1 /*
2 * Copyright (c) 1994, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.io;
27
28 import java.util.ArrayList;
29 import java.util.Arrays;
30 import java.util.List;
31 import java.util.Objects;
32
33 /**
34 * This abstract class is the superclass of all classes representing
35 * an input stream of bytes.
36 *
37 * <p> Applications that need to define a subclass of <code>InputStream</code>
38 * must always provide a method that returns the next byte of input.
39 *
40 * @author Arthur van Hoff
41 * @see java.io.BufferedInputStream
42 * @see java.io.ByteArrayInputStream
43 * @see java.io.DataInputStream
44 * @see java.io.FilterInputStream
45 * @see java.io.InputStream#read()
46 * @see java.io.OutputStream
47 * @see java.io.PushbackInputStream
48 * @since 1.0
49 */
50 public abstract class InputStream implements Closeable {
51
52 // MAX_SKIP_BUFFER_SIZE is used to determine the maximum buffer size to
53 // use when skipping.
54 private static final int MAX_SKIP_BUFFER_SIZE = 2048;
55
56 private static final int DEFAULT_BUFFER_SIZE = 8192;
57
58 /**
59 * Reads the next byte of data from the input stream. The value byte is
60 * returned as an <code>int</code> in the range <code>0</code> to
61 * <code>255</code>. If no byte is available because the end of the stream
62 * has been reached, the value <code>-1</code> is returned. This method
63 * blocks until input data is available, the end of the stream is detected,
64 * or an exception is thrown.
65 *
66 * <p> A subclass must provide an implementation of this method.
67 *
68 * @return the next byte of data, or <code>-1</code> if the end of the
69 * stream is reached.
70 * @exception IOException if an I/O error occurs.
71 */
72 public abstract int read() throws IOException;
73
74 /**
75 * Reads some number of bytes from the input stream and stores them into
76 * the buffer array <code>b</code>. The number of bytes actually read is
77 * returned as an integer. This method blocks until input data is
78 * available, end of file is detected, or an exception is thrown.
79 *
80 * <p> If the length of <code>b</code> is zero, then no bytes are read and
81 * <code>0</code> is returned; otherwise, there is an attempt to read at
82 * least one byte. If no byte is available because the stream is at the
83 * end of the file, the value <code>-1</code> is returned; otherwise, at
84 * least one byte is read and stored into <code>b</code>.
85 *
86 * <p> The first byte read is stored into element <code>b[0]</code>, the
87 * next one into <code>b[1]</code>, and so on. The number of bytes read is,
88 * at most, equal to the length of <code>b</code>. Let <i>k</i> be the
89 * number of bytes actually read; these bytes will be stored in elements
90 * <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>,
91 * leaving elements <code>b[</code><i>k</i><code>]</code> through
92 * <code>b[b.length-1]</code> unaffected.
93 *
94 * <p> The <code>read(b)</code> method for class <code>InputStream</code>
95 * has the same effect as: <pre><code> read(b, 0, b.length) </code></pre>
96 *
97 * @param b the buffer into which the data is read.
98 * @return the total number of bytes read into the buffer, or
99 * <code>-1</code> if there is no more data because the end of
100 * the stream has been reached.
101 * @exception IOException If the first byte cannot be read for any reason
102 * other than the end of the file, if the input stream has been closed, or
103 * if some other I/O error occurs.
104 * @exception NullPointerException if <code>b</code> is <code>null</code>.
105 * @see java.io.InputStream#read(byte[], int, int)
106 */
107 public int read(byte b[]) throws IOException {
108 return read(b, 0, b.length);
109 }
110
111 /**
112 * Reads up to <code>len</code> bytes of data from the input stream into
113 * an array of bytes. An attempt is made to read as many as
114 * <code>len</code> bytes, but a smaller number may be read.
115 * The number of bytes actually read is returned as an integer.
116 *
117 * <p> This method blocks until input data is available, end of file is
118 * detected, or an exception is thrown.
119 *
120 * <p> If <code>len</code> is zero, then no bytes are read and
121 * <code>0</code> is returned; otherwise, there is an attempt to read at
122 * least one byte. If no byte is available because the stream is at end of
123 * file, the value <code>-1</code> is returned; otherwise, at least one
124 * byte is read and stored into <code>b</code>.
125 *
126 * <p> The first byte read is stored into element <code>b[off]</code>, the
127 * next one into <code>b[off+1]</code>, and so on. The number of bytes read
128 * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
129 * bytes actually read; these bytes will be stored in elements
130 * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
131 * leaving elements <code>b[off+</code><i>k</i><code>]</code> through
132 * <code>b[off+len-1]</code> unaffected.
133 *
134 * <p> In every case, elements <code>b[0]</code> through
135 * <code>b[off]</code> and elements <code>b[off+len]</code> through
136 * <code>b[b.length-1]</code> are unaffected.
137 *
138 * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method
139 * for class <code>InputStream</code> simply calls the method
140 * <code>read()</code> repeatedly. If the first such call results in an
141 * <code>IOException</code>, that exception is returned from the call to
142 * the <code>read(b,</code> <code>off,</code> <code>len)</code> method. If
143 * any subsequent call to <code>read()</code> results in a
144 * <code>IOException</code>, the exception is caught and treated as if it
145 * were end of file; the bytes read up to that point are stored into
146 * <code>b</code> and the number of bytes read before the exception
147 * occurred is returned. The default implementation of this method blocks
148 * until the requested amount of input data <code>len</code> has been read,
149 * end of file is detected, or an exception is thrown. Subclasses are encouraged
150 * to provide a more efficient implementation of this method.
151 *
152 * @param b the buffer into which the data is read.
153 * @param off the start offset in array <code>b</code>
154 * at which the data is written.
155 * @param len the maximum number of bytes to read.
156 * @return the total number of bytes read into the buffer, or
157 * <code>-1</code> if there is no more data because the end of
158 * the stream has been reached.
159 * @exception IOException If the first byte cannot be read for any reason
160 * other than end of file, or if the input stream has been closed, or if
161 * some other I/O error occurs.
162 * @exception NullPointerException If <code>b</code> is <code>null</code>.
163 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
164 * <code>len</code> is negative, or <code>len</code> is greater than
165 * <code>b.length - off</code>
166 * @see java.io.InputStream#read()
167 */
168 public int read(byte b[], int off, int len) throws IOException {
169 Objects.requireNonNull(b);
170 Objects.checkFromIndexSize(off, len, b.length);
171 if (len == 0) {
172 return 0;
173 }
174
175 int c = read();
176 if (c == -1) {
177 return -1;
178 }
179 b[off] = (byte)c;
180
181 int i = 1;
182 try {
183 for (; i < len ; i++) {
184 c = read();
185 if (c == -1) {
186 break;
187 }
188 b[off + i] = (byte)c;
189 }
190 } catch (IOException ee) {
191 }
192 return i;
193 }
194
195 /**
196 * The maximum size of array to allocate.
197 * Some VMs reserve some header words in an array.
198 * Attempts to allocate larger arrays may result in
199 * OutOfMemoryError: Requested array size exceeds VM limit
200 */
201 private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
202
203 /**
204 * Reads all remaining bytes from the input stream. This method blocks until
205 * all remaining bytes have been read and end of stream is detected, or an
206 * exception is thrown. This method does not close the input stream.
207 *
208 * <p> When this stream reaches end of stream, further invocations of this
209 * method will return an empty byte array.
210 *
211 * <p> Note that this method is intended for simple cases where it is
212 * convenient to read all bytes into a byte array. It is not intended for
213 * reading input streams with large amounts of data.
214 *
215 * <p> The behavior for the case where the input stream is <i>asynchronously
216 * closed</i>, or the thread interrupted during the read, is highly input
217 * stream specific, and therefore not specified.
218 *
219 * <p> If an I/O error occurs reading from the input stream, then it may do
220 * so after some, but not all, bytes have been read. Consequently the input
221 * stream may not be at end of stream and may be in an inconsistent state.
222 * It is strongly recommended that the stream be promptly closed if an I/O
223 * error occurs.
224 *
225 * @return a byte array containing the bytes read from this input stream
226 * @throws IOException if an I/O error occurs
227 * @throws OutOfMemoryError if an array of the required size cannot be
228 * allocated. For example, if an array larger than {@code 2GB} would
229 * be required to store the bytes.
230 *
231 * @since 9
232 */
233 public byte[] readAllBytes() throws IOException {
234 List<byte[]> bufs = null;
235 byte[] result = null;
236 byte[] buf = new byte[DEFAULT_BUFFER_SIZE];
237 int total = 0;
238 int n;
239 do {
240 int nread = 0;
241
242 // read to EOF which may read more or less than buffer size
243 while ((n = read(buf, nread, buf.length - nread)) > 0) {
244 nread += n;
245 }
246
247 if (nread > 0) {
248 if (MAX_BUFFER_SIZE - total < nread) {
249 throw new OutOfMemoryError("Required array size too large");
250 }
251 total += nread;
252 byte[] copy;
253 if (nread == DEFAULT_BUFFER_SIZE) {
254 copy = buf;
255 if (n >= 0) {
256 buf = new byte[DEFAULT_BUFFER_SIZE];
257 }
258 } else {
259 copy = Arrays.copyOf(buf, nread);
260 }
261 if (result == null) {
262 result = copy;
263 } else {
264 if (bufs == null) {
265 bufs = new ArrayList<>();
266 bufs.add(result);
267 }
268 bufs.add(copy);
269 }
270 }
271 } while (n >= 0); // if the last call to read returned -1, then break
272
273 if (bufs == null) {
274 return result == null ? new byte[0] : result;
275 }
276
277 result = new byte[total];
278 int offset = 0;
279 for (byte[] b : bufs) {
280 System.arraycopy(b, 0, result, offset, b.length);
281 offset += b.length;
282 }
283
284 return result;
285 }
286
287 /**
288 * Reads the requested number of bytes from the input stream into the given
289 * byte array. This method blocks until {@code len} bytes of input data have
290 * been read, end of stream is detected, or an exception is thrown. The
291 * number of bytes actually read, possibly zero, is returned. This method
292 * does not close the input stream.
293 *
294 * <p> In the case where end of stream is reached before {@code len} bytes
295 * have been read, then the actual number of bytes read will be returned.
296 * When this stream reaches end of stream, further invocations of this
297 * method will return zero.
298 *
299 * <p> If {@code len} is zero, then no bytes are read and {@code 0} is
300 * returned; otherwise, there is an attempt to read up to {@code len} bytes.
301 *
302 * <p> The first byte read is stored into element {@code b[off]}, the next
303 * one in to {@code b[off+1]}, and so on. The number of bytes read is, at
304 * most, equal to {@code len}. Let <i>k</i> be the number of bytes actually
305 * read; these bytes will be stored in elements {@code b[off]} through
306 * {@code b[off+}<i>k</i>{@code -1]}, leaving elements {@code b[off+}<i>k</i>
307 * {@code ]} through {@code b[off+len-1]} unaffected.
308 *
309 * <p> The behavior for the case where the input stream is <i>asynchronously
310 * closed</i>, or the thread interrupted during the read, is highly input
311 * stream specific, and therefore not specified.
312 *
313 * <p> If an I/O error occurs reading from the input stream, then it may do
314 * so after some, but not all, bytes of {@code b} have been updated with
315 * data from the input stream. Consequently the input stream and {@code b}
316 * may be in an inconsistent state. It is strongly recommended that the
317 * stream be promptly closed if an I/O error occurs.
318 *
319 * @param b the byte array into which the data is read
320 * @param off the start offset in {@code b} at which the data is written
321 * @param len the maximum number of bytes to read
322 * @return the actual number of bytes read into the buffer
323 * @throws IOException if an I/O error occurs
324 * @throws NullPointerException if {@code b} is {@code null}
325 * @throws IndexOutOfBoundsException If {@code off} is negative, {@code len}
326 * is negative, or {@code len} is greater than {@code b.length - off}
327 *
328 * @since 9
329 */
330 public int readNBytes(byte[] b, int off, int len) throws IOException {
331 Objects.requireNonNull(b);
332 Objects.checkFromIndexSize(off, len, b.length);
333
334 int n = 0;
335 while (n < len) {
336 int count = read(b, off + n, len - n);
337 if (count < 0)
338 break;
339 n += count;
340 }
341 return n;
342 }
343
344 /**
345 * Skips over and discards <code>n</code> bytes of data from this input
346 * stream. The <code>skip</code> method may, for a variety of reasons, end
347 * up skipping over some smaller number of bytes, possibly <code>0</code>.
348 * This may result from any of a number of conditions; reaching end of file
349 * before <code>n</code> bytes have been skipped is only one possibility.
350 * The actual number of bytes skipped is returned. If {@code n} is
351 * negative, the {@code skip} method for class {@code InputStream} always
352 * returns 0, and no bytes are skipped. Subclasses may handle the negative
353 * value differently.
354 *
355 * <p> The <code>skip</code> method implementation of this class creates a
356 * byte array and then repeatedly reads into it until <code>n</code> bytes
357 * have been read or the end of the stream has been reached. Subclasses are
358 * encouraged to provide a more efficient implementation of this method.
359 * For instance, the implementation may depend on the ability to seek.
360 *
361 * @param n the number of bytes to be skipped.
362 * @return the actual number of bytes skipped.
363 * @throws IOException if an I/O error occurs.
364 */
365 public long skip(long n) throws IOException {
366
367 long remaining = n;
368 int nr;
369
370 if (n <= 0) {
371 return 0;
372 }
373
374 int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining);
375 byte[] skipBuffer = new byte[size];
376 while (remaining > 0) {
377 nr = read(skipBuffer, 0, (int)Math.min(size, remaining));
378 if (nr < 0) {
379 break;
380 }
381 remaining -= nr;
382 }
383
384 return n - remaining;
385 }
386
387 /**
388 * Returns an estimate of the number of bytes that can be read (or
389 * skipped over) from this input stream without blocking by the next
390 * invocation of a method for this input stream. The next invocation
391 * might be the same thread or another thread. A single read or skip of this
392 * many bytes will not block, but may read or skip fewer bytes.
393 *
394 * <p> Note that while some implementations of {@code InputStream} will return
395 * the total number of bytes in the stream, many will not. It is
396 * never correct to use the return value of this method to allocate
397 * a buffer intended to hold all data in this stream.
398 *
399 * <p> A subclass' implementation of this method may choose to throw an
400 * {@link IOException} if this input stream has been closed by
401 * invoking the {@link #close()} method.
402 *
403 * <p> The {@code available} method for class {@code InputStream} always
404 * returns {@code 0}.
405 *
406 * <p> This method should be overridden by subclasses.
407 *
408 * @return an estimate of the number of bytes that can be read (or skipped
409 * over) from this input stream without blocking or {@code 0} when
410 * it reaches the end of the input stream.
411 * @exception IOException if an I/O error occurs.
412 */
413 public int available() throws IOException {
414 return 0;
415 }
416
417 /**
418 * Closes this input stream and releases any system resources associated
419 * with the stream.
420 *
421 * <p> The <code>close</code> method of <code>InputStream</code> does
422 * nothing.
423 *
424 * @exception IOException if an I/O error occurs.
425 */
426 public void close() throws IOException {}
427
428 /**
429 * Marks the current position in this input stream. A subsequent call to
430 * the <code>reset</code> method repositions this stream at the last marked
431 * position so that subsequent reads re-read the same bytes.
432 *
433 * <p> The <code>readlimit</code> arguments tells this input stream to
434 * allow that many bytes to be read before the mark position gets
435 * invalidated.
436 *
437 * <p> The general contract of <code>mark</code> is that, if the method
438 * <code>markSupported</code> returns <code>true</code>, the stream somehow
439 * remembers all the bytes read after the call to <code>mark</code> and
440 * stands ready to supply those same bytes again if and whenever the method
441 * <code>reset</code> is called. However, the stream is not required to
442 * remember any data at all if more than <code>readlimit</code> bytes are
443 * read from the stream before <code>reset</code> is called.
444 *
445 * <p> Marking a closed stream should not have any effect on the stream.
446 *
447 * <p> The <code>mark</code> method of <code>InputStream</code> does
448 * nothing.
449 *
450 * @param readlimit the maximum limit of bytes that can be read before
451 * the mark position becomes invalid.
452 * @see java.io.InputStream#reset()
453 */
454 public synchronized void mark(int readlimit) {}
455
456 /**
457 * Repositions this stream to the position at the time the
458 * <code>mark</code> method was last called on this input stream.
459 *
460 * <p> The general contract of <code>reset</code> is:
461 *
462 * <ul>
463 * <li> If the method <code>markSupported</code> returns
464 * <code>true</code>, then:
465 *
466 * <ul><li> If the method <code>mark</code> has not been called since
467 * the stream was created, or the number of bytes read from the stream
468 * since <code>mark</code> was last called is larger than the argument
469 * to <code>mark</code> at that last call, then an
470 * <code>IOException</code> might be thrown.
471 *
472 * <li> If such an <code>IOException</code> is not thrown, then the
473 * stream is reset to a state such that all the bytes read since the
474 * most recent call to <code>mark</code> (or since the start of the
475 * file, if <code>mark</code> has not been called) will be resupplied
476 * to subsequent callers of the <code>read</code> method, followed by
477 * any bytes that otherwise would have been the next input data as of
478 * the time of the call to <code>reset</code>. </ul>
479 *
480 * <li> If the method <code>markSupported</code> returns
481 * <code>false</code>, then:
482 *
483 * <ul><li> The call to <code>reset</code> may throw an
484 * <code>IOException</code>.
485 *
486 * <li> If an <code>IOException</code> is not thrown, then the stream
487 * is reset to a fixed state that depends on the particular type of the
488 * input stream and how it was created. The bytes that will be supplied
489 * to subsequent callers of the <code>read</code> method depend on the
490 * particular type of the input stream. </ul></ul>
491 *
492 * <p>The method <code>reset</code> for class <code>InputStream</code>
493 * does nothing except throw an <code>IOException</code>.
494 *
495 * @exception IOException if this stream has not been marked or if the
496 * mark has been invalidated.
497 * @see java.io.InputStream#mark(int)
498 * @see java.io.IOException
499 */
500 public synchronized void reset() throws IOException {
501 throw new IOException("mark/reset not supported");
502 }
503
504 /**
505 * Tests if this input stream supports the <code>mark</code> and
506 * <code>reset</code> methods. Whether or not <code>mark</code> and
507 * <code>reset</code> are supported is an invariant property of a
508 * particular input stream instance. The <code>markSupported</code> method
509 * of <code>InputStream</code> returns <code>false</code>.
510 *
511 * @return <code>true</code> if this stream instance supports the mark
512 * and reset methods; <code>false</code> otherwise.
513 * @see java.io.InputStream#mark(int)
514 * @see java.io.InputStream#reset()
515 */
516 public boolean markSupported() {
517 return false;
518 }
519
520 /**
521 * Reads all bytes from this input stream and writes the bytes to the
522 * given output stream in the order that they are read. On return, this
523 * input stream will be at end of stream. This method does not close either
524 * stream.
525 * <p>
526 * This method may block indefinitely reading from the input stream, or
527 * writing to the output stream. The behavior for the case where the input
528 * and/or output stream is <i>asynchronously closed</i>, or the thread
529 * interrupted during the transfer, is highly input and output stream
530 * specific, and therefore not specified.
531 * <p>
532 * If an I/O error occurs reading from the input stream or writing to the
533 * output stream, then it may do so after some bytes have been read or
534 * written. Consequently the input stream may not be at end of stream and
535 * one, or both, streams may be in an inconsistent state. It is strongly
536 * recommended that both streams be promptly closed if an I/O error occurs.
537 *
538 * @param out the output stream, non-null
539 * @return the number of bytes transferred
540 * @throws IOException if an I/O error occurs when reading or writing
541 * @throws NullPointerException if {@code out} is {@code null}
542 *
543 * @since 9
544 */
545 public long transferTo(OutputStream out) throws IOException {
546 Objects.requireNonNull(out, "out");
547 long transferred = 0;
548 byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
549 int read;
550 while ((read = this.read(buffer, 0, DEFAULT_BUFFER_SIZE)) >= 0) {
551 out.write(buffer, 0, read);
552 transferred += read;
553 }
554 return transferred;
555 }
556 }