1 /* 2 * Copyright (c) 1994, 2012, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.io; 27 28 import java.nio.channels.FileChannel; 29 import sun.nio.ch.FileChannelImpl; 30 31 32 /** 33 * Instances of this class support both reading and writing to a 34 * random access file. A random access file behaves like a large 35 * array of bytes stored in the file system. There is a kind of cursor, 36 * or index into the implied array, called the <em>file pointer</em>; 37 * input operations read bytes starting at the file pointer and advance 38 * the file pointer past the bytes read. If the random access file is 39 * created in read/write mode, then output operations are also available; 40 * output operations write bytes starting at the file pointer and advance 41 * the file pointer past the bytes written. Output operations that write 42 * past the current end of the implied array cause the array to be 43 * extended. The file pointer can be read by the 44 * <code>getFilePointer</code> method and set by the <code>seek</code> 45 * method. 46 * <p> 47 * It is generally true of all the reading routines in this class that 48 * if end-of-file is reached before the desired number of bytes has been 49 * read, an <code>EOFException</code> (which is a kind of 50 * <code>IOException</code>) is thrown. If any byte cannot be read for 51 * any reason other than end-of-file, an <code>IOException</code> other 52 * than <code>EOFException</code> is thrown. In particular, an 53 * <code>IOException</code> may be thrown if the stream has been closed. 54 * 55 * @author unascribed 56 * @since JDK1.0 57 */ 58 59 public class RandomAccessFile implements DataOutput, DataInput, Closeable { 60 61 private FileDescriptor fd; 62 private FileChannel channel = null; 63 private boolean rw; 64 65 private Object closeLock = new Object(); 66 private volatile boolean closed = false; 67 68 private static final int O_RDONLY = 1; 69 private static final int O_RDWR = 2; 70 private static final int O_SYNC = 4; 71 private static final int O_DSYNC = 8; 72 73 /** 74 * Creates a random access file stream to read from, and optionally 75 * to write to, a file with the specified name. A new 76 * {@link FileDescriptor} object is created to represent the 77 * connection to the file. 78 * 79 * <p> The <tt>mode</tt> argument specifies the access mode with which the 80 * file is to be opened. The permitted values and their meanings are as 81 * specified for the <a 82 * href="#mode"><tt>RandomAccessFile(File,String)</tt></a> constructor. 83 * 84 * <p> 85 * If there is a security manager, its <code>checkRead</code> method 86 * is called with the <code>name</code> argument 87 * as its argument to see if read access to the file is allowed. 88 * If the mode allows writing, the security manager's 89 * <code>checkWrite</code> method 90 * is also called with the <code>name</code> argument 91 * as its argument to see if write access to the file is allowed. 92 * 93 * @param name the system-dependent filename 94 * @param mode the access <a href="#mode">mode</a> 95 * @exception IllegalArgumentException if the mode argument is not equal 96 * to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or 97 * <tt>"rwd"</tt> 98 * @exception FileNotFoundException 99 * if the mode is <tt>"r"</tt> but the given string does not 100 * denote an existing regular file, or if the mode begins with 101 * <tt>"rw"</tt> but the given string does not denote an 102 * existing, writable regular file and a new regular file of 103 * that name cannot be created, or if some other error occurs 104 * while opening or creating the file 105 * @exception SecurityException if a security manager exists and its 106 * <code>checkRead</code> method denies read access to the file 107 * or the mode is "rw" and the security manager's 108 * <code>checkWrite</code> method denies write access to the file 109 * @see java.lang.SecurityException 110 * @see java.lang.SecurityManager#checkRead(java.lang.String) 111 * @see java.lang.SecurityManager#checkWrite(java.lang.String) 112 * @revised 1.4 113 * @spec JSR-51 114 */ 115 public RandomAccessFile(String name, String mode) 116 throws FileNotFoundException 117 { 118 this(name != null ? new File(name) : null, mode); 119 } 120 121 /** 122 * Creates a random access file stream to read from, and optionally to 123 * write to, the file specified by the {@link File} argument. A new {@link 124 * FileDescriptor} object is created to represent this file connection. 125 * 126 * <a name="mode"><p> The <tt>mode</tt> argument specifies the access mode 127 * in which the file is to be opened. The permitted values and their 128 * meanings are: 129 * 130 * <blockquote><table summary="Access mode permitted values and meanings"> 131 * <tr><th><p align="left">Value</p></th><th><p align="left">Meaning</p></th></tr> 132 * <tr><td valign="top"><tt>"r"</tt></td> 133 * <td> Open for reading only. Invoking any of the <tt>write</tt> 134 * methods of the resulting object will cause an {@link 135 * java.io.IOException} to be thrown. </td></tr> 136 * <tr><td valign="top"><tt>"rw"</tt></td> 137 * <td> Open for reading and writing. If the file does not already 138 * exist then an attempt will be made to create it. </td></tr> 139 * <tr><td valign="top"><tt>"rws"</tt></td> 140 * <td> Open for reading and writing, as with <tt>"rw"</tt>, and also 141 * require that every update to the file's content or metadata be 142 * written synchronously to the underlying storage device. </td></tr> 143 * <tr><td valign="top"><tt>"rwd" </tt></td> 144 * <td> Open for reading and writing, as with <tt>"rw"</tt>, and also 145 * require that every update to the file's content be written 146 * synchronously to the underlying storage device. </td></tr> 147 * </table></blockquote> 148 * 149 * The <tt>"rws"</tt> and <tt>"rwd"</tt> modes work much like the {@link 150 * java.nio.channels.FileChannel#force(boolean) force(boolean)} method of 151 * the {@link java.nio.channels.FileChannel} class, passing arguments of 152 * <tt>true</tt> and <tt>false</tt>, respectively, except that they always 153 * apply to every I/O operation and are therefore often more efficient. If 154 * the file resides on a local storage device then when an invocation of a 155 * method of this class returns it is guaranteed that all changes made to 156 * the file by that invocation will have been written to that device. This 157 * is useful for ensuring that critical information is not lost in the 158 * event of a system crash. If the file does not reside on a local device 159 * then no such guarantee is made. 160 * 161 * <p> The <tt>"rwd"</tt> mode can be used to reduce the number of I/O 162 * operations performed. Using <tt>"rwd"</tt> only requires updates to the 163 * file's content to be written to storage; using <tt>"rws"</tt> requires 164 * updates to both the file's content and its metadata to be written, which 165 * generally requires at least one more low-level I/O operation. 166 * 167 * <p> If there is a security manager, its <code>checkRead</code> method is 168 * called with the pathname of the <code>file</code> argument as its 169 * argument to see if read access to the file is allowed. If the mode 170 * allows writing, the security manager's <code>checkWrite</code> method is 171 * also called with the path argument to see if write access to the file is 172 * allowed. 173 * 174 * @param file the file object 175 * @param mode the access mode, as described 176 * <a href="#mode">above</a> 177 * @exception IllegalArgumentException if the mode argument is not equal 178 * to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or 179 * <tt>"rwd"</tt> 180 * @exception FileNotFoundException 181 * if the mode is <tt>"r"</tt> but the given file object does 182 * not denote an existing regular file, or if the mode begins 183 * with <tt>"rw"</tt> but the given file object does not denote 184 * an existing, writable regular file and a new regular file of 185 * that name cannot be created, or if some other error occurs 186 * while opening or creating the file 187 * @exception SecurityException if a security manager exists and its 188 * <code>checkRead</code> method denies read access to the file 189 * or the mode is "rw" and the security manager's 190 * <code>checkWrite</code> method denies write access to the file 191 * @see java.lang.SecurityManager#checkRead(java.lang.String) 192 * @see java.lang.SecurityManager#checkWrite(java.lang.String) 193 * @see java.nio.channels.FileChannel#force(boolean) 194 * @revised 1.4 195 * @spec JSR-51 196 */ 197 public RandomAccessFile(File file, String mode) 198 throws FileNotFoundException 199 { 200 String name = (file != null ? file.getPath() : null); 201 int imode = -1; 202 if (mode.equals("r")) 203 imode = O_RDONLY; 204 else if (mode.startsWith("rw")) { 205 imode = O_RDWR; 206 rw = true; 207 if (mode.length() > 2) { 208 if (mode.equals("rws")) 209 imode |= O_SYNC; 210 else if (mode.equals("rwd")) 211 imode |= O_DSYNC; 212 else 213 imode = -1; 214 } 215 } 216 if (imode < 0) 217 throw new IllegalArgumentException("Illegal mode \"" + mode 218 + "\" must be one of " 219 + "\"r\", \"rw\", \"rws\"," 220 + " or \"rwd\""); 221 SecurityManager security = System.getSecurityManager(); 222 if (security != null) { 223 security.checkRead(name); 224 if (rw) { 225 security.checkWrite(name); 226 } 227 } 228 if (name == null) { 229 throw new NullPointerException(); 230 } 231 fd = new FileDescriptor(); 232 fd.incrementAndGetUseCount(); 233 open(name, imode); 234 } 235 236 /** 237 * Returns the opaque file descriptor object associated with this 238 * stream. </p> 239 * 240 * @return the file descriptor object associated with this stream. 241 * @exception IOException if an I/O error occurs. 242 * @see java.io.FileDescriptor 243 */ 244 public final FileDescriptor getFD() throws IOException { 245 if (fd != null) return fd; 246 throw new IOException(); 247 } 248 249 /** 250 * Returns the unique {@link java.nio.channels.FileChannel FileChannel} 251 * object associated with this file. 252 * 253 * <p> The {@link java.nio.channels.FileChannel#position() 254 * </code>position<code>} of the returned channel will always be equal to 255 * this object's file-pointer offset as returned by the {@link 256 * #getFilePointer getFilePointer} method. Changing this object's 257 * file-pointer offset, whether explicitly or by reading or writing bytes, 258 * will change the position of the channel, and vice versa. Changing the 259 * file's length via this object will change the length seen via the file 260 * channel, and vice versa. 261 * 262 * @return the file channel associated with this file 263 * 264 * @since 1.4 265 * @spec JSR-51 266 */ 267 public final FileChannel getChannel() { 268 synchronized (this) { 269 if (channel == null) { 270 channel = FileChannelImpl.open(fd, true, rw, this); 271 272 /* 273 * FileDescriptor could be shared by FileInputStream or 274 * FileOutputStream. 275 * Ensure that FD is GC'ed only when all the streams/channels 276 * are done using it. 277 * Increment fd's use count. Invoking the channel's close() 278 * method will result in decrementing the use count set for 279 * the channel. 280 */ 281 fd.incrementAndGetUseCount(); 282 } 283 return channel; 284 } 285 } 286 287 /** 288 * Opens a file and returns the file descriptor. The file is 289 * opened in read-write mode if the O_RDWR bit in <code>mode</code> 290 * is true, else the file is opened as read-only. 291 * If the <code>name</code> refers to a directory, an IOException 292 * is thrown. 293 * 294 * @param name the name of the file 295 * @param mode the mode flags, a combination of the O_ constants 296 * defined above 297 */ 298 private native void open(String name, int mode) 299 throws FileNotFoundException; 300 301 // 'Read' primitives 302 303 /** 304 * Reads a byte of data from this file. The byte is returned as an 305 * integer in the range 0 to 255 (<code>0x00-0x0ff</code>). This 306 * method blocks if no input is yet available. 307 * <p> 308 * Although <code>RandomAccessFile</code> is not a subclass of 309 * <code>InputStream</code>, this method behaves in exactly the same 310 * way as the {@link InputStream#read()} method of 311 * <code>InputStream</code>. 312 * 313 * @return the next byte of data, or <code>-1</code> if the end of the 314 * file has been reached. 315 * @exception IOException if an I/O error occurs. Not thrown if 316 * end-of-file has been reached. 317 */ 318 public native int read() throws IOException; 319 320 /** 321 * Reads a sub array as a sequence of bytes. 322 * @param b the buffer into which the data is read. 323 * @param off the start offset of the data. 324 * @param len the number of bytes to read. 325 * @exception IOException If an I/O error has occurred. 326 */ 327 private native int readBytes(byte b[], int off, int len) throws IOException; 328 329 /** 330 * Reads up to <code>len</code> bytes of data from this file into an 331 * array of bytes. This method blocks until at least one byte of input 332 * is available. 333 * <p> 334 * Although <code>RandomAccessFile</code> is not a subclass of 335 * <code>InputStream</code>, this method behaves in exactly the 336 * same way as the {@link InputStream#read(byte[], int, int)} method of 337 * <code>InputStream</code>. 338 * 339 * @param b the buffer into which the data is read. 340 * @param off the start offset in array <code>b</code> 341 * at which the data is written. 342 * @param len the maximum number of bytes read. 343 * @return the total number of bytes read into the buffer, or 344 * <code>-1</code> if there is no more data because the end of 345 * the file has been reached. 346 * @exception IOException If the first byte cannot be read for any reason 347 * other than end of file, or if the random access file has been closed, or if 348 * some other I/O error occurs. 349 * @exception NullPointerException If <code>b</code> is <code>null</code>. 350 * @exception IndexOutOfBoundsException If <code>off</code> is negative, 351 * <code>len</code> is negative, or <code>len</code> is greater than 352 * <code>b.length - off</code> 353 */ 354 public int read(byte b[], int off, int len) throws IOException { 355 return readBytes(b, off, len); 356 } 357 358 /** 359 * Reads up to <code>b.length</code> bytes of data from this file 360 * into an array of bytes. This method blocks until at least one byte 361 * of input is available. 362 * <p> 363 * Although <code>RandomAccessFile</code> is not a subclass of 364 * <code>InputStream</code>, this method behaves in exactly the 365 * same way as the {@link InputStream#read(byte[])} method of 366 * <code>InputStream</code>. 367 * 368 * @param b the buffer into which the data is read. 369 * @return the total number of bytes read into the buffer, or 370 * <code>-1</code> if there is no more data because the end of 371 * this file has been reached. 372 * @exception IOException If the first byte cannot be read for any reason 373 * other than end of file, or if the random access file has been closed, or if 374 * some other I/O error occurs. 375 * @exception NullPointerException If <code>b</code> is <code>null</code>. 376 */ 377 public int read(byte b[]) throws IOException { 378 return readBytes(b, 0, b.length); 379 } 380 381 /** 382 * Reads <code>b.length</code> bytes from this file into the byte 383 * array, starting at the current file pointer. This method reads 384 * repeatedly from the file until the requested number of bytes are 385 * read. This method blocks until the requested number of bytes are 386 * read, the end of the stream is detected, or an exception is thrown. 387 * 388 * @param b the buffer into which the data is read. 389 * @exception EOFException if this file reaches the end before reading 390 * all the bytes. 391 * @exception IOException if an I/O error occurs. 392 */ 393 public final void readFully(byte b[]) throws IOException { 394 readFully(b, 0, b.length); 395 } 396 397 /** 398 * Reads exactly <code>len</code> bytes from this file into the byte 399 * array, starting at the current file pointer. This method reads 400 * repeatedly from the file until the requested number of bytes are 401 * read. This method blocks until the requested number of bytes are 402 * read, the end of the stream is detected, or an exception is thrown. 403 * 404 * @param b the buffer into which the data is read. 405 * @param off the start offset of the data. 406 * @param len the number of bytes to read. 407 * @exception EOFException if this file reaches the end before reading 408 * all the bytes. 409 * @exception IOException if an I/O error occurs. 410 */ 411 public final void readFully(byte b[], int off, int len) throws IOException { 412 int n = 0; 413 do { 414 int count = this.read(b, off + n, len - n); 415 if (count < 0) 416 throw new EOFException(); 417 n += count; 418 } while (n < len); 419 } 420 421 /** 422 * Attempts to skip over <code>n</code> bytes of input discarding the 423 * skipped bytes. 424 * <p> 425 * 426 * This method may skip over some smaller number of bytes, possibly zero. 427 * This may result from any of a number of conditions; reaching end of 428 * file before <code>n</code> bytes have been skipped is only one 429 * possibility. This method never throws an <code>EOFException</code>. 430 * The actual number of bytes skipped is returned. If <code>n</code> 431 * is negative, no bytes are skipped. 432 * 433 * @param n the number of bytes to be skipped. 434 * @return the actual number of bytes skipped. 435 * @exception IOException if an I/O error occurs. 436 */ 437 public int skipBytes(int n) throws IOException { 438 long pos; 439 long len; 440 long newpos; 441 442 if (n <= 0) { 443 return 0; 444 } 445 pos = getFilePointer(); 446 len = length(); 447 newpos = pos + n; 448 if (newpos > len) { 449 newpos = len; 450 } 451 seek(newpos); 452 453 /* return the actual number of bytes skipped */ 454 return (int) (newpos - pos); 455 } 456 457 // 'Write' primitives 458 459 /** 460 * Writes the specified byte to this file. The write starts at 461 * the current file pointer. 462 * 463 * @param b the <code>byte</code> to be written. 464 * @exception IOException if an I/O error occurs. 465 */ 466 public native void write(int b) throws IOException; 467 468 /** 469 * Writes a sub array as a sequence of bytes. 470 * @param b the data to be written 471 472 * @param off the start offset in the data 473 * @param len the number of bytes that are written 474 * @exception IOException If an I/O error has occurred. 475 */ 476 private native void writeBytes(byte b[], int off, int len) throws IOException; 477 478 /** 479 * Writes <code>b.length</code> bytes from the specified byte array 480 * to this file, starting at the current file pointer. 481 * 482 * @param b the data. 483 * @exception IOException if an I/O error occurs. 484 */ 485 public void write(byte b[]) throws IOException { 486 writeBytes(b, 0, b.length); 487 } 488 489 /** 490 * Writes <code>len</code> bytes from the specified byte array 491 * starting at offset <code>off</code> to this file. 492 * 493 * @param b the data. 494 * @param off the start offset in the data. 495 * @param len the number of bytes to write. 496 * @exception IOException if an I/O error occurs. 497 */ 498 public void write(byte b[], int off, int len) throws IOException { 499 writeBytes(b, off, len); 500 } 501 502 // 'Random access' stuff 503 504 /** 505 * Returns the current offset in this file. 506 * 507 * @return the offset from the beginning of the file, in bytes, 508 * at which the next read or write occurs. 509 * @exception IOException if an I/O error occurs. 510 */ 511 public native long getFilePointer() throws IOException; 512 513 /** 514 * Sets the file-pointer offset, measured from the beginning of this 515 * file, at which the next read or write occurs. The offset may be 516 * set beyond the end of the file. Setting the offset beyond the end 517 * of the file does not change the file length. The file length will 518 * change only by writing after the offset has been set beyond the end 519 * of the file. 520 * 521 * @param pos the offset position, measured in bytes from the 522 * beginning of the file, at which to set the file 523 * pointer. 524 * @exception IOException if <code>pos</code> is less than 525 * <code>0</code> or if an I/O error occurs. 526 */ 527 public native void seek(long pos) throws IOException; 528 529 /** 530 * Returns the length of this file. 531 * 532 * @return the length of this file, measured in bytes. 533 * @exception IOException if an I/O error occurs. 534 */ 535 public native long length() throws IOException; 536 537 /** 538 * Sets the length of this file. 539 * 540 * <p> If the present length of the file as returned by the 541 * <code>length</code> method is greater than the <code>newLength</code> 542 * argument then the file will be truncated. In this case, if the file 543 * offset as returned by the <code>getFilePointer</code> method is greater 544 * than <code>newLength</code> then after this method returns the offset 545 * will be equal to <code>newLength</code>. 546 * 547 * <p> If the present length of the file as returned by the 548 * <code>length</code> method is smaller than the <code>newLength</code> 549 * argument then the file will be extended. In this case, the contents of 550 * the extended portion of the file are not defined. 551 * 552 * @param newLength The desired length of the file 553 * @exception IOException If an I/O error occurs 554 * @since 1.2 555 */ 556 public native void setLength(long newLength) throws IOException; 557 558 /** 559 * Closes this random access file stream and releases any system 560 * resources associated with the stream. A closed random access 561 * file cannot perform input or output operations and cannot be 562 * reopened. 563 * 564 * <p> If this file has an associated channel then the channel is closed 565 * as well. 566 * 567 * @exception IOException if an I/O error occurs. 568 * 569 * @revised 1.4 570 * @spec JSR-51 571 */ 572 public void close() throws IOException { 573 synchronized (closeLock) { 574 if (closed) { 575 return; 576 } 577 closed = true; 578 } 579 if (channel != null) { 580 /* 581 * Decrement FD use count associated with the channel. The FD use 582 * count is incremented whenever a new channel is obtained from 583 * this stream. 584 */ 585 fd.decrementAndGetUseCount(); 586 channel.close(); 587 } 588 589 /* 590 * Decrement FD use count associated with this stream. 591 * The count got incremented by FileDescriptor during its construction. 592 */ 593 fd.decrementAndGetUseCount(); 594 close0(); 595 } 596 597 // 598 // Some "reading/writing Java data types" methods stolen from 599 // DataInputStream and DataOutputStream. 600 // 601 602 /** 603 * Reads a <code>boolean</code> from this file. This method reads a 604 * single byte from the file, starting at the current file pointer. 605 * A value of <code>0</code> represents 606 * <code>false</code>. Any other value represents <code>true</code>. 607 * This method blocks until the byte is read, the end of the stream 608 * is detected, or an exception is thrown. 609 * 610 * @return the <code>boolean</code> value read. 611 * @exception EOFException if this file has reached the end. 612 * @exception IOException if an I/O error occurs. 613 */ 614 public final boolean readBoolean() throws IOException { 615 int ch = this.read(); 616 if (ch < 0) 617 throw new EOFException(); 618 return (ch != 0); 619 } 620 621 /** 622 * Reads a signed eight-bit value from this file. This method reads a 623 * byte from the file, starting from the current file pointer. 624 * If the byte read is <code>b</code>, where 625 * <code>0 <= b <= 255</code>, 626 * then the result is: 627 * <blockquote><pre> 628 * (byte)(b) 629 * </pre></blockquote> 630 * <p> 631 * This method blocks until the byte is read, the end of the stream 632 * is detected, or an exception is thrown. 633 * 634 * @return the next byte of this file as a signed eight-bit 635 * <code>byte</code>. 636 * @exception EOFException if this file has reached the end. 637 * @exception IOException if an I/O error occurs. 638 */ 639 public final byte readByte() throws IOException { 640 int ch = this.read(); 641 if (ch < 0) 642 throw new EOFException(); 643 return (byte)(ch); 644 } 645 646 /** 647 * Reads an unsigned eight-bit number from this file. This method reads 648 * a byte from this file, starting at the current file pointer, 649 * and returns that byte. 650 * <p> 651 * This method blocks until the byte is read, the end of the stream 652 * is detected, or an exception is thrown. 653 * 654 * @return the next byte of this file, interpreted as an unsigned 655 * eight-bit number. 656 * @exception EOFException if this file has reached the end. 657 * @exception IOException if an I/O error occurs. 658 */ 659 public final int readUnsignedByte() throws IOException { 660 int ch = this.read(); 661 if (ch < 0) 662 throw new EOFException(); 663 return ch; 664 } 665 666 /** 667 * Reads a signed 16-bit number from this file. The method reads two 668 * bytes from this file, starting at the current file pointer. 669 * If the two bytes read, in order, are 670 * <code>b1</code> and <code>b2</code>, where each of the two values is 671 * between <code>0</code> and <code>255</code>, inclusive, then the 672 * result is equal to: 673 * <blockquote><pre> 674 * (short)((b1 << 8) | b2) 675 * </pre></blockquote> 676 * <p> 677 * This method blocks until the two bytes are read, the end of the 678 * stream is detected, or an exception is thrown. 679 * 680 * @return the next two bytes of this file, interpreted as a signed 681 * 16-bit number. 682 * @exception EOFException if this file reaches the end before reading 683 * two bytes. 684 * @exception IOException if an I/O error occurs. 685 */ 686 public final short readShort() throws IOException { 687 int ch1 = this.read(); 688 int ch2 = this.read(); 689 if ((ch1 | ch2) < 0) 690 throw new EOFException(); 691 return (short)((ch1 << 8) + (ch2 << 0)); 692 } 693 694 /** 695 * Reads an unsigned 16-bit number from this file. This method reads 696 * two bytes from the file, starting at the current file pointer. 697 * If the bytes read, in order, are 698 * <code>b1</code> and <code>b2</code>, where 699 * <code>0 <= b1, b2 <= 255</code>, 700 * then the result is equal to: 701 * <blockquote><pre> 702 * (b1 << 8) | b2 703 * </pre></blockquote> 704 * <p> 705 * This method blocks until the two bytes are read, the end of the 706 * stream is detected, or an exception is thrown. 707 * 708 * @return the next two bytes of this file, interpreted as an unsigned 709 * 16-bit integer. 710 * @exception EOFException if this file reaches the end before reading 711 * two bytes. 712 * @exception IOException if an I/O error occurs. 713 */ 714 public final int readUnsignedShort() throws IOException { 715 int ch1 = this.read(); 716 int ch2 = this.read(); 717 if ((ch1 | ch2) < 0) 718 throw new EOFException(); 719 return (ch1 << 8) + (ch2 << 0); 720 } 721 722 /** 723 * Reads a character from this file. This method reads two 724 * bytes from the file, starting at the current file pointer. 725 * If the bytes read, in order, are 726 * <code>b1</code> and <code>b2</code>, where 727 * <code>0 <= b1, b2 <= 255</code>, 728 * then the result is equal to: 729 * <blockquote><pre> 730 * (char)((b1 << 8) | b2) 731 * </pre></blockquote> 732 * <p> 733 * This method blocks until the two bytes are read, the end of the 734 * stream is detected, or an exception is thrown. 735 * 736 * @return the next two bytes of this file, interpreted as a 737 * <code>char</code>. 738 * @exception EOFException if this file reaches the end before reading 739 * two bytes. 740 * @exception IOException if an I/O error occurs. 741 */ 742 public final char readChar() throws IOException { 743 int ch1 = this.read(); 744 int ch2 = this.read(); 745 if ((ch1 | ch2) < 0) 746 throw new EOFException(); 747 return (char)((ch1 << 8) + (ch2 << 0)); 748 } 749 750 /** 751 * Reads a signed 32-bit integer from this file. This method reads 4 752 * bytes from the file, starting at the current file pointer. 753 * If the bytes read, in order, are <code>b1</code>, 754 * <code>b2</code>, <code>b3</code>, and <code>b4</code>, where 755 * <code>0 <= b1, b2, b3, b4 <= 255</code>, 756 * then the result is equal to: 757 * <blockquote><pre> 758 * (b1 << 24) | (b2 << 16) + (b3 << 8) + b4 759 * </pre></blockquote> 760 * <p> 761 * This method blocks until the four bytes are read, the end of the 762 * stream is detected, or an exception is thrown. 763 * 764 * @return the next four bytes of this file, interpreted as an 765 * <code>int</code>. 766 * @exception EOFException if this file reaches the end before reading 767 * four bytes. 768 * @exception IOException if an I/O error occurs. 769 */ 770 public final int readInt() throws IOException { 771 int ch1 = this.read(); 772 int ch2 = this.read(); 773 int ch3 = this.read(); 774 int ch4 = this.read(); 775 if ((ch1 | ch2 | ch3 | ch4) < 0) 776 throw new EOFException(); 777 return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0)); 778 } 779 780 /** 781 * Reads a signed 64-bit integer from this file. This method reads eight 782 * bytes from the file, starting at the current file pointer. 783 * If the bytes read, in order, are 784 * <code>b1</code>, <code>b2</code>, <code>b3</code>, 785 * <code>b4</code>, <code>b5</code>, <code>b6</code>, 786 * <code>b7</code>, and <code>b8,</code> where: 787 * <blockquote><pre> 788 * 0 <= b1, b2, b3, b4, b5, b6, b7, b8 <=255, 789 * </pre></blockquote> 790 * <p> 791 * then the result is equal to: 792 * <p><blockquote><pre> 793 * ((long)b1 << 56) + ((long)b2 << 48) 794 * + ((long)b3 << 40) + ((long)b4 << 32) 795 * + ((long)b5 << 24) + ((long)b6 << 16) 796 * + ((long)b7 << 8) + b8 797 * </pre></blockquote> 798 * <p> 799 * This method blocks until the eight bytes are read, the end of the 800 * stream is detected, or an exception is thrown. 801 * 802 * @return the next eight bytes of this file, interpreted as a 803 * <code>long</code>. 804 * @exception EOFException if this file reaches the end before reading 805 * eight bytes. 806 * @exception IOException if an I/O error occurs. 807 */ 808 public final long readLong() throws IOException { 809 return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL); 810 } 811 812 /** 813 * Reads a <code>float</code> from this file. This method reads an 814 * <code>int</code> value, starting at the current file pointer, 815 * as if by the <code>readInt</code> method 816 * and then converts that <code>int</code> to a <code>float</code> 817 * using the <code>intBitsToFloat</code> method in class 818 * <code>Float</code>. 819 * <p> 820 * This method blocks until the four bytes are read, the end of the 821 * stream is detected, or an exception is thrown. 822 * 823 * @return the next four bytes of this file, interpreted as a 824 * <code>float</code>. 825 * @exception EOFException if this file reaches the end before reading 826 * four bytes. 827 * @exception IOException if an I/O error occurs. 828 * @see java.io.RandomAccessFile#readInt() 829 * @see java.lang.Float#intBitsToFloat(int) 830 */ 831 public final float readFloat() throws IOException { 832 return Float.intBitsToFloat(readInt()); 833 } 834 835 /** 836 * Reads a <code>double</code> from this file. This method reads a 837 * <code>long</code> value, starting at the current file pointer, 838 * as if by the <code>readLong</code> method 839 * and then converts that <code>long</code> to a <code>double</code> 840 * using the <code>longBitsToDouble</code> method in 841 * class <code>Double</code>. 842 * <p> 843 * This method blocks until the eight bytes are read, the end of the 844 * stream is detected, or an exception is thrown. 845 * 846 * @return the next eight bytes of this file, interpreted as a 847 * <code>double</code>. 848 * @exception EOFException if this file reaches the end before reading 849 * eight bytes. 850 * @exception IOException if an I/O error occurs. 851 * @see java.io.RandomAccessFile#readLong() 852 * @see java.lang.Double#longBitsToDouble(long) 853 */ 854 public final double readDouble() throws IOException { 855 return Double.longBitsToDouble(readLong()); 856 } 857 858 /** 859 * Reads the next line of text from this file. This method successively 860 * reads bytes from the file, starting at the current file pointer, 861 * until it reaches a line terminator or the end 862 * of the file. Each byte is converted into a character by taking the 863 * byte's value for the lower eight bits of the character and setting the 864 * high eight bits of the character to zero. This method does not, 865 * therefore, support the full Unicode character set. 866 * 867 * <p> A line of text is terminated by a carriage-return character 868 * (<code>'\r'</code>), a newline character (<code>'\n'</code>), a 869 * carriage-return character immediately followed by a newline character, 870 * or the end of the file. Line-terminating characters are discarded and 871 * are not included as part of the string returned. 872 * 873 * <p> This method blocks until a newline character is read, a carriage 874 * return and the byte following it are read (to see if it is a newline), 875 * the end of the file is reached, or an exception is thrown. 876 * 877 * @return the next line of text from this file, or null if end 878 * of file is encountered before even one byte is read. 879 * @exception IOException if an I/O error occurs. 880 */ 881 882 public final String readLine() throws IOException { 883 StringBuffer input = new StringBuffer(); 884 int c = -1; 885 boolean eol = false; 886 887 while (!eol) { 888 switch (c = read()) { 889 case -1: 890 case '\n': 891 eol = true; 892 break; 893 case '\r': 894 eol = true; 895 long cur = getFilePointer(); 896 if ((read()) != '\n') { 897 seek(cur); 898 } 899 break; 900 default: 901 input.append((char)c); 902 break; 903 } 904 } 905 906 if ((c == -1) && (input.length() == 0)) { 907 return null; 908 } 909 return input.toString(); 910 } 911 912 /** 913 * Reads in a string from this file. The string has been encoded 914 * using a 915 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a> 916 * format. 917 * <p> 918 * The first two bytes are read, starting from the current file 919 * pointer, as if by 920 * <code>readUnsignedShort</code>. This value gives the number of 921 * following bytes that are in the encoded string, not 922 * the length of the resulting string. The following bytes are then 923 * interpreted as bytes encoding characters in the modified UTF-8 format 924 * and are converted into characters. 925 * <p> 926 * This method blocks until all the bytes are read, the end of the 927 * stream is detected, or an exception is thrown. 928 * 929 * @return a Unicode string. 930 * @exception EOFException if this file reaches the end before 931 * reading all the bytes. 932 * @exception IOException if an I/O error occurs. 933 * @exception UTFDataFormatException if the bytes do not represent 934 * valid modified UTF-8 encoding of a Unicode string. 935 * @see java.io.RandomAccessFile#readUnsignedShort() 936 */ 937 public final String readUTF() throws IOException { 938 return DataInputStream.readUTF(this); 939 } 940 941 /** 942 * Writes a <code>boolean</code> to the file as a one-byte value. The 943 * value <code>true</code> is written out as the value 944 * <code>(byte)1</code>; the value <code>false</code> is written out 945 * as the value <code>(byte)0</code>. The write starts at 946 * the current position of the file pointer. 947 * 948 * @param v a <code>boolean</code> value to be written. 949 * @exception IOException if an I/O error occurs. 950 */ 951 public final void writeBoolean(boolean v) throws IOException { 952 write(v ? 1 : 0); 953 //written++; 954 } 955 956 /** 957 * Writes a <code>byte</code> to the file as a one-byte value. The 958 * write starts at the current position of the file pointer. 959 * 960 * @param v a <code>byte</code> value to be written. 961 * @exception IOException if an I/O error occurs. 962 */ 963 public final void writeByte(int v) throws IOException { 964 write(v); 965 //written++; 966 } 967 968 /** 969 * Writes a <code>short</code> to the file as two bytes, high byte first. 970 * The write starts at the current position of the file pointer. 971 * 972 * @param v a <code>short</code> to be written. 973 * @exception IOException if an I/O error occurs. 974 */ 975 public final void writeShort(int v) throws IOException { 976 write((v >>> 8) & 0xFF); 977 write((v >>> 0) & 0xFF); 978 //written += 2; 979 } 980 981 /** 982 * Writes a <code>char</code> to the file as a two-byte value, high 983 * byte first. The write starts at the current position of the 984 * file pointer. 985 * 986 * @param v a <code>char</code> value to be written. 987 * @exception IOException if an I/O error occurs. 988 */ 989 public final void writeChar(int v) throws IOException { 990 write((v >>> 8) & 0xFF); 991 write((v >>> 0) & 0xFF); 992 //written += 2; 993 } 994 995 /** 996 * Writes an <code>int</code> to the file as four bytes, high byte first. 997 * The write starts at the current position of the file pointer. 998 * 999 * @param v an <code>int</code> to be written. 1000 * @exception IOException if an I/O error occurs. 1001 */ 1002 public final void writeInt(int v) throws IOException { 1003 write((v >>> 24) & 0xFF); 1004 write((v >>> 16) & 0xFF); 1005 write((v >>> 8) & 0xFF); 1006 write((v >>> 0) & 0xFF); 1007 //written += 4; 1008 } 1009 1010 /** 1011 * Writes a <code>long</code> to the file as eight bytes, high byte first. 1012 * The write starts at the current position of the file pointer. 1013 * 1014 * @param v a <code>long</code> to be written. 1015 * @exception IOException if an I/O error occurs. 1016 */ 1017 public final void writeLong(long v) throws IOException { 1018 write((int)(v >>> 56) & 0xFF); 1019 write((int)(v >>> 48) & 0xFF); 1020 write((int)(v >>> 40) & 0xFF); 1021 write((int)(v >>> 32) & 0xFF); 1022 write((int)(v >>> 24) & 0xFF); 1023 write((int)(v >>> 16) & 0xFF); 1024 write((int)(v >>> 8) & 0xFF); 1025 write((int)(v >>> 0) & 0xFF); 1026 //written += 8; 1027 } 1028 1029 /** 1030 * Converts the float argument to an <code>int</code> using the 1031 * <code>floatToIntBits</code> method in class <code>Float</code>, 1032 * and then writes that <code>int</code> value to the file as a 1033 * four-byte quantity, high byte first. The write starts at the 1034 * current position of the file pointer. 1035 * 1036 * @param v a <code>float</code> value to be written. 1037 * @exception IOException if an I/O error occurs. 1038 * @see java.lang.Float#floatToIntBits(float) 1039 */ 1040 public final void writeFloat(float v) throws IOException { 1041 writeInt(Float.floatToIntBits(v)); 1042 } 1043 1044 /** 1045 * Converts the double argument to a <code>long</code> using the 1046 * <code>doubleToLongBits</code> method in class <code>Double</code>, 1047 * and then writes that <code>long</code> value to the file as an 1048 * eight-byte quantity, high byte first. The write starts at the current 1049 * position of the file pointer. 1050 * 1051 * @param v a <code>double</code> value to be written. 1052 * @exception IOException if an I/O error occurs. 1053 * @see java.lang.Double#doubleToLongBits(double) 1054 */ 1055 public final void writeDouble(double v) throws IOException { 1056 writeLong(Double.doubleToLongBits(v)); 1057 } 1058 1059 /** 1060 * Writes the string to the file as a sequence of bytes. Each 1061 * character in the string is written out, in sequence, by discarding 1062 * its high eight bits. The write starts at the current position of 1063 * the file pointer. 1064 * 1065 * @param s a string of bytes to be written. 1066 * @exception IOException if an I/O error occurs. 1067 */ 1068 public final void writeBytes(String s) throws IOException { 1069 int len = s.length(); 1070 byte[] b = new byte[len]; 1071 s.getBytes(0, len, b, 0); 1072 writeBytes(b, 0, len); 1073 } 1074 1075 /** 1076 * Writes a string to the file as a sequence of characters. Each 1077 * character is written to the data output stream as if by the 1078 * <code>writeChar</code> method. The write starts at the current 1079 * position of the file pointer. 1080 * 1081 * @param s a <code>String</code> value to be written. 1082 * @exception IOException if an I/O error occurs. 1083 * @see java.io.RandomAccessFile#writeChar(int) 1084 */ 1085 public final void writeChars(String s) throws IOException { 1086 int clen = s.length(); 1087 int blen = 2*clen; 1088 byte[] b = new byte[blen]; 1089 char[] c = new char[clen]; 1090 s.getChars(0, clen, c, 0); 1091 for (int i = 0, j = 0; i < clen; i++) { 1092 b[j++] = (byte)(c[i] >>> 8); 1093 b[j++] = (byte)(c[i] >>> 0); 1094 } 1095 writeBytes(b, 0, blen); 1096 } 1097 1098 /** 1099 * Writes a string to the file using 1100 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a> 1101 * encoding in a machine-independent manner. 1102 * <p> 1103 * First, two bytes are written to the file, starting at the 1104 * current file pointer, as if by the 1105 * <code>writeShort</code> method giving the number of bytes to 1106 * follow. This value is the number of bytes actually written out, 1107 * not the length of the string. Following the length, each character 1108 * of the string is output, in sequence, using the modified UTF-8 encoding 1109 * for each character. 1110 * 1111 * @param str a string to be written. 1112 * @exception IOException if an I/O error occurs. 1113 */ 1114 public final void writeUTF(String str) throws IOException { 1115 DataOutputStream.writeUTF(str, this); 1116 } 1117 1118 private static native void initIDs(); 1119 1120 private native void close0() throws IOException; 1121 1122 static { 1123 initIDs(); 1124 } 1125 }