package graph;
import java.util.Hashtable;

/**
 * Arbitrate access to attributes in Elements for "hash once"
 * functionality.  Hash once means that there is a global
 * hash table which contains package names.  This is so a
 * package does not need to perform an expensive hashing
 * function in the middle of an inner loop.
 *
 * @see java.util.Hashtable
 * @see Element
 * @author Michael Shilman (michaels@eecs.berkeley.edu)
 * @version $Id$
 */
public class AttributeManager {
	/**
	 * A constant which designates that a particular
	 * package does not yet have a slot in the attribute
	 * table.
	 */
	public static int NO_INDEX = -1;
	
	private static int DEFAULT_NUM_PKG = 5;
    private static Hashtable s_hash = new Hashtable(DEFAULT_NUM_PKG);
    private static int s_numattr = 0;
    private static boolean s_dirty = false;
    
    /**
     * Gets the index of the attribute named by <i>packageName</i>.
     * If <i>packageName</i> doesn't yet have an index, it returns
     * the constant <b>NO_INDEX</b>.
     */
    public static int queryIndex(String packageName) {
        Integer i;
        if((i = (Integer)s_hash.get(packageName)) != null) {
            return i.intValue();
        }
        else {
        	return NO_INDEX;
        }
    }

    /**
     * Gets the index of the attribute named by <i>packageName</i>.
     * If <i>packageName</i> doesn't yet have an index, it creates
     * a new slot for it.
     */
    public static int getIndex(String packageName) {
    	int i;
		if((i = queryIndex(packageName)) != NO_INDEX) {
			return i;
		}
		else {
            Integer ind = new Integer(s_numattr++);
            if((s_numattr % DEFAULT_NUM_PKG) == 0) {
            	//we've just gotten one more than all
            	//our nodes can handle
            	s_dirty = true;
            }
            s_hash.put(packageName, ind);
            return ind.intValue();
        }
    }
    
    /**
     * @return	The number of attribute slots that have currently
     * 			been reserved.
     */
    public static int getNumAttr() {
    	return s_numattr;
    }
    
    /**
     * Obsolete function.
     */
    public static boolean getDirty() {
    	return s_dirty;
    }
}