uk.ac.gla.terrier.compression
Class BitInputStream

java.lang.Object
  uk.ac.gla.terrier.compression.BitInputStream

public class BitInputStream
extends java.lang.Object

This class provides sequential stream access to a compressed BitFile file.

Version:

$Revision: 1.18 $

Author:

Gianni Amati, Vassilis Plachouras, Douglas Johnson

See Also:

BitFile

Constructor Summary

BitInputStream(java.io.File file)
Constructs an instance of the class for a given file

BitInputStream(java.io.InputStream is)
Constructs an instance of the class for a given stream.

BitInputStream(java.lang.String filename)
Constructs an instance of the class for a given filename

Method Summary

void	close() Closes the stream.
byte	getBitOffset() Returns the bit offset in the last byte.
long	getByteOffset() Returns the byte offset of the stream.
int	readBinary(int noBits) Reads a binary integer from the already read buffer.
int	readGamma() Reads a gamma encoded integer from the stream
int	readUnary() Reads a unary encoded integer from the stream.

Methods inherited from class java.lang.Object

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

Constructor Detail

BitInputStream

public BitInputStream(java.io.InputStream is)
               throws java.io.IOException

Constructs an instance of the class for a given stream. We recommend that the inputstream passed to this class if buffered in some way - ie using java.io.BufferedInputStream

Parameters:

is - java.io.InputStream the underlying input stream

Throws:

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

BitInputStream

public BitInputStream(java.lang.String filename)
               throws java.io.IOException

Constructs an instance of the class for a given filename

Parameters:

filename - java.lang.String the name of the undelying file

Throws:

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

BitInputStream

public BitInputStream(java.io.File file)
               throws java.io.IOException

Constructs an instance of the class for a given file

Parameters:

file - java.io.File the underlying file

Throws:

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

Method Detail

readBinary

public int readBinary(int noBits)
               throws java.io.IOException

Reads a binary integer from the already read buffer. No IO is performed and 0 is returned if noBits == 0. NB: noBits > than 32 will give undefined results.

Parameters:

noBits - the number of binary bits to read

Returns:

the decoded integer, -1 if eof was reached unexpectedly

Throws:

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

close

public void close()
           throws java.io.IOException

Closes the stream.

Throws:

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

readUnary

public int readUnary()
              throws java.io.IOException

Reads a unary encoded integer from the stream.

Returns:

the decoded integer, or -1 if EOF is found

Throws:

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

readGamma

public int readGamma()
              throws java.io.IOException

Reads a gamma encoded integer from the stream

Returns:

the decoded integer, or -1 if EOF is found

Throws:

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

getByteOffset

public long getByteOffset()

Returns the byte offset of the stream. It corresponds to the offset of the byte from which the next bit will be read.

Returns:

the byte offset in the stream.

getBitOffset

public byte getBitOffset()

Returns the bit offset in the last byte. It corresponds to the next bit that it will be read.

Returns:

the bit offset in the stream.