jj2000.j2k.codestream.reader

Class PktHeaderBitReader

java.lang.Object

jj2000.j2k.codestream.reader.PktHeaderBitReader

class PktHeaderBitReader
extends Object

This class provides a bit based reading facility from a byte based one, applying the bit unstuffing procedure as required by the packet headers.

Field Summary

Fields

Modifier and Type	Field and Description
(package private) ByteArrayInputStream	bais The byte array that is the source of data if the PktHeaderBitReader is instantiated with a buffer instead of a RandomAccessIO
(package private) int	bbuf The current bit buffer
(package private) int	bpos The position of the next bit to read in the bit buffer (0 means empty, 8 full)
(package private) RandomAccessIO	in The byte based source of data
(package private) int	nextbbuf The next bit buffer, if bit stuffing occurred (i.e.
(package private) boolean	usebais Flag indicating whether the data should be read from the buffer

Constructor Summary

Constructors

Constructor and Description
PktHeaderBitReader(ByteArrayInputStream bais) Instantiates a 'PktHeaderBitReader' that gets the byte data from the given source.
PktHeaderBitReader(RandomAccessIO in) Instantiates a 'PktHeaderBitReader' that gets the byte data from the given source.

Method Summary

Modifier and Type	Method and Description
(package private) int	readBit() Reads a single bit from the input.
(package private) int	readBits(int n) Reads a specified number of bits and returns them in a single integer.
(package private) void	setInput(ByteArrayInputStream bais) Sets the underlying byte based input to the given object.
(package private) void	setInput(RandomAccessIO in) Sets the underlying byte based input to the given object.
(package private) void	sync() Synchronizes this object with the underlying byte based input.

Methods inherited from class java.lang.Object

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

Field Detail

in

RandomAccessIO in

The byte based source of data

bais

ByteArrayInputStream bais

The byte array that is the source of data if the PktHeaderBitReader is instantiated with a buffer instead of a RandomAccessIO

usebais

boolean usebais

Flag indicating whether the data should be read from the buffer

bbuf

int bbuf

The current bit buffer

bpos

int bpos

The position of the next bit to read in the bit buffer (0 means empty, 8 full)

nextbbuf

int nextbbuf

The next bit buffer, if bit stuffing occurred (i.e. current bit buffer holds 0xFF)

Constructor Detail

PktHeaderBitReader

PktHeaderBitReader(RandomAccessIO in)

Instantiates a 'PktHeaderBitReader' that gets the byte data from the given source.

Parameters:

in - The source of byte data

PktHeaderBitReader

PktHeaderBitReader(ByteArrayInputStream bais)

Instantiates a 'PktHeaderBitReader' that gets the byte data from the given source.

Parameters:

bais - The source of byte data

Method Detail

readBit

final int readBit()
           throws IOException

Reads a single bit from the input.

Returns:

The read bit (0 or 1)

Throws:

IOException - If an I/O error occurred

EOFException - If teh end of file has been reached

readBits

final int readBits(int n)
            throws IOException

Reads a specified number of bits and returns them in a single integer. The bits are returned in the 'n' least significant bits of the returned integer. The maximum number of bits that can be read is 31.

Parameters:

n - The number of bits to read

Returns:

The read bits, packed in the 'n' LSBs.

Throws:

IOException - If an I/O error occurred

EOFException - If teh end of file has been reached

sync

void sync()

Synchronizes this object with the underlying byte based input. It discards and buffered bits and gets ready to read bits from the current position in the underlying byte based input.

This method should always be called when some data has been read directly from the underlying byte based input since the last call to 'readBits()' or 'readBit()' before a new call to any of those methods.

setInput

void setInput(RandomAccessIO in)

Sets the underlying byte based input to the given object. This method discards any currently buffered bits and gets ready to start reading bits from 'in'.

This method is equivalent to creating a new 'PktHeaderBitReader' object.

Parameters:

in - The source of byte data

setInput

void setInput(ByteArrayInputStream bais)

Sets the underlying byte based input to the given object. This method discards any currently buffered bits and gets ready to start reading bits from 'in'.

This method is equivalent to creating a new 'PktHeaderBitReader' object.

Parameters:

bais - The source of byte data