 409 * position so that subsequent reads re-read the same bytes. 410 * 411 * <p> The <code>readlimit</code> arguments tells this input stream to 412 * allow that many bytes to be read before the mark position gets 413 * invalidated. 414 * 415 * <p> The general contract of <code>mark</code> is that, if the method 416 * <code>markSupported</code> returns <code>true</code>, the stream somehow 417 * remembers all the bytes read after the call to <code>mark</code> and 418 * stands ready to supply those same bytes again if and whenever the method 419 * <code>reset</code> is called. However, the stream is not required to 420 * remember any data at all if more than <code>readlimit</code> bytes are 421 * read from the stream before <code>reset</code> is called. 422 * 423 * <p> Marking a closed stream should not have any effect on the stream. 424 * 425 * <p> The <code>mark</code> method of <code>InputStream</code> does 426 * nothing. 427 * 428 * @param readlimit the maximum limit of bytes that can be read before 429 * the mark position becomes invalid. 430 * @see java.io.InputStream#reset() 431 */ 432 public synchronized void mark(int readlimit) {} 433 434 /** 435 * Repositions this stream to the position at the time the 436 * <code>mark</code> method was last called on this input stream. 437 * 438 * <p> The general contract of <code>reset</code> is: 439 * 440 * <ul> 441 * <li> If the method <code>markSupported</code> returns 442 * <code>true</code>, then: 443 * 444 * <ul><li> If the method <code>mark</code> has not been called since 445 * the stream was created, or the number of bytes read from the stream 446 * since <code>mark</code> was last called is larger than the argument 447 * to <code>mark</code> at that last call, then an 448 * <code>IOException</code> might be thrown. 449 * 450 * <li> If such an <code>IOException</code> is not thrown, then the 451 * stream is reset to a state such that all the bytes read since the 452 * most recent call to <code>mark</code> (or since the start of the 453 * file, if <code>mark</code> has not been called) will be resupplied 454 * to subsequent callers of the <code>read</code> method, followed by 455 * any bytes that otherwise would have been the next input data as of 456 * the time of the call to <code>reset</code>. </ul> 457 * 458 * <li> If the method <code>markSupported</code> returns 459 * <code>false</code>, then: 460 * 461 * <ul><li> The call to <code>reset</code> may throw an 462 * <code>IOException</code>. 463 * 464 * <li> If an <code>IOException</code> is not thrown, then the stream 465 * is reset to a fixed state that depends on the particular type of the 466 * input stream and how it was created. The bytes that will be supplied 467 * to subsequent callers of the <code>read</code> method depend on the 468 * particular type of the input stream. </ul></ul> 469 * 470 * <p>The method <code>reset</code> for class <code>InputStream</code> 471 * does nothing except throw an <code>IOException</code>. 472 * 473 * @exception IOException if this stream has not been marked or if the 474 * mark has been invalidated. 475 * @see java.io.InputStream#mark(int) 476 * @see java.io.IOException 477 */ 478 public synchronized void reset() throws IOException { 479 throw new IOException("mark/reset not supported"); 480 } 481 482 /** 483 * Tests if this input stream supports the <code>mark</code> and 484 * <code>reset</code> methods. Whether or not <code>mark</code> and 485 * <code>reset</code> are supported is an invariant property of a 486 * particular input stream instance. The <code>markSupported</code> method 487 * of <code>InputStream</code> returns <code>false</code>. 488 * 489 * @return <code>true</code> if this stream instance supports the mark 490 * and reset methods; <code>false</code> otherwise. 491 * @see java.io.InputStream#mark(int) 492 * @see java.io.InputStream#reset() 493 */ 494 public boolean markSupported() { 495 return false; 496 } 497 498 /** 499 * Reads all bytes from this input stream and writes the bytes to the 500 * given output stream in the order that they are read. On return, this 501 * input stream will be at end of stream. This method does not close either 502 * stream. 503 * <p> 504 * This method may block indefinitely reading from the input stream, or 505 * writing to the output stream. The behavior for the case where the input 506 * and/or output stream is <i>asynchronously closed</i>, or the thread 507 * interrupted during the transfer, is highly input and output stream 508 * specific, and therefore not specified. 509 * <p> 510 * If an I/O error occurs reading from the input stream or writing to the 511 * output stream, then it may do so after some bytes have been read or 512 * written. Consequently the input stream may not be at end of stream and 513 * one, or both, streams may be in an inconsistent state. It is strongly 514 * recommended that both streams be promptly closed if an I/O error occurs. 515 * 516 * @param out the output stream, non-null 517 * @return the number of bytes transferred 518 * @throws IOException if an I/O error occurs when reading or writing 519 * @throws NullPointerException if {@code out} is {@code null} 520 * 521 * @since 1.9 522 */ 523 public long transferTo(OutputStream out) throws IOException { 524 Objects.requireNonNull(out, "out"); 525 long transferred = 0; 526 byte[] buffer = new byte[DEFAULT_BUFFER_SIZE]; 527 int read; 528 while ((read = this.read(buffer, 0, DEFAULT_BUFFER_SIZE)) >= 0) { 529 out.write(buffer, 0, read); 530 transferred += read; 531 } 532 return transferred; 533 } 534 }