1 /* 2 * Copyright (c) 1994, 2011, 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" </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.attach(this); 233 open(name, imode); 234 } 235 236 /** 237 * Returns the opaque file descriptor object associated with this 238 * stream. </p> 239 * 240 * @return the file descriptor object associated with this stream. 241 * @exception IOException if an I/O error occurs. 242 * @see java.io.FileDescriptor 243 */ 244 public final FileDescriptor getFD() throws IOException { 245 if (fd != null) { 246 return fd; 247 } 248 throw new IOException(); 249 } 250 251 /** 252 * Returns the unique {@link java.nio.channels.FileChannel FileChannel} 253 * object associated with this file. 254 * 255 * <p> The {@link java.nio.channels.FileChannel#position() 256 * </code>position<code>} of the returned channel will always be equal to 257 * this object's file-pointer offset as returned by the {@link 258 * #getFilePointer getFilePointer} method. Changing this object's 259 * file-pointer offset, whether explicitly or by reading or writing bytes, 260 * will change the position of the channel, and vice versa. Changing the 261 * file's length via this object will change the length seen via the file 262 * channel, and vice versa. 263 * 264 * @return the file channel associated with this file 265 * 266 * @since 1.4 267 * @spec JSR-51 268 */ 269 public final FileChannel getChannel() { 270 synchronized (this) { 271 if (channel == null) { 272 channel = FileChannelImpl.open(fd, true, rw, this); 273 } 274 return channel; 275 } 276 } 277 278 /** 279 * Opens a file and returns the file descriptor. The file is 280 * opened in read-write mode if the O_RDWR bit in <code>mode</code> 281 * is true, else the file is opened as read-only. 282 * If the <code>name</code> refers to a directory, an IOException 283 * is thrown. 284 * 285 * @param name the name of the file 286 * @param mode the mode flags, a combination of the O_ constants 287 * defined above 288 */ 289 private native void open(String name, int mode) 290 throws FileNotFoundException; 291 292 // 'Read' primitives 293 294 /** 295 * Reads a byte of data from this file. The byte is returned as an 296 * integer in the range 0 to 255 (<code>0x00-0x0ff</code>). This 297 * method blocks if no input is yet available. 298 * <p> 299 * Although <code>RandomAccessFile</code> is not a subclass of 300 * <code>InputStream</code>, this method behaves in exactly the same 301 * way as the {@link InputStream#read()} method of 302 * <code>InputStream</code>. 303 * 304 * @return the next byte of data, or <code>-1</code> if the end of the 305 * file has been reached. 306 * @exception IOException if an I/O error occurs. Not thrown if 307 * end-of-file has been reached. 308 */ 309 public native int read() throws IOException; 310 311 /** 312 * Reads a sub array as a sequence of bytes. 313 * @param b the buffer into which the data is read. 314 * @param off the start offset of the data. 315 * @param len the number of bytes to read. 316 * @exception IOException If an I/O error has occurred. 317 */ 318 private native int readBytes(byte b[], int off, int len) throws IOException; 319 320 /** 321 * Reads up to <code>len</code> bytes of data from this file into an 322 * array of bytes. This method blocks until at least one byte of input 323 * is available. 324 * <p> 325 * Although <code>RandomAccessFile</code> is not a subclass of 326 * <code>InputStream</code>, this method behaves in exactly the 327 * same way as the {@link InputStream#read(byte[], int, int)} method of 328 * <code>InputStream</code>. 329 * 330 * @param b the buffer into which the data is read. 331 * @param off the start offset in array <code>b</code> 332 * at which the data is written. 333 * @param len the maximum number of bytes read. 334 * @return the total number of bytes read into the buffer, or 335 * <code>-1</code> if there is no more data because the end of 336 * the file has been reached. 337 * @exception IOException If the first byte cannot be read for any reason 338 * other than end of file, or if the random access file has been closed, or if 339 * some other I/O error occurs. 340 * @exception NullPointerException If <code>b</code> is <code>null</code>. 341 * @exception IndexOutOfBoundsException If <code>off</code> is negative, 342 * <code>len</code> is negative, or <code>len</code> is greater than 343 * <code>b.length - off</code> 344 */ 345 public int read(byte b[], int off, int len) throws IOException { 346 return readBytes(b, off, len); 347 } 348 349 /** 350 * Reads up to <code>b.length</code> bytes of data from this file 351 * into an array of bytes. This method blocks until at least one byte 352 * of input is available. 353 * <p> 354 * Although <code>RandomAccessFile</code> is not a subclass of 355 * <code>InputStream</code>, this method behaves in exactly the 356 * same way as the {@link InputStream#read(byte[])} method of 357 * <code>InputStream</code>. 358 * 359 * @param b the buffer into which the data is read. 360 * @return the total number of bytes read into the buffer, or 361 * <code>-1</code> if there is no more data because the end of 362 * this file has been reached. 363 * @exception IOException If the first byte cannot be read for any reason 364 * other than end of file, or if the random access file has been closed, or if 365 * some other I/O error occurs. 366 * @exception NullPointerException If <code>b</code> is <code>null</code>. 367 */ 368 public int read(byte b[]) throws IOException { 369 return readBytes(b, 0, b.length); 370 } 371 372 /** 373 * Reads <code>b.length</code> bytes from this file into the byte 374 * array, starting at the current file pointer. This method reads 375 * repeatedly from the file until the requested number of bytes are 376 * read. This method blocks until the requested number of bytes are 377 * read, the end of the stream is detected, or an exception is thrown. 378 * 379 * @param b the buffer into which the data is read. 380 * @exception EOFException if this file reaches the end before reading 381 * all the bytes. 382 * @exception IOException if an I/O error occurs. 383 */ 384 public final void readFully(byte b[]) throws IOException { 385 readFully(b, 0, b.length); 386 } 387 388 /** 389 * Reads exactly <code>len</code> bytes from this file into the byte 390 * array, starting at the current file pointer. This method reads 391 * repeatedly from the file until the requested number of bytes are 392 * read. This method blocks until the requested number of bytes are 393 * read, the end of the stream is detected, or an exception is thrown. 394 * 395 * @param b the buffer into which the data is read. 396 * @param off the start offset of the data. 397 * @param len the number of bytes to read. 398 * @exception EOFException if this file reaches the end before reading 399 * all the bytes. 400 * @exception IOException if an I/O error occurs. 401 */ 402 public final void readFully(byte b[], int off, int len) throws IOException { 403 int n = 0; 404 do { 405 int count = this.read(b, off + n, len - n); 406 if (count < 0) 407 throw new EOFException(); 408 n += count; 409 } while (n < len); 410 } 411 412 /** 413 * Attempts to skip over <code>n</code> bytes of input discarding the 414 * skipped bytes. 415 * <p> 416 * 417 * This method may skip over some smaller number of bytes, possibly zero. 418 * This may result from any of a number of conditions; reaching end of 419 * file before <code>n</code> bytes have been skipped is only one 420 * possibility. This method never throws an <code>EOFException</code>. 421 * The actual number of bytes skipped is returned. If <code>n</code> 422 * is negative, no bytes are skipped. 423 * 424 * @param n the number of bytes to be skipped. 425 * @return the actual number of bytes skipped. 426 * @exception IOException if an I/O error occurs. 427 */ 428 public int skipBytes(int n) throws IOException { 429 long pos; 430 long len; 431 long newpos; 432 433 if (n <= 0) { 434 return 0; 435 } 436 pos = getFilePointer(); 437 len = length(); 438 newpos = pos + n; 439 if (newpos > len) { 440 newpos = len; 441 } 442 seek(newpos); 443 444 /* return the actual number of bytes skipped */ 445 return (int) (newpos - pos); 446 } 447 448 // 'Write' primitives 449 450 /** 451 * Writes the specified byte to this file. The write starts at 452 * the current file pointer. 453 * 454 * @param b the <code>byte</code> to be written. 455 * @exception IOException if an I/O error occurs. 456 */ 457 public native void write(int b) throws IOException; 458 459 /** 460 * Writes a sub array as a sequence of bytes. 461 * @param b the data to be written 462 463 * @param off the start offset in the data 464 * @param len the number of bytes that are written 465 * @exception IOException If an I/O error has occurred. 466 */ 467 private native void writeBytes(byte b[], int off, int len) throws IOException; 468 469 /** 470 * Writes <code>b.length</code> bytes from the specified byte array 471 * to this file, starting at the current file pointer. 472 * 473 * @param b the data. 474 * @exception IOException if an I/O error occurs. 475 */ 476 public void write(byte b[]) throws IOException { 477 writeBytes(b, 0, b.length); 478 } 479 480 /** 481 * Writes <code>len</code> bytes from the specified byte array 482 * starting at offset <code>off</code> to this file. 483 * 484 * @param b the data. 485 * @param off the start offset in the data. 486 * @param len the number of bytes to write. 487 * @exception IOException if an I/O error occurs. 488 */ 489 public void write(byte b[], int off, int len) throws IOException { 490 writeBytes(b, off, len); 491 } 492 493 // 'Random access' stuff 494 495 /** 496 * Returns the current offset in this file. 497 * 498 * @return the offset from the beginning of the file, in bytes, 499 * at which the next read or write occurs. 500 * @exception IOException if an I/O error occurs. 501 */ 502 public native long getFilePointer() throws IOException; 503 504 /** 505 * Sets the file-pointer offset, measured from the beginning of this 506 * file, at which the next read or write occurs. The offset may be 507 * set beyond the end of the file. Setting the offset beyond the end 508 * of the file does not change the file length. The file length will 509 * change only by writing after the offset has been set beyond the end 510 * of the file. 511 * 512 * @param pos the offset position, measured in bytes from the 513 * beginning of the file, at which to set the file 514 * pointer. 515 * @exception IOException if <code>pos</code> is less than 516 * <code>0</code> or if an I/O error occurs. 517 */ 518 public native void seek(long pos) throws IOException; 519 520 /** 521 * Returns the length of this file. 522 * 523 * @return the length of this file, measured in bytes. 524 * @exception IOException if an I/O error occurs. 525 */ 526 public native long length() throws IOException; 527 528 /** 529 * Sets the length of this file. 530 * 531 * <p> If the present length of the file as returned by the 532 * <code>length</code> method is greater than the <code>newLength</code> 533 * argument then the file will be truncated. In this case, if the file 534 * offset as returned by the <code>getFilePointer</code> method is greater 535 * than <code>newLength</code> then after this method returns the offset 536 * will be equal to <code>newLength</code>. 537 * 538 * <p> If the present length of the file as returned by the 539 * <code>length</code> method is smaller than the <code>newLength</code> 540 * argument then the file will be extended. In this case, the contents of 541 * the extended portion of the file are not defined. 542 * 543 * @param newLength The desired length of the file 544 * @exception IOException If an I/O error occurs 545 * @since 1.2 546 */ 547 public native void setLength(long newLength) throws IOException; 548 549 /** 550 * Closes this random access file stream and releases any system 551 * resources associated with the stream. A closed random access 552 * file cannot perform input or output operations and cannot be 553 * reopened. 554 * 555 * <p> If this file has an associated channel then the channel is closed 556 * as well. 557 * 558 * @exception IOException if an I/O error occurs. 559 * 560 * @revised 1.4 561 * @spec JSR-51 562 */ 563 public void close() throws IOException { 564 synchronized (closeLock) { 565 if (closed) { 566 return; 567 } 568 closed = true; 569 } 570 if (channel != null) { 571 channel.close(); 572 } 573 574 fd.closeAll(new Closeable() { 575 public void close() throws IOException { 576 close0(); 577 } 578 }); 579 } 580 581 // 582 // Some "reading/writing Java data types" methods stolen from 583 // DataInputStream and DataOutputStream. 584 // 585 586 /** 587 * Reads a <code>boolean</code> from this file. This method reads a 588 * single byte from the file, starting at the current file pointer. 589 * A value of <code>0</code> represents 590 * <code>false</code>. Any other value represents <code>true</code>. 591 * This method blocks until the byte is read, the end of the stream 592 * is detected, or an exception is thrown. 593 * 594 * @return the <code>boolean</code> value read. 595 * @exception EOFException if this file has reached the end. 596 * @exception IOException if an I/O error occurs. 597 */ 598 public final boolean readBoolean() throws IOException { 599 int ch = this.read(); 600 if (ch < 0) 601 throw new EOFException(); 602 return (ch != 0); 603 } 604 605 /** 606 * Reads a signed eight-bit value from this file. This method reads a 607 * byte from the file, starting from the current file pointer. 608 * If the byte read is <code>b</code>, where 609 * <code>0 <= b <= 255</code>, 610 * then the result is: 611 * <blockquote><pre> 612 * (byte)(b) 613 * </pre></blockquote> 614 * <p> 615 * This method blocks until the byte is read, the end of the stream 616 * is detected, or an exception is thrown. 617 * 618 * @return the next byte of this file as a signed eight-bit 619 * <code>byte</code>. 620 * @exception EOFException if this file has reached the end. 621 * @exception IOException if an I/O error occurs. 622 */ 623 public final byte readByte() throws IOException { 624 int ch = this.read(); 625 if (ch < 0) 626 throw new EOFException(); 627 return (byte)(ch); 628 } 629 630 /** 631 * Reads an unsigned eight-bit number from this file. This method reads 632 * a byte from this file, starting at the current file pointer, 633 * and returns that byte. 634 * <p> 635 * This method blocks until the byte is read, the end of the stream 636 * is detected, or an exception is thrown. 637 * 638 * @return the next byte of this file, interpreted as an unsigned 639 * eight-bit number. 640 * @exception EOFException if this file has reached the end. 641 * @exception IOException if an I/O error occurs. 642 */ 643 public final int readUnsignedByte() throws IOException { 644 int ch = this.read(); 645 if (ch < 0) 646 throw new EOFException(); 647 return ch; 648 } 649 650 /** 651 * Reads a signed 16-bit number from this file. The method reads two 652 * bytes from this file, starting at the current file pointer. 653 * If the two bytes read, in order, are 654 * <code>b1</code> and <code>b2</code>, where each of the two values is 655 * between <code>0</code> and <code>255</code>, inclusive, then the 656 * result is equal to: 657 * <blockquote><pre> 658 * (short)((b1 << 8) | b2) 659 * </pre></blockquote> 660 * <p> 661 * This method blocks until the two bytes are read, the end of the 662 * stream is detected, or an exception is thrown. 663 * 664 * @return the next two bytes of this file, interpreted as a signed 665 * 16-bit number. 666 * @exception EOFException if this file reaches the end before reading 667 * two bytes. 668 * @exception IOException if an I/O error occurs. 669 */ 670 public final short readShort() throws IOException { 671 int ch1 = this.read(); 672 int ch2 = this.read(); 673 if ((ch1 | ch2) < 0) 674 throw new EOFException(); 675 return (short)((ch1 << 8) + (ch2 << 0)); 676 } 677 678 /** 679 * Reads an unsigned 16-bit number from this file. This method reads 680 * two bytes from the file, starting at the current file pointer. 681 * If the bytes read, in order, are 682 * <code>b1</code> and <code>b2</code>, where 683 * <code>0 <= b1, b2 <= 255</code>, 684 * then the result is equal to: 685 * <blockquote><pre> 686 * (b1 << 8) | b2 687 * </pre></blockquote> 688 * <p> 689 * This method blocks until the two bytes are read, the end of the 690 * stream is detected, or an exception is thrown. 691 * 692 * @return the next two bytes of this file, interpreted as an unsigned 693 * 16-bit integer. 694 * @exception EOFException if this file reaches the end before reading 695 * two bytes. 696 * @exception IOException if an I/O error occurs. 697 */ 698 public final int readUnsignedShort() throws IOException { 699 int ch1 = this.read(); 700 int ch2 = this.read(); 701 if ((ch1 | ch2) < 0) 702 throw new EOFException(); 703 return (ch1 << 8) + (ch2 << 0); 704 } 705 706 /** 707 * Reads a character from this file. This method reads two 708 * bytes from the file, starting at the current file pointer. 709 * If the bytes read, in order, are 710 * <code>b1</code> and <code>b2</code>, where 711 * <code>0 <= b1, b2 <= 255</code>, 712 * then the result is equal to: 713 * <blockquote><pre> 714 * (char)((b1 << 8) | b2) 715 * </pre></blockquote> 716 * <p> 717 * This method blocks until the two bytes are read, the end of the 718 * stream is detected, or an exception is thrown. 719 * 720 * @return the next two bytes of this file, interpreted as a 721 * <code>char</code>. 722 * @exception EOFException if this file reaches the end before reading 723 * two bytes. 724 * @exception IOException if an I/O error occurs. 725 */ 726 public final char readChar() throws IOException { 727 int ch1 = this.read(); 728 int ch2 = this.read(); 729 if ((ch1 | ch2) < 0) 730 throw new EOFException(); 731 return (char)((ch1 << 8) + (ch2 << 0)); 732 } 733 734 /** 735 * Reads a signed 32-bit integer from this file. This method reads 4 736 * bytes from the file, starting at the current file pointer. 737 * If the bytes read, in order, are <code>b1</code>, 738 * <code>b2</code>, <code>b3</code>, and <code>b4</code>, where 739 * <code>0 <= b1, b2, b3, b4 <= 255</code>, 740 * then the result is equal to: 741 * <blockquote><pre> 742 * (b1 << 24) | (b2 << 16) + (b3 << 8) + b4 743 * </pre></blockquote> 744 * <p> 745 * This method blocks until the four bytes are read, the end of the 746 * stream is detected, or an exception is thrown. 747 * 748 * @return the next four bytes of this file, interpreted as an 749 * <code>int</code>. 750 * @exception EOFException if this file reaches the end before reading 751 * four bytes. 752 * @exception IOException if an I/O error occurs. 753 */ 754 public final int readInt() throws IOException { 755 int ch1 = this.read(); 756 int ch2 = this.read(); 757 int ch3 = this.read(); 758 int ch4 = this.read(); 759 if ((ch1 | ch2 | ch3 | ch4) < 0) 760 throw new EOFException(); 761 return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0)); 762 } 763 764 /** 765 * Reads a signed 64-bit integer from this file. This method reads eight 766 * bytes from the file, starting at the current file pointer. 767 * If the bytes read, in order, are 768 * <code>b1</code>, <code>b2</code>, <code>b3</code>, 769 * <code>b4</code>, <code>b5</code>, <code>b6</code>, 770 * <code>b7</code>, and <code>b8,</code> where: 771 * <blockquote><pre> 772 * 0 <= b1, b2, b3, b4, b5, b6, b7, b8 <=255, 773 * </pre></blockquote> 774 * <p> 775 * then the result is equal to: 776 * <p><blockquote><pre> 777 * ((long)b1 << 56) + ((long)b2 << 48) 778 * + ((long)b3 << 40) + ((long)b4 << 32) 779 * + ((long)b5 << 24) + ((long)b6 << 16) 780 * + ((long)b7 << 8) + b8 781 * </pre></blockquote> 782 * <p> 783 * This method blocks until the eight bytes are read, the end of the 784 * stream is detected, or an exception is thrown. 785 * 786 * @return the next eight bytes of this file, interpreted as a 787 * <code>long</code>. 788 * @exception EOFException if this file reaches the end before reading 789 * eight bytes. 790 * @exception IOException if an I/O error occurs. 791 */ 792 public final long readLong() throws IOException { 793 return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL); 794 } 795 796 /** 797 * Reads a <code>float</code> from this file. This method reads an 798 * <code>int</code> value, starting at the current file pointer, 799 * as if by the <code>readInt</code> method 800 * and then converts that <code>int</code> to a <code>float</code> 801 * using the <code>intBitsToFloat</code> method in class 802 * <code>Float</code>. 803 * <p> 804 * This method blocks until the four bytes are read, the end of the 805 * stream is detected, or an exception is thrown. 806 * 807 * @return the next four bytes of this file, interpreted as a 808 * <code>float</code>. 809 * @exception EOFException if this file reaches the end before reading 810 * four bytes. 811 * @exception IOException if an I/O error occurs. 812 * @see java.io.RandomAccessFile#readInt() 813 * @see java.lang.Float#intBitsToFloat(int) 814 */ 815 public final float readFloat() throws IOException { 816 return Float.intBitsToFloat(readInt()); 817 } 818 819 /** 820 * Reads a <code>double</code> from this file. This method reads a 821 * <code>long</code> value, starting at the current file pointer, 822 * as if by the <code>readLong</code> method 823 * and then converts that <code>long</code> to a <code>double</code> 824 * using the <code>longBitsToDouble</code> method in 825 * class <code>Double</code>. 826 * <p> 827 * This method blocks until the eight bytes are read, the end of the 828 * stream is detected, or an exception is thrown. 829 * 830 * @return the next eight bytes of this file, interpreted as a 831 * <code>double</code>. 832 * @exception EOFException if this file reaches the end before reading 833 * eight bytes. 834 * @exception IOException if an I/O error occurs. 835 * @see java.io.RandomAccessFile#readLong() 836 * @see java.lang.Double#longBitsToDouble(long) 837 */ 838 public final double readDouble() throws IOException { 839 return Double.longBitsToDouble(readLong()); 840 } 841 842 /** 843 * Reads the next line of text from this file. This method successively 844 * reads bytes from the file, starting at the current file pointer, 845 * until it reaches a line terminator or the end 846 * of the file. Each byte is converted into a character by taking the 847 * byte's value for the lower eight bits of the character and setting the 848 * high eight bits of the character to zero. This method does not, 849 * therefore, support the full Unicode character set. 850 * 851 * <p> A line of text is terminated by a carriage-return character 852 * (<code>'\r'</code>), a newline character (<code>'\n'</code>), a 853 * carriage-return character immediately followed by a newline character, 854 * or the end of the file. Line-terminating characters are discarded and 855 * are not included as part of the string returned. 856 * 857 * <p> This method blocks until a newline character is read, a carriage 858 * return and the byte following it are read (to see if it is a newline), 859 * the end of the file is reached, or an exception is thrown. 860 * 861 * @return the next line of text from this file, or null if end 862 * of file is encountered before even one byte is read. 863 * @exception IOException if an I/O error occurs. 864 */ 865 866 public final String readLine() throws IOException { 867 StringBuffer input = new StringBuffer(); 868 int c = -1; 869 boolean eol = false; 870 871 while (!eol) { 872 switch (c = read()) { 873 case -1: 874 case '\n': 875 eol = true; 876 break; 877 case '\r': 878 eol = true; 879 long cur = getFilePointer(); 880 if ((read()) != '\n') { 881 seek(cur); 882 } 883 break; 884 default: 885 input.append((char)c); 886 break; 887 } 888 } 889 890 if ((c == -1) && (input.length() == 0)) { 891 return null; 892 } 893 return input.toString(); 894 } 895 896 /** 897 * Reads in a string from this file. The string has been encoded 898 * using a 899 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a> 900 * format. 901 * <p> 902 * The first two bytes are read, starting from the current file 903 * pointer, as if by 904 * <code>readUnsignedShort</code>. This value gives the number of 905 * following bytes that are in the encoded string, not 906 * the length of the resulting string. The following bytes are then 907 * interpreted as bytes encoding characters in the modified UTF-8 format 908 * and are converted into characters. 909 * <p> 910 * This method blocks until all the bytes are read, the end of the 911 * stream is detected, or an exception is thrown. 912 * 913 * @return a Unicode string. 914 * @exception EOFException if this file reaches the end before 915 * reading all the bytes. 916 * @exception IOException if an I/O error occurs. 917 * @exception UTFDataFormatException if the bytes do not represent 918 * valid modified UTF-8 encoding of a Unicode string. 919 * @see java.io.RandomAccessFile#readUnsignedShort() 920 */ 921 public final String readUTF() throws IOException { 922 return DataInputStream.readUTF(this); 923 } 924 925 /** 926 * Writes a <code>boolean</code> to the file as a one-byte value. The 927 * value <code>true</code> is written out as the value 928 * <code>(byte)1</code>; the value <code>false</code> is written out 929 * as the value <code>(byte)0</code>. The write starts at 930 * the current position of the file pointer. 931 * 932 * @param v a <code>boolean</code> value to be written. 933 * @exception IOException if an I/O error occurs. 934 */ 935 public final void writeBoolean(boolean v) throws IOException { 936 write(v ? 1 : 0); 937 //written++; 938 } 939 940 /** 941 * Writes a <code>byte</code> to the file as a one-byte value. The 942 * write starts at the current position of the file pointer. 943 * 944 * @param v a <code>byte</code> value to be written. 945 * @exception IOException if an I/O error occurs. 946 */ 947 public final void writeByte(int v) throws IOException { 948 write(v); 949 //written++; 950 } 951 952 /** 953 * Writes a <code>short</code> to the file as two bytes, high byte first. 954 * The write starts at the current position of the file pointer. 955 * 956 * @param v a <code>short</code> to be written. 957 * @exception IOException if an I/O error occurs. 958 */ 959 public final void writeShort(int v) throws IOException { 960 write((v >>> 8) & 0xFF); 961 write((v >>> 0) & 0xFF); 962 //written += 2; 963 } 964 965 /** 966 * Writes a <code>char</code> to the file as a two-byte value, high 967 * byte first. The write starts at the current position of the 968 * file pointer. 969 * 970 * @param v a <code>char</code> value to be written. 971 * @exception IOException if an I/O error occurs. 972 */ 973 public final void writeChar(int v) throws IOException { 974 write((v >>> 8) & 0xFF); 975 write((v >>> 0) & 0xFF); 976 //written += 2; 977 } 978 979 /** 980 * Writes an <code>int</code> to the file as four bytes, high byte first. 981 * The write starts at the current position of the file pointer. 982 * 983 * @param v an <code>int</code> to be written. 984 * @exception IOException if an I/O error occurs. 985 */ 986 public final void writeInt(int v) throws IOException { 987 write((v >>> 24) & 0xFF); 988 write((v >>> 16) & 0xFF); 989 write((v >>> 8) & 0xFF); 990 write((v >>> 0) & 0xFF); 991 //written += 4; 992 } 993 994 /** 995 * Writes a <code>long</code> to the file as eight bytes, high byte first. 996 * The write starts at the current position of the file pointer. 997 * 998 * @param v a <code>long</code> to be written. 999 * @exception IOException if an I/O error occurs. 1000 */ 1001 public final void writeLong(long v) throws IOException { 1002 write((int)(v >>> 56) & 0xFF); 1003 write((int)(v >>> 48) & 0xFF); 1004 write((int)(v >>> 40) & 0xFF); 1005 write((int)(v >>> 32) & 0xFF); 1006 write((int)(v >>> 24) & 0xFF); 1007 write((int)(v >>> 16) & 0xFF); 1008 write((int)(v >>> 8) & 0xFF); 1009 write((int)(v >>> 0) & 0xFF); 1010 //written += 8; 1011 } 1012 1013 /** 1014 * Converts the float argument to an <code>int</code> using the 1015 * <code>floatToIntBits</code> method in class <code>Float</code>, 1016 * and then writes that <code>int</code> value to the file as a 1017 * four-byte quantity, high byte first. The write starts at the 1018 * current position of the file pointer. 1019 * 1020 * @param v a <code>float</code> value to be written. 1021 * @exception IOException if an I/O error occurs. 1022 * @see java.lang.Float#floatToIntBits(float) 1023 */ 1024 public final void writeFloat(float v) throws IOException { 1025 writeInt(Float.floatToIntBits(v)); 1026 } 1027 1028 /** 1029 * Converts the double argument to a <code>long</code> using the 1030 * <code>doubleToLongBits</code> method in class <code>Double</code>, 1031 * and then writes that <code>long</code> value to the file as an 1032 * eight-byte quantity, high byte first. The write starts at the current 1033 * position of the file pointer. 1034 * 1035 * @param v a <code>double</code> value to be written. 1036 * @exception IOException if an I/O error occurs. 1037 * @see java.lang.Double#doubleToLongBits(double) 1038 */ 1039 public final void writeDouble(double v) throws IOException { 1040 writeLong(Double.doubleToLongBits(v)); 1041 } 1042 1043 /** 1044 * Writes the string to the file as a sequence of bytes. Each 1045 * character in the string is written out, in sequence, by discarding 1046 * its high eight bits. The write starts at the current position of 1047 * the file pointer. 1048 * 1049 * @param s a string of bytes to be written. 1050 * @exception IOException if an I/O error occurs. 1051 */ 1052 public final void writeBytes(String s) throws IOException { 1053 int len = s.length(); 1054 byte[] b = new byte[len]; 1055 s.getBytes(0, len, b, 0); 1056 writeBytes(b, 0, len); 1057 } 1058 1059 /** 1060 * Writes a string to the file as a sequence of characters. Each 1061 * character is written to the data output stream as if by the 1062 * <code>writeChar</code> method. The write starts at the current 1063 * position of the file pointer. 1064 * 1065 * @param s a <code>String</code> value to be written. 1066 * @exception IOException if an I/O error occurs. 1067 * @see java.io.RandomAccessFile#writeChar(int) 1068 */ 1069 public final void writeChars(String s) throws IOException { 1070 int clen = s.length(); 1071 int blen = 2*clen; 1072 byte[] b = new byte[blen]; 1073 char[] c = new char[clen]; 1074 s.getChars(0, clen, c, 0); 1075 for (int i = 0, j = 0; i < clen; i++) { 1076 b[j++] = (byte)(c[i] >>> 8); 1077 b[j++] = (byte)(c[i] >>> 0); 1078 } 1079 writeBytes(b, 0, blen); 1080 } 1081 1082 /** 1083 * Writes a string to the file using 1084 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a> 1085 * encoding in a machine-independent manner. 1086 * <p> 1087 * First, two bytes are written to the file, starting at the 1088 * current file pointer, as if by the 1089 * <code>writeShort</code> method giving the number of bytes to 1090 * follow. This value is the number of bytes actually written out, 1091 * not the length of the string. Following the length, each character 1092 * of the string is output, in sequence, using the modified UTF-8 encoding 1093 * for each character. 1094 * 1095 * @param str a string to be written. 1096 * @exception IOException if an I/O error occurs. 1097 */ 1098 public final void writeUTF(String str) throws IOException { 1099 DataOutputStream.writeUTF(str, this); 1100 } 1101 1102 private static native void initIDs(); 1103 1104 private native void close0() throws IOException; 1105 1106 static { 1107 initIDs(); 1108 } 1109 }