rev 5501 : imported patch 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</code> method and set by the <code>seek</code>
  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</code> (which is a kind of
  50  * <code>IOException</code>) is thrown. If any byte cannot be read for
  51  * any reason other than end-of-file, an <code>IOException</code> other
  52  * than <code>EOFException</code> is thrown. In particular, an
  53  * <code>IOException</code> 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</code> method
  86      * is called with the <code>name</code> 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</code> method
  90      * is also called with the <code>name</code> 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</code> method denies read access to the file
 107      *               or the mode is "rw" and the security manager's
 108      *               <code>checkWrite</code> 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</code> method is
 168      * called with the pathname of the <code>file</code> 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</code> 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</code> method denies read access to the file
 189      *               or the mode is "rw" and the security manager's
 190      *               <code>checkWrite</code> 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.incrementAndGetUseCount();

 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) return fd;
 246         throw new IOException();
 247     }
 248 
 249     /**
 250      * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
 251      * object associated with this file.
 252      *
 253      * <p> The {@link java.nio.channels.FileChannel#position()
 254      * </code>position<code>} of the returned channel will always be equal to
 255      * this object's file-pointer offset as returned by the {@link
 256      * #getFilePointer getFilePointer} method.  Changing this object's
 257      * file-pointer offset, whether explicitly or by reading or writing bytes,
 258      * will change the position of the channel, and vice versa.  Changing the
 259      * file's length via this object will change the length seen via the file
 260      * channel, and vice versa.
 261      *
 262      * @return  the file channel associated with this file
 263      *
 264      * @since 1.4
 265      * @spec JSR-51
 266      */
 267     public final FileChannel getChannel() {
 268         synchronized (this) {
 269             if (channel == null) {
 270                 channel = FileChannelImpl.open(fd, true, rw, this);
 271 
 272                 /*
 273                  * FileDescriptor could be shared by FileInputStream or
 274                  * FileOutputStream.
 275                  * Ensure that FD is GC'ed only when all the streams/channels
 276                  * are done using it.
 277                  * Increment fd's use count. Invoking the channel's close()
 278                  * method will result in decrementing the use count set for
 279                  * the channel.
 280                  */
 281                 fd.incrementAndGetUseCount();
 282             }
 283             return channel;
 284         }
 285     }
 286 
 287     /**
 288      * Opens a file and returns the file descriptor.  The file is
 289      * opened in read-write mode if the O_RDWR bit in <code>mode</code>
 290      * is true, else the file is opened as read-only.
 291      * If the <code>name</code> refers to a directory, an IOException
 292      * is thrown.
 293      *
 294      * @param name the name of the file
 295      * @param mode the mode flags, a combination of the O_ constants
 296      *             defined above
 297      */
 298     private native void open(String name, int mode)
 299         throws FileNotFoundException;
 300 
 301     // 'Read' primitives
 302 
 303     /**
 304      * Reads a byte of data from this file. The byte is returned as an
 305      * integer in the range 0 to 255 (<code>0x00-0x0ff</code>). This
 306      * method blocks if no input is yet available.
 307      * <p>
 308      * Although <code>RandomAccessFile</code> is not a subclass of
 309      * <code>InputStream</code>, this method behaves in exactly the same
 310      * way as the {@link InputStream#read()} method of
 311      * <code>InputStream</code>.
 312      *
 313      * @return     the next byte of data, or <code>-1</code> if the end of the
 314      *             file has been reached.
 315      * @exception  IOException  if an I/O error occurs. Not thrown if
 316      *                          end-of-file has been reached.
 317      */
 318     public native int read() throws IOException;











 319 
 320     /**
 321      * Reads a sub array as a sequence of bytes.
 322      * @param b the buffer into which the data is read.
 323      * @param off the start offset of the data.
 324      * @param len the number of bytes to read.
 325      * @exception IOException If an I/O error has occurred.
 326      */
 327     private native int readBytes(byte b[], int off, int len) throws IOException;











 328 
 329     /**
 330      * Reads up to <code>len</code> bytes of data from this file into an
 331      * array of bytes. This method blocks until at least one byte of input
 332      * is available.
 333      * <p>
 334      * Although <code>RandomAccessFile</code> is not a subclass of
 335      * <code>InputStream</code>, this method behaves in exactly the
 336      * same way as the {@link InputStream#read(byte[], int, int)} method of
 337      * <code>InputStream</code>.
 338      *
 339      * @param      b     the buffer into which the data is read.
 340      * @param      off   the start offset in array <code>b</code>
 341      *                   at which the data is written.
 342      * @param      len   the maximum number of bytes read.
 343      * @return     the total number of bytes read into the buffer, or
 344      *             <code>-1</code> if there is no more data because the end of
 345      *             the file has been reached.
 346      * @exception  IOException If the first byte cannot be read for any reason
 347      * other than end of file, or if the random access file has been closed, or if
 348      * some other I/O error occurs.
 349      * @exception  NullPointerException If <code>b</code> is <code>null</code>.
 350      * @exception  IndexOutOfBoundsException If <code>off</code> is negative,
 351      * <code>len</code> is negative, or <code>len</code> is greater than
 352      * <code>b.length - off</code>
 353      */
 354     public int read(byte b[], int off, int len) throws IOException {
 355         return readBytes(b, off, len);
 356     }
 357 
 358     /**
 359      * Reads up to <code>b.length</code> bytes of data from this file
 360      * into an array of bytes. This method blocks until at least one byte
 361      * of input is available.
 362      * <p>
 363      * Although <code>RandomAccessFile</code> is not a subclass of
 364      * <code>InputStream</code>, this method behaves in exactly the
 365      * same way as the {@link InputStream#read(byte[])} method of
 366      * <code>InputStream</code>.
 367      *
 368      * @param      b   the buffer into which the data is read.
 369      * @return     the total number of bytes read into the buffer, or
 370      *             <code>-1</code> if there is no more data because the end of
 371      *             this file has been reached.
 372      * @exception  IOException If the first byte cannot be read for any reason
 373      * other than end of file, or if the random access file has been closed, or if
 374      * some other I/O error occurs.
 375      * @exception  NullPointerException If <code>b</code> is <code>null</code>.
 376      */
 377     public int read(byte b[]) throws IOException {
 378         return readBytes(b, 0, b.length);
 379     }
 380 
 381     /**
 382      * Reads <code>b.length</code> bytes from this file into the byte
 383      * array, starting at the current file pointer. This method reads
 384      * repeatedly from the file until the requested number of bytes are
 385      * read. This method blocks until the requested number of bytes are
 386      * read, the end of the stream is detected, or an exception is thrown.
 387      *
 388      * @param      b   the buffer into which the data is read.
 389      * @exception  EOFException  if this file reaches the end before reading
 390      *               all the bytes.
 391      * @exception  IOException   if an I/O error occurs.
 392      */
 393     public final void readFully(byte b[]) throws IOException {
 394         readFully(b, 0, b.length);
 395     }
 396 
 397     /**
 398      * Reads exactly <code>len</code> bytes from this file into the byte
 399      * array, starting at the current file pointer. This method reads
 400      * repeatedly from the file until the requested number of bytes are
 401      * read. This method blocks until the requested number of bytes are
 402      * read, the end of the stream is detected, or an exception is thrown.
 403      *
 404      * @param      b     the buffer into which the data is read.
 405      * @param      off   the start offset of the data.
 406      * @param      len   the number of bytes to read.
 407      * @exception  EOFException  if this file reaches the end before reading
 408      *               all the bytes.
 409      * @exception  IOException   if an I/O error occurs.
 410      */
 411     public final void readFully(byte b[], int off, int len) throws IOException {
 412         int n = 0;
 413         do {
 414             int count = this.read(b, off + n, len - n);
 415             if (count < 0)
 416                 throw new EOFException();
 417             n += count;
 418         } while (n < len);
 419     }
 420 
 421     /**
 422      * Attempts to skip over <code>n</code> bytes of input discarding the
 423      * skipped bytes.
 424      * <p>
 425      *
 426      * This method may skip over some smaller number of bytes, possibly zero.
 427      * This may result from any of a number of conditions; reaching end of
 428      * file before <code>n</code> bytes have been skipped is only one
 429      * possibility. This method never throws an <code>EOFException</code>.
 430      * The actual number of bytes skipped is returned.  If <code>n</code>
 431      * is negative, no bytes are skipped.
 432      *
 433      * @param      n   the number of bytes to be skipped.
 434      * @return     the actual number of bytes skipped.
 435      * @exception  IOException  if an I/O error occurs.
 436      */
 437     public int skipBytes(int n) throws IOException {
 438         long pos;
 439         long len;
 440         long newpos;
 441 
 442         if (n <= 0) {
 443             return 0;
 444         }
 445         pos = getFilePointer();
 446         len = length();
 447         newpos = pos + n;
 448         if (newpos > len) {
 449             newpos = len;
 450         }
 451         seek(newpos);
 452 
 453         /* return the actual number of bytes skipped */
 454         return (int) (newpos - pos);
 455     }
 456 
 457     // 'Write' primitives
 458 
 459     /**
 460      * Writes the specified byte to this file. The write starts at
 461      * the current file pointer.
 462      *
 463      * @param      b   the <code>byte</code> to be written.
 464      * @exception  IOException  if an I/O error occurs.
 465      */
 466     public native void write(int b) throws IOException;











 467 
 468     /**
 469      * Writes a sub array as a sequence of bytes.
 470      * @param b the data to be written
 471 
 472      * @param off the start offset in the data
 473      * @param len the number of bytes that are written
 474      * @exception IOException If an I/O error has occurred.
 475      */
 476     private native void writeBytes(byte b[], int off, int len) throws IOException;











 477 
 478     /**
 479      * Writes <code>b.length</code> bytes from the specified byte array
 480      * to this file, starting at the current file pointer.
 481      *
 482      * @param      b   the data.
 483      * @exception  IOException  if an I/O error occurs.
 484      */
 485     public void write(byte b[]) throws IOException {
 486         writeBytes(b, 0, b.length);
 487     }
 488 
 489     /**
 490      * Writes <code>len</code> bytes from the specified byte array
 491      * starting at offset <code>off</code> to this file.
 492      *
 493      * @param      b     the data.
 494      * @param      off   the start offset in the data.
 495      * @param      len   the number of bytes to write.
 496      * @exception  IOException  if an I/O error occurs.
 497      */
 498     public void write(byte b[], int off, int len) throws IOException {
 499         writeBytes(b, off, len);
 500     }
 501 
 502     // 'Random access' stuff
 503 
 504     /**
 505      * Returns the current offset in this file.
 506      *
 507      * @return     the offset from the beginning of the file, in bytes,
 508      *             at which the next read or write occurs.
 509      * @exception  IOException  if an I/O error occurs.
 510      */
 511     public native long getFilePointer() throws IOException;
 512 
 513     /**
 514      * Sets the file-pointer offset, measured from the beginning of this
 515      * file, at which the next read or write occurs.  The offset may be
 516      * set beyond the end of the file. Setting the offset beyond the end
 517      * of the file does not change the file length.  The file length will
 518      * change only by writing after the offset has been set beyond the end
 519      * of the file.
 520      *
 521      * @param      pos   the offset position, measured in bytes from the
 522      *                   beginning of the file, at which to set the file
 523      *                   pointer.
 524      * @exception  IOException  if <code>pos</code> is less than
 525      *                          <code>0</code> or if an I/O error occurs.
 526      */
 527     public native void seek(long pos) throws IOException;
 528 
 529     /**
 530      * Returns the length of this file.
 531      *
 532      * @return     the length of this file, measured in bytes.
 533      * @exception  IOException  if an I/O error occurs.
 534      */
 535     public native long length() throws IOException;
 536 
 537     /**
 538      * Sets the length of this file.
 539      *
 540      * <p> If the present length of the file as returned by the
 541      * <code>length</code> method is greater than the <code>newLength</code>
 542      * argument then the file will be truncated.  In this case, if the file
 543      * offset as returned by the <code>getFilePointer</code> method is greater
 544      * than <code>newLength</code> then after this method returns the offset
 545      * will be equal to <code>newLength</code>.
 546      *
 547      * <p> If the present length of the file as returned by the
 548      * <code>length</code> method is smaller than the <code>newLength</code>
 549      * argument then the file will be extended.  In this case, the contents of
 550      * the extended portion of the file are not defined.
 551      *
 552      * @param      newLength    The desired length of the file
 553      * @exception  IOException  If an I/O error occurs
 554      * @since      1.2
 555      */
 556     public native void setLength(long newLength) throws IOException;
 557 
 558     /**
 559      * Closes this random access file stream and releases any system
 560      * resources associated with the stream. A closed random access
 561      * file cannot perform input or output operations and cannot be
 562      * reopened.
 563      *
 564      * <p> If this file has an associated channel then the channel is closed
 565      * as well.
 566      *
 567      * @exception  IOException  if an I/O error occurs.
 568      *
 569      * @revised 1.4
 570      * @spec JSR-51
 571      */
 572     public void close() throws IOException {
 573         synchronized (closeLock) {
 574             if (closed) {
 575                 return;
 576             }
 577             closed = true;
 578         }
 579         if (channel != null) {
 580             /*
 581              * Decrement FD use count associated with the channel. The FD use
 582              * count is incremented whenever a new channel is obtained from
 583              * this stream.
 584              */
 585             fd.decrementAndGetUseCount();
 586             channel.close();
 587         }
 588 
 589         /*
 590          * Decrement FD use count associated with this stream.
 591          * The count got incremented by FileDescriptor during its construction.
 592          */
 593         fd.decrementAndGetUseCount();
 594         close0();
 595     }
 596 
 597     //
 598     //  Some "reading/writing Java data types" methods stolen from
 599     //  DataInputStream and DataOutputStream.
 600     //
 601 
 602     /**
 603      * Reads a <code>boolean</code> from this file. This method reads a
 604      * single byte from the file, starting at the current file pointer.
 605      * A value of <code>0</code> represents
 606      * <code>false</code>. Any other value represents <code>true</code>.
 607      * This method blocks until the byte is read, the end of the stream
 608      * is detected, or an exception is thrown.
 609      *
 610      * @return     the <code>boolean</code> value read.
 611      * @exception  EOFException  if this file has reached the end.
 612      * @exception  IOException   if an I/O error occurs.
 613      */
 614     public final boolean readBoolean() throws IOException {
 615         int ch = this.read();
 616         if (ch < 0)
 617             throw new EOFException();
 618         return (ch != 0);
 619     }
 620 
 621     /**
 622      * Reads a signed eight-bit value from this file. This method reads a
 623      * byte from the file, starting from the current file pointer.
 624      * If the byte read is <code>b</code>, where
 625      * <code>0&nbsp;&lt;=&nbsp;b&nbsp;&lt;=&nbsp;255</code>,
 626      * then the result is:
 627      * <blockquote><pre>
 628      *     (byte)(b)
 629      * </pre></blockquote>
 630      * <p>
 631      * This method blocks until the byte is read, the end of the stream
 632      * is detected, or an exception is thrown.
 633      *
 634      * @return     the next byte of this file as a signed eight-bit
 635      *             <code>byte</code>.
 636      * @exception  EOFException  if this file has reached the end.
 637      * @exception  IOException   if an I/O error occurs.
 638      */
 639     public final byte readByte() throws IOException {
 640         int ch = this.read();
 641         if (ch < 0)
 642             throw new EOFException();
 643         return (byte)(ch);
 644     }
 645 
 646     /**
 647      * Reads an unsigned eight-bit number from this file. This method reads
 648      * a byte from this file, starting at the current file pointer,
 649      * and returns that byte.
 650      * <p>
 651      * This method blocks until the byte is read, the end of the stream
 652      * is detected, or an exception is thrown.
 653      *
 654      * @return     the next byte of this file, interpreted as an unsigned
 655      *             eight-bit number.
 656      * @exception  EOFException  if this file has reached the end.
 657      * @exception  IOException   if an I/O error occurs.
 658      */
 659     public final int readUnsignedByte() throws IOException {
 660         int ch = this.read();
 661         if (ch < 0)
 662             throw new EOFException();
 663         return ch;
 664     }
 665 
 666     /**
 667      * Reads a signed 16-bit number from this file. The method reads two
 668      * bytes from this file, starting at the current file pointer.
 669      * If the two bytes read, in order, are
 670      * <code>b1</code> and <code>b2</code>, where each of the two values is
 671      * between <code>0</code> and <code>255</code>, inclusive, then the
 672      * result is equal to:
 673      * <blockquote><pre>
 674      *     (short)((b1 &lt;&lt; 8) | b2)
 675      * </pre></blockquote>
 676      * <p>
 677      * This method blocks until the two bytes are read, the end of the
 678      * stream is detected, or an exception is thrown.
 679      *
 680      * @return     the next two bytes of this file, interpreted as a signed
 681      *             16-bit number.
 682      * @exception  EOFException  if this file reaches the end before reading
 683      *               two bytes.
 684      * @exception  IOException   if an I/O error occurs.
 685      */
 686     public final short readShort() throws IOException {
 687         int ch1 = this.read();
 688         int ch2 = this.read();
 689         if ((ch1 | ch2) < 0)
 690             throw new EOFException();
 691         return (short)((ch1 << 8) + (ch2 << 0));
 692     }
 693 
 694     /**
 695      * Reads an unsigned 16-bit number from this file. This method reads
 696      * two bytes from the file, starting at the current file pointer.
 697      * If the bytes read, in order, are
 698      * <code>b1</code> and <code>b2</code>, where
 699      * <code>0&nbsp;&lt;=&nbsp;b1, b2&nbsp;&lt;=&nbsp;255</code>,
 700      * then the result is equal to:
 701      * <blockquote><pre>
 702      *     (b1 &lt;&lt; 8) | b2
 703      * </pre></blockquote>
 704      * <p>
 705      * This method blocks until the two bytes are read, the end of the
 706      * stream is detected, or an exception is thrown.
 707      *
 708      * @return     the next two bytes of this file, interpreted as an unsigned
 709      *             16-bit integer.
 710      * @exception  EOFException  if this file reaches the end before reading
 711      *               two bytes.
 712      * @exception  IOException   if an I/O error occurs.
 713      */
 714     public final int readUnsignedShort() throws IOException {
 715         int ch1 = this.read();
 716         int ch2 = this.read();
 717         if ((ch1 | ch2) < 0)
 718             throw new EOFException();
 719         return (ch1 << 8) + (ch2 << 0);
 720     }
 721 
 722     /**
 723      * Reads a character from this file. This method reads two
 724      * bytes from the file, starting at the current file pointer.
 725      * If the bytes read, in order, are
 726      * <code>b1</code> and <code>b2</code>, where
 727      * <code>0&nbsp;&lt;=&nbsp;b1,&nbsp;b2&nbsp;&lt;=&nbsp;255</code>,
 728      * then the result is equal to:
 729      * <blockquote><pre>
 730      *     (char)((b1 &lt;&lt; 8) | b2)
 731      * </pre></blockquote>
 732      * <p>
 733      * This method blocks until the two bytes are read, the end of the
 734      * stream is detected, or an exception is thrown.
 735      *
 736      * @return     the next two bytes of this file, interpreted as a
 737      *                  <code>char</code>.
 738      * @exception  EOFException  if this file reaches the end before reading
 739      *               two bytes.
 740      * @exception  IOException   if an I/O error occurs.
 741      */
 742     public final char readChar() throws IOException {
 743         int ch1 = this.read();
 744         int ch2 = this.read();
 745         if ((ch1 | ch2) < 0)
 746             throw new EOFException();
 747         return (char)((ch1 << 8) + (ch2 << 0));
 748     }
 749 
 750     /**
 751      * Reads a signed 32-bit integer from this file. This method reads 4
 752      * bytes from the file, starting at the current file pointer.
 753      * If the bytes read, in order, are <code>b1</code>,
 754      * <code>b2</code>, <code>b3</code>, and <code>b4</code>, where
 755      * <code>0&nbsp;&lt;=&nbsp;b1, b2, b3, b4&nbsp;&lt;=&nbsp;255</code>,
 756      * then the result is equal to:
 757      * <blockquote><pre>
 758      *     (b1 &lt;&lt; 24) | (b2 &lt;&lt; 16) + (b3 &lt;&lt; 8) + b4
 759      * </pre></blockquote>
 760      * <p>
 761      * This method blocks until the four bytes are read, the end of the
 762      * stream is detected, or an exception is thrown.
 763      *
 764      * @return     the next four bytes of this file, interpreted as an
 765      *             <code>int</code>.
 766      * @exception  EOFException  if this file reaches the end before reading
 767      *               four bytes.
 768      * @exception  IOException   if an I/O error occurs.
 769      */
 770     public final int readInt() throws IOException {
 771         int ch1 = this.read();
 772         int ch2 = this.read();
 773         int ch3 = this.read();
 774         int ch4 = this.read();
 775         if ((ch1 | ch2 | ch3 | ch4) < 0)
 776             throw new EOFException();
 777         return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
 778     }
 779 
 780     /**
 781      * Reads a signed 64-bit integer from this file. This method reads eight
 782      * bytes from the file, starting at the current file pointer.
 783      * If the bytes read, in order, are
 784      * <code>b1</code>, <code>b2</code>, <code>b3</code>,
 785      * <code>b4</code>, <code>b5</code>, <code>b6</code>,
 786      * <code>b7</code>, and <code>b8,</code> where:
 787      * <blockquote><pre>
 788      *     0 &lt;= b1, b2, b3, b4, b5, b6, b7, b8 &lt;=255,
 789      * </pre></blockquote>
 790      * <p>
 791      * then the result is equal to:
 792      * <p><blockquote><pre>
 793      *     ((long)b1 &lt;&lt; 56) + ((long)b2 &lt;&lt; 48)
 794      *     + ((long)b3 &lt;&lt; 40) + ((long)b4 &lt;&lt; 32)
 795      *     + ((long)b5 &lt;&lt; 24) + ((long)b6 &lt;&lt; 16)
 796      *     + ((long)b7 &lt;&lt; 8) + b8
 797      * </pre></blockquote>
 798      * <p>
 799      * This method blocks until the eight bytes are read, the end of the
 800      * stream is detected, or an exception is thrown.
 801      *
 802      * @return     the next eight bytes of this file, interpreted as a
 803      *             <code>long</code>.
 804      * @exception  EOFException  if this file reaches the end before reading
 805      *               eight bytes.
 806      * @exception  IOException   if an I/O error occurs.
 807      */
 808     public final long readLong() throws IOException {
 809         return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
 810     }
 811 
 812     /**
 813      * Reads a <code>float</code> from this file. This method reads an
 814      * <code>int</code> value, starting at the current file pointer,
 815      * as if by the <code>readInt</code> method
 816      * and then converts that <code>int</code> to a <code>float</code>
 817      * using the <code>intBitsToFloat</code> method in class
 818      * <code>Float</code>.
 819      * <p>
 820      * This method blocks until the four bytes are read, the end of the
 821      * stream is detected, or an exception is thrown.
 822      *
 823      * @return     the next four bytes of this file, interpreted as a
 824      *             <code>float</code>.
 825      * @exception  EOFException  if this file reaches the end before reading
 826      *             four bytes.
 827      * @exception  IOException   if an I/O error occurs.
 828      * @see        java.io.RandomAccessFile#readInt()
 829      * @see        java.lang.Float#intBitsToFloat(int)
 830      */
 831     public final float readFloat() throws IOException {
 832         return Float.intBitsToFloat(readInt());
 833     }
 834 
 835     /**
 836      * Reads a <code>double</code> from this file. This method reads a
 837      * <code>long</code> value, starting at the current file pointer,
 838      * as if by the <code>readLong</code> method
 839      * and then converts that <code>long</code> to a <code>double</code>
 840      * using the <code>longBitsToDouble</code> method in
 841      * class <code>Double</code>.
 842      * <p>
 843      * This method blocks until the eight bytes are read, the end of the
 844      * stream is detected, or an exception is thrown.
 845      *
 846      * @return     the next eight bytes of this file, interpreted as a
 847      *             <code>double</code>.
 848      * @exception  EOFException  if this file reaches the end before reading
 849      *             eight bytes.
 850      * @exception  IOException   if an I/O error occurs.
 851      * @see        java.io.RandomAccessFile#readLong()
 852      * @see        java.lang.Double#longBitsToDouble(long)
 853      */
 854     public final double readDouble() throws IOException {
 855         return Double.longBitsToDouble(readLong());
 856     }
 857 
 858     /**
 859      * Reads the next line of text from this file.  This method successively
 860      * reads bytes from the file, starting at the current file pointer,
 861      * until it reaches a line terminator or the end
 862      * of the file.  Each byte is converted into a character by taking the
 863      * byte's value for the lower eight bits of the character and setting the
 864      * high eight bits of the character to zero.  This method does not,
 865      * therefore, support the full Unicode character set.
 866      *
 867      * <p> A line of text is terminated by a carriage-return character
 868      * (<code>'&#92;r'</code>), a newline character (<code>'&#92;n'</code>), a
 869      * carriage-return character immediately followed by a newline character,
 870      * or the end of the file.  Line-terminating characters are discarded and
 871      * are not included as part of the string returned.
 872      *
 873      * <p> This method blocks until a newline character is read, a carriage
 874      * return and the byte following it are read (to see if it is a newline),
 875      * the end of the file is reached, or an exception is thrown.
 876      *
 877      * @return     the next line of text from this file, or null if end
 878      *             of file is encountered before even one byte is read.
 879      * @exception  IOException  if an I/O error occurs.
 880      */
 881 
 882     public final String readLine() throws IOException {
 883         StringBuffer input = new StringBuffer();
 884         int c = -1;
 885         boolean eol = false;
 886 
 887         while (!eol) {
 888             switch (c = read()) {
 889             case -1:
 890             case '\n':
 891                 eol = true;
 892                 break;
 893             case '\r':
 894                 eol = true;
 895                 long cur = getFilePointer();
 896                 if ((read()) != '\n') {
 897                     seek(cur);
 898                 }
 899                 break;
 900             default:
 901                 input.append((char)c);
 902                 break;
 903             }
 904         }
 905 
 906         if ((c == -1) && (input.length() == 0)) {
 907             return null;
 908         }
 909         return input.toString();
 910     }
 911 
 912     /**
 913      * Reads in a string from this file. The string has been encoded
 914      * using a
 915      * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
 916      * format.
 917      * <p>
 918      * The first two bytes are read, starting from the current file
 919      * pointer, as if by
 920      * <code>readUnsignedShort</code>. This value gives the number of
 921      * following bytes that are in the encoded string, not
 922      * the length of the resulting string. The following bytes are then
 923      * interpreted as bytes encoding characters in the modified UTF-8 format
 924      * and are converted into characters.
 925      * <p>
 926      * This method blocks until all the bytes are read, the end of the
 927      * stream is detected, or an exception is thrown.
 928      *
 929      * @return     a Unicode string.
 930      * @exception  EOFException            if this file reaches the end before
 931      *               reading all the bytes.
 932      * @exception  IOException             if an I/O error occurs.
 933      * @exception  UTFDataFormatException  if the bytes do not represent
 934      *               valid modified UTF-8 encoding of a Unicode string.
 935      * @see        java.io.RandomAccessFile#readUnsignedShort()
 936      */
 937     public final String readUTF() throws IOException {
 938         return DataInputStream.readUTF(this);
 939     }
 940 
 941     /**
 942      * Writes a <code>boolean</code> to the file as a one-byte value. The
 943      * value <code>true</code> is written out as the value
 944      * <code>(byte)1</code>; the value <code>false</code> is written out
 945      * as the value <code>(byte)0</code>. The write starts at
 946      * the current position of the file pointer.
 947      *
 948      * @param      v   a <code>boolean</code> value to be written.
 949      * @exception  IOException  if an I/O error occurs.
 950      */
 951     public final void writeBoolean(boolean v) throws IOException {
 952         write(v ? 1 : 0);
 953         //written++;
 954     }
 955 
 956     /**
 957      * Writes a <code>byte</code> to the file as a one-byte value. The
 958      * write starts at the current position of the file pointer.
 959      *
 960      * @param      v   a <code>byte</code> value to be written.
 961      * @exception  IOException  if an I/O error occurs.
 962      */
 963     public final void writeByte(int v) throws IOException {
 964         write(v);
 965         //written++;
 966     }
 967 
 968     /**
 969      * Writes a <code>short</code> to the file as two bytes, high byte first.
 970      * The write starts at the current position of the file pointer.
 971      *
 972      * @param      v   a <code>short</code> to be written.
 973      * @exception  IOException  if an I/O error occurs.
 974      */
 975     public final void writeShort(int v) throws IOException {
 976         write((v >>> 8) & 0xFF);
 977         write((v >>> 0) & 0xFF);
 978         //written += 2;
 979     }
 980 
 981     /**
 982      * Writes a <code>char</code> to the file as a two-byte value, high
 983      * byte first. The write starts at the current position of the
 984      * file pointer.
 985      *
 986      * @param      v   a <code>char</code> value to be written.
 987      * @exception  IOException  if an I/O error occurs.
 988      */
 989     public final void writeChar(int v) throws IOException {
 990         write((v >>> 8) & 0xFF);
 991         write((v >>> 0) & 0xFF);
 992         //written += 2;
 993     }
 994 
 995     /**
 996      * Writes an <code>int</code> to the file as four bytes, high byte first.
 997      * The write starts at the current position of the file pointer.
 998      *
 999      * @param      v   an <code>int</code> to be written.
1000      * @exception  IOException  if an I/O error occurs.
1001      */
1002     public final void writeInt(int v) throws IOException {
1003         write((v >>> 24) & 0xFF);
1004         write((v >>> 16) & 0xFF);
1005         write((v >>>  8) & 0xFF);
1006         write((v >>>  0) & 0xFF);
1007         //written += 4;
1008     }
1009 
1010     /**
1011      * Writes a <code>long</code> to the file as eight bytes, high byte first.
1012      * The write starts at the current position of the file pointer.
1013      *
1014      * @param      v   a <code>long</code> to be written.
1015      * @exception  IOException  if an I/O error occurs.
1016      */
1017     public final void writeLong(long v) throws IOException {
1018         write((int)(v >>> 56) & 0xFF);
1019         write((int)(v >>> 48) & 0xFF);
1020         write((int)(v >>> 40) & 0xFF);
1021         write((int)(v >>> 32) & 0xFF);
1022         write((int)(v >>> 24) & 0xFF);
1023         write((int)(v >>> 16) & 0xFF);
1024         write((int)(v >>>  8) & 0xFF);
1025         write((int)(v >>>  0) & 0xFF);
1026         //written += 8;
1027     }
1028 
1029     /**
1030      * Converts the float argument to an <code>int</code> using the
1031      * <code>floatToIntBits</code> method in class <code>Float</code>,
1032      * and then writes that <code>int</code> value to the file as a
1033      * four-byte quantity, high byte first. The write starts at the
1034      * current position of the file pointer.
1035      *
1036      * @param      v   a <code>float</code> value to be written.
1037      * @exception  IOException  if an I/O error occurs.
1038      * @see        java.lang.Float#floatToIntBits(float)
1039      */
1040     public final void writeFloat(float v) throws IOException {
1041         writeInt(Float.floatToIntBits(v));
1042     }
1043 
1044     /**
1045      * Converts the double argument to a <code>long</code> using the
1046      * <code>doubleToLongBits</code> method in class <code>Double</code>,
1047      * and then writes that <code>long</code> value to the file as an
1048      * eight-byte quantity, high byte first. The write starts at the current
1049      * position of the file pointer.
1050      *
1051      * @param      v   a <code>double</code> value to be written.
1052      * @exception  IOException  if an I/O error occurs.
1053      * @see        java.lang.Double#doubleToLongBits(double)
1054      */
1055     public final void writeDouble(double v) throws IOException {
1056         writeLong(Double.doubleToLongBits(v));
1057     }
1058 
1059     /**
1060      * Writes the string to the file as a sequence of bytes. Each
1061      * character in the string is written out, in sequence, by discarding
1062      * its high eight bits. The write starts at the current position of
1063      * the file pointer.
1064      *
1065      * @param      s   a string of bytes to be written.
1066      * @exception  IOException  if an I/O error occurs.
1067      */
1068     public final void writeBytes(String s) throws IOException {
1069         int len = s.length();
1070         byte[] b = new byte[len];
1071         s.getBytes(0, len, b, 0);
1072         writeBytes(b, 0, len);
1073     }
1074 
1075     /**
1076      * Writes a string to the file as a sequence of characters. Each
1077      * character is written to the data output stream as if by the
1078      * <code>writeChar</code> method. The write starts at the current
1079      * position of the file pointer.
1080      *
1081      * @param      s   a <code>String</code> value to be written.
1082      * @exception  IOException  if an I/O error occurs.
1083      * @see        java.io.RandomAccessFile#writeChar(int)
1084      */
1085     public final void writeChars(String s) throws IOException {
1086         int clen = s.length();
1087         int blen = 2*clen;
1088         byte[] b = new byte[blen];
1089         char[] c = new char[clen];
1090         s.getChars(0, clen, c, 0);
1091         for (int i = 0, j = 0; i < clen; i++) {
1092             b[j++] = (byte)(c[i] >>> 8);
1093             b[j++] = (byte)(c[i] >>> 0);
1094         }
1095         writeBytes(b, 0, blen);
1096     }
1097 
1098     /**
1099      * Writes a string to the file using
1100      * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
1101      * encoding in a machine-independent manner.
1102      * <p>
1103      * First, two bytes are written to the file, starting at the
1104      * current file pointer, as if by the
1105      * <code>writeShort</code> method giving the number of bytes to
1106      * follow. This value is the number of bytes actually written out,
1107      * not the length of the string. Following the length, each character
1108      * of the string is output, in sequence, using the modified UTF-8 encoding
1109      * for each character.
1110      *
1111      * @param      str   a string to be written.
1112      * @exception  IOException  if an I/O error occurs.
1113      */
1114     public final void writeUTF(String str) throws IOException {
1115         DataOutputStream.writeUTF(str, this);
1116     }
1117 
1118     private static native void initIDs();
1119 
1120     private native void close0() throws IOException;
1121 
1122     static {
1123         initIDs();
1124     }
1125 }
--- EOF ---