Package org.ka2ddo.yaac.io

Class MultiBufferedRandomAccessFile

java.lang.Object

org.ka2ddo.yaac.io.MultiBufferedRandomAccessFile

All Implemented Interfaces:

Closeable, DataInput, DataOutput, AutoCloseable

public final class MultiBufferedRandomAccessFile
extends Object
implements DataInput, DataOutput, Closeable

This class provides a cached, buffered variant of RandomAccessFile, so that sequential reads from a starting point can be done with minimal JNI calls and actual kernel calls. It also supports multiple buffers for reading chunks of data that are significantly not sequential.

Author:

Andrew Pavlin, KA2DDO

Constructor Summary

Constructors

Constructor	Description
MultiBufferedRandomAccessFile(File file, int bufSize, int maxBuffers)	Create a read-only random access file with the specified maximum number of buffers of the specified size.
MultiBufferedRandomAccessFile(File file, int bufSize, int maxBuffers, boolean isWriteable)	Create a read-only or read-write random access file with the specified maximum number of buffers of the specified size.
MultiBufferedRandomAccessFile(File file, int bufSize, int maxBuffers, boolean isWriteable, boolean flushUnloadedBuffers)	Create a read-only or read-write random access file with the specified maximum number of buffers of the specified size.
MultiBufferedRandomAccessFile(File file, int bufSize, int maxBuffers, boolean isWriteable, boolean flushUnloadedBuffers, boolean trackReloadedBlocks)	Create a read-only or read-write random access file with the specified maximum number of buffers of the specified size.
MultiBufferedRandomAccessFile(File file, int bufSize, int maxBuffers, boolean isWriteable, byte[] prefillPattern)	Create a read-only or read-write random access file with the specified maximum number of buffers of the specified size.
MultiBufferedRandomAccessFile(File file, int bufSize, int maxBuffers, boolean isWriteable, byte[] prefillPattern, boolean trackReloadedBlocks)	Create a read-only or read-write random access file with the specified maximum number of buffers of the specified size.

Method Summary

Modifier and Type	Method	Description
void	clearCache()	Clear the cache buffers.
void	close()	Closes this file and releases any system resources associated with the buffering.
void	flush()	Flush all "dirty" (modified) buffers.
long	getFilePointer()	Returns the current offset in this file.
int	getNumConsecutiveHits()	Get number of consecutive times a read matched data already in the buffers or a write overwrote data already in the buffers.
int	getNumFlushes()	Get the number of times write-modified buffers had to be flushed to disk.
long	getNumHits()	Get number of times a read matched data already in the buffers or a write overwrote data already in the buffers.
long	getNumMisses()	Get the number of times a read or write required loading a buffer from disk.
int	getNumReReads()	Get the number of times a block that had already been read into a buffer was read again.
RandomAccessFile	getRandomAccessFile()	Get the RandomAccessFile underlying this MultiBufferedRandomAccessFile.
int	read()	Reads the next byte in the file at the current seek position.
boolean	readBoolean()	See the general contract of the readBoolean method of DataInput.
byte	readByte()	See the general contract of the readByte method of DataInput.
char	readChar()	See the general contract of the readChar method of DataInput.
double	readDouble()	See the general contract of the readDouble method of DataInput.
float	readFloat()	See the general contract of the readFloat method of DataInput.
void	readFully(byte[] b)	See the general contract of the readFully method of DataInput.
void	readFully(byte[] b, int off, int len)	See the general contract of the readFully method of DataInput.
int	readInt()	See the general contract of the readInt method of DataInput.
int	readIntAt(long seekPos)	Bytes for this operation are read from the contained file.
String	readLine()	See the general contract of the readLine method of DataInput.
long	readLong()	See the general contract of the readLong method of DataInput.
int	readNextInt()	This is similar to readInt(), but the caller must guarantee that no seek(long) occurred between the last call to readInt() or readNextInt() and this one.
short	readShort()	See the general contract of the readShort method of DataInput.
int	readUnsignedByte()	See the general contract of the readUnsignedByte method of DataInput.
int	readUnsignedShort()	See the general contract of the readUnsignedShort method of DataInput.
String	readUTF()	See the general contract of the readUTF method of DataInput.
void	resetOldPages()	If being used, clear the history of already-accessed pages.
void	resetStatistics()	Reset the statistics counters that are reported by the toString() method.
void	seek(long seekPos)	Sets the file-pointer offset, measured from the beginning of this file, at which the next read occurs.
int	skipBytes(int n)	See the general contract of the skipBytes method of DataInput.
String	toString()	Returns a string representation of the object.
void	write(byte[] b)	Writes to the output stream all the bytes in array b.
void	write(byte[] b, int off, int len)	Writes len bytes from array b, in order, to the output stream.
void	write(int b)	Writes to the output stream the eight low-order bits of the argument b.
void	write2Int(int v1, int v2)	Writes 2 int values, each of which is comprised of four bytes, to the output stream.
void	write2Int(long seekPos, int v1, int v2)	Sets the file-pointer offset, measured from the beginning of this file, at which the next read occurs.
void	writeBoolean(boolean v)	Writes a boolean value to this output stream.
void	writeByte(int v)	Writes to the output stream the eight low- order bits of the argument v.
void	writeBytes(String s)	Writes a string to the output stream.
void	writeChar(int v)	Writes a char value, which is comprised of two bytes, to the output stream.
void	writeChars(String s)	Writes every character in the string s, to the output stream, in order, two bytes per character.
void	writeDouble(double v)	Writes a double value, which is comprised of eight bytes, to the output stream.
void	writeFloat(float v)	Writes a float value, which is comprised of four bytes, to the output stream.
void	writeInt(int v)	Writes an int value, which is comprised of four bytes, to the output stream.
void	writeLong(long v)	Writes a long value, which is comprised of eight bytes, to the output stream.
void	writeShort(int v)	Writes two bytes to the output stream to represent the value of the argument.
void	writeUTF(String s)	Writes two bytes of length information to the output stream, followed by the modified UTF-8 representation of every character in the string s.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Details

MultiBufferedRandomAccessFile

public MultiBufferedRandomAccessFile(File file,
 int bufSize,
 int maxBuffers)
                              throws IOException

Create a read-only random access file with the specified maximum number of buffers of the specified size.

Parameters:

file - File pointing at the disk file to read

bufSize - size of each buffer in bytes (must be a power of 2)

maxBuffers - maximum number of buffers to use

Throws:

IOException - if file cannot be opened for read-only access

MultiBufferedRandomAccessFile

public MultiBufferedRandomAccessFile(File file,
 int bufSize,
 int maxBuffers,
 boolean isWriteable)
                              throws IOException

Create a read-only or read-write random access file with the specified maximum number of buffers of the specified size.

Parameters:

file - File pointing at the disk file to read

bufSize - size of each buffer in bytes (must be a power of 2)

maxBuffers - maximum number of buffers to use

isWriteable - boolean true if this file can be written to

Throws:

IOException - if file cannot be opened for the requested access

MultiBufferedRandomAccessFile

public MultiBufferedRandomAccessFile(File file,
 int bufSize,
 int maxBuffers,
 boolean isWriteable,
 boolean flushUnloadedBuffers)
                              throws IOException

Create a read-only or read-write random access file with the specified maximum number of buffers of the specified size.

Parameters:

file - File pointing at the disk file to read

bufSize - size of each buffer in bytes (must be a power of 2)

maxBuffers - maximum number of buffers to use

isWriteable - boolean true if this file can be written to

flushUnloadedBuffers - specify whether capable systems should flush released buffers from kernel filesystem cache to reduce cache overgrowth

Throws:

IOException - if file cannot be opened for the requested access

MultiBufferedRandomAccessFile

public MultiBufferedRandomAccessFile(File file,
 int bufSize,
 int maxBuffers,
 boolean isWriteable,
 boolean flushUnloadedBuffers,
 boolean trackReloadedBlocks)
                              throws IOException

Create a read-only or read-write random access file with the specified maximum number of buffers of the specified size.

Parameters:

file - File pointing at the disk file to read

bufSize - size of each buffer in bytes (must be a power of 2)

maxBuffers - maximum number of buffers to use

isWriteable - boolean true if this file can be written to

flushUnloadedBuffers - specify whether capable systems should flush released buffers from kernel filesystem cache to reduce cache overgrowth

trackReloadedBlocks - boolean true if rereads of blocks should be tracked, false if not

Throws:

IOException - if file cannot be opened for the requested access

MultiBufferedRandomAccessFile

public MultiBufferedRandomAccessFile(File file,
 int bufSize,
 int maxBuffers,
 boolean isWriteable,
 byte[] prefillPattern)
                              throws IOException

Create a read-only or read-write random access file with the specified maximum number of buffers of the specified size.

Parameters:

file - File pointing at the disk file to read

bufSize - size of each buffer in bytes (must be a power of 2)

maxBuffers - maximum number of buffers to use

isWriteable - boolean true if this file can be written to

prefillPattern - byte array to iteratively write to a new buffer as a fill pattern

Throws:

IOException - if file cannot be opened for the requested access

MultiBufferedRandomAccessFile

public MultiBufferedRandomAccessFile(File file,
 int bufSize,
 int maxBuffers,
 boolean isWriteable,
 byte[] prefillPattern,
 boolean trackReloadedBlocks)
                              throws IOException

Create a read-only or read-write random access file with the specified maximum number of buffers of the specified size.

Parameters:

file - File pointing at the disk file to read

bufSize - size of each buffer in bytes (must be a power of 2)

maxBuffers - maximum number of buffers to use

isWriteable - boolean true if this file can be written to

prefillPattern - byte array to iteratively write to a new buffer as a fill pattern

trackReloadedBlocks - boolean true if rereads of blocks should be tracked, false if not

Throws:

IOException - if file cannot be opened for the requested access

Method Details

read

public int read()
         throws IOException

Reads the next byte in the file at the current seek position.

Returns:

the next byte of data

Throws:

EOFException - if attempt to read past the end of file

IOException - if this input stream has been closed by invoking its close() method, or an I/O error occurs.

See Also:

• seek(long)

readBoolean

public boolean readBoolean()
                    throws IOException

See the general contract of the readBoolean method of DataInput.

Bytes for this operation are read from the contained file.

Specified by:

readBoolean in interface DataInput

Returns:

the boolean value read.

Throws:

EOFException - if this input stream has reached the end.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

readByte

public byte readByte()
              throws IOException

See the general contract of the readByte method of DataInput.

Bytes for this operation are read from the contained file.

Specified by:

readByte in interface DataInput

Returns:

the next byte of this input stream as a signed 8-bit byte.

Throws:

EOFException - if this input stream has reached the end.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

readChar

public char readChar()
              throws IOException

See the general contract of the readChar method of DataInput.

Bytes for this operation are read from the contained input stream.

Specified by:

readChar in interface DataInput

Returns:

the next two bytes of this input stream, interpreted as a char.

Throws:

EOFException - if this input stream reaches the end before reading two bytes.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

readDouble

public double readDouble()
                  throws IOException

See the general contract of the readDouble method of DataInput.

Bytes for this operation are read from the contained file.

Specified by:

readDouble in interface DataInput

Returns:

the next eight bytes of this input stream, interpreted as a double.

Throws:

EOFException - if this input stream reaches the end before reading eight bytes.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

See Also:

• DataInputStream.readLong()
• Double.longBitsToDouble(long)

readFloat

public float readFloat()
                throws IOException

See the general contract of the readFloat method of DataInput.

Bytes for this operation are read from the contained file.

Specified by:

readFloat in interface DataInput

Returns:

the next four bytes of this input stream, interpreted as a float.

Throws:

EOFException - if this input stream reaches the end before reading four bytes.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

See Also:

• DataInputStream.readInt()
• Float.intBitsToFloat(int)

readFully

public void readFully(byte[] b)
               throws IOException

See the general contract of the readFully method of DataInput.

Bytes for this operation are read from the contained file.

Specified by:

readFully in interface DataInput

Parameters:

b - the buffer into which the data is read.

Throws:

EOFException - if this input stream reaches the end before reading all the bytes.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

readFully

public void readFully(byte[] b,
 int off,
 int len)
               throws IOException

See the general contract of the readFully method of DataInput.

Bytes for this operation are read from the contained file.

Specified by:

readFully in interface DataInput

Parameters:

b - the buffer into which the data is read.

off - the start offset of the data.

len - the number of bytes to read.

Throws:

EOFException - if this input stream reaches the end before reading all the bytes.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

readInt

public int readInt()
            throws IOException

See the general contract of the readInt method of DataInput.

Bytes for this operation are read from the contained file.

Specified by:

readInt in interface DataInput

Returns:

the next four bytes of this input stream, interpreted as an int.

Throws:

EOFException - if this input stream reaches the end before reading four bytes.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

readLine

public String readLine()
                throws IOException

See the general contract of the readLine method of DataInput.

Bytes for this operation are read from the contained file. Note that this method only supports extended 8-bit ASCII; it does not support UTF-8 or other locale-specific character sets.

Specified by:

readLine in interface DataInput

Returns:

the next line of text from this input stream.

Throws:

IOException - if an I/O error occurs.

readLong

public long readLong()
              throws IOException

See the general contract of the readLong method of DataInput.

Bytes for this operation are read from the contained file.

Specified by:

readLong in interface DataInput

Returns:

the next eight bytes of this input stream, interpreted as a long.

Throws:

EOFException - if this input stream reaches the end before reading eight bytes.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

readShort

public short readShort()
                throws IOException

See the general contract of the readShort method of DataInput.

Bytes for this operation are read from the contained file.

Specified by:

readShort in interface DataInput

Returns:

the next two bytes of this input stream, interpreted as a signed 16-bit number.

Throws:

EOFException - if this input stream reaches the end before reading two bytes.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

readUnsignedByte

public int readUnsignedByte()
                     throws IOException

See the general contract of the readUnsignedByte method of DataInput.

Bytes for this operation are read from the contained file.

Specified by:

readUnsignedByte in interface DataInput

Returns:

the next byte of this input stream, interpreted as an unsigned 8-bit number.

Throws:

EOFException - if this input stream has reached the end.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

readUnsignedShort

public int readUnsignedShort()
                      throws IOException

See the general contract of the readUnsignedShort method of DataInput.

Bytes for this operation are read from the contained file.

Specified by:

readUnsignedShort in interface DataInput

Returns:

the next two bytes of this input stream, interpreted as an unsigned 16-bit integer.

Throws:

EOFException - if this input stream reaches the end before reading two bytes.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

readUTF

public String readUTF()
               throws IOException

See the general contract of the readUTF method of DataInput.

Bytes for this operation are read from the contained file.

Specified by:

readUTF in interface DataInput

Returns:

a Unicode string.

Throws:

EOFException - if this input stream reaches the end before reading all the bytes.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

UTFDataFormatException - if the bytes do not represent a valid modified UTF-8 encoding of a string.

skipBytes

public int skipBytes(int n)

See the general contract of the skipBytes method of DataInput.

No actual bytes are read; the current file seek position pointer is merely updated in preparation for later I/O.

Specified by:

skipBytes in interface DataInput

Parameters:

n - the number of bytes to be skipped.

Returns:

the actual number of bytes skipped.

seek

public void seek(long seekPos)

Sets the file-pointer offset, measured from the beginning of this file, at which the next read 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.

Parameters:

seekPos - the offset position, measured in bytes from the beginning of the file, at which to set the file pointer.

readIntAt

public int readIntAt(long seekPos)
              throws IOException

Bytes for this operation are read from the contained file.

Parameters:

seekPos - the offset position, measured in bytes from the beginning of the file, at which to set the file pointer.

Returns:

the next four bytes of this input stream, interpreted as an int.

Throws:

EOFException - if this input stream reaches the end before reading four bytes.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

getFilePointer

public long getFilePointer()

Returns the current offset in this file.

Returns:

the offset from the beginning of the file, in bytes, at which the next read or write occurs.

close

public void close()
           throws IOException

Closes this file and releases any system resources associated with the buffering. Once the file has been closed, further read(), available(), or skipBytes() invocations will throw an IOException. Closing a previously closed stream has no effect.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException - if an I/O error occurs.

toString

public String toString()

Returns a string representation of the object.

Overrides:

toString in class Object

Returns:

a string representation of the object.

resetStatistics

public void resetStatistics()

Reset the statistics counters that are reported by the toString() method.

See Also:

• toString()

resetOldPages

public void resetOldPages()

If being used, clear the history of already-accessed pages.

getNumHits

public long getNumHits()

Get number of times a read matched data already in the buffers or a write overwrote data already in the buffers.

Returns:

long hit count since last statistics reset

See Also:

• resetStatistics()

getNumConsecutiveHits

public int getNumConsecutiveHits()

Get number of consecutive times a read matched data already in the buffers or a write overwrote data already in the buffers.

Returns:

int maximum consecutive hit count since last statistics reset

See Also:

• resetStatistics()

getNumMisses

public long getNumMisses()

Get the number of times a read or write required loading a buffer from disk.

Returns:

long miss count since last statistics reset

See Also:

• resetStatistics()

getNumFlushes

public int getNumFlushes()

Get the number of times write-modified buffers had to be flushed to disk.

Returns:

int flush count since last statistics reset

See Also:

• resetStatistics()

getNumReReads

public int getNumReReads()

Get the number of times a block that had already been read into a buffer was read again.

Returns:

number of re-reads

readNextInt

public int readNextInt()
                throws IOException

This is similar to readInt(), but the caller must guarantee that no seek(long) occurred between the last call to readInt() or readNextInt() and this one.

Returns:

the next four bytes of this input stream, interpreted as an int.

Throws:

EOFException - if this input stream reaches the end before reading four bytes.

IOException - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.

See Also:

• readInt()

clearCache

public void clearCache()

Clear the cache buffers. Useful if the file is changed through another file descriptor such that this caching RandomAccessFile's caches might be stale. Note that any unflushed writes will be lost.

write

public void write(byte[] b)
           throws IOException

Writes to the output stream all the bytes in array b. If b is null, a NullPointerException is thrown. If b.length is zero, then no bytes are written. Otherwise, the byte b[0] is written first, then b[1], and so on; the last byte written is b[b.length-1].

Specified by:

write in interface DataOutput

Parameters:

b - the data.

Throws:

IOException - if an I/O error occurs.

write

public void write(int b)
           throws IOException

Writes to the output stream the eight low-order bits of the argument b. The 24 high-order bits of b are ignored.

Specified by:

write in interface DataOutput

Parameters:

b - the byte to be written.

Throws:

IOException - if an I/O error occurs.

write

public void write(byte[] b,
 int off,
 int len)
           throws IOException

Writes len bytes from array b, in order, to the output stream. If b is null, a NullPointerException is thrown. If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException is thrown. If len is zero, then no bytes are written. Otherwise, the byte b[off] is written first, then b[off+1], and so on; the last byte written is b[off+len-1].

Specified by:

write in interface DataOutput

Parameters:

b - the data.

off - the start offset in the data.

len - the number of bytes to write.

Throws:

IOException - if an I/O error occurs.

writeBoolean

public void writeBoolean(boolean v)
                  throws IOException

Writes a boolean value to this output stream. If the argument v is true, the value (byte)1 is written; if v is false, the value (byte)0 is written. The byte written by this method may be read by the readBoolean method of interface DataInput, which will then return a boolean equal to v.

Specified by:

writeBoolean in interface DataOutput

Parameters:

v - the boolean to be written.

Throws:

IOException - if an I/O error occurs.

writeByte

public void writeByte(int v)
               throws IOException

Writes to the output stream the eight low- order bits of the argument v. The 24 high-order bits of v are ignored. (This means that writeByte does exactly the same thing as write for an integer argument.) The byte written by this method may be read by the readByte method of interface DataInput, which will then return a byte equal to (byte)v.

Specified by:

writeByte in interface DataOutput

Parameters:

v - the byte value to be written.

Throws:

IOException - if an I/O error occurs.

writeShort

public void writeShort(int v)
                throws IOException

Writes two bytes to the output stream to represent the value of the argument. The byte values to be written, in the order shown, are:

 (byte)(0xff & (v >> 8))
 (byte)(0xff & v)
  

The bytes written by this method may be read by the readShort method of interface DataInput , which will then return a short equal to (short)v.

Specified by:

writeShort in interface DataOutput

Parameters:

v - the short value to be written.

Throws:

IOException - if an I/O error occurs.

writeChar

public void writeChar(int v)
               throws IOException

Writes a char value, which is comprised of two bytes, to the output stream. The byte values to be written, in the order shown, are:

 (byte)(0xff & (v >> 8))
 (byte)(0xff & v)
 

The bytes written by this method may be read by the readChar method of interface DataInput , which will then return a char equal to (char)v.

Specified by:

writeChar in interface DataOutput

Parameters:

v - the char value to be written.

Throws:

IOException - if an I/O error occurs.

writeInt

public void writeInt(int v)
              throws IOException

Writes an int value, which is comprised of four bytes, to the output stream. The byte values to be written, in the order shown, are:

 (byte)(0xff & (v >> 24))
 (byte)(0xff & (v >> 16))
 (byte)(0xff & (v >>    8))
 (byte)(0xff & v)
 

The bytes written by this method may be read by the readInt method of interface DataInput , which will then return an int equal to v.

Specified by:

writeInt in interface DataOutput

Parameters:

v - the int value to be written.

Throws:

IOException - if an I/O error occurs.

write2Int

public void write2Int(int v1,
 int v2)
               throws IOException

Writes 2 int values, each of which is comprised of four bytes, to the output stream. The byte values to be written, in the order shown, are:

 (byte)(0xff & (v >> 24))
 (byte)(0xff & (v >> 16))
 (byte)(0xff & (v >>    8))
 (byte)(0xff & v)
 

The bytes written by this method may be read by the readInt method of interface DataInput , which will then return an int equal to v.

Parameters:

v1 - the first int value to be written.

v2 - the first int value to be written.

Throws:

IOException - if an I/O error occurs.

write2Int

public void write2Int(long seekPos,
 int v1,
 int v2)
               throws IOException

Sets the file-pointer offset, measured from the beginning of this file, at which the next read 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. Then writes 2 int values, each of which is comprised of four bytes, to the output stream. The byte values to be written, in the order shown, are:

 (byte)(0xff & (v >> 24))
 (byte)(0xff & (v >> 16))
 (byte)(0xff & (v >>    8))
 (byte)(0xff & v)
 

The bytes written by this method may be read by the readInt method of interface DataInput , which will then return an int equal to v1 or v2.

Parameters:

seekPos - the offset position, measured in bytes from the beginning of the file, at which to set the file pointer.

v1 - the first int value to be written.

v2 - the first int value to be written.

Throws:

IOException - if an I/O error occurs.

writeLong

public void writeLong(long v)
               throws IOException

Writes a long value, which is comprised of eight bytes, to the output stream. The byte values to be written, in the order shown, are:

 (byte)(0xff & (v >> 56))
 (byte)(0xff & (v >> 48))
 (byte)(0xff & (v >> 40))
 (byte)(0xff & (v >> 32))
 (byte)(0xff & (v >> 24))
 (byte)(0xff & (v >> 16))
 (byte)(0xff & (v >>  8))
 (byte)(0xff & v)
 

The bytes written by this method may be read by the readLong method of interface DataInput , which will then return a long equal to v.

Specified by:

writeLong in interface DataOutput

Parameters:

v - the long value to be written.

Throws:

IOException - if an I/O error occurs.

writeFloat

public void writeFloat(float v)
                throws IOException

Writes a float value, which is comprised of four bytes, to the output stream. It does this as if it first converts this float value to an int in exactly the manner of the Float.floatToIntBits method and then writes the int value in exactly the manner of the writeInt method. The bytes written by this method may be read by the readFloat method of interface DataInput, which will then return a float equal to v.

Specified by:

writeFloat in interface DataOutput

Parameters:

v - the float value to be written.

Throws:

IOException - if an I/O error occurs.

writeDouble

public void writeDouble(double v)
                 throws IOException

Writes a double value, which is comprised of eight bytes, to the output stream. It does this as if it first converts this double value to a long in exactly the manner of the Double.doubleToLongBits method and then writes the long value in exactly the manner of the writeLong method. The bytes written by this method may be read by the readDouble method of interface DataInput, which will then return a double equal to v.

Specified by:

writeDouble in interface DataOutput

Parameters:

v - the double value to be written.

Throws:

IOException - if an I/O error occurs.

writeBytes

public void writeBytes(String s)
                throws IOException

Writes a string to the output stream. For every character in the string s, taken in order, one byte is written to the output stream. If s is null, a NullPointerException is thrown.

If s.length is zero, then no bytes are written. Otherwise, the character s[0] is written first, then s[1], and so on; the last character written is s[s.length-1]. For each character, one byte is written, the low-order byte, in exactly the manner of the writeByte method . The high-order eight bits of each character in the string are ignored.

Specified by:

writeBytes in interface DataOutput

Parameters:

s - the string of bytes to be written.

Throws:

IOException - if an I/O error occurs.

writeChars

public void writeChars(String s)
                throws IOException

Writes every character in the string s, to the output stream, in order, two bytes per character. If s is null, a NullPointerException is thrown. If s.length is zero, then no characters are written. Otherwise, the character s[0] is written first, then s[1], and so on; the last character written is s[s.length-1]. For each character, two bytes are actually written, high-order byte first, in exactly the manner of the writeChar method.

Specified by:

writeChars in interface DataOutput

Parameters:

s - the string value to be written.

Throws:

IOException - if an I/O error occurs.

writeUTF

public void writeUTF(String s)
              throws IOException

Writes two bytes of length information to the output stream, followed by the modified UTF-8 representation of every character in the string s. If s is null, a NullPointerException is thrown. Each character in the string s is converted to a group of one, two, or three bytes, depending on the value of the character.

If a character c is in the range \u0001 through \u007f, it is represented by one byte:

(byte)c 

If a character c is \u0000 or is in the range \u0080 through \u07ff, then it is represented by two bytes, to be written in the order shown:

 (byte)(0xc0 | (0x1f & (c >> 6)))
 (byte)(0x80 | (0x3f & c))
 

If a character c is in the range \u0800 through uffff, then it is represented by three bytes, to be written in the order shown:

 (byte)(0xe0 | (0x0f & (c >> 12)))
 (byte)(0x80 | (0x3f & (c >>  6)))
 (byte)(0x80 | (0x3f & c))
 

First, the total number of bytes needed to represent all the characters of s is calculated. If this number is larger than 65535, then a UTFDataFormatException is thrown. Otherwise, this length is written to the output stream in exactly the manner of the writeShort method; after this, the one-, two-, or three-byte representation of each character in the string s is written.

The bytes written by this method may be read by the readUTF method of interface DataInput , which will then return a String equal to s.

Specified by:

writeUTF in interface DataOutput

Parameters:

s - the string value to be written.

Throws:

IOException - if an I/O error occurs.

flush

public void flush()
           throws IOException

Flush all "dirty" (modified) buffers.

Throws:

IOException - if dirty buffers can't be written to disk

See Also:

• getNumFlushes()

getRandomAccessFile

public RandomAccessFile getRandomAccessFile()

Get the RandomAccessFile underlying this MultiBufferedRandomAccessFile.

Returns:

RandomAccessFile if file is still open, null otherwise

See Also:

• OSAdapter.releaseOldPages(RandomAccessFile, long, long)