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