pt.tumba.ngram.compression
Class BitInput

java.lang.Object
  pt.tumba.ngram.compression.BitInput

public final class BitInput
extends java.lang.Object

Reads input from an underlying input stream a bit at a time. Bits are returned as booleans, with true=1 and false=0.

Author:

Bruno Martins

See Also:

BitOutput

Field Summary

private boolean	_endOfStream Set to true when all bits have been read.
private java.io.InputStream	_in Underlying input stream.
private int	_nextBitIndex Position of next bit in the buffered byte.
private int	_nextByte Buffered byte from which bits are read.

Constructor Summary

BitInput(java.io.InputStream in)
Constructs a bit input from an underlying input stream.

Method Summary

long	available() Returns number of bits available for reading.
void	close() Closes the underlying input stream.
boolean	endOfStream() Returns true if all of the available bits have been read.
private void	readAhead() Reads the next byte from the input stream into _nextByte.
boolean	readBit() Reads the next bit from the input stream.

Methods inherited from class java.lang.Object

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

Field Detail

_in

private final java.io.InputStream _in

Underlying input stream.

_nextByte

private int _nextByte

Buffered byte from which bits are read.

_nextBitIndex

private int _nextBitIndex

Position of next bit in the buffered byte.

_endOfStream

private boolean _endOfStream

Set to true when all bits have been read.

Constructor Detail

BitInput

public BitInput(java.io.InputStream in)
         throws java.io.IOException

Constructs a bit input from an underlying input stream.

Parameters:

in - Input stream backing this bit input.

Throws:

java.io.IOException - If there is an exception reading from the specified input stream.

Method Detail

available

public long available()
               throws java.io.IOException

Returns number of bits available for reading. Will always be 0 or 1.

Returns:

Number of bits available for reading.

Throws:

java.io.IOException - If there is an exception checking available bytes in the underlying input stream.

close

public void close()
           throws java.io.IOException

Closes the underlying input stream.

Throws:

java.io.IOException - If there is an exception closing the underlying input stream.

endOfStream

public boolean endOfStream()

Returns true if all of the available bits have been read.

Returns:

true if all of the available bits have been read.

readBit

public boolean readBit()
                throws java.io.IOException

Reads the next bit from the input stream. Returns garbage if reading while available() is false.

Returns:

The boolean value of the next bit, true=1, false=0.

Throws:

java.io.IOException - If there is an exception reading a byte from the underlying stream.

readAhead

private void readAhead()
                throws java.io.IOException

Reads the next byte from the input stream into _nextByte.

Throws:

java.io.IOException - If there is an IOException reading from the stream.