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.channels.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 */ FileDescriptor()87 public FileDescriptor() 88 { 89 channel = null; 90 } 91 92 /** 93 * This method is used to initialize a FileDescriptor object. 94 */ FileDescriptor(ByteChannel channel)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 */ sync()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 */ valid()135 public boolean valid () 136 { 137 return channel != null && channel.isOpen(); 138 } 139 } 140