001/* PipedWriter.java -- Write portion of piped character streams.
002   Copyright (C) 1998, 2000, 2001, 2003 Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010 
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package 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  */
056public 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}