1 /*
2 * Copyright (c) 1994, 2018, 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 import jdk.internal.io.IOSupport;
33
34 /**
35 * This abstract class is the superclass of all classes representing
36 * an input stream of bytes.
37 *
38 * <p> Applications that need to define a subclass of <code>InputStream</code>
39 * must always provide a method that returns the next byte of input.
40 *
41 * @author Arthur van Hoff
42 * @see java.io.BufferedInputStream
43 * @see java.io.ByteArrayInputStream
44 * @see java.io.DataInputStream
45 * @see java.io.FilterInputStream
46 * @see java.io.InputStream#read()
47 * @see java.io.OutputStream
48 * @see java.io.PushbackInputStream
49 * @since 1.0
50 */
51 public abstract class InputStream implements Closeable {
52
53 // MAX_SKIP_BUFFER_SIZE is used to determine the maximum buffer size to
54 // use when skipping.
55 private static final int MAX_SKIP_BUFFER_SIZE = 2048;
56
57 private static final int DEFAULT_BUFFER_SIZE = 8192;
58
59 /**
60 * Reads the next byte of data from the input stream. The value byte is
61 * returned as an <code>int</code> in the range <code>0</code> to
62 * <code>255</code>. If no byte is available because the end of the stream
63 * has been reached, the value <code>-1</code> is returned. This method
64 * blocks until input data is available, the end of the stream is detected,
65 * or an exception is thrown.
66 *
67 * <p> A subclass must provide an implementation of this method.
68 *
69 * @return the next byte of data, or <code>-1</code> if the end of the
70 * stream is reached.
71 * @exception IOException if an I/O error occurs.
72 */
73 public abstract int read() throws IOException;
74
75 /**
76 * Reads some number of bytes from the input stream and stores them into
77 * the buffer array <code>b</code>. The number of bytes actually read is
78 * returned as an integer. This method blocks until input data is
79 * available, end of file is detected, or an exception is thrown.
80 *
81 * <p> If the length of <code>b</code> is zero, then no bytes are read and
82 * <code>0</code> is returned; otherwise, there is an attempt to read at
83 * least one byte. If no byte is available because the stream is at the
84 * end of the file, the value <code>-1</code> is returned; otherwise, at
85 * least one byte is read and stored into <code>b</code>.
86 *
87 * <p> The first byte read is stored into element <code>b[0]</code>, the
88 * next one into <code>b[1]</code>, and so on. The number of bytes read is,
89 * at most, equal to the length of <code>b</code>. Let <i>k</i> be the
90 * number of bytes actually read; these bytes will be stored in elements
91 * <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>,
92 * leaving elements <code>b[</code><i>k</i><code>]</code> through
93 * <code>b[b.length-1]</code> unaffected.
94 *
95 * <p> The <code>read(b)</code> method for class <code>InputStream</code>
96 * has the same effect as: <pre><code> read(b, 0, b.length) </code></pre>
97 *
98 * @param b the buffer into which the data is read.
99 * @return the total number of bytes read into the buffer, or
100 * <code>-1</code> if there is no more data because the end of
101 * the stream has been reached.
102 * @exception IOException If the first byte cannot be read for any reason
103 * other than the end of the file, if the input stream has been closed, or
104 * if some other I/O error occurs.
105 * @exception NullPointerException if <code>b</code> is <code>null</code>.
106 * @see java.io.InputStream#read(byte[], int, int)
107 */
108 public int read(byte b[]) throws IOException {
109 return read(b, 0, b.length);
110 }
111
112 /**
113 * Reads up to <code>len</code> bytes of data from the input stream into
114 * an array of bytes. An attempt is made to read as many as
115 * <code>len</code> bytes, but a smaller number may be read.
116 * The number of bytes actually read is returned as an integer.
117 *
118 * <p> This method blocks until input data is available, end of file is
119 * detected, or an exception is thrown.
120 *
121 * <p> If <code>len</code> is zero, then no bytes are read and
122 * <code>0</code> is returned; otherwise, there is an attempt to read at
123 * least one byte. If no byte is available because the stream is at end of
124 * file, the value <code>-1</code> is returned; otherwise, at least one
125 * byte is read and stored into <code>b</code>.
126 *
127 * <p> The first byte read is stored into element <code>b[off]</code>, the
128 * next one into <code>b[off+1]</code>, and so on. The number of bytes read
129 * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
130 * bytes actually read; these bytes will be stored in elements
131 * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
132 * leaving elements <code>b[off+</code><i>k</i><code>]</code> through
133 * <code>b[off+len-1]</code> unaffected.
134 *
135 * <p> In every case, elements <code>b[0]</code> through
136 * <code>b[off]</code> and elements <code>b[off+len]</code> through
137 * <code>b[b.length-1]</code> are unaffected.
138 *
139 * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method
140 * for class <code>InputStream</code> simply calls the method
141 * <code>read()</code> repeatedly. If the first such call results in an
142 * <code>IOException</code>, that exception is returned from the call to
143 * the <code>read(b,</code> <code>off,</code> <code>len)</code> method. If
144 * any subsequent call to <code>read()</code> results in a
145 * <code>IOException</code>, the exception is caught and treated as if it
146 * were end of file; the bytes read up to that point are stored into
147 * <code>b</code> and the number of bytes read before the exception
148 * occurred is returned. The default implementation of this method blocks
149 * until the requested amount of input data <code>len</code> has been read,
150 * end of file is detected, or an exception is thrown. Subclasses are encouraged
151 * to provide a more efficient implementation of this method.
152 *
153 * @param b the buffer into which the data is read.
154 * @param off the start offset in array <code>b</code>
155 * at which the data is written.
156 * @param len the maximum number of bytes to read.
157 * @return the total number of bytes read into the buffer, or
158 * <code>-1</code> if there is no more data because the end of
159 * the stream has been reached.
160 * @exception IOException If the first byte cannot be read for any reason
161 * other than end of file, or if the input stream has been closed, or if
162 * some other I/O error occurs.
163 * @exception NullPointerException If <code>b</code> is <code>null</code>.
164 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
165 * <code>len</code> is negative, or <code>len</code> is greater than
166 * <code>b.length - off</code>
167 * @see java.io.InputStream#read()
168 */
169 public int read(byte b[], int off, int len) throws IOException {
170 Objects.requireNonNull(b);
171 Objects.checkFromIndexSize(off, len, b.length);
172 if (len == 0) {
173 return 0;
174 }
175
176 int c = read();
177 if (c == -1) {
178 return -1;
179 }
180 b[off] = (byte)c;
181
182 int i = 1;
183 try {
184 for (; i < len ; i++) {
185 c = read();
186 if (c == -1) {
187 break;
188 }
189 b[off + i] = (byte)c;
190 }
191 } catch (IOException ee) {
192 }
193 return i;
194 }
195
196 /**
197 * The maximum size of array to allocate.
198 * Some VMs reserve some header words in an array.
199 * Attempts to allocate larger arrays may result in
200 * OutOfMemoryError: Requested array size exceeds VM limit
201 */
202 private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
203
204 /**
205 * Reads all remaining bytes from the input stream. This method blocks until
206 * all remaining bytes have been read and end of stream is detected, or an
207 * exception is thrown. This method does not close the input stream.
208 *
209 * <p> When this stream reaches end of stream, further invocations of this
210 * method will return an empty byte array.
211 *
212 * <p> Note that this method is intended for simple cases where it is
213 * convenient to read all bytes into a byte array. It is not intended for
214 * reading input streams with large amounts of data.
215 *
216 * <p> The behavior for the case where the input stream is <i>asynchronously
217 * closed</i>, or the thread interrupted during the read, is highly input
218 * stream specific, and therefore not specified.
219 *
220 * <p> If an I/O error occurs reading from the input stream, then it may do
221 * so after some, but not all, bytes have been read. Consequently the input
222 * stream may not be at end of stream and may be in an inconsistent state.
223 * It is strongly recommended that the stream be promptly closed if an I/O
224 * error occurs.
225 *
226 * @return a byte array containing the bytes read from this input stream
227 * @throws IOException if an I/O error occurs
228 * @throws OutOfMemoryError if an array of the required size cannot be
229 * allocated. For example, if an array larger than {@code 2GB} would
230 * be required to store the bytes.
231 *
232 * @since 9
233 */
234 public byte[] readAllBytes() throws IOException {
235 List<byte[]> bufs = null;
236 byte[] result = null;
237 int total = 0;
238 int n;
239 do {
240 byte[] buf = new byte[DEFAULT_BUFFER_SIZE];
241 int nread = 0;
242
243 // read to EOF which may read more or less than buffer size
244 while ((n = read(buf, nread, buf.length - nread)) > 0) {
245 nread += n;
246 }
247
248 if (nread > 0) {
249 if (MAX_BUFFER_SIZE - total < nread) {
250 throw new OutOfMemoryError("Required array size too large");
251 }
252 total += nread;
253 if (result == null) {
254 result = buf;
255 } else {
256 if (bufs == null) {
257 bufs = new ArrayList<>();
258 bufs.add(result);
259 }
260 bufs.add(buf);
261 }
262 }
263 } while (n >= 0); // if the last call to read returned -1, then break
264
265 if (bufs == null) {
266 if (result == null) {
267 return new byte[0];
268 }
269 return result.length == total ?
270 result : Arrays.copyOf(result, total);
271 }
272
273 result = new byte[total];
274 int offset = 0;
275 int remaining = total;
276 for (byte[] b : bufs) {
277 int len = Math.min(b.length, remaining);
278 System.arraycopy(b, 0, result, offset, len);
279 offset += len;
280 remaining -= len;
281 }
282
283 return result;
284 }
285
286 /**
287 * Reads the requested number of bytes from the input stream into the given
288 * byte array. This method blocks until {@code len} bytes of input data have
289 * been read, end of stream is detected, or an exception is thrown. The
290 * number of bytes actually read, possibly zero, is returned. This method
291 * does not close the input stream.
292 *
293 * <p> In the case where end of stream is reached before {@code len} bytes
294 * have been read, then the actual number of bytes read will be returned.
295 * When this stream reaches end of stream, further invocations of this
296 * method will return zero.
297 *
298 * <p> If {@code len} is zero, then no bytes are read and {@code 0} is
299 * returned; otherwise, there is an attempt to read up to {@code len} bytes.
300 *
301 * <p> The first byte read is stored into element {@code b[off]}, the next
302 * one in to {@code b[off+1]}, and so on. The number of bytes read is, at
303 * most, equal to {@code len}. Let <i>k</i> be the number of bytes actually
304 * read; these bytes will be stored in elements {@code b[off]} through
305 * {@code b[off+}<i>k</i>{@code -1]}, leaving elements {@code b[off+}<i>k</i>
306 * {@code ]} through {@code b[off+len-1]} unaffected.
307 *
308 * <p> The behavior for the case where the input stream is <i>asynchronously
309 * closed</i>, or the thread interrupted during the read, is highly input
310 * stream specific, and therefore not specified.
311 *
312 * <p> If an I/O error occurs reading from the input stream, then it may do
313 * so after some, but not all, bytes of {@code b} have been updated with
314 * data from the input stream. Consequently the input stream and {@code b}
315 * may be in an inconsistent state. It is strongly recommended that the
316 * stream be promptly closed if an I/O error occurs.
317 *
318 * @param b the byte array into which the data is read
319 * @param off the start offset in {@code b} at which the data is written
320 * @param len the maximum number of bytes to read
321 * @return the actual number of bytes read into the buffer
322 * @throws IOException if an I/O error occurs
323 * @throws NullPointerException if {@code b} is {@code null}
324 * @throws IndexOutOfBoundsException If {@code off} is negative, {@code len}
325 * is negative, or {@code len} is greater than {@code b.length - off}
326 *
327 * @since 9
328 */
329 public int readNBytes(byte[] b, int off, int len) throws IOException {
330 Objects.requireNonNull(b);
331 Objects.checkFromIndexSize(off, len, b.length);
332
333 int n = 0;
334 while (n < len) {
335 int count = read(b, off + n, len - n);
336 if (count < 0)
337 break;
338 n += count;
339 }
340 return n;
341 }
342
343 /**
344 * Skips over and discards <code>n</code> bytes of data from this input
345 * stream. The <code>skip</code> method may, for a variety of reasons, end
346 * up skipping over some smaller number of bytes, possibly <code>0</code>.
347 * This may result from any of a number of conditions; reaching end of file
348 * before <code>n</code> bytes have been skipped is only one possibility.
349 * The actual number of bytes skipped is returned. If {@code n} is
350 * negative, the {@code skip} method for class {@code InputStream} always
351 * returns 0, and no bytes are skipped. Subclasses may handle the negative
352 * value differently.
353 *
354 * <p> The <code>skip</code> method implementation of this class creates a
355 * byte array and then repeatedly reads into it until <code>n</code> bytes
356 * have been read or the end of the stream has been reached. Subclasses are
357 * encouraged to provide a more efficient implementation of this method.
358 * For instance, the implementation may depend on the ability to seek.
359 *
360 * @param n the number of bytes to be skipped.
361 * @return the actual number of bytes skipped.
362 * @throws IOException if an I/O error occurs.
363 */
364 public long skip(long n) throws IOException {
365
366 long remaining = n;
367 int nr;
368
369 if (n <= 0) {
370 return 0;
371 }
372
373 int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining);
374 byte[] skipBuffer = new byte[size];
375 while (remaining > 0) {
376 nr = read(skipBuffer, 0, (int)Math.min(size, remaining));
377 if (nr < 0) {
378 break;
379 }
380 remaining -= nr;
381 }
382
383 return n - remaining;
384 }
385
386 /**
387 * Returns an estimate of the number of bytes that can be read (or
388 * skipped over) from this input stream without blocking by the next
389 * invocation of a method for this input stream. The next invocation
390 * might be the same thread or another thread. A single read or skip of this
391 * many bytes will not block, but may read or skip fewer bytes.
392 *
393 * <p> Note that while some implementations of {@code InputStream} will return
394 * the total number of bytes in the stream, many will not. It is
395 * never correct to use the return value of this method to allocate
396 * a buffer intended to hold all data in this stream.
397 *
398 * <p> A subclass' implementation of this method may choose to throw an
399 * {@link IOException} if this input stream has been closed by
400 * invoking the {@link #close()} method.
401 *
402 * <p> The {@code available} method for class {@code InputStream} always
403 * returns {@code 0}.
404 *
405 * <p> This method should be overridden by subclasses.
406 *
407 * @return an estimate of the number of bytes that can be read (or skipped
408 * over) from this input stream without blocking or {@code 0} when
409 * it reaches the end of the input stream.
410 * @exception IOException if an I/O error occurs.
411 */
412 public int available() throws IOException {
413 return 0;
414 }
415
416 /**
417 * Closes this input stream and releases any system resources associated
418 * with the stream.
419 *
420 * <p> The <code>close</code> method of <code>InputStream</code> does
421 * nothing.
422 *
423 * @exception IOException if an I/O error occurs.
424 */
425 public void close() throws IOException {}
426
427 /**
428 * Marks the current position in this input stream. A subsequent call to
429 * the <code>reset</code> method repositions this stream at the last marked
430 * position so that subsequent reads re-read the same bytes.
431 *
432 * <p> The <code>readlimit</code> arguments tells this input stream to
433 * allow that many bytes to be read before the mark position gets
434 * invalidated.
435 *
436 * <p> The general contract of <code>mark</code> is that, if the method
437 * <code>markSupported</code> returns <code>true</code>, the stream somehow
438 * remembers all the bytes read after the call to <code>mark</code> and
439 * stands ready to supply those same bytes again if and whenever the method
440 * <code>reset</code> is called. However, the stream is not required to
441 * remember any data at all if more than <code>readlimit</code> bytes are
442 * read from the stream before <code>reset</code> is called.
443 *
444 * <p> Marking a closed stream should not have any effect on the stream.
445 *
446 * <p> The <code>mark</code> method of <code>InputStream</code> does
447 * nothing.
448 *
449 * @param readlimit the maximum limit of bytes that can be read before
450 * the mark position becomes invalid.
451 * @see java.io.InputStream#reset()
452 */
453 public synchronized void mark(int readlimit) {}
454
455 /**
456 * Repositions this stream to the position at the time the
457 * <code>mark</code> method was last called on this input stream.
458 *
459 * <p> The general contract of <code>reset</code> is:
460 *
461 * <ul>
462 * <li> If the method <code>markSupported</code> returns
463 * <code>true</code>, then:
464 *
465 * <ul><li> If the method <code>mark</code> has not been called since
466 * the stream was created, or the number of bytes read from the stream
467 * since <code>mark</code> was last called is larger than the argument
468 * to <code>mark</code> at that last call, then an
469 * <code>IOException</code> might be thrown.
470 *
471 * <li> If such an <code>IOException</code> is not thrown, then the
472 * stream is reset to a state such that all the bytes read since the
473 * most recent call to <code>mark</code> (or since the start of the
474 * file, if <code>mark</code> has not been called) will be resupplied
475 * to subsequent callers of the <code>read</code> method, followed by
476 * any bytes that otherwise would have been the next input data as of
477 * the time of the call to <code>reset</code>. </ul>
478 *
479 * <li> If the method <code>markSupported</code> returns
480 * <code>false</code>, then:
481 *
482 * <ul><li> The call to <code>reset</code> may throw an
483 * <code>IOException</code>.
484 *
485 * <li> If an <code>IOException</code> is not thrown, then the stream
486 * is reset to a fixed state that depends on the particular type of the
487 * input stream and how it was created. The bytes that will be supplied
488 * to subsequent callers of the <code>read</code> method depend on the
489 * particular type of the input stream. </ul></ul>
490 *
491 * <p>The method <code>reset</code> for class <code>InputStream</code>
492 * does nothing except throw an <code>IOException</code>.
493 *
494 * @exception IOException if this stream has not been marked or if the
495 * mark has been invalidated.
496 * @see java.io.InputStream#mark(int)
497 * @see java.io.IOException
498 */
499 public synchronized void reset() throws IOException {
500 throw new IOException("mark/reset not supported");
501 }
502
503 /**
504 * Tests if this input stream supports the <code>mark</code> and
505 * <code>reset</code> methods. Whether or not <code>mark</code> and
506 * <code>reset</code> are supported is an invariant property of a
507 * particular input stream instance. The <code>markSupported</code> method
508 * of <code>InputStream</code> returns <code>false</code>.
509 *
510 * @return <code>true</code> if this stream instance supports the mark
511 * and reset methods; <code>false</code> otherwise.
512 * @see java.io.InputStream#mark(int)
513 * @see java.io.InputStream#reset()
514 */
515 public boolean markSupported() {
516 return false;
517 }
518
519 /**
520 * Reads all bytes from this input stream and writes the bytes to the
521 * given output stream in the order that they are read. On return, this
522 * input stream will be at end of stream. This method does not close either
523 * stream.
524 * <p>
525 * This method may block indefinitely reading from the input stream, or
526 * writing to the output stream. The behavior for the case where the input
527 * and/or output stream is <i>asynchronously closed</i>, or the thread
528 * interrupted during the transfer, is highly input and output stream
529 * specific, and therefore not specified.
530 * <p>
531 * If an I/O error occurs reading from the input stream or writing to the
532 * output stream, then it may do so after some bytes have been read or
533 * written. Consequently the input stream may not be at end of stream and
534 * one, or both, streams may be in an inconsistent state. It is strongly
535 * recommended that both streams be promptly closed if an I/O error occurs.
536 *
537 * @param out the output stream, non-null
538 * @return the number of bytes transferred
539 * @throws IOException if an I/O error occurs when reading or writing
540 * @throws NullPointerException if {@code out} is {@code null}
541 *
542 * @since 9
543 */
544 public long transferTo(OutputStream out) throws IOException {
545 Objects.requireNonNull(out, "out");
546 return IOSupport.copy(this, out);
547 }
548 }