/* VariableSet Copyright (C) 1998-2002 Jochen Hoenicke.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * 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 General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; see the file COPYING.LESSER.  If not, write to
 * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * $Id$
 */

package net.sf.jode.flow;
import net.sf.jode.decompiler.LocalInfo;
import net.sf.jode.util.ArrayEnum;

///#def COLLECTIONS java.util
import java.util.Collection;
import java.util.AbstractSet;
import java.util.Iterator;
///#enddef

/**
 * This class represents a set of Variables, which are mainly used in
 * the in/out sets of StructuredBlock.  The type of the Variables is
 * LocalInfo. <p>
 *
 * It defines some Helper-Function, like intersecting, merging, union
 * and difference.  <p>
 *
 * Note that a variable set can contain LocalInfos that use the same
 * slot, but are different.
 */
public final class VariableSet extends AbstractSet implements Cloneable {
    LocalInfo[] locals;
    int count;

    /**
     * Creates a new empty variable set
     */
    public VariableSet() {
        locals = null;
        count = 0;
    }

    /**
     * Creates a new pre initialized variable set
     */
    public VariableSet(LocalInfo[] locals) {
        count = locals.length;
        this.locals = locals;
    }

    public final void grow(int size) {
        if (locals != null) {
            size += count;
            if (size > locals.length) {
                int nextSize = locals.length * 2;
//                 GlobalOptions.err.println("wanted: "+size+" next: "+nextSize);
                LocalInfo[] newLocals
                    = new LocalInfo[nextSize > size ? nextSize : size];
                System.arraycopy(locals, 0, newLocals, 0, count);
                locals = newLocals;
            }
        } else if (size > 0)
            locals = new LocalInfo[size];
    }

    /**
     * Adds a local info to this variable set.
     */
    public boolean add(Object li) {
	if (contains(li))
	    return false;
        grow(1);
        locals[count++] = (LocalInfo) li;
	return true;
    }

    /**
     * Checks if the variable set contains the given local info.
     */
    public boolean contains(Object li) {
        li = ((LocalInfo) li).getLocalInfo();
        for (int i=0; i<count;i++)
            if (locals[i].getLocalInfo() == li)
                return true;
        return false;
    }

    /**
     * Checks if the variable set contains a local with the given name.
     */
    public final boolean containsSlot(int slot) {
	return findSlot(slot) != null;
    }

    /**
     * Checks if the variable set contains a local with the given name.
     */
    public LocalInfo findLocal(String name) {
        for (int i=0; i<count;i++)
            if (locals[i].getName().equals(name))
                return locals[i];
        return null;
    }

    /**
     * Checks if the variable set contains a local with the given slot.
     */
    public LocalInfo findSlot(int slot) {
        for (int i=0; i<count;i++)
            if (locals[i].getSlot() == slot)
                return locals[i];
        return null;
    }

    /**
     * Removes a local info from this variable set.  
     */
    public boolean remove(Object li) {
        li = ((LocalInfo) li).getLocalInfo();
        for (int i=0; i<count;i++) {
            if (locals[i].getLocalInfo() == li) {
                locals[i] = locals[--count];
		locals[count] = null;
		return true;
	    }
	}
	return false;
    }

    public int size() {
	return count;
    }

    public Iterator iterator() {
	return new Iterator() {
	    int pos = 0;

	    public boolean hasNext() {
		return pos < count;
	    }
	    
	    public Object next() {
		return locals[pos++];
	    }
	  
	    public void remove() {
		if (pos < count)
		    System.arraycopy(locals, pos, 
				     locals, pos-1, count - pos);
		count--;
		pos--;
		locals[count] = null;
	    }
	};
    }
    
    /**
     * Removes everything from this variable set.  
     */
    public void clear() {
        locals = null;
        count = 0;
    }

    public Object clone() {
        try {
            VariableSet other = (VariableSet) super.clone();
            if (count > 0) {
                other.locals = new LocalInfo[count];
                System.arraycopy(locals, 0, other.locals, 0, count);
            }
            return other;
        } catch (CloneNotSupportedException ex) {
            throw new InternalError("Clone?");
        }
    }

    /**
     * Intersects the current VariableSet with another and returns the
     * intersection.  The existing VariableSet are not changed.  
     * @param vs the other variable set.  
     */
    public VariableSet intersect(VariableSet vs) {
        VariableSet intersection = new VariableSet();
        intersection.grow(Math.min(count, vs.count));
    big_loop:
        for (int i=0; i<count; i++) {
            LocalInfo li = locals[i];
            int slot = li.getSlot();
	    if (vs.containsSlot(slot)
		&& !intersection.containsSlot(slot))
		intersection.locals[intersection.count++] = li.getLocalInfo();
        }
        return intersection;
    }

    /**
     * Add the variables in gen to the current set, unless there are
     * variables in kill using the same slot.
     * @param gen The gen set.
     * @param kill The kill set.
     */
    public void mergeGenKill(Collection gen, SlotSet kill) {
        grow(gen.size());
    big_loop:
        for (Iterator i = gen.iterator(); i.hasNext(); ) {
            LocalInfo li2 = (LocalInfo) i.next();
	    if (!kill.containsSlot(li2.getSlot()))
		add(li2.getLocalInfo());
        }
    }

    /**
     * Merges the localinfo with this gen set and remove all variables
     * that are killed by it. This differs by mergeWrite in that it merges
     * li.
     * @param li the variable to add.  
     */
    public void mergeRead(LocalInfo li) {
	int slot = li.getSlot();
	for (int i=0; i < count; ) {
	    if (locals[i].getSlot() == slot) {
		li.combineWith(locals[i]);
		locals[i] = locals[--count];
	    } else
		i++;
	}
	add(li);
    }

    /**
     * Add li to this gen set and remove all variables that are killed
     * by it.
     * @param li the variable to add.  
     */
    public void mergeWrite(LocalInfo li) {
	int slot = li.getSlot();
	for (int i=0; i < count; ) {
	    if (locals[i].getSlot() == slot)
		locals[i] = locals[--count];
	    else
		i++;
	}
	add(li);
    }
}