org.terrier.compression
Interface BitOut

All Superinterfaces:

java.io.Closeable

All Known Implementing Classes:

BitByteOutputStream, BitFile, BitOutputStream, MemorySBOS

public interface BitOut
extends java.io.Closeable

Interface describing the writing compression methods supported by the BitOutputStream classes. Integers written through these compression methods must be greater than 0.

Since:

2.0

Author:

Craig Macdonald

Method Summary

byte	getBitOffset() Returns the bit offset in the last byte.
long	getByteOffset() Returns the byte offset of the stream.
int	writeBinary(int len, int x) Writes an integer in binary format to the stream.
int	writeDelta(int x) Writes an integer x into the stream using delta encoding.
int	writeGamma(int x) Writes an integer x into the stream using gamma encoding.
int	writeGolomb(int x, int b) Writes and integer x into the stream using golomb coding.
int	writeInt(int x, int len) Writes an integer x into the underlying OutputStream.
int	writeInterpolativeCode(int[] data, int offset, int len, int lo, int hi) Writes a sequence of integers using interpolative coding.
int	writeMinimalBinary(int x, int b) Writes an integer x using minimal binary encoding, given an upper bound.
int	writeSkewedGolomb(int x, int b) Writes and integer x into the stream using skewed-golomb coding.
int	writeUnary(int x) Writes an integer x using unary encoding.

Methods inherited from interface java.io.Closeable

close

Method Detail

getByteOffset

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.

Returns:

the byte offset in the stream.

getBitOffset

byte getBitOffset()

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

Returns:

the bit offset in the stream.

writeUnary

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

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

Parameters:

x - the number to write

Returns:

the number of bits written

Throws:

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

writeGamma

int writeGamma(int x)
               throws java.io.IOException

Writes an integer x into the stream using gamma encoding. This method is not failsafe, it doesn't check if the argument is 0 or negative.

Parameters:

x - the int number to write

Returns:

the number of bits written

Throws:

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

writeBinary

int writeBinary(int len,
                int x)
                throws java.io.IOException

Writes an integer in binary format to the stream.

Parameters:

len - size in bits of the number.

x - the integer to write.

Returns:

the number of bits written.

Throws:

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

writeInterpolativeCode

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

Writes a sequence of integers using interpolative coding. The data must be sorted (increasing order).

Parameters:

data - the vector containing the integer sequence.

offset - the offset into data where the sequence starts.

len - the number of integers to code.

lo - a lower bound (must be smaller than or equal to the first integer in the sequence).

hi - an upper bound (must be greater than or equal to the last integer in the sequence).

Returns:

the number of written bits.

Throws:

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

writeSkewedGolomb

int writeSkewedGolomb(int x,
                      int b)
                      throws java.io.IOException

Writes and integer x into the stream using skewed-golomb coding. Consider a bucket-vector v = <b, 2b, 4b, ... , 2^i b, ...> an integer x is coded as unary(k+1) where k is the index sum(i=0)(k) v_i < x <= sum(i=0)(k+1)
, so k = log(x/b + 1) sum_i = b(2^n -1) (geometric progression) and the remainder with log(v_k) bits in binary if lower = ceil(x/b) -> lower = 2^i * b -> i = log(ceil(x/b)) + 1 the remainder x - sum_i 2^i*b - 1 = x - b(2^n - 1) - 1 is coded with floor(log(v_k)) bits This method is not failsafe, it doesn't check if the argument or the modulus is 0 or negative.

Parameters:

x - the number to write

b - the parameter for golomb coding

Returns:

the number of bits written

Throws:

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

writeGolomb

int writeGolomb(int x,
                int b)
                throws java.io.IOException

Writes and integer x into the stream using golomb coding. This method is not failsafe, it doesn't check if the argument or the modulus is 0 or negative.

Parameters:

x - the number to write

b - the parameter for golomb coding

Returns:

the number of bits written

Throws:

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

writeMinimalBinary

int writeMinimalBinary(int x,
                       int b)
                       throws java.io.IOException

Writes an integer x using minimal binary encoding, given an upper bound. This method is not failsafe, it doesn't check if the argument is 0 or negative.

Parameters:

x - the number to write

b - and strict bound for x

Returns:

the number of bits written

Throws:

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

writeDelta

int writeDelta(int x)
               throws java.io.IOException

Writes an integer x into the stream using delta encoding. This method is not failsafe, it doesn't check if the argument is 0 or negative.

Parameters:

x - the int number to write

Returns:

the number of bits written

Throws:

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

writeInt

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 writing, and then it writes as many bytes as necessary

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.