1 /*
2 * Copyright (c) 1994, 2019, 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 * Constructor for subclasses to call.
60 */
61 public InputStream() {}
62
63 /**
64 * Returns a new {@code InputStream} that reads no bytes. The returned
65 * stream is initially open. The stream is closed by calling the
66 * {@code close()} method. Subsequent calls to {@code close()} have no
67 * effect.
68 *
69 * <p> While the stream is open, the {@code available()}, {@code read()},
70 * {@code read(byte[])}, {@code read(byte[], int, int)},
71 * {@code readAllBytes()}, {@code readNBytes(byte[], int, int)},
72 * {@code readNBytes(int)}, {@code skip(long)}, {@code skipNBytes(long)},
73 * and {@code transferTo()} methods all behave as if end of stream has been
74 * reached. After the stream has been closed, these methods all throw
75 * {@code IOException}.
76 *
77 * <p> The {@code markSupported()} method returns {@code false}. The
78 * {@code mark()} method does nothing, and the {@code reset()} method
79 * throws {@code IOException}.
80 *
81 * @return an {@code InputStream} which contains no bytes
82 *
83 * @since 11
84 */
85 public static InputStream nullInputStream() {
86 return new InputStream() {
87 private volatile boolean closed;
88
89 private void ensureOpen() throws IOException {
90 if (closed) {
91 throw new IOException("Stream closed");
92 }
93 }
94
95 @Override
96 public int available () throws IOException {
97 ensureOpen();
98 return 0;
99 }
100
101 @Override
102 public int read() throws IOException {
103 ensureOpen();
104 return -1;
105 }
106
107 @Override
108 public int read(byte[] b, int off, int len) throws IOException {
109 Objects.checkFromIndexSize(off, len, b.length);
110 if (len == 0) {
111 return 0;
112 }
113 ensureOpen();
114 return -1;
115 }
116
117 @Override
118 public byte[] readAllBytes() throws IOException {
119 ensureOpen();
120 return new byte[0];
121 }
122
123 @Override
124 public int readNBytes(byte[] b, int off, int len)
125 throws IOException {
126 Objects.checkFromIndexSize(off, len, b.length);
127 ensureOpen();
128 return 0;
129 }
130
131 @Override
132 public byte[] readNBytes(int len) throws IOException {
133 if (len < 0) {
134 throw new IllegalArgumentException("len < 0");
135 }
136 ensureOpen();
137 return new byte[0];
138 }
139
140 @Override
141 public long skip(long n) throws IOException {
142 ensureOpen();
143 return 0L;
144 }
145
146 @Override
147 public void skipNBytes(long n) throws IOException {
148 ensureOpen();
149 if (n > 0) {
150 throw new EOFException();
151 }
152 }
153
154 @Override
155 public long transferTo(OutputStream out) throws IOException {
156 Objects.requireNonNull(out);
157 ensureOpen();
158 return 0L;
159 }
160
161 @Override
162 public void close() throws IOException {
163 closed = true;
164 }
165 };
166 }
167
168 /**
169 * Reads the next byte of data from the input stream. The value byte is
170 * returned as an <code>int</code> in the range <code>0</code> to
171 * <code>255</code>. If no byte is available because the end of the stream
172 * has been reached, the value <code>-1</code> is returned. This method
173 * blocks until input data is available, the end of the stream is detected,
174 * or an exception is thrown.
175 *
176 * <p> A subclass must provide an implementation of this method.
177 *
178 * @return the next byte of data, or <code>-1</code> if the end of the
179 * stream is reached.
180 * @exception IOException if an I/O error occurs.
181 */
182 public abstract int read() throws IOException;
183
184 /**
185 * Reads some number of bytes from the input stream and stores them into
186 * the buffer array <code>b</code>. The number of bytes actually read is
187 * returned as an integer. This method blocks until input data is
188 * available, end of file is detected, or an exception is thrown.
189 *
190 * <p> If the length of <code>b</code> is zero, then no bytes are read and
191 * <code>0</code> is returned; otherwise, there is an attempt to read at
192 * least one byte. If no byte is available because the stream is at the
193 * end of the file, the value <code>-1</code> is returned; otherwise, at
194 * least one byte is read and stored into <code>b</code>.
195 *
196 * <p> The first byte read is stored into element <code>b[0]</code>, the
197 * next one into <code>b[1]</code>, and so on. The number of bytes read is,
198 * at most, equal to the length of <code>b</code>. Let <i>k</i> be the
199 * number of bytes actually read; these bytes will be stored in elements
200 * <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>,
201 * leaving elements <code>b[</code><i>k</i><code>]</code> through
202 * <code>b[b.length-1]</code> unaffected.
203 *
204 * <p> The <code>read(b)</code> method for class <code>InputStream</code>
205 * has the same effect as: <pre><code> read(b, 0, b.length) </code></pre>
206 *
207 * @param b the buffer into which the data is read.
208 * @return the total number of bytes read into the buffer, or
209 * <code>-1</code> if there is no more data because the end of
210 * the stream has been reached.
211 * @exception IOException If the first byte cannot be read for any reason
212 * other than the end of the file, if the input stream has been closed, or
213 * if some other I/O error occurs.
214 * @exception NullPointerException if <code>b</code> is <code>null</code>.
215 * @see java.io.InputStream#read(byte[], int, int)
216 */
217 public int read(byte b[]) throws IOException {
218 return read(b, 0, b.length);
219 }
220
221 /**
222 * Reads up to <code>len</code> bytes of data from the input stream into
223 * an array of bytes. An attempt is made to read as many as
224 * <code>len</code> bytes, but a smaller number may be read.
225 * The number of bytes actually read is returned as an integer.
226 *
227 * <p> This method blocks until input data is available, end of file is
228 * detected, or an exception is thrown.
229 *
230 * <p> If <code>len</code> is zero, then no bytes are read and
231 * <code>0</code> is returned; otherwise, there is an attempt to read at
232 * least one byte. If no byte is available because the stream is at end of
233 * file, the value <code>-1</code> is returned; otherwise, at least one
234 * byte is read and stored into <code>b</code>.
235 *
236 * <p> The first byte read is stored into element <code>b[off]</code>, the
237 * next one into <code>b[off+1]</code>, and so on. The number of bytes read
238 * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
239 * bytes actually read; these bytes will be stored in elements
240 * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
241 * leaving elements <code>b[off+</code><i>k</i><code>]</code> through
242 * <code>b[off+len-1]</code> unaffected.
243 *
244 * <p> In every case, elements <code>b[0]</code> through
245 * <code>b[off-1]</code> and elements <code>b[off+len]</code> through
246 * <code>b[b.length-1]</code> are unaffected.
247 *
248 * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method
249 * for class <code>InputStream</code> simply calls the method
250 * <code>read()</code> repeatedly. If the first such call results in an
251 * <code>IOException</code>, that exception is returned from the call to
252 * the <code>read(b,</code> <code>off,</code> <code>len)</code> method. If
253 * any subsequent call to <code>read()</code> results in a
254 * <code>IOException</code>, the exception is caught and treated as if it
255 * were end of file; the bytes read up to that point are stored into
256 * <code>b</code> and the number of bytes read before the exception
257 * occurred is returned. The default implementation of this method blocks
258 * until the requested amount of input data <code>len</code> has been read,
259 * end of file is detected, or an exception is thrown. Subclasses are
260 * encouraged to provide a more efficient implementation of this method.
261 *
262 * @param b the buffer into which the data is read.
263 * @param off the start offset in array <code>b</code>
264 * at which the data is written.
265 * @param len the maximum number of bytes to read.
266 * @return the total number of bytes read into the buffer, or
267 * <code>-1</code> if there is no more data because the end of
268 * the stream has been reached.
269 * @exception IOException If the first byte cannot be read for any reason
270 * other than end of file, or if the input stream has been closed, or if
271 * some other I/O error occurs.
272 * @exception NullPointerException If <code>b</code> is <code>null</code>.
273 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
274 * <code>len</code> is negative, or <code>len</code> is greater than
275 * <code>b.length - off</code>
276 * @see java.io.InputStream#read()
277 */
278 public int read(byte b[], int off, int len) throws IOException {
279 Objects.checkFromIndexSize(off, len, b.length);
280 if (len == 0) {
281 return 0;
282 }
283
284 int c = read();
285 if (c == -1) {
286 return -1;
287 }
288 b[off] = (byte)c;
289
290 int i = 1;
291 try {
292 for (; i < len ; i++) {
293 c = read();
294 if (c == -1) {
295 break;
296 }
297 b[off + i] = (byte)c;
298 }
299 } catch (IOException ee) {
300 }
301 return i;
302 }
303
304 /**
305 * The maximum size of array to allocate.
306 * Some VMs reserve some header words in an array.
307 * Attempts to allocate larger arrays may result in
308 * OutOfMemoryError: Requested array size exceeds VM limit
309 */
310 private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
311
312 /**
313 * Reads all remaining bytes from the input stream. This method blocks until
314 * all remaining bytes have been read and end of stream is detected, or an
315 * exception is thrown. This method does not close the input stream.
316 *
317 * <p> When this stream reaches end of stream, further invocations of this
318 * method will return an empty byte array.
319 *
320 * <p> Note that this method is intended for simple cases where it is
321 * convenient to read all bytes into a byte array. It is not intended for
322 * reading input streams with large amounts of data.
323 *
324 * <p> The behavior for the case where the input stream is <i>asynchronously
325 * closed</i>, or the thread interrupted during the read, is highly input
326 * stream specific, and therefore not specified.
327 *
328 * <p> If an I/O error occurs reading from the input stream, then it may do
329 * so after some, but not all, bytes have been read. Consequently the input
330 * stream may not be at end of stream and may be in an inconsistent state.
331 * It is strongly recommended that the stream be promptly closed if an I/O
332 * error occurs.
333 *
334 * @implSpec
335 * This method invokes {@link #readNBytes(int)} with a length of
336 * {@link Integer#MAX_VALUE}.
337 *
338 * @return a byte array containing the bytes read from this input stream
339 * @throws IOException if an I/O error occurs
340 * @throws OutOfMemoryError if an array of the required size cannot be
341 * allocated.
342 *
343 * @since 9
344 */
345 public byte[] readAllBytes() throws IOException {
346 return readNBytes(Integer.MAX_VALUE);
347 }
348
349 /**
350 * Reads up to a specified number of bytes from the input stream. This
351 * method blocks until the requested number of bytes have been read, end
352 * of stream is detected, or an exception is thrown. This method does not
353 * close the input stream.
354 *
355 * <p> The length of the returned array equals the number of bytes read
356 * from the stream. If {@code len} is zero, then no bytes are read and
357 * an empty byte array is returned. Otherwise, up to {@code len} bytes
358 * are read from the stream. Fewer than {@code len} bytes may be read if
359 * end of stream is encountered.
360 *
361 * <p> When this stream reaches end of stream, further invocations of this
362 * method will return an empty byte array.
363 *
364 * <p> Note that this method is intended for simple cases where it is
365 * convenient to read the specified number of bytes into a byte array. The
366 * total amount of memory allocated by this method is proportional to the
367 * number of bytes read from the stream which is bounded by {@code len}.
368 * Therefore, the method may be safely called with very large values of
369 * {@code len} provided sufficient memory is available.
370 *
371 * <p> The behavior for the case where the input stream is <i>asynchronously
372 * closed</i>, or the thread interrupted during the read, is highly input
373 * stream specific, and therefore not specified.
374 *
375 * <p> If an I/O error occurs reading from the input stream, then it may do
376 * so after some, but not all, bytes have been read. Consequently the input
377 * stream may not be at end of stream and may be in an inconsistent state.
378 * It is strongly recommended that the stream be promptly closed if an I/O
379 * error occurs.
380 *
381 * @implNote
382 * The number of bytes allocated to read data from this stream and return
383 * the result is bounded by {@code 2*(long)len}, inclusive.
384 *
385 * @param len the maximum number of bytes to read
386 * @return a byte array containing the bytes read from this input stream
387 * @throws IllegalArgumentException if {@code length} is negative
388 * @throws IOException if an I/O error occurs
389 * @throws OutOfMemoryError if an array of the required size cannot be
390 * allocated.
391 *
392 * @since 11
393 */
394 public byte[] readNBytes(int len) throws IOException {
395 if (len < 0) {
396 throw new IllegalArgumentException("len < 0");
397 }
398
399 List<byte[]> bufs = null;
400 byte[] result = null;
401 int total = 0;
402 int remaining = len;
403 int n;
404 do {
405 byte[] buf = new byte[Math.min(remaining, DEFAULT_BUFFER_SIZE)];
406 int nread = 0;
407
408 // read to EOF which may read more or less than buffer size
409 while ((n = read(buf, nread,
410 Math.min(buf.length - nread, remaining))) > 0) {
411 nread += n;
412 remaining -= n;
413 }
414
415 if (nread > 0) {
416 if (MAX_BUFFER_SIZE - total < nread) {
417 throw new OutOfMemoryError("Required array size too large");
418 }
419 total += nread;
420 if (result == null) {
421 result = buf;
422 } else {
423 if (bufs == null) {
424 bufs = new ArrayList<>();
425 bufs.add(result);
426 }
427 bufs.add(buf);
428 }
429 }
430 // if the last call to read returned -1 or the number of bytes
431 // requested have been read then break
432 } while (n >= 0 && remaining > 0);
433
434 if (bufs == null) {
435 if (result == null) {
436 return new byte[0];
437 }
438 return result.length == total ?
439 result : Arrays.copyOf(result, total);
440 }
441
442 result = new byte[total];
443 int offset = 0;
444 remaining = total;
445 for (byte[] b : bufs) {
446 int count = Math.min(b.length, remaining);
447 System.arraycopy(b, 0, result, offset, count);
448 offset += count;
449 remaining -= count;
450 }
451
452 return result;
453 }
454
455 /**
456 * Reads the requested number of bytes from the input stream into the given
457 * byte array. This method blocks until {@code len} bytes of input data have
458 * been read, end of stream is detected, or an exception is thrown. The
459 * number of bytes actually read, possibly zero, is returned. This method
460 * does not close the input stream.
461 *
462 * <p> In the case where end of stream is reached before {@code len} bytes
463 * have been read, then the actual number of bytes read will be returned.
464 * When this stream reaches end of stream, further invocations of this
465 * method will return zero.
466 *
467 * <p> If {@code len} is zero, then no bytes are read and {@code 0} is
468 * returned; otherwise, there is an attempt to read up to {@code len} bytes.
469 *
470 * <p> The first byte read is stored into element {@code b[off]}, the next
471 * one in to {@code b[off+1]}, and so on. The number of bytes read is, at
472 * most, equal to {@code len}. Let <i>k</i> be the number of bytes actually
473 * read; these bytes will be stored in elements {@code b[off]} through
474 * {@code b[off+}<i>k</i>{@code -1]}, leaving elements {@code b[off+}<i>k</i>
475 * {@code ]} through {@code b[off+len-1]} unaffected.
476 *
477 * <p> The behavior for the case where the input stream is <i>asynchronously
478 * closed</i>, or the thread interrupted during the read, is highly input
479 * stream specific, and therefore not specified.
480 *
481 * <p> If an I/O error occurs reading from the input stream, then it may do
482 * so after some, but not all, bytes of {@code b} have been updated with
483 * data from the input stream. Consequently the input stream and {@code b}
484 * may be in an inconsistent state. It is strongly recommended that the
485 * stream be promptly closed if an I/O error occurs.
486 *
487 * @param b the byte array into which the data is read
488 * @param off the start offset in {@code b} at which the data is written
489 * @param len the maximum number of bytes to read
490 * @return the actual number of bytes read into the buffer
491 * @throws IOException if an I/O error occurs
492 * @throws NullPointerException if {@code b} is {@code null}
493 * @throws IndexOutOfBoundsException If {@code off} is negative, {@code len}
494 * is negative, or {@code len} is greater than {@code b.length - off}
495 *
496 * @since 9
497 */
498 public int readNBytes(byte[] b, int off, int len) throws IOException {
499 Objects.checkFromIndexSize(off, len, b.length);
500
501 int n = 0;
502 while (n < len) {
503 int count = read(b, off + n, len - n);
504 if (count < 0)
505 break;
506 n += count;
507 }
508 return n;
509 }
510
511 /**
512 * Skips over and discards <code>n</code> bytes of data from this input
513 * stream. The <code>skip</code> method may, for a variety of reasons, end
514 * up skipping over some smaller number of bytes, possibly <code>0</code>.
515 * This may result from any of a number of conditions; reaching end of file
516 * before <code>n</code> bytes have been skipped is only one possibility.
517 * The actual number of bytes skipped is returned. If {@code n} is
518 * negative, the {@code skip} method for class {@code InputStream} always
519 * returns 0, and no bytes are skipped. Subclasses may handle the negative
520 * value differently.
521 *
522 * <p> The <code>skip</code> method implementation of this class creates a
523 * byte array and then repeatedly reads into it until <code>n</code> bytes
524 * have been read or the end of the stream has been reached. Subclasses are
525 * encouraged to provide a more efficient implementation of this method.
526 * For instance, the implementation may depend on the ability to seek.
527 *
528 * @param n the number of bytes to be skipped.
529 * @return the actual number of bytes skipped which might be zero.
530 * @throws IOException if an I/O error occurs.
531 * @see java.io.InputStream#skipNBytes(long)
532 */
533 public long skip(long n) throws IOException {
534 long remaining = n;
535 int nr;
536
537 if (n <= 0) {
538 return 0;
539 }
540
541 int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining);
542 byte[] skipBuffer = new byte[size];
543 while (remaining > 0) {
544 nr = read(skipBuffer, 0, (int)Math.min(size, remaining));
545 if (nr < 0) {
546 break;
547 }
548 remaining -= nr;
549 }
550
551 return n - remaining;
552 }
553
554 /**
555 * Skips over and discards exactly {@code n} bytes of data from this input
556 * stream. If {@code n} is zero, then no bytes are skipped.
557 * If {@code n} is negative, then no bytes are skipped.
558 * Subclasses may handle the negative value differently.
559 *
560 * <p> This method blocks until the requested number of bytes have been
561 * skipped, end of file is reached, or an exception is thrown.
562 *
563 * <p> If end of stream is reached before the stream is at the desired
564 * position, then an {@code EOFException} is thrown.
565 *
566 * <p> If an I/O error occurs, then the input stream may be
567 * in an inconsistent state. It is strongly recommended that the
568 * stream be promptly closed if an I/O error occurs.
569 *
570 * @implNote
571 * Subclasses are encouraged to provide a more efficient implementation
572 * of this method.
573 *
574 * @implSpec
575 * If {@code n} is zero or negative, then no bytes are skipped.
576 * If {@code n} is positive, the default implementation of this method
577 * invokes {@link #skip(long) skip()} with parameter {@code n}. If the
578 * return value of {@code skip(n)} is non-negative and less than {@code n},
579 * then {@link #read()} is invoked repeatedly until the stream is {@code n}
580 * bytes beyond its position when this method was invoked or end of stream
581 * is reached. If the return value of {@code skip(n)} is negative or
582 * greater than {@code n}, then an {@code IOException} is thrown. Any
583 * exception thrown by {@code skip()} or {@code read()} will be propagated.
584 *
585 * @param n the number of bytes to be skipped.
586 * @throws EOFException if end of stream is encountered before the
587 * stream can be positioned {@code n} bytes beyond its position
588 * when this method was invoked.
589 * @throws IOException if the stream cannot be positioned properly or
590 * if an I/O error occurs.
591 * @see java.io.InputStream#skip(long)
592 */
593 public void skipNBytes(long n) throws IOException {
594 if (n > 0) {
595 long ns = skip(n);
596 if (ns >= 0 && ns < n) { // skipped too few bytes
597 // adjust number to skip
598 n -= ns;
599 // read until requested number skipped or EOS reached
600 while (n > 0 && read() != -1) {
601 n--;
602 }
603 // if not enough skipped, then EOFE
604 if (n != 0) {
605 throw new EOFException();
606 }
607 } else if (ns != n) { // skipped negative or too many bytes
608 throw new IOException("Unable to skip exactly");
609 }
610 }
611 }
612
613 /**
614 * Returns an estimate of the number of bytes that can be read (or skipped
615 * over) from this input stream without blocking, which may be 0, or 0 when
616 * end of stream is detected. The read might be on the same thread or
617 * another thread. A single read or skip of this many bytes will not block,
618 * but may read or skip fewer bytes.
619 *
620 * <p> Note that while some implementations of {@code InputStream} will
621 * return the total number of bytes in the stream, many will not. It is
622 * never correct to use the return value of this method to allocate
623 * a buffer intended to hold all data in this stream.
624 *
625 * <p> A subclass's implementation of this method may choose to throw an
626 * {@link IOException} if this input stream has been closed by invoking the
627 * {@link #close()} method.
628 *
629 * <p> The {@code available} method of {@code InputStream} always returns
630 * {@code 0}.
631 *
632 * <p> This method should be overridden by subclasses.
633 *
634 * @return an estimate of the number of bytes that can be read (or
635 * skipped over) from this input stream without blocking or
636 * {@code 0} when it reaches the end of the input stream.
637 * @exception IOException if an I/O error occurs.
638 */
639 public int available() throws IOException {
640 return 0;
641 }
642
643 /**
644 * Closes this input stream and releases any system resources associated
645 * with the stream.
646 *
647 * <p> The <code>close</code> method of <code>InputStream</code> does
648 * nothing.
649 *
650 * @exception IOException if an I/O error occurs.
651 */
652 public void close() throws IOException {}
653
654 /**
655 * Marks the current position in this input stream. A subsequent call to
656 * the <code>reset</code> method repositions this stream at the last marked
657 * position so that subsequent reads re-read the same bytes.
658 *
659 * <p> The <code>readlimit</code> arguments tells this input stream to
660 * allow that many bytes to be read before the mark position gets
661 * invalidated.
662 *
663 * <p> The general contract of <code>mark</code> is that, if the method
664 * <code>markSupported</code> returns <code>true</code>, the stream somehow
665 * remembers all the bytes read after the call to <code>mark</code> and
666 * stands ready to supply those same bytes again if and whenever the method
667 * <code>reset</code> is called. However, the stream is not required to
668 * remember any data at all if more than <code>readlimit</code> bytes are
669 * read from the stream before <code>reset</code> is called.
670 *
671 * <p> Marking a closed stream should not have any effect on the stream.
672 *
673 * <p> The <code>mark</code> method of <code>InputStream</code> does
674 * nothing.
675 *
676 * @param readlimit the maximum limit of bytes that can be read before
677 * the mark position becomes invalid.
678 * @see java.io.InputStream#reset()
679 */
680 public synchronized void mark(int readlimit) {}
681
682 /**
683 * Repositions this stream to the position at the time the
684 * <code>mark</code> method was last called on this input stream.
685 *
686 * <p> The general contract of <code>reset</code> is:
687 *
688 * <ul>
689 * <li> If the method <code>markSupported</code> returns
690 * <code>true</code>, then:
691 *
692 * <ul><li> If the method <code>mark</code> has not been called since
693 * the stream was created, or the number of bytes read from the stream
694 * since <code>mark</code> was last called is larger than the argument
695 * to <code>mark</code> at that last call, then an
696 * <code>IOException</code> might be thrown.
697 *
698 * <li> If such an <code>IOException</code> is not thrown, then the
699 * stream is reset to a state such that all the bytes read since the
700 * most recent call to <code>mark</code> (or since the start of the
701 * file, if <code>mark</code> has not been called) will be resupplied
702 * to subsequent callers of the <code>read</code> method, followed by
703 * any bytes that otherwise would have been the next input data as of
704 * the time of the call to <code>reset</code>. </ul>
705 *
706 * <li> If the method <code>markSupported</code> returns
707 * <code>false</code>, then:
708 *
709 * <ul><li> The call to <code>reset</code> may throw an
710 * <code>IOException</code>.
711 *
712 * <li> If an <code>IOException</code> is not thrown, then the stream
713 * is reset to a fixed state that depends on the particular type of the
714 * input stream and how it was created. The bytes that will be supplied
715 * to subsequent callers of the <code>read</code> method depend on the
716 * particular type of the input stream. </ul></ul>
717 *
718 * <p>The method <code>reset</code> for class <code>InputStream</code>
719 * does nothing except throw an <code>IOException</code>.
720 *
721 * @exception IOException if this stream has not been marked or if the
722 * mark has been invalidated.
723 * @see java.io.InputStream#mark(int)
724 * @see java.io.IOException
725 */
726 public synchronized void reset() throws IOException {
727 throw new IOException("mark/reset not supported");
728 }
729
730 /**
731 * Tests if this input stream supports the <code>mark</code> and
732 * <code>reset</code> methods. Whether or not <code>mark</code> and
733 * <code>reset</code> are supported is an invariant property of a
734 * particular input stream instance. The <code>markSupported</code> method
735 * of <code>InputStream</code> returns <code>false</code>.
736 *
737 * @return <code>true</code> if this stream instance supports the mark
738 * and reset methods; <code>false</code> otherwise.
739 * @see java.io.InputStream#mark(int)
740 * @see java.io.InputStream#reset()
741 */
742 public boolean markSupported() {
743 return false;
744 }
745
746 /**
747 * Reads all bytes from this input stream and writes the bytes to the
748 * given output stream in the order that they are read. On return, this
749 * input stream will be at end of stream. This method does not close either
750 * stream.
751 * <p>
752 * This method may block indefinitely reading from the input stream, or
753 * writing to the output stream. The behavior for the case where the input
754 * and/or output stream is <i>asynchronously closed</i>, or the thread
755 * interrupted during the transfer, is highly input and output stream
756 * specific, and therefore not specified.
757 * <p>
758 * If an I/O error occurs reading from the input stream or writing to the
759 * output stream, then it may do so after some bytes have been read or
760 * written. Consequently the input stream may not be at end of stream and
761 * one, or both, streams may be in an inconsistent state. It is strongly
762 * recommended that both streams be promptly closed if an I/O error occurs.
763 *
764 * @param out the output stream, non-null
765 * @return the number of bytes transferred
766 * @throws IOException if an I/O error occurs when reading or writing
767 * @throws NullPointerException if {@code out} is {@code null}
768 *
769 * @since 9
770 */
771 public long transferTo(OutputStream out) throws IOException {
772 Objects.requireNonNull(out, "out");
773 long transferred = 0;
774 byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
775 int read;
776 while ((read = this.read(buffer, 0, DEFAULT_BUFFER_SIZE)) >= 0) {
777 out.write(buffer, 0, read);
778 transferred += read;
779 }
780 return transferred;
781 }
782 }