libjava/java/io/PipedOutputStream.java

   1 /* PipedOutputStream.java -- Write portion of piped streams.
   2    Copyright (C) 1998, 2000, 2001, 2003 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package java.io;
  40
  41 // NOTE: This implementation is very similar to that of PipedWriter.  If you
  42 // fix a bug in here, chances are you should make a similar change to the
  43 // PipedWriter code.
  44
  45 /**
  46   * This class writes its bytes to a <code>PipedInputStream</code> to
  47   * which it is connected.
  48   * <p>
  49   * It is highly recommended that a <code>PipedOutputStream</code> and its
  50   * connected <code>PipedInputStream</code> be in different threads.  If
  51   * they are in the same thread, read and write operations could deadlock
  52   * the thread.
  53   *
  54   * @author Aaron M. Renn (arenn@urbanophile.com)
  55   */
  56 public class PipedOutputStream extends OutputStream
  57 {
  58   /** Target PipedInputStream to which this is connected. Null only if this
  59     * OutputStream hasn't been connected yet. */
  60   PipedInputStream sink;
  61
  62   /** Set to true if close() has been called on this OutputStream. */
  63   boolean closed;
  64
  65   /**
  66     * Create an unconnected PipedOutputStream.  It must be connected
  67     * to a <code>PipedInputStream</code> using the <code>connect</code>
  68     * method prior to writing any data or an exception will be thrown.
  69     */
  70   public PipedOutputStream()
  71   {
  72   }
  73
  74   /**
  75      * Create a new <code>PipedOutputStream</code> instance
  76     * to write to the specified <code>PipedInputStream</code>.  This stream
  77     * is then ready for writing.
  78     *
  79     * @param sink The <code>PipedInputStream</code> to connect this stream to.
  80     *
  81     * @exception IOException If <code>sink</code> has already been connected
  82     *                        to a different PipedOutputStream.
  83     */
  84   public PipedOutputStream(PipedInputStream sink) throws IOException
  85   {
  86     sink.connect(this);
  87   }
  88
  89   /**
  90     * Connects this object to the specified <code>PipedInputStream</code>
  91     * object.  This stream will then be ready for writing.
  92     *
  93     * @param sink The <code>PipedInputStream</code> to connect this stream to
  94     *
  95     * @exception IOException If the stream has not been connected or has
  96     *                        been closed.
  97     */
  98   public void connect(PipedInputStream sink) throws IOException
  99   {
 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 }