org.terrier.compression
Class BitInputStream

java.lang.Object
  org.terrier.compression.BitInputStream

All Implemented Interfaces:

java.io.Closeable, BitIn

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

Field Summary

protected int	bitOffset The bit offset.
protected long	byteOffset The byte offset.
protected byte	byteRead A byte read from the stream.
protected java.io.DataInput	dis The private input stream used internaly.

Fields inherited from interface org.terrier.compression.BitIn

USUAL_EXTENSION

Constructor Summary

protected	BitInputStream() Do nothing constructor used by child classes which override all methods, eg OldBitInputStream
	BitInputStream(java.io.DataInput in) Constructs an instance of the class for a given stream
	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 = <b, 2b, 4b, ...
int	readUnary() Reads a unary encoded integer from the underlying stream
void	skipBits(int len) Skip a number of bits while reading the bit file.
void	skipBytes(long len) Skip a number of bytes while reading the bit file.

Methods inherited from class java.lang.Object

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

Field Detail

dis

protected java.io.DataInput dis

The private input stream used internaly.

byteOffset

protected long byteOffset

The byte offset.

bitOffset

protected int bitOffset

The bit offset.

byteRead

protected byte byteRead

A byte read from the stream. This byte should be initialised during the construction of the class.

Constructor Detail

BitInputStream

protected BitInputStream()

Do nothing constructor used by child classes which override all methods, eg OldBitInputStream

BitInputStream

public BitInputStream(java.io.DataInput in)
               throws java.io.IOException

Constructs an instance of the class for a given stream

Parameters:

in - java.io.DataInput the underlying input stream

Throws:

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

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 while reading the bit file.

Specified by:

skipBits in interface BitIn

Parameters:

len - The number of bits to skip

Throws:

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

skipBytes

public void skipBytes(long len)
               throws java.io.IOException

Skip a number of bytes while reading the bit file. After this opteration, getBitOffset() == 0, so use skipBits to get getBitOffset() to desired value.

Specified by:

skipBytes in interface BitIn

Parameters:

len - The number of bytes 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

Specified by:

readMinimalBinary in interface BitIn

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

Specified by:

readGolomb in interface BitIn

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

Specified by:

readDelta in interface BitIn

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 = <b, 2b, 4b, ... , 2^i b, ...> The sum of the elements in the vector goes b, 3b, 7b, 2^(i-1)*b

Specified by:

readSkewedGolomb in interface BitIn

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.

Specified by:

readInterpolativeCoding in interface BitIn

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

Specified by:

readMinimalBinaryZero in interface BitIn

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