432 lines
16 KiB
Java
432 lines
16 KiB
Java
/*
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* Copyright (c) 1994, 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.io;
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import java.nio.channels.FileChannel;
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import sun.nio.ch.FileChannelImpl;
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/**
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* A {@code FileInputStream} obtains input bytes
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* from a file in a file system. What files
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* are available depends on the host environment.
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*
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* <p>{@code FileInputStream} is meant for reading streams of raw bytes
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* such as image data. For reading streams of characters, consider using
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* {@code FileReader}.
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*
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* @apiNote
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* To release resources used by this stream {@link #close} should be called
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* directly or by try-with-resources. Subclasses are responsible for the cleanup
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* of resources acquired by the subclass.
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* Subclasses that override {@link #finalize} in order to perform cleanup
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* should be modified to use alternative cleanup mechanisms such as
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* {@link java.lang.ref.Cleaner} and remove the overriding {@code finalize} method.
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*
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* @implSpec
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* If this FileInputStream has been subclassed and the {@link #close}
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* method has been overridden, the {@link #close} method will be
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* called when the FileInputStream is unreachable.
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* Otherwise, it is implementation specific how the resource cleanup described in
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* {@link #close} is performed.
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*
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* @author Arthur van Hoff
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* @see java.io.File
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* @see java.io.FileDescriptor
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* @see java.io.FileOutputStream
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* @see java.nio.file.Files#newInputStream
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* @since 1.0
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*/
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public class FileInputStream extends InputStream
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{
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/* File Descriptor - handle to the open file */
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private final FileDescriptor fd;
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/**
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* The path of the referenced file
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* (null if the stream is created with a file descriptor)
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*/
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private final String path;
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private volatile FileChannel channel;
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private final Object closeLock = new Object();
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private volatile boolean closed;
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/**
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* Creates a {@code FileInputStream} by
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* opening a connection to an actual file,
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* the file named by the path name {@code name}
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* in the file system. A new {@code FileDescriptor}
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* object is created to represent this file
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* connection.
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* <p>
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* First, if there is a security
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* manager, its {@code checkRead} method
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* is called with the {@code name} argument
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* as its argument.
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* <p>
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* If the named file does not exist, is a directory rather than a regular
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* file, or for some other reason cannot be opened for reading then a
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* {@code FileNotFoundException} is thrown.
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*
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* @param name the system-dependent file name.
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* @throws FileNotFoundException if the file does not exist,
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* is a directory rather than a regular file,
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* or for some other reason cannot be opened for
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* reading.
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* @throws SecurityException if a security manager exists and its
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* {@code checkRead} method denies read access
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* to the file.
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* @see java.lang.SecurityManager#checkRead(java.lang.String)
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*/
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public FileInputStream(String name) throws FileNotFoundException {
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this(name != null ? new File(name) : null);
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}
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/**
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* Creates a {@code FileInputStream} by
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* opening a connection to an actual file,
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* the file named by the {@code File}
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* object {@code file} in the file system.
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* A new {@code FileDescriptor} object
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* is created to represent this file connection.
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* <p>
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* First, if there is a security manager,
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* its {@code checkRead} method is called
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* with the path represented by the {@code file}
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* argument as its argument.
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* <p>
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* If the named file does not exist, is a directory rather than a regular
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* file, or for some other reason cannot be opened for reading then a
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* {@code FileNotFoundException} is thrown.
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*
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* @param file the file to be opened for reading.
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* @throws FileNotFoundException if the file does not exist,
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* is a directory rather than a regular file,
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* or for some other reason cannot be opened for
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* reading.
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* @throws SecurityException if a security manager exists and its
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* {@code checkRead} method denies read access to the file.
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* @see java.io.File#getPath()
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* @see java.lang.SecurityManager#checkRead(java.lang.String)
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*/
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public FileInputStream(File file) throws FileNotFoundException {
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String name = (file != null ? file.getPath() : null);
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SecurityManager security = System.getSecurityManager();
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if (security != null) {
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security.checkRead(name);
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}
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if (name == null) {
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throw new NullPointerException();
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}
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if (file.isInvalid()) {
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throw new FileNotFoundException("Invalid file path");
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}
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fd = new FileDescriptor();
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fd.attach(this);
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path = name;
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open(name);
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FileCleanable.register(fd); // open set the fd, register the cleanup
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}
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/**
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* Creates a {@code FileInputStream} by using the file descriptor
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* {@code fdObj}, which represents an existing connection to an
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* actual file in the file system.
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* <p>
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* If there is a security manager, its {@code checkRead} method is
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* called with the file descriptor {@code fdObj} as its argument to
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* see if it's ok to read the file descriptor. If read access is denied
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* to the file descriptor a {@code SecurityException} is thrown.
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* <p>
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* If {@code fdObj} is null then a {@code NullPointerException}
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* is thrown.
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* <p>
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* This constructor does not throw an exception if {@code fdObj}
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* is {@link java.io.FileDescriptor#valid() invalid}.
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* However, if the methods are invoked on the resulting stream to attempt
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* I/O on the stream, an {@code IOException} is thrown.
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*
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* @param fdObj the file descriptor to be opened for reading.
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* @throws SecurityException if a security manager exists and its
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* {@code checkRead} method denies read access to the
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* file descriptor.
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* @see SecurityManager#checkRead(java.io.FileDescriptor)
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*/
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public FileInputStream(FileDescriptor fdObj) {
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SecurityManager security = System.getSecurityManager();
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if (fdObj == null) {
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throw new NullPointerException();
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}
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if (security != null) {
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security.checkRead(fdObj);
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}
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fd = fdObj;
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path = null;
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/*
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* FileDescriptor is being shared by streams.
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* Register this stream with FileDescriptor tracker.
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*/
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fd.attach(this);
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}
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/**
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* Opens the specified file for reading.
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* @param name the name of the file
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*/
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private native void open0(String name) throws FileNotFoundException;
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// wrap native call to allow instrumentation
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/**
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* Opens the specified file for reading.
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* @param name the name of the file
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*/
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private void open(String name) throws FileNotFoundException {
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open0(name);
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}
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/**
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* Reads a byte of data from this input stream. This method blocks
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* if no input is yet available.
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*
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* @return the next byte of data, or {@code -1} if the end of the
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* file is reached.
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* @throws IOException if an I/O error occurs.
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*/
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public int read() throws IOException {
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return read0();
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}
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private native int read0() throws IOException;
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/**
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* Reads a subarray as a sequence of bytes.
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* @param b the data to be written
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* @param off the start offset in the data
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* @param len the number of bytes that are written
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* @throws IOException If an I/O error has occurred.
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*/
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private native int readBytes(byte b[], int off, int len) throws IOException;
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/**
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* Reads up to {@code b.length} bytes of data from this input
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* stream into an array of bytes. This method blocks until some input
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* is available.
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*
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* @param b the buffer into which the data is read.
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* @return the total number of bytes read into the buffer, or
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* {@code -1} if there is no more data because the end of
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* the file has been reached.
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* @throws IOException if an I/O error occurs.
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*/
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public int read(byte b[]) throws IOException {
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return readBytes(b, 0, b.length);
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}
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/**
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* Reads up to {@code len} bytes of data from this input stream
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* into an array of bytes. If {@code len} is not zero, the method
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* blocks until some input is available; otherwise, no
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* bytes are read and {@code 0} is returned.
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*
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* @param b the buffer into which the data is read.
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* @param off the start offset in the destination array {@code b}
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* @param len the maximum number of bytes read.
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* @return the total number of bytes read into the buffer, or
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* {@code -1} if there is no more data because the end of
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* the file has been reached.
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* @throws NullPointerException If {@code b} is {@code null}.
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* @throws IndexOutOfBoundsException If {@code off} is negative,
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* {@code len} is negative, or {@code len} is greater than
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* {@code b.length - off}
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* @throws IOException if an I/O error occurs.
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*/
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public int read(byte b[], int off, int len) throws IOException {
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return readBytes(b, off, len);
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}
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/**
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* Skips over and discards {@code n} bytes of data from the
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* input stream.
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*
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* <p>The {@code skip} method may, for a variety of
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* reasons, end up skipping over some smaller number of bytes,
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* possibly {@code 0}. If {@code n} is negative, the method
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* will try to skip backwards. In case the backing file does not support
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* backward skip at its current position, an {@code IOException} is
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* thrown. The actual number of bytes skipped is returned. If it skips
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* forwards, it returns a positive value. If it skips backwards, it
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* returns a negative value.
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*
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* <p>This method may skip more bytes than what are remaining in the
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* backing file. This produces no exception and the number of bytes skipped
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* may include some number of bytes that were beyond the EOF of the
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* backing file. Attempting to read from the stream after skipping past
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* the end will result in -1 indicating the end of the file.
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*
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* @param n the number of bytes to be skipped.
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* @return the actual number of bytes skipped.
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* @throws IOException if n is negative, if the stream does not
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* support seek, or if an I/O error occurs.
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*/
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public long skip(long n) throws IOException {
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return skip0(n);
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}
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private native long skip0(long n) throws IOException;
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/**
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* Returns an estimate of the number of remaining bytes that can be read (or
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* skipped over) from this input stream without blocking by the next
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* invocation of a method for this input stream. Returns 0 when the file
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* position is beyond EOF. The next invocation might be the same thread
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* or another thread. A single read or skip of this many bytes will not
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* block, but may read or skip fewer bytes.
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*
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* <p> In some cases, a non-blocking read (or skip) may appear to be
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* blocked when it is merely slow, for example when reading large
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* files over slow networks.
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*
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* @return an estimate of the number of remaining bytes that can be read
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* (or skipped over) from this input stream without blocking.
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* @throws IOException if this file input stream has been closed by calling
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* {@code close} or an I/O error occurs.
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*/
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public int available() throws IOException {
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return available0();
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}
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private native int available0() throws IOException;
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/**
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* Closes this file input stream and releases any system resources
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* associated with the stream.
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*
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* <p> If this stream has an associated channel then the channel is closed
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* as well.
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*
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* @apiNote
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* Overriding {@link #close} to perform cleanup actions is reliable
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* only when called directly or when called by try-with-resources.
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* Do not depend on finalization to invoke {@code close};
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* finalization is not reliable and is deprecated.
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* If cleanup of native resources is needed, other mechanisms such as
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* {@linkplain java.lang.ref.Cleaner} should be used.
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*
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* @throws IOException if an I/O error occurs.
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*
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* @revised 1.4
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*/
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public void close() throws IOException {
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if (closed) {
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return;
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}
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synchronized (closeLock) {
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if (closed) {
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return;
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}
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closed = true;
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}
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FileChannel fc = channel;
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if (fc != null) {
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// possible race with getChannel(), benign since
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// FileChannel.close is final and idempotent
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fc.close();
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}
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fd.closeAll(new Closeable() {
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public void close() throws IOException {
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fd.close();
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}
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});
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}
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/**
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* Returns the {@code FileDescriptor}
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* object that represents the connection to
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* the actual file in the file system being
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* used by this {@code FileInputStream}.
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*
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* @return the file descriptor object associated with this stream.
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* @throws IOException if an I/O error occurs.
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* @see java.io.FileDescriptor
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*/
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public final FileDescriptor getFD() throws IOException {
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if (fd != null) {
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return fd;
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}
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throw new IOException();
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}
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/**
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* Returns the unique {@link java.nio.channels.FileChannel FileChannel}
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* object associated with this file input stream.
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*
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* <p> The initial {@link java.nio.channels.FileChannel#position()
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* position} of the returned channel will be equal to the
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* number of bytes read from the file so far. Reading bytes from this
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* stream will increment the channel's position. Changing the channel's
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* position, either explicitly or by reading, will change this stream's
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* file position.
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*
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* @return the file channel associated with this file input stream
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*
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* @since 1.4
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*/
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public FileChannel getChannel() {
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FileChannel fc = this.channel;
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if (fc == null) {
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synchronized (this) {
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fc = this.channel;
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if (fc == null) {
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this.channel = fc = FileChannelImpl.open(fd, path, true,
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false, false, this);
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if (closed) {
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try {
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// possible race with close(), benign since
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// FileChannel.close is final and idempotent
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fc.close();
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} catch (IOException ioe) {
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throw new InternalError(ioe); // should not happen
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}
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}
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}
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}
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}
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return fc;
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}
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private static native void initIDs();
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static {
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initIDs();
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}
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}
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