001 /* PipedWriter.java -- Write portion of piped character streams.
002 Copyright (C) 1998, 2000, 2001, 2003 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038
039 package java.io;
040
041 // NOTE: This implementation is very similar to that of PipedOutputStream.
042 // If you fix a bug in here, chances are you should make a similar change to
043 // the PipedOutputStream code.
044
045 /**
046 * This class writes its chars to a <code>PipedReader</code> to
047 * which it is connected.
048 * <p>
049 * It is highly recommended that a <code>PipedWriter</code> and its
050 * connected <code>PipedReader</code> be in different threads. If
051 * they are in the same thread, read and write operations could deadlock
052 * the thread.
053 *
054 * @author Aaron M. Renn (arenn@urbanophile.com)
055 */
056 public class PipedWriter extends Writer
057 {
058 /** Target PipedReader to which this is connected. Null only if this
059 * Writer hasn't been connected yet. */
060 PipedReader sink;
061
062 /** Set to true if close() has been called on this Writer. */
063 boolean closed;
064
065 /** Buffer used to implement single-argument write */
066 char[] read_buf = new char[1];
067
068 /**
069 * Create an unconnected PipedWriter. It must be connected
070 * to a <code>PipedReader</code> using the <code>connect</code>
071 * method prior to writing any data or an exception will be thrown.
072 */
073 public PipedWriter()
074 {
075 }
076
077 /**
078 * Create a new <code>PipedWriter</code> instance
079 * to write to the specified <code>PipedReader</code>. This stream
080 * is then ready for writing.
081 *
082 * @param sink The <code>PipedReader</code> to connect this stream to.
083 *
084 * @exception IOException If <code>sink</code> has already been connected
085 * to a different PipedWriter.
086 */
087 public PipedWriter(PipedReader sink) throws IOException
088 {
089 sink.connect(this);
090 }
091
092 /**
093 * Connects this object to the specified <code>PipedReader</code>
094 * object. This stream will then be ready for writing.
095 *
096 * @param sink The <code>PipedReader</code> to connect this stream to
097 *
098 * @exception IOException If the stream has not been connected or has
099 * been closed.
100 */
101 public void connect(PipedReader sink) throws IOException
102 {
103 if (this.sink != null || sink.source != null)
104 throw new IOException ("Already connected");
105 sink.connect(this);
106 }
107
108 /**
109 * Write a single char of date to the stream. Note that this method will
110 * block if the <code>PipedReader</code> to which this object is
111 * connected has a full buffer.
112 *
113 * @param b The char of data to be written, passed as an <code>int</code>.
114 *
115 * @exception IOException If the stream has not been connected or has
116 * been closed.
117 */
118 public void write(int b) throws IOException
119 {
120 read_buf[0] = (char) (b & 0xffff);
121 sink.receive (read_buf, 0, 1);
122 }
123
124 /**
125 * This method writes <code>len</code> chars of data from the char array
126 * <code>buf</code> starting at index <code>offset</code> in the array
127 * to the stream. Note that this method will block if the
128 * <code>PipedReader</code> to which this object is connected has
129 * a buffer that cannot hold all of the chars to be written.
130 *
131 * @param buffer The array containing chars to write to the stream.
132 * @param offset The index into the array to start writing chars from.
133 * @param len The number of chars to write.
134 *
135 * @exception IOException If the stream has not been connected or has
136 * been closed.
137 */
138 public void write(char[] buffer, int offset, int len) throws IOException
139 {
140 if (sink == null)
141 throw new IOException ("Not connected");
142 if (closed)
143 throw new IOException ("Pipe closed");
144
145 sink.receive(buffer, offset, len);
146 }
147
148 /**
149 * This method does nothing.
150 *
151 * @exception IOException If the stream is closed.
152 * @specnote You'd think that this method would block until the sink
153 * had read all available data. Thats not the case - this method
154 * appears to be a no-op?
155 */
156 public void flush() throws IOException
157 {
158 if (closed)
159 throw new IOException ("Pipe closed");
160 }
161
162 /**
163 * This method closes this stream so that no more data can be written
164 * to it. Any further attempts to write to this stream may throw an
165 * exception
166 *
167 * @exception IOException If an error occurs
168 */
169 public void close() throws IOException
170 {
171 // A close call on an unconnected PipedWriter has no effect.
172 if (sink != null)
173 {
174 closed = true;
175 // Notify any waiting readers that the stream is now closed.
176 synchronized (sink)
177 {
178 sink.notifyAll();
179 }
180 }
181 }
182 }