RandomAccessFile.java 43.8 KB
Newer Older
D
duke 已提交
1
/*
2
 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
D
duke 已提交
3 4 5 6
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
7
 * published by the Free Software Foundation.  Oracle designates this
D
duke 已提交
8
 * particular file as subject to the "Classpath" exception as provided
9
 * by Oracle in the LICENSE file that accompanied this code.
D
duke 已提交
10 11 12 13 14 15 16 17 18 19 20
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
21 22 23
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
D
duke 已提交
24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
 */

package java.io;

import java.nio.channels.FileChannel;
import sun.nio.ch.FileChannelImpl;


/**
 * Instances of this class support both reading and writing to a
 * random access file. A random access file behaves like a large
 * array of bytes stored in the file system. There is a kind of cursor,
 * or index into the implied array, called the <em>file pointer</em>;
 * input operations read bytes starting at the file pointer and advance
 * the file pointer past the bytes read. If the random access file is
 * created in read/write mode, then output operations are also available;
 * output operations write bytes starting at the file pointer and advance
 * the file pointer past the bytes written. Output operations that write
 * past the current end of the implied array cause the array to be
 * extended. The file pointer can be read by the
44
 * {@code getFilePointer} method and set by the {@code seek}
D
duke 已提交
45 46 47 48
 * method.
 * <p>
 * It is generally true of all the reading routines in this class that
 * if end-of-file is reached before the desired number of bytes has been
49 50 51 52 53
 * read, an {@code EOFException} (which is a kind of
 * {@code IOException}) is thrown. If any byte cannot be read for
 * any reason other than end-of-file, an {@code IOException} other
 * than {@code EOFException} is thrown. In particular, an
 * {@code IOException} may be thrown if the stream has been closed.
D
duke 已提交
54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84
 *
 * @author  unascribed
 * @since   JDK1.0
 */

public class RandomAccessFile implements DataOutput, DataInput, Closeable {

    private FileDescriptor fd;
    private FileChannel channel = null;
    private boolean rw;

    private Object closeLock = new Object();
    private volatile boolean closed = false;

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

    /**
     * Creates a random access file stream to read from, and optionally
     * to write to, a file with the specified name. A new
     * {@link FileDescriptor} object is created to represent the
     * connection to the file.
     *
     * <p> The <tt>mode</tt> argument specifies the access mode with which the
     * file is to be opened.  The permitted values and their meanings are as
     * specified for the <a
     * href="#mode"><tt>RandomAccessFile(File,String)</tt></a> constructor.
     *
     * <p>
85 86
     * If there is a security manager, its {@code checkRead} method
     * is called with the {@code name} argument
D
duke 已提交
87 88
     * as its argument to see if read access to the file is allowed.
     * If the mode allows writing, the security manager's
89 90
     * {@code checkWrite} method
     * is also called with the {@code name} argument
D
duke 已提交
91 92 93 94 95 96 97 98 99 100 101 102 103 104 105
     * as its argument to see if write access to the file is allowed.
     *
     * @param      name   the system-dependent filename
     * @param      mode   the access <a href="#mode">mode</a>
     * @exception  IllegalArgumentException  if the mode argument is not equal
     *               to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
     *               <tt>"rwd"</tt>
     * @exception FileNotFoundException
     *            if the mode is <tt>"r"</tt> but the given string does not
     *            denote an existing regular file, or if the mode begins with
     *            <tt>"rw"</tt> but the given string does not denote an
     *            existing, writable regular file and a new regular file of
     *            that name cannot be created, or if some other error occurs
     *            while opening or creating the file
     * @exception  SecurityException         if a security manager exists and its
106
     *               {@code checkRead} method denies read access to the file
D
duke 已提交
107
     *               or the mode is "rw" and the security manager's
108
     *               {@code checkWrite} method denies write access to the file
D
duke 已提交
109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125
     * @see        java.lang.SecurityException
     * @see        java.lang.SecurityManager#checkRead(java.lang.String)
     * @see        java.lang.SecurityManager#checkWrite(java.lang.String)
     * @revised 1.4
     * @spec JSR-51
     */
    public RandomAccessFile(String name, String mode)
        throws FileNotFoundException
    {
        this(name != null ? new File(name) : null, mode);
    }

    /**
     * Creates a random access file stream to read from, and optionally to
     * write to, the file specified by the {@link File} argument.  A new {@link
     * FileDescriptor} object is created to represent this file connection.
     *
126
     * <p>The <a name="mode"><tt>mode</tt></a> argument specifies the access mode
D
duke 已提交
127 128 129
     * in which the file is to be opened.  The permitted values and their
     * meanings are:
     *
130
     * <table summary="Access mode permitted values and meanings">
D
duke 已提交
131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146
     * <tr><th><p align="left">Value</p></th><th><p align="left">Meaning</p></th></tr>
     * <tr><td valign="top"><tt>"r"</tt></td>
     *     <td> Open for reading only.  Invoking any of the <tt>write</tt>
     *     methods of the resulting object will cause an {@link
     *     java.io.IOException} to be thrown. </td></tr>
     * <tr><td valign="top"><tt>"rw"</tt></td>
     *     <td> Open for reading and writing.  If the file does not already
     *     exist then an attempt will be made to create it. </td></tr>
     * <tr><td valign="top"><tt>"rws"</tt></td>
     *     <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
     *     require that every update to the file's content or metadata be
     *     written synchronously to the underlying storage device.  </td></tr>
     * <tr><td valign="top"><tt>"rwd"&nbsp;&nbsp;</tt></td>
     *     <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
     *     require that every update to the file's content be written
     *     synchronously to the underlying storage device. </td></tr>
147
     * </table>
D
duke 已提交
148 149 150 151 152 153 154 155 156 157 158 159 160
     *
     * The <tt>"rws"</tt> and <tt>"rwd"</tt> modes work much like the {@link
     * java.nio.channels.FileChannel#force(boolean) force(boolean)} method of
     * the {@link java.nio.channels.FileChannel} class, passing arguments of
     * <tt>true</tt> and <tt>false</tt>, respectively, except that they always
     * apply to every I/O operation and are therefore often more efficient.  If
     * the file resides on a local storage device then when an invocation of a
     * method of this class returns it is guaranteed that all changes made to
     * the file by that invocation will have been written to that device.  This
     * is useful for ensuring that critical information is not lost in the
     * event of a system crash.  If the file does not reside on a local device
     * then no such guarantee is made.
     *
161
     * <p>The <tt>"rwd"</tt> mode can be used to reduce the number of I/O
D
duke 已提交
162 163 164 165 166
     * operations performed.  Using <tt>"rwd"</tt> only requires updates to the
     * file's content to be written to storage; using <tt>"rws"</tt> requires
     * updates to both the file's content and its metadata to be written, which
     * generally requires at least one more low-level I/O operation.
     *
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
D
duke 已提交
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
D
duke 已提交
171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187
     * also called with the path argument to see if write access to the file is
     * allowed.
     *
     * @param      file   the file object
     * @param      mode   the access mode, as described
     *                    <a href="#mode">above</a>
     * @exception  IllegalArgumentException  if the mode argument is not equal
     *               to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
     *               <tt>"rwd"</tt>
     * @exception FileNotFoundException
     *            if the mode is <tt>"r"</tt> but the given file object does
     *            not denote an existing regular file, or if the mode begins
     *            with <tt>"rw"</tt> but the given file object does not denote
     *            an existing, writable regular file and a new regular file of
     *            that name cannot be created, or if some other error occurs
     *            while opening or creating the file
     * @exception  SecurityException         if a security manager exists and its
188
     *               {@code checkRead} method denies read access to the file
D
duke 已提交
189
     *               or the mode is "rw" and the security manager's
190
     *               {@code checkWrite} method denies write access to the file
D
duke 已提交
191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230
     * @see        java.lang.SecurityManager#checkRead(java.lang.String)
     * @see        java.lang.SecurityManager#checkWrite(java.lang.String)
     * @see        java.nio.channels.FileChannel#force(boolean)
     * @revised 1.4
     * @spec JSR-51
     */
    public RandomAccessFile(File file, String mode)
        throws FileNotFoundException
    {
        String name = (file != null ? file.getPath() : null);
        int imode = -1;
        if (mode.equals("r"))
            imode = O_RDONLY;
        else if (mode.startsWith("rw")) {
            imode = O_RDWR;
            rw = true;
            if (mode.length() > 2) {
                if (mode.equals("rws"))
                    imode |= O_SYNC;
                else if (mode.equals("rwd"))
                    imode |= O_DSYNC;
                else
                    imode = -1;
            }
        }
        if (imode < 0)
            throw new IllegalArgumentException("Illegal mode \"" + mode
                                               + "\" must be one of "
                                               + "\"r\", \"rw\", \"rws\","
                                               + " or \"rwd\"");
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkRead(name);
            if (rw) {
                security.checkWrite(name);
            }
        }
        if (name == null) {
            throw new NullPointerException();
        }
231 232 233
        if (file.isInvalid()) {
            throw new FileNotFoundException("Invalid file path");
        }
D
duke 已提交
234
        fd = new FileDescriptor();
235
        fd.attach(this);
D
duke 已提交
236 237 238 239 240
        open(name, imode);
    }

    /**
     * Returns the opaque file descriptor object associated with this
241
     * stream.
D
duke 已提交
242 243 244 245 246 247
     *
     * @return     the file descriptor object associated with this stream.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FileDescriptor
     */
    public final FileDescriptor getFD() throws IOException {
248 249 250
        if (fd != null) {
            return fd;
        }
D
duke 已提交
251 252 253 254 255 256 257 258
        throw new IOException();
    }

    /**
     * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
     * object associated with this file.
     *
     * <p> The {@link java.nio.channels.FileChannel#position()
259
     * position} of the returned channel will always be equal to
D
duke 已提交
260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282
     * this object's file-pointer offset as returned by the {@link
     * #getFilePointer getFilePointer} method.  Changing this object's
     * file-pointer offset, whether explicitly or by reading or writing bytes,
     * will change the position of the channel, and vice versa.  Changing the
     * file's length via this object will change the length seen via the file
     * channel, and vice versa.
     *
     * @return  the file channel associated with this file
     *
     * @since 1.4
     * @spec JSR-51
     */
    public final FileChannel getChannel() {
        synchronized (this) {
            if (channel == null) {
                channel = FileChannelImpl.open(fd, true, rw, this);
            }
            return channel;
        }
    }

    /**
     * Opens a file and returns the file descriptor.  The file is
283
     * opened in read-write mode if the O_RDWR bit in {@code mode}
D
duke 已提交
284
     * is true, else the file is opened as read-only.
285
     * If the {@code name} refers to a directory, an IOException
D
duke 已提交
286 287 288 289 290 291 292 293 294 295 296 297 298
     * is thrown.
     *
     * @param name the name of the file
     * @param mode the mode flags, a combination of the O_ constants
     *             defined above
     */
    private native void open(String name, int mode)
        throws FileNotFoundException;

    // 'Read' primitives

    /**
     * Reads a byte of data from this file. The byte is returned as an
299
     * integer in the range 0 to 255 ({@code 0x00-0x0ff}). This
D
duke 已提交
300 301
     * method blocks if no input is yet available.
     * <p>
302 303
     * Although {@code RandomAccessFile} is not a subclass of
     * {@code InputStream}, this method behaves in exactly the same
D
duke 已提交
304
     * way as the {@link InputStream#read()} method of
305
     * {@code InputStream}.
D
duke 已提交
306
     *
307
     * @return     the next byte of data, or {@code -1} if the end of the
D
duke 已提交
308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323
     *             file has been reached.
     * @exception  IOException  if an I/O error occurs. Not thrown if
     *                          end-of-file has been reached.
     */
    public native int read() throws IOException;

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

    /**
324
     * Reads up to {@code len} bytes of data from this file into an
D
duke 已提交
325 326 327
     * array of bytes. This method blocks until at least one byte of input
     * is available.
     * <p>
328 329
     * Although {@code RandomAccessFile} is not a subclass of
     * {@code InputStream}, this method behaves in exactly the
D
duke 已提交
330
     * same way as the {@link InputStream#read(byte[], int, int)} method of
331
     * {@code InputStream}.
D
duke 已提交
332 333
     *
     * @param      b     the buffer into which the data is read.
334
     * @param      off   the start offset in array {@code b}
D
duke 已提交
335 336 337
     *                   at which the data is written.
     * @param      len   the maximum number of bytes read.
     * @return     the total number of bytes read into the buffer, or
338
     *             {@code -1} if there is no more data because the end of
D
duke 已提交
339 340 341 342
     *             the file has been reached.
     * @exception  IOException If the first byte cannot be read for any reason
     * other than end of file, or if the random access file has been closed, or if
     * some other I/O error occurs.
343 344 345 346
     * @exception  NullPointerException If {@code b} is {@code null}.
     * @exception  IndexOutOfBoundsException If {@code off} is negative,
     * {@code len} is negative, or {@code len} is greater than
     * {@code b.length - off}
D
duke 已提交
347 348 349 350 351 352
     */
    public int read(byte b[], int off, int len) throws IOException {
        return readBytes(b, off, len);
    }

    /**
353
     * Reads up to {@code b.length} bytes of data from this file
D
duke 已提交
354 355 356
     * into an array of bytes. This method blocks until at least one byte
     * of input is available.
     * <p>
357 358
     * Although {@code RandomAccessFile} is not a subclass of
     * {@code InputStream}, this method behaves in exactly the
D
duke 已提交
359
     * same way as the {@link InputStream#read(byte[])} method of
360
     * {@code InputStream}.
D
duke 已提交
361 362 363
     *
     * @param      b   the buffer into which the data is read.
     * @return     the total number of bytes read into the buffer, or
364
     *             {@code -1} if there is no more data because the end of
D
duke 已提交
365 366 367 368
     *             this file has been reached.
     * @exception  IOException If the first byte cannot be read for any reason
     * other than end of file, or if the random access file has been closed, or if
     * some other I/O error occurs.
369
     * @exception  NullPointerException If {@code b} is {@code null}.
D
duke 已提交
370 371 372 373 374 375
     */
    public int read(byte b[]) throws IOException {
        return readBytes(b, 0, b.length);
    }

    /**
376
     * Reads {@code b.length} bytes from this file into the byte
D
duke 已提交
377 378 379 380 381 382 383 384 385 386 387 388 389 390 391
     * array, starting at the current file pointer. This method reads
     * repeatedly from the file until the requested number of bytes are
     * read. This method blocks until the requested number of bytes are
     * read, the end of the stream is detected, or an exception is thrown.
     *
     * @param      b   the buffer into which the data is read.
     * @exception  EOFException  if this file reaches the end before reading
     *               all the bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final void readFully(byte b[]) throws IOException {
        readFully(b, 0, b.length);
    }

    /**
392
     * Reads exactly {@code len} bytes from this file into the byte
D
duke 已提交
393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415
     * array, starting at the current file pointer. This method reads
     * repeatedly from the file until the requested number of bytes are
     * read. This method blocks until the requested number of bytes are
     * read, the end of the stream is detected, or an exception is thrown.
     *
     * @param      b     the buffer into which the data is read.
     * @param      off   the start offset of the data.
     * @param      len   the number of bytes to read.
     * @exception  EOFException  if this file reaches the end before reading
     *               all the bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final void readFully(byte b[], int off, int len) throws IOException {
        int n = 0;
        do {
            int count = this.read(b, off + n, len - n);
            if (count < 0)
                throw new EOFException();
            n += count;
        } while (n < len);
    }

    /**
416
     * Attempts to skip over {@code n} bytes of input discarding the
D
duke 已提交
417 418 419 420 421
     * skipped bytes.
     * <p>
     *
     * This method may skip over some smaller number of bytes, possibly zero.
     * This may result from any of a number of conditions; reaching end of
422 423 424
     * file before {@code n} bytes have been skipped is only one
     * possibility. This method never throws an {@code EOFException}.
     * The actual number of bytes skipped is returned.  If {@code n}
D
duke 已提交
425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456
     * is negative, no bytes are skipped.
     *
     * @param      n   the number of bytes to be skipped.
     * @return     the actual number of bytes skipped.
     * @exception  IOException  if an I/O error occurs.
     */
    public int skipBytes(int n) throws IOException {
        long pos;
        long len;
        long newpos;

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

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

    // 'Write' primitives

    /**
     * Writes the specified byte to this file. The write starts at
     * the current file pointer.
     *
457
     * @param      b   the {@code byte} to be written.
D
duke 已提交
458 459 460 461 462 463 464 465 466 467 468 469 470 471 472
     * @exception  IOException  if an I/O error occurs.
     */
    public native void write(int b) throws IOException;

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

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

    /**
473
     * Writes {@code b.length} bytes from the specified byte array
D
duke 已提交
474 475 476 477 478 479 480 481 482 483
     * to this file, starting at the current file pointer.
     *
     * @param      b   the data.
     * @exception  IOException  if an I/O error occurs.
     */
    public void write(byte b[]) throws IOException {
        writeBytes(b, 0, b.length);
    }

    /**
484 485
     * Writes {@code len} bytes from the specified byte array
     * starting at offset {@code off} to this file.
D
duke 已提交
486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517
     *
     * @param      b     the data.
     * @param      off   the start offset in the data.
     * @param      len   the number of bytes to write.
     * @exception  IOException  if an I/O error occurs.
     */
    public void write(byte b[], int off, int len) throws IOException {
        writeBytes(b, off, len);
    }

    // 'Random access' stuff

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

    /**
     * Sets the file-pointer offset, measured from the beginning of this
     * file, at which the next read or write occurs.  The offset may be
     * set beyond the end of the file. Setting the offset beyond the end
     * of the file does not change the file length.  The file length will
     * change only by writing after the offset has been set beyond the end
     * of the file.
     *
     * @param      pos   the offset position, measured in bytes from the
     *                   beginning of the file, at which to set the file
     *                   pointer.
518 519
     * @exception  IOException  if {@code pos} is less than
     *                          {@code 0} or if an I/O error occurs.
D
duke 已提交
520 521 522 523 524 525 526 527 528 529 530 531 532 533 534
     */
    public native void seek(long pos) throws IOException;

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

    /**
     * Sets the length of this file.
     *
     * <p> If the present length of the file as returned by the
535
     * {@code length} method is greater than the {@code newLength}
D
duke 已提交
536
     * argument then the file will be truncated.  In this case, if the file
537 538 539
     * offset as returned by the {@code getFilePointer} method is greater
     * than {@code newLength} then after this method returns the offset
     * will be equal to {@code newLength}.
D
duke 已提交
540 541
     *
     * <p> If the present length of the file as returned by the
542
     * {@code length} method is smaller than the {@code newLength}
D
duke 已提交
543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576
     * argument then the file will be extended.  In this case, the contents of
     * the extended portion of the file are not defined.
     *
     * @param      newLength    The desired length of the file
     * @exception  IOException  If an I/O error occurs
     * @since      1.2
     */
    public native void setLength(long newLength) throws IOException;

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

577 578 579 580 581
        fd.closeAll(new Closeable() {
            public void close() throws IOException {
               close0();
           }
        });
D
duke 已提交
582 583 584 585 586 587 588 589
    }

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

    /**
590
     * Reads a {@code boolean} from this file. This method reads a
D
duke 已提交
591
     * single byte from the file, starting at the current file pointer.
592 593
     * A value of {@code 0} represents
     * {@code false}. Any other value represents {@code true}.
D
duke 已提交
594 595 596
     * This method blocks until the byte is read, the end of the stream
     * is detected, or an exception is thrown.
     *
597
     * @return     the {@code boolean} value read.
D
duke 已提交
598 599 600 601 602 603 604 605 606 607 608 609 610
     * @exception  EOFException  if this file has reached the end.
     * @exception  IOException   if an I/O error occurs.
     */
    public final boolean readBoolean() throws IOException {
        int ch = this.read();
        if (ch < 0)
            throw new EOFException();
        return (ch != 0);
    }

    /**
     * Reads a signed eight-bit value from this file. This method reads a
     * byte from the file, starting from the current file pointer.
611
     * If the byte read is {@code b}, where
D
duke 已提交
612 613 614 615 616 617 618 619 620 621
     * <code>0&nbsp;&lt;=&nbsp;b&nbsp;&lt;=&nbsp;255</code>,
     * then the result is:
     * <blockquote><pre>
     *     (byte)(b)
     * </pre></blockquote>
     * <p>
     * This method blocks until the byte is read, the end of the stream
     * is detected, or an exception is thrown.
     *
     * @return     the next byte of this file as a signed eight-bit
622
     *             {@code byte}.
D
duke 已提交
623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656
     * @exception  EOFException  if this file has reached the end.
     * @exception  IOException   if an I/O error occurs.
     */
    public final byte readByte() throws IOException {
        int ch = this.read();
        if (ch < 0)
            throw new EOFException();
        return (byte)(ch);
    }

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

    /**
     * Reads a signed 16-bit number from this file. The method reads two
     * bytes from this file, starting at the current file pointer.
     * If the two bytes read, in order, are
657 658
     * {@code b1} and {@code b2}, where each of the two values is
     * between {@code 0} and {@code 255}, inclusive, then the
D
duke 已提交
659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684
     * result is equal to:
     * <blockquote><pre>
     *     (short)((b1 &lt;&lt; 8) | b2)
     * </pre></blockquote>
     * <p>
     * This method blocks until the two bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next two bytes of this file, interpreted as a signed
     *             16-bit number.
     * @exception  EOFException  if this file reaches the end before reading
     *               two bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final short readShort() throws IOException {
        int ch1 = this.read();
        int ch2 = this.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (short)((ch1 << 8) + (ch2 << 0));
    }

    /**
     * Reads an unsigned 16-bit number from this file. This method reads
     * two bytes from the file, starting at the current file pointer.
     * If the bytes read, in order, are
685
     * {@code b1} and {@code b2}, where
D
duke 已提交
686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712
     * <code>0&nbsp;&lt;=&nbsp;b1, b2&nbsp;&lt;=&nbsp;255</code>,
     * then the result is equal to:
     * <blockquote><pre>
     *     (b1 &lt;&lt; 8) | b2
     * </pre></blockquote>
     * <p>
     * This method blocks until the two bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next two bytes of this file, interpreted as an unsigned
     *             16-bit integer.
     * @exception  EOFException  if this file reaches the end before reading
     *               two bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final int readUnsignedShort() throws IOException {
        int ch1 = this.read();
        int ch2 = this.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (ch1 << 8) + (ch2 << 0);
    }

    /**
     * Reads a character from this file. This method reads two
     * bytes from the file, starting at the current file pointer.
     * If the bytes read, in order, are
713
     * {@code b1} and {@code b2}, where
D
duke 已提交
714 715 716 717 718 719 720 721 722 723
     * <code>0&nbsp;&lt;=&nbsp;b1,&nbsp;b2&nbsp;&lt;=&nbsp;255</code>,
     * then the result is equal to:
     * <blockquote><pre>
     *     (char)((b1 &lt;&lt; 8) | b2)
     * </pre></blockquote>
     * <p>
     * This method blocks until the two bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next two bytes of this file, interpreted as a
724
     *                  {@code char}.
D
duke 已提交
725 726 727 728 729 730 731 732 733 734 735 736 737 738 739
     * @exception  EOFException  if this file reaches the end before reading
     *               two bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final char readChar() throws IOException {
        int ch1 = this.read();
        int ch2 = this.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (char)((ch1 << 8) + (ch2 << 0));
    }

    /**
     * Reads a signed 32-bit integer from this file. This method reads 4
     * bytes from the file, starting at the current file pointer.
740 741
     * If the bytes read, in order, are {@code b1},
     * {@code b2}, {@code b3}, and {@code b4}, where
D
duke 已提交
742 743 744 745 746 747 748 749 750 751
     * <code>0&nbsp;&lt;=&nbsp;b1, b2, b3, b4&nbsp;&lt;=&nbsp;255</code>,
     * then the result is equal to:
     * <blockquote><pre>
     *     (b1 &lt;&lt; 24) | (b2 &lt;&lt; 16) + (b3 &lt;&lt; 8) + b4
     * </pre></blockquote>
     * <p>
     * This method blocks until the four bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next four bytes of this file, interpreted as an
752
     *             {@code int}.
D
duke 已提交
753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770
     * @exception  EOFException  if this file reaches the end before reading
     *               four bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final int readInt() throws IOException {
        int ch1 = this.read();
        int ch2 = this.read();
        int ch3 = this.read();
        int ch4 = this.read();
        if ((ch1 | ch2 | ch3 | ch4) < 0)
            throw new EOFException();
        return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
    }

    /**
     * Reads a signed 64-bit integer from this file. This method reads eight
     * bytes from the file, starting at the current file pointer.
     * If the bytes read, in order, are
771 772 773
     * {@code b1}, {@code b2}, {@code b3},
     * {@code b4}, {@code b5}, {@code b6},
     * {@code b7}, and {@code b8,} where:
D
duke 已提交
774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789
     * <blockquote><pre>
     *     0 &lt;= b1, b2, b3, b4, b5, b6, b7, b8 &lt;=255,
     * </pre></blockquote>
     * <p>
     * then the result is equal to:
     * <p><blockquote><pre>
     *     ((long)b1 &lt;&lt; 56) + ((long)b2 &lt;&lt; 48)
     *     + ((long)b3 &lt;&lt; 40) + ((long)b4 &lt;&lt; 32)
     *     + ((long)b5 &lt;&lt; 24) + ((long)b6 &lt;&lt; 16)
     *     + ((long)b7 &lt;&lt; 8) + b8
     * </pre></blockquote>
     * <p>
     * This method blocks until the eight bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next eight bytes of this file, interpreted as a
790
     *             {@code long}.
D
duke 已提交
791 792 793 794 795 796 797 798 799
     * @exception  EOFException  if this file reaches the end before reading
     *               eight bytes.
     * @exception  IOException   if an I/O error occurs.
     */
    public final long readLong() throws IOException {
        return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
    }

    /**
800 801 802 803 804 805
     * Reads a {@code float} from this file. This method reads an
     * {@code int} value, starting at the current file pointer,
     * as if by the {@code readInt} method
     * and then converts that {@code int} to a {@code float}
     * using the {@code intBitsToFloat} method in class
     * {@code Float}.
D
duke 已提交
806 807 808 809 810
     * <p>
     * This method blocks until the four bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next four bytes of this file, interpreted as a
811
     *             {@code float}.
D
duke 已提交
812 813 814 815 816 817 818 819 820 821 822
     * @exception  EOFException  if this file reaches the end before reading
     *             four bytes.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.RandomAccessFile#readInt()
     * @see        java.lang.Float#intBitsToFloat(int)
     */
    public final float readFloat() throws IOException {
        return Float.intBitsToFloat(readInt());
    }

    /**
823 824 825 826 827 828
     * Reads a {@code double} from this file. This method reads a
     * {@code long} value, starting at the current file pointer,
     * as if by the {@code readLong} method
     * and then converts that {@code long} to a {@code double}
     * using the {@code longBitsToDouble} method in
     * class {@code Double}.
D
duke 已提交
829 830 831 832 833
     * <p>
     * This method blocks until the eight bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     the next eight bytes of this file, interpreted as a
834
     *             {@code double}.
D
duke 已提交
835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854
     * @exception  EOFException  if this file reaches the end before reading
     *             eight bytes.
     * @exception  IOException   if an I/O error occurs.
     * @see        java.io.RandomAccessFile#readLong()
     * @see        java.lang.Double#longBitsToDouble(long)
     */
    public final double readDouble() throws IOException {
        return Double.longBitsToDouble(readLong());
    }

    /**
     * Reads the next line of text from this file.  This method successively
     * reads bytes from the file, starting at the current file pointer,
     * until it reaches a line terminator or the end
     * of the file.  Each byte is converted into a character by taking the
     * byte's value for the lower eight bits of the character and setting the
     * high eight bits of the character to zero.  This method does not,
     * therefore, support the full Unicode character set.
     *
     * <p> A line of text is terminated by a carriage-return character
855
     * ({@code '\u005Cr'}), a newline character ({@code '\u005Cn'}), a
D
duke 已提交
856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906
     * carriage-return character immediately followed by a newline character,
     * or the end of the file.  Line-terminating characters are discarded and
     * are not included as part of the string returned.
     *
     * <p> This method blocks until a newline character is read, a carriage
     * return and the byte following it are read (to see if it is a newline),
     * the end of the file is reached, or an exception is thrown.
     *
     * @return     the next line of text from this file, or null if end
     *             of file is encountered before even one byte is read.
     * @exception  IOException  if an I/O error occurs.
     */

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

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

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

    /**
     * Reads in a string from this file. The string has been encoded
     * using a
     * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
     * format.
     * <p>
     * The first two bytes are read, starting from the current file
     * pointer, as if by
907
     * {@code readUnsignedShort}. This value gives the number of
D
duke 已提交
908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928
     * following bytes that are in the encoded string, not
     * the length of the resulting string. The following bytes are then
     * interpreted as bytes encoding characters in the modified UTF-8 format
     * and are converted into characters.
     * <p>
     * This method blocks until all the bytes are read, the end of the
     * stream is detected, or an exception is thrown.
     *
     * @return     a Unicode string.
     * @exception  EOFException            if this file reaches the end before
     *               reading all the bytes.
     * @exception  IOException             if an I/O error occurs.
     * @exception  UTFDataFormatException  if the bytes do not represent
     *               valid modified UTF-8 encoding of a Unicode string.
     * @see        java.io.RandomAccessFile#readUnsignedShort()
     */
    public final String readUTF() throws IOException {
        return DataInputStream.readUTF(this);
    }

    /**
929 930 931 932
     * Writes a {@code boolean} to the file as a one-byte value. The
     * value {@code true} is written out as the value
     * {@code (byte)1}; the value {@code false} is written out
     * as the value {@code (byte)0}. The write starts at
D
duke 已提交
933 934
     * the current position of the file pointer.
     *
935
     * @param      v   a {@code boolean} value to be written.
D
duke 已提交
936 937 938 939 940 941 942 943
     * @exception  IOException  if an I/O error occurs.
     */
    public final void writeBoolean(boolean v) throws IOException {
        write(v ? 1 : 0);
        //written++;
    }

    /**
944
     * Writes a {@code byte} to the file as a one-byte value. The
D
duke 已提交
945 946
     * write starts at the current position of the file pointer.
     *
947
     * @param      v   a {@code byte} value to be written.
D
duke 已提交
948 949 950 951 952 953 954 955
     * @exception  IOException  if an I/O error occurs.
     */
    public final void writeByte(int v) throws IOException {
        write(v);
        //written++;
    }

    /**
956
     * Writes a {@code short} to the file as two bytes, high byte first.
D
duke 已提交
957 958
     * The write starts at the current position of the file pointer.
     *
959
     * @param      v   a {@code short} to be written.
D
duke 已提交
960 961 962 963 964 965 966 967 968
     * @exception  IOException  if an I/O error occurs.
     */
    public final void writeShort(int v) throws IOException {
        write((v >>> 8) & 0xFF);
        write((v >>> 0) & 0xFF);
        //written += 2;
    }

    /**
969
     * Writes a {@code char} to the file as a two-byte value, high
D
duke 已提交
970 971 972
     * byte first. The write starts at the current position of the
     * file pointer.
     *
973
     * @param      v   a {@code char} value to be written.
D
duke 已提交
974 975 976 977 978 979 980 981 982
     * @exception  IOException  if an I/O error occurs.
     */
    public final void writeChar(int v) throws IOException {
        write((v >>> 8) & 0xFF);
        write((v >>> 0) & 0xFF);
        //written += 2;
    }

    /**
983
     * Writes an {@code int} to the file as four bytes, high byte first.
D
duke 已提交
984 985
     * The write starts at the current position of the file pointer.
     *
986
     * @param      v   an {@code int} to be written.
D
duke 已提交
987 988 989 990 991 992 993 994 995 996 997
     * @exception  IOException  if an I/O error occurs.
     */
    public final void writeInt(int v) throws IOException {
        write((v >>> 24) & 0xFF);
        write((v >>> 16) & 0xFF);
        write((v >>>  8) & 0xFF);
        write((v >>>  0) & 0xFF);
        //written += 4;
    }

    /**
998
     * Writes a {@code long} to the file as eight bytes, high byte first.
D
duke 已提交
999 1000
     * The write starts at the current position of the file pointer.
     *
1001
     * @param      v   a {@code long} to be written.
D
duke 已提交
1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016
     * @exception  IOException  if an I/O error occurs.
     */
    public final void writeLong(long v) throws IOException {
        write((int)(v >>> 56) & 0xFF);
        write((int)(v >>> 48) & 0xFF);
        write((int)(v >>> 40) & 0xFF);
        write((int)(v >>> 32) & 0xFF);
        write((int)(v >>> 24) & 0xFF);
        write((int)(v >>> 16) & 0xFF);
        write((int)(v >>>  8) & 0xFF);
        write((int)(v >>>  0) & 0xFF);
        //written += 8;
    }

    /**
1017 1018 1019
     * Converts the float argument to an {@code int} using the
     * {@code floatToIntBits} method in class {@code Float},
     * and then writes that {@code int} value to the file as a
D
duke 已提交
1020 1021 1022
     * four-byte quantity, high byte first. The write starts at the
     * current position of the file pointer.
     *
1023
     * @param      v   a {@code float} value to be written.
D
duke 已提交
1024 1025 1026 1027 1028 1029 1030 1031
     * @exception  IOException  if an I/O error occurs.
     * @see        java.lang.Float#floatToIntBits(float)
     */
    public final void writeFloat(float v) throws IOException {
        writeInt(Float.floatToIntBits(v));
    }

    /**
1032 1033 1034
     * Converts the double argument to a {@code long} using the
     * {@code doubleToLongBits} method in class {@code Double},
     * and then writes that {@code long} value to the file as an
D
duke 已提交
1035 1036 1037
     * eight-byte quantity, high byte first. The write starts at the current
     * position of the file pointer.
     *
1038
     * @param      v   a {@code double} value to be written.
D
duke 已提交
1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054
     * @exception  IOException  if an I/O error occurs.
     * @see        java.lang.Double#doubleToLongBits(double)
     */
    public final void writeDouble(double v) throws IOException {
        writeLong(Double.doubleToLongBits(v));
    }

    /**
     * Writes the string to the file as a sequence of bytes. Each
     * character in the string is written out, in sequence, by discarding
     * its high eight bits. The write starts at the current position of
     * the file pointer.
     *
     * @param      s   a string of bytes to be written.
     * @exception  IOException  if an I/O error occurs.
     */
1055
    @SuppressWarnings("deprecation")
D
duke 已提交
1056 1057 1058 1059 1060 1061 1062 1063 1064 1065
    public final void writeBytes(String s) throws IOException {
        int len = s.length();
        byte[] b = new byte[len];
        s.getBytes(0, len, b, 0);
        writeBytes(b, 0, len);
    }

    /**
     * Writes a string to the file as a sequence of characters. Each
     * character is written to the data output stream as if by the
1066
     * {@code writeChar} method. The write starts at the current
D
duke 已提交
1067 1068
     * position of the file pointer.
     *
1069
     * @param      s   a {@code String} value to be written.
D
duke 已提交
1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.RandomAccessFile#writeChar(int)
     */
    public final void writeChars(String s) throws IOException {
        int clen = s.length();
        int blen = 2*clen;
        byte[] b = new byte[blen];
        char[] c = new char[clen];
        s.getChars(0, clen, c, 0);
        for (int i = 0, j = 0; i < clen; i++) {
            b[j++] = (byte)(c[i] >>> 8);
            b[j++] = (byte)(c[i] >>> 0);
        }
        writeBytes(b, 0, blen);
    }

    /**
     * Writes a string to the file using
     * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
     * encoding in a machine-independent manner.
     * <p>
     * First, two bytes are written to the file, starting at the
     * current file pointer, as if by the
1093
     * {@code writeShort} method giving the number of bytes to
D
duke 已提交
1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113
     * follow. This value is the number of bytes actually written out,
     * not the length of the string. Following the length, each character
     * of the string is output, in sequence, using the modified UTF-8 encoding
     * for each character.
     *
     * @param      str   a string to be written.
     * @exception  IOException  if an I/O error occurs.
     */
    public final void writeUTF(String str) throws IOException {
        DataOutputStream.writeUTF(str, this);
    }

    private static native void initIDs();

    private native void close0() throws IOException;

    static {
        initIDs();
    }
}