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 int total = 0;
237 int n;
238 do {
239 byte[] buf = new byte[DEFAULT_BUFFER_SIZE];
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 if (result == null) {
253 result = buf;
254 } else {
255 if (bufs == null) {
256 bufs = new ArrayList<>();
257 bufs.add(result);
258 }
259 bufs.add(buf);
260 }
261 }
262 } while (n >= 0); // if the last call to read returned -1, then break
263
264 if (bufs == null) {
265 if (result == null) {
266 return new byte[0];
267 }
268 return result.length == total ?
269 result : Arrays.copyOf(result, total);
270 }
271
272 result = new byte[total];
273 int offset = 0;
274 int remaining = total;
275 for (byte[] b : bufs) {
276 int len = Math.min(b.length, remaining);
277 System.arraycopy(b, 0, result, offset, len);
278 offset += len;
279 remaining -= len;
280 }
281
282 return result;
283 }
284
285 /**
286 * Reads the requested number of bytes from the input stream into the given
287 * byte array. This method blocks until {@code len} bytes of input data have
288 * been read, end of stream is detected, or an exception is thrown. The
289 * number of bytes actually read, possibly zero, is returned. This method
290 * does not close the input stream.
291 *
292 * <p> In the case where end of stream is reached before {@code len} bytes
293 * have been read, then the actual number of bytes read will be returned.
294 * When this stream reaches end of stream, further invocations of this
295 * method will return zero.
296 *
297 * <p> If {@code len} is zero, then no bytes are read and {@code 0} is
298 * returned; otherwise, there is an attempt to read up to {@code len} bytes.
299 *
300 * <p> The first byte read is stored into element {@code b[off]}, the next
301 * one in to {@code b[off+1]}, and so on. The number of bytes read is, at
302 * most, equal to {@code len}. Let <i>k</i> be the number of bytes actually
303 * read; these bytes will be stored in elements {@code b[off]} through
304 * {@code b[off+}<i>k</i>{@code -1]}, leaving elements {@code b[off+}<i>k</i>
305 * {@code ]} through {@code b[off+len-1]} unaffected.
306 *
307 * <p> The behavior for the case where the input stream is <i>asynchronously
308 * closed</i>, or the thread interrupted during the read, is highly input
309 * stream specific, and therefore not specified.
310 *
311 * <p> If an I/O error occurs reading from the input stream, then it may do
312 * so after some, but not all, bytes of {@code b} have been updated with
313 * data from the input stream. Consequently the input stream and {@code b}
314 * may be in an inconsistent state. It is strongly recommended that the
315 * stream be promptly closed if an I/O error occurs.
316 *
317 * @param b the byte array into which the data is read
318 * @param off the start offset in {@code b} at which the data is written
319 * @param len the maximum number of bytes to read
320 * @return the actual number of bytes read into the buffer
321 * @throws IOException if an I/O error occurs
322 * @throws NullPointerException if {@code b} is {@code null}
323 * @throws IndexOutOfBoundsException If {@code off} is negative, {@code len}
324 * is negative, or {@code len} is greater than {@code b.length - off}
325 *
326 * @since 9
327 */
328 public int readNBytes(byte[] b, int off, int len) throws IOException {
329 Objects.requireNonNull(b);
330 Objects.checkFromIndexSize(off, len, b.length);
331
332 int n = 0;
333 while (n < len) {
334 int count = read(b, off + n, len - n);
335 if (count < 0)
336 break;
337 n += count;
338 }
339 return n;
340 }
341
342 /**
343 * Skips over and discards <code>n</code> bytes of data from this input
344 * stream. The <code>skip</code> method may, for a variety of reasons, end
345 * up skipping over some smaller number of bytes, possibly <code>0</code>.
346 * This may result from any of a number of conditions; reaching end of file
347 * before <code>n</code> bytes have been skipped is only one possibility.
348 * The actual number of bytes skipped is returned. If {@code n} is
349 * negative, the {@code skip} method for class {@code InputStream} always
350 * returns 0, and no bytes are skipped. Subclasses may handle the negative
351 * value differently.
352 *
353 * <p> The <code>skip</code> method implementation of this class creates a
354 * byte array and then repeatedly reads into it until <code>n</code> bytes
355 * have been read or the end of the stream has been reached. Subclasses are
356 * encouraged to provide a more efficient implementation of this method.
357 * For instance, the implementation may depend on the ability to seek.
358 *
359 * @param n the number of bytes to be skipped.
360 * @return the actual number of bytes skipped.
361 * @throws IOException if an I/O error occurs.
362 */
363 public long skip(long n) throws IOException {
364
365 long remaining = n;
366 int nr;
367
368 if (n <= 0) {
369 return 0;
370 }
371
372 int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining);
373 byte[] skipBuffer = new byte[size];
374 while (remaining > 0) {
375 nr = read(skipBuffer, 0, (int)Math.min(size, remaining));
376 if (nr < 0) {
377 break;
378 }
379 remaining -= nr;
380 }
381
382 return n - remaining;
383 }
384
385 /**
386 * Returns an estimate of the number of bytes that can be read (or
387 * skipped over) from this input stream without blocking by the next
388 * invocation of a method for this input stream. The next invocation
389 * might be the same thread or another thread. A single read or skip of this
390 * many bytes will not block, but may read or skip fewer bytes.
391 *
392 * <p> Note that while some implementations of {@code InputStream} will return
393 * the total number of bytes in the stream, many will not. It is
394 * never correct to use the return value of this method to allocate
395 * a buffer intended to hold all data in this stream.
396 *
397 * <p> A subclass' implementation of this method may choose to throw an
398 * {@link IOException} if this input stream has been closed by
399 * invoking the {@link #close()} method.
400 *
401 * <p> The {@code available} method for class {@code InputStream} always
402 * returns {@code 0}.
403 *
404 * <p> This method should be overridden by subclasses.
405 *
406 * @return an estimate of the number of bytes that can be read (or skipped
407 * over) from this input stream without blocking or {@code 0} when
408 * it reaches the end of the input stream.
409 * @exception IOException if an I/O error occurs.
410 */
411 public int available() throws IOException {
412 return 0;
413 }
414
415 /**
416 * Closes this input stream and releases any system resources associated
417 * with the stream.
418 *
419 * <p> The <code>close</code> method of <code>InputStream</code> does
420 * nothing.
421 *
422 * @exception IOException if an I/O error occurs.
423 */
424 public void close() throws IOException {}
425
426 /**
427 * Marks the current position in this input stream. A subsequent call to
428 * the <code>reset</code> method repositions this stream at the last marked
429 * position so that subsequent reads re-read the same bytes.
430 *
431 * <p> The <code>readlimit</code> arguments tells this input stream to
432 * allow that many bytes to be read before the mark position gets
433 * invalidated.
434 *
435 * <p> The general contract of <code>mark</code> is that, if the method
436 * <code>markSupported</code> returns <code>true</code>, the stream somehow
437 * remembers all the bytes read after the call to <code>mark</code> and
438 * stands ready to supply those same bytes again if and whenever the method
439 * <code>reset</code> is called. However, the stream is not required to
440 * remember any data at all if more than <code>readlimit</code> bytes are
441 * read from the stream before <code>reset</code> is called.
442 *
443 * <p> Marking a closed stream should not have any effect on the stream.
444 *
445 * <p> The <code>mark</code> method of <code>InputStream</code> does
446 * nothing.
447 *
448 * @param readlimit the maximum limit of bytes that can be read before
449 * the mark position becomes invalid.
450 * @see java.io.InputStream#reset()
451 */
452 public synchronized void mark(int readlimit) {}
453
454 /**
455 * Repositions this stream to the position at the time the
456 * <code>mark</code> method was last called on this input stream.
457 *
458 * <p> The general contract of <code>reset</code> is:
459 *
460 * <ul>
461 * <li> If the method <code>markSupported</code> returns
462 * <code>true</code>, then:
463 *
464 * <ul><li> If the method <code>mark</code> has not been called since
465 * the stream was created, or the number of bytes read from the stream
466 * since <code>mark</code> was last called is larger than the argument
467 * to <code>mark</code> at that last call, then an
468 * <code>IOException</code> might be thrown.
469 *
470 * <li> If such an <code>IOException</code> is not thrown, then the
471 * stream is reset to a state such that all the bytes read since the
472 * most recent call to <code>mark</code> (or since the start of the
473 * file, if <code>mark</code> has not been called) will be resupplied
474 * to subsequent callers of the <code>read</code> method, followed by
475 * any bytes that otherwise would have been the next input data as of
476 * the time of the call to <code>reset</code>. </ul>
477 *
478 * <li> If the method <code>markSupported</code> returns
479 * <code>false</code>, then:
480 *
481 * <ul><li> The call to <code>reset</code> may throw an
482 * <code>IOException</code>.
483 *
484 * <li> If an <code>IOException</code> is not thrown, then the stream
485 * is reset to a fixed state that depends on the particular type of the
486 * input stream and how it was created. The bytes that will be supplied
487 * to subsequent callers of the <code>read</code> method depend on the
488 * particular type of the input stream. </ul></ul>
489 *
490 * <p>The method <code>reset</code> for class <code>InputStream</code>
491 * does nothing except throw an <code>IOException</code>.
492 *
493 * @exception IOException if this stream has not been marked or if the
494 * mark has been invalidated.
495 * @see java.io.InputStream#mark(int)
496 * @see java.io.IOException
497 */
498 public synchronized void reset() throws IOException {
499 throw new IOException("mark/reset not supported");
500 }
501
502 /**
503 * Tests if this input stream supports the <code>mark</code> and
504 * <code>reset</code> methods. Whether or not <code>mark</code> and
505 * <code>reset</code> are supported is an invariant property of a
506 * particular input stream instance. The <code>markSupported</code> method
507 * of <code>InputStream</code> returns <code>false</code>.
508 *
509 * @return <code>true</code> if this stream instance supports the mark
510 * and reset methods; <code>false</code> otherwise.
511 * @see java.io.InputStream#mark(int)
512 * @see java.io.InputStream#reset()
513 */
514 public boolean markSupported() {
515 return false;
516 }
517
518 /**
519 * Reads all bytes from this input stream and writes the bytes to the
520 * given output stream in the order that they are read. On return, this
521 * input stream will be at end of stream. This method does not close either
522 * stream.
523 * <p>
524 * This method may block indefinitely reading from the input stream, or
525 * writing to the output stream. The behavior for the case where the input
526 * and/or output stream is <i>asynchronously closed</i>, or the thread
527 * interrupted during the transfer, is highly input and output stream
528 * specific, and therefore not specified.
529 * <p>
530 * If an I/O error occurs reading from the input stream or writing to the
531 * output stream, then it may do so after some bytes have been read or
532 * written. Consequently the input stream may not be at end of stream and
533 * one, or both, streams may be in an inconsistent state. It is strongly
534 * recommended that both streams be promptly closed if an I/O error occurs.
535 *
536 * @param out the output stream, non-null
537 * @return the number of bytes transferred
538 * @throws IOException if an I/O error occurs when reading or writing
539 * @throws NullPointerException if {@code out} is {@code null}
540 *
541 * @since 9
542 */
543 public long transferTo(OutputStream out) throws IOException {
544 Objects.requireNonNull(out, "out");
545 long transferred = 0;
546 byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
547 int read;
548 while ((read = this.read(buffer, 0, DEFAULT_BUFFER_SIZE)) >= 0) {
549 out.write(buffer, 0, read);
550 transferred += read;
551 }
552 return transferred;
553 }
554 }