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