uk.ac.gla.terrier.compression
Class BitInputStream

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

All Implemented Interfaces:

java.io.Closeable, BitIn

Direct Known Subclasses:

OldBitInputStream

public class BitInputStream
extends java.lang.Object
implements BitIn

This class reads from a file or an InputStream integers that can be coded with different encoding algorithms. It does not use any internal buffering, and operates with bytes.

Author:

Roi Blanco

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	align() Aligns the stream to the next byte
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 len) Reads a binary integer from the already read buffer.
int	readDelta() Reads a delta encoded integer from the underlying stream
int	readGamma() Reads a gamma encoded integer from the underlying stream
int	readGolomb(int b) Reads a Golomb encoded integer
void	readInterpolativeCoding(int[] data, int offset, int len, int lo, int hi) Reads a sequence of numbers from the stream interpolative coded.
int	readMinimalBinary(int b) Reads a binary encoded integer, given an upper bound
int	readMinimalBinaryZero(int b) Reads a minimal binary encoded number, when the upper bound can b zero.
int	readSkewedGolomb(int b) Reads a skewed-golomb encoded integer from the underlying stream Consider a bucket-vector v =
int	readUnary() Reads a unary encoded integer from the underlying stream
void	skipBits(int len) Skip a number of bits in the current input 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

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

close

public void close()
           throws java.io.IOException

Closes the stream.

Specified by:

close in interface java.io.Closeable

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.

Specified by:

getByteOffset in interface BitIn

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.

Specified by:

getBitOffset in interface BitIn

Returns:

the bit offset in the stream.

readUnary

public int readUnary()
              throws java.io.IOException

Reads a unary encoded integer from the underlying stream

Specified by:

readUnary in interface BitIn

Returns:

the number read

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 underlying stream

Specified by:

readGamma in interface BitIn

Returns:

the number read

Throws:

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

readBinary

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

Reads a binary integer from the already read buffer.

Specified by:

readBinary in interface BitIn

Parameters:

len - the number of binary bits to read

Returns:

the decoded integer

Throws:

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

skipBits

public void skipBits(int len)
              throws java.io.IOException

Skip a number of bits in the current input stream

Specified by:

skipBits in interface BitIn

Parameters:

len - The number of bits to skip

Throws:

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

readMinimalBinary

public int readMinimalBinary(int b)
                      throws java.io.IOException

Reads a binary encoded integer, given an upper bound

Parameters:

b - the upper bound

Returns:

the int read

Throws:

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

readGolomb

public int readGolomb(int b)
               throws java.io.IOException

Reads a Golomb encoded integer

Parameters:

b - the golomb modulus

Returns:

the int read

Throws:

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

readDelta

public int readDelta()
              throws java.io.IOException

Reads a delta encoded integer from the underlying stream

Returns:

the number read

Throws:

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

readSkewedGolomb

public int readSkewedGolomb(int b)
                     throws java.io.IOException

Reads a skewed-golomb encoded integer from the underlying stream Consider a bucket-vector v = The sum of the elements in the vector goes b, 3b, 7b, 2^(i-1)*b

Returns:

the number read

Throws:

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

readInterpolativeCoding

public void readInterpolativeCoding(int[] data,
                                    int offset,
                                    int len,
                                    int lo,
                                    int hi)
                             throws java.io.IOException

Reads a sequence of numbers from the stream interpolative coded.

Parameters:

data - the result vector

offset - offset where to write in the vector

len - the number of integers to decode.

lo - a lower bound (the same one passed to writeInterpolativeCoding)

hi - an upper bound (the same one passed to writeInterpolativeCoding)

Throws:

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

readMinimalBinaryZero

public int readMinimalBinaryZero(int b)
                          throws java.io.IOException

Reads a minimal binary encoded number, when the upper bound can b zero. Used to interpolative code

Parameters:

b - the upper bound

Returns:

the int read

Throws:

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

align

public void align()
           throws java.io.IOException

Aligns the stream to the next byte

Specified by:

align in interface BitIn

Throws:

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