1 /* 2 * Copyright (C) 2014 The Android Open Source Project 3 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. Oracle designates this 9 * particular file as subject to the "Classpath" exception as provided 10 * by Oracle in the LICENSE file that accompanied this code. 11 * 12 * This code is distributed in the hope that it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * version 2 for more details (a copy is included in the LICENSE file that 16 * accompanied this code). 17 * 18 * You should have received a copy of the GNU General Public License version 19 * 2 along with this work; if not, write to the Free Software Foundation, 20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 21 * 22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 23 * or visit www.oracle.com if you need additional information or have any 24 * questions. 25 */ 26 27 package java.io; 28 29 import java.nio.channels.FileChannel; 30 import sun.nio.ch.FileChannelImpl; 31 import sun.misc.IoTrace; 32 import android.system.ErrnoException; 33 import dalvik.system.CloseGuard; 34 import libcore.io.IoBridge; 35 import libcore.io.Libcore; 36 import static android.system.OsConstants.*; 37 38 39 /** 40 * Instances of this class support both reading and writing to a 41 * random access file. A random access file behaves like a large 42 * array of bytes stored in the file system. There is a kind of cursor, 43 * or index into the implied array, called the <em>file pointer</em>; 44 * input operations read bytes starting at the file pointer and advance 45 * the file pointer past the bytes read. If the random access file is 46 * created in read/write mode, then output operations are also available; 47 * output operations write bytes starting at the file pointer and advance 48 * the file pointer past the bytes written. Output operations that write 49 * past the current end of the implied array cause the array to be 50 * extended. The file pointer can be read by the 51 * <code>getFilePointer</code> method and set by the <code>seek</code> 52 * method. 53 * <p> 54 * It is generally true of all the reading routines in this class that 55 * if end-of-file is reached before the desired number of bytes has been 56 * read, an <code>EOFException</code> (which is a kind of 57 * <code>IOException</code>) is thrown. If any byte cannot be read for 58 * any reason other than end-of-file, an <code>IOException</code> other 59 * than <code>EOFException</code> is thrown. In particular, an 60 * <code>IOException</code> may be thrown if the stream has been closed. 61 * 62 * @author unascribed 63 * @since JDK1.0 64 */ 65 66 public class RandomAccessFile implements DataOutput, DataInput, Closeable { 67 68 private final CloseGuard guard = CloseGuard.get(); 69 private final byte[] scratch = new byte[8]; 70 private boolean syncMetadata = false; 71 private int mode; 72 73 private FileDescriptor fd; 74 private FileChannel channel = null; 75 private boolean rw; 76 77 /* The path of the referenced file */ 78 private final String path; 79 80 private Object closeLock = new Object(); 81 private volatile boolean closed = false; 82 83 /** 84 * Creates a random access file stream to read from, and optionally 85 * to write to, a file with the specified name. A new 86 * {@link FileDescriptor} object is created to represent the 87 * connection to the file. 88 * 89 * <p> The <tt>mode</tt> argument specifies the access mode with which the 90 * file is to be opened. The permitted values and their meanings are as 91 * specified for the <a 92 * href="#mode"><tt>RandomAccessFile(File,String)</tt></a> constructor. 93 * 94 * <p> 95 * If there is a security manager, its <code>checkRead</code> method 96 * is called with the <code>name</code> argument 97 * as its argument to see if read access to the file is allowed. 98 * If the mode allows writing, the security manager's 99 * <code>checkWrite</code> method 100 * is also called with the <code>name</code> argument 101 * as its argument to see if write access to the file is allowed. 102 * 103 * @param name the system-dependent filename 104 * @param mode the access <a href="#mode">mode</a> 105 * @exception IllegalArgumentException if the mode argument is not equal 106 * to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or 107 * <tt>"rwd"</tt> 108 * @exception FileNotFoundException 109 * if the mode is <tt>"r"</tt> but the given string does not 110 * denote an existing regular file, or if the mode begins with 111 * <tt>"rw"</tt> but the given string does not denote an 112 * existing, writable regular file and a new regular file of 113 * that name cannot be created, or if some other error occurs 114 * while opening or creating the file 115 * @exception SecurityException if a security manager exists and its 116 * <code>checkRead</code> method denies read access to the file 117 * or the mode is "rw" and the security manager's 118 * <code>checkWrite</code> method denies write access to the file 119 * @see java.lang.SecurityException 120 * @see java.lang.SecurityManager#checkRead(java.lang.String) 121 * @see java.lang.SecurityManager#checkWrite(java.lang.String) 122 * @revised 1.4 123 * @spec JSR-51 124 */ RandomAccessFile(String name, String mode)125 public RandomAccessFile(String name, String mode) 126 throws FileNotFoundException 127 { 128 this(name != null ? new File(name) : null, mode); 129 } 130 131 /** 132 * Creates a random access file stream to read from, and optionally to 133 * write to, the file specified by the {@link File} argument. A new {@link 134 * FileDescriptor} object is created to represent this file connection. 135 * 136 * <a name="mode"><p> The <tt>mode</tt> argument specifies the access mode 137 * in which the file is to be opened. The permitted values and their 138 * meanings are: 139 * 140 * <blockquote><table summary="Access mode permitted values and meanings"> 141 * <tr><th><p align="left">Value</p></th><th><p align="left">Meaning</p></th></tr> 142 * <tr><td valign="top"><tt>"r"</tt></td> 143 * <td> Open for reading only. Invoking any of the <tt>write</tt> 144 * methods of the resulting object will cause an {@link 145 * java.io.IOException} to be thrown. </td></tr> 146 * <tr><td valign="top"><tt>"rw"</tt></td> 147 * <td> Open for reading and writing. If the file does not already 148 * exist then an attempt will be made to create it. </td></tr> 149 * <tr><td valign="top"><tt>"rws"</tt></td> 150 * <td> Open for reading and writing, as with <tt>"rw"</tt>, and also 151 * require that every update to the file's content or metadata be 152 * written synchronously to the underlying storage device. </td></tr> 153 * <tr><td valign="top"><tt>"rwd" </tt></td> 154 * <td> Open for reading and writing, as with <tt>"rw"</tt>, and also 155 * require that every update to the file's content be written 156 * synchronously to the underlying storage device. </td></tr> 157 * </table></blockquote> 158 * 159 * The <tt>"rws"</tt> and <tt>"rwd"</tt> modes work much like the {@link 160 * java.nio.channels.FileChannel#force(boolean) force(boolean)} method of 161 * the {@link java.nio.channels.FileChannel} class, passing arguments of 162 * <tt>true</tt> and <tt>false</tt>, respectively, except that they always 163 * apply to every I/O operation and are therefore often more efficient. If 164 * the file resides on a local storage device then when an invocation of a 165 * method of this class returns it is guaranteed that all changes made to 166 * the file by that invocation will have been written to that device. This 167 * is useful for ensuring that critical information is not lost in the 168 * event of a system crash. If the file does not reside on a local device 169 * then no such guarantee is made. 170 * 171 * <p> The <tt>"rwd"</tt> mode can be used to reduce the number of I/O 172 * operations performed. Using <tt>"rwd"</tt> only requires updates to the 173 * file's content to be written to storage; using <tt>"rws"</tt> requires 174 * updates to both the file's content and its metadata to be written, which 175 * generally requires at least one more low-level I/O operation. 176 * 177 * <p> If there is a security manager, its <code>checkRead</code> method is 178 * called with the pathname of the <code>file</code> argument as its 179 * argument to see if read access to the file is allowed. If the mode 180 * allows writing, the security manager's <code>checkWrite</code> method is 181 * also called with the path argument to see if write access to the file is 182 * allowed. 183 * 184 * @param file the file object 185 * @param mode the access mode, as described 186 * <a href="#mode">above</a> 187 * @exception IllegalArgumentException if the mode argument is not equal 188 * to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or 189 * <tt>"rwd"</tt> 190 * @exception FileNotFoundException 191 * if the mode is <tt>"r"</tt> but the given file object does 192 * not denote an existing regular file, or if the mode begins 193 * with <tt>"rw"</tt> but the given file object does not denote 194 * an existing, writable regular file and a new regular file of 195 * that name cannot be created, or if some other error occurs 196 * while opening or creating the file 197 * @exception SecurityException if a security manager exists and its 198 * <code>checkRead</code> method denies read access to the file 199 * or the mode is "rw" and the security manager's 200 * <code>checkWrite</code> method denies write access to the file 201 * @see java.lang.SecurityManager#checkRead(java.lang.String) 202 * @see java.lang.SecurityManager#checkWrite(java.lang.String) 203 * @see java.nio.channels.FileChannel#force(boolean) 204 * @revised 1.4 205 * @spec JSR-51 206 */ RandomAccessFile(File file, String mode)207 public RandomAccessFile(File file, String mode) 208 throws FileNotFoundException 209 { 210 String name = (file != null ? file.getPath() : null); 211 this.mode = -1; 212 if (mode.equals("r")) { 213 this.mode = O_RDONLY; 214 } else if (mode.startsWith("rw")) { 215 // Android changed: Added. O_CREAT 216 this.mode = O_RDWR | O_CREAT; 217 rw = true; 218 if (mode.length() > 2) { 219 if (mode.equals("rws")) { 220 syncMetadata = true; 221 } else if (mode.equals("rwd")) { 222 // Android-changeD: Should this be O_DSYNC and the above O_SYNC ? 223 this.mode |= O_SYNC; 224 } else { 225 this.mode = -1; 226 } 227 } 228 } 229 230 if (this.mode < 0) { 231 throw new IllegalArgumentException("Illegal mode \"" + mode 232 + "\" must be one of " 233 + "\"r\", \"rw\", \"rws\"," 234 + " or \"rwd\""); 235 } 236 237 if (name == null) { 238 throw new NullPointerException("file == null"); 239 } 240 241 if (file.isInvalid()) { 242 throw new FileNotFoundException("Invalid file path"); 243 } 244 this.path = name; 245 246 // Android-changed: Use IoBridge.open() instead of open. 247 fd = IoBridge.open(file.getPath(), this.mode); 248 if (syncMetadata) { 249 try { 250 fd.sync(); 251 } catch (IOException e) { 252 // Ignored 253 } 254 } 255 guard.open("close"); 256 } 257 258 /** 259 * Returns the opaque file descriptor object associated with this 260 * stream. </p> 261 * 262 * @return the file descriptor object associated with this stream. 263 * @exception IOException if an I/O error occurs. 264 * @see java.io.FileDescriptor 265 */ getFD()266 public final FileDescriptor getFD() throws IOException { 267 if (fd != null) return fd; 268 throw new IOException(); 269 } 270 271 /** 272 * Returns the unique {@link java.nio.channels.FileChannel FileChannel} 273 * object associated with this file. 274 * 275 * <p> The {@link java.nio.channels.FileChannel#position() 276 * </code>position<code>} of the returned channel will always be equal to 277 * this object's file-pointer offset as returned by the {@link 278 * #getFilePointer getFilePointer} method. Changing this object's 279 * file-pointer offset, whether explicitly or by reading or writing bytes, 280 * will change the position of the channel, and vice versa. Changing the 281 * file's length via this object will change the length seen via the file 282 * channel, and vice versa. 283 * 284 * @return the file channel associated with this file 285 * 286 * @since 1.4 287 * @spec JSR-51 288 */ getChannel()289 public final FileChannel getChannel() { 290 synchronized (this) { 291 if (channel == null) { 292 channel = FileChannelImpl.open(fd, path, true, rw, this); 293 } 294 return channel; 295 } 296 } 297 298 /** 299 * Reads a byte of data from this file. The byte is returned as an 300 * integer in the range 0 to 255 (<code>0x00-0x0ff</code>). This 301 * method blocks if no input is yet available. 302 * <p> 303 * Although <code>RandomAccessFile</code> is not a subclass of 304 * <code>InputStream</code>, this method behaves in exactly the same 305 * way as the {@link InputStream#read()} method of 306 * <code>InputStream</code>. 307 * 308 * @return the next byte of data, or <code>-1</code> if the end of the 309 * file has been reached. 310 * @exception IOException if an I/O error occurs. Not thrown if 311 * end-of-file has been reached. 312 */ read()313 public int read() throws IOException { 314 return (read(scratch, 0, 1) != -1) ? scratch[0] & 0xff : -1; 315 } 316 317 /** 318 * Reads a sub array as a sequence of bytes. 319 * @param b the buffer into which the data is read. 320 * @param off the start offset of the data. 321 * @param len the number of bytes to read. 322 * @exception IOException If an I/O error has occurred. 323 */ readBytes(byte b[], int off, int len)324 private int readBytes(byte b[], int off, int len) throws IOException { 325 return IoBridge.read(fd, b, off, len); 326 } 327 328 /** 329 * Reads up to <code>len</code> bytes of data from this file into an 330 * array of bytes. This method blocks until at least one byte of input 331 * is available. 332 * <p> 333 * Although <code>RandomAccessFile</code> is not a subclass of 334 * <code>InputStream</code>, this method behaves in exactly the 335 * same way as the {@link InputStream#read(byte[], int, int)} method of 336 * <code>InputStream</code>. 337 * 338 * @param b the buffer into which the data is read. 339 * @param off the start offset in array <code>b</code> 340 * at which the data is written. 341 * @param len the maximum number of bytes read. 342 * @return the total number of bytes read into the buffer, or 343 * <code>-1</code> if there is no more data because the end of 344 * the file has been reached. 345 * @exception IOException If the first byte cannot be read for any reason 346 * other than end of file, or if the random access file has been closed, or if 347 * some other I/O error occurs. 348 * @exception NullPointerException If <code>b</code> is <code>null</code>. 349 * @exception IndexOutOfBoundsException If <code>off</code> is negative, 350 * <code>len</code> is negative, or <code>len</code> is greater than 351 * <code>b.length - off</code> 352 */ read(byte b[], int off, int len)353 public int read(byte b[], int off, int len) throws IOException { 354 return readBytes(b, off, len); 355 } 356 357 /** 358 * Reads up to <code>b.length</code> bytes of data from this file 359 * into an array of bytes. This method blocks until at least one byte 360 * of input is available. 361 * <p> 362 * Although <code>RandomAccessFile</code> is not a subclass of 363 * <code>InputStream</code>, this method behaves in exactly the 364 * same way as the {@link InputStream#read(byte[])} method of 365 * <code>InputStream</code>. 366 * 367 * @param b the buffer into which the data is read. 368 * @return the total number of bytes read into the buffer, or 369 * <code>-1</code> if there is no more data because the end of 370 * this file has been reached. 371 * @exception IOException If the first byte cannot be read for any reason 372 * other than end of file, or if the random access file has been closed, or if 373 * some other I/O error occurs. 374 * @exception NullPointerException If <code>b</code> is <code>null</code>. 375 */ read(byte b[])376 public int read(byte b[]) throws IOException { 377 return readBytes(b, 0, b.length); 378 } 379 380 /** 381 * Reads <code>b.length</code> bytes from this file into the byte 382 * array, starting at the current file pointer. This method reads 383 * repeatedly from the file until the requested number of bytes are 384 * read. This method blocks until the requested number of bytes are 385 * read, the end of the stream is detected, or an exception is thrown. 386 * 387 * @param b the buffer into which the data is read. 388 * @exception EOFException if this file reaches the end before reading 389 * all the bytes. 390 * @exception IOException if an I/O error occurs. 391 */ readFully(byte b[])392 public final void readFully(byte b[]) throws IOException { 393 readFully(b, 0, b.length); 394 } 395 396 /** 397 * Reads exactly <code>len</code> bytes from this file into the byte 398 * array, starting at the current file pointer. This method reads 399 * repeatedly from the file until the requested number of bytes are 400 * read. This method blocks until the requested number of bytes are 401 * read, the end of the stream is detected, or an exception is thrown. 402 * 403 * @param b the buffer into which the data is read. 404 * @param off the start offset of the data. 405 * @param len the number of bytes to read. 406 * @exception EOFException if this file reaches the end before reading 407 * all the bytes. 408 * @exception IOException if an I/O error occurs. 409 */ readFully(byte b[], int off, int len)410 public final void readFully(byte b[], int off, int len) throws IOException { 411 int n = 0; 412 do { 413 int count = this.read(b, off + n, len - n); 414 if (count < 0) 415 throw new EOFException(); 416 n += count; 417 } while (n < len); 418 } 419 420 /** 421 * Attempts to skip over <code>n</code> bytes of input discarding the 422 * skipped bytes. 423 * <p> 424 * 425 * This method may skip over some smaller number of bytes, possibly zero. 426 * This may result from any of a number of conditions; reaching end of 427 * file before <code>n</code> bytes have been skipped is only one 428 * possibility. This method never throws an <code>EOFException</code>. 429 * The actual number of bytes skipped is returned. If <code>n</code> 430 * is negative, no bytes are skipped. 431 * 432 * @param n the number of bytes to be skipped. 433 * @return the actual number of bytes skipped. 434 * @exception IOException if an I/O error occurs. 435 */ skipBytes(int n)436 public int skipBytes(int n) throws IOException { 437 long pos; 438 long len; 439 long newpos; 440 441 if (n <= 0) { 442 return 0; 443 } 444 pos = getFilePointer(); 445 len = length(); 446 newpos = pos + n; 447 if (newpos > len) { 448 newpos = len; 449 } 450 seek(newpos); 451 452 /* return the actual number of bytes skipped */ 453 return (int) (newpos - pos); 454 } 455 456 // 'Write' primitives 457 458 /** 459 * Writes the specified byte to this file. The write starts at 460 * the current file pointer. 461 * 462 * @param b the <code>byte</code> to be written. 463 * @exception IOException if an I/O error occurs. 464 */ write(int b)465 public void write(int b) throws IOException { 466 scratch[0] = (byte) (b & 0xff); 467 write(scratch, 0, 1); 468 } 469 470 /** 471 * Writes a sub array as a sequence of bytes. 472 * @param b the data to be written 473 * @param off the start offset in the data 474 * @param len the number of bytes that are written 475 * @exception IOException If an I/O error has occurred. 476 */ writeBytes(byte b[], int off, int len)477 private void writeBytes(byte b[], int off, int len) throws IOException { 478 IoBridge.write(fd, b, off, len); 479 // if we are in "rws" mode, attempt to sync file+metadata 480 if (syncMetadata) { 481 fd.sync(); 482 } 483 } 484 485 /** 486 * Writes <code>b.length</code> bytes from the specified byte array 487 * to this file, starting at the current file pointer. 488 * 489 * @param b the data. 490 * @exception IOException if an I/O error occurs. 491 */ write(byte b[])492 public void write(byte b[]) throws IOException { 493 writeBytes(b, 0, b.length); 494 } 495 496 /** 497 * Writes <code>len</code> bytes from the specified byte array 498 * starting at offset <code>off</code> to this file. 499 * 500 * @param b the data. 501 * @param off the start offset in the data. 502 * @param len the number of bytes to write. 503 * @exception IOException if an I/O error occurs. 504 */ write(byte b[], int off, int len)505 public void write(byte b[], int off, int len) throws IOException { 506 writeBytes(b, off, len); 507 } 508 509 // 'Random access' stuff 510 511 /** 512 * Returns the current offset in this file. 513 * 514 * @return the offset from the beginning of the file, in bytes, 515 * at which the next read or write occurs. 516 * @exception IOException if an I/O error occurs. 517 */ getFilePointer()518 public long getFilePointer() throws IOException { 519 try { 520 return Libcore.os.lseek(fd, 0L, SEEK_CUR); 521 } catch (ErrnoException errnoException) { 522 throw errnoException.rethrowAsIOException(); 523 } 524 } 525 526 /** 527 * Sets the file-pointer offset, measured from the beginning of this 528 * file, at which the next read or write occurs. The offset may be 529 * set beyond the end of the file. Setting the offset beyond the end 530 * of the file does not change the file length. The file length will 531 * change only by writing after the offset has been set beyond the end 532 * of the file. 533 * 534 * @param offset the offset position, measured in bytes from the 535 * beginning of the file, at which to set the file 536 * pointer. 537 * @exception IOException if <code>pos</code> is less than 538 * <code>0</code> or if an I/O error occurs. 539 */ seek(long offset)540 public void seek(long offset) throws IOException { 541 if (offset < 0) { 542 throw new IOException("offset < 0: " + offset); 543 } 544 try { 545 Libcore.os.lseek(fd, offset, SEEK_SET); 546 } catch (ErrnoException errnoException) { 547 throw errnoException.rethrowAsIOException(); 548 } 549 } 550 551 /** 552 * Returns the length of this file. 553 * 554 * @return the length of this file, measured in bytes. 555 * @exception IOException if an I/O error occurs. 556 */ length()557 public long length() throws IOException { 558 try { 559 return Libcore.os.fstat(fd).st_size; 560 } catch (ErrnoException errnoException) { 561 throw errnoException.rethrowAsIOException(); 562 } 563 } 564 565 /** 566 * Sets the length of this file. 567 * 568 * <p> If the present length of the file as returned by the 569 * <code>length</code> method is greater than the <code>newLength</code> 570 * argument then the file will be truncated. In this case, if the file 571 * offset as returned by the <code>getFilePointer</code> method is greater 572 * than <code>newLength</code> then after this method returns the offset 573 * will be equal to <code>newLength</code>. 574 * 575 * <p> If the present length of the file as returned by the 576 * <code>length</code> method is smaller than the <code>newLength</code> 577 * argument then the file will be extended. In this case, the contents of 578 * the extended portion of the file are not defined. 579 * 580 * @param newLength The desired length of the file 581 * @exception IOException If an I/O error occurs 582 * @since 1.2 583 */ setLength(long newLength)584 public void setLength(long newLength) throws IOException { 585 if (newLength < 0) { 586 throw new IllegalArgumentException("newLength < 0"); 587 } 588 try { 589 Libcore.os.ftruncate(fd, newLength); 590 } catch (ErrnoException errnoException) { 591 throw errnoException.rethrowAsIOException(); 592 } 593 594 long filePointer = getFilePointer(); 595 if (filePointer > newLength) { 596 seek(newLength); 597 } 598 // if we are in "rws" mode, attempt to sync file+metadata 599 if (syncMetadata) { 600 fd.sync(); 601 } 602 } 603 604 605 /** 606 * Closes this random access file stream and releases any system 607 * resources associated with the stream. A closed random access 608 * file cannot perform input or output operations and cannot be 609 * reopened. 610 * 611 * <p> If this file has an associated channel then the channel is closed 612 * as well. 613 * 614 * @exception IOException if an I/O error occurs. 615 * 616 * @revised 1.4 617 * @spec JSR-51 618 */ close()619 public void close() throws IOException { 620 guard.close(); 621 synchronized (closeLock) { 622 if (closed) { 623 return; 624 } 625 closed = true; 626 } 627 628 if (channel != null && channel.isOpen()) { 629 channel.close(); 630 } 631 IoBridge.closeAndSignalBlockedThreads(fd); 632 } 633 634 // 635 // Some "reading/writing Java data types" methods stolen from 636 // DataInputStream and DataOutputStream. 637 // 638 639 /** 640 * Reads a <code>boolean</code> from this file. This method reads a 641 * single byte from the file, starting at the current file pointer. 642 * A value of <code>0</code> represents 643 * <code>false</code>. Any other value represents <code>true</code>. 644 * This method blocks until the byte is read, the end of the stream 645 * is detected, or an exception is thrown. 646 * 647 * @return the <code>boolean</code> value read. 648 * @exception EOFException if this file has reached the end. 649 * @exception IOException if an I/O error occurs. 650 */ readBoolean()651 public final boolean readBoolean() throws IOException { 652 int ch = this.read(); 653 if (ch < 0) 654 throw new EOFException(); 655 return (ch != 0); 656 } 657 658 /** 659 * Reads a signed eight-bit value from this file. This method reads a 660 * byte from the file, starting from the current file pointer. 661 * If the byte read is <code>b</code>, where 662 * <code>0 <= b <= 255</code>, 663 * then the result is: 664 * <blockquote><pre> 665 * (byte)(b) 666 * </pre></blockquote> 667 * <p> 668 * This method blocks until the byte is read, the end of the stream 669 * is detected, or an exception is thrown. 670 * 671 * @return the next byte of this file as a signed eight-bit 672 * <code>byte</code>. 673 * @exception EOFException if this file has reached the end. 674 * @exception IOException if an I/O error occurs. 675 */ readByte()676 public final byte readByte() throws IOException { 677 int ch = this.read(); 678 if (ch < 0) 679 throw new EOFException(); 680 return (byte)(ch); 681 } 682 683 /** 684 * Reads an unsigned eight-bit number from this file. This method reads 685 * a byte from this file, starting at the current file pointer, 686 * and returns that byte. 687 * <p> 688 * This method blocks until the byte is read, the end of the stream 689 * is detected, or an exception is thrown. 690 * 691 * @return the next byte of this file, interpreted as an unsigned 692 * eight-bit number. 693 * @exception EOFException if this file has reached the end. 694 * @exception IOException if an I/O error occurs. 695 */ readUnsignedByte()696 public final int readUnsignedByte() throws IOException { 697 int ch = this.read(); 698 if (ch < 0) 699 throw new EOFException(); 700 return ch; 701 } 702 703 /** 704 * Reads a signed 16-bit number from this file. The method reads two 705 * bytes from this file, starting at the current file pointer. 706 * If the two bytes read, in order, are 707 * <code>b1</code> and <code>b2</code>, where each of the two values is 708 * between <code>0</code> and <code>255</code>, inclusive, then the 709 * result is equal to: 710 * <blockquote><pre> 711 * (short)((b1 << 8) | b2) 712 * </pre></blockquote> 713 * <p> 714 * This method blocks until the two bytes are read, the end of the 715 * stream is detected, or an exception is thrown. 716 * 717 * @return the next two bytes of this file, interpreted as a signed 718 * 16-bit number. 719 * @exception EOFException if this file reaches the end before reading 720 * two bytes. 721 * @exception IOException if an I/O error occurs. 722 */ readShort()723 public final short readShort() throws IOException { 724 int ch1 = this.read(); 725 int ch2 = this.read(); 726 if ((ch1 | ch2) < 0) 727 throw new EOFException(); 728 return (short)((ch1 << 8) + (ch2 << 0)); 729 } 730 731 /** 732 * Reads an unsigned 16-bit number from this file. This method reads 733 * two bytes from the file, starting at the current file pointer. 734 * If the bytes read, in order, are 735 * <code>b1</code> and <code>b2</code>, where 736 * <code>0 <= b1, b2 <= 255</code>, 737 * then the result is equal to: 738 * <blockquote><pre> 739 * (b1 << 8) | b2 740 * </pre></blockquote> 741 * <p> 742 * This method blocks until the two bytes are read, the end of the 743 * stream is detected, or an exception is thrown. 744 * 745 * @return the next two bytes of this file, interpreted as an unsigned 746 * 16-bit integer. 747 * @exception EOFException if this file reaches the end before reading 748 * two bytes. 749 * @exception IOException if an I/O error occurs. 750 */ readUnsignedShort()751 public final int readUnsignedShort() throws IOException { 752 int ch1 = this.read(); 753 int ch2 = this.read(); 754 if ((ch1 | ch2) < 0) 755 throw new EOFException(); 756 return (ch1 << 8) + (ch2 << 0); 757 } 758 759 /** 760 * Reads a character from this file. This method reads two 761 * bytes from the file, starting at the current file pointer. 762 * If the bytes read, in order, are 763 * <code>b1</code> and <code>b2</code>, where 764 * <code>0 <= b1, b2 <= 255</code>, 765 * then the result is equal to: 766 * <blockquote><pre> 767 * (char)((b1 << 8) | b2) 768 * </pre></blockquote> 769 * <p> 770 * This method blocks until the two bytes are read, the end of the 771 * stream is detected, or an exception is thrown. 772 * 773 * @return the next two bytes of this file, interpreted as a 774 * <code>char</code>. 775 * @exception EOFException if this file reaches the end before reading 776 * two bytes. 777 * @exception IOException if an I/O error occurs. 778 */ readChar()779 public final char readChar() throws IOException { 780 int ch1 = this.read(); 781 int ch2 = this.read(); 782 if ((ch1 | ch2) < 0) 783 throw new EOFException(); 784 return (char)((ch1 << 8) + (ch2 << 0)); 785 } 786 787 /** 788 * Reads a signed 32-bit integer from this file. This method reads 4 789 * bytes from the file, starting at the current file pointer. 790 * If the bytes read, in order, are <code>b1</code>, 791 * <code>b2</code>, <code>b3</code>, and <code>b4</code>, where 792 * <code>0 <= b1, b2, b3, b4 <= 255</code>, 793 * then the result is equal to: 794 * <blockquote><pre> 795 * (b1 << 24) | (b2 << 16) + (b3 << 8) + b4 796 * </pre></blockquote> 797 * <p> 798 * This method blocks until the four bytes are read, the end of the 799 * stream is detected, or an exception is thrown. 800 * 801 * @return the next four bytes of this file, interpreted as an 802 * <code>int</code>. 803 * @exception EOFException if this file reaches the end before reading 804 * four bytes. 805 * @exception IOException if an I/O error occurs. 806 */ readInt()807 public final int readInt() throws IOException { 808 int ch1 = this.read(); 809 int ch2 = this.read(); 810 int ch3 = this.read(); 811 int ch4 = this.read(); 812 if ((ch1 | ch2 | ch3 | ch4) < 0) 813 throw new EOFException(); 814 return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0)); 815 } 816 817 /** 818 * Reads a signed 64-bit integer from this file. This method reads eight 819 * bytes from the file, starting at the current file pointer. 820 * If the bytes read, in order, are 821 * <code>b1</code>, <code>b2</code>, <code>b3</code>, 822 * <code>b4</code>, <code>b5</code>, <code>b6</code>, 823 * <code>b7</code>, and <code>b8,</code> where: 824 * <blockquote><pre> 825 * 0 <= b1, b2, b3, b4, b5, b6, b7, b8 <=255, 826 * </pre></blockquote> 827 * <p> 828 * then the result is equal to: 829 * <p><blockquote><pre> 830 * ((long)b1 << 56) + ((long)b2 << 48) 831 * + ((long)b3 << 40) + ((long)b4 << 32) 832 * + ((long)b5 << 24) + ((long)b6 << 16) 833 * + ((long)b7 << 8) + b8 834 * </pre></blockquote> 835 * <p> 836 * This method blocks until the eight bytes are read, the end of the 837 * stream is detected, or an exception is thrown. 838 * 839 * @return the next eight bytes of this file, interpreted as a 840 * <code>long</code>. 841 * @exception EOFException if this file reaches the end before reading 842 * eight bytes. 843 * @exception IOException if an I/O error occurs. 844 */ readLong()845 public final long readLong() throws IOException { 846 return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL); 847 } 848 849 /** 850 * Reads a <code>float</code> from this file. This method reads an 851 * <code>int</code> value, starting at the current file pointer, 852 * as if by the <code>readInt</code> method 853 * and then converts that <code>int</code> to a <code>float</code> 854 * using the <code>intBitsToFloat</code> method in class 855 * <code>Float</code>. 856 * <p> 857 * This method blocks until the four bytes are read, the end of the 858 * stream is detected, or an exception is thrown. 859 * 860 * @return the next four bytes of this file, interpreted as a 861 * <code>float</code>. 862 * @exception EOFException if this file reaches the end before reading 863 * four bytes. 864 * @exception IOException if an I/O error occurs. 865 * @see java.io.RandomAccessFile#readInt() 866 * @see java.lang.Float#intBitsToFloat(int) 867 */ readFloat()868 public final float readFloat() throws IOException { 869 return Float.intBitsToFloat(readInt()); 870 } 871 872 /** 873 * Reads a <code>double</code> from this file. This method reads a 874 * <code>long</code> value, starting at the current file pointer, 875 * as if by the <code>readLong</code> method 876 * and then converts that <code>long</code> to a <code>double</code> 877 * using the <code>longBitsToDouble</code> method in 878 * class <code>Double</code>. 879 * <p> 880 * This method blocks until the eight bytes are read, the end of the 881 * stream is detected, or an exception is thrown. 882 * 883 * @return the next eight bytes of this file, interpreted as a 884 * <code>double</code>. 885 * @exception EOFException if this file reaches the end before reading 886 * eight bytes. 887 * @exception IOException if an I/O error occurs. 888 * @see java.io.RandomAccessFile#readLong() 889 * @see java.lang.Double#longBitsToDouble(long) 890 */ readDouble()891 public final double readDouble() throws IOException { 892 return Double.longBitsToDouble(readLong()); 893 } 894 895 /** 896 * Reads the next line of text from this file. This method successively 897 * reads bytes from the file, starting at the current file pointer, 898 * until it reaches a line terminator or the end 899 * of the file. Each byte is converted into a character by taking the 900 * byte's value for the lower eight bits of the character and setting the 901 * high eight bits of the character to zero. This method does not, 902 * therefore, support the full Unicode character set. 903 * 904 * <p> A line of text is terminated by a carriage-return character 905 * (<code>'\r'</code>), a newline character (<code>'\n'</code>), a 906 * carriage-return character immediately followed by a newline character, 907 * or the end of the file. Line-terminating characters are discarded and 908 * are not included as part of the string returned. 909 * 910 * <p> This method blocks until a newline character is read, a carriage 911 * return and the byte following it are read (to see if it is a newline), 912 * the end of the file is reached, or an exception is thrown. 913 * 914 * @return the next line of text from this file, or null if end 915 * of file is encountered before even one byte is read. 916 * @exception IOException if an I/O error occurs. 917 */ 918 readLine()919 public final String readLine() throws IOException { 920 StringBuffer input = new StringBuffer(); 921 int c = -1; 922 boolean eol = false; 923 924 while (!eol) { 925 switch (c = read()) { 926 case -1: 927 case '\n': 928 eol = true; 929 break; 930 case '\r': 931 eol = true; 932 long cur = getFilePointer(); 933 if ((read()) != '\n') { 934 seek(cur); 935 } 936 break; 937 default: 938 input.append((char)c); 939 break; 940 } 941 } 942 943 if ((c == -1) && (input.length() == 0)) { 944 return null; 945 } 946 return input.toString(); 947 } 948 949 /** 950 * Reads in a string from this file. The string has been encoded 951 * using a 952 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a> 953 * format. 954 * <p> 955 * The first two bytes are read, starting from the current file 956 * pointer, as if by 957 * <code>readUnsignedShort</code>. This value gives the number of 958 * following bytes that are in the encoded string, not 959 * the length of the resulting string. The following bytes are then 960 * interpreted as bytes encoding characters in the modified UTF-8 format 961 * and are converted into characters. 962 * <p> 963 * This method blocks until all the bytes are read, the end of the 964 * stream is detected, or an exception is thrown. 965 * 966 * @return a Unicode string. 967 * @exception EOFException if this file reaches the end before 968 * reading all the bytes. 969 * @exception IOException if an I/O error occurs. 970 * @exception UTFDataFormatException if the bytes do not represent 971 * valid modified UTF-8 encoding of a Unicode string. 972 * @see java.io.RandomAccessFile#readUnsignedShort() 973 */ readUTF()974 public final String readUTF() throws IOException { 975 return DataInputStream.readUTF(this); 976 } 977 978 /** 979 * Writes a <code>boolean</code> to the file as a one-byte value. The 980 * value <code>true</code> is written out as the value 981 * <code>(byte)1</code>; the value <code>false</code> is written out 982 * as the value <code>(byte)0</code>. The write starts at 983 * the current position of the file pointer. 984 * 985 * @param v a <code>boolean</code> value to be written. 986 * @exception IOException if an I/O error occurs. 987 */ writeBoolean(boolean v)988 public final void writeBoolean(boolean v) throws IOException { 989 write(v ? 1 : 0); 990 //written++; 991 } 992 993 /** 994 * Writes a <code>byte</code> to the file as a one-byte value. The 995 * write starts at the current position of the file pointer. 996 * 997 * @param v a <code>byte</code> value to be written. 998 * @exception IOException if an I/O error occurs. 999 */ writeByte(int v)1000 public final void writeByte(int v) throws IOException { 1001 write(v); 1002 //written++; 1003 } 1004 1005 /** 1006 * Writes a <code>short</code> to the file as two bytes, high byte first. 1007 * The write starts at the current position of the file pointer. 1008 * 1009 * @param v a <code>short</code> to be written. 1010 * @exception IOException if an I/O error occurs. 1011 */ writeShort(int v)1012 public final void writeShort(int v) throws IOException { 1013 write((v >>> 8) & 0xFF); 1014 write((v >>> 0) & 0xFF); 1015 //written += 2; 1016 } 1017 1018 /** 1019 * Writes a <code>char</code> to the file as a two-byte value, high 1020 * byte first. The write starts at the current position of the 1021 * file pointer. 1022 * 1023 * @param v a <code>char</code> value to be written. 1024 * @exception IOException if an I/O error occurs. 1025 */ writeChar(int v)1026 public final void writeChar(int v) throws IOException { 1027 write((v >>> 8) & 0xFF); 1028 write((v >>> 0) & 0xFF); 1029 //written += 2; 1030 } 1031 1032 /** 1033 * Writes an <code>int</code> to the file as four bytes, high byte first. 1034 * The write starts at the current position of the file pointer. 1035 * 1036 * @param v an <code>int</code> to be written. 1037 * @exception IOException if an I/O error occurs. 1038 */ writeInt(int v)1039 public final void writeInt(int v) throws IOException { 1040 write((v >>> 24) & 0xFF); 1041 write((v >>> 16) & 0xFF); 1042 write((v >>> 8) & 0xFF); 1043 write((v >>> 0) & 0xFF); 1044 //written += 4; 1045 } 1046 1047 /** 1048 * Writes a <code>long</code> to the file as eight bytes, high byte first. 1049 * The write starts at the current position of the file pointer. 1050 * 1051 * @param v a <code>long</code> to be written. 1052 * @exception IOException if an I/O error occurs. 1053 */ writeLong(long v)1054 public final void writeLong(long v) throws IOException { 1055 write((int)(v >>> 56) & 0xFF); 1056 write((int)(v >>> 48) & 0xFF); 1057 write((int)(v >>> 40) & 0xFF); 1058 write((int)(v >>> 32) & 0xFF); 1059 write((int)(v >>> 24) & 0xFF); 1060 write((int)(v >>> 16) & 0xFF); 1061 write((int)(v >>> 8) & 0xFF); 1062 write((int)(v >>> 0) & 0xFF); 1063 //written += 8; 1064 } 1065 1066 /** 1067 * Converts the float argument to an <code>int</code> using the 1068 * <code>floatToIntBits</code> method in class <code>Float</code>, 1069 * and then writes that <code>int</code> value to the file as a 1070 * four-byte quantity, high byte first. The write starts at the 1071 * current position of the file pointer. 1072 * 1073 * @param v a <code>float</code> value to be written. 1074 * @exception IOException if an I/O error occurs. 1075 * @see java.lang.Float#floatToIntBits(float) 1076 */ writeFloat(float v)1077 public final void writeFloat(float v) throws IOException { 1078 writeInt(Float.floatToIntBits(v)); 1079 } 1080 1081 /** 1082 * Converts the double argument to a <code>long</code> using the 1083 * <code>doubleToLongBits</code> method in class <code>Double</code>, 1084 * and then writes that <code>long</code> value to the file as an 1085 * eight-byte quantity, high byte first. The write starts at the current 1086 * position of the file pointer. 1087 * 1088 * @param v a <code>double</code> value to be written. 1089 * @exception IOException if an I/O error occurs. 1090 * @see java.lang.Double#doubleToLongBits(double) 1091 */ writeDouble(double v)1092 public final void writeDouble(double v) throws IOException { 1093 writeLong(Double.doubleToLongBits(v)); 1094 } 1095 1096 /** 1097 * Writes the string to the file as a sequence of bytes. Each 1098 * character in the string is written out, in sequence, by discarding 1099 * its high eight bits. The write starts at the current position of 1100 * the file pointer. 1101 * 1102 * @param s a string of bytes to be written. 1103 * @exception IOException if an I/O error occurs. 1104 */ writeBytes(String s)1105 public final void writeBytes(String s) throws IOException { 1106 int len = s.length(); 1107 byte[] b = new byte[len]; 1108 s.getBytes(0, len, b, 0); 1109 writeBytes(b, 0, len); 1110 } 1111 1112 /** 1113 * Writes a string to the file as a sequence of characters. Each 1114 * character is written to the data output stream as if by the 1115 * <code>writeChar</code> method. The write starts at the current 1116 * position of the file pointer. 1117 * 1118 * @param s a <code>String</code> value to be written. 1119 * @exception IOException if an I/O error occurs. 1120 * @see java.io.RandomAccessFile#writeChar(int) 1121 */ writeChars(String s)1122 public final void writeChars(String s) throws IOException { 1123 int clen = s.length(); 1124 int blen = 2*clen; 1125 byte[] b = new byte[blen]; 1126 char[] c = new char[clen]; 1127 s.getChars(0, clen, c, 0); 1128 for (int i = 0, j = 0; i < clen; i++) { 1129 b[j++] = (byte)(c[i] >>> 8); 1130 b[j++] = (byte)(c[i] >>> 0); 1131 } 1132 writeBytes(b, 0, blen); 1133 } 1134 1135 /** 1136 * Writes a string to the file using 1137 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a> 1138 * encoding in a machine-independent manner. 1139 * <p> 1140 * First, two bytes are written to the file, starting at the 1141 * current file pointer, as if by the 1142 * <code>writeShort</code> method giving the number of bytes to 1143 * follow. This value is the number of bytes actually written out, 1144 * not the length of the string. Following the length, each character 1145 * of the string is output, in sequence, using the modified UTF-8 encoding 1146 * for each character. 1147 * 1148 * @param str a string to be written. 1149 * @exception IOException if an I/O error occurs. 1150 */ writeUTF(String str)1151 public final void writeUTF(String str) throws IOException { 1152 DataOutputStream.writeUTF(str, this); 1153 } 1154 finalize()1155 @Override protected void finalize() throws Throwable { 1156 try { 1157 if (guard != null) { 1158 guard.warnIfOpen(); 1159 } 1160 close(); 1161 } finally { 1162 super.finalize(); 1163 } 1164 } 1165 } 1166