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 * Returns a new {@code InputStream} that contains no bytes. The returned
58 * stream is initially open. The stream is closed by calling the
59 * {@code close()} method. Subsequent calls to {@code close()} have no
60 * effect.
61 *
62 * <p> While the stream is open, the {@code available()}, {@code read()},
63 * {@code read(byte[])}, {@code read(byte[], int, int)},
64 * {@code readAllBytes()}, {@code readNBytes()}, {@code skip()}, and
65 * {@code transferTo()} methods all behave as if end of stream has been
66 * reached. After the stream has been closed, these methods all throw
67 * {@code IOException}.
68 *
69 * <p> The {@code markSupported()} method returns {@code false}. The
70 * {@code mark()} method does nothing, and the {@code reset()} method
71 * throws {@code IOException}.
72 *
73 * @return an {@code InputStream} which contains no bytes
74 *
75 * @since 10
76 */
77 public static InputStream nullStream() {
78 return new InputStream() {
79 private volatile boolean closed;
80
81 private void ensureOpen() throws IOException {
82 if (closed) {
83 throw new IOException("Stream closed");
84 }
85 }
86
87 @Override
88 public int available () throws IOException {
89 ensureOpen();
90 return 0;
91 }
92
93 @Override
94 public int read() throws IOException {
95 ensureOpen();
96 return -1;
97 }
98
99 @Override
100 public int read(byte[] b, int off, int len) throws IOException {
101 Objects.requireNonNull(b);
102 Objects.checkFromIndexSize(off, len, b.length);
103 if (len == 0) {
104 return 0;
105 }
106 ensureOpen();
107 return -1;
108 }
109
110 @Override
111 // overridden for efficiency
112 public byte[] readAllBytes() throws IOException {
113 ensureOpen();
114 return new byte[0];
115 }
116
117 @Override
118 // overridden for efficiency
119 public int readNBytes(byte[] b, int off, int len)
120 throws IOException {
121 Objects.requireNonNull(b);
122 Objects.checkFromIndexSize(off, len, b.length);
123 ensureOpen();
124 return 0;
125 }
126
127 @Override
128 // overridden for efficiency
129 public long skip(long n) throws IOException {
130 ensureOpen();
131 return 0L;
132 }
133
134 @Override
135 // overridden for efficiency
136 public long transferTo(OutputStream out) throws IOException {
137 Objects.requireNonNull(out);
138 ensureOpen();
139 return 0L;
140 }
141
142 @Override
143 public void close() throws IOException {
144 closed = true;
145 }
146 };
147 }
148
149 /**
150 * Reads the next byte of data from the input stream. The value byte is
151 * returned as an <code>int</code> in the range <code>0</code> to
152 * <code>255</code>. If no byte is available because the end of the stream
153 * has been reached, the value <code>-1</code> is returned. This method
154 * blocks until input data is available, the end of the stream is detected,
155 * or an exception is thrown.
156 *
157 * <p> A subclass must provide an implementation of this method.
158 *
159 * @return the next byte of data, or <code>-1</code> if the end of the
160 * stream is reached.
161 * @exception IOException if an I/O error occurs.
162 */
163 public abstract int read() throws IOException;
164
165 /**
166 * Reads some number of bytes from the input stream and stores them into
167 * the buffer array <code>b</code>. The number of bytes actually read is
168 * returned as an integer. This method blocks until input data is
169 * available, end of file is detected, or an exception is thrown.
170 *
171 * <p> If the length of <code>b</code> is zero, then no bytes are read and
172 * <code>0</code> is returned; otherwise, there is an attempt to read at
173 * least one byte. If no byte is available because the stream is at the
174 * end of the file, the value <code>-1</code> is returned; otherwise, at
175 * least one byte is read and stored into <code>b</code>.
176 *
177 * <p> The first byte read is stored into element <code>b[0]</code>, the
178 * next one into <code>b[1]</code>, and so on. The number of bytes read is,
179 * at most, equal to the length of <code>b</code>. Let <i>k</i> be the
180 * number of bytes actually read; these bytes will be stored in elements
181 * <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>,
182 * leaving elements <code>b[</code><i>k</i><code>]</code> through
183 * <code>b[b.length-1]</code> unaffected.
184 *
185 * <p> The <code>read(b)</code> method for class <code>InputStream</code>
186 * has the same effect as: <pre><code> read(b, 0, b.length) </code></pre>
187 *
188 * @param b the buffer into which the data is read.
189 * @return the total number of bytes read into the buffer, or
190 * <code>-1</code> if there is no more data because the end of
191 * the stream has been reached.
192 * @exception IOException If the first byte cannot be read for any reason
193 * other than the end of the file, if the input stream has been closed, or
194 * if some other I/O error occurs.
195 * @exception NullPointerException if <code>b</code> is <code>null</code>.
196 * @see java.io.InputStream#read(byte[], int, int)
197 */
198 public int read(byte b[]) throws IOException {
199 return read(b, 0, b.length);
200 }
201
202 /**
203 * Reads up to <code>len</code> bytes of data from the input stream into
204 * an array of bytes. An attempt is made to read as many as
205 * <code>len</code> bytes, but a smaller number may be read.
206 * The number of bytes actually read is returned as an integer.
207 *
208 * <p> This method blocks until input data is available, end of file is
209 * detected, or an exception is thrown.
210 *
211 * <p> If <code>len</code> is zero, then no bytes are read and
212 * <code>0</code> is returned; otherwise, there is an attempt to read at
213 * least one byte. If no byte is available because the stream is at end of
214 * file, the value <code>-1</code> is returned; otherwise, at least one
215 * byte is read and stored into <code>b</code>.
216 *
217 * <p> The first byte read is stored into element <code>b[off]</code>, the
218 * next one into <code>b[off+1]</code>, and so on. The number of bytes read
219 * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
220 * bytes actually read; these bytes will be stored in elements
221 * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
222 * leaving elements <code>b[off+</code><i>k</i><code>]</code> through
223 * <code>b[off+len-1]</code> unaffected.
224 *
225 * <p> In every case, elements <code>b[0]</code> through
226 * <code>b[off]</code> and elements <code>b[off+len]</code> through
227 * <code>b[b.length-1]</code> are unaffected.
228 *
229 * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method
230 * for class <code>InputStream</code> simply calls the method
231 * <code>read()</code> repeatedly. If the first such call results in an
232 * <code>IOException</code>, that exception is returned from the call to
233 * the <code>read(b,</code> <code>off,</code> <code>len)</code> method. If
234 * any subsequent call to <code>read()</code> results in a
235 * <code>IOException</code>, the exception is caught and treated as if it
236 * were end of file; the bytes read up to that point are stored into
237 * <code>b</code> and the number of bytes read before the exception
238 * occurred is returned. The default implementation of this method blocks
239 * until the requested amount of input data <code>len</code> has been read,
240 * end of file is detected, or an exception is thrown. Subclasses are encouraged
241 * to provide a more efficient implementation of this method.
242 *
243 * @param b the buffer into which the data is read.
244 * @param off the start offset in array <code>b</code>
245 * at which the data is written.
246 * @param len the maximum number of bytes to read.
247 * @return the total number of bytes read into the buffer, or
248 * <code>-1</code> if there is no more data because the end of
249 * the stream has been reached.
250 * @exception IOException If the first byte cannot be read for any reason
251 * other than end of file, or if the input stream has been closed, or if
252 * some other I/O error occurs.
253 * @exception NullPointerException If <code>b</code> is <code>null</code>.
254 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
255 * <code>len</code> is negative, or <code>len</code> is greater than
256 * <code>b.length - off</code>
257 * @see java.io.InputStream#read()
258 */
259 public int read(byte b[], int off, int len) throws IOException {
260 Objects.requireNonNull(b);
261 Objects.checkFromIndexSize(off, len, b.length);
262 if (len == 0) {
263 return 0;
264 }
265
266 int c = read();
267 if (c == -1) {
268 return -1;
269 }
270 b[off] = (byte)c;
271
272 int i = 1;
273 try {
274 for (; i < len ; i++) {
275 c = read();
276 if (c == -1) {
277 break;
278 }
279 b[off + i] = (byte)c;
280 }
281 } catch (IOException ee) {
282 }
283 return i;
284 }
285
286 /**
287 * The maximum size of array to allocate.
288 * Some VMs reserve some header words in an array.
289 * Attempts to allocate larger arrays may result in
290 * OutOfMemoryError: Requested array size exceeds VM limit
291 */
292 private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
293
294 /**
295 * Reads all remaining bytes from the input stream. This method blocks until
296 * all remaining bytes have been read and end of stream is detected, or an
297 * exception is thrown. This method does not close the input stream.
298 *
299 * <p> When this stream reaches end of stream, further invocations of this
300 * method will return an empty byte array.
301 *
302 * <p> Note that this method is intended for simple cases where it is
303 * convenient to read all bytes into a byte array. It is not intended for
304 * reading input streams with large amounts of data.
305 *
306 * <p> The behavior for the case where the input stream is <i>asynchronously
307 * closed</i>, or the thread interrupted during the read, is highly input
308 * stream specific, and therefore not specified.
309 *
310 * <p> If an I/O error occurs reading from the input stream, then it may do
311 * so after some, but not all, bytes have been read. Consequently the input
312 * stream may not be at end of stream and may be in an inconsistent state.
313 * It is strongly recommended that the stream be promptly closed if an I/O
314 * error occurs.
315 *
316 * @return a byte array containing the bytes read from this input stream
317 * @throws IOException if an I/O error occurs
318 * @throws OutOfMemoryError if an array of the required size cannot be
319 * allocated. For example, if an array larger than {@code 2GB} would
320 * be required to store the bytes.
321 *
322 * @since 9
323 */
324 public byte[] readAllBytes() throws IOException {
325 byte[] buf = new byte[DEFAULT_BUFFER_SIZE];
326 int capacity = buf.length;
327 int nread = 0;
328 int n;
329 for (;;) {
330 // read to EOF which may read more or less than initial buffer size
331 while ((n = read(buf, nread, capacity - nread)) > 0)
332 nread += n;
333
334 // if the last call to read returned -1, then we're done
335 if (n < 0)
336 break;
337
338 // need to allocate a larger buffer
339 if (capacity <= MAX_BUFFER_SIZE - capacity) {
340 capacity = capacity << 1;
341 } else {
342 if (capacity == MAX_BUFFER_SIZE)
343 throw new OutOfMemoryError("Required array size too large");
344 capacity = MAX_BUFFER_SIZE;
345 }
346 buf = Arrays.copyOf(buf, capacity);
347 }
348 return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
349 }
350
351 /**
352 * Reads the requested number of bytes from the input stream into the given
353 * byte array. This method blocks until {@code len} bytes of input data have
354 * been read, end of stream is detected, or an exception is thrown. The
355 * number of bytes actually read, possibly zero, is returned. This method
356 * does not close the input stream.
357 *
358 * <p> In the case where end of stream is reached before {@code len} bytes
359 * have been read, then the actual number of bytes read will be returned.
360 * When this stream reaches end of stream, further invocations of this
361 * method will return zero.
362 *
363 * <p> If {@code len} is zero, then no bytes are read and {@code 0} is
364 * returned; otherwise, there is an attempt to read up to {@code len} bytes.
365 *
366 * <p> The first byte read is stored into element {@code b[off]}, the next
367 * one in to {@code b[off+1]}, and so on. The number of bytes read is, at
368 * most, equal to {@code len}. Let <i>k</i> be the number of bytes actually
369 * read; these bytes will be stored in elements {@code b[off]} through
370 * {@code b[off+}<i>k</i>{@code -1]}, leaving elements {@code b[off+}<i>k</i>
371 * {@code ]} through {@code b[off+len-1]} unaffected.
372 *
373 * <p> The behavior for the case where the input stream is <i>asynchronously
374 * closed</i>, or the thread interrupted during the read, is highly input
375 * stream specific, and therefore not specified.
376 *
377 * <p> If an I/O error occurs reading from the input stream, then it may do
378 * so after some, but not all, bytes of {@code b} have been updated with
379 * data from the input stream. Consequently the input stream and {@code b}
380 * may be in an inconsistent state. It is strongly recommended that the
381 * stream be promptly closed if an I/O error occurs.
382 *
383 * @param b the byte array into which the data is read
384 * @param off the start offset in {@code b} at which the data is written
385 * @param len the maximum number of bytes to read
386 * @return the actual number of bytes read into the buffer
387 * @throws IOException if an I/O error occurs
388 * @throws NullPointerException if {@code b} is {@code null}
389 * @throws IndexOutOfBoundsException If {@code off} is negative, {@code len}
390 * is negative, or {@code len} is greater than {@code b.length - off}
391 *
392 * @since 9
393 */
394 public int readNBytes(byte[] b, int off, int len) throws IOException {
395 Objects.requireNonNull(b);
396 Objects.checkFromIndexSize(off, len, b.length);
397
398 int n = 0;
399 while (n < len) {
400 int count = read(b, off + n, len - n);
401 if (count < 0)
402 break;
403 n += count;
404 }
405 return n;
406 }
407
408 /**
409 * Skips over and discards <code>n</code> bytes of data from this input
410 * stream. The <code>skip</code> method may, for a variety of reasons, end
411 * up skipping over some smaller number of bytes, possibly <code>0</code>.
412 * This may result from any of a number of conditions; reaching end of file
413 * before <code>n</code> bytes have been skipped is only one possibility.
414 * The actual number of bytes skipped is returned. If {@code n} is
415 * negative, the {@code skip} method for class {@code InputStream} always
416 * returns 0, and no bytes are skipped. Subclasses may handle the negative
417 * value differently.
418 *
419 * <p> The <code>skip</code> method implementation of this class creates a
420 * byte array and then repeatedly reads into it until <code>n</code> bytes
421 * have been read or the end of the stream has been reached. Subclasses are
422 * encouraged to provide a more efficient implementation of this method.
423 * For instance, the implementation may depend on the ability to seek.
424 *
425 * @param n the number of bytes to be skipped.
426 * @return the actual number of bytes skipped.
427 * @throws IOException if an I/O error occurs.
428 */
429 public long skip(long n) throws IOException {
430
431 long remaining = n;
432 int nr;
433
434 if (n <= 0) {
435 return 0;
436 }
437
438 int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining);
439 byte[] skipBuffer = new byte[size];
440 while (remaining > 0) {
441 nr = read(skipBuffer, 0, (int)Math.min(size, remaining));
442 if (nr < 0) {
443 break;
444 }
445 remaining -= nr;
446 }
447
448 return n - remaining;
449 }
450
451 /**
452 * Returns an estimate of the number of bytes that can be read (or
453 * skipped over) from this input stream without blocking by the next
454 * invocation of a method for this input stream. The next invocation
455 * might be the same thread or another thread. A single read or skip of this
456 * many bytes will not block, but may read or skip fewer bytes.
457 *
458 * <p> Note that while some implementations of {@code InputStream} will return
459 * the total number of bytes in the stream, many will not. It is
460 * never correct to use the return value of this method to allocate
461 * a buffer intended to hold all data in this stream.
462 *
463 * <p> A subclass' implementation of this method may choose to throw an
464 * {@link IOException} if this input stream has been closed by
465 * invoking the {@link #close()} method.
466 *
467 * <p> The {@code available} method for class {@code InputStream} always
468 * returns {@code 0}.
469 *
470 * <p> This method should be overridden by subclasses.
471 *
472 * @return an estimate of the number of bytes that can be read (or skipped
473 * over) from this input stream without blocking or {@code 0} when
474 * it reaches the end of the input stream.
475 * @exception IOException if an I/O error occurs.
476 */
477 public int available() throws IOException {
478 return 0;
479 }
480
481 /**
482 * Closes this input stream and releases any system resources associated
483 * with the stream.
484 *
485 * <p> The <code>close</code> method of <code>InputStream</code> does
486 * nothing.
487 *
488 * @exception IOException if an I/O error occurs.
489 */
490 public void close() throws IOException {}
491
492 /**
493 * Marks the current position in this input stream. A subsequent call to
494 * the <code>reset</code> method repositions this stream at the last marked
495 * position so that subsequent reads re-read the same bytes.
496 *
497 * <p> The <code>readlimit</code> arguments tells this input stream to
498 * allow that many bytes to be read before the mark position gets
499 * invalidated.
500 *
501 * <p> The general contract of <code>mark</code> is that, if the method
502 * <code>markSupported</code> returns <code>true</code>, the stream somehow
503 * remembers all the bytes read after the call to <code>mark</code> and
504 * stands ready to supply those same bytes again if and whenever the method
505 * <code>reset</code> is called. However, the stream is not required to
506 * remember any data at all if more than <code>readlimit</code> bytes are
507 * read from the stream before <code>reset</code> is called.
508 *
509 * <p> Marking a closed stream should not have any effect on the stream.
510 *
511 * <p> The <code>mark</code> method of <code>InputStream</code> does
512 * nothing.
513 *
514 * @param readlimit the maximum limit of bytes that can be read before
515 * the mark position becomes invalid.
516 * @see java.io.InputStream#reset()
517 */
518 public synchronized void mark(int readlimit) {}
519
520 /**
521 * Repositions this stream to the position at the time the
522 * <code>mark</code> method was last called on this input stream.
523 *
524 * <p> The general contract of <code>reset</code> is:
525 *
526 * <ul>
527 * <li> If the method <code>markSupported</code> returns
528 * <code>true</code>, then:
529 *
530 * <ul><li> If the method <code>mark</code> has not been called since
531 * the stream was created, or the number of bytes read from the stream
532 * since <code>mark</code> was last called is larger than the argument
533 * to <code>mark</code> at that last call, then an
534 * <code>IOException</code> might be thrown.
535 *
536 * <li> If such an <code>IOException</code> is not thrown, then the
537 * stream is reset to a state such that all the bytes read since the
538 * most recent call to <code>mark</code> (or since the start of the
539 * file, if <code>mark</code> has not been called) will be resupplied
540 * to subsequent callers of the <code>read</code> method, followed by
541 * any bytes that otherwise would have been the next input data as of
542 * the time of the call to <code>reset</code>. </ul>
543 *
544 * <li> If the method <code>markSupported</code> returns
545 * <code>false</code>, then:
546 *
547 * <ul><li> The call to <code>reset</code> may throw an
548 * <code>IOException</code>.
549 *
550 * <li> If an <code>IOException</code> is not thrown, then the stream
551 * is reset to a fixed state that depends on the particular type of the
552 * input stream and how it was created. The bytes that will be supplied
553 * to subsequent callers of the <code>read</code> method depend on the
554 * particular type of the input stream. </ul></ul>
555 *
556 * <p>The method <code>reset</code> for class <code>InputStream</code>
557 * does nothing except throw an <code>IOException</code>.
558 *
559 * @exception IOException if this stream has not been marked or if the
560 * mark has been invalidated.
561 * @see java.io.InputStream#mark(int)
562 * @see java.io.IOException
563 */
564 public synchronized void reset() throws IOException {
565 throw new IOException("mark/reset not supported");
566 }
567
568 /**
569 * Tests if this input stream supports the <code>mark</code> and
570 * <code>reset</code> methods. Whether or not <code>mark</code> and
571 * <code>reset</code> are supported is an invariant property of a
572 * particular input stream instance. The <code>markSupported</code> method
573 * of <code>InputStream</code> returns <code>false</code>.
574 *
575 * @return <code>true</code> if this stream instance supports the mark
576 * and reset methods; <code>false</code> otherwise.
577 * @see java.io.InputStream#mark(int)
578 * @see java.io.InputStream#reset()
579 */
580 public boolean markSupported() {
581 return false;
582 }
583
584 /**
585 * Reads all bytes from this input stream and writes the bytes to the
586 * given output stream in the order that they are read. On return, this
587 * input stream will be at end of stream. This method does not close either
588 * stream.
589 * <p>
590 * This method may block indefinitely reading from the input stream, or
591 * writing to the output stream. The behavior for the case where the input
592 * and/or output stream is <i>asynchronously closed</i>, or the thread
593 * interrupted during the transfer, is highly input and output stream
594 * specific, and therefore not specified.
595 * <p>
596 * If an I/O error occurs reading from the input stream or writing to the
597 * output stream, then it may do so after some bytes have been read or
598 * written. Consequently the input stream may not be at end of stream and
599 * one, or both, streams may be in an inconsistent state. It is strongly
600 * recommended that both streams be promptly closed if an I/O error occurs.
601 *
602 * @param out the output stream, non-null
603 * @return the number of bytes transferred
604 * @throws IOException if an I/O error occurs when reading or writing
605 * @throws NullPointerException if {@code out} is {@code null}
606 *
607 * @since 9
608 */
609 public long transferTo(OutputStream out) throws IOException {
610 Objects.requireNonNull(out, "out");
611 long transferred = 0;
612 byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
613 int read;
614 while ((read = this.read(buffer, 0, DEFAULT_BUFFER_SIZE)) >= 0) {
615 out.write(buffer, 0, read);
616 transferred += read;
617 }
618 return transferred;
619 }
620 }