import java.util.Hashtable;
import java.util.Vector;

/**
 * SymbolTable implementation using two Hashtables,
 * one for forward lookup and one for reverse.
 */
public class SamSymbolTable implements SymbolTable, java.io.Serializable {
	protected Hashtable sym2adr = new Hashtable();
	protected Hashtable adr2sym = new Hashtable();

	public void add(String symbol, int address) {
		Integer adr = new Integer(address);
		sym2adr.put(symbol, adr);
	
		Vector v;
		if (adr2sym.containsKey(adr)) {
			v = (Vector) adr2sym.get(adr);
			if (v.contains(symbol) == false)
				v.add(symbol);
		}

		else {
			v = new Vector();
			v.add(symbol);
			adr2sym.put(adr, v); 
		}
	}

	public String[] resolveSymbols(int address) {
		Vector labels = (Vector) adr2sym.get(new Integer(address));
		return (labels != null) ? ((String []) labels.toArray())  : null;
	}
	
	public String resolveSymbol(int address){
		Vector labels = (Vector)adr2sym.get(new Integer(address));
		return (labels != null)?(String)labels.get(0):null;
	}

	public int resolveAddress(String label) {
		Object addr = sym2adr.get(label);
		return (addr != null) ? ((Integer)addr).intValue() : -1;
	}

	public String toString() 
		{ return sym2adr.toString(); }
}