001: /*
002: * Copyright 1995-2006 Sun Microsystems, Inc. All Rights Reserved.
003: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004: *
005: * This code is free software; you can redistribute it and/or modify it
006: * under the terms of the GNU General Public License version 2 only, as
007: * published by the Free Software Foundation. Sun designates this
008: * particular file as subject to the "Classpath" exception as provided
009: * by Sun in the LICENSE file that accompanied this code.
010: *
011: * This code is distributed in the hope that it will be useful, but WITHOUT
012: * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013: * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014: * version 2 for more details (a copy is included in the LICENSE file that
015: * accompanied this code).
016: *
017: * You should have received a copy of the GNU General Public License version
018: * 2 along with this work; if not, write to the Free Software Foundation,
019: * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020: *
021: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022: * CA 95054 USA or visit www.sun.com if you need additional information or
023: * have any questions.
024: */
025:
026: package java.io;
027:
028: /**
029: * A piped input stream should be connected
030: * to a piped output stream; the piped input
031: * stream then provides whatever data bytes
032: * are written to the piped output stream.
033: * Typically, data is read from a <code>PipedInputStream</code>
034: * object by one thread and data is written
035: * to the corresponding <code>PipedOutputStream</code>
036: * by some other thread. Attempting to use
037: * both objects from a single thread is not
038: * recommended, as it may deadlock the thread.
039: * The piped input stream contains a buffer,
040: * decoupling read operations from write operations,
041: * within limits.
042: * A pipe is said to be <a name=BROKEN> <i>broken</i> </a> if a
043: * thread that was providing data bytes to the connected
044: * piped output stream is no longer alive.
045: *
046: * @author James Gosling
047: * @version 1.40, 12/01/05
048: * @see java.io.PipedOutputStream
049: * @since JDK1.0
050: */
051: public class PipedInputStream extends InputStream {
052: boolean closedByWriter = false;
053: volatile boolean closedByReader = false;
054: boolean connected = false;
055:
056: /* REMIND: identification of the read and write sides needs to be
057: more sophisticated. Either using thread groups (but what about
058: pipes within a thread?) or using finalization (but it may be a
059: long time until the next GC). */
060: Thread readSide;
061: Thread writeSide;
062:
063: private static final int DEFAULT_PIPE_SIZE = 1024;
064:
065: /**
066: * The default size of the pipe's circular input buffer.
067: * @since JDK1.1
068: */
069: // This used to be a constant before the pipe size was allowed
070: // to change. This field will continue to be maintained
071: // for backward compatibility.
072: protected static final int PIPE_SIZE = DEFAULT_PIPE_SIZE;
073:
074: /**
075: * The circular buffer into which incoming data is placed.
076: * @since JDK1.1
077: */
078: protected byte buffer[];
079:
080: /**
081: * The index of the position in the circular buffer at which the
082: * next byte of data will be stored when received from the connected
083: * piped output stream. <code>in<0</code> implies the buffer is empty,
084: * <code>in==out</code> implies the buffer is full
085: * @since JDK1.1
086: */
087: protected int in = -1;
088:
089: /**
090: * The index of the position in the circular buffer at which the next
091: * byte of data will be read by this piped input stream.
092: * @since JDK1.1
093: */
094: protected int out = 0;
095:
096: /**
097: * Creates a <code>PipedInputStream</code> so
098: * that it is connected to the piped output
099: * stream <code>src</code>. Data bytes written
100: * to <code>src</code> will then be available
101: * as input from this stream.
102: *
103: * @param src the stream to connect to.
104: * @exception IOException if an I/O error occurs.
105: */
106: public PipedInputStream(PipedOutputStream src) throws IOException {
107: this (src, DEFAULT_PIPE_SIZE);
108: }
109:
110: /**
111: * Creates a <code>PipedInputStream</code> so that it is
112: * connected to the piped output stream
113: * <code>src</code> and uses the specified pipe size for
114: * the pipe's buffer.
115: * Data bytes written to <code>src</code> will then
116: * be available as input from this stream.
117: *
118: * @param src the stream to connect to.
119: * @param pipeSize the size of the pipe's buffer.
120: * @exception IOException if an I/O error occurs.
121: * @exception IllegalArgumentException if <code>pipeSize <= 0</code>.
122: * @since 1.6
123: */
124: public PipedInputStream(PipedOutputStream src, int pipeSize)
125: throws IOException {
126: initPipe(pipeSize);
127: connect(src);
128: }
129:
130: /**
131: * Creates a <code>PipedInputStream</code> so
132: * that it is not yet {@linkplain #connect(java.io.PipedOutputStream)
133: * connected}.
134: * It must be {@linkplain java.io.PipedOutputStream#connect(
135: * java.io.PipedInputStream) connected} to a
136: * <code>PipedOutputStream</code> before being used.
137: */
138: public PipedInputStream() {
139: initPipe(DEFAULT_PIPE_SIZE);
140: }
141:
142: /**
143: * Creates a <code>PipedInputStream</code> so that it is not yet
144: * {@linkplain #connect(java.io.PipedOutputStream) connected} and
145: * uses the specified pipe size for the pipe's buffer.
146: * It must be {@linkplain java.io.PipedOutputStream#connect(
147: * java.io.PipedInputStream)
148: * connected} to a <code>PipedOutputStream</code> before being used.
149: *
150: * @param pipeSize the size of the pipe's buffer.
151: * @exception IllegalArgumentException if <code>pipeSize <= 0</code>.
152: * @since 1.6
153: */
154: public PipedInputStream(int pipeSize) {
155: initPipe(pipeSize);
156: }
157:
158: private void initPipe(int pipeSize) {
159: if (pipeSize <= 0) {
160: throw new IllegalArgumentException("Pipe Size <= 0");
161: }
162: buffer = new byte[pipeSize];
163: }
164:
165: /**
166: * Causes this piped input stream to be connected
167: * to the piped output stream <code>src</code>.
168: * If this object is already connected to some
169: * other piped output stream, an <code>IOException</code>
170: * is thrown.
171: * <p>
172: * If <code>src</code> is an
173: * unconnected piped output stream and <code>snk</code>
174: * is an unconnected piped input stream, they
175: * may be connected by either the call:
176: * <p>
177: * <pre><code>snk.connect(src)</code> </pre>
178: * <p>
179: * or the call:
180: * <p>
181: * <pre><code>src.connect(snk)</code> </pre>
182: * <p>
183: * The two
184: * calls have the same effect.
185: *
186: * @param src The piped output stream to connect to.
187: * @exception IOException if an I/O error occurs.
188: */
189: public void connect(PipedOutputStream src) throws IOException {
190: src.connect(this );
191: }
192:
193: /**
194: * Receives a byte of data. This method will block if no input is
195: * available.
196: * @param b the byte being received
197: * @exception IOException If the pipe is <a href=#BROKEN> <code>broken</code></a>,
198: * {@link #connect(java.io.PipedOutputStream) unconnected},
199: * closed, or if an I/O error occurs.
200: * @since JDK1.1
201: */
202: protected synchronized void receive(int b) throws IOException {
203: checkStateForReceive();
204: writeSide = Thread.currentThread();
205: if (in == out)
206: awaitSpace();
207: if (in < 0) {
208: in = 0;
209: out = 0;
210: }
211: buffer[in++] = (byte) (b & 0xFF);
212: if (in >= buffer.length) {
213: in = 0;
214: }
215: }
216:
217: /**
218: * Receives data into an array of bytes. This method will
219: * block until some input is available.
220: * @param b the buffer into which the data is received
221: * @param off the start offset of the data
222: * @param len the maximum number of bytes received
223: * @exception IOException If the pipe is <a href=#BROKEN> broken</a>,
224: * {@link #connect(java.io.PipedOutputStream) unconnected},
225: * closed,or if an I/O error occurs.
226: */
227: synchronized void receive(byte b[], int off, int len)
228: throws IOException {
229: checkStateForReceive();
230: writeSide = Thread.currentThread();
231: int bytesToTransfer = len;
232: while (bytesToTransfer > 0) {
233: if (in == out)
234: awaitSpace();
235: int nextTransferAmount = 0;
236: if (out < in) {
237: nextTransferAmount = buffer.length - in;
238: } else if (in < out) {
239: if (in == -1) {
240: in = out = 0;
241: nextTransferAmount = buffer.length - in;
242: } else {
243: nextTransferAmount = out - in;
244: }
245: }
246: if (nextTransferAmount > bytesToTransfer)
247: nextTransferAmount = bytesToTransfer;
248: assert (nextTransferAmount > 0);
249: System.arraycopy(b, off, buffer, in, nextTransferAmount);
250: bytesToTransfer -= nextTransferAmount;
251: off += nextTransferAmount;
252: in += nextTransferAmount;
253: if (in >= buffer.length) {
254: in = 0;
255: }
256: }
257: }
258:
259: private void checkStateForReceive() throws IOException {
260: if (!connected) {
261: throw new IOException("Pipe not connected");
262: } else if (closedByWriter || closedByReader) {
263: throw new IOException("Pipe closed");
264: } else if (readSide != null && !readSide.isAlive()) {
265: throw new IOException("Read end dead");
266: }
267: }
268:
269: private void awaitSpace() throws IOException {
270: while (in == out) {
271: checkStateForReceive();
272:
273: /* full: kick any waiting readers */
274: notifyAll();
275: try {
276: wait(1000);
277: } catch (InterruptedException ex) {
278: throw new java.io.InterruptedIOException();
279: }
280: }
281: }
282:
283: /**
284: * Notifies all waiting threads that the last byte of data has been
285: * received.
286: */
287: synchronized void receivedLast() {
288: closedByWriter = true;
289: notifyAll();
290: }
291:
292: /**
293: * Reads the next byte of data from this piped input stream. The
294: * value byte is returned as an <code>int</code> in the range
295: * <code>0</code> to <code>255</code>.
296: * This method blocks until input data is available, the end of the
297: * stream is detected, or an exception is thrown.
298: *
299: * @return the next byte of data, or <code>-1</code> if the end of the
300: * stream is reached.
301: * @exception IOException if the pipe is
302: * {@link #connect(java.io.PipedOutputStream) unconnected},
303: * <a href=#BROKEN> <code>broken</code></a>, closed,
304: * or if an I/O error occurs.
305: */
306: public synchronized int read() throws IOException {
307: if (!connected) {
308: throw new IOException("Pipe not connected");
309: } else if (closedByReader) {
310: throw new IOException("Pipe closed");
311: } else if (writeSide != null && !writeSide.isAlive()
312: && !closedByWriter && (in < 0)) {
313: throw new IOException("Write end dead");
314: }
315:
316: readSide = Thread.currentThread();
317: int trials = 2;
318: while (in < 0) {
319: if (closedByWriter) {
320: /* closed by writer, return EOF */
321: return -1;
322: }
323: if ((writeSide != null) && (!writeSide.isAlive())
324: && (--trials < 0)) {
325: throw new IOException("Pipe broken");
326: }
327: /* might be a writer waiting */
328: notifyAll();
329: try {
330: wait(1000);
331: } catch (InterruptedException ex) {
332: throw new java.io.InterruptedIOException();
333: }
334: }
335: int ret = buffer[out++] & 0xFF;
336: if (out >= buffer.length) {
337: out = 0;
338: }
339: if (in == out) {
340: /* now empty */
341: in = -1;
342: }
343:
344: return ret;
345: }
346:
347: /**
348: * Reads up to <code>len</code> bytes of data from this piped input
349: * stream into an array of bytes. Less than <code>len</code> bytes
350: * will be read if the end of the data stream is reached or if
351: * <code>len</code> exceeds the pipe's buffer size.
352: * If <code>len </code> is zero, then no bytes are read and 0 is returned;
353: * otherwise, the method blocks until at least 1 byte of input is
354: * available, end of the stream has been detected, or an exception is
355: * thrown.
356: *
357: * @param b the buffer into which the data is read.
358: * @param off the start offset in the destination array <code>b</code>
359: * @param len the maximum number of bytes read.
360: * @return the total number of bytes read into the buffer, or
361: * <code>-1</code> if there is no more data because the end of
362: * the stream has been reached.
363: * @exception NullPointerException If <code>b</code> is <code>null</code>.
364: * @exception IndexOutOfBoundsException If <code>off</code> is negative,
365: * <code>len</code> is negative, or <code>len</code> is greater than
366: * <code>b.length - off</code>
367: * @exception IOException if the pipe is <a href=#BROKEN> <code>broken</code></a>,
368: * {@link #connect(java.io.PipedOutputStream) unconnected},
369: * closed, or if an I/O error occurs.
370: */
371: public synchronized int read(byte b[], int off, int len)
372: throws IOException {
373: if (b == null) {
374: throw new NullPointerException();
375: } else if (off < 0 || len < 0 || len > b.length - off) {
376: throw new IndexOutOfBoundsException();
377: } else if (len == 0) {
378: return 0;
379: }
380:
381: /* possibly wait on the first character */
382: int c = read();
383: if (c < 0) {
384: return -1;
385: }
386: b[off] = (byte) c;
387: int rlen = 1;
388: while ((in >= 0) && (len > 1)) {
389:
390: int available;
391:
392: if (in > out) {
393: available = Math.min((buffer.length - out), (in - out));
394: } else {
395: available = buffer.length - out;
396: }
397:
398: // A byte is read beforehand outside the loop
399: if (available > (len - 1)) {
400: available = len - 1;
401: }
402: System.arraycopy(buffer, out, b, off + rlen, available);
403: out += available;
404: rlen += available;
405: len -= available;
406:
407: if (out >= buffer.length) {
408: out = 0;
409: }
410: if (in == out) {
411: /* now empty */
412: in = -1;
413: }
414: }
415: return rlen;
416: }
417:
418: /**
419: * Returns the number of bytes that can be read from this input
420: * stream without blocking.
421: *
422: * @return the number of bytes that can be read from this input stream
423: * without blocking, or {@code 0} if this input stream has been
424: * closed by invoking its {@link #close()} method, or if the pipe
425: * is {@link #connect(java.io.PipedOutputStream) unconnected}, or
426: * <a href=#BROKEN> <code>broken</code></a>.
427: *
428: * @exception IOException if an I/O error occurs.
429: * @since JDK1.0.2
430: */
431: public synchronized int available() throws IOException {
432: if (in < 0)
433: return 0;
434: else if (in == out)
435: return buffer.length;
436: else if (in > out)
437: return in - out;
438: else
439: return in + buffer.length - out;
440: }
441:
442: /**
443: * Closes this piped input stream and releases any system resources
444: * associated with the stream.
445: *
446: * @exception IOException if an I/O error occurs.
447: */
448: public void close() throws IOException {
449: closedByReader = true;
450: synchronized (this ) {
451: in = -1;
452: }
453: }
454: }
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