Source for java.io.PipedOutputStream

   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., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 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: }