1 /*
2 * Copyright (c) 1996, 2019, 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
29 /**
30 * Piped character-input streams.
31 *
32 * @author Mark Reinhold
33 * @since 1.1
34 */
35
36 public class PipedReader extends Reader {
37 boolean closedByWriter = false;
38 boolean closedByReader = false;
39 boolean connected = false;
40
41 /* REMIND: identification of the read and write sides needs to be
42 more sophisticated. Either using thread groups (but what about
43 pipes within a thread?) or using finalization (but it may be a
44 long time until the next GC). */
45 Thread readSide;
46 Thread writeSide;
47
48 /**
49 * The size of the pipe's circular input buffer.
50 */
51 private static final int DEFAULT_PIPE_SIZE = 1024;
52
53 /**
54 * The circular buffer into which incoming data is placed.
55 */
56 char buffer[];
57
58 /**
59 * The index of the position in the circular buffer at which the
60 * next character of data will be stored when received from the connected
61 * piped writer. <code>in<0</code> implies the buffer is empty,
62 * {@code in==out} implies the buffer is full
63 */
64 int in = -1;
65
66 /**
67 * The index of the position in the circular buffer at which the next
68 * character of data will be read by this piped reader.
69 */
70 int out = 0;
71
72 /**
73 * Creates a {@code PipedReader} so
74 * that it is connected to the piped writer
75 * {@code src}. Data written to {@code src}
76 * will then be available as input from this stream.
77 *
78 * @param src the stream to connect to.
79 * @throws IOException if an I/O error occurs.
80 */
81 public PipedReader(PipedWriter src) throws IOException {
82 this(src, DEFAULT_PIPE_SIZE);
83 }
84
85 /**
86 * Creates a {@code PipedReader} so that it is connected
87 * to the piped writer {@code src} and uses the specified
88 * pipe size for the pipe's buffer. Data written to {@code src}
89 * will then be available as input from this stream.
90
91 * @param src the stream to connect to.
92 * @param pipeSize the size of the pipe's buffer.
93 * @throws IOException if an I/O error occurs.
94 * @throws IllegalArgumentException if {@code pipeSize <= 0}.
95 * @since 1.6
96 */
97 public PipedReader(PipedWriter src, int pipeSize) throws IOException {
98 initPipe(pipeSize);
99 connect(src);
100 }
101
102
103 /**
104 * Creates a {@code PipedReader} so
105 * that it is not yet {@linkplain #connect(java.io.PipedWriter)
106 * connected}. It must be {@linkplain java.io.PipedWriter#connect(
107 * java.io.PipedReader) connected} to a {@code PipedWriter}
108 * before being used.
109 */
110 public PipedReader() {
111 initPipe(DEFAULT_PIPE_SIZE);
112 }
113
114 /**
115 * Creates a {@code PipedReader} so that it is not yet
116 * {@link #connect(java.io.PipedWriter) connected} and uses
117 * the specified pipe size for the pipe's buffer.
118 * It must be {@linkplain java.io.PipedWriter#connect(
119 * java.io.PipedReader) connected} to a {@code PipedWriter}
120 * before being used.
121 *
122 * @param pipeSize the size of the pipe's buffer.
123 * @throws IllegalArgumentException if {@code pipeSize <= 0}.
124 * @since 1.6
125 */
126 public PipedReader(int pipeSize) {
127 initPipe(pipeSize);
128 }
129
130 private void initPipe(int pipeSize) {
131 if (pipeSize <= 0) {
132 throw new IllegalArgumentException("Pipe size <= 0");
133 }
134 buffer = new char[pipeSize];
135 }
136
137 /**
138 * Causes this piped reader to be connected
139 * to the piped writer {@code src}.
140 * If this object is already connected to some
141 * other piped writer, an {@code IOException}
142 * is thrown.
143 * <p>
144 * If {@code src} is an
145 * unconnected piped writer and {@code snk}
146 * is an unconnected piped reader, they
147 * may be connected by either the call:
148 *
149 * <pre>{@code snk.connect(src)} </pre>
150 * <p>
151 * or the call:
152 *
153 * <pre>{@code src.connect(snk)} </pre>
154 * <p>
155 * The two calls have the same effect.
156 *
157 * @param src The piped writer to connect to.
158 * @throws IOException if an I/O error occurs.
159 */
160 public void connect(PipedWriter src) throws IOException {
161 src.connect(this);
162 }
163
164 /**
165 * Receives a char of data. This method will block if no input is
166 * available.
167 */
168 synchronized void receive(int c) throws IOException {
169 if (!connected) {
170 throw new IOException("Pipe not connected");
171 } else if (closedByWriter || closedByReader) {
172 throw new IOException("Pipe closed");
173 } else if (readSide != null && !readSide.isAlive()) {
174 throw new IOException("Read end dead");
175 }
176
177 writeSide = Thread.currentThread();
178 while (in == out) {
179 if ((readSide != null) && !readSide.isAlive()) {
180 throw new IOException("Pipe broken");
181 }
182 /* full: kick any waiting readers */
183 notifyAll();
184 try {
185 wait(1000);
186 } catch (InterruptedException ex) {
187 throw new java.io.InterruptedIOException();
188 }
189 }
190 if (in < 0) {
191 in = 0;
192 out = 0;
193 }
194 buffer[in++] = (char) c;
195 if (in >= buffer.length) {
196 in = 0;
197 }
198 }
199
200 /**
201 * Receives data into an array of characters. This method will
202 * block until some input is available.
203 */
204 synchronized void receive(char c[], int off, int len) throws IOException {
205 while (--len >= 0) {
206 receive(c[off++]);
207 }
208 }
209
210 /**
211 * Notifies all waiting threads that the last character of data has been
212 * received.
213 */
214 synchronized void receivedLast() {
215 closedByWriter = true;
216 notifyAll();
217 }
218
219 /**
220 * Reads the next character of data from this piped stream.
221 * If no character is available because the end of the stream
222 * has been reached, the value {@code -1} is returned.
223 * This method blocks until input data is available, the end of
224 * the stream is detected, or an exception is thrown.
225 *
226 * @return the next character of data, or {@code -1} if the end of the
227 * stream is reached.
228 * @throws IOException if the pipe is
229 * <a href=PipedInputStream.html#BROKEN> {@code broken}</a>,
230 * {@link #connect(java.io.PipedWriter) unconnected}, closed,
231 * or an I/O error occurs.
232 */
233 public synchronized int read() throws IOException {
234 if (!connected) {
235 throw new IOException("Pipe not connected");
236 } else if (closedByReader) {
237 throw new IOException("Pipe closed");
238 } else if (writeSide != null && !writeSide.isAlive()
239 && !closedByWriter && (in < 0)) {
240 throw new IOException("Write end dead");
241 }
242
243 readSide = Thread.currentThread();
244 int trials = 2;
245 while (in < 0) {
246 if (closedByWriter) {
247 /* closed by writer, return EOF */
248 return -1;
249 }
250 if ((writeSide != null) && (!writeSide.isAlive()) && (--trials < 0)) {
251 throw new IOException("Pipe broken");
252 }
253 /* might be a writer waiting */
254 notifyAll();
255 try {
256 wait(1000);
257 } catch (InterruptedException ex) {
258 throw new java.io.InterruptedIOException();
259 }
260 }
261 int ret = buffer[out++];
262 if (out >= buffer.length) {
263 out = 0;
264 }
265 if (in == out) {
266 /* now empty */
267 in = -1;
268 }
269 return ret;
270 }
271
272 /**
273 * Reads up to {@code len} characters of data from this piped
274 * stream into an array of characters. Less than {@code len} characters
275 * will be read if the end of the data stream is reached or if
276 * {@code len} exceeds the pipe's buffer size. This method
277 * blocks until at least one character of input is available.
278 *
279 * @param cbuf the buffer into which the data is read.
280 * @param off the start offset of the data.
281 * @param len the maximum number of characters read.
282 * @return the total number of characters read into the buffer, or
283 * {@code -1} if there is no more data because the end of
284 * the stream has been reached.
285 * @throws IOException if the pipe is
286 * <a href=PipedInputStream.html#BROKEN> {@code broken}</a>,
287 * {@link #connect(java.io.PipedWriter) unconnected}, closed,
288 * or an I/O error occurs.
289 * @throws IndexOutOfBoundsException {@inheritDoc}
290 */
291 public synchronized int read(char cbuf[], int off, int len) throws IOException {
292 if (!connected) {
293 throw new IOException("Pipe not connected");
294 } else if (closedByReader) {
295 throw new IOException("Pipe closed");
296 } else if (writeSide != null && !writeSide.isAlive()
297 && !closedByWriter && (in < 0)) {
298 throw new IOException("Write end dead");
299 }
300
301 if ((off < 0) || (off > cbuf.length) || (len < 0) ||
302 ((off + len) > cbuf.length) || ((off + len) < 0)) {
303 throw new IndexOutOfBoundsException();
304 } else if (len == 0) {
305 return 0;
306 }
307
308 /* possibly wait on the first character */
309 int c = read();
310 if (c < 0) {
311 return -1;
312 }
313 cbuf[off] = (char)c;
314 int rlen = 1;
315 while ((in >= 0) && (--len > 0)) {
316 cbuf[off + rlen] = buffer[out++];
317 rlen++;
318 if (out >= buffer.length) {
319 out = 0;
320 }
321 if (in == out) {
322 /* now empty */
323 in = -1;
324 }
325 }
326 return rlen;
327 }
328
329 /**
330 * Tell whether this stream is ready to be read. A piped character
331 * stream is ready if the circular buffer is not empty.
332 *
333 * @throws IOException if the pipe is
334 * <a href=PipedInputStream.html#BROKEN> {@code broken}</a>,
335 * {@link #connect(java.io.PipedWriter) unconnected}, or closed.
336 */
337 public synchronized boolean ready() throws IOException {
338 if (!connected) {
339 throw new IOException("Pipe not connected");
340 } else if (closedByReader) {
341 throw new IOException("Pipe closed");
342 } else if (writeSide != null && !writeSide.isAlive()
343 && !closedByWriter && (in < 0)) {
344 throw new IOException("Write end dead");
345 }
346 if (in < 0) {
347 return false;
348 } else {
349 return true;
350 }
351 }
352
353 /**
354 * Closes this piped stream and releases any system resources
355 * associated with the stream.
356 *
357 * @throws IOException if an I/O error occurs.
358 */
359 public void close() throws IOException {
360 in = -1;
361 closedByReader = true;
362 }
363 }