1 /*
2 * Copyright (c) 1995, 2006, 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 import java.io.*;
29
30 /**
31 * A piped output stream can be connected to a piped input stream
32 * to create a communications pipe. The piped output stream is the
33 * sending end of the pipe. Typically, data is written to a
34 * <code>PipedOutputStream</code> object by one thread and data is
35 * read from the connected <code>PipedInputStream</code> by some
36 * other thread. Attempting to use both objects from a single thread
37 * is not recommended as it may deadlock the thread.
38 * The pipe is said to be <a id=BROKEN> <i>broken</i> </a> if a
39 * thread that was reading data bytes from the connected piped input
40 * stream is no longer alive.
41 *
42 * @author James Gosling
43 * @see java.io.PipedInputStream
44 * @since 1.0
45 */
46 public
47 class PipedOutputStream extends OutputStream {
48
49 /* REMIND: identification of the read and write sides needs to be
50 more sophisticated. Either using thread groups (but what about
51 pipes within a thread?) or using finalization (but it may be a
52 long time until the next GC). */
53 private PipedInputStream sink;
54
55 /**
56 * Creates a piped output stream connected to the specified piped
57 * input stream. Data bytes written to this stream will then be
58 * available as input from <code>snk</code>.
59 *
60 * @param snk The piped input stream to connect to.
61 * @exception IOException if an I/O error occurs.
62 */
63 public PipedOutputStream(PipedInputStream snk) throws IOException {
64 connect(snk);
65 }
66
67 /**
68 * Creates a piped output stream that is not yet connected to a
69 * piped input stream. It must be connected to a piped input stream,
70 * either by the receiver or the sender, before being used.
71 *
72 * @see java.io.PipedInputStream#connect(java.io.PipedOutputStream)
73 * @see java.io.PipedOutputStream#connect(java.io.PipedInputStream)
74 */
75 public PipedOutputStream() {
76 }
77
78 /**
79 * Connects this piped output stream to a receiver. If this object
80 * is already connected to some other piped input stream, an
81 * <code>IOException</code> is thrown.
82 * <p>
83 * If <code>snk</code> is an unconnected piped input stream and
84 * <code>src</code> is an unconnected piped output stream, they may
85 * be connected by either the call:
86 * <blockquote><pre>
87 * src.connect(snk)</pre></blockquote>
88 * or the call:
89 * <blockquote><pre>
90 * snk.connect(src)</pre></blockquote>
91 * The two calls have the same effect.
92 *
93 * @param snk the piped input stream to connect to.
94 * @exception IOException if an I/O error occurs.
95 */
96 public synchronized void connect(PipedInputStream snk) throws IOException {
97 if (snk == null) {
98 throw new NullPointerException();
99 } else if (sink != null || snk.connected) {
100 throw new IOException("Already connected");
101 }
102 sink = snk;
103 snk.in = -1;
104 snk.out = 0;
105 snk.connected = true;
106 }
107
108 /**
109 * Writes the specified <code>byte</code> to the piped output stream.
110 * <p>
111 * Implements the <code>write</code> method of <code>OutputStream</code>.
112 *
113 * @param b the <code>byte</code> to be written.
114 * @exception IOException if the pipe is <a href=#BROKEN> broken</a>,
115 * {@link #connect(java.io.PipedInputStream) unconnected},
116 * closed, or if an I/O error occurs.
117 */
118 public void write(int b) throws IOException {
119 if (sink == null) {
120 throw new IOException("Pipe not connected");
121 }
122 sink.receive(b);
123 }
124
125 /**
126 * Writes <code>len</code> bytes from the specified byte array
127 * starting at offset <code>off</code> to this piped output stream.
128 * This method blocks until all the bytes are written to the output
129 * stream.
130 *
131 * @param b the data.
132 * @param off the start offset in the data.
133 * @param len the number of bytes to write.
134 * @exception IOException if the pipe is <a href=#BROKEN> broken</a>,
135 * {@link #connect(java.io.PipedInputStream) unconnected},
136 * closed, or if an I/O error occurs.
137 */
138 public void write(byte[] b, int off, int len) throws IOException {
139 if (sink == null) {
140 throw new IOException("Pipe not connected");
141 } else if (b == null) {
142 throw new NullPointerException();
143 } else if ((off < 0) || (off > b.length) || (len < 0) ||
144 ((off + len) > b.length) || ((off + len) < 0)) {
145 throw new IndexOutOfBoundsException();
146 } else if (len == 0) {
147 return;
148 }
149 sink.receive(b, off, len);
150 }
151
152 /**
153 * Flushes this output stream and forces any buffered output bytes
154 * to be written out.
155 * This will notify any readers that bytes are waiting in the pipe.
156 *
157 * @exception IOException if an I/O error occurs.
158 */
159 public synchronized void flush() throws IOException {
160 if (sink != null) {
161 synchronized (sink) {
162 sink.notifyAll();
163 }
164 }
165 }
166
167 /**
168 * Closes this piped output stream and releases any system resources
169 * associated with this stream. This stream may no longer be used for
170 * writing bytes.
171 *
172 * @exception IOException if an I/O error occurs.
173 */
174 public void close() throws IOException {
175 if (sink != null) {
176 sink.receivedLast();
177 }
178 }
179 }