1 /*
2 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.io;
27
28 import java.nio.channels.FileChannel;
29 import sun.nio.ch.FileChannelImpl;
30
31
32 /**
33 * Instances of this class support both reading and writing to a
34 * random access file. A random access file behaves like a large
35 * array of bytes stored in the file system. There is a kind of cursor,
36 * or index into the implied array, called the <em>file pointer</em>;
37 * input operations read bytes starting at the file pointer and advance
38 * the file pointer past the bytes read. If the random access file is
39 * created in read/write mode, then output operations are also available;
40 * output operations write bytes starting at the file pointer and advance
41 * the file pointer past the bytes written. Output operations that write
42 * past the current end of the implied array cause the array to be
43 * extended. The file pointer can be read by the
44 * {@code getFilePointer} method and set by the {@code seek}
45 * method.
46 * <p>
47 * It is generally true of all the reading routines in this class that
48 * if end-of-file is reached before the desired number of bytes has been
49 * read, an {@code EOFException} (which is a kind of
50 * {@code IOException}) is thrown. If any byte cannot be read for
51 * any reason other than end-of-file, an {@code IOException} other
52 * than {@code EOFException} is thrown. In particular, an
53 * {@code IOException} may be thrown if the stream has been closed.
54 *
55 * @author unascribed
56 * @since JDK1.0
57 */
58
59 public class RandomAccessFile implements DataOutput, DataInput, Closeable {
60
61 private FileDescriptor fd;
62 private FileChannel channel = null;
63 private boolean rw;
64
65 /**
66 * The path of the referenced file
67 * (null if the stream is created with a file descriptor)
68 */
69 private final String path;
70
71 private Object closeLock = new Object();
72 private volatile boolean closed = false;
73
74 private static final int O_RDONLY = 1;
75 private static final int O_RDWR = 2;
76 private static final int O_SYNC = 4;
77 private static final int O_DSYNC = 8;
78
79 /**
80 * Creates a random access file stream to read from, and optionally
81 * to write to, a file with the specified name. A new
82 * {@link FileDescriptor} object is created to represent the
83 * connection to the file.
84 *
85 * <p> The <tt>mode</tt> argument specifies the access mode with which the
86 * file is to be opened. The permitted values and their meanings are as
87 * specified for the <a
88 * href="#mode"><tt>RandomAccessFile(File,String)</tt></a> constructor.
89 *
90 * <p>
91 * If there is a security manager, its {@code checkRead} method
92 * is called with the {@code name} argument
93 * as its argument to see if read access to the file is allowed.
94 * If the mode allows writing, the security manager's
95 * {@code checkWrite} method
96 * is also called with the {@code name} argument
97 * as its argument to see if write access to the file is allowed.
98 *
99 * @param name the system-dependent filename
100 * @param mode the access <a href="#mode">mode</a>
101 * @exception IllegalArgumentException if the mode argument is not equal
102 * to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
103 * <tt>"rwd"</tt>
104 * @exception FileNotFoundException
105 * if the mode is <tt>"r"</tt> but the given string does not
106 * denote an existing regular file, or if the mode begins with
107 * <tt>"rw"</tt> but the given string does not denote an
108 * existing, writable regular file and a new regular file of
109 * that name cannot be created, or if some other error occurs
110 * while opening or creating the file
111 * @exception SecurityException if a security manager exists and its
112 * {@code checkRead} method denies read access to the file
113 * or the mode is "rw" and the security manager's
114 * {@code checkWrite} method denies write access to the file
115 * @see java.lang.SecurityException
116 * @see java.lang.SecurityManager#checkRead(java.lang.String)
117 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
118 * @revised 1.4
119 * @spec JSR-51
120 */
121 public RandomAccessFile(String name, String mode)
122 throws FileNotFoundException
123 {
124 this(name != null ? new File(name) : null, mode);
125 }
126
127 /**
128 * Creates a random access file stream to read from, and optionally to
129 * write to, the file specified by the {@link File} argument. A new {@link
130 * FileDescriptor} object is created to represent this file connection.
131 *
132 * <p>The <a name="mode"><tt>mode</tt></a> argument specifies the access mode
133 * in which the file is to be opened. The permitted values and their
134 * meanings are:
135 *
136 * <table summary="Access mode permitted values and meanings">
137 * <tr><th align="left">Value</th><th align="left">Meaning</th></tr>
138 * <tr><td valign="top"><tt>"r"</tt></td>
139 * <td> Open for reading only. Invoking any of the <tt>write</tt>
140 * methods of the resulting object will cause an {@link
141 * java.io.IOException} to be thrown. </td></tr>
142 * <tr><td valign="top"><tt>"rw"</tt></td>
143 * <td> Open for reading and writing. If the file does not already
144 * exist then an attempt will be made to create it. </td></tr>
145 * <tr><td valign="top"><tt>"rws"</tt></td>
146 * <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
147 * require that every update to the file's content or metadata be
148 * written synchronously to the underlying storage device. </td></tr>
149 * <tr><td valign="top"><tt>"rwd" </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 be written
152 * synchronously to the underlying storage device. </td></tr>
153 * </table>
154 *
155 * The <tt>"rws"</tt> and <tt>"rwd"</tt> modes work much like the {@link
156 * java.nio.channels.FileChannel#force(boolean) force(boolean)} method of
157 * the {@link java.nio.channels.FileChannel} class, passing arguments of
158 * <tt>true</tt> and <tt>false</tt>, respectively, except that they always
159 * apply to every I/O operation and are therefore often more efficient. If
160 * the file resides on a local storage device then when an invocation of a
161 * method of this class returns it is guaranteed that all changes made to
162 * the file by that invocation will have been written to that device. This
163 * is useful for ensuring that critical information is not lost in the
164 * event of a system crash. If the file does not reside on a local device
165 * then no such guarantee is made.
166 *
167 * <p>The <tt>"rwd"</tt> mode can be used to reduce the number of I/O
168 * operations performed. Using <tt>"rwd"</tt> only requires updates to the
169 * file's content to be written to storage; using <tt>"rws"</tt> requires
170 * updates to both the file's content and its metadata to be written, which
171 * generally requires at least one more low-level I/O operation.
172 *
173 * <p>If there is a security manager, its {@code checkRead} method is
174 * called with the pathname of the {@code file} argument as its
175 * argument to see if read access to the file is allowed. If the mode
176 * allows writing, the security manager's {@code checkWrite} method is
177 * also called with the path argument to see if write access to the file is
178 * allowed.
179 *
180 * @param file the file object
181 * @param mode the access mode, as described
182 * <a href="#mode">above</a>
183 * @exception IllegalArgumentException if the mode argument is not equal
184 * to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
185 * <tt>"rwd"</tt>
186 * @exception FileNotFoundException
187 * if the mode is <tt>"r"</tt> but the given file object does
188 * not denote an existing regular file, or if the mode begins
189 * with <tt>"rw"</tt> but the given file object does not denote
190 * an existing, writable regular file and a new regular file of
191 * that name cannot be created, or if some other error occurs
192 * while opening or creating the file
193 * @exception SecurityException if a security manager exists and its
194 * {@code checkRead} method denies read access to the file
195 * or the mode is "rw" and the security manager's
196 * {@code checkWrite} method denies write access to the file
197 * @see java.lang.SecurityManager#checkRead(java.lang.String)
198 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
199 * @see java.nio.channels.FileChannel#force(boolean)
200 * @revised 1.4
201 * @spec JSR-51
202 */
203 public RandomAccessFile(File file, String mode)
204 throws FileNotFoundException
205 {
206 String name = (file != null ? file.getPath() : null);
207 int imode = -1;
208 if (mode.equals("r"))
209 imode = O_RDONLY;
210 else if (mode.startsWith("rw")) {
211 imode = O_RDWR;
212 rw = true;
213 if (mode.length() > 2) {
214 if (mode.equals("rws"))
215 imode |= O_SYNC;
216 else if (mode.equals("rwd"))
217 imode |= O_DSYNC;
218 else
219 imode = -1;
220 }
221 }
222 if (imode < 0)
223 throw new IllegalArgumentException("Illegal mode \"" + mode
224 + "\" must be one of "
225 + "\"r\", \"rw\", \"rws\","
226 + " or \"rwd\"");
227 SecurityManager security = System.getSecurityManager();
228 if (security != null) {
229 security.checkRead(name);
230 if (rw) {
231 security.checkWrite(name);
232 }
233 }
234 if (name == null) {
235 throw new NullPointerException();
236 }
237 if (file.isInvalid()) {
238 throw new FileNotFoundException("Invalid file path");
239 }
240 fd = new FileDescriptor();
241 fd.attach(this);
242 path = name;
243 open(name, imode);
244 }
245
246 /**
247 * Returns the opaque file descriptor object associated with this
248 * stream.
249 *
250 * @return the file descriptor object associated with this stream.
251 * @exception IOException if an I/O error occurs.
252 * @see java.io.FileDescriptor
253 */
254 public final FileDescriptor getFD() throws IOException {
255 if (fd != null) {
256 return fd;
257 }
258 throw new IOException();
259 }
260
261 /**
262 * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
263 * object associated with this file.
264 *
265 * <p> The {@link java.nio.channels.FileChannel#position()
266 * position} of the returned channel will always be equal to
267 * this object's file-pointer offset as returned by the {@link
268 * #getFilePointer getFilePointer} method. Changing this object's
269 * file-pointer offset, whether explicitly or by reading or writing bytes,
270 * will change the position of the channel, and vice versa. Changing the
271 * file's length via this object will change the length seen via the file
272 * channel, and vice versa.
273 *
274 * @return the file channel associated with this file
275 *
276 * @since 1.4
277 * @spec JSR-51
278 */
279 public final FileChannel getChannel() {
280 synchronized (this) {
281 if (channel == null) {
282 channel = FileChannelImpl.open(fd, path, true, rw, this);
283 }
284 return channel;
285 }
286 }
287
288 /**
289 * Opens a file and returns the file descriptor. The file is
290 * opened in read-write mode if the O_RDWR bit in {@code mode}
291 * is true, else the file is opened as read-only.
292 * If the {@code name} refers to a directory, an IOException
293 * is thrown.
294 *
295 * @param name the name of the file
296 * @param mode the mode flags, a combination of the O_ constants
297 * defined above
298 */
299 private native void open(String name, int mode)
300 throws FileNotFoundException;
301
302 // 'Read' primitives
303
304 /**
305 * Reads a byte of data from this file. The byte is returned as an
306 * integer in the range 0 to 255 ({@code 0x00-0x0ff}). This
307 * method blocks if no input is yet available.
308 * <p>
309 * Although {@code RandomAccessFile} is not a subclass of
310 * {@code InputStream}, this method behaves in exactly the same
311 * way as the {@link InputStream#read()} method of
312 * {@code InputStream}.
313 *
314 * @return the next byte of data, or {@code -1} if the end of the
315 * file has been reached.
316 * @exception IOException if an I/O error occurs. Not thrown if
317 * end-of-file has been reached.
318 */
319 public int read() throws IOException {
320 return read0();
321 }
322
323 private native int read0() throws IOException;
324
325 /**
326 * Reads a sub array as a sequence of bytes.
327 * @param b the buffer into which the data is read.
328 * @param off the start offset of the data.
329 * @param len the number of bytes to read.
330 * @exception IOException If an I/O error has occurred.
331 */
332 private native int readBytes(byte b[], int off, int len) throws IOException;
333
334 /**
335 * Reads up to {@code len} bytes of data from this file into an
336 * array of bytes. This method blocks until at least one byte of input
337 * is available.
338 * <p>
339 * Although {@code RandomAccessFile} is not a subclass of
340 * {@code InputStream}, this method behaves in exactly the
341 * same way as the {@link InputStream#read(byte[], int, int)} method of
342 * {@code InputStream}.
343 *
344 * @param b the buffer into which the data is read.
345 * @param off the start offset in array {@code b}
346 * at which the data is written.
347 * @param len the maximum number of bytes read.
348 * @return the total number of bytes read into the buffer, or
349 * {@code -1} if there is no more data because the end of
350 * the file has been reached.
351 * @exception IOException If the first byte cannot be read for any reason
352 * other than end of file, or if the random access file has been closed, or if
353 * some other I/O error occurs.
354 * @exception NullPointerException If {@code b} is {@code null}.
355 * @exception IndexOutOfBoundsException If {@code off} is negative,
356 * {@code len} is negative, or {@code len} is greater than
357 * {@code b.length - off}
358 */
359 public int read(byte b[], int off, int len) throws IOException {
360 return readBytes(b, off, len);
361 }
362
363 /**
364 * Reads up to {@code b.length} bytes of data from this file
365 * into an array of bytes. This method blocks until at least one byte
366 * of input is available.
367 * <p>
368 * Although {@code RandomAccessFile} is not a subclass of
369 * {@code InputStream}, this method behaves in exactly the
370 * same way as the {@link InputStream#read(byte[])} method of
371 * {@code InputStream}.
372 *
373 * @param b the buffer into which the data is read.
374 * @return the total number of bytes read into the buffer, or
375 * {@code -1} if there is no more data because the end of
376 * this file has been reached.
377 * @exception IOException If the first byte cannot be read for any reason
378 * other than end of file, or if the random access file has been closed, or if
379 * some other I/O error occurs.
380 * @exception NullPointerException If {@code b} is {@code null}.
381 */
382 public int read(byte b[]) throws IOException {
383 return readBytes(b, 0, b.length);
384 }
385
386 /**
387 * Reads {@code b.length} bytes from this file into the byte
388 * array, starting at the current file pointer. This method reads
389 * repeatedly from the file until the requested number of bytes are
390 * read. This method blocks until the requested number of bytes are
391 * read, the end of the stream is detected, or an exception is thrown.
392 *
393 * @param b the buffer into which the data is read.
394 * @exception EOFException if this file reaches the end before reading
395 * all the bytes.
396 * @exception IOException if an I/O error occurs.
397 */
398 public final void readFully(byte b[]) throws IOException {
399 readFully(b, 0, b.length);
400 }
401
402 /**
403 * Reads exactly {@code len} bytes from this file into the byte
404 * array, starting at the current file pointer. This method reads
405 * repeatedly from the file until the requested number of bytes are
406 * read. This method blocks until the requested number of bytes are
407 * read, the end of the stream is detected, or an exception is thrown.
408 *
409 * @param b the buffer into which the data is read.
410 * @param off the start offset of the data.
411 * @param len the number of bytes to read.
412 * @exception EOFException if this file reaches the end before reading
413 * all the bytes.
414 * @exception IOException if an I/O error occurs.
415 */
416 public final void readFully(byte b[], int off, int len) throws IOException {
417 int n = 0;
418 do {
419 int count = this.read(b, off + n, len - n);
420 if (count < 0)
421 throw new EOFException();
422 n += count;
423 } while (n < len);
424 }
425
426 /**
427 * Attempts to skip over {@code n} bytes of input discarding the
428 * skipped bytes.
429 * <p>
430 *
431 * This method may skip over some smaller number of bytes, possibly zero.
432 * This may result from any of a number of conditions; reaching end of
433 * file before {@code n} bytes have been skipped is only one
434 * possibility. This method never throws an {@code EOFException}.
435 * The actual number of bytes skipped is returned. If {@code n}
436 * is negative, no bytes are skipped.
437 *
438 * @param n the number of bytes to be skipped.
439 * @return the actual number of bytes skipped.
440 * @exception IOException if an I/O error occurs.
441 */
442 public int skipBytes(int n) throws IOException {
443 long pos;
444 long len;
445 long newpos;
446
447 if (n <= 0) {
448 return 0;
449 }
450 pos = getFilePointer();
451 len = length();
452 newpos = pos + n;
453 if (newpos > len) {
454 newpos = len;
455 }
456 seek(newpos);
457
458 /* return the actual number of bytes skipped */
459 return (int) (newpos - pos);
460 }
461
462 // 'Write' primitives
463
464 /**
465 * Writes the specified byte to this file. The write starts at
466 * the current file pointer.
467 *
468 * @param b the {@code byte} to be written.
469 * @exception IOException if an I/O error occurs.
470 */
471 public void write(int b) throws IOException {
472 write0(b);
473 }
474
475 private native void write0(int b) throws IOException;
476
477 /**
478 * Writes a sub array as a sequence of bytes.
479 * @param b the data to be written
480
481 * @param off the start offset in the data
482 * @param len the number of bytes that are written
483 * @exception IOException If an I/O error has occurred.
484 */
485 private native void writeBytes(byte b[], int off, int len) throws IOException;
486
487 /**
488 * Writes {@code b.length} bytes from the specified byte array
489 * to this file, starting at the current file pointer.
490 *
491 * @param b the data.
492 * @exception IOException if an I/O error occurs.
493 */
494 public void write(byte b[]) throws IOException {
495 writeBytes(b, 0, b.length);
496 }
497
498 /**
499 * Writes {@code len} bytes from the specified byte array
500 * starting at offset {@code off} to this file.
501 *
502 * @param b the data.
503 * @param off the start offset in the data.
504 * @param len the number of bytes to write.
505 * @exception IOException if an I/O error occurs.
506 */
507 public void write(byte b[], int off, int len) throws IOException {
508 writeBytes(b, off, len);
509 }
510
511 // 'Random access' stuff
512
513 /**
514 * Returns the current offset in this file.
515 *
516 * @return the offset from the beginning of the file, in bytes,
517 * at which the next read or write occurs.
518 * @exception IOException if an I/O error occurs.
519 */
520 public native long getFilePointer() throws IOException;
521
522 /**
523 * Sets the file-pointer offset, measured from the beginning of this
524 * file, at which the next read or write occurs. The offset may be
525 * set beyond the end of the file. Setting the offset beyond the end
526 * of the file does not change the file length. The file length will
527 * change only by writing after the offset has been set beyond the end
528 * of the file.
529 *
530 * @param pos the offset position, measured in bytes from the
531 * beginning of the file, at which to set the file
532 * pointer.
533 * @exception IOException if {@code pos} is less than
534 * {@code 0} or if an I/O error occurs.
535 */
536 public void seek(long pos) throws IOException {
537 if (pos < 0) {
538 throw new IOException("Negative seek offset");
539 } else {
540 seek0(pos);
541 }
542 }
543
544 private native void seek0(long pos) throws IOException;
545
546 /**
547 * Returns the length of this file.
548 *
549 * @return the length of this file, measured in bytes.
550 * @exception IOException if an I/O error occurs.
551 */
552 public native long length() throws IOException;
553
554 /**
555 * Sets the length of this file.
556 *
557 * <p> If the present length of the file as returned by the
558 * {@code length} method is greater than the {@code newLength}
559 * argument then the file will be truncated. In this case, if the file
560 * offset as returned by the {@code getFilePointer} method is greater
561 * than {@code newLength} then after this method returns the offset
562 * will be equal to {@code newLength}.
563 *
564 * <p> If the present length of the file as returned by the
565 * {@code length} method is smaller than the {@code newLength}
566 * argument then the file will be extended. In this case, the contents of
567 * the extended portion of the file are not defined.
568 *
569 * @param newLength The desired length of the file
570 * @exception IOException If an I/O error occurs
571 * @since 1.2
572 */
573 public native void setLength(long newLength) throws IOException;
574
575 /**
576 * Closes this random access file stream and releases any system
577 * resources associated with the stream. A closed random access
578 * file cannot perform input or output operations and cannot be
579 * reopened.
580 *
581 * <p> If this file has an associated channel then the channel is closed
582 * as well.
583 *
584 * @exception IOException if an I/O error occurs.
585 *
586 * @revised 1.4
587 * @spec JSR-51
588 */
589 public void close() throws IOException {
590 synchronized (closeLock) {
591 if (closed) {
592 return;
593 }
594 closed = true;
595 }
596 if (channel != null) {
597 channel.close();
598 }
599
600 fd.closeAll(new Closeable() {
601 public void close() throws IOException {
602 close0();
603 }
604 });
605 }
606
607 //
608 // Some "reading/writing Java data types" methods stolen from
609 // DataInputStream and DataOutputStream.
610 //
611
612 /**
613 * Reads a {@code boolean} from this file. This method reads a
614 * single byte from the file, starting at the current file pointer.
615 * A value of {@code 0} represents
616 * {@code false}. Any other value represents {@code true}.
617 * This method blocks until the byte is read, the end of the stream
618 * is detected, or an exception is thrown.
619 *
620 * @return the {@code boolean} value read.
621 * @exception EOFException if this file has reached the end.
622 * @exception IOException if an I/O error occurs.
623 */
624 public final boolean readBoolean() throws IOException {
625 int ch = this.read();
626 if (ch < 0)
627 throw new EOFException();
628 return (ch != 0);
629 }
630
631 /**
632 * Reads a signed eight-bit value from this file. This method reads a
633 * byte from the file, starting from the current file pointer.
634 * If the byte read is {@code b}, where
635 * <code>0 <= b <= 255</code>,
636 * then the result is:
637 * <blockquote><pre>
638 * (byte)(b)
639 * </pre></blockquote>
640 * <p>
641 * This method blocks until the byte is read, the end of the stream
642 * is detected, or an exception is thrown.
643 *
644 * @return the next byte of this file as a signed eight-bit
645 * {@code byte}.
646 * @exception EOFException if this file has reached the end.
647 * @exception IOException if an I/O error occurs.
648 */
649 public final byte readByte() throws IOException {
650 int ch = this.read();
651 if (ch < 0)
652 throw new EOFException();
653 return (byte)(ch);
654 }
655
656 /**
657 * Reads an unsigned eight-bit number from this file. This method reads
658 * a byte from this file, starting at the current file pointer,
659 * and returns that byte.
660 * <p>
661 * This method blocks until the byte is read, the end of the stream
662 * is detected, or an exception is thrown.
663 *
664 * @return the next byte of this file, interpreted as an unsigned
665 * eight-bit number.
666 * @exception EOFException if this file has reached the end.
667 * @exception IOException if an I/O error occurs.
668 */
669 public final int readUnsignedByte() throws IOException {
670 int ch = this.read();
671 if (ch < 0)
672 throw new EOFException();
673 return ch;
674 }
675
676 /**
677 * Reads a signed 16-bit number from this file. The method reads two
678 * bytes from this file, starting at the current file pointer.
679 * If the two bytes read, in order, are
680 * {@code b1} and {@code b2}, where each of the two values is
681 * between {@code 0} and {@code 255}, inclusive, then the
682 * result is equal to:
683 * <blockquote><pre>
684 * (short)((b1 << 8) | b2)
685 * </pre></blockquote>
686 * <p>
687 * This method blocks until the two bytes are read, the end of the
688 * stream is detected, or an exception is thrown.
689 *
690 * @return the next two bytes of this file, interpreted as a signed
691 * 16-bit number.
692 * @exception EOFException if this file reaches the end before reading
693 * two bytes.
694 * @exception IOException if an I/O error occurs.
695 */
696 public final short readShort() throws IOException {
697 int ch1 = this.read();
698 int ch2 = this.read();
699 if ((ch1 | ch2) < 0)
700 throw new EOFException();
701 return (short)((ch1 << 8) + (ch2 << 0));
702 }
703
704 /**
705 * Reads an unsigned 16-bit number from this file. This method reads
706 * two bytes from the file, starting at the current file pointer.
707 * If the bytes read, in order, are
708 * {@code b1} and {@code b2}, where
709 * <code>0 <= b1, b2 <= 255</code>,
710 * then the result is equal to:
711 * <blockquote><pre>
712 * (b1 << 8) | b2
713 * </pre></blockquote>
714 * <p>
715 * This method blocks until the two bytes are read, the end of the
716 * stream is detected, or an exception is thrown.
717 *
718 * @return the next two bytes of this file, interpreted as an unsigned
719 * 16-bit integer.
720 * @exception EOFException if this file reaches the end before reading
721 * two bytes.
722 * @exception IOException if an I/O error occurs.
723 */
724 public final int readUnsignedShort() throws IOException {
725 int ch1 = this.read();
726 int ch2 = this.read();
727 if ((ch1 | ch2) < 0)
728 throw new EOFException();
729 return (ch1 << 8) + (ch2 << 0);
730 }
731
732 /**
733 * Reads a character from this file. This method reads two
734 * bytes from the file, starting at the current file pointer.
735 * If the bytes read, in order, are
736 * {@code b1} and {@code b2}, where
737 * <code>0 <= b1, b2 <= 255</code>,
738 * then the result is equal to:
739 * <blockquote><pre>
740 * (char)((b1 << 8) | b2)
741 * </pre></blockquote>
742 * <p>
743 * This method blocks until the two bytes are read, the end of the
744 * stream is detected, or an exception is thrown.
745 *
746 * @return the next two bytes of this file, interpreted as a
747 * {@code char}.
748 * @exception EOFException if this file reaches the end before reading
749 * two bytes.
750 * @exception IOException if an I/O error occurs.
751 */
752 public final char readChar() throws IOException {
753 int ch1 = this.read();
754 int ch2 = this.read();
755 if ((ch1 | ch2) < 0)
756 throw new EOFException();
757 return (char)((ch1 << 8) + (ch2 << 0));
758 }
759
760 /**
761 * Reads a signed 32-bit integer from this file. This method reads 4
762 * bytes from the file, starting at the current file pointer.
763 * If the bytes read, in order, are {@code b1},
764 * {@code b2}, {@code b3}, and {@code b4}, where
765 * <code>0 <= b1, b2, b3, b4 <= 255</code>,
766 * then the result is equal to:
767 * <blockquote><pre>
768 * (b1 << 24) | (b2 << 16) + (b3 << 8) + b4
769 * </pre></blockquote>
770 * <p>
771 * This method blocks until the four bytes are read, the end of the
772 * stream is detected, or an exception is thrown.
773 *
774 * @return the next four bytes of this file, interpreted as an
775 * {@code int}.
776 * @exception EOFException if this file reaches the end before reading
777 * four bytes.
778 * @exception IOException if an I/O error occurs.
779 */
780 public final int readInt() throws IOException {
781 int ch1 = this.read();
782 int ch2 = this.read();
783 int ch3 = this.read();
784 int ch4 = this.read();
785 if ((ch1 | ch2 | ch3 | ch4) < 0)
786 throw new EOFException();
787 return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
788 }
789
790 /**
791 * Reads a signed 64-bit integer from this file. This method reads eight
792 * bytes from the file, starting at the current file pointer.
793 * If the bytes read, in order, are
794 * {@code b1}, {@code b2}, {@code b3},
795 * {@code b4}, {@code b5}, {@code b6},
796 * {@code b7}, and {@code b8,} where:
797 * <blockquote><pre>
798 * 0 <= b1, b2, b3, b4, b5, b6, b7, b8 <=255,
799 * </pre></blockquote>
800 * <p>
801 * then the result is equal to:
802 * <blockquote><pre>
803 * ((long)b1 << 56) + ((long)b2 << 48)
804 * + ((long)b3 << 40) + ((long)b4 << 32)
805 * + ((long)b5 << 24) + ((long)b6 << 16)
806 * + ((long)b7 << 8) + b8
807 * </pre></blockquote>
808 * <p>
809 * This method blocks until the eight bytes are read, the end of the
810 * stream is detected, or an exception is thrown.
811 *
812 * @return the next eight bytes of this file, interpreted as a
813 * {@code long}.
814 * @exception EOFException if this file reaches the end before reading
815 * eight bytes.
816 * @exception IOException if an I/O error occurs.
817 */
818 public final long readLong() throws IOException {
819 return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
820 }
821
822 /**
823 * Reads a {@code float} from this file. This method reads an
824 * {@code int} value, starting at the current file pointer,
825 * as if by the {@code readInt} method
826 * and then converts that {@code int} to a {@code float}
827 * using the {@code intBitsToFloat} method in class
828 * {@code Float}.
829 * <p>
830 * This method blocks until the four bytes are read, the end of the
831 * stream is detected, or an exception is thrown.
832 *
833 * @return the next four bytes of this file, interpreted as a
834 * {@code float}.
835 * @exception EOFException if this file reaches the end before reading
836 * four bytes.
837 * @exception IOException if an I/O error occurs.
838 * @see java.io.RandomAccessFile#readInt()
839 * @see java.lang.Float#intBitsToFloat(int)
840 */
841 public final float readFloat() throws IOException {
842 return Float.intBitsToFloat(readInt());
843 }
844
845 /**
846 * Reads a {@code double} from this file. This method reads a
847 * {@code long} value, starting at the current file pointer,
848 * as if by the {@code readLong} method
849 * and then converts that {@code long} to a {@code double}
850 * using the {@code longBitsToDouble} method in
851 * class {@code Double}.
852 * <p>
853 * This method blocks until the eight bytes are read, the end of the
854 * stream is detected, or an exception is thrown.
855 *
856 * @return the next eight bytes of this file, interpreted as a
857 * {@code double}.
858 * @exception EOFException if this file reaches the end before reading
859 * eight bytes.
860 * @exception IOException if an I/O error occurs.
861 * @see java.io.RandomAccessFile#readLong()
862 * @see java.lang.Double#longBitsToDouble(long)
863 */
864 public final double readDouble() throws IOException {
865 return Double.longBitsToDouble(readLong());
866 }
867
868 /**
869 * Reads the next line of text from this file. This method successively
870 * reads bytes from the file, starting at the current file pointer,
871 * until it reaches a line terminator or the end
872 * of the file. Each byte is converted into a character by taking the
873 * byte's value for the lower eight bits of the character and setting the
874 * high eight bits of the character to zero. This method does not,
875 * therefore, support the full Unicode character set.
876 *
877 * <p> A line of text is terminated by a carriage-return character
878 * ({@code '\u005Cr'}), a newline character ({@code '\u005Cn'}), a
879 * carriage-return character immediately followed by a newline character,
880 * or the end of the file. Line-terminating characters are discarded and
881 * are not included as part of the string returned.
882 *
883 * <p> This method blocks until a newline character is read, a carriage
884 * return and the byte following it are read (to see if it is a newline),
885 * the end of the file is reached, or an exception is thrown.
886 *
887 * @return the next line of text from this file, or null if end
888 * of file is encountered before even one byte is read.
889 * @exception IOException if an I/O error occurs.
890 */
891
892 public final String readLine() throws IOException {
893 StringBuffer input = new StringBuffer();
894 int c = -1;
895 boolean eol = false;
896
897 while (!eol) {
898 switch (c = read()) {
899 case -1:
900 case '\n':
901 eol = true;
902 break;
903 case '\r':
904 eol = true;
905 long cur = getFilePointer();
906 if ((read()) != '\n') {
907 seek(cur);
908 }
909 break;
910 default:
911 input.append((char)c);
912 break;
913 }
914 }
915
916 if ((c == -1) && (input.length() == 0)) {
917 return null;
918 }
919 return input.toString();
920 }
921
922 /**
923 * Reads in a string from this file. The string has been encoded
924 * using a
925 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
926 * format.
927 * <p>
928 * The first two bytes are read, starting from the current file
929 * pointer, as if by
930 * {@code readUnsignedShort}. This value gives the number of
931 * following bytes that are in the encoded string, not
932 * the length of the resulting string. The following bytes are then
933 * interpreted as bytes encoding characters in the modified UTF-8 format
934 * and are converted into characters.
935 * <p>
936 * This method blocks until all the bytes are read, the end of the
937 * stream is detected, or an exception is thrown.
938 *
939 * @return a Unicode string.
940 * @exception EOFException if this file reaches the end before
941 * reading all the bytes.
942 * @exception IOException if an I/O error occurs.
943 * @exception UTFDataFormatException if the bytes do not represent
944 * valid modified UTF-8 encoding of a Unicode string.
945 * @see java.io.RandomAccessFile#readUnsignedShort()
946 */
947 public final String readUTF() throws IOException {
948 return DataInputStream.readUTF(this);
949 }
950
951 /**
952 * Writes a {@code boolean} to the file as a one-byte value. The
953 * value {@code true} is written out as the value
954 * {@code (byte)1}; the value {@code false} is written out
955 * as the value {@code (byte)0}. The write starts at
956 * the current position of the file pointer.
957 *
958 * @param v a {@code boolean} value to be written.
959 * @exception IOException if an I/O error occurs.
960 */
961 public final void writeBoolean(boolean v) throws IOException {
962 write(v ? 1 : 0);
963 //written++;
964 }
965
966 /**
967 * Writes a {@code byte} to the file as a one-byte value. The
968 * write starts at the current position of the file pointer.
969 *
970 * @param v a {@code byte} value to be written.
971 * @exception IOException if an I/O error occurs.
972 */
973 public final void writeByte(int v) throws IOException {
974 write(v);
975 //written++;
976 }
977
978 /**
979 * Writes a {@code short} to the file as two bytes, high byte first.
980 * The write starts at the current position of the file pointer.
981 *
982 * @param v a {@code short} to be written.
983 * @exception IOException if an I/O error occurs.
984 */
985 public final void writeShort(int v) throws IOException {
986 write((v >>> 8) & 0xFF);
987 write((v >>> 0) & 0xFF);
988 //written += 2;
989 }
990
991 /**
992 * Writes a {@code char} to the file as a two-byte value, high
993 * byte first. The write starts at the current position of the
994 * file pointer.
995 *
996 * @param v a {@code char} value to be written.
997 * @exception IOException if an I/O error occurs.
998 */
999 public final void writeChar(int v) throws IOException {
1000 write((v >>> 8) & 0xFF);
1001 write((v >>> 0) & 0xFF);
1002 //written += 2;
1003 }
1004
1005 /**
1006 * Writes an {@code int} to the file as four bytes, high byte first.
1007 * The write starts at the current position of the file pointer.
1008 *
1009 * @param v an {@code int} to be written.
1010 * @exception IOException if an I/O error occurs.
1011 */
1012 public final void writeInt(int v) throws IOException {
1013 write((v >>> 24) & 0xFF);
1014 write((v >>> 16) & 0xFF);
1015 write((v >>> 8) & 0xFF);
1016 write((v >>> 0) & 0xFF);
1017 //written += 4;
1018 }
1019
1020 /**
1021 * Writes a {@code long} to the file as eight bytes, high byte first.
1022 * The write starts at the current position of the file pointer.
1023 *
1024 * @param v a {@code long} to be written.
1025 * @exception IOException if an I/O error occurs.
1026 */
1027 public final void writeLong(long v) throws IOException {
1028 write((int)(v >>> 56) & 0xFF);
1029 write((int)(v >>> 48) & 0xFF);
1030 write((int)(v >>> 40) & 0xFF);
1031 write((int)(v >>> 32) & 0xFF);
1032 write((int)(v >>> 24) & 0xFF);
1033 write((int)(v >>> 16) & 0xFF);
1034 write((int)(v >>> 8) & 0xFF);
1035 write((int)(v >>> 0) & 0xFF);
1036 //written += 8;
1037 }
1038
1039 /**
1040 * Converts the float argument to an {@code int} using the
1041 * {@code floatToIntBits} method in class {@code Float},
1042 * and then writes that {@code int} value to the file as a
1043 * four-byte quantity, high byte first. The write starts at the
1044 * current position of the file pointer.
1045 *
1046 * @param v a {@code float} value to be written.
1047 * @exception IOException if an I/O error occurs.
1048 * @see java.lang.Float#floatToIntBits(float)
1049 */
1050 public final void writeFloat(float v) throws IOException {
1051 writeInt(Float.floatToIntBits(v));
1052 }
1053
1054 /**
1055 * Converts the double argument to a {@code long} using the
1056 * {@code doubleToLongBits} method in class {@code Double},
1057 * and then writes that {@code long} value to the file as an
1058 * eight-byte quantity, high byte first. The write starts at the current
1059 * position of the file pointer.
1060 *
1061 * @param v a {@code double} value to be written.
1062 * @exception IOException if an I/O error occurs.
1063 * @see java.lang.Double#doubleToLongBits(double)
1064 */
1065 public final void writeDouble(double v) throws IOException {
1066 writeLong(Double.doubleToLongBits(v));
1067 }
1068
1069 /**
1070 * Writes the string to the file as a sequence of bytes. Each
1071 * character in the string is written out, in sequence, by discarding
1072 * its high eight bits. The write starts at the current position of
1073 * the file pointer.
1074 *
1075 * @param s a string of bytes to be written.
1076 * @exception IOException if an I/O error occurs.
1077 */
1078 @SuppressWarnings("deprecation")
1079 public final void writeBytes(String s) throws IOException {
1080 int len = s.length();
1081 byte[] b = new byte[len];
1082 s.getBytes(0, len, b, 0);
1083 writeBytes(b, 0, len);
1084 }
1085
1086 /**
1087 * Writes a string to the file as a sequence of characters. Each
1088 * character is written to the data output stream as if by the
1089 * {@code writeChar} method. The write starts at the current
1090 * position of the file pointer.
1091 *
1092 * @param s a {@code String} value to be written.
1093 * @exception IOException if an I/O error occurs.
1094 * @see java.io.RandomAccessFile#writeChar(int)
1095 */
1096 public final void writeChars(String s) throws IOException {
1097 int clen = s.length();
1098 int blen = 2*clen;
1099 byte[] b = new byte[blen];
1100 char[] c = new char[clen];
1101 s.getChars(0, clen, c, 0);
1102 for (int i = 0, j = 0; i < clen; i++) {
1103 b[j++] = (byte)(c[i] >>> 8);
1104 b[j++] = (byte)(c[i] >>> 0);
1105 }
1106 writeBytes(b, 0, blen);
1107 }
1108
1109 /**
1110 * Writes a string to the file using
1111 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
1112 * encoding in a machine-independent manner.
1113 * <p>
1114 * First, two bytes are written to the file, starting at the
1115 * current file pointer, as if by the
1116 * {@code writeShort} method giving the number of bytes to
1117 * follow. This value is the number of bytes actually written out,
1118 * not the length of the string. Following the length, each character
1119 * of the string is output, in sequence, using the modified UTF-8 encoding
1120 * for each character.
1121 *
1122 * @param str a string to be written.
1123 * @exception IOException if an I/O error occurs.
1124 */
1125 public final void writeUTF(String str) throws IOException {
1126 DataOutputStream.writeUTF(str, this);
1127 }
1128
1129 private static native void initIDs();
1130
1131 private native void close0() throws IOException;
1132
1133 static {
1134 initIDs();
1135 }
1136 }