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.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 Objects.requireNonNull(b); 168 Objects.checkFromIndexSize(off, len, b.length); 169 if (len == 0) { 170 return 0; 171 } 172 173 int c = read(); 174 if (c == -1) { 175 return -1; 176 } 177 b[off] = (byte)c; 178 179 int i = 1; 180 try { 181 for (; i < len ; i++) { 182 c = read(); 183 if (c == -1) { 184 break; 185 } 186 b[off + i] = (byte)c; 187 } 188 } catch (IOException ee) { 189 } 190 return i; 191 } 192 193 /** 194 * The maximum size of array to allocate. 195 * Some VMs reserve some header words in an array. 196 * Attempts to allocate larger arrays may result in 197 * OutOfMemoryError: Requested array size exceeds VM limit 198 */ 199 private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8; 200 201 /** 202 * Reads all remaining bytes from the input stream. This method blocks until 203 * all remaining bytes have been read and end of stream is detected, or an 204 * exception is thrown. This method does not close the input stream. 205 * 206 * <p> When this stream reaches end of stream, further invocations of this 207 * method will return an empty byte array. 208 * 209 * <p> Note that this method is intended for simple cases where it is 210 * convenient to read all bytes into a byte array. It is not intended for 211 * reading input streams with large amounts of data. 212 * 213 * <p> The behavior for the case where the input stream is <i>asynchronously 214 * closed</i>, or the thread interrupted during the read, is highly input 215 * stream specific, and therefore not specified. 216 * 217 * <p> If an I/O error occurs reading from the input stream, then it may do 218 * so after some, but not all, bytes have been read. Consequently the input 219 * stream may not be at end of stream and may be in an inconsistent state. 220 * It is strongly recommended that the stream be promptly closed if an I/O 221 * error occurs. 222 * 223 * @return a byte array containing the bytes read from this input stream 224 * @throws IOException if an I/O error occurs 225 * @throws OutOfMemoryError if an array of the required size cannot be 226 * allocated. For example, if an array larger than {@code 2GB} would 227 * be required to store the bytes. 228 * 229 * @since 9 230 */ 231 public byte[] readAllBytes() throws IOException { 232 byte[] buf = new byte[DEFAULT_BUFFER_SIZE]; 233 int capacity = buf.length; 234 int nread = 0; 235 int n; 236 for (;;) { 237 // read to EOF which may read more or less than initial buffer size 238 while ((n = read(buf, nread, capacity - nread)) > 0) 239 nread += n; 240 241 // if the last call to read returned -1, then we're done 242 if (n < 0) 243 break; 244 245 // need to allocate a larger buffer 246 if (capacity <= MAX_BUFFER_SIZE - capacity) { 247 capacity = capacity << 1; 248 } else { 249 if (capacity == MAX_BUFFER_SIZE) 250 throw new OutOfMemoryError("Required array size too large"); 251 capacity = MAX_BUFFER_SIZE; 252 } 253 buf = Arrays.copyOf(buf, capacity); 254 } 255 return (capacity == nread) ? buf : Arrays.copyOf(buf, nread); 256 } 257 258 /** 259 * Reads the requested number of bytes from the input stream into the given 260 * byte array. This method blocks until {@code len} bytes of input data have 261 * been read, end of stream is detected, or an exception is thrown. The 262 * number of bytes actually read, possibly zero, is returned. This method 263 * does not close the input stream. 264 * 265 * <p> In the case where end of stream is reached before {@code len} bytes 266 * have been read, then the actual number of bytes read will be returned. 267 * When this stream reaches end of stream, further invocations of this 268 * method will return zero. 269 * 270 * <p> If {@code len} is zero, then no bytes are read and {@code 0} is 271 * returned; otherwise, there is an attempt to read up to {@code len} bytes. 272 * 273 * <p> The first byte read is stored into element {@code b[off]}, the next 274 * one in to {@code b[off+1]}, and so on. The number of bytes read is, at 275 * most, equal to {@code len}. Let <i>k</i> be the number of bytes actually 276 * read; these bytes will be stored in elements {@code b[off]} through 277 * {@code b[off+}<i>k</i>{@code -1]}, leaving elements {@code b[off+}<i>k</i> 278 * {@code ]} through {@code b[off+len-1]} unaffected. 279 * 280 * <p> The behavior for the case where the input stream is <i>asynchronously 281 * closed</i>, or the thread interrupted during the read, is highly input 282 * stream specific, and therefore not specified. 283 * 284 * <p> If an I/O error occurs reading from the input stream, then it may do 285 * so after some, but not all, bytes of {@code b} have been updated with 286 * data from the input stream. Consequently the input stream and {@code b} 287 * may be in an inconsistent state. It is strongly recommended that the 288 * stream be promptly closed if an I/O error occurs. 289 * 290 * @param b the byte array into which the data is read 291 * @param off the start offset in {@code b} at which the data is written 292 * @param len the maximum number of bytes to read 293 * @return the actual number of bytes read into the buffer 294 * @throws IOException if an I/O error occurs 295 * @throws NullPointerException if {@code b} is {@code null} 296 * @throws IndexOutOfBoundsException If {@code off} is negative, {@code len} 297 * is negative, or {@code len} is greater than {@code b.length - off} 298 * 299 * @since 9 300 */ 301 public int readNBytes(byte[] b, int off, int len) throws IOException { 302 Objects.requireNonNull(b); 303 Objects.checkFromIndexSize(off, len, b.length); 304 305 int n = 0; 306 while (n < len) { 307 int count = read(b, off + n, len - n); 308 if (count < 0) 309 break; 310 n += count; 311 } 312 return n; 313 } 314 315 /** 316 * Skips over and discards <code>n</code> bytes of data from this input 317 * stream. The <code>skip</code> method may, for a variety of reasons, end 318 * up skipping over some smaller number of bytes, possibly <code>0</code>. 319 * This may result from any of a number of conditions; reaching end of file 320 * before <code>n</code> bytes have been skipped is only one possibility. 321 * The actual number of bytes skipped is returned. If {@code n} is 322 * negative, the {@code skip} method for class {@code InputStream} always 323 * returns 0, and no bytes are skipped. Subclasses may handle the negative 324 * value differently. 325 * 326 * <p> The <code>skip</code> method implementation of this class creates a 327 * byte array and then repeatedly reads into it until <code>n</code> bytes 328 * have been read or the end of the stream has been reached. Subclasses are 329 * encouraged to provide a more efficient implementation of this method. 330 * For instance, the implementation may depend on the ability to seek. 331 * 332 * @param n the number of bytes to be skipped. 333 * @return the actual number of bytes skipped. 334 * @throws IOException if an I/O error occurs. 335 */ 336 public long skip(long n) throws IOException { 337 338 long remaining = n; 339 int nr; 340 341 if (n <= 0) { 342 return 0; 343 } 344 345 int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining); 346 byte[] skipBuffer = new byte[size]; 347 while (remaining > 0) { 348 nr = read(skipBuffer, 0, (int)Math.min(size, remaining)); 349 if (nr < 0) { 350 break; 351 } 352 remaining -= nr; 353 } 354 355 return n - remaining; 356 } 357 358 /** 359 * Returns an estimate of the number of bytes that can be read (or 360 * skipped over) from this input stream without blocking by the next 361 * invocation of a method for this input stream. The next invocation 362 * might be the same thread or another thread. A single read or skip of this 363 * many bytes will not block, but may read or skip fewer bytes. 364 * 365 * <p> Note that while some implementations of {@code InputStream} will return 366 * the total number of bytes in the stream, many will not. It is 367 * never correct to use the return value of this method to allocate 368 * a buffer intended to hold all data in this stream. 369 * 370 * <p> A subclass' implementation of this method may choose to throw an 371 * {@link IOException} if this input stream has been closed by 372 * invoking the {@link #close()} method. 373 * 374 * <p> The {@code available} method for class {@code InputStream} always 375 * returns {@code 0}. 376 * 377 * <p> This method should be overridden by subclasses. 378 * 379 * @return an estimate of the number of bytes that can be read (or skipped 380 * over) from this input stream without blocking or {@code 0} when 381 * it reaches the end of the input stream. 382 * @exception IOException if an I/O error occurs. 383 */ 384 public int available() throws IOException { 385 return 0; 386 } 387 388 /** 389 * Closes this input stream and releases any system resources associated 390 * with the stream. 391 * 392 * <p> The <code>close</code> method of <code>InputStream</code> does 393 * nothing. 394 * 395 * @exception IOException if an I/O error occurs. 396 */ 397 public void close() throws IOException {} 398 399 /** 400 * Marks the current position in this input stream. A subsequent call to 401 * the <code>reset</code> method repositions this stream at the last marked 402 * position so that subsequent reads re-read the same bytes. 403 * 404 * <p> The <code>readlimit</code> arguments tells this input stream to 405 * allow that many bytes to be read before the mark position gets 406 * invalidated. 407 * 408 * <p> The general contract of <code>mark</code> is that, if the method 409 * <code>markSupported</code> returns <code>true</code>, the stream somehow 410 * remembers all the bytes read after the call to <code>mark</code> and 411 * stands ready to supply those same bytes again if and whenever the method 412 * <code>reset</code> is called. However, the stream is not required to 413 * remember any data at all if more than <code>readlimit</code> bytes are 414 * read from the stream before <code>reset</code> is called. 415 * 416 * <p> Marking a closed stream should not have any effect on the stream. 417 * 418 * <p> The <code>mark</code> method of <code>InputStream</code> does 419 * nothing. 420 * 421 * @param readlimit the maximum limit of bytes that can be read before 422 * the mark position becomes invalid. 423 * @see java.io.InputStream#reset() 424 */ 425 public synchronized void mark(int readlimit) {} 426 427 /** 428 * Repositions this stream to the position at the time the 429 * <code>mark</code> method was last called on this input stream. 430 * 431 * <p> The general contract of <code>reset</code> is: 432 * 433 * <ul> 434 * <li> If the method <code>markSupported</code> returns 435 * <code>true</code>, then: 436 * 437 * <ul><li> If the method <code>mark</code> has not been called since 438 * the stream was created, or the number of bytes read from the stream 439 * since <code>mark</code> was last called is larger than the argument 440 * to <code>mark</code> at that last call, then an 441 * <code>IOException</code> might be thrown. 442 * 443 * <li> If such an <code>IOException</code> is not thrown, then the 444 * stream is reset to a state such that all the bytes read since the 445 * most recent call to <code>mark</code> (or since the start of the 446 * file, if <code>mark</code> has not been called) will be resupplied 447 * to subsequent callers of the <code>read</code> method, followed by 448 * any bytes that otherwise would have been the next input data as of 449 * the time of the call to <code>reset</code>. </ul> 450 * 451 * <li> If the method <code>markSupported</code> returns 452 * <code>false</code>, then: 453 * 454 * <ul><li> The call to <code>reset</code> may throw an 455 * <code>IOException</code>. 456 * 457 * <li> If an <code>IOException</code> is not thrown, then the stream 458 * is reset to a fixed state that depends on the particular type of the 459 * input stream and how it was created. The bytes that will be supplied 460 * to subsequent callers of the <code>read</code> method depend on the 461 * particular type of the input stream. </ul></ul> 462 * 463 * <p>The method <code>reset</code> for class <code>InputStream</code> 464 * does nothing except throw an <code>IOException</code>. 465 * 466 * @exception IOException if this stream has not been marked or if the 467 * mark has been invalidated. 468 * @see java.io.InputStream#mark(int) 469 * @see java.io.IOException 470 */ 471 public synchronized void reset() throws IOException { 472 throw new IOException("mark/reset not supported"); 473 } 474 475 /** 476 * Tests if this input stream supports the <code>mark</code> and 477 * <code>reset</code> methods. Whether or not <code>mark</code> and 478 * <code>reset</code> are supported is an invariant property of a 479 * particular input stream instance. The <code>markSupported</code> method 480 * of <code>InputStream</code> returns <code>false</code>. 481 * 482 * @return <code>true</code> if this stream instance supports the mark 483 * and reset methods; <code>false</code> otherwise. 484 * @see java.io.InputStream#mark(int) 485 * @see java.io.InputStream#reset() 486 */ 487 public boolean markSupported() { 488 return false; 489 } 490 491 /** 492 * Reads all bytes from this input stream and writes the bytes to the 493 * given output stream in the order that they are read. On return, this 494 * input stream will be at end of stream. This method does not close either 495 * stream. 496 * <p> 497 * This method may block indefinitely reading from the input stream, or 498 * writing to the output stream. The behavior for the case where the input 499 * and/or output stream is <i>asynchronously closed</i>, or the thread 500 * interrupted during the transfer, is highly input and output stream 501 * specific, and therefore not specified. 502 * <p> 503 * If an I/O error occurs reading from the input stream or writing to the 504 * output stream, then it may do so after some bytes have been read or 505 * written. Consequently the input stream may not be at end of stream and 506 * one, or both, streams may be in an inconsistent state. It is strongly 507 * recommended that both streams be promptly closed if an I/O error occurs. 508 * 509 * @param out the output stream, non-null 510 * @return the number of bytes transferred 511 * @throws IOException if an I/O error occurs when reading or writing 512 * @throws NullPointerException if {@code out} is {@code null} 513 * 514 * @since 9 515 */ 516 public long transferTo(OutputStream out) throws IOException { 517 Objects.requireNonNull(out, "out"); 518 long transferred = 0; 519 byte[] buffer = new byte[DEFAULT_BUFFER_SIZE]; 520 int read; 521 while ((read = this.read(buffer, 0, DEFAULT_BUFFER_SIZE)) >= 0) { 522 out.write(buffer, 0, read); 523 transferred += read; 524 } 525 return transferred; 526 } 527 }