uk.ac.gla.terrier.compression
Class BitByteOutputStream

java.lang.Object
  uk.ac.gla.terrier.compression.BitOutputStream
      uk.ac.gla.terrier.compression.BitByteOutputStream

All Implemented Interfaces:

java.io.Closeable, BitOut

Direct Known Subclasses:

MemorySBOS

public class BitByteOutputStream
extends BitOutputStream

This class provides methods to write compressed integers to an outputstream.
The numbers are written into a byte starting from the most significant bit (i.e, left to right). This class does not use any buffering, it relies on the underlying OutputStream to decide when to flush to disk. It is used for indexing, when keeping many compressed streams in memory (MemoryOutputStream) and a two-level buffering is unnecessary (and slower).

Author:

Roi Blanco

Constructor Summary

BitByteOutputStream()
Empty constructor, used for subclassing

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

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

BitByteOutputStream(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.
byte	getByteToWrite()
void	pad() Fills the remaining bits of the current byte with 0s
int	writeInt(int x, int len) Writes an integer x into the underlying OutputStream.
int	writeUnary(int x) Writes an integer x using unary encoding.

Methods inherited from class uk.ac.gla.terrier.compression.BitOutputStream

append, append, flush, padAndFlush, writeBinary, writeDelta, writeGamma, writeGolomb, writeInterpolativeCode, writeMinimalBinary, writeSkewedGolomb

Methods inherited from class java.lang.Object

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

Constructor Detail

BitByteOutputStream

public BitByteOutputStream(java.io.OutputStream is)
                    throws java.io.IOException

Constructs an instance of the class for a given stream

Parameters:

is - java.io.OutputStream the underlying input stream

Throws:

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

BitByteOutputStream

public BitByteOutputStream(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 underlying file

Throws:

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

BitByteOutputStream

public BitByteOutputStream(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

BitByteOutputStream

public BitByteOutputStream()

Empty constructor, used for subclassing

Method Detail

close

public void close()
           throws java.io.IOException

Closes the stream.

Specified by:

close in interface java.io.Closeable

Overrides:

close in class BitOutputStream

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 position of the byte in which the next bit will be written.

Specified by:

getByteOffset in interface BitOut

Overrides:

getByteOffset in class BitOutputStream

Returns:

the byte offset in the stream.

getBitOffset

public byte getBitOffset()

Returns the bit offset in the last byte. It corresponds to the position in which the next bit will be written.

Specified by:

getBitOffset in interface BitOut

Overrides:

getBitOffset in class BitOutputStream

Returns:

the bit offset in the stream.

writeUnary

public int writeUnary(int x)
               throws java.io.IOException

Writes an integer x using unary encoding. The encoding is a sequence of x -1 zeroes and 1 one: 1, 01, 001, 0001, etc .. This method is not failsafe, it doesn't check if the argument is 0 or negative.

Specified by:

writeUnary in interface BitOut

Overrides:

writeUnary in class BitOutputStream

Parameters:

x - the number to write

Returns:

the number of bis written

Throws:

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

writeInt

public int writeInt(int x,
                    int len)
             throws java.io.IOException

Writes an integer x into the underlying OutputStream. First, it checks if it fits into the current byte we are using for writting, and then it writes as many bytes as necessary

Overrides:

writeInt in class BitOutputStream

Parameters:

x - the int to write

len - length of the int in bits

Returns:

the number of bits written

Throws:

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

pad

public void pad()
         throws java.io.IOException

Fills the remaining bits of the current byte with 0s

Throws:

java.io.IOException

getByteToWrite

public byte getByteToWrite()

Returns:

the actual byte it is being written.