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: import java.io.*;
029:
030: /**
031: * A piped output stream can be connected to a piped input stream
032: * to create a communications pipe. The piped output stream is the
033: * sending end of the pipe. Typically, data is written to a
034: * <code>PipedOutputStream</code> object by one thread and data is
035: * read from the connected <code>PipedInputStream</code> by some
036: * other thread. Attempting to use both objects from a single thread
037: * is not recommended as it may deadlock the thread.
038: * The pipe is said to be <a name=BROKEN> <i>broken</i> </a> if a
039: * thread that was reading data bytes from the connected piped input
040: * stream is no longer alive.
041: *
042: * @author James Gosling
043: * @version 1.34, 05/05/07
044: * @see java.io.PipedInputStream
045: * @since JDK1.0
046: */
047: public class PipedOutputStream extends OutputStream {
048:
049: /* REMIND: identification of the read and write sides needs to be
050: more sophisticated. Either using thread groups (but what about
051: pipes within a thread?) or using finalization (but it may be a
052: long time until the next GC). */
053: private PipedInputStream sink;
054:
055: /**
056: * Creates a piped output stream connected to the specified piped
057: * input stream. Data bytes written to this stream will then be
058: * available as input from <code>snk</code>.
059: *
060: * @param snk The piped input stream to connect to.
061: * @exception IOException if an I/O error occurs.
062: */
063: public PipedOutputStream(PipedInputStream snk) throws IOException {
064: connect(snk);
065: }
066:
067: /**
068: * Creates a piped output stream that is not yet connected to a
069: * piped input stream. It must be connected to a piped input stream,
070: * either by the receiver or the sender, before being used.
071: *
072: * @see java.io.PipedInputStream#connect(java.io.PipedOutputStream)
073: * @see java.io.PipedOutputStream#connect(java.io.PipedInputStream)
074: */
075: public PipedOutputStream() {
076: }
077:
078: /**
079: * Connects this piped output stream to a receiver. If this object
080: * is already connected to some other piped input stream, an
081: * <code>IOException</code> is thrown.
082: * <p>
083: * If <code>snk</code> is an unconnected piped input stream and
084: * <code>src</code> is an unconnected piped output stream, they may
085: * be connected by either the call:
086: * <blockquote><pre>
087: * src.connect(snk)</pre></blockquote>
088: * or the call:
089: * <blockquote><pre>
090: * snk.connect(src)</pre></blockquote>
091: * The two calls have the same effect.
092: *
093: * @param snk the piped input stream to connect to.
094: * @exception IOException if an I/O error occurs.
095: */
096: public synchronized void connect(PipedInputStream snk)
097: throws IOException {
098: if (snk == null) {
099: throw new NullPointerException();
100: } else if (sink != null || snk.connected) {
101: throw new IOException("Already connected");
102: }
103: sink = snk;
104: snk.in = -1;
105: snk.out = 0;
106: snk.connected = true;
107: }
108:
109: /**
110: * Writes the specified <code>byte</code> to the piped output stream.
111: * <p>
112: * Implements the <code>write</code> method of <code>OutputStream</code>.
113: *
114: * @param b the <code>byte</code> to be written.
115: * @exception IOException if the pipe is <a href=#BROKEN> broken</a>,
116: * {@link #connect(java.io.PipedInputStream) unconnected},
117: * closed, or if an I/O error occurs.
118: */
119: public void write(int b) throws IOException {
120: if (sink == null) {
121: throw new IOException("Pipe not connected");
122: }
123: sink.receive(b);
124: }
125:
126: /**
127: * Writes <code>len</code> bytes from the specified byte array
128: * starting at offset <code>off</code> to this piped output stream.
129: * This method blocks until all the bytes are written to the output
130: * stream.
131: *
132: * @param b the data.
133: * @param off the start offset in the data.
134: * @param len the number of bytes to write.
135: * @exception IOException if the pipe is <a href=#BROKEN> broken</a>,
136: * {@link #connect(java.io.PipedInputStream) unconnected},
137: * closed, or if an I/O error occurs.
138: */
139: public void write(byte b[], int off, int len) throws IOException {
140: if (sink == null) {
141: throw new IOException("Pipe not connected");
142: } else if (b == null) {
143: throw new NullPointerException();
144: } else if ((off < 0) || (off > b.length) || (len < 0)
145: || ((off + len) > b.length) || ((off + len) < 0)) {
146: throw new IndexOutOfBoundsException();
147: } else if (len == 0) {
148: return;
149: }
150: sink.receive(b, off, len);
151: }
152:
153: /**
154: * Flushes this output stream and forces any buffered output bytes
155: * to be written out.
156: * This will notify any readers that bytes are waiting in the pipe.
157: *
158: * @exception IOException if an I/O error occurs.
159: */
160: public synchronized void flush() throws IOException {
161: if (sink != null) {
162: synchronized (sink) {
163: sink.notifyAll();
164: }
165: }
166: }
167:
168: /**
169: * Closes this piped output stream and releases any system resources
170: * associated with this stream. This stream may no longer be used for
171: * writing bytes.
172: *
173: * @exception IOException if an I/O error occurs.
174: */
175: public void close() throws IOException {
176: if (sink != null) {
177: sink.receivedLast();
178: }
179: }
180: }
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