jj2000.j2k.io

Class BufferedRandomAccessFile

java.lang.Object

jj2000.j2k.io.BufferedRandomAccessFile

All Implemented Interfaces:

BinaryDataInput, BinaryDataOutput, EndianType, RandomAccessIO

Direct Known Subclasses:

BEBufferedRandomAccessFile

public abstract class BufferedRandomAccessFile
extends Object
implements RandomAccessIO, EndianType

This class defines a Buffered Random Access File. It implements the BinaryDataInput and BinaryDataOutput interfaces so that binary data input/output can be performed. This class is abstract since no assumption is done about the byte ordering type (little Endian, big Endian). So subclasses will have to implement methods like readShort(), writeShort(), readFloat(), ...

BufferedRandomAccessFile (BRAF for short) is a RandomAccessFile containing an extra buffer. When the BRAF is accessed, it checks if the requested part of the file is in the buffer or not. If that is the case, the read/write is done on the buffer. If not, the file is uppdated to reflect the current status of the buffer and the file is then accessed for a new buffer containing the requested byte/bit.

See Also:

RandomAccessIO, BinaryDataOutput, BinaryDataInput, BEBufferedRandomAccessFile

Field Summary

Fields

Modifier and Type	Field and Description
protected byte[]	byteBuffer Buffer of bytes containing the part of the file that is currently being accessed
protected boolean	byteBufferChanged Boolean keeping track of whether the byte buffer has been changed since it was read.
protected int	byteOrdering
protected boolean	isEOFInBuffer Whether the end of the file is in the current buffer or not
protected int	maxByte The maximum number of bytes that can be read from the buffer
protected int	offset The current offset of the buffer (which will differ from the offset of the file)
protected int	pos The current position in the byte-buffer

Fields inherited from interface jj2000.j2k.io.EndianType

BIG_ENDIAN, LITTLE_ENDIAN

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	BufferedRandomAccessFile(File file, String mode) Constructor.
protected	BufferedRandomAccessFile(File file, String mode, int bufferSize) Constructor.
protected	BufferedRandomAccessFile(String name, String mode) Constructor.
protected	BufferedRandomAccessFile(String name, String mode, int bufferSize) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
void	close() Closes the buffered random access file
void	flush() Any data that has been buffered must be written (including buffering at the bit level), and the stream should be realigned at the byte level.
int	getByteOrdering() Returns the endianess (i.e., byte ordering) of the implementing class.
int	getPos() Returns the current offset in the file
int	length() Returns the current length of the stream, in bytes, taking into account any buffering.
int	read() Reads an unsigned byte of data from the stream.
byte	readByte() Reads a signed byte (i.e., 8 bit) from the input.
void	readFully(byte[] b, int off, int len) Reads up to len bytes of data from this file into an array of bytes.
protected void	readNewBuffer(int off) Reads a new buffer from the file.
int	readUnsignedByte() Reads an unsigned byte (i.e., 8 bit) from the input.
void	seek(int off) Moves the current position to the given offset at which the next read or write occurs.
int	skipBytes(int n) Skips n bytes from the input.
String	toString() Returns a string of information about the file
void	write(byte b) Writes a byte to the stream.
void	write(byte[] b, int offset, int length) Writes aan array of bytes to the stream.
void	write(int b) Writes a byte to the stream.
void	writeByte(int v) Writes the byte value of v (i.e., 8 least significant bits) to the output.

Methods inherited from class java.lang.Object

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

Methods inherited from interface jj2000.j2k.io.BinaryDataInput

readDouble, readFloat, readInt, readLong, readShort, readUnsignedInt, readUnsignedShort

Methods inherited from interface jj2000.j2k.io.BinaryDataOutput

writeDouble, writeFloat, writeInt, writeLong, writeShort

Field Detail

byteBuffer

protected byte[] byteBuffer

Buffer of bytes containing the part of the file that is currently being accessed

byteBufferChanged

protected boolean byteBufferChanged

Boolean keeping track of whether the byte buffer has been changed since it was read.

offset

protected int offset

The current offset of the buffer (which will differ from the offset of the file)

pos

protected int pos

The current position in the byte-buffer

maxByte

protected int maxByte

The maximum number of bytes that can be read from the buffer

isEOFInBuffer

protected boolean isEOFInBuffer

Whether the end of the file is in the current buffer or not

byteOrdering

protected int byteOrdering

Constructor Detail

BufferedRandomAccessFile

protected BufferedRandomAccessFile(File file,
                        String mode,
                        int bufferSize)
                            throws IOException

Constructor. Always needs a size for the buffer.

Parameters:

file - The file associated with the buffer

mode - "r" for read, "rw" or "rw+" for read and write mode ("rw+" opens the file for update whereas "rw" removes it before. So the 2 modes are different only if the file already exists).

bufferSize - The number of bytes to buffer

Throws:

IOException - If an I/O error occurred.

BufferedRandomAccessFile

protected BufferedRandomAccessFile(File file,
                        String mode)
                            throws IOException

Constructor. Uses the default value for the byte-buffer size (512 bytes).

Parameters:

file - The file associated with the buffer

mode - "r" for read, "rw" or "rw+" for read and write mode ("rw+" opens the file for update whereas "rw" removes it before. So the 2 modes are different only if the file already exists).

Throws:

IOException - If an I/O error occurred.

BufferedRandomAccessFile

protected BufferedRandomAccessFile(String name,
                        String mode,
                        int bufferSize)
                            throws IOException

Constructor. Always needs a size for the buffer.

Parameters:

name - The name of the file associated with the buffer

mode - "r" for read, "rw" or "rw+" for read and write mode ("rw+" opens the file for update whereas "rw" removes it before. So the 2 modes are different only if the file already exists).

bufferSize - The number of bytes to buffer

Throws:

IOException - If an I/O error occurred.

BufferedRandomAccessFile

protected BufferedRandomAccessFile(String name,
                        String mode)
                            throws IOException

Constructor. Uses the default value for the byte-buffer size (512 bytes).

Parameters:

name - The name of the file associated with the buffer

mode - "r" for read, "rw" or "rw+" for read and write mode ("rw+" opens the file for update whereas "rw" removes it before. So the 2 modes are different only if the file already exists).

Throws:

IOException - If an I/O error occurred.

Method Detail

readNewBuffer

protected final void readNewBuffer(int off)
                            throws IOException

Reads a new buffer from the file. If there has been any changes made since the buffer was read, the buffer is first written to the file.

Parameters:

off - The offset where to move to.

Throws:

IOException - If an I/O error occurred.

close

public void close()
           throws IOException

Closes the buffered random access file

Specified by:

close in interface RandomAccessIO

Throws:

IOException - If an I/O error occurred.

getPos

public int getPos()

Returns the current offset in the file

Specified by:

getPos in interface RandomAccessIO

Returns:

The offset of the current position, in bytes.

length

public int length()
           throws IOException

Returns the current length of the stream, in bytes, taking into account any buffering.

Specified by:

length in interface RandomAccessIO

Returns:

The length of the stream, in bytes.

Throws:

IOException - If an I/O error occurred.

seek

public void seek(int off)
          throws IOException

Moves the current position to the given offset at which the next read or write occurs. The offset is measured from the beginning of the stream.

Specified by:

seek in interface RandomAccessIO

Parameters:

off - The offset where to move to.

Throws:

EOFException - If in read-only and seeking beyond EOF.

IOException - If an I/O error occurred.

read

public final int read()
               throws IOException,
                      EOFException

Reads an unsigned byte of data from the stream. Prior to reading, the stream is realigned at the byte level.

Specified by:

read in interface RandomAccessIO

Returns:

The byte read.

Throws:

IOException - If an I/O error occurred.

EOFException - If the end of file was reached

readFully

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

Reads up to len bytes of data from this file into an array of bytes. This method reads repeatedly from the stream 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 RandomAccessIO

Parameters:

b - The buffer into which the data is to be read. It must be long enough.

off - The index in 'b' where to place the first byte read.

len - The number of bytes to read.

Throws:

EOFException - If the end-of file was reached before getting all the necessary data.

IOException - If an I/O error occurred.

write

public final void write(int b)
                 throws IOException

Writes a byte to the stream. Prior to writing, the stream is realigned at the byte level.

Specified by:

write in interface RandomAccessIO

Parameters:

b - The byte to write. The lower 8 bits of b are written.

Throws:

IOException - If an I/O error occurred.

write

public final void write(byte b)
                 throws IOException

Writes a byte to the stream. Prior to writing, the stream is realigned at the byte level.

Parameters:

b - The byte to write.

Throws:

IOException - If an I/O error occurred.

write

public final void write(byte[] b,
         int offset,
         int length)
                 throws IOException

Writes aan array of bytes to the stream. Prior to writing, the stream is realigned at the byte level.

Parameters:

b - The array of bytes to write.

offset - The first byte in b to write

length - The number of bytes from b to write

Throws:

IOException - If an I/O error occurred.

writeByte

public final void writeByte(int v)
                     throws IOException

Writes the byte value of v (i.e., 8 least significant bits) to the output. Prior to writing, the output should be realigned at the byte level.

Signed or unsigned data can be written. To write a signed value just pass the byte value as an argument. To write unsigned data pass the int value as an argument (it will be automatically casted, and only the 8 least significant bits will be written).

Specified by:

writeByte in interface BinaryDataOutput

Parameters:

v - The value to write to the output

Throws:

IOException - If an I/O error occurred.

flush

public final void flush()
                 throws IOException

Any data that has been buffered must be written (including buffering at the bit level), and the stream should be realigned at the byte level.

Specified by:

flush in interface BinaryDataOutput

Throws:

IOException - If an I/O error occurred.

readByte

public final byte readByte()
                    throws EOFException,
                           IOException

Reads a signed byte (i.e., 8 bit) from the input. Prior to reading, the input should be realigned at the byte level.

Specified by:

readByte in interface BinaryDataInput

Returns:

The next byte-aligned signed byte (8 bit) from the input.

Throws:

EOFException - If the end-of file was reached before getting all the necessary data.

IOException - If an I/O error occurred.

readUnsignedByte

public final int readUnsignedByte()
                           throws EOFException,
                                  IOException

Reads an unsigned byte (i.e., 8 bit) from the input. It is returned as an int since Java does not have an unsigned byte type. Prior to reading, the input should be realigned at the byte level.

Specified by:

readUnsignedByte in interface BinaryDataInput

Returns:

The next byte-aligned unsigned byte (8 bit) from the input, as an int.

Throws:

EOFException - If the end-of file was reached before getting all the necessary data.

IOException - If an I/O error occurred.

getByteOrdering

public int getByteOrdering()

Returns the endianess (i.e., byte ordering) of the implementing class. Note that an implementing class may implement only one type of endianness or both, which would be decided at creation time.

Specified by:

getByteOrdering in interface BinaryDataInput

Specified by:

getByteOrdering in interface BinaryDataOutput

Returns:

Either EndianType.BIG_ENDIAN or EndianType.LITTLE_ENDIAN

See Also:

EndianType

skipBytes

public int skipBytes(int n)
              throws EOFException,
                     IOException

Skips n bytes from the input. Prior to skipping, the input should be realigned at the byte level.

Specified by:

skipBytes in interface BinaryDataInput

Parameters:

n - The number of bytes to skip

Throws:

EOFException - If the end-of file was reached before all the bytes could be skipped.

IOException - If an I/O error occurred.

toString

public String toString()

Returns a string of information about the file

Overrides:

toString in class Object