sandmark.util.graph.codec
Class GraphCodec

java.lang.Object
  |
  +--sandmark.util.graph.codec.GraphCodec

Direct Known Subclasses:

PermutationGraph, PPCT, RadixGraph

public abstract class GraphCodec

extends java.lang.Object

Base-class for watermark encoders/decoders (codecs). Each class in this package should implement sandmark.util.graph.codec.GraphCodec. This entails implementing the encode and decode methods.

To encode an integer into a graph, use the package like this:

    java.math.BigInteger value = ...
    sandmark.util.graph.codec.GraphCodec E = new sandmark.util.graph.codec.RadixGraph(value);
    sandmark.util.graph.Graph graph = E.graph; 
 

To decode a graph into an integer, use the package like this:

    sandmark.util.graph.Graph graph = ...; 
    sandmark.util.graph.Node  root  = ...; 
    int[] kidMap = {1,2};
    sandmark.util.graph.codec.GraphCodec E = new sandmark.util.graph.codec.RadixGraph(graph,root,kidMap);
    sandmark.util.graph.Graph graph = E.graph; 
 

Field Summary

static java.lang.Class[]	codecs
java.lang.String	fullName
Graph	graph
protected int[]	kidMap
(package private) static java.util.Random	random Return a random codec.
protected Node	root
java.lang.String	shortName
java.math.BigInteger	value

Constructor Summary

GraphCodec()

GraphCodec(java.math.BigInteger value)
Constructor to be used when encoding an integer into a graph.

GraphCodec(Graph graph, int[] kidMap)
Constructor to be used when decoding a graph to an integer.

Method Summary

static java.lang.Class	codecByName(java.lang.String name) Return the codec whose name is 'name'.
(package private) abstract void	decode() Codecs should implement this method to convert the 'graph' into 'value'.
(package private) abstract void	encode() Codecs should implement this method to convert the 'value' into 'graph'.
(package private) Node	getKid(Node node, int edgeNumber) Use the kidMap to get the edgeNumber:th child of the node.
static java.lang.Class	randomCodec()

Methods inherited from class java.lang.Object

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

Field Detail

value

public java.math.BigInteger value

graph

public Graph graph

root

protected Node root

kidMap

protected int[] kidMap

fullName

public java.lang.String fullName

shortName

public java.lang.String shortName

codecs

public static java.lang.Class[] codecs

random

static java.util.Random random

Return a random codec.

Constructor Detail

GraphCodec

public GraphCodec()

GraphCodec

public GraphCodec(java.math.BigInteger value)

Constructor to be used when encoding an integer into a graph.

Parameters:

value - The value to be encoded.

GraphCodec

public GraphCodec(Graph graph,
                  int[] kidMap)
           throws DecodeFailure

Constructor to be used when decoding a graph to an integer.

Parameters:

graph - The graph to be decoded.

kidMap - An array of ints describing which field should represent the first child, the second child, etc.

Method Detail

encode

abstract void encode()

Codecs should implement this method to convert the 'value' into 'graph'.

decode

abstract void decode()
              throws DecodeFailure

Codecs should implement this method to convert the 'graph' into 'value'. Whenever the decoding failes (eg. because the graph has the wrong shape) the codec should simply throw an exception.

DecodeFailure

codecByName

public static java.lang.Class codecByName(java.lang.String name)
                                   throws java.lang.Exception

Return the codec whose name is 'name'.

Parameters:

name - The short name of the codec. A java.util.NoSuchElementException is thrown if a codec by this name does not exist.

java.lang.Exception

randomCodec

public static java.lang.Class randomCodec()
                                   throws java.lang.Exception

java.lang.Exception

getKid

Node getKid(Node node,
            int edgeNumber)

Use the kidMap to get the edgeNumber:th child of the node. This is a utility method used by decoders.

Parameters:

node - Look up this node

edgeNumber - The edge number to look up