basicblock.java

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/*
 * BasicBlock.java
 *
 * Created on July 24, 2001, 7:20 AM
 *
 * See LICENSE file for license conditions.
 */

package residue.graph;

import java.util.*;

/**
 * This class represents a basic block in the flow control graph,
 * as an adjacent, ordered, series of Nodes.
 *
 * @author  chowells
 * @version 
 */
public class BasicBlock implements Observer
{
	private List nodes = new ArrayList();
	
	private Set edges = new HashSet();
	private Set lines = new TreeSet();
	
	private int pos = -1;
	
	private int incomingEdges;
	
	public void add(Node n)
	{
		if (pos == -1)
			pos = n.getPosition();
		nodes.add(n);
		
		Iterator it = n.getEdges().iterator();
		while (it.hasNext())
		{
			Node t = (Node)it.next();
			BasicBlock bb = t.getBlock();
			
			if (bb == this) continue;
			if (bb == null) t.addObserver(this);
			else
			{
				if (edges.add(bb)) bb.incomingEdges++;
			}
		} // while
		
		lines.add(new Integer(n.getLine()));
		n.setBlock(this);
	} // add
	
	public Set getLines()
	{
		return Collections.unmodifiableSet(lines);
	} // getLines
	
	public Set getEdges()
	{
		return Collections.unmodifiableSet(edges);
	} // getEdges
	
	/**
	 * package visible mutator for edges, used by
	 * reverse() in graph.
	 */
	void setEdges(Set s)
	{
		edges = s;
	} // setEdges
	
	public int getPosition()
	{
		return pos;
	} // getPosition
	
	public int getIncomingEdgeCount()
	{
		return incomingEdges;
	} // getIncomingEdgeCount
	
	public Node getFirstNode()
	{
		return (Node)nodes.get(0);
	} // getFirstNode
	
	public Node getLastNode()
	{
		return (Node)nodes.get(nodes.size() - 1);
	} // getLastNode
	
	/**
	 * This method overrides update in the Observer interface.
	 * The object it expects to get is a BasicBlock to include
	 * in its internal set of edges.  If it doesn't get a
	 * BasicBlock, it throws a ClassCastException
	 */
	public void update(Observable observable, Object obj)
	{
		if (obj != this)
		{
			BasicBlock b = (BasicBlock)obj; 
			if (edges.add(b)) b.incomingEdges++;
		}
		
		observable.deleteObserver(this);
	} // update
	
} // BasicBlock