it.unimi.dsi.compression

Class TreeDecoder

java.lang.Object

it.unimi.dsi.compression.TreeDecoder

All Implemented Interfaces:

Decoder, Serializable

public final class TreeDecoder
extends Object
implements Decoder, Serializable

A decoder that follows 0/1 labelled paths in a tree.

Additional, the buildCodes() method returns a vector of codewords corresponding to the paths of an instance of this class. Conversely, the codeword-based constructor builds a tree out of the codewords generated by root-to-leaf paths.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	TreeDecoder.LeafNode A leaf node of the decoding tree.
static class	TreeDecoder.Node A internal node of the decoding tree.

Constructor Summary

Constructors

Constructor and Description
TreeDecoder(BitVector[] lexSortedCodeWord, int[] symbol) Creates a new codeword-based decoder starting from a set of complete, lexicographically ordered codewords.
TreeDecoder(TreeDecoder.Node root, int n) Creates a new codeword-based decoder using the given tree.

Method Summary

Methods

Modifier and Type	Method and Description
BitVector[]	buildCodes() Generate the codewords corresponding to this tree decoder.
int	decode(it.unimi.dsi.fastutil.booleans.BooleanIterator iterator) Decodes the next symbol from the given boolean iterator.
int	decode(InputBitStream ibs) Decodes the next symbol from the given input bit stream.

Methods inherited from class java.lang.Object

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

Constructor Detail

TreeDecoder

public TreeDecoder(TreeDecoder.Node root,
           int n)

Creates a new codeword-based decoder using the given tree. It is responsability of the caller that the tree is well-formed, that is, that all internal nodes are instances of TreeDecoder.Node and all leaf nodes are instances of TreeDecoder.LeafNode.

Parameters:

root - the root of a decoding tree.

n - the number of leaves (symbols).

TreeDecoder

public TreeDecoder(BitVector[] lexSortedCodeWord,
           int[] symbol)

Creates a new codeword-based decoder starting from a set of complete, lexicographically ordered codewords. It is responsability of the caller that the tree is well-formed, that is, that the provided codewords are exactly the root-to-leaf paths of such a tree.

Parameters:

lexSortedCodeWord - a vector of lexically sorted codeWords.

symbol - a mapping from codewords to symbols.

Method Detail

decode

public int decode(it.unimi.dsi.fastutil.booleans.BooleanIterator iterator)

Description copied from interface: Decoder

Decodes the next symbol from the given boolean iterator.

Note that InputBitStream implements BooleanIterator.

Specified by:

decode in interface Decoder

Parameters:

iterator - a boolean iterator.

Returns:

the next symbol decoded from the bits emitted by i

decode

public int decode(InputBitStream ibs)
           throws IOException

Description copied from interface: Decoder

Decodes the next symbol from the given input bit stream.

Note that InputBitStream implements BooleanIterator.

Specified by:

decode in interface Decoder

Parameters:

ibs - an input bit stream.

Returns:

the next symbol decoded from ibs.

Throws:

IOException

buildCodes

public BitVector[] buildCodes()

Generate the codewords corresponding to this tree decoder.

Returns:

a vector of codewords for this decoder.