jj2000.j2k.entropy.encoder
Class BitToByteOutput

java.lang.Object
  |
  +--jj2000.j2k.entropy.encoder.BitToByteOutput

class BitToByteOutput

extends java.lang.Object

This class provides an adapter to perform bit based output on byte based output objects that inherit from a 'ByteOutputBuffer' class. This class implements the bit stuffing policy needed for the 'selective arithmetic coding bypass' mode of the entropy coder. This class also delays the output of a trailing 0xFF, since they are synthetized be the decoder.

Field Summary

(package private) int	bbuf The bit buffer
(package private) int	bpos The position of the next bit to put in the bit buffer.
(package private) boolean	delFF Flag that indicates if an FF has been delayed
private boolean	isPredTerm Whether or not predictable termination is requested.
(package private) int	nb The number of written bytes (excluding the bit buffer)
(package private) ByteOutputBuffer	out The byte based output
(package private) static int	PAD_SEQ The alternating sequence of 0's and 1's used for byte padding

Constructor Summary

(package private)

BitToByteOutput(ByteOutputBuffer out) Instantiates a new 'BitToByteOutput' object that uses 'out' as the underlying byte based output.

Method Summary

(package private) void	flush() Writes the contents of the bit buffer and byte aligns the output by filling bits with an alternating sequence of 0's and 1's.
(package private) int	length() Returns the length, in bytes, of the output bit stream as written by this object.
(package private) void	reset() Resets the bit buffer to empty, without writing anything to the underlying byte output, and resets the byte count.
(package private) void	setPredTerm(boolean isPredTerm) Set the flag according to whether or not the predictable termination is requested.
int	terminate() Terminates the bit stream by calling 'flush()' and then 'reset()'.
(package private) void	writeBit(int bit) Write a bit to the output.
(package private) void	writeBits(int[] symbuf, int nsym) Writes to the bit stream the symbols contained in the 'symbuf' buffer.

Methods inherited from class java.lang.Object

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

Field Detail

isPredTerm

private boolean isPredTerm

Whether or not predictable termination is requested. This value is important when the last byte before termination is an 0xFF

PAD_SEQ

static final int PAD_SEQ

The alternating sequence of 0's and 1's used for byte padding

See Also:

Constant Field Values

delFF

boolean delFF

Flag that indicates if an FF has been delayed

out

ByteOutputBuffer out

The byte based output

bbuf

int bbuf

The bit buffer

bpos

int bpos

The position of the next bit to put in the bit buffer. When it is 7 the bit buffer 'bbuf' is empty. The value should always be between 7 and 0 (i.e. if it gets to -1, the bit buffer should be immediately written to the byte output).

nb

int nb

The number of written bytes (excluding the bit buffer)

Constructor Detail

BitToByteOutput

BitToByteOutput(ByteOutputBuffer out)

Instantiates a new 'BitToByteOutput' object that uses 'out' as the underlying byte based output.

Parameters:

out - The underlying byte based output

Method Detail

writeBits

final void writeBits(int[] symbuf,
                     int nsym)

Writes to the bit stream the symbols contained in the 'symbuf' buffer. The least significant bit of each element in 'symbuf'is written.

Parameters:

symbuf - The symbols to write

nsym - The number of symbols in symbuf

writeBit

final void writeBit(int bit)

Write a bit to the output. The least significant bit of 'bit' is written to the output.

Parameters:

bit -

flush

void flush()

Writes the contents of the bit buffer and byte aligns the output by filling bits with an alternating sequence of 0's and 1's.

terminate

public int terminate()

Terminates the bit stream by calling 'flush()' and then 'reset()'. Finally, it returns the number of bytes effectively written.

Returns:

The number of bytes effectively written.

reset

void reset()

Resets the bit buffer to empty, without writing anything to the underlying byte output, and resets the byte count. The underlying byte output is NOT reset.

length

int length()

Returns the length, in bytes, of the output bit stream as written by this object. If the output bit stream does not have an integer number of bytes in length then it is rounded to the next integer.

Returns:

The length, in bytes, of the output bit stream.

setPredTerm

void setPredTerm(boolean isPredTerm)

Set the flag according to whether or not the predictable termination is requested.

Parameters:

isPredTerm - Whether or not predictable termination is requested.