/*
 * Copyright (c) 1994, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation. Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.io;

import java.nio.channels.FileChannel;

import jdk.internal.access.JavaIORandomAccessFileAccess;
import jdk.internal.access.SharedSecrets;
import sun.nio.ch.FileChannelImpl;


/**
 * Instances of this class support both reading and writing to a
 * random access file. A random access file behaves like a large
 * array of bytes stored in the file system. There is a kind of cursor,
 * or index into the implied array, called the <em>file pointer</em>;
 * input operations read bytes starting at the file pointer and advance
 * the file pointer past the bytes read. If the random access file is
 * created in read/write mode, then output operations are also available;
 * output operations write bytes starting at the file pointer and advance
 * the file pointer past the bytes written. Output operations that write
 * past the current end of the implied array cause the array to be
 * extended. The file pointer can be read by the
 * {@code getFilePointer} method and set by the {@code seek}
 * method.
 * <p>
 * It is generally true of all the reading routines in this class that
 * if end-of-file is reached before the desired number of bytes has been
 * read, an {@code EOFException} (which is a kind of
 * {@code IOException}) is thrown. If any byte cannot be read for
 * any reason other than end-of-file, an {@code IOException} other
 * than {@code EOFException} is thrown. In particular, an
 * {@code IOException} may be thrown if the stream has been closed.
 *
 * @author unascribed
 * @since 1.0
 */

public class RandomAccessFile implements DataOutput, DataInput, Closeable {

 private FileDescriptor fd;
 private volatile FileChannel channel;
 private boolean rw;

 /**
 * The path of the referenced file
 * (null if the stream is created with a file descriptor)
 */
 private final String path;

 private final Object closeLock = new Object();

 private volatile boolean closed;

 private static final int O_RDONLY = 1;
 private static final int O_RDWR = 2;
 private static final int O_SYNC = 4;
 private static final int O_DSYNC = 8;
 private static final int O_TEMPORARY = 16;

 /**
 * Creates a random access file stream to read from, and optionally
 * to write to, a file with the specified name. A new
 * {@link FileDescriptor} object is created to represent the
 * connection to the file.
 *
 * <p> The {@code mode} argument specifies the access mode with which the
 * file is to be opened. The permitted values and their meanings are as
 * specified for the <a
 * href="#mode">{@code RandomAccessFile(File,String)}</a> constructor.
 *
 * <p>
 * If there is a security manager, its {@code checkRead} method
 * is called with the {@code name} argument
 * as its argument to see if read access to the file is allowed.
 * If the mode allows writing, the security manager's
 * {@code checkWrite} method
 * is also called with the {@code name} argument
 * as its argument to see if write access to the file is allowed.
 *
 * @param name the system-dependent filename
 * @param mode the access <a href="#mode">mode</a>
 * @exception IllegalArgumentException if the mode argument is not equal
 * to one of {@code "r"}, {@code "rw"}, {@code "rws"}, or
 * {@code "rwd"}
 * @exception FileNotFoundException
 * if the mode is {@code "r"} but the given string does not
 * denote an existing regular file, or if the mode begins with
 * {@code "rw"} but the given string does not denote an
 * existing, writable regular file and a new regular file of
 * that name cannot be created, or if some other error occurs
 * while opening or creating the file
 * @exception SecurityException if a security manager exists and its
 * {@code checkRead} method denies read access to the file
 * or the mode is {@code "rw"} and the security manager's
 * {@code checkWrite} method denies write access to the file
 * @see java.lang.SecurityException
 * @see java.lang.SecurityManager#checkRead(java.lang.String)
 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
 * @revised 1.4
 * @spec JSR-51
 */
 public RandomAccessFile(String name, String mode)
 throws FileNotFoundException
 {
 this(name != null ? new File(name) : null, mode);
 }

 /**
 * Creates a random access file stream to read from, and optionally to
 * write to, the file specified by the {@link File} argument. A new {@link
 * FileDescriptor} object is created to represent this file connection.
 *
 * <p>The <a id="mode">{@code mode}</a> argument specifies the access mode
 * in which the file is to be opened. The permitted values and their
 * meanings are:
 *
 * <table class="striped">
 * <caption style="display:none">Access mode permitted values and meanings</caption>
 * <thead>
 * <tr><th scope="col" style="text-align:left">Value</th><th scope="col" style="text-align:left">Meaning</th></tr>
 * </thead>
 * <tbody>
 * <tr><th scope="row" style="vertical-align:top">{@code "r"}</th>
 * <td> Open for reading only. Invoking any of the {@code write}
 * methods of the resulting object will cause an
 * {@link java.io.IOException} to be thrown.</td></tr>
 * <tr><th scope="row" style="vertical-align:top">{@code "rw"}</th>
 * <td> Open for reading and writing. If the file does not already
 * exist then an attempt will be made to create it.</td></tr>
 * <tr><th scope="row" style="vertical-align:top">{@code "rws"}</th>
 * <td> Open for reading and writing, as with {@code "rw"}, and also
 * require that every update to the file's content or metadata be
 * written synchronously to the underlying storage device.</td></tr>
 * <tr><th scope="row" style="vertical-align:top">{@code "rwd"}</th>
 * <td> Open for reading and writing, as with {@code "rw"}, and also
 * require that every update to the file's content be written
 * synchronously to the underlying storage device.</td></tr>
 * </tbody>
 * </table>
 *
 * The {@code "rws"} and {@code "rwd"} modes work much like the {@link
 * java.nio.channels.FileChannel#force(boolean) force(boolean)} method of
 * the {@link java.nio.channels.FileChannel} class, passing arguments of
 * {@code true} and {@code false}, respectively, except that they always
 * apply to every I/O operation and are therefore often more efficient. If
 * the file resides on a local storage device then when an invocation of a
 * method of this class returns it is guaranteed that all changes made to
 * the file by that invocation will have been written to that device. This
 * is useful for ensuring that critical information is not lost in the
 * event of a system crash. If the file does not reside on a local device
 * then no such guarantee is made.
 *
 * <p>The {@code "rwd"} mode can be used to reduce the number of I/O
 * operations performed. Using {@code "rwd"} only requires updates to the
 * file's content to be written to storage; using {@code "rws"} requires
 * updates to both the file's content and its metadata to be written, which
 * generally requires at least one more low-level I/O operation.
 *
 * <p>If there is a security manager, its {@code checkRead} method is
 * called with the pathname of the {@code file} argument as its
 * argument to see if read access to the file is allowed. If the mode
 * allows writing, the security manager's {@code checkWrite} method is
 * also called with the path argument to see if write access to the file is
 * allowed.
 *
 * @param file the file object
 * @param mode the access mode, as described
 * <a href="#mode">above</a>
 * @exception IllegalArgumentException if the mode argument is not equal
 * to one of {@code "r"}, {@code "rw"}, {@code "rws"}, or
 * {@code "rwd"}
 * @exception FileNotFoundException
 * if the mode is {@code "r"} but the given file object does
 * not denote an existing regular file, or if the mode begins
 * with {@code "rw"} but the given file object does not denote
 * an existing, writable regular file and a new regular file of
 * that name cannot be created, or if some other error occurs
 * while opening or creating the file
 * @exception SecurityException if a security manager exists and its
 * {@code checkRead} method denies read access to the file
 * or the mode is {@code "rw"} and the security manager's
 * {@code checkWrite} method denies write access to the file
 * @see java.lang.SecurityManager#checkRead(java.lang.String)
 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
 * @see java.nio.channels.FileChannel#force(boolean)
 * @revised 1.4
 * @spec JSR-51
 */
 public RandomAccessFile(File file, String mode)
 throws FileNotFoundException
 {
 this(file, mode, false);
 }

 private RandomAccessFile(File file, String mode, boolean openAndDelete)
 throws FileNotFoundException
 {
 String name = (file != null ? file.getPath() : null);
 int imode = -1;
 if (mode.equals("r"))
 imode = O_RDONLY;
 else if (mode.startsWith("rw")) {
 imode = O_RDWR;
 rw = true;
 if (mode.length() > 2) {
 if (mode.equals("rws"))
 imode |= O_SYNC;
 else if (mode.equals("rwd"))
 imode |= O_DSYNC;
 else
 imode = -1;
 }
 }
 if (openAndDelete)
 imode |= O_TEMPORARY;
 if (imode < 0)
 throw new IllegalArgumentException("Illegal mode \"" + mode
 + "\" must be one of "
 + "\"r\", \"rw\", \"rws\","
 + " or \"rwd\"");
 SecurityManager security = System.getSecurityManager();
 if (security != null) {
 security.checkRead(name);
 if (rw) {
 security.checkWrite(name);
 }
 }
 if (name == null) {
 throw new NullPointerException();
 }
 if (file.isInvalid()) {
 throw new FileNotFoundException("Invalid file path");
 }
 fd = new FileDescriptor();
 fd.attach(this);
 path = name;
 open(name, imode);
 FileCleanable.register(fd); // open sets the fd, register the cleanup
 }

 /**
 * Returns the opaque file descriptor object associated with this
 * stream.
 *
 * @return the file descriptor object associated with this stream.
 * @exception IOException if an I/O error occurs.
 * @see java.io.FileDescriptor
 */
 public final FileDescriptor getFD() throws IOException {
 if (fd != null) {
 return fd;
 }
 throw new IOException();
 }

 /**
 * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
 * object associated with this file.
 *
 * <p> The {@link java.nio.channels.FileChannel#position()
 * position} of the returned channel will always be equal to
 * this object's file-pointer offset as returned by the {@link
 * #getFilePointer getFilePointer} method. Changing this object's
 * file-pointer offset, whether explicitly or by reading or writing bytes,
 * will change the position of the channel, and vice versa. Changing the
 * file's length via this object will change the length seen via the file
 * channel, and vice versa.
 *
 * @return the file channel associated with this file
 *
 * @since 1.4
 * @spec JSR-51
 */
 public final FileChannel getChannel() {
 FileChannel fc = this.channel;
 if (fc == null) {
 synchronized (this) {
 fc = this.channel;
 if (fc == null) {
 this.channel = fc = FileChannelImpl.open(fd, path, true,
 rw, false, this);
 if (closed) {
 try {
 fc.close();
 } catch (IOException ioe) {
 throw new InternalError(ioe); // should not happen
 }
 }
 }
 }
 }
 return fc;
 }

 /**
 * Opens a file and returns the file descriptor. The file is
 * opened in read-write mode if the O_RDWR bit in {@code mode}
 * is true, else the file is opened as read-only.
 * If the {@code name} refers to a directory, an IOException
 * is thrown.
 *
 * @param name the name of the file
 * @param mode the mode flags, a combination of the O_ constants
 * defined above
 */
 private native void open0(String name, int mode)
 throws FileNotFoundException;

 // wrap native call to allow instrumentation
 /**
 * Opens a file and returns the file descriptor. The file is
 * opened in read-write mode if the O_RDWR bit in {@code mode}
 * is true, else the file is opened as read-only.
 * If the {@code name} refers to a directory, an IOException
 * is thrown.
 *
 * @param name the name of the file
 * @param mode the mode flags, a combination of the O_ constants
 * defined above
 */
 private void open(String name, int mode)
 throws FileNotFoundException {
 open0(name, mode);
 }

 // 'Read' primitives

 /**
 * Reads a byte of data from this file. The byte is returned as an
 * integer in the range 0 to 255 ({@code 0x00-0x0ff}). This
 * method blocks if no input is yet available.
 * <p>
 * Although {@code RandomAccessFile} is not a subclass of
 * {@code InputStream}, this method behaves in exactly the same
 * way as the {@link InputStream#read()} method of
 * {@code InputStream}.
 *
 * @return the next byte of data, or {@code -1} if the end of the
 * file has been reached.
 * @exception IOException if an I/O error occurs. Not thrown if
 * end-of-file has been reached.
 */
 public int read() throws IOException {
 return read0();
 }

 private native int read0() throws IOException;

 /**
 * Reads a sub array as a sequence of bytes.
 * @param b the buffer into which the data is read.
 * @param off the start offset of the data.
 * @param len the number of bytes to read.
 * @exception IOException If an I/O error has occurred.
 */
 private native int readBytes(byte b[], int off, int len) throws IOException;

 /**
 * Reads up to {@code len} bytes of data from this file into an
 * array of bytes. This method blocks until at least one byte of input
 * is available.
 * <p>
 * Although {@code RandomAccessFile} is not a subclass of
 * {@code InputStream}, this method behaves in exactly the
 * same way as the {@link InputStream#read(byte[], int, int)} method of
 * {@code InputStream}.
 *
 * @param b the buffer into which the data is read.
 * @param off the start offset in array {@code b}
 * at which the data is written.
 * @param len the maximum number of bytes read.
 * @return the total number of bytes read into the buffer, or
 * {@code -1} if there is no more data because the end of
 * the file has been reached.
 * @exception IOException If the first byte cannot be read for any reason
 * other than end of file, or if the random access file has been closed, or if
 * some other I/O error occurs.
 * @exception NullPointerException If {@code b} is {@code null}.
 * @exception IndexOutOfBoundsException If {@code off} is negative,
 * {@code len} is negative, or {@code len} is greater than
 * {@code b.length - off}
 */
 public int read(byte b[], int off, int len) throws IOException {
 return readBytes(b, off, len);
 }

 /**
 * Reads up to {@code b.length} bytes of data from this file
 * into an array of bytes. This method blocks until at least one byte
 * of input is available.
 * <p>
 * Although {@code RandomAccessFile} is not a subclass of
 * {@code InputStream}, this method behaves in exactly the
 * same way as the {@link InputStream#read(byte[])} method of
 * {@code InputStream}.
 *
 * @param b the buffer into which the data is read.
 * @return the total number of bytes read into the buffer, or
 * {@code -1} if there is no more data because the end of
 * this file has been reached.
 * @exception IOException If the first byte cannot be read for any reason
 * other than end of file, or if the random access file has been closed, or if
 * some other I/O error occurs.
 * @exception NullPointerException If {@code b} is {@code null}.
 */
 public int read(byte b[]) throws IOException {
 return readBytes(b, 0, b.length);
 }

 /**
 * Reads {@code b.length} bytes from this file into the byte
 * array, starting at the current file pointer. This method reads
 * repeatedly from the file until the requested number of bytes are
 * read. This method blocks until the requested number of bytes are
 * read, the end of the stream is detected, or an exception is thrown.
 *
 * @param b the buffer into which the data is read.
 * @throws NullPointerException if {@code b} is {@code null}.
 * @throws EOFException if this file reaches the end before reading
 * all the bytes.
 * @throws IOException if an I/O error occurs.
 */
 public final void readFully(byte b[]) throws IOException {
 readFully(b, 0, b.length);
 }

 /**
 * Reads exactly {@code len} bytes from this file into the byte
 * array, starting at the current file pointer. This method reads
 * repeatedly from the file until the requested number of bytes are
 * read. This method blocks until the requested number of bytes are
 * read, the end of the stream is detected, or an exception is thrown.
 *
 * @param b the buffer into which the data is read.
 * @param off the start offset into the data array {@code b}.
 * @param len the number of bytes to read.
 * @throws NullPointerException if {@code b} is {@code null}.
 * @throws IndexOutOfBoundsException if {@code off} is negative,
 * {@code len} is negative, or {@code len} is greater than
 * {@code b.length - off}.
 * @throws EOFException if this file reaches the end before reading
 * all the bytes.
 * @throws IOException if an I/O error occurs.
 */
 public final void readFully(byte b[], int off, int len) throws IOException {
 int n = 0;
 do {
 int count = this.read(b, off + n, len - n);
 if (count < 0)
 throw new EOFException();
 n += count;
 } while (n < len);
 }

 /**
 * Attempts to skip over {@code n} bytes of input discarding the
 * skipped bytes.
 * <p>
 *
 * This method may skip over some smaller number of bytes, possibly zero.
 * This may result from any of a number of conditions; reaching end of
 * file before {@code n} bytes have been skipped is only one
 * possibility. This method never throws an {@code EOFException}.
 * The actual number of bytes skipped is returned. If {@code n}
 * is negative, no bytes are skipped.
 *
 * @param n the number of bytes to be skipped.
 * @return the actual number of bytes skipped.
 * @exception IOException if an I/O error occurs.
 */
 public int skipBytes(int n) throws IOException {
 long pos;
 long len;
 long newpos;

 if (n <= 0) {
 return 0;
 }
 pos = getFilePointer();
 len = length();
 newpos = pos + n;
 if (newpos > len) {
 newpos = len;
 }
 seek(newpos);

 /* return the actual number of bytes skipped */
 return (int) (newpos - pos);
 }

 // 'Write' primitives

 /**
 * Writes the specified byte to this file. The write starts at
 * the current file pointer.
 *
 * @param b the {@code byte} to be written.
 * @exception IOException if an I/O error occurs.
 */
 public void write(int b) throws IOException {
 write0(b);
 }

 private native void write0(int b) throws IOException;

 /**
 * Writes a sub array as a sequence of bytes.
 * @param b the data to be written

 * @param off the start offset in the data
 * @param len the number of bytes that are written
 * @exception IOException If an I/O error has occurred.
 */
 private native void writeBytes(byte b[], int off, int len) throws IOException;

 /**
 * Writes {@code b.length} bytes from the specified byte array
 * to this file, starting at the current file pointer.
 *
 * @param b the data.
 * @exception IOException if an I/O error occurs.
 */
 public void write(byte b[]) throws IOException {
 writeBytes(b, 0, b.length);
 }

 /**
 * Writes {@code len} bytes from the specified byte array
 * starting at offset {@code off} to this file.
 *
 * @param b the data.
 * @param off the start offset in the data.
 * @param len the number of bytes to write.
 * @exception IOException if an I/O error occurs.
 */
 public void write(byte b[], int off, int len) throws IOException {
 writeBytes(b, off, len);
 }

 // 'Random access' stuff

 /**
 * Returns the current offset in this file.
 *
 * @return the offset from the beginning of the file, in bytes,
 * at which the next read or write occurs.
 * @exception IOException if an I/O error occurs.
 */
 public native long getFilePointer() throws IOException;

 /**
 * Sets the file-pointer offset, measured from the beginning of this
 * file, at which the next read or write occurs. The offset may be
 * set beyond the end of the file. Setting the offset beyond the end
 * of the file does not change the file length. The file length will
 * change only by writing after the offset has been set beyond the end
 * of the file.
 *
 * @param pos the offset position, measured in bytes from the
 * beginning of the file, at which to set the file
 * pointer.
 * @exception IOException if {@code pos} is less than
 * {@code 0} or if an I/O error occurs.
 */
 public void seek(long pos) throws IOException {
 if (pos < 0) {
 throw new IOException("Negative seek offset");
 } else {
 seek0(pos);
 }
 }

 private native void seek0(long pos) throws IOException;

 /**
 * Returns the length of this file.
 *
 * @return the length of this file, measured in bytes.
 * @exception IOException if an I/O error occurs.
 */
 public native long length() throws IOException;

 /**
 * Sets the length of this file.
 *
 * <p> If the present length of the file as returned by the
 * {@code length} method is greater than the {@code newLength}
 * argument then the file will be truncated. In this case, if the file
 * offset as returned by the {@code getFilePointer} method is greater
 * than {@code newLength} then after this method returns the offset
 * will be equal to {@code newLength}.
 *
 * <p> If the present length of the file as returned by the
 * {@code length} method is smaller than the {@code newLength}
 * argument then the file will be extended. In this case, the contents of
 * the extended portion of the file are not defined.
 *
 * @param newLength The desired length of the file
 * @exception IOException If an I/O error occurs
 * @since 1.2
 */
 public native void setLength(long newLength) throws IOException;

 /**
 * Closes this random access file stream and releases any system
 * resources associated with the stream. A closed random access
 * file cannot perform input or output operations and cannot be
 * reopened.
 *
 * <p> If this file has an associated channel then the channel is closed
 * as well.
 *
 * @exception IOException if an I/O error occurs.
 *
 * @revised 1.4
 * @spec JSR-51
 */
 public void close() throws IOException {
 if (closed) {
 return;
 }
 synchronized (closeLock) {
 if (closed) {
 return;
 }
 closed = true;
 }

 FileChannel fc = channel;
 if (fc != null) {
 // possible race with getChannel(), benign since
 // FileChannel.close is final and idempotent
 fc.close();
 }

 fd.closeAll(new Closeable() {
 public void close() throws IOException {
 fd.close();
 }
 });
 }

 //
 // Some "reading/writing Java data types" methods stolen from
 // DataInputStream and DataOutputStream.
 //

 /**
 * Reads a {@code boolean} from this file. This method reads a
 * single byte from the file, starting at the current file pointer.
 * A value of {@code 0} represents
 * {@code false}. Any other value represents {@code true}.
 * This method blocks until the byte is read, the end of the stream
 * is detected, or an exception is thrown.
 *
 * @return the {@code boolean} value read.
 * @exception EOFException if this file has reached the end.
 * @exception IOException if an I/O error occurs.
 */
 public final boolean readBoolean() throws IOException {
 int ch = this.read();
 if (ch < 0)
 throw new EOFException();
 return (ch != 0);
 }

 /**
 * Reads a signed eight-bit value from this file. This method reads a
 * byte from the file, starting from the current file pointer.
 * If the byte read is {@code b}, where
 * <code>0&nbsp;&lt;=&nbsp;b&nbsp;&lt;=&nbsp;255</code>,
 * then the result is:
 * <blockquote><pre>
 * (byte)(b)
 * </pre></blockquote>
 * <p>
 * This method blocks until the byte is read, the end of the stream
 * is detected, or an exception is thrown.
 *
 * @return the next byte of this file as a signed eight-bit
 * {@code byte}.
 * @exception EOFException if this file has reached the end.
 * @exception IOException if an I/O error occurs.
 */
 public final byte readByte() throws IOException {
 int ch = this.read();
 if (ch < 0)
 throw new EOFException();
 return (byte)(ch);
 }

 /**
 * Reads an unsigned eight-bit number from this file. This method reads
 * a byte from this file, starting at the current file pointer,
 * and returns that byte.
 * <p>
 * This method blocks until the byte is read, the end of the stream
 * is detected, or an exception is thrown.
 *
 * @return the next byte of this file, interpreted as an unsigned
 * eight-bit number.
 * @exception EOFException if this file has reached the end.
 * @exception IOException if an I/O error occurs.
 */
 public final int readUnsignedByte() throws IOException {
 int ch = this.read();
 if (ch < 0)
 throw new EOFException();
 return ch;
 }

 /**
 * Reads a signed 16-bit number from this file. The method reads two
 * bytes from this file, starting at the current file pointer.
 * If the two bytes read, in order, are
 * {@code b1} and {@code b2}, where each of the two values is
 * between {@code 0} and {@code 255}, inclusive, then the
 * result is equal to:
 * <blockquote><pre>
 * (short)((b1 &lt;&lt; 8) | b2)
 * </pre></blockquote>
 * <p>
 * This method blocks until the two bytes are read, the end of the
 * stream is detected, or an exception is thrown.
 *
 * @return the next two bytes of this file, interpreted as a signed
 * 16-bit number.
 * @exception EOFException if this file reaches the end before reading
 * two bytes.
 * @exception IOException if an I/O error occurs.
 */
 public final short readShort() throws IOException {
 int ch1 = this.read();
 int ch2 = this.read();
 if ((ch1 | ch2) < 0)
 throw new EOFException();
 return (short)((ch1 << 8) + (ch2 << 0));
 }

 /**
 * Reads an unsigned 16-bit number from this file. This method reads
 * two bytes from the file, starting at the current file pointer.
 * If the bytes read, in order, are
 * {@code b1} and {@code b2}, where
 * <code>0&nbsp;&lt;=&nbsp;b1, b2&nbsp;&lt;=&nbsp;255</code>,
 * then the result is equal to:
 * <blockquote><pre>
 * (b1 &lt;&lt; 8) | b2
 * </pre></blockquote>
 * <p>
 * This method blocks until the two bytes are read, the end of the
 * stream is detected, or an exception is thrown.
 *
 * @return the next two bytes of this file, interpreted as an unsigned
 * 16-bit integer.
 * @exception EOFException if this file reaches the end before reading
 * two bytes.
 * @exception IOException if an I/O error occurs.
 */
 public final int readUnsignedShort() throws IOException {
 int ch1 = this.read();
 int ch2 = this.read();
 if ((ch1 | ch2) < 0)
 throw new EOFException();
 return (ch1 << 8) + (ch2 << 0);
 }

 /**
 * Reads a character from this file. This method reads two
 * bytes from the file, starting at the current file pointer.
 * If the bytes read, in order, are
 * {@code b1} and {@code b2}, where
 * <code>0&nbsp;&lt;=&nbsp;b1,&nbsp;b2&nbsp;&lt;=&nbsp;255</code>,
 * then the result is equal to:
 * <blockquote><pre>
 * (char)((b1 &lt;&lt; 8) | b2)
 * </pre></blockquote>
 * <p>
 * This method blocks until the two bytes are read, the end of the
 * stream is detected, or an exception is thrown.
 *
 * @return the next two bytes of this file, interpreted as a
 * {@code char}.
 * @exception EOFException if this file reaches the end before reading
 * two bytes.
 * @exception IOException if an I/O error occurs.
 */
 public final char readChar() throws IOException {
 int ch1 = this.read();
 int ch2 = this.read();
 if ((ch1 | ch2) < 0)
 throw new EOFException();
 return (char)((ch1 << 8) + (ch2 << 0));
 }

 /**
 * Reads a signed 32-bit integer from this file. This method reads 4
 * bytes from the file, starting at the current file pointer.
 * If the bytes read, in order, are {@code b1},
 * {@code b2}, {@code b3}, and {@code b4}, where
 * <code>0&nbsp;&lt;=&nbsp;b1, b2, b3, b4&nbsp;&lt;=&nbsp;255</code>,
 * then the result is equal to:
 * <blockquote><pre>
 * (b1 &lt;&lt; 24) | (b2 &lt;&lt; 16) + (b3 &lt;&lt; 8) + b4
 * </pre></blockquote>
 * <p>
 * This method blocks until the four bytes are read, the end of the
 * stream is detected, or an exception is thrown.
 *
 * @return the next four bytes of this file, interpreted as an
 * {@code int}.
 * @exception EOFException if this file reaches the end before reading
 * four bytes.
 * @exception IOException if an I/O error occurs.
 */
 public final int readInt() throws IOException {
 int ch1 = this.read();
 int ch2 = this.read();
 int ch3 = this.read();
 int ch4 = this.read();
 if ((ch1 | ch2 | ch3 | ch4) < 0)
 throw new EOFException();
 return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
 }

 /**
 * Reads a signed 64-bit integer from this file. This method reads eight
 * bytes from the file, starting at the current file pointer.
 * If the bytes read, in order, are
 * {@code b1}, {@code b2}, {@code b3},
 * {@code b4}, {@code b5}, {@code b6},
 * {@code b7}, and {@code b8,} where:
 * <blockquote><pre>
 * 0 &lt;= b1, b2, b3, b4, b5, b6, b7, b8 &lt;=255,
 * </pre></blockquote>
 * <p>
 * then the result is equal to:
 * <blockquote><pre>
 * ((long)b1 &lt;&lt; 56) + ((long)b2 &lt;&lt; 48)
 * + ((long)b3 &lt;&lt; 40) + ((long)b4 &lt;&lt; 32)
 * + ((long)b5 &lt;&lt; 24) + ((long)b6 &lt;&lt; 16)
 * + ((long)b7 &lt;&lt; 8) + b8
 * </pre></blockquote>
 * <p>
 * This method blocks until the eight bytes are read, the end of the
 * stream is detected, or an exception is thrown.
 *
 * @return the next eight bytes of this file, interpreted as a
 * {@code long}.
 * @exception EOFException if this file reaches the end before reading
 * eight bytes.
 * @exception IOException if an I/O error occurs.
 */
 public final long readLong() throws IOException {
 return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
 }

 /**
 * Reads a {@code float} from this file. This method reads an
 * {@code int} value, starting at the current file pointer,
 * as if by the {@code readInt} method
 * and then converts that {@code int} to a {@code float}
 * using the {@code intBitsToFloat} method in class
 * {@code Float}.
 * <p>
 * This method blocks until the four bytes are read, the end of the
 * stream is detected, or an exception is thrown.
 *
 * @return the next four bytes of this file, interpreted as a
 * {@code float}.
 * @exception EOFException if this file reaches the end before reading
 * four bytes.
 * @exception IOException if an I/O error occurs.
 * @see java.io.RandomAccessFile#readInt()
 * @see java.lang.Float#intBitsToFloat(int)
 */
 public final float readFloat() throws IOException {
 return Float.intBitsToFloat(readInt());
 }

 /**
 * Reads a {@code double} from this file. This method reads a
 * {@code long} value, starting at the current file pointer,
 * as if by the {@code readLong} method
 * and then converts that {@code long} to a {@code double}
 * using the {@code longBitsToDouble} method in
 * class {@code Double}.
 * <p>
 * This method blocks until the eight bytes are read, the end of the
 * stream is detected, or an exception is thrown.
 *
 * @return the next eight bytes of this file, interpreted as a
 * {@code double}.
 * @exception EOFException if this file reaches the end before reading
 * eight bytes.
 * @exception IOException if an I/O error occurs.
 * @see java.io.RandomAccessFile#readLong()
 * @see java.lang.Double#longBitsToDouble(long)
 */
 public final double readDouble() throws IOException {
 return Double.longBitsToDouble(readLong());
 }

 /**
 * Reads the next line of text from this file. This method successively
 * reads bytes from the file, starting at the current file pointer,
 * until it reaches a line terminator or the end
 * of the file. Each byte is converted into a character by taking the
 * byte's value for the lower eight bits of the character and setting the
 * high eight bits of the character to zero. This method does not,
 * therefore, support the full Unicode character set.
 *
 * <p> A line of text is terminated by a carriage-return character
 * ({@code '\u005Cr'}), a newline character ({@code '\u005Cn'}), a
 * carriage-return character immediately followed by a newline character,
 * or the end of the file. Line-terminating characters are discarded and
 * are not included as part of the string returned.
 *
 * <p> This method blocks until a newline character is read, a carriage
 * return and the byte following it are read (to see if it is a newline),
 * the end of the file is reached, or an exception is thrown.
 *
 * @return the next line of text from this file, or null if end
 * of file is encountered before even one byte is read.
 * @exception IOException if an I/O error occurs.
 */

 public final String readLine() throws IOException {
 StringBuilder input = new StringBuilder();
 int c = -1;
 boolean eol = false;

 while (!eol) {
 switch (c = read()) {
 case -1:
 case '\n':
 eol = true;
 break;
 case '\r':
 eol = true;
 long cur = getFilePointer();
 if ((read()) != '\n') {
 seek(cur);
 }
 break;
 default:
 input.append((char)c);
 break;
 }
 }

 if ((c == -1) && (input.length() == 0)) {
 return null;
 }
 return input.toString();
 }

 /**
 * Reads in a string from this file. The string has been encoded
 * using a
 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
 * format.
 * <p>
 * The first two bytes are read, starting from the current file
 * pointer, as if by
 * {@code readUnsignedShort}. This value gives the number of
 * following bytes that are in the encoded string, not
 * the length of the resulting string. The following bytes are then
 * interpreted as bytes encoding characters in the modified UTF-8 format
 * and are converted into characters.
 * <p>
 * This method blocks until all the bytes are read, the end of the
 * stream is detected, or an exception is thrown.
 *
 * @return a Unicode string.
 * @exception EOFException if this file reaches the end before
 * reading all the bytes.
 * @exception IOException if an I/O error occurs.
 * @exception UTFDataFormatException if the bytes do not represent
 * valid modified UTF-8 encoding of a Unicode string.
 * @see java.io.RandomAccessFile#readUnsignedShort()
 */
 public final String readUTF() throws IOException {
 return DataInputStream.readUTF(this);
 }

 /**
 * Writes a {@code boolean} to the file as a one-byte value. The
 * value {@code true} is written out as the value
 * {@code (byte)1}; the value {@code false} is written out
 * as the value {@code (byte)0}. The write starts at
 * the current position of the file pointer.
 *
 * @param v a {@code boolean} value to be written.
 * @exception IOException if an I/O error occurs.
 */
 public final void writeBoolean(boolean v) throws IOException {
 write(v ? 1 : 0);
 //written++;
 }

 /**
 * Writes a {@code byte} to the file as a one-byte value. The
 * write starts at the current position of the file pointer.
 *
 * @param v a {@code byte} value to be written.
 * @exception IOException if an I/O error occurs.
 */
 public final void writeByte(int v) throws IOException {
 write(v);
 //written++;
 }

 /**
 * Writes a {@code short} to the file as two bytes, high byte first.
 * The write starts at the current position of the file pointer.
 *
 * @param v a {@code short} to be written.
 * @exception IOException if an I/O error occurs.
 */
 public final void writeShort(int v) throws IOException {
 write((v >>> 8) & 0xFF);
 write((v >>> 0) & 0xFF);
 //written += 2;
 }

 /**
 * Writes a {@code char} to the file as a two-byte value, high
 * byte first. The write starts at the current position of the
 * file pointer.
 *
 * @param v a {@code char} value to be written.
 * @exception IOException if an I/O error occurs.
 */
 public final void writeChar(int v) throws IOException {
 write((v >>> 8) & 0xFF);
 write((v >>> 0) & 0xFF);
 //written += 2;
 }

 /**
 * Writes an {@code int} to the file as four bytes, high byte first.
 * The write starts at the current position of the file pointer.
 *
 * @param v an {@code int} to be written.
 * @exception IOException if an I/O error occurs.
 */
 public final void writeInt(int v) throws IOException {
 write((v >>> 24) & 0xFF);
 write((v >>> 16) & 0xFF);
 write((v >>> 8) & 0xFF);
 write((v >>> 0) & 0xFF);
 //written += 4;
 }

 /**
 * Writes a {@code long} to the file as eight bytes, high byte first.
 * The write starts at the current position of the file pointer.
 *
 * @param v a {@code long} to be written.
 * @exception IOException if an I/O error occurs.
 */
 public final void writeLong(long v) throws IOException {
 write((int)(v >>> 56) & 0xFF);
 write((int)(v >>> 48) & 0xFF);
 write((int)(v >>> 40) & 0xFF);
 write((int)(v >>> 32) & 0xFF);
 write((int)(v >>> 24) & 0xFF);
 write((int)(v >>> 16) & 0xFF);
 write((int)(v >>> 8) & 0xFF);
 write((int)(v >>> 0) & 0xFF);
 //written += 8;
 }

 /**
 * Converts the float argument to an {@code int} using the
 * {@code floatToIntBits} method in class {@code Float},
 * and then writes that {@code int} value to the file as a
 * four-byte quantity, high byte first. The write starts at the
 * current position of the file pointer.
 *
 * @param v a {@code float} value to be written.
 * @exception IOException if an I/O error occurs.
 * @see java.lang.Float#floatToIntBits(float)
 */
 public final void writeFloat(float v) throws IOException {
 writeInt(Float.floatToIntBits(v));
 }

 /**
 * Converts the double argument to a {@code long} using the
 * {@code doubleToLongBits} method in class {@code Double},
 * and then writes that {@code long} value to the file as an
 * eight-byte quantity, high byte first. The write starts at the current
 * position of the file pointer.
 *
 * @param v a {@code double} value to be written.
 * @exception IOException if an I/O error occurs.
 * @see java.lang.Double#doubleToLongBits(double)
 */
 public final void writeDouble(double v) throws IOException {
 writeLong(Double.doubleToLongBits(v));
 }

 /**
 * Writes the string to the file as a sequence of bytes. Each
 * character in the string is written out, in sequence, by discarding
 * its high eight bits. The write starts at the current position of
 * the file pointer.
 *
 * @param s a string of bytes to be written.
 * @exception IOException if an I/O error occurs.
 */
 @SuppressWarnings("deprecation")
 public final void writeBytes(String s) throws IOException {
 int len = s.length();
 byte[] b = new byte[len];
 s.getBytes(0, len, b, 0);
 writeBytes(b, 0, len);
 }

 /**
 * Writes a string to the file as a sequence of characters. Each
 * character is written to the data output stream as if by the
 * {@code writeChar} method. The write starts at the current
 * position of the file pointer.
 *
 * @param s a {@code String} value to be written.
 * @exception IOException if an I/O error occurs.
 * @see java.io.RandomAccessFile#writeChar(int)
 */
 public final void writeChars(String s) throws IOException {
 int clen = s.length();
 int blen = 2*clen;
 byte[] b = new byte[blen];
 char[] c = new char[clen];
 s.getChars(0, clen, c, 0);
 for (int i = 0, j = 0; i < clen; i++) {
 b[j++] = (byte)(c[i] >>> 8);
 b[j++] = (byte)(c[i] >>> 0);
 }
 writeBytes(b, 0, blen);
 }

 /**
 * Writes a string to the file using
 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
 * encoding in a machine-independent manner.
 * <p>
 * First, two bytes are written to the file, starting at the
 * current file pointer, as if by the
 * {@code writeShort} method giving the number of bytes to
 * follow. This value is the number of bytes actually written out,
 * not the length of the string. Following the length, each character
 * of the string is output, in sequence, using the modified UTF-8 encoding
 * for each character.
 *
 * @param str a string to be written.
 * @exception IOException if an I/O error occurs.
 */
 public final void writeUTF(String str) throws IOException {
 DataOutputStream.writeUTF(str, this);
 }

 private static native void initIDs();

 static {
 initIDs();
 SharedSecrets.setJavaIORandomAccessFileAccess(new JavaIORandomAccessFileAccess()
 {
 // This is for j.u.z.ZipFile.OPEN_DELETE. The O_TEMPORARY flag
 // is only implemented/supported on windows.
 public RandomAccessFile openAndDelete(File file, String mode)
 throws IOException
 {
 return new RandomAccessFile(file, mode, true);
 }
 });
 }
}