310 lines
10 KiB
Java
310 lines
10 KiB
Java
/* FileInputStream.java -- An input stream that reads from disk files.
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Copyright (C) 1998, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.io;
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import gnu.java.nio.channels.FileChannelImpl;
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import java.nio.channels.FileChannel;
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/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
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* "The Java Language Specification", ISBN 0-201-63451-1
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* plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
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* Status: Believed complete and correct.
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*/
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/**
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* This class is a stream that reads its bytes from a file.
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*
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* @author Aaron M. Renn (arenn@urbanophile.com)
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* @author Warren Levy (warrenl@cygnus.com)
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*/
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public class FileInputStream extends InputStream
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{
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/**
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* This is the native file handle for the file this stream is reading from
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*/
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private FileDescriptor fd;
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private FileChannelImpl ch;
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/**
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* This method initializes a <code>FileInputStream</code> to read from the
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* specified named file. A security check is first made to determine
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* whether or not access to this file is allowed. This is done by
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* calling the <code>checkRead()</code> method of the
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* <code>SecurityManager</code>
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* (if one exists) with the name of this file. An exception is thrown
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* if reading is not allowed. If the file does not exist, an exception
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* is also thrown.
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*
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* @param name The name of the file this stream should read from
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*
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* @exception SecurityException If read access to the file is not allowed
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* @exception FileNotFoundException If the file does not exist
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* or if it is a directory
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*/
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public FileInputStream(String name) throws FileNotFoundException
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{
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this(new File(name));
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}
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/**
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* This method initializes a <code>FileInputStream</code> to read from the
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* specified <code>File</code> object. A security check is first
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* made to determine
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* whether or not access to this file is allowed. This is done by
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* calling the <code>checkRead()</code> method of the
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* <code>SecurityManager</code>
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* (if one exists) with the name of this file. An exception is thrown
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* if reading is not allowed. If the file does not exist, an exception
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* is also thrown.
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*
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* @param file The <code>File</code> object this stream should read from
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*
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* @exception SecurityException If read access to the file is not allowed
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* @exception FileNotFoundException If the file does not exist
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* or if it is a directory.
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*/
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public FileInputStream(File file) throws FileNotFoundException
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{
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SecurityManager s = System.getSecurityManager();
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if (s != null)
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s.checkRead(file.getPath());
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ch = new FileChannelImpl (file, FileChannelImpl.READ);
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}
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/**
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* This method initializes a <code>FileInputStream</code> to read from the
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* specified <code>FileDescriptor</code> object. A security
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* check is first made to
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* determine whether or not access to this file is allowed. This is done by
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* calling the <code>checkRead()</code> method of the
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* <code>SecurityManager</code>
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* (if one exists) with the specified <code>FileDescriptor</code>
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* An exception is
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* thrown if reading is not allowed.
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*
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* @param fdObj The <code>FileDescriptor</code> object this stream
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* should read from
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*
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* @exception SecurityException If read access to the file is not allowed
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*/
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public FileInputStream(FileDescriptor fdObj)
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{
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SecurityManager s = System.getSecurityManager();
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if (s != null)
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s.checkRead(fdObj);
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fd = fdObj;
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ch = (FileChannelImpl) fdObj.channel;
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}
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FileInputStream(FileChannelImpl ch)
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{
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this.ch = ch;
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}
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/**
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* This method returns the number of bytes that can be read from this
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* stream before a read can block. A return of 0 indicates that blocking
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* might (or might not) occur on the very next read attempt.
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* <p>
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* This method returns the number of unread bytes remaining in the file if
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* the descriptor being read from is an actual file. If this method is
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* reading from a ''special'' file such a the standard input, this method
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* will return the appropriate value for the stream being read.
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* <p>
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* Be aware that reads on plain files that do not reside locally might
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* possibly block even if this method says they should not. For example,
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* a remote server might crash, preventing an NFS mounted file from being
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* read.
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*
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* @return The number of bytes that can be read before blocking could occur
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*
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* @exception IOException If an error occurs
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*/
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public int available() throws IOException
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{
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return ch.available();
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}
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/**
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* This method closes the stream. Any futher attempts to read from the
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* stream will likely generate an IOException since the underlying file
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* will be closed.
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*
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* @exception IOException If an error occurs.
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*/
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public void close() throws IOException
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{
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ch.close();
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}
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protected void finalize() throws IOException
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{
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// We don't actually need this, but we include it because it is
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// mentioned in the JCL.
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}
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/**
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* This method returns a <code>FileDescriptor</code> object representing the
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* underlying native file handle of the file this stream is reading
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* from
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*
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* @return A <code>FileDescriptor</code> for this stream
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*
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* @exception IOException If an error occurs
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*/
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public final FileDescriptor getFD() throws IOException
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{
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synchronized (this)
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{
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if (fd == null)
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fd = new FileDescriptor (ch);
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return fd;
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}
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}
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/**
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* This method reads an unsigned byte from the input stream and returns it
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* as an int in the range of 0-255. This method also will return -1 if
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* the end of the stream has been reached.
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* <p>
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* This method will block until the byte can be read.
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*
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* @return The byte read or -1 if end of stream
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*
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* @exception IOException If an error occurs
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*/
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public int read() throws IOException
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{
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return ch.read();
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}
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/**
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* This method reads bytes from a stream and stores them into a caller
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* supplied buffer. This method attempts to completely fill the buffer,
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* but can return before doing so. The actual number of bytes read is
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* returned as an int. A -1 is returned to indicate the end of the stream.
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* <p>
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* This method will block until some data can be read.
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* <p>
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* This method operates by calling an overloaded read method like so:
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* <code>read(buf, 0, buf.length)</code>
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*
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* @param buf The buffer into which the bytes read will be stored.
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*
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* @return The number of bytes read or -1 if end of stream.
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*
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* @exception IOException If an error occurs.
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*/
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public int read(byte[] buf) throws IOException
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{
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return read(buf, 0, buf.length);
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}
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/**
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* This method read bytes from a stream and stores them into a caller
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* supplied buffer. It starts storing the data at index
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* <code>offset</code> into
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* the buffer and attempts to read <code>len</code> bytes. This method can
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* return before reading the number of bytes requested. The actual number
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* of bytes read is returned as an int. A -1 is returned to indicate the
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* end of the stream.
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* <p>
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* This method will block until some data can be read.
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*
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* @param buf The array into which the bytes read should be stored
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* @param offset The offset into the array to start storing bytes
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* @param len The requested number of bytes to read
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*
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* @return The actual number of bytes read, or -1 if end of stream.
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*
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* @exception IOException If an error occurs.
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*/
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public int read(byte[] buf, int offset, int len) throws IOException
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{
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if (offset < 0
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|| len < 0
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|| offset + len > buf.length)
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throw new ArrayIndexOutOfBoundsException();
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return ch.read(buf, offset, len);
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}
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/**
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* This method skips the specified number of bytes in the stream. It
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* returns the actual number of bytes skipped, which may be less than the
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* requested amount.
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* <p>
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* @param numBytes The requested number of bytes to skip
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*
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* @return The actual number of bytes skipped.
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*
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* @exception IOException If an error occurs
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*/
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public synchronized long skip (long numBytes) throws IOException
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{
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if (numBytes < 0)
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throw new IllegalArgumentException ("Can't skip negative bytes: " +
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numBytes);
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if (numBytes == 0)
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return 0;
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long oldPos = ch.position ();
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ch.position(oldPos + numBytes);
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return ch.position() - oldPos;
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}
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/**
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* This method creates a java.nio.channels.FileChannel.
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* Nio does not allow one to create a file channel directly.
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* A file channel must be created by first creating an instance of
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* Input/Output/RandomAccessFile and invoking the getChannel() method on it.
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*/
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public synchronized FileChannel getChannel ()
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{
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return ch;
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}
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} // class FileInputStream
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