1 /* 2 * Copyright (c) 1995, 2012, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.io; 27 28 import android.system.ErrnoException; 29 import android.system.Os; 30 import static android.system.OsConstants.F_DUPFD_CLOEXEC; 31 32 import java.util.concurrent.atomic.AtomicInteger; 33 34 /** 35 * Instances of the file descriptor class serve as an opaque handle 36 * to the underlying machine-specific structure representing an open 37 * file, an open socket, or another source or sink of bytes. The 38 * main practical use for a file descriptor is to create a 39 * <code>FileInputStream</code> or <code>FileOutputStream</code> to 40 * contain it. 41 * <p> 42 * Applications should not create their own file descriptors. 43 * 44 * @author Pavani Diwanji 45 * @see java.io.FileInputStream 46 * @see java.io.FileOutputStream 47 * @since JDK1.0 48 */ 49 // Android-changed: Removed parent reference counting. Creator is responsible for closing 50 // the file descriptor. 51 public final class FileDescriptor { 52 53 private int descriptor; 54 55 /** 56 * Constructs an (invalid) FileDescriptor 57 * object. 58 */ FileDescriptor()59 public FileDescriptor() { 60 descriptor = -1; 61 } 62 FileDescriptor(int descriptor)63 private FileDescriptor(int descriptor) { 64 this.descriptor = descriptor; 65 } 66 67 /** 68 * A handle to the standard input stream. Usually, this file 69 * descriptor is not used directly, but rather via the input stream 70 * known as <code>System.in</code>. 71 * 72 * @see java.lang.System#in 73 */ 74 public static final FileDescriptor in = dupFd(0); 75 76 /** 77 * A handle to the standard output stream. Usually, this file 78 * descriptor is not used directly, but rather via the output stream 79 * known as <code>System.out</code>. 80 * @see java.lang.System#out 81 */ 82 public static final FileDescriptor out = dupFd(1); 83 84 /** 85 * A handle to the standard error stream. Usually, this file 86 * descriptor is not used directly, but rather via the output stream 87 * known as <code>System.err</code>. 88 * 89 * @see java.lang.System#err 90 */ 91 public static final FileDescriptor err = dupFd(2); 92 93 /** 94 * Tests if this file descriptor object is valid. 95 * 96 * @return <code>true</code> if the file descriptor object represents a 97 * valid, open file, socket, or other active I/O connection; 98 * <code>false</code> otherwise. 99 */ valid()100 public boolean valid() { 101 return descriptor != -1; 102 } 103 104 /** 105 * Force all system buffers to synchronize with the underlying 106 * device. This method returns after all modified data and 107 * attributes of this FileDescriptor have been written to the 108 * relevant device(s). In particular, if this FileDescriptor 109 * refers to a physical storage medium, such as a file in a file 110 * system, sync will not return until all in-memory modified copies 111 * of buffers associated with this FileDescriptor have been 112 * written to the physical medium. 113 * 114 * sync is meant to be used by code that requires physical 115 * storage (such as a file) to be in a known state For 116 * example, a class that provided a simple transaction facility 117 * might use sync to ensure that all changes to a file caused 118 * by a given transaction were recorded on a storage medium. 119 * 120 * sync only affects buffers downstream of this FileDescriptor. If 121 * any in-memory buffering is being done by the application (for 122 * example, by a BufferedOutputStream object), those buffers must 123 * be flushed into the FileDescriptor (for example, by invoking 124 * OutputStream.flush) before that data will be affected by sync. 125 * 126 * @exception SyncFailedException 127 * Thrown when the buffers cannot be flushed, 128 * or because the system cannot guarantee that all the 129 * buffers have been synchronized with physical media. 130 * @since JDK1.1 131 */ sync()132 public native void sync() throws SyncFailedException; 133 134 /** 135 * Returns the int descriptor. It's highly unlikely you should be calling this. Please discuss 136 * your needs with a libcore maintainer before using this method. 137 * @hide internal use only 138 */ 139 // Android-added. getInt$()140 public final int getInt$() { 141 return descriptor; 142 } 143 144 /** 145 * Sets the int descriptor. It's highly unlikely you should be calling this. Please discuss 146 * your needs with a libcore maintainer before using this method. 147 * @hide internal use only 148 */ 149 // Android-added. setInt$(int fd)150 public final void setInt$(int fd) { 151 this.descriptor = fd; 152 } 153 154 /** 155 * @hide internal use only 156 */ 157 // Android-added. isSocket$()158 public boolean isSocket$() { 159 return isSocket(descriptor); 160 } 161 162 // Android-added. dupFd(int fd)163 private static FileDescriptor dupFd(int fd) { 164 try { 165 return new FileDescriptor(Os.fcntlInt(new FileDescriptor(fd), F_DUPFD_CLOEXEC, 0)); 166 } catch (ErrnoException e) { 167 throw new RuntimeException(e); 168 } 169 } 170 isSocket(int descriptor)171 private static native boolean isSocket(int descriptor); 172 // Set up JavaIOFileDescriptorAccess in SharedSecrets 173 static { sun.misc.SharedSecrets.setJavaIOFileDescriptorAccess( new sun.misc.JavaIOFileDescriptorAccess() { public void set(FileDescriptor obj, int fd) { obj.descriptor = fd; } public int get(FileDescriptor obj) { return obj.descriptor; } public void setHandle(FileDescriptor obj, long handle) { throw new UnsupportedOperationException(); } public long getHandle(FileDescriptor obj) { throw new UnsupportedOperationException(); } } )174 sun.misc.SharedSecrets.setJavaIOFileDescriptorAccess( 175 new sun.misc.JavaIOFileDescriptorAccess() { 176 public void set(FileDescriptor obj, int fd) { 177 obj.descriptor = fd; 178 } 179 180 public int get(FileDescriptor obj) { 181 return obj.descriptor; 182 } 183 184 public void setHandle(FileDescriptor obj, long handle) { 185 throw new UnsupportedOperationException(); 186 } 187 188 public long getHandle(FileDescriptor obj) { 189 throw new UnsupportedOperationException(); 190 } 191 } 192 ); 193 } 194 195 196 } 197