1 /*
2 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.io;
27
28 import java.util.Arrays;
29 import java.util.Objects;
30
31 /**
32 * This abstract class is the superclass of all classes representing
33 * an input stream of bytes.
34 *
35 * <p> Applications that need to define a subclass of <code>InputStream</code>
36 * must always provide a method that returns the next byte of input.
37 *
38 * @author Arthur van Hoff
39 * @see java.io.BufferedInputStream
40 * @see java.io.ByteArrayInputStream
41 * @see java.io.DataInputStream
42 * @see java.io.FilterInputStream
43 * @see java.io.InputStream#read()
44 * @see java.io.OutputStream
45 * @see java.io.PushbackInputStream
46 * @since 1.0
47 */
48 public abstract class InputStream implements Closeable {
49
50 // MAX_SKIP_BUFFER_SIZE is used to determine the maximum buffer size to
51 // use when skipping.
52 private static final int MAX_SKIP_BUFFER_SIZE = 2048;
53
54 private static final int DEFAULT_BUFFER_SIZE = 8192;
55
56 /**
57 * Reads the next byte of data from the input stream. The value byte is
58 * returned as an <code>int</code> in the range <code>0</code> to
59 * <code>255</code>. If no byte is available because the end of the stream
60 * has been reached, the value <code>-1</code> is returned. This method
61 * blocks until input data is available, the end of the stream is detected,
62 * or an exception is thrown.
63 *
64 * <p> A subclass must provide an implementation of this method.
65 *
66 * @return the next byte of data, or <code>-1</code> if the end of the
67 * stream is reached.
68 * @exception IOException if an I/O error occurs.
69 */
70 public abstract int read() throws IOException;
71
72 /**
73 * Reads some number of bytes from the input stream and stores them into
74 * the buffer array <code>b</code>. The number of bytes actually read is
75 * returned as an integer. This method blocks until input data is
76 * available, end of file is detected, or an exception is thrown.
77 *
78 * <p> If the length of <code>b</code> is zero, then no bytes are read and
79 * <code>0</code> is returned; otherwise, there is an attempt to read at
80 * least one byte. If no byte is available because the stream is at the
81 * end of the file, the value <code>-1</code> is returned; otherwise, at
82 * least one byte is read and stored into <code>b</code>.
83 *
84 * <p> The first byte read is stored into element <code>b[0]</code>, the
85 * next one into <code>b[1]</code>, and so on. The number of bytes read is,
86 * at most, equal to the length of <code>b</code>. Let <i>k</i> be the
87 * number of bytes actually read; these bytes will be stored in elements
88 * <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>,
89 * leaving elements <code>b[</code><i>k</i><code>]</code> through
90 * <code>b[b.length-1]</code> unaffected.
91 *
92 * <p> The <code>read(b)</code> method for class <code>InputStream</code>
93 * has the same effect as: <pre><code> read(b, 0, b.length) </code></pre>
94 *
95 * @param b the buffer into which the data is read.
96 * @return the total number of bytes read into the buffer, or
97 * <code>-1</code> if there is no more data because the end of
98 * the stream has been reached.
99 * @exception IOException If the first byte cannot be read for any reason
100 * other than the end of the file, if the input stream has been closed, or
101 * if some other I/O error occurs.
102 * @exception NullPointerException if <code>b</code> is <code>null</code>.
103 * @see java.io.InputStream#read(byte[], int, int)
104 */
105 public int read(byte b[]) throws IOException {
106 return read(b, 0, b.length);
107 }
108
109 /**
110 * Reads up to <code>len</code> bytes of data from the input stream into
111 * an array of bytes. An attempt is made to read as many as
112 * <code>len</code> bytes, but a smaller number may be read.
113 * The number of bytes actually read is returned as an integer.
114 *
115 * <p> This method blocks until input data is available, end of file is
116 * detected, or an exception is thrown.
117 *
118 * <p> If <code>len</code> is zero, then no bytes are read and
119 * <code>0</code> is returned; otherwise, there is an attempt to read at
120 * least one byte. If no byte is available because the stream is at end of
121 * file, the value <code>-1</code> is returned; otherwise, at least one
122 * byte is read and stored into <code>b</code>.
123 *
124 * <p> The first byte read is stored into element <code>b[off]</code>, the
125 * next one into <code>b[off+1]</code>, and so on. The number of bytes read
126 * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
127 * bytes actually read; these bytes will be stored in elements
128 * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
129 * leaving elements <code>b[off+</code><i>k</i><code>]</code> through
130 * <code>b[off+len-1]</code> unaffected.
131 *
132 * <p> In every case, elements <code>b[0]</code> through
133 * <code>b[off]</code> and elements <code>b[off+len]</code> through
134 * <code>b[b.length-1]</code> are unaffected.
135 *
136 * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method
137 * for class <code>InputStream</code> simply calls the method
138 * <code>read()</code> repeatedly. If the first such call results in an
139 * <code>IOException</code>, that exception is returned from the call to
140 * the <code>read(b,</code> <code>off,</code> <code>len)</code> method. If
141 * any subsequent call to <code>read()</code> results in a
142 * <code>IOException</code>, the exception is caught and treated as if it
143 * were end of file; the bytes read up to that point are stored into
144 * <code>b</code> and the number of bytes read before the exception
145 * occurred is returned. The default implementation of this method blocks
146 * until the requested amount of input data <code>len</code> has been read,
147 * end of file is detected, or an exception is thrown. Subclasses are encouraged
148 * to provide a more efficient implementation of this method.
149 *
150 * @param b the buffer into which the data is read.
151 * @param off the start offset in array <code>b</code>
152 * at which the data is written.
153 * @param len the maximum number of bytes to read.
154 * @return the total number of bytes read into the buffer, or
155 * <code>-1</code> if there is no more data because the end of
156 * the stream has been reached.
157 * @exception IOException If the first byte cannot be read for any reason
158 * other than end of file, or if the input stream has been closed, or if
159 * some other I/O error occurs.
160 * @exception NullPointerException If <code>b</code> is <code>null</code>.
161 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
162 * <code>len</code> is negative, or <code>len</code> is greater than
163 * <code>b.length - off</code>
164 * @see java.io.InputStream#read()
165 */
166 public int read(byte b[], int off, int len) throws IOException {
167 if (b == null) {
168 throw new NullPointerException();
169 } else if (off < 0 || len < 0 || len > b.length - off) {
170 throw new IndexOutOfBoundsException();
171 } else 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 byte[] buf = new byte[DEFAULT_BUFFER_SIZE];
235 int capacity = buf.length;
236 int nread = 0;
237 int n;
238 for (;;) {
239 // read to EOF which may read more or less than initial buffer size
240 while ((n = read(buf, nread, capacity - nread)) > 0)
241 nread += n;
242
243 // if the last call to read returned -1, then we're done
244 if (n < 0)
245 break;
246
247 // need to allocate a larger buffer
248 if (capacity <= MAX_BUFFER_SIZE - capacity) {
249 capacity = capacity << 1;
250 } else {
251 if (capacity == MAX_BUFFER_SIZE)
252 throw new OutOfMemoryError("Required array size too large");
253 capacity = MAX_BUFFER_SIZE;
254 }
255 buf = Arrays.copyOf(buf, capacity);
256 }
257 return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
258 }
259
260 /**
261 * Reads the requested number of bytes from the input stream into the given
262 * byte array. This method blocks until {@code len} bytes of input data have
263 * been read, end of stream is detected, or an exception is thrown. The
264 * number of bytes actually read, possibly zero, is returned. This method
265 * does not close the input stream.
266 *
267 * <p> In the case where end of stream is reached before {@code len} bytes
268 * have been read, then the actual number of bytes read will be returned.
269 * When this stream reaches end of stream, further invocations of this
270 * method will return zero.
271 *
272 * <p> If {@code len} is zero, then no bytes are read and {@code 0} is
273 * returned; otherwise, there is an attempt to read up to {@code len} bytes.
274 *
275 * <p> The first byte read is stored into element {@code b[off]}, the next
276 * one in to {@code b[off+1]}, and so on. The number of bytes read is, at
277 * most, equal to {@code len}. Let <i>k</i> be the number of bytes actually
278 * read; these bytes will be stored in elements {@code b[off]} through
279 * {@code b[off+}<i>k</i>{@code -1]}, leaving elements {@code b[off+}<i>k</i>
280 * {@code ]} through {@code b[off+len-1]} unaffected.
281 *
282 * <p> The behavior for the case where the input stream is <i>asynchronously
283 * closed</i>, or the thread interrupted during the read, is highly input
284 * stream specific, and therefore not specified.
285 *
286 * <p> If an I/O error occurs reading from the input stream, then it may do
287 * so after some, but not all, bytes of {@code b} have been updated with
288 * data from the input stream. Consequently the input stream and {@code b}
289 * may be in an inconsistent state. It is strongly recommended that the
290 * stream be promptly closed if an I/O error occurs.
291 *
292 * @param b the byte array into which the data is read
293 * @param off the start offset in {@code b} at which the data is written
294 * @param len the maximum number of bytes to read
295 * @return the actual number of bytes read into the buffer
296 * @throws IOException if an I/O error occurs
297 * @throws NullPointerException if {@code b} is {@code null}
298 * @throws IndexOutOfBoundsException If {@code off} is negative, {@code len}
299 * is negative, or {@code len} is greater than {@code b.length - off}
300 *
301 * @since 9
302 */
303 public int readNBytes(byte[] b, int off, int len) throws IOException {
304 Objects.requireNonNull(b);
305 if (off < 0 || len < 0 || len > b.length - off)
306 throw new IndexOutOfBoundsException();
307 int n = 0;
308 while (n < len) {
309 int count = read(b, off + n, len - n);
310 if (count < 0)
311 break;
312 n += count;
313 }
314 return n;
315 }
316
317 /**
318 * Skips over and discards <code>n</code> bytes of data from this input
319 * stream. The <code>skip</code> method may, for a variety of reasons, end
320 * up skipping over some smaller number of bytes, possibly <code>0</code>.
321 * This may result from any of a number of conditions; reaching end of file
322 * before <code>n</code> bytes have been skipped is only one possibility.
323 * The actual number of bytes skipped is returned. If {@code n} is
324 * negative, the {@code skip} method for class {@code InputStream} always
325 * returns 0, and no bytes are skipped. Subclasses may handle the negative
326 * value differently.
327 *
328 * <p> The <code>skip</code> method of this class creates a
329 * byte array and then repeatedly reads into it until <code>n</code> bytes
330 * have been read or the end of the stream has been reached. Subclasses are
331 * encouraged to provide a more efficient implementation of this method.
332 * For instance, the implementation may depend on the ability to seek.
333 *
334 * @param n the number of bytes to be skipped.
335 * @return the actual number of bytes skipped.
336 * @exception IOException if the stream does not support seek,
337 * or if some other I/O error occurs.
338 */
339 public long skip(long n) throws IOException {
340
341 long remaining = n;
342 int nr;
343
344 if (n <= 0) {
345 return 0;
346 }
347
348 int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining);
349 byte[] skipBuffer = new byte[size];
350 while (remaining > 0) {
351 nr = read(skipBuffer, 0, (int)Math.min(size, remaining));
352 if (nr < 0) {
353 break;
354 }
355 remaining -= nr;
356 }
357
358 return n - remaining;
359 }
360
361 /**
362 * Returns an estimate of the number of bytes that can be read (or
363 * skipped over) from this input stream without blocking by the next
364 * invocation of a method for this input stream. The next invocation
365 * might be the same thread or another thread. A single read or skip of this
366 * many bytes will not block, but may read or skip fewer bytes.
367 *
368 * <p> Note that while some implementations of {@code InputStream} will return
369 * the total number of bytes in the stream, many will not. It is
370 * never correct to use the return value of this method to allocate
371 * a buffer intended to hold all data in this stream.
372 *
373 * <p> A subclass' implementation of this method may choose to throw an
374 * {@link IOException} if this input stream has been closed by
375 * invoking the {@link #close()} method.
376 *
377 * <p> The {@code available} method for class {@code InputStream} always
378 * returns {@code 0}.
379 *
380 * <p> This method should be overridden by subclasses.
381 *
382 * @return an estimate of the number of bytes that can be read (or skipped
383 * over) from this input stream without blocking or {@code 0} when
384 * it reaches the end of the input stream.
385 * @exception IOException if an I/O error occurs.
386 */
387 public int available() throws IOException {
388 return 0;
389 }
390
391 /**
392 * Closes this input stream and releases any system resources associated
393 * with the stream.
394 *
395 * <p> The <code>close</code> method of <code>InputStream</code> does
396 * nothing.
397 *
398 * @exception IOException if an I/O error occurs.
399 */
400 public void close() throws IOException {}
401
402 /**
403 * Marks the current position in this input stream. A subsequent call to
404 * the <code>reset</code> method repositions this stream at the last marked
405 * position so that subsequent reads re-read the same bytes.
406 *
407 * <p> The <code>readlimit</code> arguments tells this input stream to
408 * allow that many bytes to be read before the mark position gets
409 * invalidated.
410 *
411 * <p> The general contract of <code>mark</code> is that, if the method
412 * <code>markSupported</code> returns <code>true</code>, the stream somehow
413 * remembers all the bytes read after the call to <code>mark</code> and
414 * stands ready to supply those same bytes again if and whenever the method
415 * <code>reset</code> is called. However, the stream is not required to
416 * remember any data at all if more than <code>readlimit</code> bytes are
417 * read from the stream before <code>reset</code> is called.
418 *
419 * <p> Marking a closed stream should not have any effect on the stream.
420 *
421 * <p> The <code>mark</code> method of <code>InputStream</code> does
422 * nothing.
423 *
424 * @param readlimit the maximum limit of bytes that can be read before
425 * the mark position becomes invalid.
426 * @see java.io.InputStream#reset()
427 */
428 public synchronized void mark(int readlimit) {}
429
430 /**
431 * Repositions this stream to the position at the time the
432 * <code>mark</code> method was last called on this input stream.
433 *
434 * <p> The general contract of <code>reset</code> is:
435 *
436 * <ul>
437 * <li> If the method <code>markSupported</code> returns
438 * <code>true</code>, then:
439 *
440 * <ul><li> If the method <code>mark</code> has not been called since
441 * the stream was created, or the number of bytes read from the stream
442 * since <code>mark</code> was last called is larger than the argument
443 * to <code>mark</code> at that last call, then an
444 * <code>IOException</code> might be thrown.
445 *
446 * <li> If such an <code>IOException</code> is not thrown, then the
447 * stream is reset to a state such that all the bytes read since the
448 * most recent call to <code>mark</code> (or since the start of the
449 * file, if <code>mark</code> has not been called) will be resupplied
450 * to subsequent callers of the <code>read</code> method, followed by
451 * any bytes that otherwise would have been the next input data as of
452 * the time of the call to <code>reset</code>. </ul>
453 *
454 * <li> If the method <code>markSupported</code> returns
455 * <code>false</code>, then:
456 *
457 * <ul><li> The call to <code>reset</code> may throw an
458 * <code>IOException</code>.
459 *
460 * <li> If an <code>IOException</code> is not thrown, then the stream
461 * is reset to a fixed state that depends on the particular type of the
462 * input stream and how it was created. The bytes that will be supplied
463 * to subsequent callers of the <code>read</code> method depend on the
464 * particular type of the input stream. </ul></ul>
465 *
466 * <p>The method <code>reset</code> for class <code>InputStream</code>
467 * does nothing except throw an <code>IOException</code>.
468 *
469 * @exception IOException if this stream has not been marked or if the
470 * mark has been invalidated.
471 * @see java.io.InputStream#mark(int)
472 * @see java.io.IOException
473 */
474 public synchronized void reset() throws IOException {
475 throw new IOException("mark/reset not supported");
476 }
477
478 /**
479 * Tests if this input stream supports the <code>mark</code> and
480 * <code>reset</code> methods. Whether or not <code>mark</code> and
481 * <code>reset</code> are supported is an invariant property of a
482 * particular input stream instance. The <code>markSupported</code> method
483 * of <code>InputStream</code> returns <code>false</code>.
484 *
485 * @return <code>true</code> if this stream instance supports the mark
486 * and reset methods; <code>false</code> otherwise.
487 * @see java.io.InputStream#mark(int)
488 * @see java.io.InputStream#reset()
489 */
490 public boolean markSupported() {
491 return false;
492 }
493
494 /**
495 * Reads all bytes from this input stream and writes the bytes to the
496 * given output stream in the order that they are read. On return, this
497 * input stream will be at end of stream. This method does not close either
498 * stream.
499 * <p>
500 * This method may block indefinitely reading from the input stream, or
501 * writing to the output stream. The behavior for the case where the input
502 * and/or output stream is <i>asynchronously closed</i>, or the thread
503 * interrupted during the transfer, is highly input and output stream
504 * specific, and therefore not specified.
505 * <p>
506 * If an I/O error occurs reading from the input stream or writing to the
507 * output stream, then it may do so after some bytes have been read or
508 * written. Consequently the input stream may not be at end of stream and
509 * one, or both, streams may be in an inconsistent state. It is strongly
510 * recommended that both streams be promptly closed if an I/O error occurs.
511 *
512 * @param out the output stream, non-null
513 * @return the number of bytes transferred
514 * @throws IOException if an I/O error occurs when reading or writing
515 * @throws NullPointerException if {@code out} is {@code null}
516 *
517 * @since 9
518 */
519 public long transferTo(OutputStream out) throws IOException {
520 Objects.requireNonNull(out, "out");
521 long transferred = 0;
522 byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
523 int read;
524 while ((read = this.read(buffer, 0, DEFAULT_BUFFER_SIZE)) >= 0) {
525 out.write(buffer, 0, read);
526 transferred += read;
527 }
528 return transferred;
529 }
530 }