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 }
|