001/* PipedOutputStream.java -- Write portion of piped 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 PipedWriter.  If you 
042// fix a bug in here, chances are you should make a similar change to the 
043// PipedWriter code.
044
045/**
046  * This class writes its bytes to a <code>PipedInputStream</code> to 
047  * which it is connected.
048  * <p>
049  * It is highly recommended that a <code>PipedOutputStream</code> and its
050  * connected <code>PipedInputStream</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 PipedOutputStream extends OutputStream
057{
058  /** Target PipedInputStream to which this is connected. Null only if this 
059    * OutputStream hasn't been connected yet. */
060  PipedInputStream sink;
061  
062  /** Set to true if close() has been called on this OutputStream. */
063  boolean closed;
064  
065  /** 
066    * Create an unconnected PipedOutputStream.  It must be connected
067    * to a <code>PipedInputStream</code> using the <code>connect</code>
068    * method prior to writing any data or an exception will be thrown.
069    */
070  public PipedOutputStream()
071  {
072  }
073
074  /**
075     * Create a new <code>PipedOutputStream</code> instance
076    * to write to the specified <code>PipedInputStream</code>.  This stream
077    * is then ready for writing.
078    *
079    * @param sink The <code>PipedInputStream</code> to connect this stream to.
080    *
081    * @exception IOException If <code>sink</code> has already been connected 
082    *                        to a different PipedOutputStream.
083    */
084  public PipedOutputStream(PipedInputStream sink) throws IOException
085  {
086    sink.connect(this);
087  }
088
089  /**
090    * Connects this object to the specified <code>PipedInputStream</code> 
091    * object.  This stream will then be ready for writing.
092    *
093    * @param sink The <code>PipedInputStream</code> to connect this stream to
094    *
095    * @exception IOException If the stream has not been connected or has
096    *                        been closed.
097    */
098  public void connect(PipedInputStream sink) throws IOException
099  {
100    if (this.sink != null || sink.source != null)
101      throw new IOException ("Already connected");
102    sink.connect(this);
103  }
104
105  /**
106    * Write a single byte of date to the stream.  Note that this method will 
107    * block if the <code>PipedInputStream</code> to which this object is 
108    * connected has a full buffer.
109    *
110    * @param b The byte of data to be written, passed as an <code>int</code>.
111    *
112    * @exception IOException If the stream has not been connected or has
113    *                        been closed.
114    */  
115  public void write(int b) throws IOException
116  {
117    if (sink == null)
118      throw new IOException ("Not connected");
119    if (closed)
120      throw new IOException ("Pipe closed");
121      
122    sink.receive (b);
123  }
124  
125  /**
126    * This method writes <code>len</code> bytes of data from the byte array
127    * <code>buf</code> starting at index <code>offset</code> in the array
128    * to the stream.  Note that this method will block if the  
129    * <code>PipedInputStream</code> to which this object is connected has
130    * a buffer that cannot hold all of the bytes to be written.
131    *
132    * @param buffer The array containing bytes to write to the stream.
133    * @param offset The index into the array to start writing bytes from.
134    * @param len The number of bytes to write.
135    *
136    * @exception IOException If the stream has not been connected or has
137    *                        been closed.
138    */
139  public void write(byte[] buffer, int offset, int len) throws IOException
140  {
141    if (sink == null)
142      throw new IOException ("Not connected");
143    if (closed)
144      throw new IOException ("Pipe closed");
145      
146    sink.receive(buffer, offset, len);
147  }
148
149  /**
150    * This method does nothing.
151    *
152    * @exception IOException If the stream is closed.
153    * @specnote You'd think that this method would block until the sink
154    *           had read all available data. Thats not the case - this method
155    *           appears to be a no-op?
156    */
157  public void flush() throws IOException
158  {
159  }
160  
161  /**
162    * This method closes this stream so that no more data can be written
163    * to it. Any further attempts to write to this stream may throw an
164    * exception
165    *
166    * @exception IOException If an error occurs
167    */
168  public void close() throws IOException
169  {
170    // A close call on an unconnected PipedOutputStream has no effect.
171    if (sink != null)
172      {
173        closed = true;
174        // Notify any waiting readers that the stream is now closed.
175        synchronized (sink)
176        {         
177          sink.notifyAll();
178        }
179      }
180  }
181}