001    /* PipedOutputStream.java -- Write portion of piped 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 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      */
056    public 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    }