001 /* PipedInputStream.java -- Read portion of piped streams.
002 Copyright (C) 1998, 1999, 2000, 2001, 2003, 2005 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038 package java.io;
039
040 // NOTE: This implementation is very similar to that of PipedReader. If you
041 // fix a bug in here, chances are you should make a similar change to the
042 // PipedReader code.
043
044 /**
045 * An input stream that reads its bytes from an output stream
046 * to which it is connected.
047 * <p>
048 * Data is read and written to an internal buffer. It is highly recommended
049 * that the <code>PipedInputStream</code> and connected
050 * <code>PipedOutputStream</code>
051 * be part of different threads. If they are not, the read and write
052 * operations could deadlock their thread.
053 *
054 * @specnote The JDK implementation appears to have some undocumented
055 * functionality where it keeps track of what thread is writing
056 * to pipe and throws an IOException if that thread susequently
057 * dies. This behaviour seems dubious and unreliable - we don't
058 * implement it.
059 *
060 * @author Aaron M. Renn (arenn@urbanophile.com)
061 */
062 public class PipedInputStream extends InputStream
063 {
064 /** PipedOutputStream to which this is connected. Null only if this
065 * InputStream hasn't been connected yet. */
066 PipedOutputStream source;
067
068 /** Set to true if close() has been called on this InputStream. */
069 boolean closed;
070
071
072 /**
073 * The size of the internal buffer used for input/output.
074 */
075 /* The "Constant Field Values" Javadoc of the Sun J2SE 1.4
076 * specifies 1024.
077 */
078 protected static final int PIPE_SIZE = 1024;
079
080
081 /**
082 * This is the internal circular buffer used for storing bytes written
083 * to the pipe and from which bytes are read by this stream
084 */
085 protected byte[] buffer = null;
086
087 /**
088 * The index into buffer where the next byte from the connected
089 * <code>PipedOutputStream</code> will be written. If this variable is
090 * equal to <code>out</code>, then the buffer is full. If set to < 0,
091 * the buffer is empty.
092 */
093 protected int in = -1;
094
095 /**
096 * This index into the buffer where bytes will be read from.
097 */
098 protected int out = 0;
099
100 /** Buffer used to implement single-argument read/receive */
101 private byte[] read_buf = new byte[1];
102
103 /**
104 * Creates a new <code>PipedInputStream</code> that is not connected to a
105 * <code>PipedOutputStream</code>. It must be connected before bytes can
106 * be read from this stream.
107 */
108 public PipedInputStream()
109 {
110 this(PIPE_SIZE);
111 }
112
113 /**
114 * Creates a new <code>PipedInputStream</code> of the given size that is not
115 * connected to a <code>PipedOutputStream</code>.
116 * It must be connected before bytes can be read from this stream.
117 *
118 * @since 1.6
119 * @since IllegalArgumentException If pipeSize <= 0.
120 */
121 public PipedInputStream(int pipeSize) throws IllegalArgumentException
122 {
123 if (pipeSize <= 0)
124 throw new IllegalArgumentException("pipeSize must be > 0");
125
126 this.buffer = new byte[pipeSize];
127 }
128
129 /**
130 * This constructor creates a new <code>PipedInputStream</code> and connects
131 * it to the passed in <code>PipedOutputStream</code>. The stream is then
132 * ready for reading.
133 *
134 * @param source The <code>PipedOutputStream</code> to connect this
135 * stream to
136 *
137 * @exception IOException If <code>source</code> is already connected.
138 */
139 public PipedInputStream(PipedOutputStream source) throws IOException
140 {
141 this();
142 connect(source);
143 }
144
145 /**
146 * This constructor creates a new <code>PipedInputStream</code> of the given
147 * size and connects it to the passed in <code>PipedOutputStream</code>.
148 * The stream is then ready for reading.
149 *
150 * @param source The <code>PipedOutputStream</code> to connect this
151 * stream to
152 *
153 * @since 1.6
154 * @exception IOException If <code>source</code> is already connected.
155 */
156 public PipedInputStream(PipedOutputStream source, int pipeSize)
157 throws IOException
158 {
159 this(pipeSize);
160 connect(source);
161 }
162
163 /**
164 * This method connects this stream to the passed in
165 * <code>PipedOutputStream</code>.
166 * This stream is then ready for reading. If this stream is already
167 * connected or has been previously closed, then an exception is thrown
168 *
169 * @param source The <code>PipedOutputStream</code> to connect this stream to
170 *
171 * @exception IOException If this PipedInputStream or <code>source</code>
172 * has been connected already.
173 */
174 public void connect(PipedOutputStream source) throws IOException
175 {
176 // The JDK (1.3) does not appear to check for a previously closed
177 // connection here.
178
179 if (this.source != null || source.sink != null)
180 throw new IOException ("Already connected");
181
182 source.sink = this;
183 this.source = source;
184 }
185
186 /**
187 * This method receives a byte of input from the source PipedOutputStream.
188 * If the internal circular buffer is full, this method blocks.
189 *
190 * @param val The byte to write to this stream
191 *
192 * @exception IOException if error occurs
193 * @specnote Weird. This method must be some sort of accident.
194 */
195 protected synchronized void receive(int val) throws IOException
196 {
197 read_buf[0] = (byte) (val & 0xff);
198 receive (read_buf, 0, 1);
199 }
200
201 /**
202 * This method is used by the connected <code>PipedOutputStream</code> to
203 * write bytes into the buffer.
204 *
205 * @param buf The array containing bytes to write to this stream
206 * @param offset The offset into the array to start writing from
207 * @param len The number of bytes to write.
208 *
209 * @exception IOException If an error occurs
210 * @specnote This code should be in PipedOutputStream.write, but we
211 * put it here in order to support that bizarre recieve(int)
212 * method.
213 */
214 synchronized void receive(byte[] buf, int offset, int len)
215 throws IOException
216 {
217 if (closed)
218 throw new IOException ("Pipe closed");
219
220 int bufpos = offset;
221 int copylen;
222
223 while (len > 0)
224 {
225 try
226 {
227 while (in == out)
228 {
229 // The pipe is full. Wake up any readers and wait for them.
230 notifyAll();
231 wait();
232 // The pipe could have been closed while we were waiting.
233 if (closed)
234 throw new IOException ("Pipe closed");
235 }
236 }
237 catch (InterruptedException ix)
238 {
239 throw new InterruptedIOException ();
240 }
241
242 if (in < 0) // The pipe is empty.
243 in = 0;
244
245 // Figure out how many bytes from buf can be copied without
246 // overrunning out or going past the length of the buffer.
247 if (in < out)
248 copylen = Math.min (len, out - in);
249 else
250 copylen = Math.min (len, buffer.length - in);
251
252 // Copy bytes until the pipe is filled, wrapping if necessary.
253 System.arraycopy(buf, bufpos, buffer, in, copylen);
254 len -= copylen;
255 bufpos += copylen;
256 in += copylen;
257 if (in == buffer.length)
258 in = 0;
259 }
260 // Notify readers that new data is in the pipe.
261 notifyAll();
262 }
263
264 /**
265 * This method reads one byte from the stream.
266 * -1 is returned to indicated that no bytes can be read
267 * because the end of the stream was reached. If the stream is already
268 * closed, a -1 will again be returned to indicate the end of the stream.
269 *
270 * <p>This method will block if no byte is available to be read.</p>
271 *
272 * @return the value of the read byte value, or -1 of the end of the stream
273 * was reached
274 *
275 * @throws IOException if an error occured
276 */
277 public int read() throws IOException
278 {
279 // Method operates by calling the multibyte overloaded read method
280 // Note that read_buf is an internal instance variable. I allocate it
281 // there to avoid constant reallocation overhead for applications that
282 // call this method in a loop at the cost of some unneeded overhead
283 // if this method is never called.
284
285 int r = read(read_buf, 0, 1);
286 return r != -1 ? (read_buf[0] & 0xff) : -1;
287 }
288
289 /**
290 * This method reads bytes from the stream into a caller supplied buffer.
291 * It starts storing bytes at position <code>offset</code> into the
292 * buffer and
293 * reads a maximum of <code>len</code> bytes. Note that this method
294 * can actually
295 * read fewer than <code>len</code> bytes. The actual number of bytes
296 * read is
297 * returned. A -1 is returned to indicated that no bytes can be read
298 * because the end of the stream was reached - ie close() was called on the
299 * connected PipedOutputStream.
300 * <p>
301 * This method will block if no bytes are available to be read.
302 *
303 * @param buf The buffer into which bytes will be stored
304 * @param offset The index into the buffer at which to start writing.
305 * @param len The maximum number of bytes to read.
306 *
307 * @exception IOException If <code>close()</code> was called on this Piped
308 * InputStream.
309 */
310 public synchronized int read(byte[] buf, int offset, int len)
311 throws IOException
312 {
313 if (source == null)
314 throw new IOException ("Not connected");
315 if (closed)
316 throw new IOException ("Pipe closed");
317
318 // Don't block if nothing was requested.
319 if (len == 0)
320 return 0;
321
322 // If the buffer is empty, wait until there is something in the pipe
323 // to read.
324 try
325 {
326 while (in < 0)
327 {
328 if (source.closed)
329 return -1;
330 wait();
331 }
332 }
333 catch (InterruptedException ix)
334 {
335 throw new InterruptedIOException();
336 }
337
338 int total = 0;
339 int copylen;
340
341 while (true)
342 {
343 // Figure out how many bytes from the pipe can be copied without
344 // overrunning in or going past the length of buf.
345 if (out < in)
346 copylen = Math.min (len, in - out);
347 else
348 copylen = Math.min (len, buffer.length - out);
349
350 System.arraycopy (buffer, out, buf, offset, copylen);
351 offset += copylen;
352 len -= copylen;
353 out += copylen;
354 total += copylen;
355
356 if (out == buffer.length)
357 out = 0;
358
359 if (out == in)
360 {
361 // Pipe is now empty.
362 in = -1;
363 out = 0;
364 }
365
366 // If output buffer is filled or the pipe is empty, we're done.
367 if (len == 0 || in == -1)
368 {
369 // Notify any waiting outputstream that there is now space
370 // to write.
371 notifyAll();
372 return total;
373 }
374 }
375 }
376
377 /**
378 * This method returns the number of bytes that can be read from this stream
379 * before blocking could occur. This is the number of bytes that are
380 * currently unread in the internal circular buffer. Note that once this
381 * many additional bytes are read, the stream may block on a subsequent
382 * read, but it not guaranteed to block.
383 *
384 * @return The number of bytes that can be read before blocking might occur
385 *
386 * @exception IOException If an error occurs
387 */
388 public synchronized int available() throws IOException
389 {
390 // The JDK 1.3 implementation does not appear to check for the closed or
391 // unconnected stream conditions here.
392
393 if (in < 0)
394 return 0;
395 else if (out < in)
396 return in - out;
397 else
398 return (buffer.length - out) + in;
399 }
400
401 /**
402 * This methods closes the stream so that no more data can be read
403 * from it.
404 *
405 * @exception IOException If an error occurs
406 */
407 public synchronized void close() throws IOException
408 {
409 closed = true;
410 // Wake any thread which may be in receive() waiting to write data.
411 notifyAll();
412 }
413 }