1/*
2 * Copyright (c) 1996, 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
26package java.io;
27
28
29/**
30 * Piped character-output streams.
31 *
32 * @author      Mark Reinhold
33 * @since       JDK1.1
34 */
35
36public class PipedWriter extends Writer {
37
38    /* REMIND: identification of the read and write sides needs to be
39       more sophisticated.  Either using thread groups (but what about
40       pipes within a thread?) or using finalization (but it may be a
41       long time until the next GC). */
42    private PipedReader sink;
43
44    /* This flag records the open status of this particular writer. It
45     * is independent of the status flags defined in PipedReader. It is
46     * used to do a sanity check on connect.
47     */
48    private boolean closed = false;
49
50    /**
51     * Creates a piped writer connected to the specified piped
52     * reader. Data characters written to this stream will then be
53     * available as input from <code>snk</code>.
54     *
55     * @param      snk   The piped reader to connect to.
56     * @exception  IOException  if an I/O error occurs.
57     */
58    public PipedWriter(PipedReader snk)  throws IOException {
59        connect(snk);
60    }
61
62    /**
63     * Creates a piped writer that is not yet connected to a
64     * piped reader. It must be connected to a piped reader,
65     * either by the receiver or the sender, before being used.
66     *
67     * @see     java.io.PipedReader#connect(java.io.PipedWriter)
68     * @see     java.io.PipedWriter#connect(java.io.PipedReader)
69     */
70    public PipedWriter() {
71    }
72
73    /**
74     * Connects this piped writer to a receiver. If this object
75     * is already connected to some other piped reader, an
76     * <code>IOException</code> is thrown.
77     * <p>
78     * If <code>snk</code> is an unconnected piped reader and
79     * <code>src</code> is an unconnected piped writer, they may
80     * be connected by either the call:
81     * <blockquote><pre>
82     * src.connect(snk)</pre></blockquote>
83     * or the call:
84     * <blockquote><pre>
85     * snk.connect(src)</pre></blockquote>
86     * The two calls have the same effect.
87     *
88     * @param      snk   the piped reader to connect to.
89     * @exception  IOException  if an I/O error occurs.
90     */
91    public synchronized void connect(PipedReader snk) throws IOException {
92        if (snk == null) {
93            throw new NullPointerException();
94        } else if (sink != null || snk.connected) {
95            throw new IOException("Already connected");
96        } else if (snk.closedByReader || closed) {
97            throw new IOException("Pipe closed");
98        }
99
100        sink = snk;
101        snk.in = -1;
102        snk.out = 0;
103        snk.connected = true;
104    }
105
106    /**
107     * Writes the specified <code>char</code> to the piped output stream.
108     * If a thread was reading data characters from the connected piped input
109     * stream, but the thread is no longer alive, then an
110     * <code>IOException</code> is thrown.
111     * <p>
112     * Implements the <code>write</code> method of <code>Writer</code>.
113     *
114     * @param      c   the <code>char</code> to be written.
115     * @exception  IOException  if the pipe is
116     *          <a href=PipedOutputStream.html#BROKEN> <code>broken</code></a>,
117     *          {@link #connect(java.io.PipedReader) unconnected}, closed
118     *          or an I/O error occurs.
119     */
120    public void write(int c)  throws IOException {
121        if (sink == null) {
122            throw new IOException("Pipe not connected");
123        }
124        sink.receive(c);
125    }
126
127    /**
128     * Writes <code>len</code> characters from the specified character array
129     * starting at offset <code>off</code> to this piped output stream.
130     * This method blocks until all the characters are written to the output
131     * stream.
132     * If a thread was reading data characters from the connected piped input
133     * stream, but the thread is no longer alive, then an
134     * <code>IOException</code> is thrown.
135     *
136     * @param      cbuf  the data.
137     * @param      off   the start offset in the data.
138     * @param      len   the number of characters to write.
139     * @exception  IOException  if the pipe is
140     *          <a href=PipedOutputStream.html#BROKEN> <code>broken</code></a>,
141     *          {@link #connect(java.io.PipedReader) unconnected}, closed
142     *          or an I/O error occurs.
143     */
144    public void write(char cbuf[], int off, int len) throws IOException {
145        if (sink == null) {
146            throw new IOException("Pipe not connected");
147        } else if ((off | len | (off + len) | (cbuf.length - (off + len))) < 0) {
148            throw new IndexOutOfBoundsException();
149        }
150        sink.receive(cbuf, off, len);
151    }
152
153    /**
154     * Flushes this output stream and forces any buffered output characters
155     * to be written out.
156     * This will notify any readers that characters are waiting in the pipe.
157     *
158     * @exception  IOException  if the pipe is closed, or an I/O error occurs.
159     */
160    public synchronized void flush() throws IOException {
161        if (sink != null) {
162            if (sink.closedByReader || closed) {
163                throw new IOException("Pipe closed");
164            }
165            synchronized (sink) {
166                sink.notifyAll();
167            }
168        }
169    }
170
171    /**
172     * Closes this piped output stream and releases any system resources
173     * associated with this stream. This stream may no longer be used for
174     * writing characters.
175     *
176     * @exception  IOException  if an I/O error occurs.
177     */
178    public void close()  throws IOException {
179        closed = true;
180        if (sink != null) {
181            sink.receivedLast();
182        }
183    }
184}
185