1 /*
   2  * Copyright (c) 1994, 2012, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.io;
  27 
  28 import java.nio.channels.FileChannel;
  29 import sun.nio.ch.FileChannelImpl;
  30 import sun.misc.IoTrace;
  31 
  32 
  33 /**
  34  * Instances of this class support both reading and writing to a
  35  * random access file. A random access file behaves like a large
  36  * array of bytes stored in the file system. There is a kind of cursor,
  37  * or index into the implied array, called the <em>file pointer</em>;
  38  * input operations read bytes starting at the file pointer and advance
  39  * the file pointer past the bytes read. If the random access file is
  40  * created in read/write mode, then output operations are also available;
  41  * output operations write bytes starting at the file pointer and advance
  42  * the file pointer past the bytes written. Output operations that write
  43  * past the current end of the implied array cause the array to be
  44  * extended. The file pointer can be read by the
  45  * {@code getFilePointer} method and set by the {@code seek}
  46  * method.
  47  * <p>
  48  * It is generally true of all the reading routines in this class that
  49  * if end-of-file is reached before the desired number of bytes has been
  50  * read, an {@code EOFException} (which is a kind of
  51  * {@code IOException}) is thrown. If any byte cannot be read for
  52  * any reason other than end-of-file, an {@code IOException} other
  53  * than {@code EOFException} is thrown. In particular, an
  54  * {@code IOException} may be thrown if the stream has been closed.
  55  *
  56  * @author  unascribed
  57  * @since   JDK1.0
  58  */
  59 
  60 public class RandomAccessFile implements DataOutput, DataInput, Closeable {
  61 
  62     private FileDescriptor fd;
  63     private FileChannel channel = null;
  64     private boolean rw;
  65     private final String path;
  66 
  67     private Object closeLock = new Object();
  68     private volatile boolean closed = false;
  69 
  70     private static final int O_RDONLY = 1;
  71     private static final int O_RDWR =   2;
  72     private static final int O_SYNC =   4;
  73     private static final int O_DSYNC =  8;
  74 
  75     /**
  76      * Creates a random access file stream to read from, and optionally
  77      * to write to, a file with the specified name. A new
  78      * {@link FileDescriptor} object is created to represent the
  79      * connection to the file.
  80      *
  81      * <p> The <tt>mode</tt> argument specifies the access mode with which the
  82      * file is to be opened.  The permitted values and their meanings are as
  83      * specified for the <a
  84      * href="#mode"><tt>RandomAccessFile(File,String)</tt></a> constructor.
  85      *
  86      * <p>
  87      * If there is a security manager, its {@code checkRead} method
  88      * is called with the {@code name} argument
  89      * as its argument to see if read access to the file is allowed.
  90      * If the mode allows writing, the security manager's
  91      * {@code checkWrite} method
  92      * is also called with the {@code name} argument
  93      * as its argument to see if write access to the file is allowed.
  94      *
  95      * @param      name   the system-dependent filename
  96      * @param      mode   the access <a href="#mode">mode</a>
  97      * @exception  IllegalArgumentException  if the mode argument is not equal
  98      *               to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
  99      *               <tt>"rwd"</tt>
 100      * @exception FileNotFoundException
 101      *            if the mode is <tt>"r"</tt> but the given string does not
 102      *            denote an existing regular file, or if the mode begins with
 103      *            <tt>"rw"</tt> but the given string does not denote an
 104      *            existing, writable regular file and a new regular file of
 105      *            that name cannot be created, or if some other error occurs
 106      *            while opening or creating the file
 107      * @exception  SecurityException         if a security manager exists and its
 108      *               {@code checkRead} method denies read access to the file
 109      *               or the mode is "rw" and the security manager's
 110      *               {@code checkWrite} method denies write access to the file
 111      * @see        java.lang.SecurityException
 112      * @see        java.lang.SecurityManager#checkRead(java.lang.String)
 113      * @see        java.lang.SecurityManager#checkWrite(java.lang.String)
 114      * @revised 1.4
 115      * @spec JSR-51
 116      */
 117     public RandomAccessFile(String name, String mode)
 118         throws FileNotFoundException
 119     {
 120         this(name != null ? new File(name) : null, mode);
 121     }
 122 
 123     /**
 124      * Creates a random access file stream to read from, and optionally to
 125      * write to, the file specified by the {@link File} argument.  A new {@link
 126      * FileDescriptor} object is created to represent this file connection.
 127      *
 128      * <a name="mode"><p> The <tt>mode</tt> argument specifies the access mode
 129      * in which the file is to be opened.  The permitted values and their
 130      * meanings are:
 131      *
 132      * <blockquote><table summary="Access mode permitted values and meanings">
 133      * <tr><th><p align="left">Value</p></th><th><p align="left">Meaning</p></th></tr>
 134      * <tr><td valign="top"><tt>"r"</tt></td>
 135      *     <td> Open for reading only.  Invoking any of the <tt>write</tt>
 136      *     methods of the resulting object will cause an {@link
 137      *     java.io.IOException} to be thrown. </td></tr>
 138      * <tr><td valign="top"><tt>"rw"</tt></td>
 139      *     <td> Open for reading and writing.  If the file does not already
 140      *     exist then an attempt will be made to create it. </td></tr>
 141      * <tr><td valign="top"><tt>"rws"</tt></td>
 142      *     <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
 143      *     require that every update to the file's content or metadata be
 144      *     written synchronously to the underlying storage device.  </td></tr>
 145      * <tr><td valign="top"><tt>"rwd"&nbsp;&nbsp;</tt></td>
 146      *     <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
 147      *     require that every update to the file's content be written
 148      *     synchronously to the underlying storage device. </td></tr>
 149      * </table></blockquote>
 150      *
 151      * The <tt>"rws"</tt> and <tt>"rwd"</tt> modes work much like the {@link
 152      * java.nio.channels.FileChannel#force(boolean) force(boolean)} method of
 153      * the {@link java.nio.channels.FileChannel} class, passing arguments of
 154      * <tt>true</tt> and <tt>false</tt>, respectively, except that they always
 155      * apply to every I/O operation and are therefore often more efficient.  If
 156      * the file resides on a local storage device then when an invocation of a
 157      * method of this class returns it is guaranteed that all changes made to
 158      * the file by that invocation will have been written to that device.  This
 159      * is useful for ensuring that critical information is not lost in the
 160      * event of a system crash.  If the file does not reside on a local device
 161      * then no such guarantee is made.
 162      *
 163      * <p> The <tt>"rwd"</tt> mode can be used to reduce the number of I/O
 164      * operations performed.  Using <tt>"rwd"</tt> only requires updates to the
 165      * file's content to be written to storage; using <tt>"rws"</tt> requires
 166      * updates to both the file's content and its metadata to be written, which
 167      * generally requires at least one more low-level I/O operation.
 168      *
 169      * <p> If there is a security manager, its {@code checkRead} method is
 170      * called with the pathname of the {@code file} argument as its
 171      * argument to see if read access to the file is allowed.  If the mode
 172      * allows writing, the security manager's {@code checkWrite} method is
 173      * also called with the path argument to see if write access to the file is
 174      * allowed.
 175      *
 176      * @param      file   the file object
 177      * @param      mode   the access mode, as described
 178      *                    <a href="#mode">above</a>
 179      * @exception  IllegalArgumentException  if the mode argument is not equal
 180      *               to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
 181      *               <tt>"rwd"</tt>
 182      * @exception FileNotFoundException
 183      *            if the mode is <tt>"r"</tt> but the given file object does
 184      *            not denote an existing regular file, or if the mode begins
 185      *            with <tt>"rw"</tt> but the given file object does not denote
 186      *            an existing, writable regular file and a new regular file of
 187      *            that name cannot be created, or if some other error occurs
 188      *            while opening or creating the file
 189      * @exception  SecurityException         if a security manager exists and its
 190      *               {@code checkRead} method denies read access to the file
 191      *               or the mode is "rw" and the security manager's
 192      *               {@code checkWrite} method denies write access to the file
 193      * @see        java.lang.SecurityManager#checkRead(java.lang.String)
 194      * @see        java.lang.SecurityManager#checkWrite(java.lang.String)
 195      * @see        java.nio.channels.FileChannel#force(boolean)
 196      * @revised 1.4
 197      * @spec JSR-51
 198      */
 199     public RandomAccessFile(File file, String mode)
 200         throws FileNotFoundException
 201     {
 202         String name = (file != null ? file.getPath() : null);
 203         int imode = -1;
 204         if (mode.equals("r"))
 205             imode = O_RDONLY;
 206         else if (mode.startsWith("rw")) {
 207             imode = O_RDWR;
 208             rw = true;
 209             if (mode.length() > 2) {
 210                 if (mode.equals("rws"))
 211                     imode |= O_SYNC;
 212                 else if (mode.equals("rwd"))
 213                     imode |= O_DSYNC;
 214                 else
 215                     imode = -1;
 216             }
 217         }
 218         if (imode < 0)
 219             throw new IllegalArgumentException("Illegal mode \"" + mode
 220                                                + "\" must be one of "
 221                                                + "\"r\", \"rw\", \"rws\","
 222                                                + " or \"rwd\"");
 223         SecurityManager security = System.getSecurityManager();
 224         if (security != null) {
 225             security.checkRead(name);
 226             if (rw) {
 227                 security.checkWrite(name);
 228             }
 229         }
 230         if (name == null) {
 231             throw new NullPointerException();
 232         }
 233         fd = new FileDescriptor();
 234         fd.attach(this);
 235         this.path = name;
 236         open(name, imode);
 237     }
 238 
 239     /**
 240      * Returns the opaque file descriptor object associated with this
 241      * stream. </p>
 242      *
 243      * @return     the file descriptor object associated with this stream.
 244      * @exception  IOException  if an I/O error occurs.
 245      * @see        java.io.FileDescriptor
 246      */
 247     public final FileDescriptor getFD() throws IOException {
 248         if (fd != null) {
 249             return fd;
 250         }
 251         throw new IOException();
 252     }
 253 
 254     /**
 255      * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
 256      * object associated with this file.
 257      *
 258      * <p> The {@link java.nio.channels.FileChannel#position()
 259      * position} of the returned channel will always be equal to
 260      * this object's file-pointer offset as returned by the {@link
 261      * #getFilePointer getFilePointer} method.  Changing this object's
 262      * file-pointer offset, whether explicitly or by reading or writing bytes,
 263      * will change the position of the channel, and vice versa.  Changing the
 264      * file's length via this object will change the length seen via the file
 265      * channel, and vice versa.
 266      *
 267      * @return  the file channel associated with this file
 268      *
 269      * @since 1.4
 270      * @spec JSR-51
 271      */
 272     public final FileChannel getChannel() {
 273         synchronized (this) {
 274             if (channel == null) {
 275                 channel = FileChannelImpl.open(fd, path, true, rw, this);
 276             }
 277             return channel;
 278         }
 279     }
 280 
 281     /**
 282      * Opens a file and returns the file descriptor.  The file is
 283      * opened in read-write mode if the O_RDWR bit in {@code mode}
 284      * is true, else the file is opened as read-only.
 285      * If the {@code name} refers to a directory, an IOException
 286      * is thrown.
 287      *
 288      * @param name the name of the file
 289      * @param mode the mode flags, a combination of the O_ constants
 290      *             defined above
 291      */
 292     private native void open(String name, int mode)
 293         throws FileNotFoundException;
 294 
 295     // 'Read' primitives
 296 
 297     /**
 298      * Reads a byte of data from this file. The byte is returned as an
 299      * integer in the range 0 to 255 ({@code 0x00-0x0ff}). This
 300      * method blocks if no input is yet available.
 301      * <p>
 302      * Although {@code RandomAccessFile} is not a subclass of
 303      * {@code InputStream}, this method behaves in exactly the same
 304      * way as the {@link InputStream#read()} method of
 305      * {@code InputStream}.
 306      *
 307      * @return     the next byte of data, or {@code -1} if the end of the
 308      *             file has been reached.
 309      * @exception  IOException  if an I/O error occurs. Not thrown if
 310      *                          end-of-file has been reached.
 311      */
 312     public int read() throws IOException {
 313         Object traceHandle = IoTrace.fileReadBegin(path);
 314         int v = read0();
 315         IoTrace.fileReadEnd(traceHandle, v == -1 ? -1 : 1);
 316         return v;
 317     }
 318 
 319     private native int read0() throws IOException;
 320 
 321     /**
 322      * Reads a sub array as a sequence of bytes.
 323      * @param b the buffer into which the data is read.
 324      * @param off the start offset of the data.
 325      * @param len the number of bytes to read.
 326      * @exception IOException If an I/O error has occurred.
 327      */
 328     private int readBytes(byte b[], int off, int len) throws IOException {
 329         Object traceHandle = IoTrace.fileReadBegin(path);
 330         int v = readBytes0(b, off, len);
 331         IoTrace.fileReadEnd(traceHandle, v);
 332         return v;
 333     }
 334 
 335     private native int readBytes0(byte b[], int off, int len) throws IOException;
 336 
 337     /**
 338      * Reads up to {@code len} bytes of data from this file into an
 339      * array of bytes. This method blocks until at least one byte of input
 340      * is available.
 341      * <p>
 342      * Although {@code RandomAccessFile} is not a subclass of
 343      * {@code InputStream}, this method behaves in exactly the
 344      * same way as the {@link InputStream#read(byte[], int, int)} method of
 345      * {@code InputStream}.
 346      *
 347      * @param      b     the buffer into which the data is read.
 348      * @param      off   the start offset in array {@code b}
 349      *                   at which the data is written.
 350      * @param      len   the maximum number of bytes read.
 351      * @return     the total number of bytes read into the buffer, or
 352      *             {@code -1} if there is no more data because the end of
 353      *             the file has been reached.
 354      * @exception  IOException If the first byte cannot be read for any reason
 355      * other than end of file, or if the random access file has been closed, or if
 356      * some other I/O error occurs.
 357      * @exception  NullPointerException If {@code b} is {@code null}.
 358      * @exception  IndexOutOfBoundsException If {@code off} is negative,
 359      * {@code len} is negative, or {@code len} is greater than
 360      * {@code b.length - off}
 361      */
 362     public int read(byte b[], int off, int len) throws IOException {
 363         return readBytes(b, off, len);
 364     }
 365 
 366     /**
 367      * Reads up to {@code b.length} bytes of data from this file
 368      * into an array of bytes. This method blocks until at least one byte
 369      * of input is available.
 370      * <p>
 371      * Although {@code RandomAccessFile} is not a subclass of
 372      * {@code InputStream}, this method behaves in exactly the
 373      * same way as the {@link InputStream#read(byte[])} method of
 374      * {@code InputStream}.
 375      *
 376      * @param      b   the buffer into which the data is read.
 377      * @return     the total number of bytes read into the buffer, or
 378      *             {@code -1} if there is no more data because the end of
 379      *             this file has been reached.
 380      * @exception  IOException If the first byte cannot be read for any reason
 381      * other than end of file, or if the random access file has been closed, or if
 382      * some other I/O error occurs.
 383      * @exception  NullPointerException If {@code b} is {@code null}.
 384      */
 385     public int read(byte b[]) throws IOException {
 386         return readBytes(b, 0, b.length);
 387     }
 388 
 389     /**
 390      * Reads {@code b.length} bytes from this file into the byte
 391      * array, starting at the current file pointer. This method reads
 392      * repeatedly from the file until the requested number of bytes are
 393      * read. This method blocks until the requested number of bytes are
 394      * read, the end of the stream is detected, or an exception is thrown.
 395      *
 396      * @param      b   the buffer into which the data is read.
 397      * @exception  EOFException  if this file reaches the end before reading
 398      *               all the bytes.
 399      * @exception  IOException   if an I/O error occurs.
 400      */
 401     public final void readFully(byte b[]) throws IOException {
 402         readFully(b, 0, b.length);
 403     }
 404 
 405     /**
 406      * Reads exactly {@code len} bytes from this file into the byte
 407      * array, starting at the current file pointer. This method reads
 408      * repeatedly from the file until the requested number of bytes are
 409      * read. This method blocks until the requested number of bytes are
 410      * read, the end of the stream is detected, or an exception is thrown.
 411      *
 412      * @param      b     the buffer into which the data is read.
 413      * @param      off   the start offset of the data.
 414      * @param      len   the number of bytes to read.
 415      * @exception  EOFException  if this file reaches the end before reading
 416      *               all the bytes.
 417      * @exception  IOException   if an I/O error occurs.
 418      */
 419     public final void readFully(byte b[], int off, int len) throws IOException {
 420         int n = 0;
 421         do {
 422             int count = this.read(b, off + n, len - n);
 423             if (count < 0)
 424                 throw new EOFException();
 425             n += count;
 426         } while (n < len);
 427     }
 428 
 429     /**
 430      * Attempts to skip over {@code n} bytes of input discarding the
 431      * skipped bytes.
 432      * <p>
 433      *
 434      * This method may skip over some smaller number of bytes, possibly zero.
 435      * This may result from any of a number of conditions; reaching end of
 436      * file before {@code n} bytes have been skipped is only one
 437      * possibility. This method never throws an {@code EOFException}.
 438      * The actual number of bytes skipped is returned.  If {@code n}
 439      * is negative, no bytes are skipped.
 440      *
 441      * @param      n   the number of bytes to be skipped.
 442      * @return     the actual number of bytes skipped.
 443      * @exception  IOException  if an I/O error occurs.
 444      */
 445     public int skipBytes(int n) throws IOException {
 446         long pos;
 447         long len;
 448         long newpos;
 449 
 450         if (n <= 0) {
 451             return 0;
 452         }
 453         pos = getFilePointer();
 454         len = length();
 455         newpos = pos + n;
 456         if (newpos > len) {
 457             newpos = len;
 458         }
 459         seek(newpos);
 460 
 461         /* return the actual number of bytes skipped */
 462         return (int) (newpos - pos);
 463     }
 464 
 465     // 'Write' primitives
 466 
 467     /**
 468      * Writes the specified byte to this file. The write starts at
 469      * the current file pointer.
 470      *
 471      * @param      b   the {@code byte} to be written.
 472      * @exception  IOException  if an I/O error occurs.
 473      */
 474     public void write(int b) throws IOException {
 475         Object traceHandle = IoTrace.fileWriteBegin(path);
 476         write0(b);
 477         IoTrace.fileWriteEnd(traceHandle, 1);
 478     }
 479 
 480     private native void write0(int b) throws IOException;
 481 
 482     /**
 483      * Writes a sub array as a sequence of bytes.
 484      * @param b the data to be written
 485      * @param off the start offset in the data
 486      * @param len the number of bytes that are written
 487      * @exception IOException If an I/O error has occurred.
 488      */
 489     private void writeBytes(byte b[], int off, int len) throws IOException {
 490         Object traceHandle = IoTrace.fileWriteBegin(path);
 491         writeBytes0(b, off, len);
 492         IoTrace.fileWriteEnd(traceHandle, len);
 493     }
 494 
 495     private native void writeBytes0(byte b[], int off, int len) throws IOException;
 496 
 497     /**
 498      * Writes {@code b.length} bytes from the specified byte array
 499      * to this file, starting at the current file pointer.
 500      *
 501      * @param      b   the data.
 502      * @exception  IOException  if an I/O error occurs.
 503      */
 504     public void write(byte b[]) throws IOException {
 505         writeBytes(b, 0, b.length);
 506     }
 507 
 508     /**
 509      * Writes {@code len} bytes from the specified byte array
 510      * starting at offset {@code off} to this file.
 511      *
 512      * @param      b     the data.
 513      * @param      off   the start offset in the data.
 514      * @param      len   the number of bytes to write.
 515      * @exception  IOException  if an I/O error occurs.
 516      */
 517     public void write(byte b[], int off, int len) throws IOException {
 518         writeBytes(b, off, len);
 519     }
 520 
 521     // 'Random access' stuff
 522 
 523     /**
 524      * Returns the current offset in this file.
 525      *
 526      * @return     the offset from the beginning of the file, in bytes,
 527      *             at which the next read or write occurs.
 528      * @exception  IOException  if an I/O error occurs.
 529      */
 530     public native long getFilePointer() throws IOException;
 531 
 532     /**
 533      * Sets the file-pointer offset, measured from the beginning of this
 534      * file, at which the next read or write occurs.  The offset may be
 535      * set beyond the end of the file. Setting the offset beyond the end
 536      * of the file does not change the file length.  The file length will
 537      * change only by writing after the offset has been set beyond the end
 538      * of the file.
 539      *
 540      * @param      pos   the offset position, measured in bytes from the
 541      *                   beginning of the file, at which to set the file
 542      *                   pointer.
 543      * @exception  IOException  if {@code pos} is less than
 544      *                          {@code 0} or if an I/O error occurs.
 545      */
 546     public native void seek(long pos) throws IOException;
 547 
 548     /**
 549      * Returns the length of this file.
 550      *
 551      * @return     the length of this file, measured in bytes.
 552      * @exception  IOException  if an I/O error occurs.
 553      */
 554     public native long length() throws IOException;
 555 
 556     /**
 557      * Sets the length of this file.
 558      *
 559      * <p> If the present length of the file as returned by the
 560      * {@code length} method is greater than the {@code newLength}
 561      * argument then the file will be truncated.  In this case, if the file
 562      * offset as returned by the {@code getFilePointer} method is greater
 563      * than {@code newLength} then after this method returns the offset
 564      * will be equal to {@code newLength}.
 565      *
 566      * <p> If the present length of the file as returned by the
 567      * {@code length} method is smaller than the {@code newLength}
 568      * argument then the file will be extended.  In this case, the contents of
 569      * the extended portion of the file are not defined.
 570      *
 571      * @param      newLength    The desired length of the file
 572      * @exception  IOException  If an I/O error occurs
 573      * @since      1.2
 574      */
 575     public native void setLength(long newLength) throws IOException;
 576 
 577     /**
 578      * Closes this random access file stream and releases any system
 579      * resources associated with the stream. A closed random access
 580      * file cannot perform input or output operations and cannot be
 581      * reopened.
 582      *
 583      * <p> If this file has an associated channel then the channel is closed
 584      * as well.
 585      *
 586      * @exception  IOException  if an I/O error occurs.
 587      *
 588      * @revised 1.4
 589      * @spec JSR-51
 590      */
 591     public void close() throws IOException {
 592         synchronized (closeLock) {
 593             if (closed) {
 594                 return;
 595             }
 596             closed = true;
 597         }
 598         if (channel != null) {
 599             channel.close();
 600         }
 601 
 602         fd.closeAll(new Closeable() {
 603             public void close() throws IOException {
 604                close0();
 605            }
 606         });
 607     }
 608 
 609     //
 610     //  Some "reading/writing Java data types" methods stolen from
 611     //  DataInputStream and DataOutputStream.
 612     //
 613 
 614     /**
 615      * Reads a {@code boolean} from this file. This method reads a
 616      * single byte from the file, starting at the current file pointer.
 617      * A value of {@code 0} represents
 618      * {@code false}. Any other value represents {@code true}.
 619      * This method blocks until the byte is read, the end of the stream
 620      * is detected, or an exception is thrown.
 621      *
 622      * @return     the {@code boolean} value read.
 623      * @exception  EOFException  if this file has reached the end.
 624      * @exception  IOException   if an I/O error occurs.
 625      */
 626     public final boolean readBoolean() throws IOException {
 627         int ch = this.read();
 628         if (ch < 0)
 629             throw new EOFException();
 630         return (ch != 0);
 631     }
 632 
 633     /**
 634      * Reads a signed eight-bit value from this file. This method reads a
 635      * byte from the file, starting from the current file pointer.
 636      * If the byte read is {@code b}, where
 637      * <code>0&nbsp;&lt;=&nbsp;b&nbsp;&lt;=&nbsp;255</code>,
 638      * then the result is:
 639      * <blockquote><pre>
 640      *     (byte)(b)
 641      * </pre></blockquote>
 642      * <p>
 643      * This method blocks until the byte is read, the end of the stream
 644      * is detected, or an exception is thrown.
 645      *
 646      * @return     the next byte of this file as a signed eight-bit
 647      *             {@code byte}.
 648      * @exception  EOFException  if this file has reached the end.
 649      * @exception  IOException   if an I/O error occurs.
 650      */
 651     public final byte readByte() throws IOException {
 652         int ch = this.read();
 653         if (ch < 0)
 654             throw new EOFException();
 655         return (byte)(ch);
 656     }
 657 
 658     /**
 659      * Reads an unsigned eight-bit number from this file. This method reads
 660      * a byte from this file, starting at the current file pointer,
 661      * and returns that byte.
 662      * <p>
 663      * This method blocks until the byte is read, the end of the stream
 664      * is detected, or an exception is thrown.
 665      *
 666      * @return     the next byte of this file, interpreted as an unsigned
 667      *             eight-bit number.
 668      * @exception  EOFException  if this file has reached the end.
 669      * @exception  IOException   if an I/O error occurs.
 670      */
 671     public final int readUnsignedByte() throws IOException {
 672         int ch = this.read();
 673         if (ch < 0)
 674             throw new EOFException();
 675         return ch;
 676     }
 677 
 678     /**
 679      * Reads a signed 16-bit number from this file. The method reads two
 680      * bytes from this file, starting at the current file pointer.
 681      * If the two bytes read, in order, are
 682      * {@code b1} and {@code b2}, where each of the two values is
 683      * between {@code 0} and {@code 255}, inclusive, then the
 684      * result is equal to:
 685      * <blockquote><pre>
 686      *     (short)((b1 &lt;&lt; 8) | b2)
 687      * </pre></blockquote>
 688      * <p>
 689      * This method blocks until the two bytes are read, the end of the
 690      * stream is detected, or an exception is thrown.
 691      *
 692      * @return     the next two bytes of this file, interpreted as a signed
 693      *             16-bit number.
 694      * @exception  EOFException  if this file reaches the end before reading
 695      *               two bytes.
 696      * @exception  IOException   if an I/O error occurs.
 697      */
 698     public final short readShort() throws IOException {
 699         int ch1 = this.read();
 700         int ch2 = this.read();
 701         if ((ch1 | ch2) < 0)
 702             throw new EOFException();
 703         return (short)((ch1 << 8) + (ch2 << 0));
 704     }
 705 
 706     /**
 707      * Reads an unsigned 16-bit number from this file. This method reads
 708      * two bytes from the file, starting at the current file pointer.
 709      * If the bytes read, in order, are
 710      * {@code b1} and {@code b2}, where
 711      * <code>0&nbsp;&lt;=&nbsp;b1, b2&nbsp;&lt;=&nbsp;255</code>,
 712      * then the result is equal to:
 713      * <blockquote><pre>
 714      *     (b1 &lt;&lt; 8) | b2
 715      * </pre></blockquote>
 716      * <p>
 717      * This method blocks until the two bytes are read, the end of the
 718      * stream is detected, or an exception is thrown.
 719      *
 720      * @return     the next two bytes of this file, interpreted as an unsigned
 721      *             16-bit integer.
 722      * @exception  EOFException  if this file reaches the end before reading
 723      *               two bytes.
 724      * @exception  IOException   if an I/O error occurs.
 725      */
 726     public final int readUnsignedShort() throws IOException {
 727         int ch1 = this.read();
 728         int ch2 = this.read();
 729         if ((ch1 | ch2) < 0)
 730             throw new EOFException();
 731         return (ch1 << 8) + (ch2 << 0);
 732     }
 733 
 734     /**
 735      * Reads a character from this file. This method reads two
 736      * bytes from the file, starting at the current file pointer.
 737      * If the bytes read, in order, are
 738      * {@code b1} and {@code b2}, where
 739      * <code>0&nbsp;&lt;=&nbsp;b1,&nbsp;b2&nbsp;&lt;=&nbsp;255</code>,
 740      * then the result is equal to:
 741      * <blockquote><pre>
 742      *     (char)((b1 &lt;&lt; 8) | b2)
 743      * </pre></blockquote>
 744      * <p>
 745      * This method blocks until the two bytes are read, the end of the
 746      * stream is detected, or an exception is thrown.
 747      *
 748      * @return     the next two bytes of this file, interpreted as a
 749      *                  {@code char}.
 750      * @exception  EOFException  if this file reaches the end before reading
 751      *               two bytes.
 752      * @exception  IOException   if an I/O error occurs.
 753      */
 754     public final char readChar() throws IOException {
 755         int ch1 = this.read();
 756         int ch2 = this.read();
 757         if ((ch1 | ch2) < 0)
 758             throw new EOFException();
 759         return (char)((ch1 << 8) + (ch2 << 0));
 760     }
 761 
 762     /**
 763      * Reads a signed 32-bit integer from this file. This method reads 4
 764      * bytes from the file, starting at the current file pointer.
 765      * If the bytes read, in order, are {@code b1},
 766      * {@code b2}, {@code b3}, and {@code b4}, where
 767      * <code>0&nbsp;&lt;=&nbsp;b1, b2, b3, b4&nbsp;&lt;=&nbsp;255</code>,
 768      * then the result is equal to:
 769      * <blockquote><pre>
 770      *     (b1 &lt;&lt; 24) | (b2 &lt;&lt; 16) + (b3 &lt;&lt; 8) + b4
 771      * </pre></blockquote>
 772      * <p>
 773      * This method blocks until the four bytes are read, the end of the
 774      * stream is detected, or an exception is thrown.
 775      *
 776      * @return     the next four bytes of this file, interpreted as an
 777      *             {@code int}.
 778      * @exception  EOFException  if this file reaches the end before reading
 779      *               four bytes.
 780      * @exception  IOException   if an I/O error occurs.
 781      */
 782     public final int readInt() throws IOException {
 783         int ch1 = this.read();
 784         int ch2 = this.read();
 785         int ch3 = this.read();
 786         int ch4 = this.read();
 787         if ((ch1 | ch2 | ch3 | ch4) < 0)
 788             throw new EOFException();
 789         return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
 790     }
 791 
 792     /**
 793      * Reads a signed 64-bit integer from this file. This method reads eight
 794      * bytes from the file, starting at the current file pointer.
 795      * If the bytes read, in order, are
 796      * {@code b1}, {@code b2}, {@code b3},
 797      * {@code b4}, {@code b5}, {@code b6},
 798      * {@code b7}, and {@code b8,} where:
 799      * <blockquote><pre>
 800      *     0 &lt;= b1, b2, b3, b4, b5, b6, b7, b8 &lt;=255,
 801      * </pre></blockquote>
 802      * <p>
 803      * then the result is equal to:
 804      * <p><blockquote><pre>
 805      *     ((long)b1 &lt;&lt; 56) + ((long)b2 &lt;&lt; 48)
 806      *     + ((long)b3 &lt;&lt; 40) + ((long)b4 &lt;&lt; 32)
 807      *     + ((long)b5 &lt;&lt; 24) + ((long)b6 &lt;&lt; 16)
 808      *     + ((long)b7 &lt;&lt; 8) + b8
 809      * </pre></blockquote>
 810      * <p>
 811      * This method blocks until the eight bytes are read, the end of the
 812      * stream is detected, or an exception is thrown.
 813      *
 814      * @return     the next eight bytes of this file, interpreted as a
 815      *             {@code long}.
 816      * @exception  EOFException  if this file reaches the end before reading
 817      *               eight bytes.
 818      * @exception  IOException   if an I/O error occurs.
 819      */
 820     public final long readLong() throws IOException {
 821         return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
 822     }
 823 
 824     /**
 825      * Reads a {@code float} from this file. This method reads an
 826      * {@code int} value, starting at the current file pointer,
 827      * as if by the {@code readInt} method
 828      * and then converts that {@code int} to a {@code float}
 829      * using the {@code intBitsToFloat} method in class
 830      * {@code Float}.
 831      * <p>
 832      * This method blocks until the four bytes are read, the end of the
 833      * stream is detected, or an exception is thrown.
 834      *
 835      * @return     the next four bytes of this file, interpreted as a
 836      *             {@code float}.
 837      * @exception  EOFException  if this file reaches the end before reading
 838      *             four bytes.
 839      * @exception  IOException   if an I/O error occurs.
 840      * @see        java.io.RandomAccessFile#readInt()
 841      * @see        java.lang.Float#intBitsToFloat(int)
 842      */
 843     public final float readFloat() throws IOException {
 844         return Float.intBitsToFloat(readInt());
 845     }
 846 
 847     /**
 848      * Reads a {@code double} from this file. This method reads a
 849      * {@code long} value, starting at the current file pointer,
 850      * as if by the {@code readLong} method
 851      * and then converts that {@code long} to a {@code double}
 852      * using the {@code longBitsToDouble} method in
 853      * class {@code Double}.
 854      * <p>
 855      * This method blocks until the eight bytes are read, the end of the
 856      * stream is detected, or an exception is thrown.
 857      *
 858      * @return     the next eight bytes of this file, interpreted as a
 859      *             {@code double}.
 860      * @exception  EOFException  if this file reaches the end before reading
 861      *             eight bytes.
 862      * @exception  IOException   if an I/O error occurs.
 863      * @see        java.io.RandomAccessFile#readLong()
 864      * @see        java.lang.Double#longBitsToDouble(long)
 865      */
 866     public final double readDouble() throws IOException {
 867         return Double.longBitsToDouble(readLong());
 868     }
 869 
 870     /**
 871      * Reads the next line of text from this file.  This method successively
 872      * reads bytes from the file, starting at the current file pointer,
 873      * until it reaches a line terminator or the end
 874      * of the file.  Each byte is converted into a character by taking the
 875      * byte's value for the lower eight bits of the character and setting the
 876      * high eight bits of the character to zero.  This method does not,
 877      * therefore, support the full Unicode character set.
 878      *
 879      * <p> A line of text is terminated by a carriage-return character
 880      * ({@code '\u005Cr'}), a newline character ({@code '\u005Cn'}), a
 881      * carriage-return character immediately followed by a newline character,
 882      * or the end of the file.  Line-terminating characters are discarded and
 883      * are not included as part of the string returned.
 884      *
 885      * <p> This method blocks until a newline character is read, a carriage
 886      * return and the byte following it are read (to see if it is a newline),
 887      * the end of the file is reached, or an exception is thrown.
 888      *
 889      * @return     the next line of text from this file, or null if end
 890      *             of file is encountered before even one byte is read.
 891      * @exception  IOException  if an I/O error occurs.
 892      */
 893 
 894     public final String readLine() throws IOException {
 895         StringBuffer input = new StringBuffer();
 896         int c = -1;
 897         boolean eol = false;
 898 
 899         while (!eol) {
 900             switch (c = read()) {
 901             case -1:
 902             case '\n':
 903                 eol = true;
 904                 break;
 905             case '\r':
 906                 eol = true;
 907                 long cur = getFilePointer();
 908                 if ((read()) != '\n') {
 909                     seek(cur);
 910                 }
 911                 break;
 912             default:
 913                 input.append((char)c);
 914                 break;
 915             }
 916         }
 917 
 918         if ((c == -1) && (input.length() == 0)) {
 919             return null;
 920         }
 921         return input.toString();
 922     }
 923 
 924     /**
 925      * Reads in a string from this file. The string has been encoded
 926      * using a
 927      * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
 928      * format.
 929      * <p>
 930      * The first two bytes are read, starting from the current file
 931      * pointer, as if by
 932      * {@code readUnsignedShort}. This value gives the number of
 933      * following bytes that are in the encoded string, not
 934      * the length of the resulting string. The following bytes are then
 935      * interpreted as bytes encoding characters in the modified UTF-8 format
 936      * and are converted into characters.
 937      * <p>
 938      * This method blocks until all the bytes are read, the end of the
 939      * stream is detected, or an exception is thrown.
 940      *
 941      * @return     a Unicode string.
 942      * @exception  EOFException            if this file reaches the end before
 943      *               reading all the bytes.
 944      * @exception  IOException             if an I/O error occurs.
 945      * @exception  UTFDataFormatException  if the bytes do not represent
 946      *               valid modified UTF-8 encoding of a Unicode string.
 947      * @see        java.io.RandomAccessFile#readUnsignedShort()
 948      */
 949     public final String readUTF() throws IOException {
 950         return DataInputStream.readUTF(this);
 951     }
 952 
 953     /**
 954      * Writes a {@code boolean} to the file as a one-byte value. The
 955      * value {@code true} is written out as the value
 956      * {@code (byte)1}; the value {@code false} is written out
 957      * as the value {@code (byte)0}. The write starts at
 958      * the current position of the file pointer.
 959      *
 960      * @param      v   a {@code boolean} value to be written.
 961      * @exception  IOException  if an I/O error occurs.
 962      */
 963     public final void writeBoolean(boolean v) throws IOException {
 964         write(v ? 1 : 0);
 965         //written++;
 966     }
 967 
 968     /**
 969      * Writes a {@code byte} to the file as a one-byte value. The
 970      * write starts at the current position of the file pointer.
 971      *
 972      * @param      v   a {@code byte} value to be written.
 973      * @exception  IOException  if an I/O error occurs.
 974      */
 975     public final void writeByte(int v) throws IOException {
 976         write(v);
 977         //written++;
 978     }
 979 
 980     /**
 981      * Writes a {@code short} to the file as two bytes, high byte first.
 982      * The write starts at the current position of the file pointer.
 983      *
 984      * @param      v   a {@code short} to be written.
 985      * @exception  IOException  if an I/O error occurs.
 986      */
 987     public final void writeShort(int v) throws IOException {
 988         write((v >>> 8) & 0xFF);
 989         write((v >>> 0) & 0xFF);
 990         //written += 2;
 991     }
 992 
 993     /**
 994      * Writes a {@code char} to the file as a two-byte value, high
 995      * byte first. The write starts at the current position of the
 996      * file pointer.
 997      *
 998      * @param      v   a {@code char} value to be written.
 999      * @exception  IOException  if an I/O error occurs.
1000      */
1001     public final void writeChar(int v) throws IOException {
1002         write((v >>> 8) & 0xFF);
1003         write((v >>> 0) & 0xFF);
1004         //written += 2;
1005     }
1006 
1007     /**
1008      * Writes an {@code int} to the file as four bytes, high byte first.
1009      * The write starts at the current position of the file pointer.
1010      *
1011      * @param      v   an {@code int} to be written.
1012      * @exception  IOException  if an I/O error occurs.
1013      */
1014     public final void writeInt(int v) throws IOException {
1015         write((v >>> 24) & 0xFF);
1016         write((v >>> 16) & 0xFF);
1017         write((v >>>  8) & 0xFF);
1018         write((v >>>  0) & 0xFF);
1019         //written += 4;
1020     }
1021 
1022     /**
1023      * Writes a {@code long} to the file as eight bytes, high byte first.
1024      * The write starts at the current position of the file pointer.
1025      *
1026      * @param      v   a {@code long} to be written.
1027      * @exception  IOException  if an I/O error occurs.
1028      */
1029     public final void writeLong(long v) throws IOException {
1030         write((int)(v >>> 56) & 0xFF);
1031         write((int)(v >>> 48) & 0xFF);
1032         write((int)(v >>> 40) & 0xFF);
1033         write((int)(v >>> 32) & 0xFF);
1034         write((int)(v >>> 24) & 0xFF);
1035         write((int)(v >>> 16) & 0xFF);
1036         write((int)(v >>>  8) & 0xFF);
1037         write((int)(v >>>  0) & 0xFF);
1038         //written += 8;
1039     }
1040 
1041     /**
1042      * Converts the float argument to an {@code int} using the
1043      * {@code floatToIntBits} method in class {@code Float},
1044      * and then writes that {@code int} value to the file as a
1045      * four-byte quantity, high byte first. The write starts at the
1046      * current position of the file pointer.
1047      *
1048      * @param      v   a {@code float} value to be written.
1049      * @exception  IOException  if an I/O error occurs.
1050      * @see        java.lang.Float#floatToIntBits(float)
1051      */
1052     public final void writeFloat(float v) throws IOException {
1053         writeInt(Float.floatToIntBits(v));
1054     }
1055 
1056     /**
1057      * Converts the double argument to a {@code long} using the
1058      * {@code doubleToLongBits} method in class {@code Double},
1059      * and then writes that {@code long} value to the file as an
1060      * eight-byte quantity, high byte first. The write starts at the current
1061      * position of the file pointer.
1062      *
1063      * @param      v   a {@code double} value to be written.
1064      * @exception  IOException  if an I/O error occurs.
1065      * @see        java.lang.Double#doubleToLongBits(double)
1066      */
1067     public final void writeDouble(double v) throws IOException {
1068         writeLong(Double.doubleToLongBits(v));
1069     }
1070 
1071     /**
1072      * Writes the string to the file as a sequence of bytes. Each
1073      * character in the string is written out, in sequence, by discarding
1074      * its high eight bits. The write starts at the current position of
1075      * the file pointer.
1076      *
1077      * @param      s   a string of bytes to be written.
1078      * @exception  IOException  if an I/O error occurs.
1079      */
1080     @SuppressWarnings("deprecation")
1081     public final void writeBytes(String s) throws IOException {
1082         int len = s.length();
1083         byte[] b = new byte[len];
1084         s.getBytes(0, len, b, 0);
1085         writeBytes(b, 0, len);
1086     }
1087 
1088     /**
1089      * Writes a string to the file as a sequence of characters. Each
1090      * character is written to the data output stream as if by the
1091      * {@code writeChar} method. The write starts at the current
1092      * position of the file pointer.
1093      *
1094      * @param      s   a {@code String} value to be written.
1095      * @exception  IOException  if an I/O error occurs.
1096      * @see        java.io.RandomAccessFile#writeChar(int)
1097      */
1098     public final void writeChars(String s) throws IOException {
1099         int clen = s.length();
1100         int blen = 2*clen;
1101         byte[] b = new byte[blen];
1102         char[] c = new char[clen];
1103         s.getChars(0, clen, c, 0);
1104         for (int i = 0, j = 0; i < clen; i++) {
1105             b[j++] = (byte)(c[i] >>> 8);
1106             b[j++] = (byte)(c[i] >>> 0);
1107         }
1108         writeBytes(b, 0, blen);
1109     }
1110 
1111     /**
1112      * Writes a string to the file using
1113      * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
1114      * encoding in a machine-independent manner.
1115      * <p>
1116      * First, two bytes are written to the file, starting at the
1117      * current file pointer, as if by the
1118      * {@code writeShort} method giving the number of bytes to
1119      * follow. This value is the number of bytes actually written out,
1120      * not the length of the string. Following the length, each character
1121      * of the string is output, in sequence, using the modified UTF-8 encoding
1122      * for each character.
1123      *
1124      * @param      str   a string to be written.
1125      * @exception  IOException  if an I/O error occurs.
1126      */
1127     public final void writeUTF(String str) throws IOException {
1128         DataOutputStream.writeUTF(str, this);
1129     }
1130 
1131     private static native void initIDs();
1132 
1133     private native void close0() throws IOException;
1134 
1135     static {
1136         initIDs();
1137     }
1138 }