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android / platform / libcore.git / 51b1b6997fd3f980076b8081f7f1165ccc2a4008 / . / ojluni / src / main / java / java / io / RandomAccessFile.java
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/*
* Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.io;
import java.nio.channels.FileChannel;
import sun.nio.ch.FileChannelImpl;
import sun.misc.IoTrace;
/**
* Instances of this class support both reading and writing to a
* random access file. A random access file behaves like a large
* array of bytes stored in the file system. There is a kind of cursor,
* or index into the implied array, called the <em>file pointer</em>;
* input operations read bytes starting at the file pointer and advance
* the file pointer past the bytes read. If the random access file is
* created in read/write mode, then output operations are also available;
* output operations write bytes starting at the file pointer and advance
* the file pointer past the bytes written. Output operations that write
* past the current end of the implied array cause the array to be
* extended. The file pointer can be read by the
* <code>getFilePointer</code> method and set by the <code>seek</code>
* method.
* <p>
* It is generally true of all the reading routines in this class that
* if end-of-file is reached before the desired number of bytes has been
* read, an <code>EOFException</code> (which is a kind of
* <code>IOException</code>) is thrown. If any byte cannot be read for
* any reason other than end-of-file, an <code>IOException</code> other
* than <code>EOFException</code> is thrown. In particular, an
* <code>IOException</code> may be thrown if the stream has been closed.
*
* @author unascribed
* @since JDK1.0
*/
public class RandomAccessFile implements DataOutput, DataInput, Closeable {
private FileDescriptor fd;
private FileChannel channel = null;
private boolean rw;
/* The path of the referenced file */
private final String path;
private Object closeLock = new Object();
private volatile boolean closed = false;
private static final int O_RDONLY = 1;
private static final int O_RDWR = 2;
private static final int O_SYNC = 4;
private static final int O_DSYNC = 8;
/**
* Creates a random access file stream to read from, and optionally
* to write to, a file with the specified name. A new
* {@link FileDescriptor} object is created to represent the
* connection to the file.
*
* <p> The <tt>mode</tt> argument specifies the access mode with which the
* file is to be opened. The permitted values and their meanings are as
* specified for the <a
* href="#mode"><tt>RandomAccessFile(File,String)</tt></a> constructor.
*
* <p>
* If there is a security manager, its <code>checkRead</code> method
* is called with the <code>name</code> argument
* as its argument to see if read access to the file is allowed.
* If the mode allows writing, the security manager's
* <code>checkWrite</code> method
* is also called with the <code>name</code> argument
* as its argument to see if write access to the file is allowed.
*
* @param name the system-dependent filename
* @param mode the access <a href="#mode">mode</a>
* @exception IllegalArgumentException if the mode argument is not equal
* to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
* <tt>"rwd"</tt>
* @exception FileNotFoundException
* if the mode is <tt>"r"</tt> but the given string does not
* denote an existing regular file, or if the mode begins with
* <tt>"rw"</tt> but the given string does not denote an
* existing, writable regular file and a new regular file of
* that name cannot be created, or if some other error occurs
* while opening or creating the file
* @exception SecurityException if a security manager exists and its
* <code>checkRead</code> method denies read access to the file
* or the mode is "rw" and the security manager's
* <code>checkWrite</code> method denies write access to the file
* @see java.lang.SecurityException
* @see java.lang.SecurityManager#checkRead(java.lang.String)
* @see java.lang.SecurityManager#checkWrite(java.lang.String)
* @revised 1.4
* @spec JSR-51
*/
public RandomAccessFile(String name, String mode)
throws FileNotFoundException
{
this(name != null ? new File(name) : null, mode);
}
/**
* Creates a random access file stream to read from, and optionally to
* write to, the file specified by the {@link File} argument. A new {@link
* FileDescriptor} object is created to represent this file connection.
*
* <a name="mode"><p> The <tt>mode</tt> argument specifies the access mode
* in which the file is to be opened. The permitted values and their
* meanings are:
*
* <blockquote><table summary="Access mode permitted values and meanings">
* <tr><th><p align="left">Value</p></th><th><p align="left">Meaning</p></th></tr>
* <tr><td valign="top"><tt>"r"</tt></td>
* <td> Open for reading only. Invoking any of the <tt>write</tt>
* methods of the resulting object will cause an {@link
* java.io.IOException} to be thrown. </td></tr>
* <tr><td valign="top"><tt>"rw"</tt></td>
* <td> Open for reading and writing. If the file does not already
* exist then an attempt will be made to create it. </td></tr>
* <tr><td valign="top"><tt>"rws"</tt></td>
* <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
* require that every update to the file's content or metadata be
* written synchronously to the underlying storage device. </td></tr>
* <tr><td valign="top"><tt>"rwd"&nbsp;&nbsp;</tt></td>
* <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
* require that every update to the file's content be written
* synchronously to the underlying storage device. </td></tr>
* </table></blockquote>
*
* The <tt>"rws"</tt> and <tt>"rwd"</tt> modes work much like the {@link
* java.nio.channels.FileChannel#force(boolean) force(boolean)} method of
* the {@link java.nio.channels.FileChannel} class, passing arguments of
* <tt>true</tt> and <tt>false</tt>, respectively, except that they always
* apply to every I/O operation and are therefore often more efficient. If
* the file resides on a local storage device then when an invocation of a
* method of this class returns it is guaranteed that all changes made to
* the file by that invocation will have been written to that device. This
* is useful for ensuring that critical information is not lost in the
* event of a system crash. If the file does not reside on a local device
* then no such guarantee is made.
*
* <p> The <tt>"rwd"</tt> mode can be used to reduce the number of I/O
* operations performed. Using <tt>"rwd"</tt> only requires updates to the
* file's content to be written to storage; using <tt>"rws"</tt> requires
* updates to both the file's content and its metadata to be written, which
* generally requires at least one more low-level I/O operation.
*
* <p> If there is a security manager, its <code>checkRead</code> method is
* called with the pathname of the <code>file</code> argument as its
* argument to see if read access to the file is allowed. If the mode
* allows writing, the security manager's <code>checkWrite</code> method is
* also called with the path argument to see if write access to the file is
* allowed.
*
* @param file the file object
* @param mode the access mode, as described
* <a href="#mode">above</a>
* @exception IllegalArgumentException if the mode argument is not equal
* to one of <tt>"r"</tt>, <tt>"rw"</tt>, <tt>"rws"</tt>, or
* <tt>"rwd"</tt>
* @exception FileNotFoundException
* if the mode is <tt>"r"</tt> but the given file object does
* not denote an existing regular file, or if the mode begins
* with <tt>"rw"</tt> but the given file object does not denote
* an existing, writable regular file and a new regular file of
* that name cannot be created, or if some other error occurs
* while opening or creating the file
* @exception SecurityException if a security manager exists and its
* <code>checkRead</code> method denies read access to the file
* or the mode is "rw" and the security manager's
* <code>checkWrite</code> method denies write access to the file
* @see java.lang.SecurityManager#checkRead(java.lang.String)
* @see java.lang.SecurityManager#checkWrite(java.lang.String)
* @see java.nio.channels.FileChannel#force(boolean)
* @revised 1.4
* @spec JSR-51
*/
public RandomAccessFile(File file, String mode)
throws FileNotFoundException
{
String name = (file != null ? file.getPath() : null);
int imode = -1;
if (mode.equals("r"))
imode = O_RDONLY;
else if (mode.startsWith("rw")) {
imode = O_RDWR;
rw = true;
if (mode.length() > 2) {
if (mode.equals("rws"))
imode |= O_SYNC;
else if (mode.equals("rwd"))
imode |= O_DSYNC;
else
imode = -1;
}
}
if (imode < 0)
throw new IllegalArgumentException("Illegal mode \"" + mode
+ "\" must be one of "
+ "\"r\", \"rw\", \"rws\","
+ " or \"rwd\"");
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkRead(name);
if (rw) {
security.checkWrite(name);
}
}
if (name == null) {
throw new NullPointerException();
}
if (file.isInvalid()) {
throw new FileNotFoundException("Invalid file path");
}
fd = new FileDescriptor();
fd.incrementAndGetUseCount();
this.path = name;
open(name, imode);
}
/**
* Returns the opaque file descriptor object associated with this
* stream. </p>
*
* @return the file descriptor object associated with this stream.
* @exception IOException if an I/O error occurs.
* @see java.io.FileDescriptor
*/
public final FileDescriptor getFD() throws IOException {
if (fd != null) return fd;
throw new IOException();
}
/**
* Returns the unique {@link java.nio.channels.FileChannel FileChannel}
* object associated with this file.
*
* <p> The {@link java.nio.channels.FileChannel#position()
* </code>position<code>} of the returned channel will always be equal to
* this object's file-pointer offset as returned by the {@link
* #getFilePointer getFilePointer} method. Changing this object's
* file-pointer offset, whether explicitly or by reading or writing bytes,
* will change the position of the channel, and vice versa. Changing the
* file's length via this object will change the length seen via the file
* channel, and vice versa.
*
* @return the file channel associated with this file
*
* @since 1.4
* @spec JSR-51
*/
public final FileChannel getChannel() {
synchronized (this) {
if (channel == null) {
channel = FileChannelImpl.open(fd, path, true, rw, this);
/*
* FileDescriptor could be shared by FileInputStream or
* FileOutputStream.
* Ensure that FD is GC'ed only when all the streams/channels
* are done using it.
* Increment fd's use count. Invoking the channel's close()
* method will result in decrementing the use count set for
* the channel.
*/
fd.incrementAndGetUseCount();
}
return channel;
}
}
/**
* Opens a file and returns the file descriptor. The file is
* opened in read-write mode if the O_RDWR bit in <code>mode</code>
* is true, else the file is opened as read-only.
* If the <code>name</code> refers to a directory, an IOException
* is thrown.
*
* @param name the name of the file
* @param mode the mode flags, a combination of the O_ constants
* defined above
*/
private native void open(String name, int mode)
throws FileNotFoundException;
// 'Read' primitives
/**
* Reads a byte of data from this file. The byte is returned as an
* integer in the range 0 to 255 (<code>0x00-0x0ff</code>). This
* method blocks if no input is yet available.
* <p>
* Although <code>RandomAccessFile</code> is not a subclass of
* <code>InputStream</code>, this method behaves in exactly the same
* way as the {@link InputStream#read()} method of
* <code>InputStream</code>.
*
* @return the next byte of data, or <code>-1</code> if the end of the
* file has been reached.
* @exception IOException if an I/O error occurs. Not thrown if
* end-of-file has been reached.
*/
public int read() throws IOException {
Object traceContext = IoTrace.fileReadBegin(path);
int b = 0;
try {
b = read0();
} finally {
IoTrace.fileReadEnd(traceContext, b == -1 ? 0 : 1);
}
return b;
}
private native int read0() throws IOException;
/**
* Reads a sub array as a sequence of bytes.
* @param b the buffer into which the data is read.
* @param off the start offset of the data.
* @param len the number of bytes to read.
* @exception IOException If an I/O error has occurred.
*/
private int readBytes(byte b[], int off, int len) throws IOException {
Object traceContext = IoTrace.fileReadBegin(path);
int bytesRead = 0;
try {
bytesRead = readBytes0(b, off, len);
} finally {
IoTrace.fileReadEnd(traceContext, bytesRead == -1 ? 0 : bytesRead);
}
return bytesRead;
}
private native int readBytes0(byte b[], int off, int len) throws IOException;
/**
* Reads up to <code>len</code> bytes of data from this file into an
* array of bytes. This method blocks until at least one byte of input
* is available.
* <p>
* Although <code>RandomAccessFile</code> is not a subclass of
* <code>InputStream</code>, this method behaves in exactly the
* same way as the {@link InputStream#read(byte[], int, int)} method of
* <code>InputStream</code>.
*
* @param b the buffer into which the data is read.
* @param off the start offset in array <code>b</code>
* at which the data is written.
* @param len the maximum number of bytes read.
* @return the total number of bytes read into the buffer, or
* <code>-1</code> if there is no more data because the end of
* the file has been reached.
* @exception IOException If the first byte cannot be read for any reason
* other than end of file, or if the random access file has been closed, or if
* some other I/O error occurs.
* @exception NullPointerException If <code>b</code> is <code>null</code>.
* @exception IndexOutOfBoundsException If <code>off</code> is negative,
* <code>len</code> is negative, or <code>len</code> is greater than
* <code>b.length - off</code>
*/
public int read(byte b[], int off, int len) throws IOException {
return readBytes(b, off, len);
}
/**
* Reads up to <code>b.length</code> bytes of data from this file
* into an array of bytes. This method blocks until at least one byte
* of input is available.
* <p>
* Although <code>RandomAccessFile</code> is not a subclass of
* <code>InputStream</code>, this method behaves in exactly the
* same way as the {@link InputStream#read(byte[])} method of
* <code>InputStream</code>.
*
* @param b the buffer into which the data is read.
* @return the total number of bytes read into the buffer, or
* <code>-1</code> if there is no more data because the end of
* this file has been reached.
* @exception IOException If the first byte cannot be read for any reason
* other than end of file, or if the random access file has been closed, or if
* some other I/O error occurs.
* @exception NullPointerException If <code>b</code> is <code>null</code>.
*/
public int read(byte b[]) throws IOException {
return readBytes(b, 0, b.length);
}
/**
* Reads <code>b.length</code> bytes from this file into the byte
* array, starting at the current file pointer. This method reads
* repeatedly from the file until the requested number of bytes are
* read. This method blocks until the requested number of bytes are
* read, the end of the stream is detected, or an exception is thrown.
*
* @param b the buffer into which the data is read.
* @exception EOFException if this file reaches the end before reading
* all the bytes.
* @exception IOException if an I/O error occurs.
*/
public final void readFully(byte b[]) throws IOException {
readFully(b, 0, b.length);
}
/**
* Reads exactly <code>len</code> bytes from this file into the byte
* array, starting at the current file pointer. This method reads
* repeatedly from the file until the requested number of bytes are
* read. This method blocks until the requested number of bytes are
* read, the end of the stream is detected, or an exception is thrown.
*
* @param b the buffer into which the data is read.
* @param off the start offset of the data.
* @param len the number of bytes to read.
* @exception EOFException if this file reaches the end before reading
* all the bytes.
* @exception IOException if an I/O error occurs.
*/
public final void readFully(byte b[], int off, int len) throws IOException {
int n = 0;
do {
int count = this.read(b, off + n, len - n);
if (count < 0)
throw new EOFException();
n += count;
} while (n < len);
}
/**
* Attempts to skip over <code>n</code> bytes of input discarding the
* skipped bytes.
* <p>
*
* This method may skip over some smaller number of bytes, possibly zero.
* This may result from any of a number of conditions; reaching end of
* file before <code>n</code> bytes have been skipped is only one
* possibility. This method never throws an <code>EOFException</code>.
* The actual number of bytes skipped is returned. If <code>n</code>
* is negative, no bytes are skipped.
*
* @param n the number of bytes to be skipped.
* @return the actual number of bytes skipped.
* @exception IOException if an I/O error occurs.
*/
public int skipBytes(int n) throws IOException {
long pos;
long len;
long newpos;
if (n <= 0) {
return 0;
}
pos = getFilePointer();
len = length();
newpos = pos + n;
if (newpos > len) {
newpos = len;
}
seek(newpos);
/* return the actual number of bytes skipped */
return (int) (newpos - pos);
}
// 'Write' primitives
/**
* Writes the specified byte to this file. The write starts at
* the current file pointer.
*
* @param b the <code>byte</code> to be written.
* @exception IOException if an I/O error occurs.
*/
public void write(int b) throws IOException {
Object traceContext = IoTrace.fileWriteBegin(path);
int bytesWritten = 0;
try {
write0(b);
bytesWritten = 1;
} finally {
IoTrace.fileWriteEnd(traceContext, bytesWritten);
}
}
private native void write0(int b) throws IOException;
/**
* Writes a sub array as a sequence of bytes.
* @param b the data to be written
* @param off the start offset in the data
* @param len the number of bytes that are written
* @exception IOException If an I/O error has occurred.
*/
private void writeBytes(byte b[], int off, int len) throws IOException {
Object traceContext = IoTrace.fileWriteBegin(path);
int bytesWritten = 0;
try {
writeBytes0(b, off, len);
bytesWritten = len;
} finally {
IoTrace.fileWriteEnd(traceContext, bytesWritten);
}
}
private native void writeBytes0(byte b[], int off, int len) throws IOException;
/**
* Writes <code>b.length</code> bytes from the specified byte array
* to this file, starting at the current file pointer.
*
* @param b the data.
* @exception IOException if an I/O error occurs.
*/
public void write(byte b[]) throws IOException {
writeBytes(b, 0, b.length);
}
/**
* Writes <code>len</code> bytes from the specified byte array
* starting at offset <code>off</code> to this file.
*
* @param b the data.
* @param off the start offset in the data.
* @param len the number of bytes to write.
* @exception IOException if an I/O error occurs.
*/
public void write(byte b[], int off, int len) throws IOException {
writeBytes(b, off, len);
}
// 'Random access' stuff
/**
* Returns the current offset in this file.
*
* @return the offset from the beginning of the file, in bytes,
* at which the next read or write occurs.
* @exception IOException if an I/O error occurs.
*/
public native long getFilePointer() throws IOException;
/**
* Sets the file-pointer offset, measured from the beginning of this
* file, at which the next read or write occurs. The offset may be
* set beyond the end of the file. Setting the offset beyond the end
* of the file does not change the file length. The file length will
* change only by writing after the offset has been set beyond the end
* of the file.
*
* @param pos the offset position, measured in bytes from the
* beginning of the file, at which to set the file
* pointer.
* @exception IOException if <code>pos</code> is less than
* <code>0</code> or if an I/O error occurs.
*/
public native void seek(long pos) throws IOException;
/**
* Returns the length of this file.
*
* @return the length of this file, measured in bytes.
* @exception IOException if an I/O error occurs.
*/
public native long length() throws IOException;
/**
* Sets the length of this file.
*
* <p> If the present length of the file as returned by the
* <code>length</code> method is greater than the <code>newLength</code>
* argument then the file will be truncated. In this case, if the file
* offset as returned by the <code>getFilePointer</code> method is greater
* than <code>newLength</code> then after this method returns the offset
* will be equal to <code>newLength</code>.
*
* <p> If the present length of the file as returned by the
* <code>length</code> method is smaller than the <code>newLength</code>
* argument then the file will be extended. In this case, the contents of
* the extended portion of the file are not defined.
*
* @param newLength The desired length of the file
* @exception IOException If an I/O error occurs
* @since 1.2
*/
public native void setLength(long newLength) throws IOException;
/**
* Closes this random access file stream and releases any system
* resources associated with the stream. A closed random access
* file cannot perform input or output operations and cannot be
* reopened.
*
* <p> If this file has an associated channel then the channel is closed
* as well.
*
* @exception IOException if an I/O error occurs.
*
* @revised 1.4
* @spec JSR-51
*/
public void close() throws IOException {
synchronized (closeLock) {
if (closed) {
return;
}
closed = true;
}
if (channel != null) {
/*
* Decrement FD use count associated with the channel. The FD use
* count is incremented whenever a new channel is obtained from
* this stream.
*/
fd.decrementAndGetUseCount();
channel.close();
}
/*
* Decrement FD use count associated with this stream.
* The count got incremented by FileDescriptor during its construction.
*/
fd.decrementAndGetUseCount();
close0();
}
//
// Some "reading/writing Java data types" methods stolen from
// DataInputStream and DataOutputStream.
//
/**
* Reads a <code>boolean</code> from this file. This method reads a
* single byte from the file, starting at the current file pointer.
* A value of <code>0</code> represents
* <code>false</code>. Any other value represents <code>true</code>.
* This method blocks until the byte is read, the end of the stream
* is detected, or an exception is thrown.
*
* @return the <code>boolean</code> value read.
* @exception EOFException if this file has reached the end.
* @exception IOException if an I/O error occurs.
*/
public final boolean readBoolean() throws IOException {
int ch = this.read();
if (ch < 0)
throw new EOFException();
return (ch != 0);
}
/**
* Reads a signed eight-bit value from this file. This method reads a
* byte from the file, starting from the current file pointer.
* If the byte read is <code>b</code>, where
* <code>0&nbsp;&lt;=&nbsp;b&nbsp;&lt;=&nbsp;255</code>,
* then the result is:
* <blockquote><pre>
* (byte)(b)
* </pre></blockquote>
* <p>
* This method blocks until the byte is read, the end of the stream
* is detected, or an exception is thrown.
*
* @return the next byte of this file as a signed eight-bit
* <code>byte</code>.
* @exception EOFException if this file has reached the end.
* @exception IOException if an I/O error occurs.
*/
public final byte readByte() throws IOException {
int ch = this.read();
if (ch < 0)
throw new EOFException();
return (byte)(ch);
}
/**
* Reads an unsigned eight-bit number from this file. This method reads
* a byte from this file, starting at the current file pointer,
* and returns that byte.
* <p>
* This method blocks until the byte is read, the end of the stream
* is detected, or an exception is thrown.
*
* @return the next byte of this file, interpreted as an unsigned
* eight-bit number.
* @exception EOFException if this file has reached the end.
* @exception IOException if an I/O error occurs.
*/
public final int readUnsignedByte() throws IOException {
int ch = this.read();
if (ch < 0)
throw new EOFException();
return ch;
}
/**
* Reads a signed 16-bit number from this file. The method reads two
* bytes from this file, starting at the current file pointer.
* If the two bytes read, in order, are
* <code>b1</code> and <code>b2</code>, where each of the two values is
* between <code>0</code> and <code>255</code>, inclusive, then the
* result is equal to:
* <blockquote><pre>
* (short)((b1 &lt;&lt; 8) | b2)
* </pre></blockquote>
* <p>
* This method blocks until the two bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next two bytes of this file, interpreted as a signed
* 16-bit number.
* @exception EOFException if this file reaches the end before reading
* two bytes.
* @exception IOException if an I/O error occurs.
*/
public final short readShort() throws IOException {
int ch1 = this.read();
int ch2 = this.read();
if ((ch1 | ch2) < 0)
throw new EOFException();
return (short)((ch1 << 8) + (ch2 << 0));
}
/**
* Reads an unsigned 16-bit number from this file. This method reads
* two bytes from the file, starting at the current file pointer.
* If the bytes read, in order, are
* <code>b1</code> and <code>b2</code>, where
* <code>0&nbsp;&lt;=&nbsp;b1, b2&nbsp;&lt;=&nbsp;255</code>,
* then the result is equal to:
* <blockquote><pre>
* (b1 &lt;&lt; 8) | b2
* </pre></blockquote>
* <p>
* This method blocks until the two bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next two bytes of this file, interpreted as an unsigned
* 16-bit integer.
* @exception EOFException if this file reaches the end before reading
* two bytes.
* @exception IOException if an I/O error occurs.
*/
public final int readUnsignedShort() throws IOException {
int ch1 = this.read();
int ch2 = this.read();
if ((ch1 | ch2) < 0)
throw new EOFException();
return (ch1 << 8) + (ch2 << 0);
}
/**
* Reads a character from this file. This method reads two
* bytes from the file, starting at the current file pointer.
* If the bytes read, in order, are
* <code>b1</code> and <code>b2</code>, where
* <code>0&nbsp;&lt;=&nbsp;b1,&nbsp;b2&nbsp;&lt;=&nbsp;255</code>,
* then the result is equal to:
* <blockquote><pre>
* (char)((b1 &lt;&lt; 8) | b2)
* </pre></blockquote>
* <p>
* This method blocks until the two bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next two bytes of this file, interpreted as a
* <code>char</code>.
* @exception EOFException if this file reaches the end before reading
* two bytes.
* @exception IOException if an I/O error occurs.
*/
public final char readChar() throws IOException {
int ch1 = this.read();
int ch2 = this.read();
if ((ch1 | ch2) < 0)
throw new EOFException();
return (char)((ch1 << 8) + (ch2 << 0));
}
/**
* Reads a signed 32-bit integer from this file. This method reads 4
* bytes from the file, starting at the current file pointer.
* If the bytes read, in order, are <code>b1</code>,
* <code>b2</code>, <code>b3</code>, and <code>b4</code>, where
* <code>0&nbsp;&lt;=&nbsp;b1, b2, b3, b4&nbsp;&lt;=&nbsp;255</code>,
* then the result is equal to:
* <blockquote><pre>
* (b1 &lt;&lt; 24) | (b2 &lt;&lt; 16) + (b3 &lt;&lt; 8) + b4
* </pre></blockquote>
* <p>
* This method blocks until the four bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next four bytes of this file, interpreted as an
* <code>int</code>.
* @exception EOFException if this file reaches the end before reading
* four bytes.
* @exception IOException if an I/O error occurs.
*/
public final int readInt() throws IOException {
int ch1 = this.read();
int ch2 = this.read();
int ch3 = this.read();
int ch4 = this.read();
if ((ch1 | ch2 | ch3 | ch4) < 0)
throw new EOFException();
return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
}
/**
* Reads a signed 64-bit integer from this file. This method reads eight
* bytes from the file, starting at the current file pointer.
* If the bytes read, in order, are
* <code>b1</code>, <code>b2</code>, <code>b3</code>,
* <code>b4</code>, <code>b5</code>, <code>b6</code>,
* <code>b7</code>, and <code>b8,</code> where:
* <blockquote><pre>
* 0 &lt;= b1, b2, b3, b4, b5, b6, b7, b8 &lt;=255,
* </pre></blockquote>
* <p>
* then the result is equal to:
* <p><blockquote><pre>
* ((long)b1 &lt;&lt; 56) + ((long)b2 &lt;&lt; 48)
* + ((long)b3 &lt;&lt; 40) + ((long)b4 &lt;&lt; 32)
* + ((long)b5 &lt;&lt; 24) + ((long)b6 &lt;&lt; 16)
* + ((long)b7 &lt;&lt; 8) + b8
* </pre></blockquote>
* <p>
* This method blocks until the eight bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next eight bytes of this file, interpreted as a
* <code>long</code>.
* @exception EOFException if this file reaches the end before reading
* eight bytes.
* @exception IOException if an I/O error occurs.
*/
public final long readLong() throws IOException {
return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
}
/**
* Reads a <code>float</code> from this file. This method reads an
* <code>int</code> value, starting at the current file pointer,
* as if by the <code>readInt</code> method
* and then converts that <code>int</code> to a <code>float</code>
* using the <code>intBitsToFloat</code> method in class
* <code>Float</code>.
* <p>
* This method blocks until the four bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next four bytes of this file, interpreted as a
* <code>float</code>.
* @exception EOFException if this file reaches the end before reading
* four bytes.
* @exception IOException if an I/O error occurs.
* @see java.io.RandomAccessFile#readInt()
* @see java.lang.Float#intBitsToFloat(int)
*/
public final float readFloat() throws IOException {
return Float.intBitsToFloat(readInt());
}
/**
* Reads a <code>double</code> from this file. This method reads a
* <code>long</code> value, starting at the current file pointer,
* as if by the <code>readLong</code> method
* and then converts that <code>long</code> to a <code>double</code>
* using the <code>longBitsToDouble</code> method in
* class <code>Double</code>.
* <p>
* This method blocks until the eight bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next eight bytes of this file, interpreted as a
* <code>double</code>.
* @exception EOFException if this file reaches the end before reading
* eight bytes.
* @exception IOException if an I/O error occurs.
* @see java.io.RandomAccessFile#readLong()
* @see java.lang.Double#longBitsToDouble(long)
*/
public final double readDouble() throws IOException {
return Double.longBitsToDouble(readLong());
}
/**
* Reads the next line of text from this file. This method successively
* reads bytes from the file, starting at the current file pointer,
* until it reaches a line terminator or the end
* of the file. Each byte is converted into a character by taking the
* byte's value for the lower eight bits of the character and setting the
* high eight bits of the character to zero. This method does not,
* therefore, support the full Unicode character set.
*
* <p> A line of text is terminated by a carriage-return character
* (<code>'&#92;r'</code>), a newline character (<code>'&#92;n'</code>), a
* carriage-return character immediately followed by a newline character,
* or the end of the file. Line-terminating characters are discarded and
* are not included as part of the string returned.
*
* <p> This method blocks until a newline character is read, a carriage
* return and the byte following it are read (to see if it is a newline),
* the end of the file is reached, or an exception is thrown.
*
* @return the next line of text from this file, or null if end
* of file is encountered before even one byte is read.
* @exception IOException if an I/O error occurs.
*/
public final String readLine() throws IOException {
StringBuffer input = new StringBuffer();
int c = -1;
boolean eol = false;
while (!eol) {
switch (c = read()) {
case -1:
case '\n':
eol = true;
break;
case '\r':
eol = true;
long cur = getFilePointer();
if ((read()) != '\n') {
seek(cur);
}
break;
default:
input.append((char)c);
break;
}
}
if ((c == -1) && (input.length() == 0)) {
return null;
}
return input.toString();
}
/**
* Reads in a string from this file. The string has been encoded
* using a
* <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
* format.
* <p>
* The first two bytes are read, starting from the current file
* pointer, as if by
* <code>readUnsignedShort</code>. This value gives the number of
* following bytes that are in the encoded string, not
* the length of the resulting string. The following bytes are then
* interpreted as bytes encoding characters in the modified UTF-8 format
* and are converted into characters.
* <p>
* This method blocks until all the bytes are read, the end of the
* stream is detected, or an exception is thrown.
*
* @return a Unicode string.
* @exception EOFException if this file reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
* @exception UTFDataFormatException if the bytes do not represent
* valid modified UTF-8 encoding of a Unicode string.
* @see java.io.RandomAccessFile#readUnsignedShort()
*/
public final String readUTF() throws IOException {
return DataInputStream.readUTF(this);
}
/**
* Writes a <code>boolean</code> to the file as a one-byte value. The
* value <code>true</code> is written out as the value
* <code>(byte)1</code>; the value <code>false</code> is written out
* as the value <code>(byte)0</code>. The write starts at
* the current position of the file pointer.
*
* @param v a <code>boolean</code> value to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeBoolean(boolean v) throws IOException {
write(v ? 1 : 0);
//written++;
}
/**
* Writes a <code>byte</code> to the file as a one-byte value. The
* write starts at the current position of the file pointer.
*
* @param v a <code>byte</code> value to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeByte(int v) throws IOException {
write(v);
//written++;
}
/**
* Writes a <code>short</code> to the file as two bytes, high byte first.
* The write starts at the current position of the file pointer.
*
* @param v a <code>short</code> to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeShort(int v) throws IOException {
write((v >>> 8) & 0xFF);
write((v >>> 0) & 0xFF);
//written += 2;
}
/**
* Writes a <code>char</code> to the file as a two-byte value, high
* byte first. The write starts at the current position of the
* file pointer.
*
* @param v a <code>char</code> value to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeChar(int v) throws IOException {
write((v >>> 8) & 0xFF);
write((v >>> 0) & 0xFF);
//written += 2;
}
/**
* Writes an <code>int</code> to the file as four bytes, high byte first.
* The write starts at the current position of the file pointer.
*
* @param v an <code>int</code> to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeInt(int v) throws IOException {
write((v >>> 24) & 0xFF);
write((v >>> 16) & 0xFF);
write((v >>> 8) & 0xFF);
write((v >>> 0) & 0xFF);
//written += 4;
}
/**
* Writes a <code>long</code> to the file as eight bytes, high byte first.
* The write starts at the current position of the file pointer.
*
* @param v a <code>long</code> to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeLong(long v) throws IOException {
write((int)(v >>> 56) & 0xFF);
write((int)(v >>> 48) & 0xFF);
write((int)(v >>> 40) & 0xFF);
write((int)(v >>> 32) & 0xFF);
write((int)(v >>> 24) & 0xFF);
write((int)(v >>> 16) & 0xFF);
write((int)(v >>> 8) & 0xFF);
write((int)(v >>> 0) & 0xFF);
//written += 8;
}
/**
* Converts the float argument to an <code>int</code> using the
* <code>floatToIntBits</code> method in class <code>Float</code>,
* and then writes that <code>int</code> value to the file as a
* four-byte quantity, high byte first. The write starts at the
* current position of the file pointer.
*
* @param v a <code>float</code> value to be written.
* @exception IOException if an I/O error occurs.
* @see java.lang.Float#floatToIntBits(float)
*/
public final void writeFloat(float v) throws IOException {
writeInt(Float.floatToIntBits(v));
}
/**
* Converts the double argument to a <code>long</code> using the
* <code>doubleToLongBits</code> method in class <code>Double</code>,
* and then writes that <code>long</code> value to the file as an
* eight-byte quantity, high byte first. The write starts at the current
* position of the file pointer.
*
* @param v a <code>double</code> value to be written.
* @exception IOException if an I/O error occurs.
* @see java.lang.Double#doubleToLongBits(double)
*/
public final void writeDouble(double v) throws IOException {
writeLong(Double.doubleToLongBits(v));
}
/**
* Writes the string to the file as a sequence of bytes. Each
* character in the string is written out, in sequence, by discarding
* its high eight bits. The write starts at the current position of
* the file pointer.
*
* @param s a string of bytes to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeBytes(String s) throws IOException {
int len = s.length();
byte[] b = new byte[len];
s.getBytes(0, len, b, 0);
writeBytes(b, 0, len);
}
/**
* Writes a string to the file as a sequence of characters. Each
* character is written to the data output stream as if by the
* <code>writeChar</code> method. The write starts at the current
* position of the file pointer.
*
* @param s a <code>String</code> value to be written.
* @exception IOException if an I/O error occurs.
* @see java.io.RandomAccessFile#writeChar(int)
*/
public final void writeChars(String s) throws IOException {
int clen = s.length();
int blen = 2*clen;
byte[] b = new byte[blen];
char[] c = new char[clen];
s.getChars(0, clen, c, 0);
for (int i = 0, j = 0; i < clen; i++) {
b[j++] = (byte)(c[i] >>> 8);
b[j++] = (byte)(c[i] >>> 0);
}
writeBytes(b, 0, blen);
}
/**
* Writes a string to the file using
* <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
* encoding in a machine-independent manner.
* <p>
* First, two bytes are written to the file, starting at the
* current file pointer, as if by the
* <code>writeShort</code> method giving the number of bytes to
* follow. This value is the number of bytes actually written out,
* not the length of the string. Following the length, each character
* of the string is output, in sequence, using the modified UTF-8 encoding
* for each character.
*
* @param str a string to be written.
* @exception IOException if an I/O error occurs.
*/
public final void writeUTF(String str) throws IOException {
DataOutputStream.writeUTF(str, this);
}
private static native void initIDs();
private native void close0() throws IOException;
static {
initIDs();
}
}