001/* FileDescriptor.java -- Opaque file handle class 002 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004 003 Free Software Foundation, Inc. 004 005This file is part of GNU Classpath. 006 007GNU Classpath is free software; you can redistribute it and/or modify 008it under the terms of the GNU General Public License as published by 009the Free Software Foundation; either version 2, or (at your option) 010any later version. 011 012GNU Classpath is distributed in the hope that it will be useful, but 013WITHOUT ANY WARRANTY; without even the implied warranty of 014MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 015General Public License for more details. 016 017You should have received a copy of the GNU General Public License 018along with GNU Classpath; see the file COPYING. If not, write to the 019Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02002110-1301 USA. 021 022Linking this library statically or dynamically with other modules is 023making a combined work based on this library. Thus, the terms and 024conditions of the GNU General Public License cover the whole 025combination. 026 027As a special exception, the copyright holders of this library give you 028permission to link this library with independent modules to produce an 029executable, regardless of the license terms of these independent 030modules, and to copy and distribute the resulting executable under 031terms of your choice, provided that you also meet, for each linked 032independent module, the terms and conditions of the license of that 033module. An independent module is a module which is not derived from 034or based on this library. If you modify this library, you may extend 035this exception to your version of the library, but you are not 036obligated to do so. If you do not wish to do so, delete this 037exception statement from your version. */ 038 039 040package java.io; 041 042import gnu.java.nio.channels.FileChannelImpl; 043 044import java.nio.channels.ByteChannel; 045import java.nio.channels.FileChannel; 046 047/** 048 * This class represents an opaque file handle as a Java class. It should 049 * be used only to pass to other methods that expect an object of this 050 * type. No system specific information can be obtained from this object. 051 * 052 * @author Aaron M. Renn (arenn@urbanophile.com) 053 * @author Tom Tromey (tromey@cygnus.com) 054 * @date September 24, 1998 055 */ 056public final class FileDescriptor 057{ 058 /** 059 * A <code>FileDescriptor</code> representing the system standard input 060 * stream. This will usually be accessed through the 061 * <code>System.in</code>variable. 062 */ 063 public static final FileDescriptor in 064 = new FileDescriptor (FileChannelImpl.in); 065 066 /** 067 * A <code>FileDescriptor</code> representing the system standard output 068 * stream. This will usually be accessed through the 069 * <code>System.out</code>variable. 070 */ 071 public static final FileDescriptor out 072 = new FileDescriptor (FileChannelImpl.out); 073 074 /** 075 * A <code>FileDescriptor</code> representing the system standard error 076 * stream. This will usually be accessed through the 077 * <code>System.err</code>variable. 078 */ 079 public static final FileDescriptor err 080 = new FileDescriptor (FileChannelImpl.err); 081 082 final ByteChannel channel; 083 084 /** 085 * This method is used to initialize an invalid FileDescriptor object. 086 */ 087 public FileDescriptor() 088 { 089 channel = null; 090 } 091 092 /** 093 * This method is used to initialize a FileDescriptor object. 094 */ 095 FileDescriptor(ByteChannel channel) 096 { 097 this.channel = channel; 098 } 099 100 101 /** 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 return channel != null && channel.isOpen(); 138 } 139}