Source for java.io.PipedWriter

   1: /* PipedWriter.java -- Write portion of piped character 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 PipedOutputStream. 
  42: // If you fix a bug in here, chances are you should make a similar change to 
  43: // the PipedOutputStream code.
  44: 
  45: /**
  46:   * This class writes its chars to a <code>PipedReader</code> to 
  47:   * which it is connected.
  48:   * <p>
  49:   * It is highly recommended that a <code>PipedWriter</code> and its
  50:   * connected <code>PipedReader</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 PipedWriter extends Writer
  57: {
  58:   /** Target PipedReader to which this is connected. Null only if this 
  59:     * Writer hasn't been connected yet. */
  60:   PipedReader sink;
  61:   
  62:   /** Set to true if close() has been called on this Writer. */
  63:   boolean closed;
  64: 
  65:   /** Buffer used to implement single-argument write */
  66:   char[] read_buf = new char[1];
  67:   
  68:   /** 
  69:     * Create an unconnected PipedWriter.  It must be connected
  70:     * to a <code>PipedReader</code> using the <code>connect</code>
  71:     * method prior to writing any data or an exception will be thrown.
  72:     */
  73:   public PipedWriter()
  74:   {
  75:   }
  76: 
  77:   /**
  78:      * Create a new <code>PipedWriter</code> instance
  79:     * to write to the specified <code>PipedReader</code>.  This stream
  80:     * is then ready for writing.
  81:     *
  82:     * @param sink The <code>PipedReader</code> to connect this stream to.
  83:     *
  84:     * @exception IOException If <code>sink</code> has already been connected 
  85:     *                        to a different PipedWriter.
  86:     */
  87:   public PipedWriter(PipedReader sink) throws IOException
  88:   {
  89:     sink.connect(this);
  90:   }
  91: 
  92:   /**
  93:     * Connects this object to the specified <code>PipedReader</code> 
  94:     * object.  This stream will then be ready for writing.
  95:     *
  96:     * @param sink The <code>PipedReader</code> to connect this stream to
  97:     *
  98:     * @exception IOException If the stream has not been connected or has
  99:     *                        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: }