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A Java Optimization Framework
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/* Soot - a J*va Optimization Framework
 * Copyright (C) 2003 Ondrej Lhotak
 *
 * This library 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 2.1 of the License, or (at your option) any later version.
 *
 * This library 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 library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

package soot.util.queue;

/** Similar to ChunkedQueue, but implemented using BDDs. A BDDQueue represents
 * a sequence of BDDs. Each reader points to some BDD in the sequence, and
 * can read the current BDD and ones that come after it in sequence. If at
 * any point, a BDD in the sequence no longer has a reader pointing to it,
 * it is unioned into the preceding BDD (if any) and removed from the sequence.
 * Only BDDs that have not been read by all the readers
 * are kept. A reader can only read the BDDs added to the queue
 * after the reader was created.
 * @author Ondrej Lhotak
 */

public class BDDReader implements Cloneable {
    BDDChunk chunk;
    BDDQueue q;
    BDDReader( BDDQueue q ) {
        this.q = q;
        chunk = q.newChunk();
    }
    public <> next() {
        <> ret;
        do {
            ret = chunk.bdd;
            chunk = chunk.next;
            if( chunk == null ) chunk = q.newChunk();
        } while( ret == 0B && chunk.next != null );
        return ret;
    }
    public boolean hasNext() {
        while( chunk.bdd == 0B && chunk.next != null ) chunk = chunk.next;
        return chunk.bdd != 0B;
    }
    private BDDReader( BDDQueue q, BDDChunk chunk ) {
        this.q = q;
        this.chunk = chunk;
    }
    public Object clone() {
        return new BDDReader(q, chunk);
    }
}