rev 6099 : [mq]: io-trace

   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 
  31 
  32 /**
  33  * Instances of this class support both reading and writing to a
  34  * random access file. A random access file behaves like a large
  35  * array of bytes stored in the file system. There is a kind of cursor,
  36  * or index into the implied array, called the <em>file pointer</em>;
  37  * input operations read bytes starting at the file pointer and advance
  38  * the file pointer past the bytes read. If the random access file is
  39  * created in read/write mode, then output operations are also available;
  40  * output operations write bytes starting at the file pointer and advance
  41  * the file pointer past the bytes written. Output operations that write
  42  * past the current end of the implied array cause the array to be
  43  * extended. The file pointer can be read by the
  44  * {@code getFilePointer} method and set by the {@code seek}
  45  * method.
  46  * <p>
  47  * It is generally true of all the reading routines in this class that
  48  * if end-of-file is reached before the desired number of bytes has been
  49  * read, an {@code EOFException} (which is a kind of
  50  * {@code IOException}) is thrown. If any byte cannot be read for
  51  * any reason other than end-of-file, an {@code IOException} other
  52  * than {@code EOFException} is thrown. In particular, an
  53  * {@code IOException} may be thrown if the stream has been closed.
  54  *
  55  * @author  unascribed
  56  * @since   JDK1.0
  57  */
  58 
  59 public class RandomAccessFile implements DataOutput, DataInput, Closeable {
  60 
  61     private FileDescriptor fd;
  62     private FileChannel channel = null;
  63     private boolean rw;

  64 
  65     private Object closeLock = new Object();
  66     private volatile boolean closed = false;
  67 
  68     private static final int O_RDONLY = 1;
  69     private static final int O_RDWR =   2;
  70     private static final int O_SYNC =   4;
  71     private static final int O_DSYNC =  8;
  72 
  73     /**
  74      * Creates a random access file stream to read from, and optionally
  75      * to write to, a file with the specified name. A new
  76      * {@link FileDescriptor} object is created to represent the
  77      * connection to the file.
  78      *
  79      * <p> The <tt>mode</tt> argument specifies the access mode with which the
  80      * file is to be opened.  The permitted values and their meanings are as
  81      * specified for the <a
  82      * href="#mode"><tt>RandomAccessFile(File,String)</tt></a> constructor.
  83      *
  84      * <p>
  85      * If there is a security manager, its {@code checkRead} method
  86      * is called with the {@code name} argument
  87      * as its argument to see if read access to the file is allowed.
  88      * If the mode allows writing, the security manager's
  89      * {@code checkWrite} method
  90      * is also called with the {@code name} argument
  91      * as its argument to see if write access to the file is allowed.
  92      *
  93      * @param      name   the system-dependent filename
  94      * @param      mode   the access <a href="#mode">mode</a>
  95      * @exception  IllegalArgumentException  if the mode argument is not equal
  96      *               to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
  97      *               <tt>"rwd"</tt>
  98      * @exception FileNotFoundException
  99      *            if the mode is <tt>"r"</tt> but the given string does not
 100      *            denote an existing regular file, or if the mode begins with
 101      *            <tt>"rw"</tt> but the given string does not denote an
 102      *            existing, writable regular file and a new regular file of
 103      *            that name cannot be created, or if some other error occurs
 104      *            while opening or creating the file
 105      * @exception  SecurityException         if a security manager exists and its
 106      *               {@code checkRead} method denies read access to the file
 107      *               or the mode is "rw" and the security manager's
 108      *               {@code checkWrite} method denies write access to the file
 109      * @see        java.lang.SecurityException
 110      * @see        java.lang.SecurityManager#checkRead(java.lang.String)
 111      * @see        java.lang.SecurityManager#checkWrite(java.lang.String)
 112      * @revised 1.4
 113      * @spec JSR-51
 114      */
 115     public RandomAccessFile(String name, String mode)
 116         throws FileNotFoundException
 117     {
 118         this(name != null ? new File(name) : null, mode);
 119     }
 120 
 121     /**
 122      * Creates a random access file stream to read from, and optionally to
 123      * write to, the file specified by the {@link File} argument.  A new {@link
 124      * FileDescriptor} object is created to represent this file connection.
 125      *
 126      * <a name="mode"><p> The <tt>mode</tt> argument specifies the access mode
 127      * in which the file is to be opened.  The permitted values and their
 128      * meanings are:
 129      *
 130      * <blockquote><table summary="Access mode permitted values and meanings">
 131      * <tr><th><p align="left">Value</p></th><th><p align="left">Meaning</p></th></tr>
 132      * <tr><td valign="top"><tt>"r"</tt></td>
 133      *     <td> Open for reading only.  Invoking any of the <tt>write</tt>
 134      *     methods of the resulting object will cause an {@link
 135      *     java.io.IOException} to be thrown. </td></tr>
 136      * <tr><td valign="top"><tt>"rw"</tt></td>
 137      *     <td> Open for reading and writing.  If the file does not already
 138      *     exist then an attempt will be made to create it. </td></tr>
 139      * <tr><td valign="top"><tt>"rws"</tt></td>
 140      *     <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
 141      *     require that every update to the file's content or metadata be
 142      *     written synchronously to the underlying storage device.  </td></tr>
 143      * <tr><td valign="top"><tt>"rwd"&nbsp;&nbsp;</tt></td>
 144      *     <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
 145      *     require that every update to the file's content be written
 146      *     synchronously to the underlying storage device. </td></tr>
 147      * </table></blockquote>
 148      *
 149      * The <tt>"rws"</tt> and <tt>"rwd"</tt> modes work much like the {@link
 150      * java.nio.channels.FileChannel#force(boolean) force(boolean)} method of
 151      * the {@link java.nio.channels.FileChannel} class, passing arguments of
 152      * <tt>true</tt> and <tt>false</tt>, respectively, except that they always
 153      * apply to every I/O operation and are therefore often more efficient.  If
 154      * the file resides on a local storage device then when an invocation of a
 155      * method of this class returns it is guaranteed that all changes made to
 156      * the file by that invocation will have been written to that device.  This
 157      * is useful for ensuring that critical information is not lost in the
 158      * event of a system crash.  If the file does not reside on a local device
 159      * then no such guarantee is made.
 160      *
 161      * <p> The <tt>"rwd"</tt> mode can be used to reduce the number of I/O
 162      * operations performed.  Using <tt>"rwd"</tt> only requires updates to the
 163      * file's content to be written to storage; using <tt>"rws"</tt> requires
 164      * updates to both the file's content and its metadata to be written, which
 165      * generally requires at least one more low-level I/O operation.
 166      *
 167      * <p> If there is a security manager, its {@code checkRead} method is
 168      * called with the pathname of the {@code file} argument as its
 169      * argument to see if read access to the file is allowed.  If the mode
 170      * allows writing, the security manager's {@code checkWrite} method is
 171      * also called with the path argument to see if write access to the file is
 172      * allowed.
 173      *
 174      * @param      file   the file object
 175      * @param      mode   the access mode, as described
 176      *                    <a href="#mode">above</a>
 177      * @exception  IllegalArgumentException  if the mode argument is not equal
 178      *               to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
 179      *               <tt>"rwd"</tt>
 180      * @exception FileNotFoundException
 181      *            if the mode is <tt>"r"</tt> but the given file object does
 182      *            not denote an existing regular file, or if the mode begins
 183      *            with <tt>"rw"</tt> but the given file object does not denote
 184      *            an existing, writable regular file and a new regular file of
 185      *            that name cannot be created, or if some other error occurs
 186      *            while opening or creating the file
 187      * @exception  SecurityException         if a security manager exists and its
 188      *               {@code checkRead} method denies read access to the file
 189      *               or the mode is "rw" and the security manager's
 190      *               {@code checkWrite} method denies write access to the file
 191      * @see        java.lang.SecurityManager#checkRead(java.lang.String)
 192      * @see        java.lang.SecurityManager#checkWrite(java.lang.String)
 193      * @see        java.nio.channels.FileChannel#force(boolean)
 194      * @revised 1.4
 195      * @spec JSR-51
 196      */
 197     public RandomAccessFile(File file, String mode)
 198         throws FileNotFoundException
 199     {
 200         String name = (file != null ? file.getPath() : null);
 201         int imode = -1;
 202         if (mode.equals("r"))
 203             imode = O_RDONLY;
 204         else if (mode.startsWith("rw")) {
 205             imode = O_RDWR;
 206             rw = true;
 207             if (mode.length() > 2) {
 208                 if (mode.equals("rws"))
 209                     imode |= O_SYNC;
 210                 else if (mode.equals("rwd"))
 211                     imode |= O_DSYNC;
 212                 else
 213                     imode = -1;
 214             }
 215         }
 216         if (imode < 0)
 217             throw new IllegalArgumentException("Illegal mode \"" + mode
 218                                                + "\" must be one of "
 219                                                + "\"r\", \"rw\", \"rws\","
 220                                                + " or \"rwd\"");
 221         SecurityManager security = System.getSecurityManager();
 222         if (security != null) {
 223             security.checkRead(name);
 224             if (rw) {
 225                 security.checkWrite(name);
 226             }
 227         }
 228         if (name == null) {
 229             throw new NullPointerException();
 230         }
 231         fd = new FileDescriptor();
 232         fd.attach(this);

 233         open(name, imode);
 234     }
 235 
 236     /**
 237      * Returns the opaque file descriptor object associated with this
 238      * stream. </p>
 239      *
 240      * @return     the file descriptor object associated with this stream.
 241      * @exception  IOException  if an I/O error occurs.
 242      * @see        java.io.FileDescriptor
 243      */
 244     public final FileDescriptor getFD() throws IOException {
 245         if (fd != null) {
 246             return fd;
 247         }
 248         throw new IOException();
 249     }
 250 
 251     /**
 252      * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
 253      * object associated with this file.
 254      *
 255      * <p> The {@link java.nio.channels.FileChannel#position()
 256      * position} of the returned channel will always be equal to
 257      * this object's file-pointer offset as returned by the {@link
 258      * #getFilePointer getFilePointer} method.  Changing this object's
 259      * file-pointer offset, whether explicitly or by reading or writing bytes,
 260      * will change the position of the channel, and vice versa.  Changing the
 261      * file's length via this object will change the length seen via the file
 262      * channel, and vice versa.
 263      *
 264      * @return  the file channel associated with this file
 265      *
 266      * @since 1.4
 267      * @spec JSR-51
 268      */
 269     public final FileChannel getChannel() {
 270         synchronized (this) {
 271             if (channel == null) {
 272                 channel = FileChannelImpl.open(fd, true, rw, this);
 273             }
 274             return channel;
 275         }
 276     }
 277 
 278     /**
 279      * Opens a file and returns the file descriptor.  The file is
 280      * opened in read-write mode if the O_RDWR bit in {@code mode}
 281      * is true, else the file is opened as read-only.
 282      * If the {@code name} refers to a directory, an IOException
 283      * is thrown.
 284      *
 285      * @param name the name of the file
 286      * @param mode the mode flags, a combination of the O_ constants
 287      *             defined above
 288      */
 289     private native void open(String name, int mode)
 290         throws FileNotFoundException;
 291 
 292     // 'Read' primitives
 293 
 294     /**
 295      * Reads a byte of data from this file. The byte is returned as an
 296      * integer in the range 0 to 255 ({@code 0x00-0x0ff}). This
 297      * method blocks if no input is yet available.
 298      * <p>
 299      * Although {@code RandomAccessFile} is not a subclass of
 300      * {@code InputStream}, this method behaves in exactly the same
 301      * way as the {@link InputStream#read()} method of
 302      * {@code InputStream}.
 303      *
 304      * @return     the next byte of data, or {@code -1} if the end of the
 305      *             file has been reached.
 306      * @exception  IOException  if an I/O error occurs. Not thrown if
 307      *                          end-of-file has been reached.
 308      */
 309     public native int read() throws IOException;











 310 
 311     /**
 312      * Reads a sub array as a sequence of bytes.
 313      * @param b the buffer into which the data is read.
 314      * @param off the start offset of the data.
 315      * @param len the number of bytes to read.
 316      * @exception IOException If an I/O error has occurred.
 317      */
 318     private native int readBytes(byte b[], int off, int len) throws IOException;











 319 
 320     /**
 321      * Reads up to {@code len} bytes of data from this file into an
 322      * array of bytes. This method blocks until at least one byte of input
 323      * is available.
 324      * <p>
 325      * Although {@code RandomAccessFile} is not a subclass of
 326      * {@code InputStream}, this method behaves in exactly the
 327      * same way as the {@link InputStream#read(byte[], int, int)} method of
 328      * {@code InputStream}.
 329      *
 330      * @param      b     the buffer into which the data is read.
 331      * @param      off   the start offset in array {@code b}
 332      *                   at which the data is written.
 333      * @param      len   the maximum number of bytes read.
 334      * @return     the total number of bytes read into the buffer, or
 335      *             {@code -1} if there is no more data because the end of
 336      *             the file has been reached.
 337      * @exception  IOException If the first byte cannot be read for any reason
 338      * other than end of file, or if the random access file has been closed, or if
 339      * some other I/O error occurs.
 340      * @exception  NullPointerException If {@code b} is {@code null}.
 341      * @exception  IndexOutOfBoundsException If {@code off} is negative,
 342      * {@code len} is negative, or {@code len} is greater than
 343      * {@code b.length - off}
 344      */
 345     public int read(byte b[], int off, int len) throws IOException {
 346         return readBytes(b, off, len);
 347     }
 348 
 349     /**
 350      * Reads up to {@code b.length} bytes of data from this file
 351      * into an array of bytes. This method blocks until at least one byte
 352      * of input is available.
 353      * <p>
 354      * Although {@code RandomAccessFile} is not a subclass of
 355      * {@code InputStream}, this method behaves in exactly the
 356      * same way as the {@link InputStream#read(byte[])} method of
 357      * {@code InputStream}.
 358      *
 359      * @param      b   the buffer into which the data is read.
 360      * @return     the total number of bytes read into the buffer, or
 361      *             {@code -1} if there is no more data because the end of
 362      *             this file has been reached.
 363      * @exception  IOException If the first byte cannot be read for any reason
 364      * other than end of file, or if the random access file has been closed, or if
 365      * some other I/O error occurs.
 366      * @exception  NullPointerException If {@code b} is {@code null}.
 367      */
 368     public int read(byte b[]) throws IOException {
 369         return readBytes(b, 0, b.length);
 370     }
 371 
 372     /**
 373      * Reads {@code b.length} bytes from this file into the byte
 374      * array, starting at the current file pointer. This method reads
 375      * repeatedly from the file until the requested number of bytes are
 376      * read. This method blocks until the requested number of bytes are
 377      * read, the end of the stream is detected, or an exception is thrown.
 378      *
 379      * @param      b   the buffer into which the data is read.
 380      * @exception  EOFException  if this file reaches the end before reading
 381      *               all the bytes.
 382      * @exception  IOException   if an I/O error occurs.
 383      */
 384     public final void readFully(byte b[]) throws IOException {
 385         readFully(b, 0, b.length);
 386     }
 387 
 388     /**
 389      * Reads exactly {@code len} bytes from this file into the byte
 390      * array, starting at the current file pointer. This method reads
 391      * repeatedly from the file until the requested number of bytes are
 392      * read. This method blocks until the requested number of bytes are
 393      * read, the end of the stream is detected, or an exception is thrown.
 394      *
 395      * @param      b     the buffer into which the data is read.
 396      * @param      off   the start offset of the data.
 397      * @param      len   the number of bytes to read.
 398      * @exception  EOFException  if this file reaches the end before reading
 399      *               all the bytes.
 400      * @exception  IOException   if an I/O error occurs.
 401      */
 402     public final void readFully(byte b[], int off, int len) throws IOException {
 403         int n = 0;
 404         do {
 405             int count = this.read(b, off + n, len - n);
 406             if (count < 0)
 407                 throw new EOFException();
 408             n += count;
 409         } while (n < len);
 410     }
 411 
 412     /**
 413      * Attempts to skip over {@code n} bytes of input discarding the
 414      * skipped bytes.
 415      * <p>
 416      *
 417      * This method may skip over some smaller number of bytes, possibly zero.
 418      * This may result from any of a number of conditions; reaching end of
 419      * file before {@code n} bytes have been skipped is only one
 420      * possibility. This method never throws an {@code EOFException}.
 421      * The actual number of bytes skipped is returned.  If {@code n}
 422      * is negative, no bytes are skipped.
 423      *
 424      * @param      n   the number of bytes to be skipped.
 425      * @return     the actual number of bytes skipped.
 426      * @exception  IOException  if an I/O error occurs.
 427      */
 428     public int skipBytes(int n) throws IOException {
 429         long pos;
 430         long len;
 431         long newpos;
 432 
 433         if (n <= 0) {
 434             return 0;
 435         }
 436         pos = getFilePointer();
 437         len = length();
 438         newpos = pos + n;
 439         if (newpos > len) {
 440             newpos = len;
 441         }
 442         seek(newpos);
 443 
 444         /* return the actual number of bytes skipped */
 445         return (int) (newpos - pos);
 446     }
 447 
 448     // 'Write' primitives
 449 
 450     /**
 451      * Writes the specified byte to this file. The write starts at
 452      * the current file pointer.
 453      *
 454      * @param      b   the {@code byte} to be written.
 455      * @exception  IOException  if an I/O error occurs.
 456      */
 457     public native void write(int b) throws IOException;











 458 
 459     /**
 460      * Writes a sub array as a sequence of bytes.
 461      * @param b the data to be written
 462 
 463      * @param off the start offset in the data
 464      * @param len the number of bytes that are written
 465      * @exception IOException If an I/O error has occurred.
 466      */
 467     private native void writeBytes(byte b[], int off, int len) throws IOException;











 468 
 469     /**
 470      * Writes {@code b.length} bytes from the specified byte array
 471      * to this file, starting at the current file pointer.
 472      *
 473      * @param      b   the data.
 474      * @exception  IOException  if an I/O error occurs.
 475      */
 476     public void write(byte b[]) throws IOException {
 477         writeBytes(b, 0, b.length);
 478     }
 479 
 480     /**
 481      * Writes {@code len} bytes from the specified byte array
 482      * starting at offset {@code off} to this file.
 483      *
 484      * @param      b     the data.
 485      * @param      off   the start offset in the data.
 486      * @param      len   the number of bytes to write.
 487      * @exception  IOException  if an I/O error occurs.
 488      */
 489     public void write(byte b[], int off, int len) throws IOException {
 490         writeBytes(b, off, len);
 491     }
 492 
 493     // 'Random access' stuff
 494 
 495     /**
 496      * Returns the current offset in this file.
 497      *
 498      * @return     the offset from the beginning of the file, in bytes,
 499      *             at which the next read or write occurs.
 500      * @exception  IOException  if an I/O error occurs.
 501      */
 502     public native long getFilePointer() throws IOException;
 503 
 504     /**
 505      * Sets the file-pointer offset, measured from the beginning of this
 506      * file, at which the next read or write occurs.  The offset may be
 507      * set beyond the end of the file. Setting the offset beyond the end
 508      * of the file does not change the file length.  The file length will
 509      * change only by writing after the offset has been set beyond the end
 510      * of the file.
 511      *
 512      * @param      pos   the offset position, measured in bytes from the
 513      *                   beginning of the file, at which to set the file
 514      *                   pointer.
 515      * @exception  IOException  if {@code pos} is less than
 516      *                          {@code 0} or if an I/O error occurs.
 517      */
 518     public native void seek(long pos) throws IOException;
 519 
 520     /**
 521      * Returns the length of this file.
 522      *
 523      * @return     the length of this file, measured in bytes.
 524      * @exception  IOException  if an I/O error occurs.
 525      */
 526     public native long length() throws IOException;
 527 
 528     /**
 529      * Sets the length of this file.
 530      *
 531      * <p> If the present length of the file as returned by the
 532      * {@code length} method is greater than the {@code newLength}
 533      * argument then the file will be truncated.  In this case, if the file
 534      * offset as returned by the {@code getFilePointer} method is greater
 535      * than {@code newLength} then after this method returns the offset
 536      * will be equal to {@code newLength}.
 537      *
 538      * <p> If the present length of the file as returned by the
 539      * {@code length} method is smaller than the {@code newLength}
 540      * argument then the file will be extended.  In this case, the contents of
 541      * the extended portion of the file are not defined.
 542      *
 543      * @param      newLength    The desired length of the file
 544      * @exception  IOException  If an I/O error occurs
 545      * @since      1.2
 546      */
 547     public native void setLength(long newLength) throws IOException;
 548 
 549     /**
 550      * Closes this random access file stream and releases any system
 551      * resources associated with the stream. A closed random access
 552      * file cannot perform input or output operations and cannot be
 553      * reopened.
 554      *
 555      * <p> If this file has an associated channel then the channel is closed
 556      * as well.
 557      *
 558      * @exception  IOException  if an I/O error occurs.
 559      *
 560      * @revised 1.4
 561      * @spec JSR-51
 562      */
 563     public void close() throws IOException {
 564         synchronized (closeLock) {
 565             if (closed) {
 566                 return;
 567             }
 568             closed = true;
 569         }
 570         if (channel != null) {
 571             channel.close();
 572         }
 573 
 574         fd.closeAll(new Closeable() {
 575             public void close() throws IOException {
 576                close0();
 577            }
 578         });
 579     }
 580 
 581     //
 582     //  Some "reading/writing Java data types" methods stolen from
 583     //  DataInputStream and DataOutputStream.
 584     //
 585 
 586     /**
 587      * Reads a {@code boolean} from this file. This method reads a
 588      * single byte from the file, starting at the current file pointer.
 589      * A value of {@code 0} represents
 590      * {@code false}. Any other value represents {@code true}.
 591      * This method blocks until the byte is read, the end of the stream
 592      * is detected, or an exception is thrown.
 593      *
 594      * @return     the {@code boolean} value read.
 595      * @exception  EOFException  if this file has reached the end.
 596      * @exception  IOException   if an I/O error occurs.
 597      */
 598     public final boolean readBoolean() throws IOException {
 599         int ch = this.read();
 600         if (ch < 0)
 601             throw new EOFException();
 602         return (ch != 0);
 603     }
 604 
 605     /**
 606      * Reads a signed eight-bit value from this file. This method reads a
 607      * byte from the file, starting from the current file pointer.
 608      * If the byte read is {@code b}, where
 609      * <code>0&nbsp;&lt;=&nbsp;b&nbsp;&lt;=&nbsp;255</code>,
 610      * then the result is:
 611      * <blockquote><pre>
 612      *     (byte)(b)
 613      * </pre></blockquote>
 614      * <p>
 615      * This method blocks until the byte is read, the end of the stream
 616      * is detected, or an exception is thrown.
 617      *
 618      * @return     the next byte of this file as a signed eight-bit
 619      *             {@code byte}.
 620      * @exception  EOFException  if this file has reached the end.
 621      * @exception  IOException   if an I/O error occurs.
 622      */
 623     public final byte readByte() throws IOException {
 624         int ch = this.read();
 625         if (ch < 0)
 626             throw new EOFException();
 627         return (byte)(ch);
 628     }
 629 
 630     /**
 631      * Reads an unsigned eight-bit number from this file. This method reads
 632      * a byte from this file, starting at the current file pointer,
 633      * and returns that byte.
 634      * <p>
 635      * This method blocks until the byte is read, the end of the stream
 636      * is detected, or an exception is thrown.
 637      *
 638      * @return     the next byte of this file, interpreted as an unsigned
 639      *             eight-bit number.
 640      * @exception  EOFException  if this file has reached the end.
 641      * @exception  IOException   if an I/O error occurs.
 642      */
 643     public final int readUnsignedByte() throws IOException {
 644         int ch = this.read();
 645         if (ch < 0)
 646             throw new EOFException();
 647         return ch;
 648     }
 649 
 650     /**
 651      * Reads a signed 16-bit number from this file. The method reads two
 652      * bytes from this file, starting at the current file pointer.
 653      * If the two bytes read, in order, are
 654      * {@code b1} and {@code b2}, where each of the two values is
 655      * between {@code 0} and {@code 255}, inclusive, then the
 656      * result is equal to:
 657      * <blockquote><pre>
 658      *     (short)((b1 &lt;&lt; 8) | b2)
 659      * </pre></blockquote>
 660      * <p>
 661      * This method blocks until the two bytes are read, the end of the
 662      * stream is detected, or an exception is thrown.
 663      *
 664      * @return     the next two bytes of this file, interpreted as a signed
 665      *             16-bit number.
 666      * @exception  EOFException  if this file reaches the end before reading
 667      *               two bytes.
 668      * @exception  IOException   if an I/O error occurs.
 669      */
 670     public final short readShort() throws IOException {
 671         int ch1 = this.read();
 672         int ch2 = this.read();
 673         if ((ch1 | ch2) < 0)
 674             throw new EOFException();
 675         return (short)((ch1 << 8) + (ch2 << 0));
 676     }
 677 
 678     /**
 679      * Reads an unsigned 16-bit number from this file. This method reads
 680      * two bytes from the file, starting at the current file pointer.
 681      * If the bytes read, in order, are
 682      * {@code b1} and {@code b2}, where
 683      * <code>0&nbsp;&lt;=&nbsp;b1, b2&nbsp;&lt;=&nbsp;255</code>,
 684      * then the result is equal to:
 685      * <blockquote><pre>
 686      *     (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 an unsigned
 693      *             16-bit integer.
 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 int readUnsignedShort() throws IOException {
 699         int ch1 = this.read();
 700         int ch2 = this.read();
 701         if ((ch1 | ch2) < 0)
 702             throw new EOFException();
 703         return (ch1 << 8) + (ch2 << 0);
 704     }
 705 
 706     /**
 707      * Reads a character from this file. This method reads two
 708      * 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,&nbsp;b2&nbsp;&lt;=&nbsp;255</code>,
 712      * then the result is equal to:
 713      * <blockquote><pre>
 714      *     (char)((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 a
 721      *                  {@code char}.
 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 char readChar() throws IOException {
 727         int ch1 = this.read();
 728         int ch2 = this.read();
 729         if ((ch1 | ch2) < 0)
 730             throw new EOFException();
 731         return (char)((ch1 << 8) + (ch2 << 0));
 732     }
 733 
 734     /**
 735      * Reads a signed 32-bit integer from this file. This method reads 4
 736      * bytes from the file, starting at the current file pointer.
 737      * If the bytes read, in order, are {@code b1},
 738      * {@code b2}, {@code b3}, and {@code b4}, where
 739      * <code>0&nbsp;&lt;=&nbsp;b1, b2, b3, b4&nbsp;&lt;=&nbsp;255</code>,
 740      * then the result is equal to:
 741      * <blockquote><pre>
 742      *     (b1 &lt;&lt; 24) | (b2 &lt;&lt; 16) + (b3 &lt;&lt; 8) + b4
 743      * </pre></blockquote>
 744      * <p>
 745      * This method blocks until the four bytes are read, the end of the
 746      * stream is detected, or an exception is thrown.
 747      *
 748      * @return     the next four bytes of this file, interpreted as an
 749      *             {@code int}.
 750      * @exception  EOFException  if this file reaches the end before reading
 751      *               four bytes.
 752      * @exception  IOException   if an I/O error occurs.
 753      */
 754     public final int readInt() throws IOException {
 755         int ch1 = this.read();
 756         int ch2 = this.read();
 757         int ch3 = this.read();
 758         int ch4 = this.read();
 759         if ((ch1 | ch2 | ch3 | ch4) < 0)
 760             throw new EOFException();
 761         return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
 762     }
 763 
 764     /**
 765      * Reads a signed 64-bit integer from this file. This method reads eight
 766      * bytes from the file, starting at the current file pointer.
 767      * If the bytes read, in order, are
 768      * {@code b1}, {@code b2}, {@code b3},
 769      * {@code b4}, {@code b5}, {@code b6},
 770      * {@code b7}, and {@code b8,} where:
 771      * <blockquote><pre>
 772      *     0 &lt;= b1, b2, b3, b4, b5, b6, b7, b8 &lt;=255,
 773      * </pre></blockquote>
 774      * <p>
 775      * then the result is equal to:
 776      * <p><blockquote><pre>
 777      *     ((long)b1 &lt;&lt; 56) + ((long)b2 &lt;&lt; 48)
 778      *     + ((long)b3 &lt;&lt; 40) + ((long)b4 &lt;&lt; 32)
 779      *     + ((long)b5 &lt;&lt; 24) + ((long)b6 &lt;&lt; 16)
 780      *     + ((long)b7 &lt;&lt; 8) + b8
 781      * </pre></blockquote>
 782      * <p>
 783      * This method blocks until the eight bytes are read, the end of the
 784      * stream is detected, or an exception is thrown.
 785      *
 786      * @return     the next eight bytes of this file, interpreted as a
 787      *             {@code long}.
 788      * @exception  EOFException  if this file reaches the end before reading
 789      *               eight bytes.
 790      * @exception  IOException   if an I/O error occurs.
 791      */
 792     public final long readLong() throws IOException {
 793         return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
 794     }
 795 
 796     /**
 797      * Reads a {@code float} from this file. This method reads an
 798      * {@code int} value, starting at the current file pointer,
 799      * as if by the {@code readInt} method
 800      * and then converts that {@code int} to a {@code float}
 801      * using the {@code intBitsToFloat} method in class
 802      * {@code Float}.
 803      * <p>
 804      * This method blocks until the four bytes are read, the end of the
 805      * stream is detected, or an exception is thrown.
 806      *
 807      * @return     the next four bytes of this file, interpreted as a
 808      *             {@code float}.
 809      * @exception  EOFException  if this file reaches the end before reading
 810      *             four bytes.
 811      * @exception  IOException   if an I/O error occurs.
 812      * @see        java.io.RandomAccessFile#readInt()
 813      * @see        java.lang.Float#intBitsToFloat(int)
 814      */
 815     public final float readFloat() throws IOException {
 816         return Float.intBitsToFloat(readInt());
 817     }
 818 
 819     /**
 820      * Reads a {@code double} from this file. This method reads a
 821      * {@code long} value, starting at the current file pointer,
 822      * as if by the {@code readLong} method
 823      * and then converts that {@code long} to a {@code double}
 824      * using the {@code longBitsToDouble} method in
 825      * class {@code Double}.
 826      * <p>
 827      * This method blocks until the eight bytes are read, the end of the
 828      * stream is detected, or an exception is thrown.
 829      *
 830      * @return     the next eight bytes of this file, interpreted as a
 831      *             {@code double}.
 832      * @exception  EOFException  if this file reaches the end before reading
 833      *             eight bytes.
 834      * @exception  IOException   if an I/O error occurs.
 835      * @see        java.io.RandomAccessFile#readLong()
 836      * @see        java.lang.Double#longBitsToDouble(long)
 837      */
 838     public final double readDouble() throws IOException {
 839         return Double.longBitsToDouble(readLong());
 840     }
 841 
 842     /**
 843      * Reads the next line of text from this file.  This method successively
 844      * reads bytes from the file, starting at the current file pointer,
 845      * until it reaches a line terminator or the end
 846      * of the file.  Each byte is converted into a character by taking the
 847      * byte's value for the lower eight bits of the character and setting the
 848      * high eight bits of the character to zero.  This method does not,
 849      * therefore, support the full Unicode character set.
 850      *
 851      * <p> A line of text is terminated by a carriage-return character
 852      * ({@code '\u005Cr'}), a newline character ({@code '\u005Cn'}), a
 853      * carriage-return character immediately followed by a newline character,
 854      * or the end of the file.  Line-terminating characters are discarded and
 855      * are not included as part of the string returned.
 856      *
 857      * <p> This method blocks until a newline character is read, a carriage
 858      * return and the byte following it are read (to see if it is a newline),
 859      * the end of the file is reached, or an exception is thrown.
 860      *
 861      * @return     the next line of text from this file, or null if end
 862      *             of file is encountered before even one byte is read.
 863      * @exception  IOException  if an I/O error occurs.
 864      */
 865 
 866     public final String readLine() throws IOException {
 867         StringBuffer input = new StringBuffer();
 868         int c = -1;
 869         boolean eol = false;
 870 
 871         while (!eol) {
 872             switch (c = read()) {
 873             case -1:
 874             case '\n':
 875                 eol = true;
 876                 break;
 877             case '\r':
 878                 eol = true;
 879                 long cur = getFilePointer();
 880                 if ((read()) != '\n') {
 881                     seek(cur);
 882                 }
 883                 break;
 884             default:
 885                 input.append((char)c);
 886                 break;
 887             }
 888         }
 889 
 890         if ((c == -1) && (input.length() == 0)) {
 891             return null;
 892         }
 893         return input.toString();
 894     }
 895 
 896     /**
 897      * Reads in a string from this file. The string has been encoded
 898      * using a
 899      * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
 900      * format.
 901      * <p>
 902      * The first two bytes are read, starting from the current file
 903      * pointer, as if by
 904      * {@code readUnsignedShort}. This value gives the number of
 905      * following bytes that are in the encoded string, not
 906      * the length of the resulting string. The following bytes are then
 907      * interpreted as bytes encoding characters in the modified UTF-8 format
 908      * and are converted into characters.
 909      * <p>
 910      * This method blocks until all the bytes are read, the end of the
 911      * stream is detected, or an exception is thrown.
 912      *
 913      * @return     a Unicode string.
 914      * @exception  EOFException            if this file reaches the end before
 915      *               reading all the bytes.
 916      * @exception  IOException             if an I/O error occurs.
 917      * @exception  UTFDataFormatException  if the bytes do not represent
 918      *               valid modified UTF-8 encoding of a Unicode string.
 919      * @see        java.io.RandomAccessFile#readUnsignedShort()
 920      */
 921     public final String readUTF() throws IOException {
 922         return DataInputStream.readUTF(this);
 923     }
 924 
 925     /**
 926      * Writes a {@code boolean} to the file as a one-byte value. The
 927      * value {@code true} is written out as the value
 928      * {@code (byte)1}; the value {@code false} is written out
 929      * as the value {@code (byte)0}. The write starts at
 930      * the current position of the file pointer.
 931      *
 932      * @param      v   a {@code boolean} value to be written.
 933      * @exception  IOException  if an I/O error occurs.
 934      */
 935     public final void writeBoolean(boolean v) throws IOException {
 936         write(v ? 1 : 0);
 937         //written++;
 938     }
 939 
 940     /**
 941      * Writes a {@code byte} to the file as a one-byte value. The
 942      * write starts at the current position of the file pointer.
 943      *
 944      * @param      v   a {@code byte} value to be written.
 945      * @exception  IOException  if an I/O error occurs.
 946      */
 947     public final void writeByte(int v) throws IOException {
 948         write(v);
 949         //written++;
 950     }
 951 
 952     /**
 953      * Writes a {@code short} to the file as two bytes, high byte first.
 954      * The write starts at the current position of the file pointer.
 955      *
 956      * @param      v   a {@code short} to be written.
 957      * @exception  IOException  if an I/O error occurs.
 958      */
 959     public final void writeShort(int v) throws IOException {
 960         write((v >>> 8) & 0xFF);
 961         write((v >>> 0) & 0xFF);
 962         //written += 2;
 963     }
 964 
 965     /**
 966      * Writes a {@code char} to the file as a two-byte value, high
 967      * byte first. The write starts at the current position of the
 968      * file pointer.
 969      *
 970      * @param      v   a {@code char} value to be written.
 971      * @exception  IOException  if an I/O error occurs.
 972      */
 973     public final void writeChar(int v) throws IOException {
 974         write((v >>> 8) & 0xFF);
 975         write((v >>> 0) & 0xFF);
 976         //written += 2;
 977     }
 978 
 979     /**
 980      * Writes an {@code int} to the file as four bytes, high byte first.
 981      * The write starts at the current position of the file pointer.
 982      *
 983      * @param      v   an {@code int} to be written.
 984      * @exception  IOException  if an I/O error occurs.
 985      */
 986     public final void writeInt(int v) throws IOException {
 987         write((v >>> 24) & 0xFF);
 988         write((v >>> 16) & 0xFF);
 989         write((v >>>  8) & 0xFF);
 990         write((v >>>  0) & 0xFF);
 991         //written += 4;
 992     }
 993 
 994     /**
 995      * Writes a {@code long} to the file as eight bytes, high byte first.
 996      * The write starts at the current position of the file pointer.
 997      *
 998      * @param      v   a {@code long} to be written.
 999      * @exception  IOException  if an I/O error occurs.
1000      */
1001     public final void writeLong(long v) throws IOException {
1002         write((int)(v >>> 56) & 0xFF);
1003         write((int)(v >>> 48) & 0xFF);
1004         write((int)(v >>> 40) & 0xFF);
1005         write((int)(v >>> 32) & 0xFF);
1006         write((int)(v >>> 24) & 0xFF);
1007         write((int)(v >>> 16) & 0xFF);
1008         write((int)(v >>>  8) & 0xFF);
1009         write((int)(v >>>  0) & 0xFF);
1010         //written += 8;
1011     }
1012 
1013     /**
1014      * Converts the float argument to an {@code int} using the
1015      * {@code floatToIntBits} method in class {@code Float},
1016      * and then writes that {@code int} value to the file as a
1017      * four-byte quantity, high byte first. The write starts at the
1018      * current position of the file pointer.
1019      *
1020      * @param      v   a {@code float} value to be written.
1021      * @exception  IOException  if an I/O error occurs.
1022      * @see        java.lang.Float#floatToIntBits(float)
1023      */
1024     public final void writeFloat(float v) throws IOException {
1025         writeInt(Float.floatToIntBits(v));
1026     }
1027 
1028     /**
1029      * Converts the double argument to a {@code long} using the
1030      * {@code doubleToLongBits} method in class {@code Double},
1031      * and then writes that {@code long} value to the file as an
1032      * eight-byte quantity, high byte first. The write starts at the current
1033      * position of the file pointer.
1034      *
1035      * @param      v   a {@code double} value to be written.
1036      * @exception  IOException  if an I/O error occurs.
1037      * @see        java.lang.Double#doubleToLongBits(double)
1038      */
1039     public final void writeDouble(double v) throws IOException {
1040         writeLong(Double.doubleToLongBits(v));
1041     }
1042 
1043     /**
1044      * Writes the string to the file as a sequence of bytes. Each
1045      * character in the string is written out, in sequence, by discarding
1046      * its high eight bits. The write starts at the current position of
1047      * the file pointer.
1048      *
1049      * @param      s   a string of bytes to be written.
1050      * @exception  IOException  if an I/O error occurs.
1051      */
1052     @SuppressWarnings("deprecation")
1053     public final void writeBytes(String s) throws IOException {
1054         int len = s.length();
1055         byte[] b = new byte[len];
1056         s.getBytes(0, len, b, 0);
1057         writeBytes(b, 0, len);
1058     }
1059 
1060     /**
1061      * Writes a string to the file as a sequence of characters. Each
1062      * character is written to the data output stream as if by the
1063      * {@code writeChar} method. The write starts at the current
1064      * position of the file pointer.
1065      *
1066      * @param      s   a {@code String} value to be written.
1067      * @exception  IOException  if an I/O error occurs.
1068      * @see        java.io.RandomAccessFile#writeChar(int)
1069      */
1070     public final void writeChars(String s) throws IOException {
1071         int clen = s.length();
1072         int blen = 2*clen;
1073         byte[] b = new byte[blen];
1074         char[] c = new char[clen];
1075         s.getChars(0, clen, c, 0);
1076         for (int i = 0, j = 0; i < clen; i++) {
1077             b[j++] = (byte)(c[i] >>> 8);
1078             b[j++] = (byte)(c[i] >>> 0);
1079         }
1080         writeBytes(b, 0, blen);
1081     }
1082 
1083     /**
1084      * Writes a string to the file using
1085      * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
1086      * encoding in a machine-independent manner.
1087      * <p>
1088      * First, two bytes are written to the file, starting at the
1089      * current file pointer, as if by the
1090      * {@code writeShort} method giving the number of bytes to
1091      * follow. This value is the number of bytes actually written out,
1092      * not the length of the string. Following the length, each character
1093      * of the string is output, in sequence, using the modified UTF-8 encoding
1094      * for each character.
1095      *
1096      * @param      str   a string to be written.
1097      * @exception  IOException  if an I/O error occurs.
1098      */
1099     public final void writeUTF(String str) throws IOException {
1100         DataOutputStream.writeUTF(str, this);
1101     }
1102 
1103     private static native void initIDs();
1104 
1105     private native void close0() throws IOException;
1106 
1107     static {
1108         initIDs();
1109     }
1110 }
--- EOF ---