0001 /*
0002 * Copyright 1994-2007 Sun Microsystems, Inc. All Rights Reserved.
0003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
0004 *
0005 * This code is free software; you can redistribute it and/or modify it
0006 * under the terms of the GNU General Public License version 2 only, as
0007 * published by the Free Software Foundation. Sun designates this
0008 * particular file as subject to the "Classpath" exception as provided
0009 * by Sun in the LICENSE file that accompanied this code.
0010 *
0011 * This code is distributed in the hope that it will be useful, but WITHOUT
0012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
0013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
0014 * version 2 for more details (a copy is included in the LICENSE file that
0015 * accompanied this code).
0016 *
0017 * You should have received a copy of the GNU General Public License version
0018 * 2 along with this work; if not, write to the Free Software Foundation,
0019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
0020 *
0021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
0022 * CA 95054 USA or visit www.sun.com if you need additional information or
0023 * have any questions.
0024 */
0025
0026 package java.io;
0027
0028 import java.nio.channels.FileChannel;
0029 import sun.nio.ch.FileChannelImpl;
0030
0031 /**
0032 * Instances of this class support both reading and writing to a
0033 * random access file. A random access file behaves like a large
0034 * array of bytes stored in the file system. There is a kind of cursor,
0035 * or index into the implied array, called the <em>file pointer</em>;
0036 * input operations read bytes starting at the file pointer and advance
0037 * the file pointer past the bytes read. If the random access file is
0038 * created in read/write mode, then output operations are also available;
0039 * output operations write bytes starting at the file pointer and advance
0040 * the file pointer past the bytes written. Output operations that write
0041 * past the current end of the implied array cause the array to be
0042 * extended. The file pointer can be read by the
0043 * <code>getFilePointer</code> method and set by the <code>seek</code>
0044 * method.
0045 * <p>
0046 * It is generally true of all the reading routines in this class that
0047 * if end-of-file is reached before the desired number of bytes has been
0048 * read, an <code>EOFException</code> (which is a kind of
0049 * <code>IOException</code>) is thrown. If any byte cannot be read for
0050 * any reason other than end-of-file, an <code>IOException</code> other
0051 * than <code>EOFException</code> is thrown. In particular, an
0052 * <code>IOException</code> may be thrown if the stream has been closed.
0053 *
0054 * @author unascribed
0055 * @version 1.90, 06/13/07
0056 * @since JDK1.0
0057 */
0058
0059 public class RandomAccessFile implements DataOutput, DataInput,
0060 Closeable {
0061
0062 private FileDescriptor fd;
0063 private FileChannel channel = null;
0064 private boolean rw;
0065
0066 private Object closeLock = new Object();
0067 private volatile boolean closed = false;
0068
0069 private static final int O_RDONLY = 1;
0070 private static final int O_RDWR = 2;
0071 private static final int O_SYNC = 4;
0072 private static final int O_DSYNC = 8;
0073
0074 /**
0075 * Creates a random access file stream to read from, and optionally
0076 * to write to, a file with the specified name. A new
0077 * {@link FileDescriptor} object is created to represent the
0078 * connection to the file.
0079 *
0080 * <p> The <tt>mode</tt> argument specifies the access mode with which the
0081 * file is to be opened. The permitted values and their meanings are as
0082 * specified for the <a
0083 * href="#mode"><tt>RandomAccessFile(File,String)</tt></a> constructor.
0084 *
0085 * <p>
0086 * If there is a security manager, its <code>checkRead</code> method
0087 * is called with the <code>name</code> argument
0088 * as its argument to see if read access to the file is allowed.
0089 * If the mode allows writing, the security manager's
0090 * <code>checkWrite</code> method
0091 * is also called with the <code>name</code> argument
0092 * as its argument to see if write access to the file is allowed.
0093 *
0094 * @param name the system-dependent filename
0095 * @param mode the access <a href="#mode">mode</a>
0096 * @exception IllegalArgumentException if the mode argument is not equal
0097 * to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
0098 * <tt>"rwd"</tt>
0099 * @exception FileNotFoundException
0100 * if the mode is <tt>"r"</tt> but the given string does not
0101 * denote an existing regular file, or if the mode begins with
0102 * <tt>"rw"</tt> but the given string does not denote an
0103 * existing, writable regular file and a new regular file of
0104 * that name cannot be created, or if some other error occurs
0105 * while opening or creating the file
0106 * @exception SecurityException if a security manager exists and its
0107 * <code>checkRead</code> method denies read access to the file
0108 * or the mode is "rw" and the security manager's
0109 * <code>checkWrite</code> method denies write access to the file
0110 * @see java.lang.SecurityException
0111 * @see java.lang.SecurityManager#checkRead(java.lang.String)
0112 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
0113 * @revised 1.4
0114 * @spec JSR-51
0115 */
0116 public RandomAccessFile(String name, String mode)
0117 throws FileNotFoundException {
0118 this (name != null ? new File(name) : null, mode);
0119 }
0120
0121 /**
0122 * Creates a random access file stream to read from, and optionally to
0123 * write to, the file specified by the {@link File} argument. A new {@link
0124 * FileDescriptor} object is created to represent this file connection.
0125 *
0126 * <a name="mode"><p> The <tt>mode</tt> argument specifies the access mode
0127 * in which the file is to be opened. The permitted values and their
0128 * meanings are:
0129 *
0130 * <blockquote><table summary="Access mode permitted values and meanings">
0131 * <tr><th><p align="left">Value</p></th><th><p align="left">Meaning</p></th></tr>
0132 * <tr><td valign="top"><tt>"r"</tt></td>
0133 * <td> Open for reading only. Invoking any of the <tt>write</tt>
0134 * methods of the resulting object will cause an {@link
0135 * java.io.IOException} to be thrown. </td></tr>
0136 * <tr><td valign="top"><tt>"rw"</tt></td>
0137 * <td> Open for reading and writing. If the file does not already
0138 * exist then an attempt will be made to create it. </td></tr>
0139 * <tr><td valign="top"><tt>"rws"</tt></td>
0140 * <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
0141 * require that every update to the file's content or metadata be
0142 * written synchronously to the underlying storage device. </td></tr>
0143 * <tr><td valign="top"><tt>"rwd" </tt></td>
0144 * <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
0145 * require that every update to the file's content be written
0146 * synchronously to the underlying storage device. </td></tr>
0147 * </table></blockquote>
0148 *
0149 * The <tt>"rws"</tt> and <tt>"rwd"</tt> modes work much like the {@link
0150 * java.nio.channels.FileChannel#force(boolean) force(boolean)} method of
0151 * the {@link java.nio.channels.FileChannel} class, passing arguments of
0152 * <tt>true</tt> and <tt>false</tt>, respectively, except that they always
0153 * apply to every I/O operation and are therefore often more efficient. If
0154 * the file resides on a local storage device then when an invocation of a
0155 * method of this class returns it is guaranteed that all changes made to
0156 * the file by that invocation will have been written to that device. This
0157 * is useful for ensuring that critical information is not lost in the
0158 * event of a system crash. If the file does not reside on a local device
0159 * then no such guarantee is made.
0160 *
0161 * <p> The <tt>"rwd"</tt> mode can be used to reduce the number of I/O
0162 * operations performed. Using <tt>"rwd"</tt> only requires updates to the
0163 * file's content to be written to storage; using <tt>"rws"</tt> requires
0164 * updates to both the file's content and its metadata to be written, which
0165 * generally requires at least one more low-level I/O operation.
0166 *
0167 * <p> If there is a security manager, its <code>checkRead</code> method is
0168 * called with the pathname of the <code>file</code> argument as its
0169 * argument to see if read access to the file is allowed. If the mode
0170 * allows writing, the security manager's <code>checkWrite</code> method is
0171 * also called with the path argument to see if write access to the file is
0172 * allowed.
0173 *
0174 * @param file the file object
0175 * @param mode the access mode, as described
0176 * <a href="#mode">above</a>
0177 * @exception IllegalArgumentException if the mode argument is not equal
0178 * to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
0179 * <tt>"rwd"</tt>
0180 * @exception FileNotFoundException
0181 * if the mode is <tt>"r"</tt> but the given file object does
0182 * not denote an existing regular file, or if the mode begins
0183 * with <tt>"rw"</tt> but the given file object does not denote
0184 * an existing, writable regular file and a new regular file of
0185 * that name cannot be created, or if some other error occurs
0186 * while opening or creating the file
0187 * @exception SecurityException if a security manager exists and its
0188 * <code>checkRead</code> method denies read access to the file
0189 * or the mode is "rw" and the security manager's
0190 * <code>checkWrite</code> method denies write access to the file
0191 * @see java.lang.SecurityManager#checkRead(java.lang.String)
0192 * @see java.lang.SecurityManager#checkWrite(java.lang.String)
0193 * @see java.nio.channels.FileChannel#force(boolean)
0194 * @revised 1.4
0195 * @spec JSR-51
0196 */
0197 public RandomAccessFile(File file, String mode)
0198 throws FileNotFoundException {
0199 String name = (file != null ? file.getPath() : null);
0200 int imode = -1;
0201 if (mode.equals("r"))
0202 imode = O_RDONLY;
0203 else if (mode.startsWith("rw")) {
0204 imode = O_RDWR;
0205 rw = true;
0206 if (mode.length() > 2) {
0207 if (mode.equals("rws"))
0208 imode |= O_SYNC;
0209 else if (mode.equals("rwd"))
0210 imode |= O_DSYNC;
0211 else
0212 imode = -1;
0213 }
0214 }
0215 if (imode < 0)
0216 throw new IllegalArgumentException("Illegal mode \"" + mode
0217 + "\" must be one of " + "\"r\", \"rw\", \"rws\","
0218 + " or \"rwd\"");
0219 SecurityManager security = System.getSecurityManager();
0220 if (security != null) {
0221 security.checkRead(name);
0222 if (rw) {
0223 security.checkWrite(name);
0224 }
0225 }
0226 if (name == null) {
0227 throw new NullPointerException();
0228 }
0229 fd = new FileDescriptor();
0230 fd.incrementAndGetUseCount();
0231 open(name, imode);
0232 }
0233
0234 /**
0235 * Returns the opaque file descriptor object associated with this
0236 * stream. </p>
0237 *
0238 * @return the file descriptor object associated with this stream.
0239 * @exception IOException if an I/O error occurs.
0240 * @see java.io.FileDescriptor
0241 */
0242 public final FileDescriptor getFD() throws IOException {
0243 if (fd != null)
0244 return fd;
0245 throw new IOException();
0246 }
0247
0248 /**
0249 * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
0250 * object associated with this file.
0251 *
0252 * <p> The {@link java.nio.channels.FileChannel#position()
0253 * </code>position<code>} of the returned channel will always be equal to
0254 * this object's file-pointer offset as returned by the {@link
0255 * #getFilePointer getFilePointer} method. Changing this object's
0256 * file-pointer offset, whether explicitly or by reading or writing bytes,
0257 * will change the position of the channel, and vice versa. Changing the
0258 * file's length via this object will change the length seen via the file
0259 * channel, and vice versa.
0260 *
0261 * @return the file channel associated with this file
0262 *
0263 * @since 1.4
0264 * @spec JSR-51
0265 */
0266 public final FileChannel getChannel() {
0267 synchronized (this ) {
0268 if (channel == null) {
0269 channel = FileChannelImpl.open(fd, true, rw, this );
0270
0271 /*
0272 * FileDescriptor could be shared by FileInputStream or
0273 * FileOutputStream.
0274 * Ensure that FD is GC'ed only when all the streams/channels
0275 * are done using it.
0276 * Increment fd's use count. Invoking the channel's close()
0277 * method will result in decrementing the use count set for
0278 * the channel.
0279 */
0280 fd.incrementAndGetUseCount();
0281 }
0282 return channel;
0283 }
0284 }
0285
0286 /**
0287 * Opens a file and returns the file descriptor. The file is
0288 * opened in read-write mode if the O_RDWR bit in <code>mode</code>
0289 * is true, else the file is opened as read-only.
0290 * If the <code>name</code> refers to a directory, an IOException
0291 * is thrown.
0292 *
0293 * @param name the name of the file
0294 * @param mode the mode flags, a combination of the O_ constants
0295 * defined above
0296 */
0297 private native void open(String name, int mode)
0298 throws FileNotFoundException;
0299
0300 // 'Read' primitives
0301
0302 /**
0303 * Reads a byte of data from this file. The byte is returned as an
0304 * integer in the range 0 to 255 (<code>0x00-0x0ff</code>). This
0305 * method blocks if no input is yet available.
0306 * <p>
0307 * Although <code>RandomAccessFile</code> is not a subclass of
0308 * <code>InputStream</code>, this method behaves in exactly the same
0309 * way as the {@link InputStream#read()} method of
0310 * <code>InputStream</code>.
0311 *
0312 * @return the next byte of data, or <code>-1</code> if the end of the
0313 * file has been reached.
0314 * @exception IOException if an I/O error occurs. Not thrown if
0315 * end-of-file has been reached.
0316 */
0317 public native int read() throws IOException;
0318
0319 /**
0320 * Reads a sub array as a sequence of bytes.
0321 * @param b the buffer into which the data is read.
0322 * @param off the start offset of the data.
0323 * @param len the number of bytes to read.
0324 * @exception IOException If an I/O error has occurred.
0325 */
0326 private native int readBytes(byte b[], int off, int len)
0327 throws IOException;
0328
0329 /**
0330 * Reads up to <code>len</code> bytes of data from this file into an
0331 * array of bytes. This method blocks until at least one byte of input
0332 * is available.
0333 * <p>
0334 * Although <code>RandomAccessFile</code> is not a subclass of
0335 * <code>InputStream</code>, this method behaves in exactly the
0336 * same way as the {@link InputStream#read(byte[], int, int)} method of
0337 * <code>InputStream</code>.
0338 *
0339 * @param b the buffer into which the data is read.
0340 * @param off the start offset in array <code>b</code>
0341 * at which the data is written.
0342 * @param len the maximum number of bytes read.
0343 * @return the total number of bytes read into the buffer, or
0344 * <code>-1</code> if there is no more data because the end of
0345 * the file has been reached.
0346 * @exception IOException If the first byte cannot be read for any reason
0347 * other than end of file, or if the random access file has been closed, or if
0348 * some other I/O error occurs.
0349 * @exception NullPointerException If <code>b</code> is <code>null</code>.
0350 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
0351 * <code>len</code> is negative, or <code>len</code> is greater than
0352 * <code>b.length - off</code>
0353 */
0354 public int read(byte b[], int off, int len) throws IOException {
0355 return readBytes(b, off, len);
0356 }
0357
0358 /**
0359 * Reads up to <code>b.length</code> bytes of data from this file
0360 * into an array of bytes. This method blocks until at least one byte
0361 * of input is available.
0362 * <p>
0363 * Although <code>RandomAccessFile</code> is not a subclass of
0364 * <code>InputStream</code>, this method behaves in exactly the
0365 * same way as the {@link InputStream#read(byte[])} method of
0366 * <code>InputStream</code>.
0367 *
0368 * @param b the buffer into which the data is read.
0369 * @return the total number of bytes read into the buffer, or
0370 * <code>-1</code> if there is no more data because the end of
0371 * this file has been reached.
0372 * @exception IOException If the first byte cannot be read for any reason
0373 * other than end of file, or if the random access file has been closed, or if
0374 * some other I/O error occurs.
0375 * @exception NullPointerException If <code>b</code> is <code>null</code>.
0376 */
0377 public int read(byte b[]) throws IOException {
0378 return readBytes(b, 0, b.length);
0379 }
0380
0381 /**
0382 * Reads <code>b.length</code> bytes from this file into the byte
0383 * array, starting at the current file pointer. This method reads
0384 * repeatedly from the file until the requested number of bytes are
0385 * read. This method blocks until the requested number of bytes are
0386 * read, the end of the stream is detected, or an exception is thrown.
0387 *
0388 * @param b the buffer into which the data is read.
0389 * @exception EOFException if this file reaches the end before reading
0390 * all the bytes.
0391 * @exception IOException if an I/O error occurs.
0392 */
0393 public final void readFully(byte b[]) throws IOException {
0394 readFully(b, 0, b.length);
0395 }
0396
0397 /**
0398 * Reads exactly <code>len</code> bytes from this file into the byte
0399 * array, starting at the current file pointer. This method reads
0400 * repeatedly from the file until the requested number of bytes are
0401 * read. This method blocks until the requested number of bytes are
0402 * read, the end of the stream is detected, or an exception is thrown.
0403 *
0404 * @param b the buffer into which the data is read.
0405 * @param off the start offset of the data.
0406 * @param len the number of bytes to read.
0407 * @exception EOFException if this file reaches the end before reading
0408 * all the bytes.
0409 * @exception IOException if an I/O error occurs.
0410 */
0411 public final void readFully(byte b[], int off, int len)
0412 throws IOException {
0413 int n = 0;
0414 do {
0415 int count = this .read(b, off + n, len - n);
0416 if (count < 0)
0417 throw new EOFException();
0418 n += count;
0419 } while (n < len);
0420 }
0421
0422 /**
0423 * Attempts to skip over <code>n</code> bytes of input discarding the
0424 * skipped bytes.
0425 * <p>
0426 *
0427 * This method may skip over some smaller number of bytes, possibly zero.
0428 * This may result from any of a number of conditions; reaching end of
0429 * file before <code>n</code> bytes have been skipped is only one
0430 * possibility. This method never throws an <code>EOFException</code>.
0431 * The actual number of bytes skipped is returned. If <code>n</code>
0432 * is negative, no bytes are skipped.
0433 *
0434 * @param n the number of bytes to be skipped.
0435 * @return the actual number of bytes skipped.
0436 * @exception IOException if an I/O error occurs.
0437 */
0438 public int skipBytes(int n) throws IOException {
0439 long pos;
0440 long len;
0441 long newpos;
0442
0443 if (n <= 0) {
0444 return 0;
0445 }
0446 pos = getFilePointer();
0447 len = length();
0448 newpos = pos + n;
0449 if (newpos > len) {
0450 newpos = len;
0451 }
0452 seek(newpos);
0453
0454 /* return the actual number of bytes skipped */
0455 return (int) (newpos - pos);
0456 }
0457
0458 // 'Write' primitives
0459
0460 /**
0461 * Writes the specified byte to this file. The write starts at
0462 * the current file pointer.
0463 *
0464 * @param b the <code>byte</code> to be written.
0465 * @exception IOException if an I/O error occurs.
0466 */
0467 public native void write(int b) throws IOException;
0468
0469 /**
0470 * Writes a sub array as a sequence of bytes.
0471 * @param b the data to be written
0472
0473 * @param off the start offset in the data
0474 * @param len the number of bytes that are written
0475 * @exception IOException If an I/O error has occurred.
0476 */
0477 private native void writeBytes(byte b[], int off, int len)
0478 throws IOException;
0479
0480 /**
0481 * Writes <code>b.length</code> bytes from the specified byte array
0482 * to this file, starting at the current file pointer.
0483 *
0484 * @param b the data.
0485 * @exception IOException if an I/O error occurs.
0486 */
0487 public void write(byte b[]) throws IOException {
0488 writeBytes(b, 0, b.length);
0489 }
0490
0491 /**
0492 * Writes <code>len</code> bytes from the specified byte array
0493 * starting at offset <code>off</code> to this file.
0494 *
0495 * @param b the data.
0496 * @param off the start offset in the data.
0497 * @param len the number of bytes to write.
0498 * @exception IOException if an I/O error occurs.
0499 */
0500 public void write(byte b[], int off, int len) throws IOException {
0501 writeBytes(b, off, len);
0502 }
0503
0504 // 'Random access' stuff
0505
0506 /**
0507 * Returns the current offset in this file.
0508 *
0509 * @return the offset from the beginning of the file, in bytes,
0510 * at which the next read or write occurs.
0511 * @exception IOException if an I/O error occurs.
0512 */
0513 public native long getFilePointer() throws IOException;
0514
0515 /**
0516 * Sets the file-pointer offset, measured from the beginning of this
0517 * file, at which the next read or write occurs. The offset may be
0518 * set beyond the end of the file. Setting the offset beyond the end
0519 * of the file does not change the file length. The file length will
0520 * change only by writing after the offset has been set beyond the end
0521 * of the file.
0522 *
0523 * @param pos the offset position, measured in bytes from the
0524 * beginning of the file, at which to set the file
0525 * pointer.
0526 * @exception IOException if <code>pos</code> is less than
0527 * <code>0</code> or if an I/O error occurs.
0528 */
0529 public native void seek(long pos) throws IOException;
0530
0531 /**
0532 * Returns the length of this file.
0533 *
0534 * @return the length of this file, measured in bytes.
0535 * @exception IOException if an I/O error occurs.
0536 */
0537 public native long length() throws IOException;
0538
0539 /**
0540 * Sets the length of this file.
0541 *
0542 * <p> If the present length of the file as returned by the
0543 * <code>length</code> method is greater than the <code>newLength</code>
0544 * argument then the file will be truncated. In this case, if the file
0545 * offset as returned by the <code>getFilePointer</code> method is greater
0546 * than <code>newLength</code> then after this method returns the offset
0547 * will be equal to <code>newLength</code>.
0548 *
0549 * <p> If the present length of the file as returned by the
0550 * <code>length</code> method is smaller than the <code>newLength</code>
0551 * argument then the file will be extended. In this case, the contents of
0552 * the extended portion of the file are not defined.
0553 *
0554 * @param newLength The desired length of the file
0555 * @exception IOException If an I/O error occurs
0556 * @since 1.2
0557 */
0558 public native void setLength(long newLength) throws IOException;
0559
0560 /**
0561 * Closes this random access file stream and releases any system
0562 * resources associated with the stream. A closed random access
0563 * file cannot perform input or output operations and cannot be
0564 * reopened.
0565 *
0566 * <p> If this file has an associated channel then the channel is closed
0567 * as well.
0568 *
0569 * @exception IOException if an I/O error occurs.
0570 *
0571 * @revised 1.4
0572 * @spec JSR-51
0573 */
0574 public void close() throws IOException {
0575 synchronized (closeLock) {
0576 if (closed) {
0577 return;
0578 }
0579 closed = true;
0580 }
0581 if (channel != null) {
0582 /*
0583 * Decrement FD use count associated with the channel. The FD use
0584 * count is incremented whenever a new channel is obtained from
0585 * this stream.
0586 */
0587 fd.decrementAndGetUseCount();
0588 channel.close();
0589 }
0590
0591 /*
0592 * Decrement FD use count associated with this stream.
0593 * The count got incremented by FileDescriptor during its construction.
0594 */
0595 fd.decrementAndGetUseCount();
0596 close0();
0597 }
0598
0599 //
0600 // Some "reading/writing Java data types" methods stolen from
0601 // DataInputStream and DataOutputStream.
0602 //
0603
0604 /**
0605 * Reads a <code>boolean</code> from this file. This method reads a
0606 * single byte from the file, starting at the current file pointer.
0607 * A value of <code>0</code> represents
0608 * <code>false</code>. Any other value represents <code>true</code>.
0609 * This method blocks until the byte is read, the end of the stream
0610 * is detected, or an exception is thrown.
0611 *
0612 * @return the <code>boolean</code> value read.
0613 * @exception EOFException if this file has reached the end.
0614 * @exception IOException if an I/O error occurs.
0615 */
0616 public final boolean readBoolean() throws IOException {
0617 int ch = this .read();
0618 if (ch < 0)
0619 throw new EOFException();
0620 return (ch != 0);
0621 }
0622
0623 /**
0624 * Reads a signed eight-bit value from this file. This method reads a
0625 * byte from the file, starting from the current file pointer.
0626 * If the byte read is <code>b</code>, where
0627 * <code>0 <= b <= 255</code>,
0628 * then the result is:
0629 * <blockquote><pre>
0630 * (byte)(b)
0631 * </pre></blockquote>
0632 * <p>
0633 * This method blocks until the byte is read, the end of the stream
0634 * is detected, or an exception is thrown.
0635 *
0636 * @return the next byte of this file as a signed eight-bit
0637 * <code>byte</code>.
0638 * @exception EOFException if this file has reached the end.
0639 * @exception IOException if an I/O error occurs.
0640 */
0641 public final byte readByte() throws IOException {
0642 int ch = this .read();
0643 if (ch < 0)
0644 throw new EOFException();
0645 return (byte) (ch);
0646 }
0647
0648 /**
0649 * Reads an unsigned eight-bit number from this file. This method reads
0650 * a byte from this file, starting at the current file pointer,
0651 * and returns that byte.
0652 * <p>
0653 * This method blocks until the byte is read, the end of the stream
0654 * is detected, or an exception is thrown.
0655 *
0656 * @return the next byte of this file, interpreted as an unsigned
0657 * eight-bit number.
0658 * @exception EOFException if this file has reached the end.
0659 * @exception IOException if an I/O error occurs.
0660 */
0661 public final int readUnsignedByte() throws IOException {
0662 int ch = this .read();
0663 if (ch < 0)
0664 throw new EOFException();
0665 return ch;
0666 }
0667
0668 /**
0669 * Reads a signed 16-bit number from this file. The method reads two
0670 * bytes from this file, starting at the current file pointer.
0671 * If the two bytes read, in order, are
0672 * <code>b1</code> and <code>b2</code>, where each of the two values is
0673 * between <code>0</code> and <code>255</code>, inclusive, then the
0674 * result is equal to:
0675 * <blockquote><pre>
0676 * (short)((b1 << 8) | b2)
0677 * </pre></blockquote>
0678 * <p>
0679 * This method blocks until the two bytes are read, the end of the
0680 * stream is detected, or an exception is thrown.
0681 *
0682 * @return the next two bytes of this file, interpreted as a signed
0683 * 16-bit number.
0684 * @exception EOFException if this file reaches the end before reading
0685 * two bytes.
0686 * @exception IOException if an I/O error occurs.
0687 */
0688 public final short readShort() throws IOException {
0689 int ch1 = this .read();
0690 int ch2 = this .read();
0691 if ((ch1 | ch2) < 0)
0692 throw new EOFException();
0693 return (short) ((ch1 << 8) + (ch2 << 0));
0694 }
0695
0696 /**
0697 * Reads an unsigned 16-bit number from this file. This method reads
0698 * two bytes from the file, starting at the current file pointer.
0699 * If the bytes read, in order, are
0700 * <code>b1</code> and <code>b2</code>, where
0701 * <code>0 <= b1, b2 <= 255</code>,
0702 * then the result is equal to:
0703 * <blockquote><pre>
0704 * (b1 << 8) | b2
0705 * </pre></blockquote>
0706 * <p>
0707 * This method blocks until the two bytes are read, the end of the
0708 * stream is detected, or an exception is thrown.
0709 *
0710 * @return the next two bytes of this file, interpreted as an unsigned
0711 * 16-bit integer.
0712 * @exception EOFException if this file reaches the end before reading
0713 * two bytes.
0714 * @exception IOException if an I/O error occurs.
0715 */
0716 public final int readUnsignedShort() throws IOException {
0717 int ch1 = this .read();
0718 int ch2 = this .read();
0719 if ((ch1 | ch2) < 0)
0720 throw new EOFException();
0721 return (ch1 << 8) + (ch2 << 0);
0722 }
0723
0724 /**
0725 * Reads a character from this file. This method reads two
0726 * bytes from the file, starting at the current file pointer.
0727 * If the bytes read, in order, are
0728 * <code>b1</code> and <code>b2</code>, where
0729 * <code>0 <= b1, b2 <= 255</code>,
0730 * then the result is equal to:
0731 * <blockquote><pre>
0732 * (char)((b1 << 8) | b2)
0733 * </pre></blockquote>
0734 * <p>
0735 * This method blocks until the two bytes are read, the end of the
0736 * stream is detected, or an exception is thrown.
0737 *
0738 * @return the next two bytes of this file, interpreted as a
0739 * <code>char</code>.
0740 * @exception EOFException if this file reaches the end before reading
0741 * two bytes.
0742 * @exception IOException if an I/O error occurs.
0743 */
0744 public final char readChar() throws IOException {
0745 int ch1 = this .read();
0746 int ch2 = this .read();
0747 if ((ch1 | ch2) < 0)
0748 throw new EOFException();
0749 return (char) ((ch1 << 8) + (ch2 << 0));
0750 }
0751
0752 /**
0753 * Reads a signed 32-bit integer from this file. This method reads 4
0754 * bytes from the file, starting at the current file pointer.
0755 * If the bytes read, in order, are <code>b1</code>,
0756 * <code>b2</code>, <code>b3</code>, and <code>b4</code>, where
0757 * <code>0 <= b1, b2, b3, b4 <= 255</code>,
0758 * then the result is equal to:
0759 * <blockquote><pre>
0760 * (b1 << 24) | (b2 << 16) + (b3 << 8) + b4
0761 * </pre></blockquote>
0762 * <p>
0763 * This method blocks until the four bytes are read, the end of the
0764 * stream is detected, or an exception is thrown.
0765 *
0766 * @return the next four bytes of this file, interpreted as an
0767 * <code>int</code>.
0768 * @exception EOFException if this file reaches the end before reading
0769 * four bytes.
0770 * @exception IOException if an I/O error occurs.
0771 */
0772 public final int readInt() throws IOException {
0773 int ch1 = this .read();
0774 int ch2 = this .read();
0775 int ch3 = this .read();
0776 int ch4 = this .read();
0777 if ((ch1 | ch2 | ch3 | ch4) < 0)
0778 throw new EOFException();
0779 return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
0780 }
0781
0782 /**
0783 * Reads a signed 64-bit integer from this file. This method reads eight
0784 * bytes from the file, starting at the current file pointer.
0785 * If the bytes read, in order, are
0786 * <code>b1</code>, <code>b2</code>, <code>b3</code>,
0787 * <code>b4</code>, <code>b5</code>, <code>b6</code>,
0788 * <code>b7</code>, and <code>b8,</code> where:
0789 * <blockquote><pre>
0790 * 0 <= b1, b2, b3, b4, b5, b6, b7, b8 <=255,
0791 * </pre></blockquote>
0792 * <p>
0793 * then the result is equal to:
0794 * <p><blockquote><pre>
0795 * ((long)b1 << 56) + ((long)b2 << 48)
0796 * + ((long)b3 << 40) + ((long)b4 << 32)
0797 * + ((long)b5 << 24) + ((long)b6 << 16)
0798 * + ((long)b7 << 8) + b8
0799 * </pre></blockquote>
0800 * <p>
0801 * This method blocks until the eight bytes are read, the end of the
0802 * stream is detected, or an exception is thrown.
0803 *
0804 * @return the next eight bytes of this file, interpreted as a
0805 * <code>long</code>.
0806 * @exception EOFException if this file reaches the end before reading
0807 * eight bytes.
0808 * @exception IOException if an I/O error occurs.
0809 */
0810 public final long readLong() throws IOException {
0811 return ((long) (readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
0812 }
0813
0814 /**
0815 * Reads a <code>float</code> from this file. This method reads an
0816 * <code>int</code> value, starting at the current file pointer,
0817 * as if by the <code>readInt</code> method
0818 * and then converts that <code>int</code> to a <code>float</code>
0819 * using the <code>intBitsToFloat</code> method in class
0820 * <code>Float</code>.
0821 * <p>
0822 * This method blocks until the four bytes are read, the end of the
0823 * stream is detected, or an exception is thrown.
0824 *
0825 * @return the next four bytes of this file, interpreted as a
0826 * <code>float</code>.
0827 * @exception EOFException if this file reaches the end before reading
0828 * four bytes.
0829 * @exception IOException if an I/O error occurs.
0830 * @see java.io.RandomAccessFile#readInt()
0831 * @see java.lang.Float#intBitsToFloat(int)
0832 */
0833 public final float readFloat() throws IOException {
0834 return Float.intBitsToFloat(readInt());
0835 }
0836
0837 /**
0838 * Reads a <code>double</code> from this file. This method reads a
0839 * <code>long</code> value, starting at the current file pointer,
0840 * as if by the <code>readLong</code> method
0841 * and then converts that <code>long</code> to a <code>double</code>
0842 * using the <code>longBitsToDouble</code> method in
0843 * class <code>Double</code>.
0844 * <p>
0845 * This method blocks until the eight bytes are read, the end of the
0846 * stream is detected, or an exception is thrown.
0847 *
0848 * @return the next eight bytes of this file, interpreted as a
0849 * <code>double</code>.
0850 * @exception EOFException if this file reaches the end before reading
0851 * eight bytes.
0852 * @exception IOException if an I/O error occurs.
0853 * @see java.io.RandomAccessFile#readLong()
0854 * @see java.lang.Double#longBitsToDouble(long)
0855 */
0856 public final double readDouble() throws IOException {
0857 return Double.longBitsToDouble(readLong());
0858 }
0859
0860 /**
0861 * Reads the next line of text from this file. This method successively
0862 * reads bytes from the file, starting at the current file pointer,
0863 * until it reaches a line terminator or the end
0864 * of the file. Each byte is converted into a character by taking the
0865 * byte's value for the lower eight bits of the character and setting the
0866 * high eight bits of the character to zero. This method does not,
0867 * therefore, support the full Unicode character set.
0868 *
0869 * <p> A line of text is terminated by a carriage-return character
0870 * (<code>'\r'</code>), a newline character (<code>'\n'</code>), a
0871 * carriage-return character immediately followed by a newline character,
0872 * or the end of the file. Line-terminating characters are discarded and
0873 * are not included as part of the string returned.
0874 *
0875 * <p> This method blocks until a newline character is read, a carriage
0876 * return and the byte following it are read (to see if it is a newline),
0877 * the end of the file is reached, or an exception is thrown.
0878 *
0879 * @return the next line of text from this file, or null if end
0880 * of file is encountered before even one byte is read.
0881 * @exception IOException if an I/O error occurs.
0882 */
0883
0884 public final String readLine() throws IOException {
0885 StringBuffer input = new StringBuffer();
0886 int c = -1;
0887 boolean eol = false;
0888
0889 while (!eol) {
0890 switch (c = read()) {
0891 case -1:
0892 case '\n':
0893 eol = true;
0894 break;
0895 case '\r':
0896 eol = true;
0897 long cur = getFilePointer();
0898 if ((read()) != '\n') {
0899 seek(cur);
0900 }
0901 break;
0902 default:
0903 input.append((char) c);
0904 break;
0905 }
0906 }
0907
0908 if ((c == -1) && (input.length() == 0)) {
0909 return null;
0910 }
0911 return input.toString();
0912 }
0913
0914 /**
0915 * Reads in a string from this file. The string has been encoded
0916 * using a
0917 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
0918 * format.
0919 * <p>
0920 * The first two bytes are read, starting from the current file
0921 * pointer, as if by
0922 * <code>readUnsignedShort</code>. This value gives the number of
0923 * following bytes that are in the encoded string, not
0924 * the length of the resulting string. The following bytes are then
0925 * interpreted as bytes encoding characters in the modified UTF-8 format
0926 * and are converted into characters.
0927 * <p>
0928 * This method blocks until all the bytes are read, the end of the
0929 * stream is detected, or an exception is thrown.
0930 *
0931 * @return a Unicode string.
0932 * @exception EOFException if this file reaches the end before
0933 * reading all the bytes.
0934 * @exception IOException if an I/O error occurs.
0935 * @exception UTFDataFormatException if the bytes do not represent
0936 * valid modified UTF-8 encoding of a Unicode string.
0937 * @see java.io.RandomAccessFile#readUnsignedShort()
0938 */
0939 public final String readUTF() throws IOException {
0940 return DataInputStream.readUTF(this );
0941 }
0942
0943 /**
0944 * Writes a <code>boolean</code> to the file as a one-byte value. The
0945 * value <code>true</code> is written out as the value
0946 * <code>(byte)1</code>; the value <code>false</code> is written out
0947 * as the value <code>(byte)0</code>. The write starts at
0948 * the current position of the file pointer.
0949 *
0950 * @param v a <code>boolean</code> value to be written.
0951 * @exception IOException if an I/O error occurs.
0952 */
0953 public final void writeBoolean(boolean v) throws IOException {
0954 write(v ? 1 : 0);
0955 //written++;
0956 }
0957
0958 /**
0959 * Writes a <code>byte</code> to the file as a one-byte value. The
0960 * write starts at the current position of the file pointer.
0961 *
0962 * @param v a <code>byte</code> value to be written.
0963 * @exception IOException if an I/O error occurs.
0964 */
0965 public final void writeByte(int v) throws IOException {
0966 write(v);
0967 //written++;
0968 }
0969
0970 /**
0971 * Writes a <code>short</code> to the file as two bytes, high byte first.
0972 * The write starts at the current position of the file pointer.
0973 *
0974 * @param v a <code>short</code> to be written.
0975 * @exception IOException if an I/O error occurs.
0976 */
0977 public final void writeShort(int v) throws IOException {
0978 write((v >>> 8) & 0xFF);
0979 write((v >>> 0) & 0xFF);
0980 //written += 2;
0981 }
0982
0983 /**
0984 * Writes a <code>char</code> to the file as a two-byte value, high
0985 * byte first. The write starts at the current position of the
0986 * file pointer.
0987 *
0988 * @param v a <code>char</code> value to be written.
0989 * @exception IOException if an I/O error occurs.
0990 */
0991 public final void writeChar(int v) throws IOException {
0992 write((v >>> 8) & 0xFF);
0993 write((v >>> 0) & 0xFF);
0994 //written += 2;
0995 }
0996
0997 /**
0998 * Writes an <code>int</code> to the file as four bytes, high byte first.
0999 * The write starts at the current position of the file pointer.
1000 *
1001 * @param v an <code>int</code> to be written.
1002 * @exception IOException if an I/O error occurs.
1003 */
1004 public final void writeInt(int v) throws IOException {
1005 write((v >>> 24) & 0xFF);
1006 write((v >>> 16) & 0xFF);
1007 write((v >>> 8) & 0xFF);
1008 write((v >>> 0) & 0xFF);
1009 //written += 4;
1010 }
1011
1012 /**
1013 * Writes a <code>long</code> to the file as eight bytes, high byte first.
1014 * The write starts at the current position of the file pointer.
1015 *
1016 * @param v a <code>long</code> to be written.
1017 * @exception IOException if an I/O error occurs.
1018 */
1019 public final void writeLong(long v) throws IOException {
1020 write((int) (v >>> 56) & 0xFF);
1021 write((int) (v >>> 48) & 0xFF);
1022 write((int) (v >>> 40) & 0xFF);
1023 write((int) (v >>> 32) & 0xFF);
1024 write((int) (v >>> 24) & 0xFF);
1025 write((int) (v >>> 16) & 0xFF);
1026 write((int) (v >>> 8) & 0xFF);
1027 write((int) (v >>> 0) & 0xFF);
1028 //written += 8;
1029 }
1030
1031 /**
1032 * Converts the float argument to an <code>int</code> using the
1033 * <code>floatToIntBits</code> method in class <code>Float</code>,
1034 * and then writes that <code>int</code> value to the file as a
1035 * four-byte quantity, high byte first. The write starts at the
1036 * current position of the file pointer.
1037 *
1038 * @param v a <code>float</code> value to be written.
1039 * @exception IOException if an I/O error occurs.
1040 * @see java.lang.Float#floatToIntBits(float)
1041 */
1042 public final void writeFloat(float v) throws IOException {
1043 writeInt(Float.floatToIntBits(v));
1044 }
1045
1046 /**
1047 * Converts the double argument to a <code>long</code> using the
1048 * <code>doubleToLongBits</code> method in class <code>Double</code>,
1049 * and then writes that <code>long</code> value to the file as an
1050 * eight-byte quantity, high byte first. The write starts at the current
1051 * position of the file pointer.
1052 *
1053 * @param v a <code>double</code> value to be written.
1054 * @exception IOException if an I/O error occurs.
1055 * @see java.lang.Double#doubleToLongBits(double)
1056 */
1057 public final void writeDouble(double v) throws IOException {
1058 writeLong(Double.doubleToLongBits(v));
1059 }
1060
1061 /**
1062 * Writes the string to the file as a sequence of bytes. Each
1063 * character in the string is written out, in sequence, by discarding
1064 * its high eight bits. The write starts at the current position of
1065 * the file pointer.
1066 *
1067 * @param s a string of bytes to be written.
1068 * @exception IOException if an I/O error occurs.
1069 */
1070 public final void writeBytes(String s) throws IOException {
1071 int len = s.length();
1072 byte[] b = new byte[len];
1073 s.getBytes(0, len, b, 0);
1074 writeBytes(b, 0, len);
1075 }
1076
1077 /**
1078 * Writes a string to the file as a sequence of characters. Each
1079 * character is written to the data output stream as if by the
1080 * <code>writeChar</code> method. The write starts at the current
1081 * position of the file pointer.
1082 *
1083 * @param s a <code>String</code> value to be written.
1084 * @exception IOException if an I/O error occurs.
1085 * @see java.io.RandomAccessFile#writeChar(int)
1086 */
1087 public final void writeChars(String s) throws IOException {
1088 int clen = s.length();
1089 int blen = 2 * clen;
1090 byte[] b = new byte[blen];
1091 char[] c = new char[clen];
1092 s.getChars(0, clen, c, 0);
1093 for (int i = 0, j = 0; i < clen; i++) {
1094 b[j++] = (byte) (c[i] >>> 8);
1095 b[j++] = (byte) (c[i] >>> 0);
1096 }
1097 writeBytes(b, 0, blen);
1098 }
1099
1100 /**
1101 * Writes a string to the file using
1102 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
1103 * encoding in a machine-independent manner.
1104 * <p>
1105 * First, two bytes are written to the file, starting at the
1106 * current file pointer, as if by the
1107 * <code>writeShort</code> method giving the number of bytes to
1108 * follow. This value is the number of bytes actually written out,
1109 * not the length of the string. Following the length, each character
1110 * of the string is output, in sequence, using the modified UTF-8 encoding
1111 * for each character.
1112 *
1113 * @param str a string to be written.
1114 * @exception IOException if an I/O error occurs.
1115 */
1116 public final void writeUTF(String str) throws IOException {
1117 DataOutputStream.writeUTF(str, this );
1118 }
1119
1120 private static native void initIDs();
1121
1122 private native void close0() throws IOException;
1123
1124 static {
1125 initIDs();
1126 }
1127 }
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