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 import sun.misc.IoTrace;
31 import sun.misc.IoTraceContext;
32
33
34 /**
35 * Instances of this class support both reading and writing to a
36 * random access file. A random access file behaves like a large
37 * array of bytes stored in the file system. There is a kind of cursor,
38 * or index into the implied array, called the <em>file pointer</em>;
39 * input operations read bytes starting at the file pointer and advance
40 * the file pointer past the bytes read. If the random access file is
41 * created in read/write mode, then output operations are also available;
42 * output operations write bytes starting at the file pointer and advance
43 * the file pointer past the bytes written. Output operations that write
44 * past the current end of the implied array cause the array to be
45 * extended. The file pointer can be read by the
46 * {@code getFilePointer} method and set by the {@code seek}
47 * method.
48 * <p>
49 * It is generally true of all the reading routines in this class that
50 * if end-of-file is reached before the desired number of bytes has been
51 * read, an {@code EOFException} (which is a kind of
52 * {@code IOException}) is thrown. If any byte cannot be read for
53 * any reason other than end-of-file, an {@code IOException} other
54 * than {@code EOFException} is thrown. In particular, an
55 * {@code IOException} may be thrown if the stream has been closed.
56 *
57 * @author unascribed
58 * @since JDK1.0
59 */
60
61 public class RandomAccessFile implements DataOutput, DataInput, Closeable {
62
63 private FileDescriptor fd;
64 private FileChannel channel = null;
65 private boolean rw;
66 private final String path;
67
68 private Object closeLock = new Object();
69 private volatile boolean closed = false;
70
71 private static final int O_RDONLY = 1;
72 private static final int O_RDWR = 2;
73 private static final int O_SYNC = 4;
74 private static final int O_DSYNC = 8;
75
76 /**
77 * Creates a random access file stream to read from, and optionally
78 * to write to, a file with the specified name. A new
79 * {@link FileDescriptor} object is created to represent the
80 * connection to the file.
81 *
82 * <p> The <tt>mode</tt> argument specifies the access mode with which the
83 * file is to be opened. The permitted values and their meanings are as
84 * specified for the <a
85 * href="#mode"><tt>RandomAccessFile(File,String)</tt></a> constructor.
86 *
87 * <p>
88 * If there is a security manager, its {@code checkRead} method
89 * is called with the {@code name} argument
90 * as its argument to see if read access to the file is allowed.
91 * If the mode allows writing, the security manager's
92 * {@code checkWrite} method
93 * is also called with the {@code name} argument
94 * as its argument to see if write access to the file is allowed.
95 *
96 * @param name the system-dependent filename
97 * @param mode the access <a href="#mode">mode</a>
98 * @exception IllegalArgumentException if the mode argument is not equal
99 * to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
100 * <tt>"rwd"</tt>
101 * @exception FileNotFoundException
102 * if the mode is <tt>"r"</tt> but the given string does not
103 * denote an existing regular file, or if the mode begins with
104 * <tt>"rw"</tt> but the given string does not denote an
105 * existing, writable regular file and a new regular file of
106 * that name cannot be created, or if some other error occurs
107 * while opening or creating the file
108 * @exception SecurityException if a security manager exists and its
109 * {@code checkRead} method denies read access to the file
110 * or the mode is "rw" and the security manager's
111 * {@code checkWrite} method denies write access to the file
112 * @see java.lang.SecurityException
113 * @see java.lang.SecurityManager#checkRead(java.lang.String)
114 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
115 * @revised 1.4
116 * @spec JSR-51
117 */
118 public RandomAccessFile(String name, String mode)
119 throws FileNotFoundException
120 {
121 this(name != null ? new File(name) : null, mode);
122 }
123
124 /**
125 * Creates a random access file stream to read from, and optionally to
126 * write to, the file specified by the {@link File} argument. A new {@link
127 * FileDescriptor} object is created to represent this file connection.
128 *
129 * <a name="mode"><p> The <tt>mode</tt> argument specifies the access mode
130 * in which the file is to be opened. The permitted values and their
131 * meanings are:
132 *
133 * <blockquote><table summary="Access mode permitted values and meanings">
134 * <tr><th><p align="left">Value</p></th><th><p align="left">Meaning</p></th></tr>
135 * <tr><td valign="top"><tt>"r"</tt></td>
136 * <td> Open for reading only. Invoking any of the <tt>write</tt>
137 * methods of the resulting object will cause an {@link
138 * java.io.IOException} to be thrown. </td></tr>
139 * <tr><td valign="top"><tt>"rw"</tt></td>
140 * <td> Open for reading and writing. If the file does not already
141 * exist then an attempt will be made to create it. </td></tr>
142 * <tr><td valign="top"><tt>"rws"</tt></td>
143 * <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
144 * require that every update to the file's content or metadata be
145 * written synchronously to the underlying storage device. </td></tr>
146 * <tr><td valign="top"><tt>"rwd" </tt></td>
147 * <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
148 * require that every update to the file's content be written
149 * synchronously to the underlying storage device. </td></tr>
150 * </table></blockquote>
151 *
152 * The <tt>"rws"</tt> and <tt>"rwd"</tt> modes work much like the {@link
153 * java.nio.channels.FileChannel#force(boolean) force(boolean)} method of
154 * the {@link java.nio.channels.FileChannel} class, passing arguments of
155 * <tt>true</tt> and <tt>false</tt>, respectively, except that they always
156 * apply to every I/O operation and are therefore often more efficient. If
157 * the file resides on a local storage device then when an invocation of a
158 * method of this class returns it is guaranteed that all changes made to
159 * the file by that invocation will have been written to that device. This
160 * is useful for ensuring that critical information is not lost in the
161 * event of a system crash. If the file does not reside on a local device
162 * then no such guarantee is made.
163 *
164 * <p> The <tt>"rwd"</tt> mode can be used to reduce the number of I/O
165 * operations performed. Using <tt>"rwd"</tt> only requires updates to the
166 * file's content to be written to storage; using <tt>"rws"</tt> requires
167 * updates to both the file's content and its metadata to be written, which
168 * generally requires at least one more low-level I/O operation.
169 *
170 * <p> If there is a security manager, its {@code checkRead} method is
171 * called with the pathname of the {@code file} argument as its
172 * argument to see if read access to the file is allowed. If the mode
173 * allows writing, the security manager's {@code checkWrite} method is
174 * also called with the path argument to see if write access to the file is
175 * allowed.
176 *
177 * @param file the file object
178 * @param mode the access mode, as described
179 * <a href="#mode">above</a>
180 * @exception IllegalArgumentException if the mode argument is not equal
181 * to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
182 * <tt>"rwd"</tt>
183 * @exception FileNotFoundException
184 * if the mode is <tt>"r"</tt> but the given file object does
185 * not denote an existing regular file, or if the mode begins
186 * with <tt>"rw"</tt> but the given file object does not denote
187 * an existing, writable regular file and a new regular file of
188 * that name cannot be created, or if some other error occurs
189 * while opening or creating the file
190 * @exception SecurityException if a security manager exists and its
191 * {@code checkRead} method denies read access to the file
192 * or the mode is "rw" and the security manager's
193 * {@code checkWrite} method denies write access to the file
194 * @see java.lang.SecurityManager#checkRead(java.lang.String)
195 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
196 * @see java.nio.channels.FileChannel#force(boolean)
197 * @revised 1.4
198 * @spec JSR-51
199 */
200 public RandomAccessFile(File file, String mode)
201 throws FileNotFoundException
202 {
203 String name = (file != null ? file.getPath() : null);
204 int imode = -1;
205 if (mode.equals("r"))
206 imode = O_RDONLY;
207 else if (mode.startsWith("rw")) {
208 imode = O_RDWR;
209 rw = true;
210 if (mode.length() > 2) {
211 if (mode.equals("rws"))
212 imode |= O_SYNC;
213 else if (mode.equals("rwd"))
214 imode |= O_DSYNC;
215 else
216 imode = -1;
217 }
218 }
219 if (imode < 0)
220 throw new IllegalArgumentException("Illegal mode \"" + mode
221 + "\" must be one of "
222 + "\"r\", \"rw\", \"rws\","
223 + " or \"rwd\"");
224 SecurityManager security = System.getSecurityManager();
225 if (security != null) {
226 security.checkRead(name);
227 if (rw) {
228 security.checkWrite(name);
229 }
230 }
231 if (name == null) {
232 throw new NullPointerException();
233 }
234 fd = new FileDescriptor();
235 fd.attach(this);
236 this.path = name;
237 open(name, imode);
238 }
239
240 /**
241 * Returns the opaque file descriptor object associated with this
242 * stream. </p>
243 *
244 * @return the file descriptor object associated with this stream.
245 * @exception IOException if an I/O error occurs.
246 * @see java.io.FileDescriptor
247 */
248 public final FileDescriptor getFD() throws IOException {
249 if (fd != null) {
250 return fd;
251 }
252 throw new IOException();
253 }
254
255 /**
256 * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
257 * object associated with this file.
258 *
259 * <p> The {@link java.nio.channels.FileChannel#position()
260 * position} of the returned channel will always be equal to
261 * this object's file-pointer offset as returned by the {@link
262 * #getFilePointer getFilePointer} method. Changing this object's
263 * file-pointer offset, whether explicitly or by reading or writing bytes,
264 * will change the position of the channel, and vice versa. Changing the
265 * file's length via this object will change the length seen via the file
266 * channel, and vice versa.
267 *
268 * @return the file channel associated with this file
269 *
270 * @since 1.4
271 * @spec JSR-51
272 */
273 public final FileChannel getChannel() {
274 synchronized (this) {
275 if (channel == null) {
276 channel = FileChannelImpl.open(fd, path, true, rw, this);
277 }
278 return channel;
279 }
280 }
281
282 /**
283 * Opens a file and returns the file descriptor. The file is
284 * opened in read-write mode if the O_RDWR bit in {@code mode}
285 * is true, else the file is opened as read-only.
286 * If the {@code name} refers to a directory, an IOException
287 * is thrown.
288 *
289 * @param name the name of the file
290 * @param mode the mode flags, a combination of the O_ constants
291 * defined above
292 */
293 private native void open(String name, int mode)
294 throws FileNotFoundException;
295
296 // 'Read' primitives
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}). This
301 * method blocks if no input is yet available.
302 * <p>
303 * Although {@code RandomAccessFile} is not a subclass of
304 * {@code InputStream}, this method behaves in exactly the same
305 * way as the {@link InputStream#read()} method of
306 * {@code InputStream}.
307 *
308 * @return the next byte of data, or {@code -1} 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 */
313 public int read() throws IOException {
314 IoTraceContext traceContext = IoTrace.fileReadBegin(path);
315 int v = 0;
316 try {
317 v = read0();
318 } finally {
319 IoTrace.fileReadEnd(traceContext, v == -1 ? 0 : 1);
320 }
321 return v;
322 }
323
324 private native int read0() throws IOException;
325
326 /**
327 * Reads a sub array as a sequence of bytes.
328 * @param b the buffer into which the data is read.
329 * @param off the start offset of the data.
330 * @param len the number of bytes to read.
331 * @exception IOException If an I/O error has occurred.
332 */
333 private int readBytes(byte b[], int off, int len) throws IOException {
334 IoTraceContext traceContext = IoTrace.fileReadBegin(path);
335 int v = 0;
336 try {
337 v = readBytes0(b, off, len);
338 } finally {
339 IoTrace.fileReadEnd(traceContext, v);
340 }
341 return v;
342 }
343
344 private native int readBytes0(byte b[], int off, int len) throws IOException;
345
346 /**
347 * Reads up to {@code len} bytes of data from this file into an
348 * array of bytes. This method blocks until at least one byte of input
349 * is available.
350 * <p>
351 * Although {@code RandomAccessFile} is not a subclass of
352 * {@code InputStream}, this method behaves in exactly the
353 * same way as the {@link InputStream#read(byte[], int, int)} method of
354 * {@code InputStream}.
355 *
356 * @param b the buffer into which the data is read.
357 * @param off the start offset in array {@code b}
358 * at which the data is written.
359 * @param len the maximum number of bytes read.
360 * @return the total number of bytes read into the buffer, or
361 * {@code -1} if there is no more data because the end of
362 * the file has been reached.
363 * @exception IOException If the first byte cannot be read for any reason
364 * other than end of file, or if the random access file has been closed, or if
365 * some other I/O error occurs.
366 * @exception NullPointerException If {@code b} is {@code null}.
367 * @exception IndexOutOfBoundsException If {@code off} is negative,
368 * {@code len} is negative, or {@code len} is greater than
369 * {@code b.length - off}
370 */
371 public int read(byte b[], int off, int len) throws IOException {
372 return readBytes(b, off, len);
373 }
374
375 /**
376 * Reads up to {@code b.length} bytes of data from this file
377 * into an array of bytes. This method blocks until at least one byte
378 * of input is available.
379 * <p>
380 * Although {@code RandomAccessFile} is not a subclass of
381 * {@code InputStream}, this method behaves in exactly the
382 * same way as the {@link InputStream#read(byte[])} method of
383 * {@code InputStream}.
384 *
385 * @param b the buffer into which the data is read.
386 * @return the total number of bytes read into the buffer, or
387 * {@code -1} if there is no more data because the end of
388 * this file has been reached.
389 * @exception IOException If the first byte cannot be read for any reason
390 * other than end of file, or if the random access file has been closed, or if
391 * some other I/O error occurs.
392 * @exception NullPointerException If {@code b} is {@code null}.
393 */
394 public int read(byte b[]) throws IOException {
395 return readBytes(b, 0, b.length);
396 }
397
398 /**
399 * Reads {@code b.length} bytes from this file into the byte
400 * array, starting at the current file pointer. This method reads
401 * repeatedly from the file until the requested number of bytes are
402 * read. This method blocks until the requested number of bytes are
403 * read, the end of the stream is detected, or an exception is thrown.
404 *
405 * @param b the buffer into which the data is 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 */
410 public final void readFully(byte b[]) throws IOException {
411 readFully(b, 0, b.length);
412 }
413
414 /**
415 * Reads exactly {@code len} bytes from this file into the byte
416 * array, starting at the current file pointer. This method reads
417 * repeatedly from the file until the requested number of bytes are
418 * read. This method blocks until the requested number of bytes are
419 * read, the end of the stream is detected, or an exception is thrown.
420 *
421 * @param b the buffer into which the data is read.
422 * @param off the start offset of the data.
423 * @param len the number of bytes to read.
424 * @exception EOFException if this file reaches the end before reading
425 * all the bytes.
426 * @exception IOException if an I/O error occurs.
427 */
428 public final void readFully(byte b[], int off, int len) throws IOException {
429 int n = 0;
430 do {
431 int count = this.read(b, off + n, len - n);
432 if (count < 0)
433 throw new EOFException();
434 n += count;
435 } while (n < len);
436 }
437
438 /**
439 * Attempts to skip over {@code n} bytes of input discarding the
440 * skipped bytes.
441 * <p>
442 *
443 * This method may skip over some smaller number of bytes, possibly zero.
444 * This may result from any of a number of conditions; reaching end of
445 * file before {@code n} bytes have been skipped is only one
446 * possibility. This method never throws an {@code EOFException}.
447 * The actual number of bytes skipped is returned. If {@code n}
448 * is negative, no bytes are skipped.
449 *
450 * @param n the number of bytes to be skipped.
451 * @return the actual number of bytes skipped.
452 * @exception IOException if an I/O error occurs.
453 */
454 public int skipBytes(int n) throws IOException {
455 long pos;
456 long len;
457 long newpos;
458
459 if (n <= 0) {
460 return 0;
461 }
462 pos = getFilePointer();
463 len = length();
464 newpos = pos + n;
465 if (newpos > len) {
466 newpos = len;
467 }
468 seek(newpos);
469
470 /* return the actual number of bytes skipped */
471 return (int) (newpos - pos);
472 }
473
474 // 'Write' primitives
475
476 /**
477 * Writes the specified byte to this file. The write starts at
478 * the current file pointer.
479 *
480 * @param b the {@code byte} to be written.
481 * @exception IOException if an I/O error occurs.
482 */
483 public void write(int b) throws IOException {
484 IoTraceContext traceContext = IoTrace.fileWriteBegin(path);
485 int v = 0;
486 try {
487 write0(b);
488 v = 1;
489 } finally {
490 IoTrace.fileWriteEnd(traceContext, v);
491 }
492 }
493
494 private native void write0(int b) throws IOException;
495
496 /**
497 * Writes a sub array as a sequence of bytes.
498 * @param b the data to be written
499 * @param off the start offset in the data
500 * @param len the number of bytes that are written
501 * @exception IOException If an I/O error has occurred.
502 */
503 private void writeBytes(byte b[], int off, int len) throws IOException {
504 IoTraceContext traceContext = IoTrace.fileWriteBegin(path);
505 int v = 0;
506 try {
507 writeBytes0(b, off, len);
508 v = len;
509 } finally {
510 IoTrace.fileWriteEnd(traceContext, v);
511 }
512 }
513
514 private native void writeBytes0(byte b[], int off, int len) throws IOException;
515
516 /**
517 * Writes {@code b.length} bytes from the specified byte array
518 * to this file, starting at the current file pointer.
519 *
520 * @param b the data.
521 * @exception IOException if an I/O error occurs.
522 */
523 public void write(byte b[]) throws IOException {
524 writeBytes(b, 0, b.length);
525 }
526
527 /**
528 * Writes {@code len} bytes from the specified byte array
529 * starting at offset {@code off} to this file.
530 *
531 * @param b the data.
532 * @param off the start offset in the data.
533 * @param len the number of bytes to write.
534 * @exception IOException if an I/O error occurs.
535 */
536 public void write(byte b[], int off, int len) throws IOException {
537 writeBytes(b, off, len);
538 }
539
540 // 'Random access' stuff
541
542 /**
543 * Returns the current offset in this file.
544 *
545 * @return the offset from the beginning of the file, in bytes,
546 * at which the next read or write occurs.
547 * @exception IOException if an I/O error occurs.
548 */
549 public native long getFilePointer() throws IOException;
550
551 /**
552 * Sets the file-pointer offset, measured from the beginning of this
553 * file, at which the next read or write occurs. The offset may be
554 * set beyond the end of the file. Setting the offset beyond the end
555 * of the file does not change the file length. The file length will
556 * change only by writing after the offset has been set beyond the end
557 * of the file.
558 *
559 * @param pos the offset position, measured in bytes from the
560 * beginning of the file, at which to set the file
561 * pointer.
562 * @exception IOException if {@code pos} is less than
563 * {@code 0} or if an I/O error occurs.
564 */
565 public native void seek(long pos) throws IOException;
566
567 /**
568 * Returns the length of this file.
569 *
570 * @return the length of this file, measured in bytes.
571 * @exception IOException if an I/O error occurs.
572 */
573 public native long length() throws IOException;
574
575 /**
576 * Sets the length of this file.
577 *
578 * <p> If the present length of the file as returned by the
579 * {@code length} method is greater than the {@code newLength}
580 * argument then the file will be truncated. In this case, if the file
581 * offset as returned by the {@code getFilePointer} method is greater
582 * than {@code newLength} then after this method returns the offset
583 * will be equal to {@code newLength}.
584 *
585 * <p> If the present length of the file as returned by the
586 * {@code length} method is smaller than the {@code newLength}
587 * argument then the file will be extended. In this case, the contents of
588 * the extended portion of the file are not defined.
589 *
590 * @param newLength The desired length of the file
591 * @exception IOException If an I/O error occurs
592 * @since 1.2
593 */
594 public native void setLength(long newLength) throws IOException;
595
596 /**
597 * Closes this random access file stream and releases any system
598 * resources associated with the stream. A closed random access
599 * file cannot perform input or output operations and cannot be
600 * reopened.
601 *
602 * <p> If this file has an associated channel then the channel is closed
603 * as well.
604 *
605 * @exception IOException if an I/O error occurs.
606 *
607 * @revised 1.4
608 * @spec JSR-51
609 */
610 public void close() throws IOException {
611 synchronized (closeLock) {
612 if (closed) {
613 return;
614 }
615 closed = true;
616 }
617 if (channel != null) {
618 channel.close();
619 }
620
621 fd.closeAll(new Closeable() {
622 public void close() throws IOException {
623 close0();
624 }
625 });
626 }
627
628 //
629 // Some "reading/writing Java data types" methods stolen from
630 // DataInputStream and DataOutputStream.
631 //
632
633 /**
634 * Reads a {@code boolean} from this file. This method reads a
635 * single byte from the file, starting at the current file pointer.
636 * A value of {@code 0} represents
637 * {@code false}. Any other value represents {@code true}.
638 * This method blocks until the byte is read, the end of the stream
639 * is detected, or an exception is thrown.
640 *
641 * @return the {@code boolean} value read.
642 * @exception EOFException if this file has reached the end.
643 * @exception IOException if an I/O error occurs.
644 */
645 public final boolean readBoolean() throws IOException {
646 int ch = this.read();
647 if (ch < 0)
648 throw new EOFException();
649 return (ch != 0);
650 }
651
652 /**
653 * Reads a signed eight-bit value from this file. This method reads a
654 * byte from the file, starting from the current file pointer.
655 * If the byte read is {@code b}, where
656 * <code>0 <= b <= 255</code>,
657 * then the result is:
658 * <blockquote><pre>
659 * (byte)(b)
660 * </pre></blockquote>
661 * <p>
662 * This method blocks until the byte is read, the end of the stream
663 * is detected, or an exception is thrown.
664 *
665 * @return the next byte of this file as a signed eight-bit
666 * {@code byte}.
667 * @exception EOFException if this file has reached the end.
668 * @exception IOException if an I/O error occurs.
669 */
670 public final byte readByte() throws IOException {
671 int ch = this.read();
672 if (ch < 0)
673 throw new EOFException();
674 return (byte)(ch);
675 }
676
677 /**
678 * Reads an unsigned eight-bit number from this file. This method reads
679 * a byte from this file, starting at the current file pointer,
680 * and returns that byte.
681 * <p>
682 * This method blocks until the byte is read, the end of the stream
683 * is detected, or an exception is thrown.
684 *
685 * @return the next byte of this file, interpreted as an unsigned
686 * eight-bit number.
687 * @exception EOFException if this file has reached the end.
688 * @exception IOException if an I/O error occurs.
689 */
690 public final int readUnsignedByte() throws IOException {
691 int ch = this.read();
692 if (ch < 0)
693 throw new EOFException();
694 return ch;
695 }
696
697 /**
698 * Reads a signed 16-bit number from this file. The method reads two
699 * bytes from this file, starting at the current file pointer.
700 * If the two bytes read, in order, are
701 * {@code b1} and {@code b2}, where each of the two values is
702 * between {@code 0} and {@code 255}, inclusive, then the
703 * result is equal to:
704 * <blockquote><pre>
705 * (short)((b1 << 8) | b2)
706 * </pre></blockquote>
707 * <p>
708 * This method blocks until the two bytes are read, the end of the
709 * stream is detected, or an exception is thrown.
710 *
711 * @return the next two bytes of this file, interpreted as a signed
712 * 16-bit number.
713 * @exception EOFException if this file reaches the end before reading
714 * two bytes.
715 * @exception IOException if an I/O error occurs.
716 */
717 public final short readShort() throws IOException {
718 int ch1 = this.read();
719 int ch2 = this.read();
720 if ((ch1 | ch2) < 0)
721 throw new EOFException();
722 return (short)((ch1 << 8) + (ch2 << 0));
723 }
724
725 /**
726 * Reads an unsigned 16-bit number from this file. This method reads
727 * two bytes from the file, starting at the current file pointer.
728 * If the bytes read, in order, are
729 * {@code b1} and {@code b2}, where
730 * <code>0 <= b1, b2 <= 255</code>,
731 * then the result is equal to:
732 * <blockquote><pre>
733 * (b1 << 8) | b2
734 * </pre></blockquote>
735 * <p>
736 * This method blocks until the two bytes are read, the end of the
737 * stream is detected, or an exception is thrown.
738 *
739 * @return the next two bytes of this file, interpreted as an unsigned
740 * 16-bit integer.
741 * @exception EOFException if this file reaches the end before reading
742 * two bytes.
743 * @exception IOException if an I/O error occurs.
744 */
745 public final int readUnsignedShort() throws IOException {
746 int ch1 = this.read();
747 int ch2 = this.read();
748 if ((ch1 | ch2) < 0)
749 throw new EOFException();
750 return (ch1 << 8) + (ch2 << 0);
751 }
752
753 /**
754 * Reads a character from this file. This method reads two
755 * bytes from the file, starting at the current file pointer.
756 * If the bytes read, in order, are
757 * {@code b1} and {@code b2}, where
758 * <code>0 <= b1, b2 <= 255</code>,
759 * then the result is equal to:
760 * <blockquote><pre>
761 * (char)((b1 << 8) | b2)
762 * </pre></blockquote>
763 * <p>
764 * This method blocks until the two bytes are read, the end of the
765 * stream is detected, or an exception is thrown.
766 *
767 * @return the next two bytes of this file, interpreted as a
768 * {@code char}.
769 * @exception EOFException if this file reaches the end before reading
770 * two bytes.
771 * @exception IOException if an I/O error occurs.
772 */
773 public final char readChar() throws IOException {
774 int ch1 = this.read();
775 int ch2 = this.read();
776 if ((ch1 | ch2) < 0)
777 throw new EOFException();
778 return (char)((ch1 << 8) + (ch2 << 0));
779 }
780
781 /**
782 * Reads a signed 32-bit integer from this file. This method reads 4
783 * bytes from the file, starting at the current file pointer.
784 * If the bytes read, in order, are {@code b1},
785 * {@code b2}, {@code b3}, and {@code b4}, where
786 * <code>0 <= b1, b2, b3, b4 <= 255</code>,
787 * then the result is equal to:
788 * <blockquote><pre>
789 * (b1 << 24) | (b2 << 16) + (b3 << 8) + b4
790 * </pre></blockquote>
791 * <p>
792 * This method blocks until the four bytes are read, the end of the
793 * stream is detected, or an exception is thrown.
794 *
795 * @return the next four bytes of this file, interpreted as an
796 * {@code int}.
797 * @exception EOFException if this file reaches the end before reading
798 * four bytes.
799 * @exception IOException if an I/O error occurs.
800 */
801 public final int readInt() throws IOException {
802 int ch1 = this.read();
803 int ch2 = this.read();
804 int ch3 = this.read();
805 int ch4 = this.read();
806 if ((ch1 | ch2 | ch3 | ch4) < 0)
807 throw new EOFException();
808 return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
809 }
810
811 /**
812 * Reads a signed 64-bit integer from this file. This method reads eight
813 * bytes from the file, starting at the current file pointer.
814 * If the bytes read, in order, are
815 * {@code b1}, {@code b2}, {@code b3},
816 * {@code b4}, {@code b5}, {@code b6},
817 * {@code b7}, and {@code b8,} where:
818 * <blockquote><pre>
819 * 0 <= b1, b2, b3, b4, b5, b6, b7, b8 <=255,
820 * </pre></blockquote>
821 * <p>
822 * then the result is equal to:
823 * <p><blockquote><pre>
824 * ((long)b1 << 56) + ((long)b2 << 48)
825 * + ((long)b3 << 40) + ((long)b4 << 32)
826 * + ((long)b5 << 24) + ((long)b6 << 16)
827 * + ((long)b7 << 8) + b8
828 * </pre></blockquote>
829 * <p>
830 * This method blocks until the eight bytes are read, the end of the
831 * stream is detected, or an exception is thrown.
832 *
833 * @return the next eight bytes of this file, interpreted as a
834 * {@code long}.
835 * @exception EOFException if this file reaches the end before reading
836 * eight bytes.
837 * @exception IOException if an I/O error occurs.
838 */
839 public final long readLong() throws IOException {
840 return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
841 }
842
843 /**
844 * Reads a {@code float} from this file. This method reads an
845 * {@code int} value, starting at the current file pointer,
846 * as if by the {@code readInt} method
847 * and then converts that {@code int} to a {@code float}
848 * using the {@code intBitsToFloat} method in class
849 * {@code Float}.
850 * <p>
851 * This method blocks until the four bytes are read, the end of the
852 * stream is detected, or an exception is thrown.
853 *
854 * @return the next four bytes of this file, interpreted as a
855 * {@code float}.
856 * @exception EOFException if this file reaches the end before reading
857 * four bytes.
858 * @exception IOException if an I/O error occurs.
859 * @see java.io.RandomAccessFile#readInt()
860 * @see java.lang.Float#intBitsToFloat(int)
861 */
862 public final float readFloat() throws IOException {
863 return Float.intBitsToFloat(readInt());
864 }
865
866 /**
867 * Reads a {@code double} from this file. This method reads a
868 * {@code long} value, starting at the current file pointer,
869 * as if by the {@code readLong} method
870 * and then converts that {@code long} to a {@code double}
871 * using the {@code longBitsToDouble} method in
872 * class {@code Double}.
873 * <p>
874 * This method blocks until the eight bytes are read, the end of the
875 * stream is detected, or an exception is thrown.
876 *
877 * @return the next eight bytes of this file, interpreted as a
878 * {@code double}.
879 * @exception EOFException if this file reaches the end before reading
880 * eight bytes.
881 * @exception IOException if an I/O error occurs.
882 * @see java.io.RandomAccessFile#readLong()
883 * @see java.lang.Double#longBitsToDouble(long)
884 */
885 public final double readDouble() throws IOException {
886 return Double.longBitsToDouble(readLong());
887 }
888
889 /**
890 * Reads the next line of text from this file. This method successively
891 * reads bytes from the file, starting at the current file pointer,
892 * until it reaches a line terminator or the end
893 * of the file. Each byte is converted into a character by taking the
894 * byte's value for the lower eight bits of the character and setting the
895 * high eight bits of the character to zero. This method does not,
896 * therefore, support the full Unicode character set.
897 *
898 * <p> A line of text is terminated by a carriage-return character
899 * ({@code '\u005Cr'}), a newline character ({@code '\u005Cn'}), a
900 * carriage-return character immediately followed by a newline character,
901 * or the end of the file. Line-terminating characters are discarded and
902 * are not included as part of the string returned.
903 *
904 * <p> This method blocks until a newline character is read, a carriage
905 * return and the byte following it are read (to see if it is a newline),
906 * the end of the file is reached, or an exception is thrown.
907 *
908 * @return the next line of text from this file, or null if end
909 * of file is encountered before even one byte is read.
910 * @exception IOException if an I/O error occurs.
911 */
912
913 public final String readLine() throws IOException {
914 StringBuffer input = new StringBuffer();
915 int c = -1;
916 boolean eol = false;
917
918 while (!eol) {
919 switch (c = read()) {
920 case -1:
921 case '\n':
922 eol = true;
923 break;
924 case '\r':
925 eol = true;
926 long cur = getFilePointer();
927 if ((read()) != '\n') {
928 seek(cur);
929 }
930 break;
931 default:
932 input.append((char)c);
933 break;
934 }
935 }
936
937 if ((c == -1) && (input.length() == 0)) {
938 return null;
939 }
940 return input.toString();
941 }
942
943 /**
944 * Reads in a string from this file. The string has been encoded
945 * using a
946 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
947 * format.
948 * <p>
949 * The first two bytes are read, starting from the current file
950 * pointer, as if by
951 * {@code readUnsignedShort}. This value gives the number of
952 * following bytes that are in the encoded string, not
953 * the length of the resulting string. The following bytes are then
954 * interpreted as bytes encoding characters in the modified UTF-8 format
955 * and are converted into characters.
956 * <p>
957 * This method blocks until all the bytes are read, the end of the
958 * stream is detected, or an exception is thrown.
959 *
960 * @return a Unicode string.
961 * @exception EOFException if this file reaches the end before
962 * reading all the bytes.
963 * @exception IOException if an I/O error occurs.
964 * @exception UTFDataFormatException if the bytes do not represent
965 * valid modified UTF-8 encoding of a Unicode string.
966 * @see java.io.RandomAccessFile#readUnsignedShort()
967 */
968 public final String readUTF() throws IOException {
969 return DataInputStream.readUTF(this);
970 }
971
972 /**
973 * Writes a {@code boolean} to the file as a one-byte value. The
974 * value {@code true} is written out as the value
975 * {@code (byte)1}; the value {@code false} is written out
976 * as the value {@code (byte)0}. The write starts at
977 * the current position of the file pointer.
978 *
979 * @param v a {@code boolean} value to be written.
980 * @exception IOException if an I/O error occurs.
981 */
982 public final void writeBoolean(boolean v) throws IOException {
983 write(v ? 1 : 0);
984 //written++;
985 }
986
987 /**
988 * Writes a {@code byte} to the file as a one-byte value. The
989 * write starts at the current position of the file pointer.
990 *
991 * @param v a {@code byte} value to be written.
992 * @exception IOException if an I/O error occurs.
993 */
994 public final void writeByte(int v) throws IOException {
995 write(v);
996 //written++;
997 }
998
999 /**
1000 * Writes a {@code short} to the file as two bytes, high byte first.
1001 * The write starts at the current position of the file pointer.
1002 *
1003 * @param v a {@code short} to be written.
1004 * @exception IOException if an I/O error occurs.
1005 */
1006 public final void writeShort(int v) throws IOException {
1007 write((v >>> 8) & 0xFF);
1008 write((v >>> 0) & 0xFF);
1009 //written += 2;
1010 }
1011
1012 /**
1013 * Writes a {@code char} to the file as a two-byte value, high
1014 * byte first. The write starts at the current position of the
1015 * file pointer.
1016 *
1017 * @param v a {@code char} value to be written.
1018 * @exception IOException if an I/O error occurs.
1019 */
1020 public final void writeChar(int v) throws IOException {
1021 write((v >>> 8) & 0xFF);
1022 write((v >>> 0) & 0xFF);
1023 //written += 2;
1024 }
1025
1026 /**
1027 * Writes an {@code int} to the file as four bytes, high byte first.
1028 * The write starts at the current position of the file pointer.
1029 *
1030 * @param v an {@code int} to be written.
1031 * @exception IOException if an I/O error occurs.
1032 */
1033 public final void writeInt(int v) throws IOException {
1034 write((v >>> 24) & 0xFF);
1035 write((v >>> 16) & 0xFF);
1036 write((v >>> 8) & 0xFF);
1037 write((v >>> 0) & 0xFF);
1038 //written += 4;
1039 }
1040
1041 /**
1042 * Writes a {@code long} to the file as eight bytes, high byte first.
1043 * The write starts at the current position of the file pointer.
1044 *
1045 * @param v a {@code long} to be written.
1046 * @exception IOException if an I/O error occurs.
1047 */
1048 public final void writeLong(long v) throws IOException {
1049 write((int)(v >>> 56) & 0xFF);
1050 write((int)(v >>> 48) & 0xFF);
1051 write((int)(v >>> 40) & 0xFF);
1052 write((int)(v >>> 32) & 0xFF);
1053 write((int)(v >>> 24) & 0xFF);
1054 write((int)(v >>> 16) & 0xFF);
1055 write((int)(v >>> 8) & 0xFF);
1056 write((int)(v >>> 0) & 0xFF);
1057 //written += 8;
1058 }
1059
1060 /**
1061 * Converts the float argument to an {@code int} using the
1062 * {@code floatToIntBits} method in class {@code Float},
1063 * and then writes that {@code int} value to the file as a
1064 * four-byte quantity, high byte first. The write starts at the
1065 * current position of the file pointer.
1066 *
1067 * @param v a {@code float} value to be written.
1068 * @exception IOException if an I/O error occurs.
1069 * @see java.lang.Float#floatToIntBits(float)
1070 */
1071 public final void writeFloat(float v) throws IOException {
1072 writeInt(Float.floatToIntBits(v));
1073 }
1074
1075 /**
1076 * Converts the double argument to a {@code long} using the
1077 * {@code doubleToLongBits} method in class {@code Double},
1078 * and then writes that {@code long} value to the file as an
1079 * eight-byte quantity, high byte first. The write starts at the current
1080 * position of the file pointer.
1081 *
1082 * @param v a {@code double} value to be written.
1083 * @exception IOException if an I/O error occurs.
1084 * @see java.lang.Double#doubleToLongBits(double)
1085 */
1086 public final void writeDouble(double v) throws IOException {
1087 writeLong(Double.doubleToLongBits(v));
1088 }
1089
1090 /**
1091 * Writes the string to the file as a sequence of bytes. Each
1092 * character in the string is written out, in sequence, by discarding
1093 * its high eight bits. The write starts at the current position of
1094 * the file pointer.
1095 *
1096 * @param s a string of bytes to be written.
1097 * @exception IOException if an I/O error occurs.
1098 */
1099 @SuppressWarnings("deprecation")
1100 public final void writeBytes(String s) throws IOException {
1101 int len = s.length();
1102 byte[] b = new byte[len];
1103 s.getBytes(0, len, b, 0);
1104 writeBytes(b, 0, len);
1105 }
1106
1107 /**
1108 * Writes a string to the file as a sequence of characters. Each
1109 * character is written to the data output stream as if by the
1110 * {@code writeChar} method. The write starts at the current
1111 * position of the file pointer.
1112 *
1113 * @param s a {@code String} value to be written.
1114 * @exception IOException if an I/O error occurs.
1115 * @see java.io.RandomAccessFile#writeChar(int)
1116 */
1117 public final void writeChars(String s) throws IOException {
1118 int clen = s.length();
1119 int blen = 2*clen;
1120 byte[] b = new byte[blen];
1121 char[] c = new char[clen];
1122 s.getChars(0, clen, c, 0);
1123 for (int i = 0, j = 0; i < clen; i++) {
1124 b[j++] = (byte)(c[i] >>> 8);
1125 b[j++] = (byte)(c[i] >>> 0);
1126 }
1127 writeBytes(b, 0, blen);
1128 }
1129
1130 /**
1131 * Writes a string to the file using
1132 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
1133 * encoding in a machine-independent manner.
1134 * <p>
1135 * First, two bytes are written to the file, starting at the
1136 * current file pointer, as if by the
1137 * {@code writeShort} method giving the number of bytes to
1138 * follow. This value is the number of bytes actually written out,
1139 * not the length of the string. Following the length, each character
1140 * of the string is output, in sequence, using the modified UTF-8 encoding
1141 * for each character.
1142 *
1143 * @param str a string to be written.
1144 * @exception IOException if an I/O error occurs.
1145 */
1146 public final void writeUTF(String str) throws IOException {
1147 DataOutputStream.writeUTF(str, this);
1148 }
1149
1150 private static native void initIDs();
1151
1152 private native void close0() throws IOException;
1153
1154 static {
1155 initIDs();
1156 }
1157 }