1 /*
   2  * Copyright (c) 1994, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.io;
  27 
  28 import java.nio.channels.FileChannel;
  29 import java.util.concurrent.atomic.AtomicBoolean;
  30 import jdk.internal.misc.JavaIORandomAccessFileAccess;
  31 import jdk.internal.misc.SharedSecrets;
  32 import sun.nio.ch.FileChannelImpl;
  33 
  34 
  35 /**
  36  * Instances of this class support both reading and writing to a
  37  * random access file. A random access file behaves like a large
  38  * array of bytes stored in the file system. There is a kind of cursor,
  39  * or index into the implied array, called the <em>file pointer</em>;
  40  * input operations read bytes starting at the file pointer and advance
  41  * the file pointer past the bytes read. If the random access file is
  42  * created in read/write mode, then output operations are also available;
  43  * output operations write bytes starting at the file pointer and advance
  44  * the file pointer past the bytes written. Output operations that write
  45  * past the current end of the implied array cause the array to be
  46  * extended. The file pointer can be read by the
  47  * {@code getFilePointer} method and set by the {@code seek}
  48  * method.
  49  * <p>
  50  * It is generally true of all the reading routines in this class that
  51  * if end-of-file is reached before the desired number of bytes has been
  52  * read, an {@code EOFException} (which is a kind of
  53  * {@code IOException}) is thrown. If any byte cannot be read for
  54  * any reason other than end-of-file, an {@code IOException} other
  55  * than {@code EOFException} is thrown. In particular, an
  56  * {@code IOException} may be thrown if the stream has been closed.
  57  *
  58  * @author  unascribed
  59  * @since   1.0
  60  */
  61 
  62 public class RandomAccessFile implements DataOutput, DataInput, Closeable {
  63 
  64     private FileDescriptor fd;
  65     private volatile FileChannel channel;
  66     private boolean rw;
  67 
  68     /**
  69      * The path of the referenced file
  70      * (null if the stream is created with a file descriptor)
  71      */
  72     private final String path;
  73 
  74     private final AtomicBoolean closed = new AtomicBoolean(false);
  75 
  76     private static final int O_RDONLY = 1;
  77     private static final int O_RDWR =   2;
  78     private static final int O_SYNC =   4;
  79     private static final int O_DSYNC =  8;
  80     private static final int O_TEMPORARY =  16;
  81 
  82     /**
  83      * Creates a random access file stream to read from, and optionally
  84      * to write to, a file with the specified name. A new
  85      * {@link FileDescriptor} object is created to represent the
  86      * connection to the file.
  87      *
  88      * <p> The {@code mode} argument specifies the access mode with which the
  89      * file is to be opened.  The permitted values and their meanings are as
  90      * specified for the <a
  91      * href="#mode">{@code RandomAccessFile(File,String)}</a> constructor.
  92      *
  93      * <p>
  94      * If there is a security manager, its {@code checkRead} method
  95      * is called with the {@code name} argument
  96      * as its argument to see if read access to the file is allowed.
  97      * If the mode allows writing, the security manager's
  98      * {@code checkWrite} method
  99      * is also called with the {@code name} argument
 100      * as its argument to see if write access to the file is allowed.
 101      *
 102      * @param      name   the system-dependent filename
 103      * @param      mode   the access <a href="#mode">mode</a>
 104      * @exception  IllegalArgumentException  if the mode argument is not equal
 105      *             to one of {@code "r"}, {@code "rw"}, {@code "rws"}, or
 106      *             {@code "rwd"}
 107      * @exception FileNotFoundException
 108      *            if the mode is {@code "r"} but the given string does not
 109      *            denote an existing regular file, or if the mode begins with
 110      *            {@code "rw"} but the given string does not denote an
 111      *            existing, writable regular file and a new regular file of
 112      *            that name cannot be created, or if some other error occurs
 113      *            while opening or creating the file
 114      * @exception  SecurityException   if a security manager exists and its
 115      *             {@code checkRead} method denies read access to the file
 116      *             or the mode is {@code "rw"} and the security manager's
 117      *             {@code checkWrite} method denies write access to the file
 118      * @see        java.lang.SecurityException
 119      * @see        java.lang.SecurityManager#checkRead(java.lang.String)
 120      * @see        java.lang.SecurityManager#checkWrite(java.lang.String)
 121      * @revised 1.4
 122      * @spec JSR-51
 123      */
 124     public RandomAccessFile(String name, String mode)
 125         throws FileNotFoundException
 126     {
 127         this(name != null ? new File(name) : null, mode);
 128     }
 129 
 130     /**
 131      * Creates a random access file stream to read from, and optionally to
 132      * write to, the file specified by the {@link File} argument.  A new {@link
 133      * FileDescriptor} object is created to represent this file connection.
 134      *
 135      * <p>The <a id="mode">{@code mode}</a> argument specifies the access mode
 136      * in which the file is to be opened.  The permitted values and their
 137      * meanings are:
 138      *
 139      * <table class="striped">
 140      * <caption style="display:none">Access mode permitted values and meanings</caption>
 141      * <thead>
 142      * <tr><th scope="col" style="text-align:left">Value</th><th scope="col" style="text-align:left">Meaning</th></tr>
 143      * </thead>
 144      * <tbody>
 145      * <tr><th scope="row" style="vertical-align:top">{@code "r"}</th>
 146      *     <td> Open for reading only. Invoking any of the {@code write}
 147      *     methods of the resulting object will cause an
 148      *     {@link java.io.IOException} to be thrown.</td></tr>
 149      * <tr><th scope="row" style="vertical-align:top">{@code "rw"}</th>
 150      *     <td> Open for reading and writing.  If the file does not already
 151      *     exist then an attempt will be made to create it.</td></tr>
 152      * <tr><th scope="row" style="vertical-align:top">{@code "rws"}</th>
 153      *     <td> Open for reading and writing, as with {@code "rw"}, and also
 154      *     require that every update to the file's content or metadata be
 155      *     written synchronously to the underlying storage device.</td></tr>
 156      * <tr><th scope="row" style="vertical-align:top">{@code "rwd"}</th>
 157      *     <td> Open for reading and writing, as with {@code "rw"}, and also
 158      *     require that every update to the file's content be written
 159      *     synchronously to the underlying storage device.</td></tr>
 160      * </tbody>
 161      * </table>
 162      *
 163      * The {@code "rws"} and {@code "rwd"} modes work much like the {@link
 164      * java.nio.channels.FileChannel#force(boolean) force(boolean)} method of
 165      * the {@link java.nio.channels.FileChannel} class, passing arguments of
 166      * {@code true} and {@code false}, respectively, except that they always
 167      * apply to every I/O operation and are therefore often more efficient.  If
 168      * the file resides on a local storage device then when an invocation of a
 169      * method of this class returns it is guaranteed that all changes made to
 170      * the file by that invocation will have been written to that device.  This
 171      * is useful for ensuring that critical information is not lost in the
 172      * event of a system crash.  If the file does not reside on a local device
 173      * then no such guarantee is made.
 174      *
 175      * <p>The {@code "rwd"} mode can be used to reduce the number of I/O
 176      * operations performed.  Using {@code "rwd"} only requires updates to the
 177      * file's content to be written to storage; using {@code "rws"} requires
 178      * updates to both the file's content and its metadata to be written, which
 179      * generally requires at least one more low-level I/O operation.
 180      *
 181      * <p>If there is a security manager, its {@code checkRead} method is
 182      * called with the pathname of the {@code file} argument as its
 183      * argument to see if read access to the file is allowed.  If the mode
 184      * allows writing, the security manager's {@code checkWrite} method is
 185      * also called with the path argument to see if write access to the file is
 186      * allowed.
 187      *
 188      * @param      file   the file object
 189      * @param      mode   the access mode, as described
 190      *                    <a href="#mode">above</a>
 191      * @exception  IllegalArgumentException  if the mode argument is not equal
 192      *             to one of {@code "r"}, {@code "rw"}, {@code "rws"}, or
 193      *             {@code "rwd"}
 194      * @exception FileNotFoundException
 195      *            if the mode is {@code "r"} but the given file object does
 196      *            not denote an existing regular file, or if the mode begins
 197      *            with {@code "rw"} but the given file object does not denote
 198      *            an existing, writable regular file and a new regular file of
 199      *            that name cannot be created, or if some other error occurs
 200      *            while opening or creating the file
 201      * @exception  SecurityException  if a security manager exists and its
 202      *             {@code checkRead} method denies read access to the file
 203      *             or the mode is {@code "rw"} and the security manager's
 204      *             {@code checkWrite} method denies write access to the file
 205      * @see        java.lang.SecurityManager#checkRead(java.lang.String)
 206      * @see        java.lang.SecurityManager#checkWrite(java.lang.String)
 207      * @see        java.nio.channels.FileChannel#force(boolean)
 208      * @revised 1.4
 209      * @spec JSR-51
 210      */
 211     public RandomAccessFile(File file, String mode)
 212         throws FileNotFoundException
 213     {
 214         this(file, mode, false);
 215     }
 216 
 217     private RandomAccessFile(File file, String mode, boolean openAndDelete)
 218         throws FileNotFoundException
 219     {
 220         String name = (file != null ? file.getPath() : null);
 221         int imode = -1;
 222         if (mode.equals("r"))
 223             imode = O_RDONLY;
 224         else if (mode.startsWith("rw")) {
 225             imode = O_RDWR;
 226             rw = true;
 227             if (mode.length() > 2) {
 228                 if (mode.equals("rws"))
 229                     imode |= O_SYNC;
 230                 else if (mode.equals("rwd"))
 231                     imode |= O_DSYNC;
 232                 else
 233                     imode = -1;
 234             }
 235         }
 236         if (openAndDelete)
 237             imode |= O_TEMPORARY;
 238         if (imode < 0)
 239             throw new IllegalArgumentException("Illegal mode \"" + mode
 240                                                + "\" must be one of "
 241                                                + "\"r\", \"rw\", \"rws\","
 242                                                + " or \"rwd\"");
 243         SecurityManager security = System.getSecurityManager();
 244         if (security != null) {
 245             security.checkRead(name);
 246             if (rw) {
 247                 security.checkWrite(name);
 248             }
 249         }
 250         if (name == null) {
 251             throw new NullPointerException();
 252         }
 253         if (file.isInvalid()) {
 254             throw new FileNotFoundException("Invalid file path");
 255         }
 256         fd = new FileDescriptor();
 257         fd.attach(this);
 258         path = name;
 259         open(name, imode);
 260         FileCleanable.register(fd);   // open sets the fd, register the cleanup
 261     }
 262 
 263     /**
 264      * Returns the opaque file descriptor object associated with this
 265      * stream.
 266      *
 267      * @return     the file descriptor object associated with this stream.
 268      * @exception  IOException  if an I/O error occurs.
 269      * @see        java.io.FileDescriptor
 270      */
 271     public final FileDescriptor getFD() throws IOException {
 272         if (fd != null) {
 273             return fd;
 274         }
 275         throw new IOException();
 276     }
 277 
 278     /**
 279      * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
 280      * object associated with this file.
 281      *
 282      * <p> The {@link java.nio.channels.FileChannel#position()
 283      * position} of the returned channel will always be equal to
 284      * this object's file-pointer offset as returned by the {@link
 285      * #getFilePointer getFilePointer} method.  Changing this object's
 286      * file-pointer offset, whether explicitly or by reading or writing bytes,
 287      * will change the position of the channel, and vice versa.  Changing the
 288      * file's length via this object will change the length seen via the file
 289      * channel, and vice versa.
 290      *
 291      * @return  the file channel associated with this file
 292      *
 293      * @since 1.4
 294      * @spec JSR-51
 295      */
 296     public final FileChannel getChannel() {
 297         FileChannel fc = this.channel;
 298         if (fc == null) {
 299             synchronized (this) {
 300                 fc = this.channel;
 301                 if (fc == null) {
 302                     this.channel = fc = FileChannelImpl.open(fd, path, true,
 303                         rw, false, this);
 304                     if (closed.get()) {
 305                         try {
 306                             fc.close();
 307                         } catch (IOException ioe) {
 308                             throw new InternalError(ioe); // should not happen
 309                         }
 310                     }
 311                 }
 312             }
 313         }
 314         return fc;
 315     }
 316 
 317     /**
 318      * Opens a file and returns the file descriptor.  The file is
 319      * opened in read-write mode if the O_RDWR bit in {@code mode}
 320      * is true, else the file is opened as read-only.
 321      * If the {@code name} refers to a directory, an IOException
 322      * is thrown.
 323      *
 324      * @param name the name of the file
 325      * @param mode the mode flags, a combination of the O_ constants
 326      *             defined above
 327      */
 328     private native void open0(String name, int mode)
 329         throws FileNotFoundException;
 330 
 331     // wrap native call to allow instrumentation
 332     /**
 333      * Opens a file and returns the file descriptor.  The file is
 334      * opened in read-write mode if the O_RDWR bit in {@code mode}
 335      * is true, else the file is opened as read-only.
 336      * If the {@code name} refers to a directory, an IOException
 337      * is thrown.
 338      *
 339      * @param name the name of the file
 340      * @param mode the mode flags, a combination of the O_ constants
 341      *             defined above
 342      */
 343     private void open(String name, int mode)
 344         throws FileNotFoundException {
 345         open0(name, mode);
 346     }
 347 
 348     // 'Read' primitives
 349 
 350     /**
 351      * Reads a byte of data from this file. The byte is returned as an
 352      * integer in the range 0 to 255 ({@code 0x00-0x0ff}). This
 353      * method blocks if no input is yet available.
 354      * <p>
 355      * Although {@code RandomAccessFile} is not a subclass of
 356      * {@code InputStream}, this method behaves in exactly the same
 357      * way as the {@link InputStream#read()} method of
 358      * {@code InputStream}.
 359      *
 360      * @return     the next byte of data, or {@code -1} if the end of the
 361      *             file has been reached.
 362      * @exception  IOException  if an I/O error occurs. Not thrown if
 363      *                          end-of-file has been reached.
 364      */
 365     public int read() throws IOException {
 366         return read0();
 367     }
 368 
 369     private native int read0() throws IOException;
 370 
 371     /**
 372      * Reads a sub array as a sequence of bytes.
 373      * @param b the buffer into which the data is read.
 374      * @param off the start offset of the data.
 375      * @param len the number of bytes to read.
 376      * @exception IOException If an I/O error has occurred.
 377      */
 378     private native int readBytes(byte b[], int off, int len) throws IOException;
 379 
 380     /**
 381      * Reads up to {@code len} bytes of data from this file into an
 382      * array of bytes. This method blocks until at least one byte of input
 383      * is available.
 384      * <p>
 385      * Although {@code RandomAccessFile} is not a subclass of
 386      * {@code InputStream}, this method behaves in exactly the
 387      * same way as the {@link InputStream#read(byte[], int, int)} method of
 388      * {@code InputStream}.
 389      *
 390      * @param      b     the buffer into which the data is read.
 391      * @param      off   the start offset in array {@code b}
 392      *                   at which the data is written.
 393      * @param      len   the maximum number of bytes read.
 394      * @return     the total number of bytes read into the buffer, or
 395      *             {@code -1} if there is no more data because the end of
 396      *             the file has been reached.
 397      * @exception  IOException If the first byte cannot be read for any reason
 398      * other than end of file, or if the random access file has been closed, or if
 399      * some other I/O error occurs.
 400      * @exception  NullPointerException If {@code b} is {@code null}.
 401      * @exception  IndexOutOfBoundsException If {@code off} is negative,
 402      * {@code len} is negative, or {@code len} is greater than
 403      * {@code b.length - off}
 404      */
 405     public int read(byte b[], int off, int len) throws IOException {
 406         return readBytes(b, off, len);
 407     }
 408 
 409     /**
 410      * Reads up to {@code b.length} bytes of data from this file
 411      * into an array of bytes. This method blocks until at least one byte
 412      * of input is available.
 413      * <p>
 414      * Although {@code RandomAccessFile} is not a subclass of
 415      * {@code InputStream}, this method behaves in exactly the
 416      * same way as the {@link InputStream#read(byte[])} method of
 417      * {@code InputStream}.
 418      *
 419      * @param      b   the buffer into which the data is read.
 420      * @return     the total number of bytes read into the buffer, or
 421      *             {@code -1} if there is no more data because the end of
 422      *             this file has been reached.
 423      * @exception  IOException If the first byte cannot be read for any reason
 424      * other than end of file, or if the random access file has been closed, or if
 425      * some other I/O error occurs.
 426      * @exception  NullPointerException If {@code b} is {@code null}.
 427      */
 428     public int read(byte b[]) throws IOException {
 429         return readBytes(b, 0, b.length);
 430     }
 431 
 432     /**
 433      * Reads {@code b.length} bytes from this file into the byte
 434      * array, starting at the current file pointer. This method reads
 435      * repeatedly from the file until the requested number of bytes are
 436      * read. This method blocks until the requested number of bytes are
 437      * read, the end of the stream is detected, or an exception is thrown.
 438      *
 439      * @param   b   the buffer into which the data is read.
 440      * @throws  NullPointerException if {@code b} is {@code null}.
 441      * @throws  EOFException  if this file reaches the end before reading
 442      *              all the bytes.
 443      * @throws  IOException   if an I/O error occurs.
 444      */
 445     public final void readFully(byte b[]) throws IOException {
 446         readFully(b, 0, b.length);
 447     }
 448 
 449     /**
 450      * Reads exactly {@code len} bytes from this file into the byte
 451      * array, starting at the current file pointer. This method reads
 452      * repeatedly from the file until the requested number of bytes are
 453      * read. This method blocks until the requested number of bytes are
 454      * read, the end of the stream is detected, or an exception is thrown.
 455      *
 456      * @param   b     the buffer into which the data is read.
 457      * @param   off   the start offset into the data array {@code b}.
 458      * @param   len   the number of bytes to read.
 459      * @throws  NullPointerException if {@code b} is {@code null}.
 460      * @throws  IndexOutOfBoundsException if {@code off} is negative,
 461      *                {@code len} is negative, or {@code len} is greater than
 462      *                {@code b.length - off}.
 463      * @throws  EOFException  if this file reaches the end before reading
 464      *                all the bytes.
 465      * @throws  IOException   if an I/O error occurs.
 466      */
 467     public final void readFully(byte b[], int off, int len) throws IOException {
 468         int n = 0;
 469         do {
 470             int count = this.read(b, off + n, len - n);
 471             if (count < 0)
 472                 throw new EOFException();
 473             n += count;
 474         } while (n < len);
 475     }
 476 
 477     /**
 478      * Attempts to skip over {@code n} bytes of input discarding the
 479      * skipped bytes.
 480      * <p>
 481      *
 482      * This method may skip over some smaller number of bytes, possibly zero.
 483      * This may result from any of a number of conditions; reaching end of
 484      * file before {@code n} bytes have been skipped is only one
 485      * possibility. This method never throws an {@code EOFException}.
 486      * The actual number of bytes skipped is returned.  If {@code n}
 487      * is negative, no bytes are skipped.
 488      *
 489      * @param      n   the number of bytes to be skipped.
 490      * @return     the actual number of bytes skipped.
 491      * @exception  IOException  if an I/O error occurs.
 492      */
 493     public int skipBytes(int n) throws IOException {
 494         long pos;
 495         long len;
 496         long newpos;
 497 
 498         if (n <= 0) {
 499             return 0;
 500         }
 501         pos = getFilePointer();
 502         len = length();
 503         newpos = pos + n;
 504         if (newpos > len) {
 505             newpos = len;
 506         }
 507         seek(newpos);
 508 
 509         /* return the actual number of bytes skipped */
 510         return (int) (newpos - pos);
 511     }
 512 
 513     // 'Write' primitives
 514 
 515     /**
 516      * Writes the specified byte to this file. The write starts at
 517      * the current file pointer.
 518      *
 519      * @param      b   the {@code byte} to be written.
 520      * @exception  IOException  if an I/O error occurs.
 521      */
 522     public void write(int b) throws IOException {
 523         write0(b);
 524     }
 525 
 526     private native void write0(int b) throws IOException;
 527 
 528     /**
 529      * Writes a sub array as a sequence of bytes.
 530      * @param b the data to be written
 531 
 532      * @param off the start offset in the data
 533      * @param len the number of bytes that are written
 534      * @exception IOException If an I/O error has occurred.
 535      */
 536     private native void writeBytes(byte b[], int off, int len) throws IOException;
 537 
 538     /**
 539      * Writes {@code b.length} bytes from the specified byte array
 540      * to this file, starting at the current file pointer.
 541      *
 542      * @param      b   the data.
 543      * @exception  IOException  if an I/O error occurs.
 544      */
 545     public void write(byte b[]) throws IOException {
 546         writeBytes(b, 0, b.length);
 547     }
 548 
 549     /**
 550      * Writes {@code len} bytes from the specified byte array
 551      * starting at offset {@code off} to this file.
 552      *
 553      * @param      b     the data.
 554      * @param      off   the start offset in the data.
 555      * @param      len   the number of bytes to write.
 556      * @exception  IOException  if an I/O error occurs.
 557      */
 558     public void write(byte b[], int off, int len) throws IOException {
 559         writeBytes(b, off, len);
 560     }
 561 
 562     // 'Random access' stuff
 563 
 564     /**
 565      * Returns the current offset in this file.
 566      *
 567      * @return     the offset from the beginning of the file, in bytes,
 568      *             at which the next read or write occurs.
 569      * @exception  IOException  if an I/O error occurs.
 570      */
 571     public native long getFilePointer() throws IOException;
 572 
 573     /**
 574      * Sets the file-pointer offset, measured from the beginning of this
 575      * file, at which the next read or write occurs.  The offset may be
 576      * set beyond the end of the file. Setting the offset beyond the end
 577      * of the file does not change the file length.  The file length will
 578      * change only by writing after the offset has been set beyond the end
 579      * of the file.
 580      *
 581      * @param      pos   the offset position, measured in bytes from the
 582      *                   beginning of the file, at which to set the file
 583      *                   pointer.
 584      * @exception  IOException  if {@code pos} is less than
 585      *                          {@code 0} or if an I/O error occurs.
 586      */
 587     public void seek(long pos) throws IOException {
 588         if (pos < 0) {
 589             throw new IOException("Negative seek offset");
 590         } else {
 591             seek0(pos);
 592         }
 593     }
 594 
 595     private native void seek0(long pos) throws IOException;
 596 
 597     /**
 598      * Returns the length of this file.
 599      *
 600      * @return     the length of this file, measured in bytes.
 601      * @exception  IOException  if an I/O error occurs.
 602      */
 603     public native long length() throws IOException;
 604 
 605     /**
 606      * Sets the length of this file.
 607      *
 608      * <p> If the present length of the file as returned by the
 609      * {@code length} method is greater than the {@code newLength}
 610      * argument then the file will be truncated.  In this case, if the file
 611      * offset as returned by the {@code getFilePointer} method is greater
 612      * than {@code newLength} then after this method returns the offset
 613      * will be equal to {@code newLength}.
 614      *
 615      * <p> If the present length of the file as returned by the
 616      * {@code length} method is smaller than the {@code newLength}
 617      * argument then the file will be extended.  In this case, the contents of
 618      * the extended portion of the file are not defined.
 619      *
 620      * @param      newLength    The desired length of the file
 621      * @exception  IOException  If an I/O error occurs
 622      * @since      1.2
 623      */
 624     public native void setLength(long newLength) throws IOException;
 625 
 626     /**
 627      * Closes this random access file stream and releases any system
 628      * resources associated with the stream. A closed random access
 629      * file cannot perform input or output operations and cannot be
 630      * reopened.
 631      *
 632      * <p> If this file has an associated channel then the channel is closed
 633      * as well.
 634      *
 635      * @exception  IOException  if an I/O error occurs.
 636      *
 637      * @revised 1.4
 638      * @spec JSR-51
 639      */
 640     public void close() throws IOException {
 641         if (!closed.compareAndSet(false, true)) {
 642             // if compareAndSet() returns false closed was already true
 643             return;
 644         }
 645 
 646         FileChannel fc = channel;
 647         if (fc != null) {
 648            fc.close();
 649         }
 650 
 651         fd.closeAll(new Closeable() {
 652             public void close() throws IOException {
 653                fd.close();
 654            }
 655         });
 656     }
 657 
 658     //
 659     //  Some "reading/writing Java data types" methods stolen from
 660     //  DataInputStream and DataOutputStream.
 661     //
 662 
 663     /**
 664      * Reads a {@code boolean} from this file. This method reads a
 665      * single byte from the file, starting at the current file pointer.
 666      * A value of {@code 0} represents
 667      * {@code false}. Any other value represents {@code true}.
 668      * This method blocks until the byte is read, the end of the stream
 669      * is detected, or an exception is thrown.
 670      *
 671      * @return     the {@code boolean} value read.
 672      * @exception  EOFException  if this file has reached the end.
 673      * @exception  IOException   if an I/O error occurs.
 674      */
 675     public final boolean readBoolean() throws IOException {
 676         int ch = this.read();
 677         if (ch < 0)
 678             throw new EOFException();
 679         return (ch != 0);
 680     }
 681 
 682     /**
 683      * Reads a signed eight-bit value from this file. This method reads a
 684      * byte from the file, starting from the current file pointer.
 685      * If the byte read is {@code b}, where
 686      * <code>0&nbsp;&lt;=&nbsp;b&nbsp;&lt;=&nbsp;255</code>,
 687      * then the result is:
 688      * <blockquote><pre>
 689      *     (byte)(b)
 690      * </pre></blockquote>
 691      * <p>
 692      * This method blocks until the byte is read, the end of the stream
 693      * is detected, or an exception is thrown.
 694      *
 695      * @return     the next byte of this file as a signed eight-bit
 696      *             {@code byte}.
 697      * @exception  EOFException  if this file has reached the end.
 698      * @exception  IOException   if an I/O error occurs.
 699      */
 700     public final byte readByte() throws IOException {
 701         int ch = this.read();
 702         if (ch < 0)
 703             throw new EOFException();
 704         return (byte)(ch);
 705     }
 706 
 707     /**
 708      * Reads an unsigned eight-bit number from this file. This method reads
 709      * a byte from this file, starting at the current file pointer,
 710      * and returns that byte.
 711      * <p>
 712      * This method blocks until the byte is read, the end of the stream
 713      * is detected, or an exception is thrown.
 714      *
 715      * @return     the next byte of this file, interpreted as an unsigned
 716      *             eight-bit number.
 717      * @exception  EOFException  if this file has reached the end.
 718      * @exception  IOException   if an I/O error occurs.
 719      */
 720     public final int readUnsignedByte() throws IOException {
 721         int ch = this.read();
 722         if (ch < 0)
 723             throw new EOFException();
 724         return ch;
 725     }
 726 
 727     /**
 728      * Reads a signed 16-bit number from this file. The method reads two
 729      * bytes from this file, starting at the current file pointer.
 730      * If the two bytes read, in order, are
 731      * {@code b1} and {@code b2}, where each of the two values is
 732      * between {@code 0} and {@code 255}, inclusive, then the
 733      * result is equal to:
 734      * <blockquote><pre>
 735      *     (short)((b1 &lt;&lt; 8) | b2)
 736      * </pre></blockquote>
 737      * <p>
 738      * This method blocks until the two bytes are read, the end of the
 739      * stream is detected, or an exception is thrown.
 740      *
 741      * @return     the next two bytes of this file, interpreted as a signed
 742      *             16-bit number.
 743      * @exception  EOFException  if this file reaches the end before reading
 744      *               two bytes.
 745      * @exception  IOException   if an I/O error occurs.
 746      */
 747     public final short readShort() throws IOException {
 748         int ch1 = this.read();
 749         int ch2 = this.read();
 750         if ((ch1 | ch2) < 0)
 751             throw new EOFException();
 752         return (short)((ch1 << 8) + (ch2 << 0));
 753     }
 754 
 755     /**
 756      * Reads an unsigned 16-bit number from this file. This method reads
 757      * two bytes from the file, starting at the current file pointer.
 758      * If the bytes read, in order, are
 759      * {@code b1} and {@code b2}, where
 760      * <code>0&nbsp;&lt;=&nbsp;b1, b2&nbsp;&lt;=&nbsp;255</code>,
 761      * then the result is equal to:
 762      * <blockquote><pre>
 763      *     (b1 &lt;&lt; 8) | b2
 764      * </pre></blockquote>
 765      * <p>
 766      * This method blocks until the two bytes are read, the end of the
 767      * stream is detected, or an exception is thrown.
 768      *
 769      * @return     the next two bytes of this file, interpreted as an unsigned
 770      *             16-bit integer.
 771      * @exception  EOFException  if this file reaches the end before reading
 772      *               two bytes.
 773      * @exception  IOException   if an I/O error occurs.
 774      */
 775     public final int readUnsignedShort() throws IOException {
 776         int ch1 = this.read();
 777         int ch2 = this.read();
 778         if ((ch1 | ch2) < 0)
 779             throw new EOFException();
 780         return (ch1 << 8) + (ch2 << 0);
 781     }
 782 
 783     /**
 784      * Reads a character from this file. This method reads two
 785      * bytes from the file, starting at the current file pointer.
 786      * If the bytes read, in order, are
 787      * {@code b1} and {@code b2}, where
 788      * <code>0&nbsp;&lt;=&nbsp;b1,&nbsp;b2&nbsp;&lt;=&nbsp;255</code>,
 789      * then the result is equal to:
 790      * <blockquote><pre>
 791      *     (char)((b1 &lt;&lt; 8) | b2)
 792      * </pre></blockquote>
 793      * <p>
 794      * This method blocks until the two bytes are read, the end of the
 795      * stream is detected, or an exception is thrown.
 796      *
 797      * @return     the next two bytes of this file, interpreted as a
 798      *                  {@code char}.
 799      * @exception  EOFException  if this file reaches the end before reading
 800      *               two bytes.
 801      * @exception  IOException   if an I/O error occurs.
 802      */
 803     public final char readChar() throws IOException {
 804         int ch1 = this.read();
 805         int ch2 = this.read();
 806         if ((ch1 | ch2) < 0)
 807             throw new EOFException();
 808         return (char)((ch1 << 8) + (ch2 << 0));
 809     }
 810 
 811     /**
 812      * Reads a signed 32-bit integer from this file. This method reads 4
 813      * bytes from the file, starting at the current file pointer.
 814      * If the bytes read, in order, are {@code b1},
 815      * {@code b2}, {@code b3}, and {@code b4}, where
 816      * <code>0&nbsp;&lt;=&nbsp;b1, b2, b3, b4&nbsp;&lt;=&nbsp;255</code>,
 817      * then the result is equal to:
 818      * <blockquote><pre>
 819      *     (b1 &lt;&lt; 24) | (b2 &lt;&lt; 16) + (b3 &lt;&lt; 8) + b4
 820      * </pre></blockquote>
 821      * <p>
 822      * This method blocks until the four bytes are read, the end of the
 823      * stream is detected, or an exception is thrown.
 824      *
 825      * @return     the next four bytes of this file, interpreted as an
 826      *             {@code int}.
 827      * @exception  EOFException  if this file reaches the end before reading
 828      *               four bytes.
 829      * @exception  IOException   if an I/O error occurs.
 830      */
 831     public final int readInt() throws IOException {
 832         int ch1 = this.read();
 833         int ch2 = this.read();
 834         int ch3 = this.read();
 835         int ch4 = this.read();
 836         if ((ch1 | ch2 | ch3 | ch4) < 0)
 837             throw new EOFException();
 838         return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
 839     }
 840 
 841     /**
 842      * Reads a signed 64-bit integer from this file. This method reads eight
 843      * bytes from the file, starting at the current file pointer.
 844      * If the bytes read, in order, are
 845      * {@code b1}, {@code b2}, {@code b3},
 846      * {@code b4}, {@code b5}, {@code b6},
 847      * {@code b7}, and {@code b8,} where:
 848      * <blockquote><pre>
 849      *     0 &lt;= b1, b2, b3, b4, b5, b6, b7, b8 &lt;=255,
 850      * </pre></blockquote>
 851      * <p>
 852      * then the result is equal to:
 853      * <blockquote><pre>
 854      *     ((long)b1 &lt;&lt; 56) + ((long)b2 &lt;&lt; 48)
 855      *     + ((long)b3 &lt;&lt; 40) + ((long)b4 &lt;&lt; 32)
 856      *     + ((long)b5 &lt;&lt; 24) + ((long)b6 &lt;&lt; 16)
 857      *     + ((long)b7 &lt;&lt; 8) + b8
 858      * </pre></blockquote>
 859      * <p>
 860      * This method blocks until the eight bytes are read, the end of the
 861      * stream is detected, or an exception is thrown.
 862      *
 863      * @return     the next eight bytes of this file, interpreted as a
 864      *             {@code long}.
 865      * @exception  EOFException  if this file reaches the end before reading
 866      *               eight bytes.
 867      * @exception  IOException   if an I/O error occurs.
 868      */
 869     public final long readLong() throws IOException {
 870         return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
 871     }
 872 
 873     /**
 874      * Reads a {@code float} from this file. This method reads an
 875      * {@code int} value, starting at the current file pointer,
 876      * as if by the {@code readInt} method
 877      * and then converts that {@code int} to a {@code float}
 878      * using the {@code intBitsToFloat} method in class
 879      * {@code Float}.
 880      * <p>
 881      * This method blocks until the four bytes are read, the end of the
 882      * stream is detected, or an exception is thrown.
 883      *
 884      * @return     the next four bytes of this file, interpreted as a
 885      *             {@code float}.
 886      * @exception  EOFException  if this file reaches the end before reading
 887      *             four bytes.
 888      * @exception  IOException   if an I/O error occurs.
 889      * @see        java.io.RandomAccessFile#readInt()
 890      * @see        java.lang.Float#intBitsToFloat(int)
 891      */
 892     public final float readFloat() throws IOException {
 893         return Float.intBitsToFloat(readInt());
 894     }
 895 
 896     /**
 897      * Reads a {@code double} from this file. This method reads a
 898      * {@code long} value, starting at the current file pointer,
 899      * as if by the {@code readLong} method
 900      * and then converts that {@code long} to a {@code double}
 901      * using the {@code longBitsToDouble} method in
 902      * class {@code Double}.
 903      * <p>
 904      * This method blocks until the eight bytes are read, the end of the
 905      * stream is detected, or an exception is thrown.
 906      *
 907      * @return     the next eight bytes of this file, interpreted as a
 908      *             {@code double}.
 909      * @exception  EOFException  if this file reaches the end before reading
 910      *             eight bytes.
 911      * @exception  IOException   if an I/O error occurs.
 912      * @see        java.io.RandomAccessFile#readLong()
 913      * @see        java.lang.Double#longBitsToDouble(long)
 914      */
 915     public final double readDouble() throws IOException {
 916         return Double.longBitsToDouble(readLong());
 917     }
 918 
 919     /**
 920      * Reads the next line of text from this file.  This method successively
 921      * reads bytes from the file, starting at the current file pointer,
 922      * until it reaches a line terminator or the end
 923      * of the file.  Each byte is converted into a character by taking the
 924      * byte's value for the lower eight bits of the character and setting the
 925      * high eight bits of the character to zero.  This method does not,
 926      * therefore, support the full Unicode character set.
 927      *
 928      * <p> A line of text is terminated by a carriage-return character
 929      * ({@code '\u005Cr'}), a newline character ({@code '\u005Cn'}), a
 930      * carriage-return character immediately followed by a newline character,
 931      * or the end of the file.  Line-terminating characters are discarded and
 932      * are not included as part of the string returned.
 933      *
 934      * <p> This method blocks until a newline character is read, a carriage
 935      * return and the byte following it are read (to see if it is a newline),
 936      * the end of the file is reached, or an exception is thrown.
 937      *
 938      * @return     the next line of text from this file, or null if end
 939      *             of file is encountered before even one byte is read.
 940      * @exception  IOException  if an I/O error occurs.
 941      */
 942 
 943     public final String readLine() throws IOException {
 944         StringBuilder input = new StringBuilder();
 945         int c = -1;
 946         boolean eol = false;
 947 
 948         while (!eol) {
 949             switch (c = read()) {
 950             case -1:
 951             case '\n':
 952                 eol = true;
 953                 break;
 954             case '\r':
 955                 eol = true;
 956                 long cur = getFilePointer();
 957                 if ((read()) != '\n') {
 958                     seek(cur);
 959                 }
 960                 break;
 961             default:
 962                 input.append((char)c);
 963                 break;
 964             }
 965         }
 966 
 967         if ((c == -1) && (input.length() == 0)) {
 968             return null;
 969         }
 970         return input.toString();
 971     }
 972 
 973     /**
 974      * Reads in a string from this file. The string has been encoded
 975      * using a
 976      * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
 977      * format.
 978      * <p>
 979      * The first two bytes are read, starting from the current file
 980      * pointer, as if by
 981      * {@code readUnsignedShort}. This value gives the number of
 982      * following bytes that are in the encoded string, not
 983      * the length of the resulting string. The following bytes are then
 984      * interpreted as bytes encoding characters in the modified UTF-8 format
 985      * and are converted into characters.
 986      * <p>
 987      * This method blocks until all the bytes are read, the end of the
 988      * stream is detected, or an exception is thrown.
 989      *
 990      * @return     a Unicode string.
 991      * @exception  EOFException            if this file reaches the end before
 992      *               reading all the bytes.
 993      * @exception  IOException             if an I/O error occurs.
 994      * @exception  UTFDataFormatException  if the bytes do not represent
 995      *               valid modified UTF-8 encoding of a Unicode string.
 996      * @see        java.io.RandomAccessFile#readUnsignedShort()
 997      */
 998     public final String readUTF() throws IOException {
 999         return DataInputStream.readUTF(this);
1000     }
1001 
1002     /**
1003      * Writes a {@code boolean} to the file as a one-byte value. The
1004      * value {@code true} is written out as the value
1005      * {@code (byte)1}; the value {@code false} is written out
1006      * as the value {@code (byte)0}. The write starts at
1007      * the current position of the file pointer.
1008      *
1009      * @param      v   a {@code boolean} value to be written.
1010      * @exception  IOException  if an I/O error occurs.
1011      */
1012     public final void writeBoolean(boolean v) throws IOException {
1013         write(v ? 1 : 0);
1014         //written++;
1015     }
1016 
1017     /**
1018      * Writes a {@code byte} to the file as a one-byte value. The
1019      * write starts at the current position of the file pointer.
1020      *
1021      * @param      v   a {@code byte} value to be written.
1022      * @exception  IOException  if an I/O error occurs.
1023      */
1024     public final void writeByte(int v) throws IOException {
1025         write(v);
1026         //written++;
1027     }
1028 
1029     /**
1030      * Writes a {@code short} to the file as two bytes, high byte first.
1031      * The write starts at the current position of the file pointer.
1032      *
1033      * @param      v   a {@code short} to be written.
1034      * @exception  IOException  if an I/O error occurs.
1035      */
1036     public final void writeShort(int v) throws IOException {
1037         write((v >>> 8) & 0xFF);
1038         write((v >>> 0) & 0xFF);
1039         //written += 2;
1040     }
1041 
1042     /**
1043      * Writes a {@code char} to the file as a two-byte value, high
1044      * byte first. The write starts at the current position of the
1045      * file pointer.
1046      *
1047      * @param      v   a {@code char} value to be written.
1048      * @exception  IOException  if an I/O error occurs.
1049      */
1050     public final void writeChar(int v) throws IOException {
1051         write((v >>> 8) & 0xFF);
1052         write((v >>> 0) & 0xFF);
1053         //written += 2;
1054     }
1055 
1056     /**
1057      * Writes an {@code int} to the file as four bytes, high byte first.
1058      * The write starts at the current position of the file pointer.
1059      *
1060      * @param      v   an {@code int} to be written.
1061      * @exception  IOException  if an I/O error occurs.
1062      */
1063     public final void writeInt(int v) throws IOException {
1064         write((v >>> 24) & 0xFF);
1065         write((v >>> 16) & 0xFF);
1066         write((v >>>  8) & 0xFF);
1067         write((v >>>  0) & 0xFF);
1068         //written += 4;
1069     }
1070 
1071     /**
1072      * Writes a {@code long} to the file as eight bytes, high byte first.
1073      * The write starts at the current position of the file pointer.
1074      *
1075      * @param      v   a {@code long} to be written.
1076      * @exception  IOException  if an I/O error occurs.
1077      */
1078     public final void writeLong(long v) throws IOException {
1079         write((int)(v >>> 56) & 0xFF);
1080         write((int)(v >>> 48) & 0xFF);
1081         write((int)(v >>> 40) & 0xFF);
1082         write((int)(v >>> 32) & 0xFF);
1083         write((int)(v >>> 24) & 0xFF);
1084         write((int)(v >>> 16) & 0xFF);
1085         write((int)(v >>>  8) & 0xFF);
1086         write((int)(v >>>  0) & 0xFF);
1087         //written += 8;
1088     }
1089 
1090     /**
1091      * Converts the float argument to an {@code int} using the
1092      * {@code floatToIntBits} method in class {@code Float},
1093      * and then writes that {@code int} value to the file as a
1094      * four-byte quantity, high byte first. The write starts at the
1095      * current position of the file pointer.
1096      *
1097      * @param      v   a {@code float} value to be written.
1098      * @exception  IOException  if an I/O error occurs.
1099      * @see        java.lang.Float#floatToIntBits(float)
1100      */
1101     public final void writeFloat(float v) throws IOException {
1102         writeInt(Float.floatToIntBits(v));
1103     }
1104 
1105     /**
1106      * Converts the double argument to a {@code long} using the
1107      * {@code doubleToLongBits} method in class {@code Double},
1108      * and then writes that {@code long} value to the file as an
1109      * eight-byte quantity, high byte first. The write starts at the current
1110      * position of the file pointer.
1111      *
1112      * @param      v   a {@code double} value to be written.
1113      * @exception  IOException  if an I/O error occurs.
1114      * @see        java.lang.Double#doubleToLongBits(double)
1115      */
1116     public final void writeDouble(double v) throws IOException {
1117         writeLong(Double.doubleToLongBits(v));
1118     }
1119 
1120     /**
1121      * Writes the string to the file as a sequence of bytes. Each
1122      * character in the string is written out, in sequence, by discarding
1123      * its high eight bits. The write starts at the current position of
1124      * the file pointer.
1125      *
1126      * @param      s   a string of bytes to be written.
1127      * @exception  IOException  if an I/O error occurs.
1128      */
1129     @SuppressWarnings("deprecation")
1130     public final void writeBytes(String s) throws IOException {
1131         int len = s.length();
1132         byte[] b = new byte[len];
1133         s.getBytes(0, len, b, 0);
1134         writeBytes(b, 0, len);
1135     }
1136 
1137     /**
1138      * Writes a string to the file as a sequence of characters. Each
1139      * character is written to the data output stream as if by the
1140      * {@code writeChar} method. The write starts at the current
1141      * position of the file pointer.
1142      *
1143      * @param      s   a {@code String} value to be written.
1144      * @exception  IOException  if an I/O error occurs.
1145      * @see        java.io.RandomAccessFile#writeChar(int)
1146      */
1147     public final void writeChars(String s) throws IOException {
1148         int clen = s.length();
1149         int blen = 2*clen;
1150         byte[] b = new byte[blen];
1151         char[] c = new char[clen];
1152         s.getChars(0, clen, c, 0);
1153         for (int i = 0, j = 0; i < clen; i++) {
1154             b[j++] = (byte)(c[i] >>> 8);
1155             b[j++] = (byte)(c[i] >>> 0);
1156         }
1157         writeBytes(b, 0, blen);
1158     }
1159 
1160     /**
1161      * Writes a string to the file using
1162      * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
1163      * encoding in a machine-independent manner.
1164      * <p>
1165      * First, two bytes are written to the file, starting at the
1166      * current file pointer, as if by the
1167      * {@code writeShort} method giving the number of bytes to
1168      * follow. This value is the number of bytes actually written out,
1169      * not the length of the string. Following the length, each character
1170      * of the string is output, in sequence, using the modified UTF-8 encoding
1171      * for each character.
1172      *
1173      * @param      str   a string to be written.
1174      * @exception  IOException  if an I/O error occurs.
1175      */
1176     public final void writeUTF(String str) throws IOException {
1177         DataOutputStream.writeUTF(str, this);
1178     }
1179 
1180     private static native void initIDs();
1181 
1182     static {
1183         initIDs();
1184         SharedSecrets.setJavaIORandomAccessFileAccess(new JavaIORandomAccessFileAccess()
1185         {
1186             // This is for j.u.z.ZipFile.OPEN_DELETE. The O_TEMPORARY flag
1187             // is only implemented/supported on windows.
1188             public RandomAccessFile openAndDelete(File file, String mode)
1189                 throws IOException
1190             {
1191                 return new RandomAccessFile(file, mode, true);
1192             }
1193         });
1194     }
1195 }