Source for java.io.FileDescriptor

   1: /* FileDescriptor.java -- Opaque file handle class
   2:    Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004
   3:    Free Software Foundation, Inc.
   4: 
   5: This file is part of GNU Classpath.
   6: 
   7: GNU Classpath is free software; you can redistribute it and/or modify
   8: it under the terms of the GNU General Public License as published by
   9: the Free Software Foundation; either version 2, or (at your option)
  10: any later version.
  11:  
  12: GNU Classpath is distributed in the hope that it will be useful, but
  13: WITHOUT ANY WARRANTY; without even the implied warranty of
  14: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15: General Public License for more details.
  16: 
  17: You should have received a copy of the GNU General Public License
  18: along with GNU Classpath; see the file COPYING.  If not, write to the
  19: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  20: 02110-1301 USA.
  21: 
  22: Linking this library statically or dynamically with other modules is
  23: making a combined work based on this library.  Thus, the terms and
  24: conditions of the GNU General Public License cover the whole
  25: combination.
  26: 
  27: As a special exception, the copyright holders of this library give you
  28: permission to link this library with independent modules to produce an
  29: executable, regardless of the license terms of these independent
  30: modules, and to copy and distribute the resulting executable under
  31: terms of your choice, provided that you also meet, for each linked
  32: independent module, the terms and conditions of the license of that
  33: module.  An independent module is a module which is not derived from
  34: or based on this library.  If you modify this library, you may extend
  35: this exception to your version of the library, but you are not
  36: obligated to do so.  If you do not wish to do so, delete this
  37: exception statement from your version. */
  38: 
  39: 
  40: package java.io;
  41: 
  42: import gnu.java.nio.FileChannelImpl;
  43: 
  44: import java.nio.channels.ByteChannel;
  45: import java.nio.channels.FileChannel;
  46: 
  47: /**
  48:  * This class represents an opaque file handle as a Java class.  It should
  49:  * be used only to pass to other methods that expect an object of this
  50:  * type.  No system specific information can be obtained from this object.
  51:  *
  52:  * @author Aaron M. Renn (arenn@urbanophile.com)
  53:  * @author Tom Tromey (tromey@cygnus.com)
  54:  * @date September 24, 1998 
  55:  */
  56: public final class FileDescriptor
  57: {
  58:   /**
  59:    * A <code>FileDescriptor</code> representing the system standard input
  60:    * stream.  This will usually be accessed through the
  61:    * <code>System.in</code>variable.
  62:    */
  63:   public static final FileDescriptor in
  64:   = new FileDescriptor (FileChannelImpl.in);
  65: 
  66:   /**
  67:    * A <code>FileDescriptor</code> representing the system standard output
  68:    * stream.  This will usually be accessed through the
  69:    * <code>System.out</code>variable.
  70:    */
  71:   public static final FileDescriptor out
  72:   = new FileDescriptor (FileChannelImpl.out);
  73: 
  74:   /**
  75:    * A <code>FileDescriptor</code> representing the system standard error
  76:    * stream.  This will usually be accessed through the
  77:    * <code>System.err</code>variable.
  78:    */
  79:   public static final FileDescriptor err
  80:   = new FileDescriptor (FileChannelImpl.err);
  81: 
  82:   final ByteChannel channel;
  83: 
  84:   /**
  85:    * This method is used to initialize an invalid FileDescriptor object.
  86:    */
  87:   public FileDescriptor()
  88:   {
  89:     channel = null;
  90:   }
  91: 
  92:   /**
  93:    * This method is used to initialize a FileDescriptor object.
  94:    */
  95:   FileDescriptor(ByteChannel channel)
  96:   {
  97:     this.channel = channel;
  98:   }
  99: 
 100: 
 101:   /**
 102:    * This method forces all data that has not yet been physically written to
 103:    * the underlying storage medium associated with this 
 104:    * <code>FileDescriptor</code>
 105:    * to be written out.  This method will not return until all data has
 106:    * been fully written to the underlying device.  If the device does not
 107:    * support this functionality or if an error occurs, then an exception
 108:    * will be thrown.
 109:    */
 110:   public void sync () throws SyncFailedException
 111:   {
 112:     if (channel instanceof FileChannel)
 113:       {
 114:     try
 115:       {
 116:         ((FileChannel) channel).force(true); 
 117:       }
 118:     catch (IOException ex)
 119:       {
 120:         if (ex instanceof SyncFailedException)
 121:           throw (SyncFailedException) ex;
 122:         else
 123:           throw new SyncFailedException(ex.toString());
 124:       }
 125:       }
 126:   }
 127: 
 128:   /**
 129:    * This methods tests whether or not this object represents a valid open
 130:    * native file handle.
 131:    *
 132:    * @return <code>true</code> if this object represents a valid 
 133:    * native file handle, <code>false</code> otherwise
 134:    */
 135:   public boolean valid ()
 136:   { 
 137:     ByteChannel c = channel;
 138:     return (c != null) && (c.isOpen());
 139:   }
 140: }