1 /* 2 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.io; 27 28 import java.nio.channels.FileChannel; 29 import sun.nio.ch.FileChannelImpl; 30 31 32 /** 33 * Instances of this class support both reading and writing to a 34 * random access file. A random access file behaves like a large 35 * array of bytes stored in the file system. There is a kind of cursor, 36 * or index into the implied array, called the <em>file pointer</em>; 37 * input operations read bytes starting at the file pointer and advance 38 * the file pointer past the bytes read. If the random access file is 39 * created in read/write mode, then output operations are also available; 40 * output operations write bytes starting at the file pointer and advance 41 * the file pointer past the bytes written. Output operations that write 42 * past the current end of the implied array cause the array to be 43 * extended. The file pointer can be read by the 44 * {@code getFilePointer} method and set by the {@code seek} 45 * method. 46 * <p> 47 * It is generally true of all the reading routines in this class that 48 * if end-of-file is reached before the desired number of bytes has been 49 * read, an {@code EOFException} (which is a kind of 50 * {@code IOException}) is thrown. If any byte cannot be read for 51 * any reason other than end-of-file, an {@code IOException} other 52 * than {@code EOFException} is thrown. In particular, an 53 * {@code IOException} may be thrown if the stream has been closed. 54 * 55 * @author unascribed 56 * @since JDK1.0 57 */ 58 59 public class RandomAccessFile implements DataOutput, DataInput, Closeable { 60 61 private FileDescriptor fd; 62 private FileChannel channel = null; 63 private boolean rw; 64 65 private Object closeLock = new Object(); 66 private volatile boolean closed = false; 67 68 private static final int O_RDONLY = 1; 69 private static final int O_RDWR = 2; 70 private static final int O_SYNC = 4; 71 private static final int O_DSYNC = 8; 72 73 /** 74 * Creates a random access file stream to read from, and optionally 75 * to write to, a file with the specified name. A new 76 * {@link FileDescriptor} object is created to represent the 77 * connection to the file. 78 * 79 * <p> The <tt>mode</tt> argument specifies the access mode with which the 80 * file is to be opened. The permitted values and their meanings are as 81 * specified for the <a 82 * href="#mode"><tt>RandomAccessFile(File,String)</tt></a> constructor. 83 * 84 * <p> 85 * If there is a security manager, its {@code checkRead} method 86 * is called with the {@code name} argument 87 * as its argument to see if read access to the file is allowed. 88 * If the mode allows writing, the security manager's 89 * {@code checkWrite} method 90 * is also called with the {@code name} argument 91 * as its argument to see if write access to the file is allowed. 92 * 93 * @param name the system-dependent filename 94 * @param mode the access <a href="#mode">mode</a> 95 * @exception IllegalArgumentException if the mode argument is not equal 96 * to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or 97 * <tt>"rwd"</tt> 98 * @exception FileNotFoundException 99 * if the mode is <tt>"r"</tt> but the given string does not 100 * denote an existing regular file, or if the mode begins with 101 * <tt>"rw"</tt> but the given string does not denote an 102 * existing, writable regular file and a new regular file of 103 * that name cannot be created, or if some other error occurs 104 * while opening or creating the file 105 * @exception SecurityException if a security manager exists and its 106 * {@code checkRead} method denies read access to the file 107 * or the mode is "rw" and the security manager's 108 * {@code checkWrite} method denies write access to the file 109 * @see java.lang.SecurityException 110 * @see java.lang.SecurityManager#checkRead(java.lang.String) 111 * @see java.lang.SecurityManager#checkWrite(java.lang.String) 112 * @revised 1.4 113 * @spec JSR-51 114 */ 115 public RandomAccessFile(String name, String mode) 116 throws FileNotFoundException 117 { 118 this(name != null ? new File(name) : null, mode); 119 } 120 121 /** 122 * Creates a random access file stream to read from, and optionally to 123 * write to, the file specified by the {@link File} argument. A new {@link 124 * FileDescriptor} object is created to represent this file connection. 125 * 126 * <p>The <a name="mode"><tt>mode</tt></a> argument specifies the access mode 127 * in which the file is to be opened. The permitted values and their 128 * meanings are: 129 * 130 * <table summary="Access mode permitted values and meanings"> 131 * <tr><th align="left">Value</th><th align="left">Meaning</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" </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> 148 * 149 * The <tt>"rws"</tt> and <tt>"rwd"</tt> modes work much like the {@link 150 * java.nio.channels.FileChannel#force(boolean) force(boolean)} method of 151 * the {@link java.nio.channels.FileChannel} class, passing arguments of 152 * <tt>true</tt> and <tt>false</tt>, respectively, except that they always 153 * apply to every I/O operation and are therefore often more efficient. If 154 * the file resides on a local storage device then when an invocation of a 155 * method of this class returns it is guaranteed that all changes made to 156 * the file by that invocation will have been written to that device. This 157 * is useful for ensuring that critical information is not lost in the 158 * event of a system crash. If the file does not reside on a local device 159 * then no such guarantee is made. 160 * 161 * <p>The <tt>"rwd"</tt> mode can be used to reduce the number of I/O 162 * operations performed. Using <tt>"rwd"</tt> only requires updates to the 163 * file's content to be written to storage; using <tt>"rws"</tt> requires 164 * updates to both the file's content and its metadata to be written, which 165 * generally requires at least one more low-level I/O operation. 166 * 167 * <p>If there is a security manager, its {@code checkRead} method is 168 * called with the pathname of the {@code file} argument as its 169 * argument to see if read access to the file is allowed. If the mode 170 * allows writing, the security manager's {@code checkWrite} method is 171 * also called with the path argument to see if write access to the file is 172 * allowed. 173 * 174 * @param file the file object 175 * @param mode the access mode, as described 176 * <a href="#mode">above</a> 177 * @exception IllegalArgumentException if the mode argument is not equal 178 * to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or 179 * <tt>"rwd"</tt> 180 * @exception FileNotFoundException 181 * if the mode is <tt>"r"</tt> but the given file object does 182 * not denote an existing regular file, or if the mode begins 183 * with <tt>"rw"</tt> but the given file object does not denote 184 * an existing, writable regular file and a new regular file of 185 * that name cannot be created, or if some other error occurs 186 * while opening or creating the file 187 * @exception SecurityException if a security manager exists and its 188 * {@code checkRead} method denies read access to the file 189 * or the mode is "rw" and the security manager's 190 * {@code checkWrite} method denies write access to the file 191 * @see java.lang.SecurityManager#checkRead(java.lang.String) 192 * @see java.lang.SecurityManager#checkWrite(java.lang.String) 193 * @see java.nio.channels.FileChannel#force(boolean) 194 * @revised 1.4 195 * @spec JSR-51 196 */ 197 public RandomAccessFile(File file, String mode) 198 throws FileNotFoundException 199 { 200 String name = (file != null ? file.getPath() : null); 201 int imode = -1; 202 if (mode.equals("r")) 203 imode = O_RDONLY; 204 else if (mode.startsWith("rw")) { 205 imode = O_RDWR; 206 rw = true; 207 if (mode.length() > 2) { 208 if (mode.equals("rws")) 209 imode |= O_SYNC; 210 else if (mode.equals("rwd")) 211 imode |= O_DSYNC; 212 else 213 imode = -1; 214 } 215 } 216 if (imode < 0) 217 throw new IllegalArgumentException("Illegal mode \"" + mode 218 + "\" must be one of " 219 + "\"r\", \"rw\", \"rws\"," 220 + " or \"rwd\""); 221 SecurityManager security = System.getSecurityManager(); 222 if (security != null) { 223 security.checkRead(name); 224 if (rw) { 225 security.checkWrite(name); 226 } 227 } 228 if (name == null) { 229 throw new NullPointerException(); 230 } 231 if (file.isInvalid()) { 232 throw new FileNotFoundException("Invalid file path"); 233 } 234 fd = new FileDescriptor(); 235 fd.attach(this); 236 open(name, imode); 237 } 238 239 /** 240 * Returns the opaque file descriptor object associated with this 241 * stream. 242 * 243 * @return the file descriptor object associated with this stream. 244 * @exception IOException if an I/O error occurs. 245 * @see java.io.FileDescriptor 246 */ 247 public final FileDescriptor getFD() throws IOException { 248 if (fd != null) { 249 return fd; 250 } 251 throw new IOException(); 252 } 253 254 /** 255 * Returns the unique {@link java.nio.channels.FileChannel FileChannel} 256 * object associated with this file. 257 * 258 * <p> The {@link java.nio.channels.FileChannel#position() 259 * position} of the returned channel will always be equal to 260 * this object's file-pointer offset as returned by the {@link 261 * #getFilePointer getFilePointer} method. Changing this object's 262 * file-pointer offset, whether explicitly or by reading or writing bytes, 263 * will change the position of the channel, and vice versa. Changing the 264 * file's length via this object will change the length seen via the file 265 * channel, and vice versa. 266 * 267 * @return the file channel associated with this file 268 * 269 * @since 1.4 270 * @spec JSR-51 271 */ 272 public final FileChannel getChannel() { 273 synchronized (this) { 274 if (channel == null) { 275 channel = FileChannelImpl.open(fd, true, rw, this); 276 } 277 return channel; 278 } 279 } 280 281 /** 282 * Opens a file and returns the file descriptor. The file is 283 * opened in read-write mode if the O_RDWR bit in {@code mode} 284 * is true, else the file is opened as read-only. 285 * If the {@code name} refers to a directory, an IOException 286 * is thrown. 287 * 288 * @param name the name of the file 289 * @param mode the mode flags, a combination of the O_ constants 290 * defined above 291 */ 292 private native void open(String name, int mode) 293 throws FileNotFoundException; 294 295 // 'Read' primitives 296 297 /** 298 * Reads a byte of data from this file. The byte is returned as an 299 * integer in the range 0 to 255 ({@code 0x00-0x0ff}). This 300 * method blocks if no input is yet available. 301 * <p> 302 * Although {@code RandomAccessFile} is not a subclass of 303 * {@code InputStream}, this method behaves in exactly the same 304 * way as the {@link InputStream#read()} method of 305 * {@code InputStream}. 306 * 307 * @return the next byte of data, or {@code -1} if the end of the 308 * file has been reached. 309 * @exception IOException if an I/O error occurs. Not thrown if 310 * end-of-file has been reached. 311 */ 312 public native int read() throws IOException; 313 314 /** 315 * Reads a sub array as a sequence of bytes. 316 * @param b the buffer into which the data is read. 317 * @param off the start offset of the data. 318 * @param len the number of bytes to read. 319 * @exception IOException If an I/O error has occurred. 320 */ 321 private native int readBytes(byte b[], int off, int len) throws IOException; 322 323 /** 324 * Reads up to {@code len} bytes of data from this file into an 325 * array of bytes. This method blocks until at least one byte of input 326 * is available. 327 * <p> 328 * Although {@code RandomAccessFile} is not a subclass of 329 * {@code InputStream}, this method behaves in exactly the 330 * same way as the {@link InputStream#read(byte[], int, int)} method of 331 * {@code InputStream}. 332 * 333 * @param b the buffer into which the data is read. 334 * @param off the start offset in array {@code b} 335 * at which the data is written. 336 * @param len the maximum number of bytes read. 337 * @return the total number of bytes read into the buffer, or 338 * {@code -1} if there is no more data because the end of 339 * the file has been reached. 340 * @exception IOException If the first byte cannot be read for any reason 341 * other than end of file, or if the random access file has been closed, or if 342 * some other I/O error occurs. 343 * @exception NullPointerException If {@code b} is {@code null}. 344 * @exception IndexOutOfBoundsException If {@code off} is negative, 345 * {@code len} is negative, or {@code len} is greater than 346 * {@code b.length - off} 347 */ 348 public int read(byte b[], int off, int len) throws IOException { 349 return readBytes(b, off, len); 350 } 351 352 /** 353 * Reads up to {@code b.length} bytes of data from this file 354 * into an array of bytes. This method blocks until at least one byte 355 * of input is available. 356 * <p> 357 * Although {@code RandomAccessFile} is not a subclass of 358 * {@code InputStream}, this method behaves in exactly the 359 * same way as the {@link InputStream#read(byte[])} method of 360 * {@code InputStream}. 361 * 362 * @param b the buffer into which the data is read. 363 * @return the total number of bytes read into the buffer, or 364 * {@code -1} if there is no more data because the end of 365 * this file has been reached. 366 * @exception IOException If the first byte cannot be read for any reason 367 * other than end of file, or if the random access file has been closed, or if 368 * some other I/O error occurs. 369 * @exception NullPointerException If {@code b} is {@code null}. 370 */ 371 public int read(byte b[]) throws IOException { 372 return readBytes(b, 0, b.length); 373 } 374 375 /** 376 * Reads {@code b.length} bytes from this file into the byte 377 * array, starting at the current file pointer. This method reads 378 * repeatedly from the file until the requested number of bytes are 379 * read. This method blocks until the requested number of bytes are 380 * read, the end of the stream is detected, or an exception is thrown. 381 * 382 * @param b the buffer into which the data is read. 383 * @exception EOFException if this file reaches the end before reading 384 * all the bytes. 385 * @exception IOException if an I/O error occurs. 386 */ 387 public final void readFully(byte b[]) throws IOException { 388 readFully(b, 0, b.length); 389 } 390 391 /** 392 * Reads exactly {@code len} bytes from this file into the byte 393 * array, starting at the current file pointer. This method reads 394 * repeatedly from the file until the requested number of bytes are 395 * read. This method blocks until the requested number of bytes are 396 * read, the end of the stream is detected, or an exception is thrown. 397 * 398 * @param b the buffer into which the data is read. 399 * @param off the start offset of the data. 400 * @param len the number of bytes to read. 401 * @exception EOFException if this file reaches the end before reading 402 * all the bytes. 403 * @exception IOException if an I/O error occurs. 404 */ 405 public final void readFully(byte b[], int off, int len) throws IOException { 406 int n = 0; 407 do { 408 int count = this.read(b, off + n, len - n); 409 if (count < 0) 410 throw new EOFException(); 411 n += count; 412 } while (n < len); 413 } 414 415 /** 416 * Attempts to skip over {@code n} bytes of input discarding the 417 * skipped bytes. 418 * <p> 419 * 420 * This method may skip over some smaller number of bytes, possibly zero. 421 * This may result from any of a number of conditions; reaching end of 422 * file before {@code n} bytes have been skipped is only one 423 * possibility. This method never throws an {@code EOFException}. 424 * The actual number of bytes skipped is returned. If {@code n} 425 * is negative, no bytes are skipped. 426 * 427 * @param n the number of bytes to be skipped. 428 * @return the actual number of bytes skipped. 429 * @exception IOException if an I/O error occurs. 430 */ 431 public int skipBytes(int n) throws IOException { 432 long pos; 433 long len; 434 long newpos; 435 436 if (n <= 0) { 437 return 0; 438 } 439 pos = getFilePointer(); 440 len = length(); 441 newpos = pos + n; 442 if (newpos > len) { 443 newpos = len; 444 } 445 seek(newpos); 446 447 /* return the actual number of bytes skipped */ 448 return (int) (newpos - pos); 449 } 450 451 // 'Write' primitives 452 453 /** 454 * Writes the specified byte to this file. The write starts at 455 * the current file pointer. 456 * 457 * @param b the {@code byte} to be written. 458 * @exception IOException if an I/O error occurs. 459 */ 460 public native void write(int b) throws IOException; 461 462 /** 463 * Writes a sub array as a sequence of bytes. 464 * @param b the data to be written 465 466 * @param off the start offset in the data 467 * @param len the number of bytes that are written 468 * @exception IOException If an I/O error has occurred. 469 */ 470 private native void writeBytes(byte b[], int off, int len) throws IOException; 471 472 /** 473 * Writes {@code b.length} bytes from the specified byte array 474 * to this file, starting at the current file pointer. 475 * 476 * @param b the data. 477 * @exception IOException if an I/O error occurs. 478 */ 479 public void write(byte b[]) throws IOException { 480 writeBytes(b, 0, b.length); 481 } 482 483 /** 484 * Writes {@code len} bytes from the specified byte array 485 * starting at offset {@code off} to this file. 486 * 487 * @param b the data. 488 * @param off the start offset in the data. 489 * @param len the number of bytes to write. 490 * @exception IOException if an I/O error occurs. 491 */ 492 public void write(byte b[], int off, int len) throws IOException { 493 writeBytes(b, off, len); 494 } 495 496 // 'Random access' stuff 497 498 /** 499 * Returns the current offset in this file. 500 * 501 * @return the offset from the beginning of the file, in bytes, 502 * at which the next read or write occurs. 503 * @exception IOException if an I/O error occurs. 504 */ 505 public native long getFilePointer() throws IOException; 506 507 /** 508 * Sets the file-pointer offset, measured from the beginning of this 509 * file, at which the next read or write occurs. The offset may be 510 * set beyond the end of the file. Setting the offset beyond the end 511 * of the file does not change the file length. The file length will 512 * change only by writing after the offset has been set beyond the end 513 * of the file. 514 * 515 * @param pos the offset position, measured in bytes from the 516 * beginning of the file, at which to set the file 517 * pointer. 518 * @exception IOException if {@code pos} is less than 519 * {@code 0} or if an I/O error occurs. 520 */ 521 public native void seek(long pos) throws IOException; 522 523 /** 524 * Returns the length of this file. 525 * 526 * @return the length of this file, measured in bytes. 527 * @exception IOException if an I/O error occurs. 528 */ 529 public native long length() throws IOException; 530 531 /** 532 * Sets the length of this file. 533 * 534 * <p> If the present length of the file as returned by the 535 * {@code length} method is greater than the {@code newLength} 536 * argument then the file will be truncated. In this case, if the file 537 * offset as returned by the {@code getFilePointer} method is greater 538 * than {@code newLength} then after this method returns the offset 539 * will be equal to {@code newLength}. 540 * 541 * <p> If the present length of the file as returned by the 542 * {@code length} method is smaller than the {@code newLength} 543 * argument then the file will be extended. In this case, the contents of 544 * the extended portion of the file are not defined. 545 * 546 * @param newLength The desired length of the file 547 * @exception IOException If an I/O error occurs 548 * @since 1.2 549 */ 550 public native void setLength(long newLength) throws IOException; 551 552 /** 553 * Closes this random access file stream and releases any system 554 * resources associated with the stream. A closed random access 555 * file cannot perform input or output operations and cannot be 556 * reopened. 557 * 558 * <p> If this file has an associated channel then the channel is closed 559 * as well. 560 * 561 * @exception IOException if an I/O error occurs. 562 * 563 * @revised 1.4 564 * @spec JSR-51 565 */ 566 public void close() throws IOException { 567 synchronized (closeLock) { 568 if (closed) { 569 return; 570 } 571 closed = true; 572 } 573 if (channel != null) { 574 channel.close(); 575 } 576 577 fd.closeAll(new Closeable() { 578 public void close() throws IOException { 579 close0(); 580 } 581 }); 582 } 583 584 // 585 // Some "reading/writing Java data types" methods stolen from 586 // DataInputStream and DataOutputStream. 587 // 588 589 /** 590 * Reads a {@code boolean} from this file. This method reads a 591 * single byte from the file, starting at the current file pointer. 592 * A value of {@code 0} represents 593 * {@code false}. Any other value represents {@code true}. 594 * This method blocks until the byte is read, the end of the stream 595 * is detected, or an exception is thrown. 596 * 597 * @return the {@code boolean} value read. 598 * @exception EOFException if this file has reached the end. 599 * @exception IOException if an I/O error occurs. 600 */ 601 public final boolean readBoolean() throws IOException { 602 int ch = this.read(); 603 if (ch < 0) 604 throw new EOFException(); 605 return (ch != 0); 606 } 607 608 /** 609 * Reads a signed eight-bit value from this file. This method reads a 610 * byte from the file, starting from the current file pointer. 611 * If the byte read is {@code b}, where 612 * <code>0 <= b <= 255</code>, 613 * then the result is: 614 * <blockquote><pre> 615 * (byte)(b) 616 * </pre></blockquote> 617 * <p> 618 * This method blocks until the byte is read, the end of the stream 619 * is detected, or an exception is thrown. 620 * 621 * @return the next byte of this file as a signed eight-bit 622 * {@code byte}. 623 * @exception EOFException if this file has reached the end. 624 * @exception IOException if an I/O error occurs. 625 */ 626 public final byte readByte() throws IOException { 627 int ch = this.read(); 628 if (ch < 0) 629 throw new EOFException(); 630 return (byte)(ch); 631 } 632 633 /** 634 * Reads an unsigned eight-bit number from this file. This method reads 635 * a byte from this file, starting at the current file pointer, 636 * and returns that byte. 637 * <p> 638 * This method blocks until the byte is read, the end of the stream 639 * is detected, or an exception is thrown. 640 * 641 * @return the next byte of this file, interpreted as an unsigned 642 * eight-bit number. 643 * @exception EOFException if this file has reached the end. 644 * @exception IOException if an I/O error occurs. 645 */ 646 public final int readUnsignedByte() throws IOException { 647 int ch = this.read(); 648 if (ch < 0) 649 throw new EOFException(); 650 return ch; 651 } 652 653 /** 654 * Reads a signed 16-bit number from this file. The method reads two 655 * bytes from this file, starting at the current file pointer. 656 * If the two bytes read, in order, are 657 * {@code b1} and {@code b2}, where each of the two values is 658 * between {@code 0} and {@code 255}, inclusive, then the 659 * result is equal to: 660 * <blockquote><pre> 661 * (short)((b1 << 8) | b2) 662 * </pre></blockquote> 663 * <p> 664 * This method blocks until the two bytes are read, the end of the 665 * stream is detected, or an exception is thrown. 666 * 667 * @return the next two bytes of this file, interpreted as a signed 668 * 16-bit number. 669 * @exception EOFException if this file reaches the end before reading 670 * two bytes. 671 * @exception IOException if an I/O error occurs. 672 */ 673 public final short readShort() throws IOException { 674 int ch1 = this.read(); 675 int ch2 = this.read(); 676 if ((ch1 | ch2) < 0) 677 throw new EOFException(); 678 return (short)((ch1 << 8) + (ch2 << 0)); 679 } 680 681 /** 682 * Reads an unsigned 16-bit number from this file. This method reads 683 * two bytes from the file, starting at the current file pointer. 684 * If the bytes read, in order, are 685 * {@code b1} and {@code b2}, where 686 * <code>0 <= b1, b2 <= 255</code>, 687 * then the result is equal to: 688 * <blockquote><pre> 689 * (b1 << 8) | b2 690 * </pre></blockquote> 691 * <p> 692 * This method blocks until the two bytes are read, the end of the 693 * stream is detected, or an exception is thrown. 694 * 695 * @return the next two bytes of this file, interpreted as an unsigned 696 * 16-bit integer. 697 * @exception EOFException if this file reaches the end before reading 698 * two bytes. 699 * @exception IOException if an I/O error occurs. 700 */ 701 public final int readUnsignedShort() throws IOException { 702 int ch1 = this.read(); 703 int ch2 = this.read(); 704 if ((ch1 | ch2) < 0) 705 throw new EOFException(); 706 return (ch1 << 8) + (ch2 << 0); 707 } 708 709 /** 710 * Reads a character from this file. This method reads two 711 * bytes from the file, starting at the current file pointer. 712 * If the bytes read, in order, are 713 * {@code b1} and {@code b2}, where 714 * <code>0 <= b1, b2 <= 255</code>, 715 * then the result is equal to: 716 * <blockquote><pre> 717 * (char)((b1 << 8) | b2) 718 * </pre></blockquote> 719 * <p> 720 * This method blocks until the two bytes are read, the end of the 721 * stream is detected, or an exception is thrown. 722 * 723 * @return the next two bytes of this file, interpreted as a 724 * {@code char}. 725 * @exception EOFException if this file reaches the end before reading 726 * two bytes. 727 * @exception IOException if an I/O error occurs. 728 */ 729 public final char readChar() throws IOException { 730 int ch1 = this.read(); 731 int ch2 = this.read(); 732 if ((ch1 | ch2) < 0) 733 throw new EOFException(); 734 return (char)((ch1 << 8) + (ch2 << 0)); 735 } 736 737 /** 738 * Reads a signed 32-bit integer from this file. This method reads 4 739 * bytes from the file, starting at the current file pointer. 740 * If the bytes read, in order, are {@code b1}, 741 * {@code b2}, {@code b3}, and {@code b4}, where 742 * <code>0 <= b1, b2, b3, b4 <= 255</code>, 743 * then the result is equal to: 744 * <blockquote><pre> 745 * (b1 << 24) | (b2 << 16) + (b3 << 8) + b4 746 * </pre></blockquote> 747 * <p> 748 * This method blocks until the four bytes are read, the end of the 749 * stream is detected, or an exception is thrown. 750 * 751 * @return the next four bytes of this file, interpreted as an 752 * {@code int}. 753 * @exception EOFException if this file reaches the end before reading 754 * four bytes. 755 * @exception IOException if an I/O error occurs. 756 */ 757 public final int readInt() throws IOException { 758 int ch1 = this.read(); 759 int ch2 = this.read(); 760 int ch3 = this.read(); 761 int ch4 = this.read(); 762 if ((ch1 | ch2 | ch3 | ch4) < 0) 763 throw new EOFException(); 764 return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0)); 765 } 766 767 /** 768 * Reads a signed 64-bit integer from this file. This method reads eight 769 * bytes from the file, starting at the current file pointer. 770 * If the bytes read, in order, are 771 * {@code b1}, {@code b2}, {@code b3}, 772 * {@code b4}, {@code b5}, {@code b6}, 773 * {@code b7}, and {@code b8,} where: 774 * <blockquote><pre> 775 * 0 <= b1, b2, b3, b4, b5, b6, b7, b8 <=255, 776 * </pre></blockquote> 777 * <p> 778 * then the result is equal to: 779 * <p><blockquote><pre> 780 * ((long)b1 << 56) + ((long)b2 << 48) 781 * + ((long)b3 << 40) + ((long)b4 << 32) 782 * + ((long)b5 << 24) + ((long)b6 << 16) 783 * + ((long)b7 << 8) + b8 784 * </pre></blockquote> 785 * <p> 786 * This method blocks until the eight bytes are read, the end of the 787 * stream is detected, or an exception is thrown. 788 * 789 * @return the next eight bytes of this file, interpreted as a 790 * {@code long}. 791 * @exception EOFException if this file reaches the end before reading 792 * eight bytes. 793 * @exception IOException if an I/O error occurs. 794 */ 795 public final long readLong() throws IOException { 796 return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL); 797 } 798 799 /** 800 * Reads a {@code float} from this file. This method reads an 801 * {@code int} value, starting at the current file pointer, 802 * as if by the {@code readInt} method 803 * and then converts that {@code int} to a {@code float} 804 * using the {@code intBitsToFloat} method in class 805 * {@code Float}. 806 * <p> 807 * This method blocks until the four bytes are read, the end of the 808 * stream is detected, or an exception is thrown. 809 * 810 * @return the next four bytes of this file, interpreted as a 811 * {@code float}. 812 * @exception EOFException if this file reaches the end before reading 813 * four bytes. 814 * @exception IOException if an I/O error occurs. 815 * @see java.io.RandomAccessFile#readInt() 816 * @see java.lang.Float#intBitsToFloat(int) 817 */ 818 public final float readFloat() throws IOException { 819 return Float.intBitsToFloat(readInt()); 820 } 821 822 /** 823 * Reads a {@code double} from this file. This method reads a 824 * {@code long} value, starting at the current file pointer, 825 * as if by the {@code readLong} method 826 * and then converts that {@code long} to a {@code double} 827 * using the {@code longBitsToDouble} method in 828 * class {@code Double}. 829 * <p> 830 * This method blocks until the eight bytes are read, the end of the 831 * stream is detected, or an exception is thrown. 832 * 833 * @return the next eight bytes of this file, interpreted as a 834 * {@code double}. 835 * @exception EOFException if this file reaches the end before reading 836 * eight bytes. 837 * @exception IOException if an I/O error occurs. 838 * @see java.io.RandomAccessFile#readLong() 839 * @see java.lang.Double#longBitsToDouble(long) 840 */ 841 public final double readDouble() throws IOException { 842 return Double.longBitsToDouble(readLong()); 843 } 844 845 /** 846 * Reads the next line of text from this file. This method successively 847 * reads bytes from the file, starting at the current file pointer, 848 * until it reaches a line terminator or the end 849 * of the file. Each byte is converted into a character by taking the 850 * byte's value for the lower eight bits of the character and setting the 851 * high eight bits of the character to zero. This method does not, 852 * therefore, support the full Unicode character set. 853 * 854 * <p> A line of text is terminated by a carriage-return character 855 * ({@code '\u005Cr'}), a newline character ({@code '\u005Cn'}), a 856 * carriage-return character immediately followed by a newline character, 857 * or the end of the file. Line-terminating characters are discarded and 858 * are not included as part of the string returned. 859 * 860 * <p> This method blocks until a newline character is read, a carriage 861 * return and the byte following it are read (to see if it is a newline), 862 * the end of the file is reached, or an exception is thrown. 863 * 864 * @return the next line of text from this file, or null if end 865 * of file is encountered before even one byte is read. 866 * @exception IOException if an I/O error occurs. 867 */ 868 869 public final String readLine() throws IOException { 870 StringBuffer input = new StringBuffer(); 871 int c = -1; 872 boolean eol = false; 873 874 while (!eol) { 875 switch (c = read()) { 876 case -1: 877 case '\n': 878 eol = true; 879 break; 880 case '\r': 881 eol = true; 882 long cur = getFilePointer(); 883 if ((read()) != '\n') { 884 seek(cur); 885 } 886 break; 887 default: 888 input.append((char)c); 889 break; 890 } 891 } 892 893 if ((c == -1) && (input.length() == 0)) { 894 return null; 895 } 896 return input.toString(); 897 } 898 899 /** 900 * Reads in a string from this file. The string has been encoded 901 * using a 902 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a> 903 * format. 904 * <p> 905 * The first two bytes are read, starting from the current file 906 * pointer, as if by 907 * {@code readUnsignedShort}. This value gives the number of 908 * following bytes that are in the encoded string, not 909 * the length of the resulting string. The following bytes are then 910 * interpreted as bytes encoding characters in the modified UTF-8 format 911 * and are converted into characters. 912 * <p> 913 * This method blocks until all the bytes are read, the end of the 914 * stream is detected, or an exception is thrown. 915 * 916 * @return a Unicode string. 917 * @exception EOFException if this file reaches the end before 918 * reading all the bytes. 919 * @exception IOException if an I/O error occurs. 920 * @exception UTFDataFormatException if the bytes do not represent 921 * valid modified UTF-8 encoding of a Unicode string. 922 * @see java.io.RandomAccessFile#readUnsignedShort() 923 */ 924 public final String readUTF() throws IOException { 925 return DataInputStream.readUTF(this); 926 } 927 928 /** 929 * Writes a {@code boolean} to the file as a one-byte value. The 930 * value {@code true} is written out as the value 931 * {@code (byte)1}; the value {@code false} is written out 932 * as the value {@code (byte)0}. The write starts at 933 * the current position of the file pointer. 934 * 935 * @param v a {@code boolean} value to be written. 936 * @exception IOException if an I/O error occurs. 937 */ 938 public final void writeBoolean(boolean v) throws IOException { 939 write(v ? 1 : 0); 940 //written++; 941 } 942 943 /** 944 * Writes a {@code byte} to the file as a one-byte value. The 945 * write starts at the current position of the file pointer. 946 * 947 * @param v a {@code byte} value to be written. 948 * @exception IOException if an I/O error occurs. 949 */ 950 public final void writeByte(int v) throws IOException { 951 write(v); 952 //written++; 953 } 954 955 /** 956 * Writes a {@code short} to the file as two bytes, high byte first. 957 * The write starts at the current position of the file pointer. 958 * 959 * @param v a {@code short} to be written. 960 * @exception IOException if an I/O error occurs. 961 */ 962 public final void writeShort(int v) throws IOException { 963 write((v >>> 8) & 0xFF); 964 write((v >>> 0) & 0xFF); 965 //written += 2; 966 } 967 968 /** 969 * Writes a {@code char} to the file as a two-byte value, high 970 * byte first. The write starts at the current position of the 971 * file pointer. 972 * 973 * @param v a {@code char} value to be written. 974 * @exception IOException if an I/O error occurs. 975 */ 976 public final void writeChar(int v) throws IOException { 977 write((v >>> 8) & 0xFF); 978 write((v >>> 0) & 0xFF); 979 //written += 2; 980 } 981 982 /** 983 * Writes an {@code int} to the file as four bytes, high byte first. 984 * The write starts at the current position of the file pointer. 985 * 986 * @param v an {@code int} to be written. 987 * @exception IOException if an I/O error occurs. 988 */ 989 public final void writeInt(int v) throws IOException { 990 write((v >>> 24) & 0xFF); 991 write((v >>> 16) & 0xFF); 992 write((v >>> 8) & 0xFF); 993 write((v >>> 0) & 0xFF); 994 //written += 4; 995 } 996 997 /** 998 * Writes a {@code long} to the file as eight bytes, high byte first. 999 * The write starts at the current position of the file pointer. 1000 * 1001 * @param v a {@code long} to be written. 1002 * @exception IOException if an I/O error occurs. 1003 */ 1004 public final void writeLong(long v) throws IOException { 1005 write((int)(v >>> 56) & 0xFF); 1006 write((int)(v >>> 48) & 0xFF); 1007 write((int)(v >>> 40) & 0xFF); 1008 write((int)(v >>> 32) & 0xFF); 1009 write((int)(v >>> 24) & 0xFF); 1010 write((int)(v >>> 16) & 0xFF); 1011 write((int)(v >>> 8) & 0xFF); 1012 write((int)(v >>> 0) & 0xFF); 1013 //written += 8; 1014 } 1015 1016 /** 1017 * Converts the float argument to an {@code int} using the 1018 * {@code floatToIntBits} method in class {@code Float}, 1019 * and then writes that {@code int} value to the file as a 1020 * four-byte quantity, high byte first. The write starts at the 1021 * current position of the file pointer. 1022 * 1023 * @param v a {@code float} value to be written. 1024 * @exception IOException if an I/O error occurs. 1025 * @see java.lang.Float#floatToIntBits(float) 1026 */ 1027 public final void writeFloat(float v) throws IOException { 1028 writeInt(Float.floatToIntBits(v)); 1029 } 1030 1031 /** 1032 * Converts the double argument to a {@code long} using the 1033 * {@code doubleToLongBits} method in class {@code Double}, 1034 * and then writes that {@code long} value to the file as an 1035 * eight-byte quantity, high byte first. The write starts at the current 1036 * position of the file pointer. 1037 * 1038 * @param v a {@code double} value to be written. 1039 * @exception IOException if an I/O error occurs. 1040 * @see java.lang.Double#doubleToLongBits(double) 1041 */ 1042 public final void writeDouble(double v) throws IOException { 1043 writeLong(Double.doubleToLongBits(v)); 1044 } 1045 1046 /** 1047 * Writes the string to the file as a sequence of bytes. Each 1048 * character in the string is written out, in sequence, by discarding 1049 * its high eight bits. The write starts at the current position of 1050 * the file pointer. 1051 * 1052 * @param s a string of bytes to be written. 1053 * @exception IOException if an I/O error occurs. 1054 */ 1055 @SuppressWarnings("deprecation") 1056 public final void writeBytes(String s) throws IOException { 1057 int len = s.length(); 1058 byte[] b = new byte[len]; 1059 s.getBytes(0, len, b, 0); 1060 writeBytes(b, 0, len); 1061 } 1062 1063 /** 1064 * Writes a string to the file as a sequence of characters. Each 1065 * character is written to the data output stream as if by the 1066 * {@code writeChar} method. The write starts at the current 1067 * position of the file pointer. 1068 * 1069 * @param s a {@code String} value to be written. 1070 * @exception IOException if an I/O error occurs. 1071 * @see java.io.RandomAccessFile#writeChar(int) 1072 */ 1073 public final void writeChars(String s) throws IOException { 1074 int clen = s.length(); 1075 int blen = 2*clen; 1076 byte[] b = new byte[blen]; 1077 char[] c = new char[clen]; 1078 s.getChars(0, clen, c, 0); 1079 for (int i = 0, j = 0; i < clen; i++) { 1080 b[j++] = (byte)(c[i] >>> 8); 1081 b[j++] = (byte)(c[i] >>> 0); 1082 } 1083 writeBytes(b, 0, blen); 1084 } 1085 1086 /** 1087 * Writes a string to the file using 1088 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a> 1089 * encoding in a machine-independent manner. 1090 * <p> 1091 * First, two bytes are written to the file, starting at the 1092 * current file pointer, as if by the 1093 * {@code writeShort} method giving the number of bytes to 1094 * follow. This value is the number of bytes actually written out, 1095 * not the length of the string. Following the length, each character 1096 * of the string is output, in sequence, using the modified UTF-8 encoding 1097 * for each character. 1098 * 1099 * @param str a string to be written. 1100 * @exception IOException if an I/O error occurs. 1101 */ 1102 public final void writeUTF(String str) throws IOException { 1103 DataOutputStream.writeUTF(str, this); 1104 } 1105 1106 private static native void initIDs(); 1107 1108 private native void close0() throws IOException; 1109 1110 static { 1111 initIDs(); 1112 } 1113 }