1 /* 2 * Copyright (c) 1994, 2017, 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.ArrayList; 29 import java.util.Arrays; 30 import java.util.List; 31 import java.util.Objects; 32 33 /** 34 * This abstract class is the superclass of all classes representing 35 * an input stream of bytes. 36 * 37 * <p> Applications that need to define a subclass of <code>InputStream</code> 38 * must always provide a method that returns the next byte of input. 39 * 40 * @author Arthur van Hoff 41 * @see java.io.BufferedInputStream 42 * @see java.io.ByteArrayInputStream 43 * @see java.io.DataInputStream 44 * @see java.io.FilterInputStream 45 * @see java.io.InputStream#read() 46 * @see java.io.OutputStream 47 * @see java.io.PushbackInputStream 48 * @since 1.0 49 */ 50 public abstract class InputStream implements Closeable { 51 52 // MAX_SKIP_BUFFER_SIZE is used to determine the maximum buffer size to 53 // use when skipping. 54 private static final int MAX_SKIP_BUFFER_SIZE = 2048; 55 56 private static final int DEFAULT_BUFFER_SIZE = 8192; 57 58 /** 59 * Reads the next byte of data from the input stream. The value byte is 60 * returned as an <code>int</code> in the range <code>0</code> to 61 * <code>255</code>. If no byte is available because the end of the stream 62 * has been reached, the value <code>-1</code> is returned. This method 63 * blocks until input data is available, the end of the stream is detected, 64 * or an exception is thrown. 65 * 66 * <p> A subclass must provide an implementation of this method. 67 * 68 * @return the next byte of data, or <code>-1</code> if the end of the 69 * stream is reached. 70 * @exception IOException if an I/O error occurs. 71 */ 72 public abstract int read() throws IOException; 73 74 /** 75 * Reads some number of bytes from the input stream and stores them into 76 * the buffer array <code>b</code>. The number of bytes actually read is 77 * returned as an integer. This method blocks until input data is 78 * available, end of file is detected, or an exception is thrown. 79 * 80 * <p> If the length of <code>b</code> is zero, then no bytes are read and 81 * <code>0</code> is returned; otherwise, there is an attempt to read at 82 * least one byte. If no byte is available because the stream is at the 83 * end of the file, the value <code>-1</code> is returned; otherwise, at 84 * least one byte is read and stored into <code>b</code>. 85 * 86 * <p> The first byte read is stored into element <code>b[0]</code>, the 87 * next one into <code>b[1]</code>, and so on. The number of bytes read is, 88 * at most, equal to the length of <code>b</code>. Let <i>k</i> be the 89 * number of bytes actually read; these bytes will be stored in elements 90 * <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>, 91 * leaving elements <code>b[</code><i>k</i><code>]</code> through 92 * <code>b[b.length-1]</code> unaffected. 93 * 94 * <p> The <code>read(b)</code> method for class <code>InputStream</code> 95 * has the same effect as: <pre><code> read(b, 0, b.length) </code></pre> 96 * 97 * @param b the buffer into which the data is read. 98 * @return the total number of bytes read into the buffer, or 99 * <code>-1</code> if there is no more data because the end of 100 * the stream has been reached. 101 * @exception IOException If the first byte cannot be read for any reason 102 * other than the end of the file, if the input stream has been closed, or 103 * if some other I/O error occurs. 104 * @exception NullPointerException if <code>b</code> is <code>null</code>. 105 * @see java.io.InputStream#read(byte[], int, int) 106 */ 107 public int read(byte b[]) throws IOException { 108 return read(b, 0, b.length); 109 } 110 111 /** 112 * Reads up to <code>len</code> bytes of data from the input stream into 113 * an array of bytes. An attempt is made to read as many as 114 * <code>len</code> bytes, but a smaller number may be read. 115 * The number of bytes actually read is returned as an integer. 116 * 117 * <p> This method blocks until input data is available, end of file is 118 * detected, or an exception is thrown. 119 * 120 * <p> If <code>len</code> is zero, then no bytes are read and 121 * <code>0</code> is returned; otherwise, there is an attempt to read at 122 * least one byte. If no byte is available because the stream is at end of 123 * file, the value <code>-1</code> is returned; otherwise, at least one 124 * byte is read and stored into <code>b</code>. 125 * 126 * <p> The first byte read is stored into element <code>b[off]</code>, the 127 * next one into <code>b[off+1]</code>, and so on. The number of bytes read 128 * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of 129 * bytes actually read; these bytes will be stored in elements 130 * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>, 131 * leaving elements <code>b[off+</code><i>k</i><code>]</code> through 132 * <code>b[off+len-1]</code> unaffected. 133 * 134 * <p> In every case, elements <code>b[0]</code> through 135 * <code>b[off]</code> and elements <code>b[off+len]</code> through 136 * <code>b[b.length-1]</code> are unaffected. 137 * 138 * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method 139 * for class <code>InputStream</code> simply calls the method 140 * <code>read()</code> repeatedly. If the first such call results in an 141 * <code>IOException</code>, that exception is returned from the call to 142 * the <code>read(b,</code> <code>off,</code> <code>len)</code> method. If 143 * any subsequent call to <code>read()</code> results in a 144 * <code>IOException</code>, the exception is caught and treated as if it 145 * were end of file; the bytes read up to that point are stored into 146 * <code>b</code> and the number of bytes read before the exception 147 * occurred is returned. The default implementation of this method blocks 148 * until the requested amount of input data <code>len</code> has been read, 149 * end of file is detected, or an exception is thrown. Subclasses are encouraged 150 * to provide a more efficient implementation of this method. 151 * 152 * @param b the buffer into which the data is read. 153 * @param off the start offset in array <code>b</code> 154 * at which the data is written. 155 * @param len the maximum number of bytes to read. 156 * @return the total number of bytes read into the buffer, or 157 * <code>-1</code> if there is no more data because the end of 158 * the stream has been reached. 159 * @exception IOException If the first byte cannot be read for any reason 160 * other than end of file, or if the input stream has been closed, or if 161 * some other I/O error occurs. 162 * @exception NullPointerException If <code>b</code> is <code>null</code>. 163 * @exception IndexOutOfBoundsException If <code>off</code> is negative, 164 * <code>len</code> is negative, or <code>len</code> is greater than 165 * <code>b.length - off</code> 166 * @see java.io.InputStream#read() 167 */ 168 public int read(byte b[], int off, int len) throws IOException { 169 Objects.requireNonNull(b); 170 Objects.checkFromIndexSize(off, len, b.length); 171 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 9 232 */ 233 public byte[] readAllBytes() throws IOException { 234 List<byte[]> bufs = null; 235 byte[] result = null; 236 int total = 0; 237 int n; 238 do { 239 byte[] buf = new byte[DEFAULT_BUFFER_SIZE]; 240 int nread = 0; 241 242 // read to EOF which may read more or less than buffer size 243 while ((n = read(buf, nread, buf.length - nread)) > 0) { 244 nread += n; 245 } 246 247 if (nread > 0) { 248 if (MAX_BUFFER_SIZE - total < nread) { 249 throw new OutOfMemoryError("Required array size too large"); 250 } 251 total += nread; 252 if (result == null) { 253 result = buf; 254 } else { 255 if (bufs == null) { 256 bufs = new ArrayList<>(); 257 bufs.add(result); 258 } 259 bufs.add(buf); 260 } 261 } 262 } while (n >= 0); // if the last call to read returned -1, then break 263 264 if (bufs == null) { 265 if (result == null) { 266 return new byte[0]; 267 } 268 return result.length == total ? 269 result : Arrays.copyOf(result, total); 270 } 271 272 result = new byte[total]; 273 int offset = 0; 274 int remaining = total; 275 for (byte[] b : bufs) { 276 int len = Math.min(b.length, remaining); 277 System.arraycopy(b, 0, result, offset, len); 278 offset += len; 279 remaining -= len; 280 } 281 282 return result; 283 } 284 285 /** 286 * Reads the requested number of bytes from the input stream into the given 287 * byte array. This method blocks until {@code len} bytes of input data have 288 * been read, end of stream is detected, or an exception is thrown. The 289 * number of bytes actually read, possibly zero, is returned. This method 290 * does not close the input stream. 291 * 292 * <p> In the case where end of stream is reached before {@code len} bytes 293 * have been read, then the actual number of bytes read will be returned. 294 * When this stream reaches end of stream, further invocations of this 295 * method will return zero. 296 * 297 * <p> If {@code len} is zero, then no bytes are read and {@code 0} is 298 * returned; otherwise, there is an attempt to read up to {@code len} bytes. 299 * 300 * <p> The first byte read is stored into element {@code b[off]}, the next 301 * one in to {@code b[off+1]}, and so on. The number of bytes read is, at 302 * most, equal to {@code len}. Let <i>k</i> be the number of bytes actually 303 * read; these bytes will be stored in elements {@code b[off]} through 304 * {@code b[off+}<i>k</i>{@code -1]}, leaving elements {@code b[off+}<i>k</i> 305 * {@code ]} through {@code b[off+len-1]} unaffected. 306 * 307 * <p> The behavior for the case where the input stream is <i>asynchronously 308 * closed</i>, or the thread interrupted during the read, is highly input 309 * stream specific, and therefore not specified. 310 * 311 * <p> If an I/O error occurs reading from the input stream, then it may do 312 * so after some, but not all, bytes of {@code b} have been updated with 313 * data from the input stream. Consequently the input stream and {@code b} 314 * may be in an inconsistent state. It is strongly recommended that the 315 * stream be promptly closed if an I/O error occurs. 316 * 317 * @param b the byte array into which the data is read 318 * @param off the start offset in {@code b} at which the data is written 319 * @param len the maximum number of bytes to read 320 * @return the actual number of bytes read into the buffer 321 * @throws IOException if an I/O error occurs 322 * @throws NullPointerException if {@code b} is {@code null} 323 * @throws IndexOutOfBoundsException If {@code off} is negative, {@code len} 324 * is negative, or {@code len} is greater than {@code b.length - off} 325 * 326 * @since 9 327 */ 328 public int readNBytes(byte[] b, int off, int len) throws IOException { 329 Objects.requireNonNull(b); 330 Objects.checkFromIndexSize(off, len, b.length); 331 332 int n = 0; 333 while (n < len) { 334 int count = read(b, off + n, len - n); 335 if (count < 0) 336 break; 337 n += count; 338 } 339 return n; 340 } 341 342 /** 343 * Skips over and discards <code>n</code> bytes of data from this input 344 * stream. The <code>skip</code> method may, for a variety of reasons, end 345 * up skipping over some smaller number of bytes, possibly <code>0</code>. 346 * This may result from any of a number of conditions; reaching end of file 347 * before <code>n</code> bytes have been skipped is only one possibility. 348 * The actual number of bytes skipped is returned. If {@code n} is 349 * negative, the {@code skip} method for class {@code InputStream} always 350 * returns 0, and no bytes are skipped. Subclasses may handle the negative 351 * value differently. 352 * 353 * <p> The <code>skip</code> method implementation of this class creates a 354 * byte array and then repeatedly reads into it until <code>n</code> bytes 355 * have been read or the end of the stream has been reached. Subclasses are 356 * encouraged to provide a more efficient implementation of this method. 357 * For instance, the implementation may depend on the ability to seek. 358 * 359 * @param n the number of bytes to be skipped. 360 * @return the actual number of bytes skipped. 361 * @throws IOException if an I/O error occurs. 362 */ 363 public long skip(long n) throws IOException { 364 365 long remaining = n; 366 int nr; 367 368 if (n <= 0) { 369 return 0; 370 } 371 372 int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining); 373 byte[] skipBuffer = new byte[size]; 374 while (remaining > 0) { 375 nr = read(skipBuffer, 0, (int)Math.min(size, remaining)); 376 if (nr < 0) { 377 break; 378 } 379 remaining -= nr; 380 } 381 382 return n - remaining; 383 } 384 385 /** 386 * Returns an estimate of the number of bytes that can be read (or 387 * skipped over) from this input stream without blocking by the next 388 * invocation of a method for this input stream. The next invocation 389 * might be the same thread or another thread. A single read or skip of this 390 * many bytes will not block, but may read or skip fewer bytes. 391 * 392 * <p> Note that while some implementations of {@code InputStream} will return 393 * the total number of bytes in the stream, many will not. It is 394 * never correct to use the return value of this method to allocate 395 * a buffer intended to hold all data in this stream. 396 * 397 * <p> A subclass' implementation of this method may choose to throw an 398 * {@link IOException} if this input stream has been closed by 399 * invoking the {@link #close()} method. 400 * 401 * <p> The {@code available} method for class {@code InputStream} always 402 * returns {@code 0}. 403 * 404 * <p> This method should be overridden by subclasses. 405 * 406 * @return an estimate of the number of bytes that can be read (or skipped 407 * over) from this input stream without blocking or {@code 0} when 408 * it reaches the end of the input stream. 409 * @exception IOException if an I/O error occurs. 410 */ 411 public int available() throws IOException { 412 return 0; 413 } 414 415 /** 416 * Closes this input stream and releases any system resources associated 417 * with the stream. 418 * 419 * <p> The <code>close</code> method of <code>InputStream</code> does 420 * nothing. 421 * 422 * @exception IOException if an I/O error occurs. 423 */ 424 public void close() throws IOException {} 425 426 /** 427 * Marks the current position in this input stream. A subsequent call to 428 * the <code>reset</code> method repositions this stream at the last marked 429 * position so that subsequent reads re-read the same bytes. 430 * 431 * <p> The <code>readlimit</code> arguments tells this input stream to 432 * allow that many bytes to be read before the mark position gets 433 * invalidated. 434 * 435 * <p> The general contract of <code>mark</code> is that, if the method 436 * <code>markSupported</code> returns <code>true</code>, the stream somehow 437 * remembers all the bytes read after the call to <code>mark</code> and 438 * stands ready to supply those same bytes again if and whenever the method 439 * <code>reset</code> is called. However, the stream is not required to 440 * remember any data at all if more than <code>readlimit</code> bytes are 441 * read from the stream before <code>reset</code> is called. 442 * 443 * <p> Marking a closed stream should not have any effect on the stream. 444 * 445 * <p> The <code>mark</code> method of <code>InputStream</code> does 446 * nothing. 447 * 448 * @param readlimit the maximum limit of bytes that can be read before 449 * the mark position becomes invalid. 450 * @see java.io.InputStream#reset() 451 */ 452 public synchronized void mark(int readlimit) {} 453 454 /** 455 * Repositions this stream to the position at the time the 456 * <code>mark</code> method was last called on this input stream. 457 * 458 * <p> The general contract of <code>reset</code> is: 459 * 460 * <ul> 461 * <li> If the method <code>markSupported</code> returns 462 * <code>true</code>, then: 463 * 464 * <ul><li> If the method <code>mark</code> has not been called since 465 * the stream was created, or the number of bytes read from the stream 466 * since <code>mark</code> was last called is larger than the argument 467 * to <code>mark</code> at that last call, then an 468 * <code>IOException</code> might be thrown. 469 * 470 * <li> If such an <code>IOException</code> is not thrown, then the 471 * stream is reset to a state such that all the bytes read since the 472 * most recent call to <code>mark</code> (or since the start of the 473 * file, if <code>mark</code> has not been called) will be resupplied 474 * to subsequent callers of the <code>read</code> method, followed by 475 * any bytes that otherwise would have been the next input data as of 476 * the time of the call to <code>reset</code>. </ul> 477 * 478 * <li> If the method <code>markSupported</code> returns 479 * <code>false</code>, then: 480 * 481 * <ul><li> The call to <code>reset</code> may throw an 482 * <code>IOException</code>. 483 * 484 * <li> If an <code>IOException</code> is not thrown, then the stream 485 * is reset to a fixed state that depends on the particular type of the 486 * input stream and how it was created. The bytes that will be supplied 487 * to subsequent callers of the <code>read</code> method depend on the 488 * particular type of the input stream. </ul></ul> 489 * 490 * <p>The method <code>reset</code> for class <code>InputStream</code> 491 * does nothing except throw an <code>IOException</code>. 492 * 493 * @exception IOException if this stream has not been marked or if the 494 * mark has been invalidated. 495 * @see java.io.InputStream#mark(int) 496 * @see java.io.IOException 497 */ 498 public synchronized void reset() throws IOException { 499 throw new IOException("mark/reset not supported"); 500 } 501 502 /** 503 * Tests if this input stream supports the <code>mark</code> and 504 * <code>reset</code> methods. Whether or not <code>mark</code> and 505 * <code>reset</code> are supported is an invariant property of a 506 * particular input stream instance. The <code>markSupported</code> method 507 * of <code>InputStream</code> returns <code>false</code>. 508 * 509 * @return <code>true</code> if this stream instance supports the mark 510 * and reset methods; <code>false</code> otherwise. 511 * @see java.io.InputStream#mark(int) 512 * @see java.io.InputStream#reset() 513 */ 514 public boolean markSupported() { 515 return false; 516 } 517 518 /** 519 * Reads all bytes from this input stream and writes the bytes to the 520 * given output stream in the order that they are read. On return, this 521 * input stream will be at end of stream. This method does not close either 522 * stream. 523 * <p> 524 * This method may block indefinitely reading from the input stream, or 525 * writing to the output stream. The behavior for the case where the input 526 * and/or output stream is <i>asynchronously closed</i>, or the thread 527 * interrupted during the transfer, is highly input and output stream 528 * specific, and therefore not specified. 529 * <p> 530 * If an I/O error occurs reading from the input stream or writing to the 531 * output stream, then it may do so after some bytes have been read or 532 * written. Consequently the input stream may not be at end of stream and 533 * one, or both, streams may be in an inconsistent state. It is strongly 534 * recommended that both streams be promptly closed if an I/O error occurs. 535 * 536 * @param out the output stream, non-null 537 * @return the number of bytes transferred 538 * @throws IOException if an I/O error occurs when reading or writing 539 * @throws NullPointerException if {@code out} is {@code null} 540 * 541 * @since 9 542 */ 543 public long transferTo(OutputStream out) throws IOException { 544 Objects.requireNonNull(out, "out"); 545 long transferred = 0; 546 byte[] buffer = new byte[DEFAULT_BUFFER_SIZE]; 547 int read; 548 while ((read = this.read(buffer, 0, DEFAULT_BUFFER_SIZE)) >= 0) { 549 out.write(buffer, 0, read); 550 transferred += read; 551 } 552 return transferred; 553 } 554 }