gov.nist.nlpir.misc.io
Class BufferedRandomAccessFile

java.lang.Object
  |
  +--gov.nist.nlpir.misc.io.BufferedRandomAccessFile

public class BufferedRandomAccessFile

extends java.lang.Object

implements java.io.DataInput, java.io.DataOutput

A buffered version of RandomAccessFile.

Instances of this class realise substantial speed increases over RandomAccessFile through the use of buffering. This is a subclass of Object, as it was not possible to subclass RandomAccessFile because many of the methods are final. However, if it is necessary to use BufferedRandomAccessFile and RandomAccessFile interchangeably, both classes implement the DataInput and DataOutput interfaces.

By Alex McManus, based on Sun's source code for RandomAccessFile. Copyright 1997 Centre For Intelligent Systems, Univeristy of Wales, Aberystwyth.

Modified by National Institute of Standards and Technology for use in the Information Retrieval Framework (IRF):

• 99/10/01 line 223: endOfSize unset if staying in the buffer during a seek().
• 99/11/03 line 225: seeking the end of the file doesn't flush the buffer anymore.
• 99/11/03 line 589: when writing data longer than the buffer, this one was becoming unconsistent. It is now fixed: the buffer is empty after such a writing but its associated values allow it to be used.
• 99/11/16 Removed method public final void writeBytes(FastStringBuffer s) to eliminate dependency on FastStringBuffer class

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program 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 for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

Version:

1.0

See Also:

DataInput, DataOutput, RandomAccessFile

Field Summary

protected byte[]	buffer The buffer used to load the data.
(package private) boolean	bufferModified True if the data in the buffer has been modified.
protected long	bufferStart The offset in bytes of the start of the buffer, from the start of the file.
static int	CREATE Create the file rather than overwriting it.
protected long	dataEnd The offset in bytes of the end of the data in the buffer, from the start of the file.
protected int	dataSize The size of the data stored in the buffer, in bytes.
protected static int	defaultBufferSize The default buffer size, in bytes.
protected boolean	endOfFile True if we are at the end of the file.
protected java.io.RandomAccessFile	file The underlying RandomAccessFile.
protected long	filePosition The offset in bytes from the file start, of the next read or write operation.
protected int	mode The access mode of the file.
static int	READ Read from the file.
static int	WRITE Write to the file.

Constructor Summary

BufferedRandomAccessFile(java.lang.String filename, int mode)
Create a new buffered random-access file with a default buffer size.

BufferedRandomAccessFile(java.lang.String filename, int mode, int bufferSize)
Create a new buffered random-access file with a specified buffer size.

Method Summary

static void	benchmark(java.lang.String filename, int bufferSize) Benchmark the performance of the new BufferedRandomAccessFile class.
void	close() Close the file, and release any associated system resources.
void	flush() Copy the contents of the buffer to the disk.
long	getFilePointer() Returns the current position in the file, where the next read or write will occur.
long	getLength() Get the length of the file.
static void	main(java.lang.String[] argv) Test the BufferedRandomAccessFile class.
int	read() Read a byte of data from the file, blocking until data is available.
int	read(byte[] b) Read up to b.length( ) bytes into an array.
int	read(byte[] b, int off, int len) Read up to len bytes into an array, at a specified offset.
boolean	readBoolean() Reads a boolean from this file.
byte	readByte() Reads a signed 8-bit value from this file.
private int	readBytes(byte[] b, int off, int len) Read up to len bytes into an array, at a specified offset.
char	readChar() Reads a Unicode character from this file.
double	readDouble() Reads a double from this file.
float	readFloat() Reads a float from this file.
void	readFully(byte[] b) Reads b.length bytes from this file into the byte array.
void	readFully(byte[] b, int off, int len) Reads exactly len bytes from this file into the byte array.
int	readInt() Reads a signed 32-bit integer from this file.
java.lang.String	readLine() Reads the next line of text from this file.
long	readLong() Reads a signed 64-bit integer from this file.
short	readShort() Reads a signed 16-bit number from this file.
int	readUnsignedByte() Reads an unsigned 8-bit number from this file.
int	readUnsignedShort() Reads an unsigned 16-bit number from this file.
java.lang.String	readUTF() Reads in a string from this file.
void	seek(long pos) Set the position in the file for the next read or write.
int	skipBytes(int n) Skips exactly n bytes of input.
static void	testBlocks(java.lang.String filename) Test the block operations of the BufferedRandomAccessFile class.
static void	testBytes(java.lang.String filename, int bufferSize) Test the byte operations of the BufferedRandomAccessFile class.
java.lang.String	toString() Create a string representation of this object.
void	unread() Unread the last byte read.
void	write(byte[] b) Writes b.length bytes from the specified byte array starting at offset off to this file.
void	write(byte[] b, int off, int len) Writes len bytes from the specified byte array starting at offset off to this file.
void	write(int b) Write a byte to the file.
void	writeBoolean(boolean v) Writes a boolean to the file as a 1-byte value.
void	writeByte(int v) Writes a byte to the file as a 1-byte value.
void	writeBytes(byte[] b, int off, int len) Write len bytes from an array to the file.
void	writeBytes(char[] b, int off, int len) Writes the character array to the file as a sequence of bytes.
void	writeBytes(java.lang.String s) Writes the string to the file as a sequence of bytes.
void	writeChar(int v) Writes a char to the file as a 2-byte value, high byte first.
void	writeChars(java.lang.String s) Writes a string to the file as a sequence of characters.
void	writeDouble(double v) Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the file as an 8-byte quantity, high byte first.
void	writeFloat(float v) Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the file as a 4-byte quantity, high byte first.
void	writeInt(int v) Writes an int to the file as four bytes, high byte first.
void	writeLong(long v) Writes a long to the file as eight bytes, high byte first.
void	writeShort(int v) Writes a short to the file as two bytes, high byte first.
void	writeUTF(java.lang.String str) Writes a string to the file using UTF-8 encoding in a machine-independent manner.

Methods inherited from class java.lang.Object

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

Field Detail

READ

public static final int READ

Read from the file. This is always implied.

WRITE

public static final int WRITE

Write to the file.

CREATE

public static final int CREATE

Create the file rather than overwriting it. This is ignored if mode is not also WRITE.

defaultBufferSize

protected static final int defaultBufferSize

The default buffer size, in bytes.

file

protected java.io.RandomAccessFile file

The underlying RandomAccessFile.

filePosition

protected long filePosition

The offset in bytes from the file start, of the next read or write operation.

buffer

protected byte[] buffer

The buffer used to load the data.

bufferStart

protected long bufferStart

The offset in bytes of the start of the buffer, from the start of the file.

dataEnd

protected long dataEnd

The offset in bytes of the end of the data in the buffer, from the start of the file. This can be calculated from bufferStart + dataSize, but it is cached to speed up the read( ) method.

dataSize

protected int dataSize

The size of the data stored in the buffer, in bytes. This may be less than the size of the buffer.

endOfFile

protected boolean endOfFile

True if we are at the end of the file.

mode

protected int mode

The access mode of the file. This is a logical OR of READ, WRITE and CREATE.

bufferModified

boolean bufferModified

True if the data in the buffer has been modified.

Constructor Detail

BufferedRandomAccessFile

public BufferedRandomAccessFile(java.lang.String filename,
                                int mode)
                         throws java.io.IOException

Create a new buffered random-access file with a default buffer size. Note that the mode CREATE implies WRITE.

Parameters:

filename - the name of the file.

mode - how the file is to be opened. This may be a combination (logical OR) of CREATE, WRITE, and READ.

Throws:

java.io.IOException - if an I/O error occurrs.

java.lang.SecurityException - if a security manager exists, its checkRead method is called with the name argument to see if the application is allowed read access to the file. If the mode argument is WRITE, its checkWrite method also is called with the name argument to see if the application is allowed write access to the file. Either of these may result in a security exception.

BufferedRandomAccessFile

public BufferedRandomAccessFile(java.lang.String filename,
                                int mode,
                                int bufferSize)
                         throws java.io.IOException

Create a new buffered random-access file with a specified buffer size. Note that the mode CREATE implies WRITE, and the READ is always implied.

Parameters:

filename - the name of the file.

mode - how the file is to be opened. This may be a combination (logical OR) of CREATE, WRITE, and READ.

bufferSize - the size of the temporary buffer, in bytes.

Throws:

java.io.IOException - if an I/O error occurrs.

java.lang.SecurityException - if a security manager exists, its checkRead method is called with the name argument to see if the application is allowed read access to the file. If the mode argument is WRITE, its checkWrite method also is called with the name argument to see if the application is allowed write access to the file. Either of these may result in a security exception.

Method Detail

close

public void close()
           throws java.io.IOException

Close the file, and release any associated system resources.

Throws:

java.io.IOException - if an I/O error occurrs.

seek

public final void seek(long pos)
                throws java.io.IOException

Set the position in the file for the next read or write.

Parameters:

pos - the offset (in bytes) from the start of the file.

Throws:

java.io.IOException - if an I/O error occurrs.

getFilePointer

public final long getFilePointer()
                          throws java.io.IOException

Returns the current position in the file, where the next read or write will occur.

Returns:

the offset from the start of the file in bytes.

Throws:

java.io.IOException - if an I/O error occurrs.

getLength

public long getLength()
               throws java.io.IOException

Get the length of the file. The data in the buffer (which may not have been written the disk yet) is taken into account.

Returns:

the length of the file in bytes.

Throws:

java.io.IOException - if an I/O error occurrs.

flush

public void flush()
           throws java.io.IOException

Copy the contents of the buffer to the disk.

Throws:

java.io.IOException - if an I/O error occurrs.

read

public final int read()
               throws java.io.IOException

Read a byte of data from the file, blocking until data is available.

Returns:

the next byte of data, or -1 if the end of the file is reached.

Throws:

java.io.IOException - if an I/O error occurrs.

readBytes

private int readBytes(byte[] b,
                      int off,
                      int len)
               throws java.io.IOException

Read up to len bytes into an array, at a specified offset. This will block until at least one byte has been read.

Parameters:

b - the byte array to receive the bytes.

off - the offset in the array where copying will start.

len - the number of bytes to copy.

Returns:

the actual number of bytes read, or -1 if there is not more data due to the end of the file being reached.

Throws:

java.io.IOException - if an I/O error occurrs.

read

public int read(byte[] b,
                int off,
                int len)
         throws java.io.IOException

Read up to len bytes into an array, at a specified offset. This will block until at least one byte has been read.

Parameters:

b - the byte array to receive the bytes.

off - the offset in the array where copying will start.

len - the number of bytes to copy.

Returns:

the actual number of bytes read, or -1 if there is not more data due to the end of the file being reached.

Throws:

java.io.IOException - if an I/O error occurrs.

read

public int read(byte[] b)
         throws java.io.IOException

Read up to b.length( ) bytes into an array. This will block until at least one byte has been read.

Parameters:

b - the byte array to receive the bytes.

Returns:

the actual number of bytes read, or -1 if there is not more data due to the end of the file being reached.

Throws:

java.io.IOException - if an I/O error occurrs.

readFully

public final void readFully(byte[] b)
                     throws java.io.IOException

Reads b.length bytes from this file into the byte array. This method reads repeatedly from the file until all the bytes are read. This method blocks until all the bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readFully in interface java.io.DataInput

Parameters:

b - the buffer into which the data is read.

Throws:

java.io.EOFException - if this file reaches the end before reading all the bytes.

java.io.IOException - if an I/O error occurs.

readFully

public final void readFully(byte[] b,
                            int off,
                            int len)
                     throws java.io.IOException

Reads exactly len bytes from this file into the byte array. This method reads repeatedly from the file until all the bytes are read. This method blocks until all the bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readFully in interface java.io.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:

java.io.EOFException - if this file reaches the end before reading all the bytes.

java.io.IOException - if an I/O error occurs.

skipBytes

public int skipBytes(int n)
              throws java.io.IOException

Skips exactly n bytes of input. This method blocks until all the bytes are skipped, the end of the stream is detected, or an exception is thrown.

Specified by:

skipBytes in interface java.io.DataInput

Parameters:

n - the number of bytes to be skipped.

Returns:

the number of bytes skipped, which is always n.

Throws:

java.io.EOFException - if this file reaches the end before skipping all the bytes.

java.io.IOException - if an I/O error occurs.

unread

public final void unread()

Unread the last byte read. This method should not be used more than once between reading operations, or strange things might happen.

write

public final void write(int b)
                 throws java.io.IOException

Write a byte to the file. If the file has not been opened for writing, an IOException will be raised only when an attempt is made to write the buffer to the file.

Caveat: the effects of seek( )ing beyond the end of the file are undefined.

Specified by:

write in interface java.io.DataOutput

Throws:

java.io.IOException - if an I/O error occurrs.

writeBytes

public final void writeBytes(byte[] b,
                             int off,
                             int len)
                      throws java.io.IOException

Write len bytes from an array to the file.

Parameters:

b - the array containing the data.

off - the offset in the array to the data.

len - the length of the data.

Throws:

java.io.IOException - if an I/O error occurrs.

write

public void write(byte[] b)
           throws java.io.IOException

Writes b.length bytes from the specified byte array starting at offset off to this file.

Specified by:

write in interface java.io.DataOutput

Parameters:

b - the data.

Throws:

java.io.IOException - if an I/O error occurs.

write

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

Writes len bytes from the specified byte array starting at offset off to this file.

Specified by:

write in interface java.io.DataOutput

Parameters:

b - the data.

off - the start offset in the data.

len - the number of bytes to write.

Throws:

java.io.IOException - if an I/O error occurs.

readBoolean

public final boolean readBoolean()
                          throws java.io.IOException

Reads a boolean from this file. This method reads a single byte from the file. A value of 0 represents false. Any other value represents true. This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.

Specified by:

readBoolean in interface java.io.DataInput

Returns:

the boolean value read.

Throws:

java.io.EOFException - if this file has reached the end.

java.io.IOException - if an I/O error occurs.

readByte

public final byte readByte()
                    throws java.io.IOException

Reads a signed 8-bit value from this file. This method reads a byte from the file. If the byte read is b, where 0 <= b <= 255, then the result is:

(byte)(b)

This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.

Specified by:

readByte in interface java.io.DataInput

Returns:

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

Throws:

java.io.EOFException - if this file has reached the end.

java.io.IOException - if an I/O error occurs.

readUnsignedByte

public final int readUnsignedByte()
                           throws java.io.IOException

Reads an unsigned 8-bit number from this file. This method reads a byte from this file and returns that byte.

This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.

Specified by:

readUnsignedByte in interface java.io.DataInput

Returns:

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

Throws:

java.io.EOFException - if this file has reached the end.

java.io.IOException - if an I/O error occurs.

readShort

public final short readShort()
                      throws java.io.IOException

Reads a signed 16-bit number from this file. The method reads 2 bytes from this file. If the two bytes read, in order, are b1 and b2, where each of the two values is between 0 and 255, inclusive, then the result is equal to:

(short)((b1 << 8) | b2)

This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readShort in interface java.io.DataInput

Returns:

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

Throws:

java.io.EOFException - if this file reaches the end before reading two bytes.

java.io.IOException - if an I/O error occurs.

readUnsignedShort

public final int readUnsignedShort()
                            throws java.io.IOException

Reads an unsigned 16-bit number from this file. This method reads two bytes from the file. If the bytes read, in order, are b1 and b2, where 0 <= b1, b2 <= 255, then the result is equal to:

(b1 << 8) | b2

This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readUnsignedShort in interface java.io.DataInput

Returns:

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

Throws:

java.io.EOFException - if this file reaches the end before reading two bytes.

java.io.IOException - if an I/O error occurs.

readChar

public final char readChar()
                    throws java.io.IOException

Reads a Unicode character from this file. This method reads two bytes from the file. If the bytes read, in order, are b1 and b2, where 0 <= b1, b2 <= 255, then the result is equal to:

(char)((b1 << 8) | b2)

This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readChar in interface java.io.DataInput

Returns:

the next two bytes of this file as a Unicode character.

Throws:

java.io.EOFException - if this file reaches the end before reading two bytes.

java.io.IOException - if an I/O error occurs.

readInt

public final int readInt()
                  throws java.io.IOException

Reads a signed 32-bit integer from this file. This method reads 4 bytes from the file. If the bytes read, in order, are b1, b2, b3, and b4, where 0 <= b1, b2, b3, b4 <= 255, then the result is equal to:

(b1 << 24) | (b2 << 16) + (b3 << 8) + b4

This method blocks until the four bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readInt in interface java.io.DataInput

Returns:

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

Throws:

java.io.EOFException - if this file reaches the end before reading four bytes.

java.io.IOException - if an I/O error occurs.

readLong

public final long readLong()
                    throws java.io.IOException

Reads a signed 64-bit integer from this file. This method reads eight bytes from the file. If the bytes read, in order, are b1, b2, b3, b4, b5, b6, b7, and b8, where:

0 <= b1, b2, b3, b4, b5, b6, b7, b8 <=255,

then the result is equal to:

 
     ((long)b1 << 56) + ((long)b2 << 48) 
     + ((long)b3 << 40) + ((long)b4 << 32) 
     + ((long)b5 << 24) + ((long)b6 << 16) 
     + ((long)b7 << 8) + b8 
 

This method blocks until the eight bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readLong in interface java.io.DataInput

Returns:

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

Throws:

java.io.EOFException - if this file reaches the end before reading eight bytes.

java.io.IOException - if an I/O error occurs.

readFloat

public final float readFloat()
                      throws java.io.IOException

Reads a float from this file. This method reads an int value as if by the readInt method and then converts that int to a float using the intBitsToFloat method in class Float.

This method blocks until the four bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readFloat in interface java.io.DataInput

Returns:

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

Throws:

java.io.EOFException - if this file reaches the end before reading four bytes.

java.io.IOException - if an I/O error occurs.

See Also:

RandomAccessFile.readInt(), Float.intBitsToFloat(int)

readDouble

public final double readDouble()
                        throws java.io.IOException

Reads a double from this file. This method reads a long value as if by the readLong method and then converts that long to a double using the longBitsToDouble method in class Double.

This method blocks until the eight bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readDouble in interface java.io.DataInput

Returns:

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

Throws:

java.io.EOFException - if this file reaches the end before reading eight bytes.

java.io.IOException - if an I/O error occurs.

See Also:

RandomAccessFile.readLong(), Double.longBitsToDouble(long)

readLine

public final java.lang.String readLine()
                                throws java.io.IOException

Reads the next line of text from this file. This method successively reads bytes from the file until it reaches the end of a line of text.

A line of text is terminated by a carriage-return character ('\r'), a newline character ('\n'), a carriage-return character immediately followed by a newline character, or the end of the input stream. The line-terminating character(s), if any, are included as part of the string returned.

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 stream is detected, or an exception is thrown.

Specified by:

readLine in interface java.io.DataInput

Returns:

the next line of text from this file.

Throws:

java.io.IOException - if an I/O error occurs.

readUTF

public final java.lang.String readUTF()
                               throws java.io.IOException

Reads in a string from this file. The string has been encoded using a modified UTF-8 format.

The first two bytes are read as if by readUnsignedShort. 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 UTF-8 format and are converted into characters.

This method blocks until all the bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readUTF in interface java.io.DataInput

Returns:

a Unicode string.

Throws:

java.io.EOFException - if this file reaches the end before reading all the bytes.

java.io.IOException - if an I/O error occurs.

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

See Also:

RandomAccessFile.readUnsignedShort()

writeBoolean

public final void writeBoolean(boolean v)
                        throws java.io.IOException

Writes a boolean to the file as a 1-byte value. The value true is written out as the value (byte)1; the value false is written out as the value (byte)0.

Specified by:

writeBoolean in interface java.io.DataOutput

Parameters:

v - a boolean value to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeByte

public final void writeByte(int v)
                     throws java.io.IOException

Writes a byte to the file as a 1-byte value.

Specified by:

writeByte in interface java.io.DataOutput

Parameters:

v - a byte value to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeShort

public final void writeShort(int v)
                      throws java.io.IOException

Writes a short to the file as two bytes, high byte first.

Specified by:

writeShort in interface java.io.DataOutput

Parameters:

v - a short to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeChar

public final void writeChar(int v)
                     throws java.io.IOException

Writes a char to the file as a 2-byte value, high byte first.

Specified by:

writeChar in interface java.io.DataOutput

Parameters:

v - a char value to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeInt

public final void writeInt(int v)
                    throws java.io.IOException

Writes an int to the file as four bytes, high byte first.

Specified by:

writeInt in interface java.io.DataOutput

Parameters:

v - an int to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeLong

public final void writeLong(long v)
                     throws java.io.IOException

Writes a long to the file as eight bytes, high byte first.

Specified by:

writeLong in interface java.io.DataOutput

Parameters:

v - a long to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeFloat

public final void writeFloat(float v)
                      throws java.io.IOException

Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the file as a 4-byte quantity, high byte first.

Specified by:

writeFloat in interface java.io.DataOutput

Parameters:

v - a float value to be written.

Throws:

java.io.IOException - if an I/O error occurs.

See Also:

Float.floatToIntBits(float)

writeDouble

public final void writeDouble(double v)
                       throws java.io.IOException

Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the file as an 8-byte quantity, high byte first.

Specified by:

writeDouble in interface java.io.DataOutput

Parameters:

v - a double value to be written.

Throws:

java.io.IOException - if an I/O error occurs.

See Also:

Double.doubleToLongBits(double)

writeBytes

public final void writeBytes(java.lang.String s)
                      throws java.io.IOException

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.

Specified by:

writeBytes in interface java.io.DataOutput

Parameters:

s - a string of bytes to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeBytes

public final void writeBytes(char[] b,
                             int off,
                             int len)
                      throws java.io.IOException

Writes the character array to the file as a sequence of bytes. Each character in the string is written out, in sequence, by discarding its high eight bits.

Parameters:

b - a character array of bytes to be written.

off - the index of the first character to write.

len - the number of characters to write.

Throws:

java.io.IOException - if an I/O error occurs.

writeChars

public final void writeChars(java.lang.String s)
                      throws java.io.IOException

Writes a string to the file as a sequence of characters. Each character is written to the data output stream as if by the writeChar method.

Specified by:

writeChars in interface java.io.DataOutput

Parameters:

s - a String value to be written.

Throws:

java.io.IOException - if an I/O error occurs.

See Also:

RandomAccessFile.writeChar(int)

writeUTF

public final void writeUTF(java.lang.String str)
                    throws java.io.IOException

Writes a string to the file using UTF-8 encoding in a machine-independent manner.

First, two bytes are written to the file as if by the writeShort 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 UTF-8 encoding for each character.

Specified by:

writeUTF in interface java.io.DataOutput

Parameters:

str - a string to be written.

Throws:

java.io.IOException - if an I/O error occurs.

toString

public java.lang.String toString()

Create a string representation of this object.

Returns:

a string representation of the state of the object.

Overrides:

toString in class java.lang.Object

testBytes

public static void testBytes(java.lang.String filename,
                             int bufferSize)

Test the byte operations of the BufferedRandomAccessFile class. These are the methods that read/write on a byte-by-byte basis. The following checks are made:

• Writing random bytes to a file.
• Checking the size of the file is correct.
• Checking that EOF is correctly raised.
• Reading the file back in and verifying its contents.

The test file is 4.5 times the size of the buffer, in order to test paging between buffers, and using files that end in the middle of a buffer. A constant seed value is used for the random number generator, to ensure any bugs are reproduceable.

Parameters:

filename - the name of the test file to generate.

bufferSize - the size of the buffer to use.

testBlocks

public static void testBlocks(java.lang.String filename)

Test the block operations of the BufferedRandomAccessFile class. These are the methods that read/write blocks of data. The following checks are made:

• Writing blocks of data that are smaller than the buffer size.
• Writing blocks of data that are larger than the buffer size.
• Checking the size of the file is correct.
• Reading small blocks of the file back in and verifying its contents.
• Reading large blocks of the file back in and verifying its contents.

Parameters:

filename - the name of the test file to generate.

benchmark

public static void benchmark(java.lang.String filename,
                             int bufferSize)

Benchmark the performance of the new BufferedRandomAccessFile class. Its speed is compared to that of a RandomAccessFile, based on reading and writing a test file, byte by byte.

Parameters:

filename - the name of the test file.

bufferSize - the buffer size to use.

main

public static void main(java.lang.String[] argv)

Test the BufferedRandomAccessFile class. This involves testing the byte methods, the block methods, and benchmarking the performance. By appending 'test' or 'benchmark' to the command-line, it can be limited to the tests or benchmarking alone. The test filename is only used for the benchmarking, the other tests create a file called "temp.data" in the current directory. Note that the size of the buffer determines the size of the test file (which is 4.5 times the size of the buffer).

Parameters:

argv - Usage: [bufferSize] [test | benchmark]

See Also:

testBytes(java.lang.String, int), testBlocks(java.lang.String), benchmark(java.lang.String, int)