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.Objects;
29
30 /**
31 * This abstract class is the superclass of all classes representing
32 * an input stream of bytes.
33 *
34 * <p> Applications that need to define a subclass of <code>InputStream</code>
35 * must always provide a method that returns the next byte of input.
36 *
37 * @author Arthur van Hoff
38 * @see java.io.BufferedInputStream
39 * @see java.io.ByteArrayInputStream
40 * @see java.io.DataInputStream
41 * @see java.io.FilterInputStream
42 * @see java.io.InputStream#read()
43 * @see java.io.OutputStream
44 * @see java.io.PushbackInputStream
45 * @since 1.0
46 */
47 public abstract class InputStream implements Closeable {
48
49 // MAX_SKIP_BUFFER_SIZE is used to determine the maximum buffer size to
50 // use when skipping.
51 private static final int MAX_SKIP_BUFFER_SIZE = 2048;
52
53 private static final int TRANSFER_BUFFER_SIZE = 8192;
54
55 /**
56 * Reads the next byte of data from the input stream. The value byte is
57 * returned as an <code>int</code> in the range <code>0</code> to
58 * <code>255</code>. If no byte is available because the end of the stream
59 * has been reached, the value <code>-1</code> is returned. This method
60 * blocks until input data is available, the end of the stream is detected,
61 * or an exception is thrown.
62 *
63 * <p> A subclass must provide an implementation of this method.
64 *
65 * @return the next byte of data, or <code>-1</code> if the end of the
66 * stream is reached.
67 * @exception IOException if an I/O error occurs.
68 */
69 public abstract int read() throws IOException;
70
71 /**
72 * Reads some number of bytes from the input stream and stores them into
73 * the buffer array <code>b</code>. The number of bytes actually read is
74 * returned as an integer. This method blocks until input data is
75 * available, end of file is detected, or an exception is thrown.
76 *
77 * <p> If the length of <code>b</code> is zero, then no bytes are read and
78 * <code>0</code> is returned; otherwise, there is an attempt to read at
79 * least one byte. If no byte is available because the stream is at the
80 * end of the file, the value <code>-1</code> is returned; otherwise, at
81 * least one byte is read and stored into <code>b</code>.
82 *
83 * <p> The first byte read is stored into element <code>b[0]</code>, the
84 * next one into <code>b[1]</code>, and so on. The number of bytes read is,
85 * at most, equal to the length of <code>b</code>. Let <i>k</i> be the
86 * number of bytes actually read; these bytes will be stored in elements
87 * <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>,
88 * leaving elements <code>b[</code><i>k</i><code>]</code> through
89 * <code>b[b.length-1]</code> unaffected.
90 *
91 * <p> The <code>read(b)</code> method for class <code>InputStream</code>
92 * has the same effect as: <pre><code> read(b, 0, b.length) </code></pre>
93 *
94 * @param b the buffer into which the data is read.
95 * @return the total number of bytes read into the buffer, or
96 * <code>-1</code> if there is no more data because the end of
97 * the stream has been reached.
98 * @exception IOException If the first byte cannot be read for any reason
99 * other than the end of the file, if the input stream has been closed, or
100 * if some other I/O error occurs.
101 * @exception NullPointerException if <code>b</code> is <code>null</code>.
102 * @see java.io.InputStream#read(byte[], int, int)
103 */
104 public int read(byte b[]) throws IOException {
105 return read(b, 0, b.length);
106 }
107
108 /**
109 * Reads up to <code>len</code> bytes of data from the input stream into
110 * an array of bytes. An attempt is made to read as many as
111 * <code>len</code> bytes, but a smaller number may be read.
112 * The number of bytes actually read is returned as an integer.
113 *
114 * <p> This method blocks until input data is available, end of file is
115 * detected, or an exception is thrown.
116 *
117 * <p> If <code>len</code> is zero, then no bytes are read and
118 * <code>0</code> is returned; otherwise, there is an attempt to read at
119 * least one byte. If no byte is available because the stream is at end of
120 * file, the value <code>-1</code> is returned; otherwise, at least one
121 * byte is read and stored into <code>b</code>.
122 *
123 * <p> The first byte read is stored into element <code>b[off]</code>, the
124 * next one into <code>b[off+1]</code>, and so on. The number of bytes read
125 * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
126 * bytes actually read; these bytes will be stored in elements
127 * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
128 * leaving elements <code>b[off+</code><i>k</i><code>]</code> through
129 * <code>b[off+len-1]</code> unaffected.
130 *
131 * <p> In every case, elements <code>b[0]</code> through
132 * <code>b[off]</code> and elements <code>b[off+len]</code> through
133 * <code>b[b.length-1]</code> are unaffected.
134 *
135 * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method
136 * for class <code>InputStream</code> simply calls the method
137 * <code>read()</code> repeatedly. If the first such call results in an
138 * <code>IOException</code>, that exception is returned from the call to
139 * the <code>read(b,</code> <code>off,</code> <code>len)</code> method. If
140 * any subsequent call to <code>read()</code> results in a
141 * <code>IOException</code>, the exception is caught and treated as if it
142 * were end of file; the bytes read up to that point are stored into
143 * <code>b</code> and the number of bytes read before the exception
144 * occurred is returned. The default implementation of this method blocks
145 * until the requested amount of input data <code>len</code> has been read,
146 * end of file is detected, or an exception is thrown. Subclasses are encouraged
147 * to provide a more efficient implementation of this method.
148 *
149 * @param b the buffer into which the data is read.
150 * @param off the start offset in array <code>b</code>
151 * at which the data is written.
152 * @param len the maximum number of bytes to read.
153 * @return the total number of bytes read into the buffer, or
154 * <code>-1</code> if there is no more data because the end of
155 * the stream has been reached.
156 * @exception IOException If the first byte cannot be read for any reason
157 * other than end of file, or if the input stream has been closed, or if
158 * some other I/O error occurs.
159 * @exception NullPointerException If <code>b</code> is <code>null</code>.
160 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
161 * <code>len</code> is negative, or <code>len</code> is greater than
162 * <code>b.length - off</code>
163 * @see java.io.InputStream#read()
164 */
165 public int read(byte b[], int off, int len) throws IOException {
166 if (b == null) {
167 throw new NullPointerException();
168 } else if (off < 0 || len < 0 || len > b.length - off) {
169 throw new IndexOutOfBoundsException();
170 } else 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 * Skips over and discards <code>n</code> bytes of data from this input
196 * stream. The <code>skip</code> method may, for a variety of reasons, end
197 * up skipping over some smaller number of bytes, possibly <code>0</code>.
198 * This may result from any of a number of conditions; reaching end of file
199 * before <code>n</code> bytes have been skipped is only one possibility.
200 * The actual number of bytes skipped is returned. If {@code n} is
201 * negative, the {@code skip} method for class {@code InputStream} always
202 * returns 0, and no bytes are skipped. Subclasses may handle the negative
203 * value differently.
204 *
205 * <p> The <code>skip</code> method of this class creates a
206 * byte array and then repeatedly reads into it until <code>n</code> bytes
207 * have been read or the end of the stream has been reached. Subclasses are
208 * encouraged to provide a more efficient implementation of this method.
209 * For instance, the implementation may depend on the ability to seek.
210 *
211 * @param n the number of bytes to be skipped.
212 * @return the actual number of bytes skipped.
213 * @exception IOException if the stream does not support seek,
214 * or if some other I/O error occurs.
215 */
216 public long skip(long n) throws IOException {
217
218 long remaining = n;
219 int nr;
220
221 if (n <= 0) {
222 return 0;
223 }
224
225 int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining);
226 byte[] skipBuffer = new byte[size];
227 while (remaining > 0) {
228 nr = read(skipBuffer, 0, (int)Math.min(size, remaining));
229 if (nr < 0) {
230 break;
231 }
232 remaining -= nr;
233 }
234
235 return n - remaining;
236 }
237
238 /**
239 * Returns an estimate of the number of bytes that can be read (or
240 * skipped over) from this input stream without blocking by the next
241 * invocation of a method for this input stream. The next invocation
242 * might be the same thread or another thread. A single read or skip of this
243 * many bytes will not block, but may read or skip fewer bytes.
244 *
245 * <p> Note that while some implementations of {@code InputStream} will return
246 * the total number of bytes in the stream, many will not. It is
247 * never correct to use the return value of this method to allocate
248 * a buffer intended to hold all data in this stream.
249 *
250 * <p> A subclass' implementation of this method may choose to throw an
251 * {@link IOException} if this input stream has been closed by
252 * invoking the {@link #close()} method.
253 *
254 * <p> The {@code available} method for class {@code InputStream} always
255 * returns {@code 0}.
256 *
257 * <p> This method should be overridden by subclasses.
258 *
259 * @return an estimate of the number of bytes that can be read (or skipped
260 * over) from this input stream without blocking or {@code 0} when
261 * it reaches the end of the input stream.
262 * @exception IOException if an I/O error occurs.
263 */
264 public int available() throws IOException {
265 return 0;
266 }
267
268 /**
269 * Closes this input stream and releases any system resources associated
270 * with the stream.
271 *
272 * <p> The <code>close</code> method of <code>InputStream</code> does
273 * nothing.
274 *
275 * @exception IOException if an I/O error occurs.
276 */
277 public void close() throws IOException {}
278
279 /**
280 * Marks the current position in this input stream. A subsequent call to
281 * the <code>reset</code> method repositions this stream at the last marked
282 * position so that subsequent reads re-read the same bytes.
283 *
284 * <p> The <code>readlimit</code> arguments tells this input stream to
285 * allow that many bytes to be read before the mark position gets
286 * invalidated.
287 *
288 * <p> The general contract of <code>mark</code> is that, if the method
289 * <code>markSupported</code> returns <code>true</code>, the stream somehow
290 * remembers all the bytes read after the call to <code>mark</code> and
291 * stands ready to supply those same bytes again if and whenever the method
292 * <code>reset</code> is called. However, the stream is not required to
293 * remember any data at all if more than <code>readlimit</code> bytes are
294 * read from the stream before <code>reset</code> is called.
295 *
296 * <p> Marking a closed stream should not have any effect on the stream.
297 *
298 * <p> The <code>mark</code> method of <code>InputStream</code> does
299 * nothing.
300 *
301 * @param readlimit the maximum limit of bytes that can be read before
302 * the mark position becomes invalid.
303 * @see java.io.InputStream#reset()
304 */
305 public synchronized void mark(int readlimit) {}
306
307 /**
308 * Repositions this stream to the position at the time the
309 * <code>mark</code> method was last called on this input stream.
310 *
311 * <p> The general contract of <code>reset</code> is:
312 *
313 * <ul>
314 * <li> If the method <code>markSupported</code> returns
315 * <code>true</code>, then:
316 *
317 * <ul><li> If the method <code>mark</code> has not been called since
318 * the stream was created, or the number of bytes read from the stream
319 * since <code>mark</code> was last called is larger than the argument
320 * to <code>mark</code> at that last call, then an
321 * <code>IOException</code> might be thrown.
322 *
323 * <li> If such an <code>IOException</code> is not thrown, then the
324 * stream is reset to a state such that all the bytes read since the
325 * most recent call to <code>mark</code> (or since the start of the
326 * file, if <code>mark</code> has not been called) will be resupplied
327 * to subsequent callers of the <code>read</code> method, followed by
328 * any bytes that otherwise would have been the next input data as of
329 * the time of the call to <code>reset</code>. </ul>
330 *
331 * <li> If the method <code>markSupported</code> returns
332 * <code>false</code>, then:
333 *
334 * <ul><li> The call to <code>reset</code> may throw an
335 * <code>IOException</code>.
336 *
337 * <li> If an <code>IOException</code> is not thrown, then the stream
338 * is reset to a fixed state that depends on the particular type of the
339 * input stream and how it was created. The bytes that will be supplied
340 * to subsequent callers of the <code>read</code> method depend on the
341 * particular type of the input stream. </ul></ul>
342 *
343 * <p>The method <code>reset</code> for class <code>InputStream</code>
344 * does nothing except throw an <code>IOException</code>.
345 *
346 * @exception IOException if this stream has not been marked or if the
347 * mark has been invalidated.
348 * @see java.io.InputStream#mark(int)
349 * @see java.io.IOException
350 */
351 public synchronized void reset() throws IOException {
352 throw new IOException("mark/reset not supported");
353 }
354
355 /**
356 * Tests if this input stream supports the <code>mark</code> and
357 * <code>reset</code> methods. Whether or not <code>mark</code> and
358 * <code>reset</code> are supported is an invariant property of a
359 * particular input stream instance. The <code>markSupported</code> method
360 * of <code>InputStream</code> returns <code>false</code>.
361 *
362 * @return <code>true</code> if this stream instance supports the mark
363 * and reset methods; <code>false</code> otherwise.
364 * @see java.io.InputStream#mark(int)
365 * @see java.io.InputStream#reset()
366 */
367 public boolean markSupported() {
368 return false;
369 }
370
371 /**
372 * Reads all bytes from this input stream and writes the bytes to the
373 * given output stream in the order that they are read. On return, this
374 * input stream will be at end of stream. This method does not close either
375 * stream.
376 * <p>
377 * This method may block indefinitely reading from the input stream, or
378 * writing to the output stream. The behavior for the case where the input
379 * and/or output stream is <i>asynchronously closed</i>, or the thread
380 * interrupted during the transfer, is highly input and output stream
381 * specific, and therefore not specified.
382 * <p>
383 * If an I/O error occurs reading from the input stream or writing to the
384 * output stream, then it may do so after some bytes have been read or
385 * written. Consequently the input stream may not be at end of stream and
386 * one, or both, streams may be in an inconsistent state. It is strongly
387 * recommended that both streams be promptly closed if an I/O error occurs.
388 *
389 * @param out the output stream, non-null
390 * @return the number of bytes transferred
391 * @throws IOException if an I/O error occurs when reading or writing
392 * @throws NullPointerException if {@code out} is {@code null}
393 *
394 * @since 1.9
395 */
396 public long transferTo(OutputStream out) throws IOException {
397 Objects.requireNonNull(out, "out");
398 long transferred = 0;
399 byte[] buffer = new byte[TRANSFER_BUFFER_SIZE];
400 int read;
401 while ((read = this.read(buffer, 0, TRANSFER_BUFFER_SIZE)) >= 0) {
402 out.write(buffer, 0, read);
403 transferred += read;
404 }
405 return transferred;
406 }
407 }