prefixsubgraph.java

peersim最新版1.0.4

/*
 * Copyright (c) 2003-2005 The BISON Project
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */
		
package peersim.graph;

import java.util.*;

/**
* This class is an adaptor for representing special subgraphs of any graph.
* It can represent the subgraphs spanned by the nodes 0,...,i where
* i is less than or equal to n-1, the last node of the original graph.
* The underlying graph is stored by reference. This means that if the
* graph changes, then these changes will be reflected by this class as well.
* Besides, the size of the prefix can be changed at will at any time
* using {@link #setSize}.
*/
public class PrefixSubGraph implements Graph {


// ====================== private fileds ========================
// ==============================================================


private final Graph g;

/** The graph represents the subgraph defined by nodes 0,...,prefSize */
private int prefSize;


// ====================== public constructors ===================
// ==============================================================


/**
* Constructs an initially max size subgraph of g. That is, the subgraph will
* contain all nodes.
*/
public PrefixSubGraph( Graph g ) {

	this.g = g;
	prefSize = g.size();
}


// ======================= Graph implementations ================
// ==============================================================


public boolean isEdge(int i, int j) {
	
	if( i<0 || i>=prefSize ) throw new IndexOutOfBoundsException();
	if( j<0 || j>=prefSize ) throw new IndexOutOfBoundsException();
	return g.isEdge(i,j);
}

// ---------------------------------------------------------------

public Collection<Integer> getNeighbours(int i) {
	
	if( i<0 || i>=prefSize ) throw new IndexOutOfBoundsException();
	
	List<Integer> result = new LinkedList<Integer>();
	for(Integer j:g.getNeighbours(i))
	{
		if( j < prefSize ) result.add(j);
	}

	return Collections.unmodifiableCollection(result);
}

// ---------------------------------------------------------------

public Object getNode(int i) {

	if( i<0 || i>=prefSize ) throw new IndexOutOfBoundsException();
	return g.getNode(i);
}
	
// ---------------------------------------------------------------

/**
* Returns the edge in the original graph if both i and j are smaller than
* size().
*/
public Object getEdge(int i, int j) {
	
	if( isEdge(i,j) ) return g.getEdge(i,j);
	return null;
}

// --------------------------------------------------------------------

public int size() { return prefSize; }

// --------------------------------------------------------------------
	
public boolean directed() { return g.directed(); }

// --------------------------------------------------------------------

/** not supported */
public boolean setEdge( int i, int j ) {
	
	throw new UnsupportedOperationException();
}

// ---------------------------------------------------------------

/** not supported */
public boolean clearEdge( int i, int j ) {
	
	throw new UnsupportedOperationException();
}

// ---------------------------------------------------------------

public int degree(int i) {

	if( i<0 || i>=prefSize ) throw new IndexOutOfBoundsException();
	return g.degree(i);
}
	

// ================= public functions =================================
// ====================================================================


/**
* Sets the size of the subgraph. If i is negative, it is changed to 0 and
* if it is larger than the underlying graph size, it is changed to the
* underlying graph size (set at construction time).
* @return old size.
*/
public int setSize(int i) {
	
	int was = prefSize;
	if( i < 0 ) i = 0;
	if( i > g.size() ) i=g.size();
	prefSize=i;
	return was;
}
}