ASM: a very small and fast Java bytecode manipulation framework
Copyright (c) 2000-2011 INRIA, France Telecom
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.
3. Neither the name of the copyright holders nor the names of its
   contributors may be used to endorse or promote products derived from
   this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2011 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.objectweb.asm.tree.analysis;

import java.util.AbstractSet;
import java.util.HashSet;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;

A set of at most two elements.
Author:
Eric Bruneton/**
 * A set of at most two elements.
 * 
 * @author Eric Bruneton
 */
class SmallSet<E> extends AbstractSet<E> implements Iterator<E> {

    // if e1 is null, e2 must be null; otherwise e2 must be different from e1

    E e1, e2;

    static final <T> Set<T> emptySet() {
        return new SmallSet<T>(null, null);
    }

    SmallSet(final E e1, final E e2) {
        this.e1 = e1;
        this.e2 = e2;
    }

    // -------------------------------------------------------------------------
    // Implementation of inherited abstract methods
    // -------------------------------------------------------------------------

    @Override
    public Iterator<E> iterator() {
        return new SmallSet<E>(e1, e2);
    }

    @Override
    public int size() {
        return e1 == null ? 0 : (e2 == null ? 1 : 2);
    }

    // -------------------------------------------------------------------------
    // Implementation of the Iterator interface
    // -------------------------------------------------------------------------

    public boolean hasNext() {
        return e1 != null;
    }

    public E next() {
        if (e1 == null) {
            throw new NoSuchElementException();
        }
        E e = e1;
        e1 = e2;
        e2 = null;
        return e;
    }

    public void remove() {
    }

    // -------------------------------------------------------------------------
    // Utility methods
    // -------------------------------------------------------------------------

    Set<E> union(final SmallSet<E> s) {
        if ((s.e1 == e1 && s.e2 == e2) || (s.e1 == e2 && s.e2 == e1)) {
            return this; // if the two sets are equal, return this
        }
        if (s.e1 == null) {
            return this; // if s is empty, return this
        }
        if (e1 == null) {
            return s; // if this is empty, return s
        }
        if (s.e2 == null) { // s contains exactly one element
            if (e2 == null) {
                return new SmallSet<E>(e1, s.e1); // necessarily e1 != s.e1
            } else if (s.e1 == e1 || s.e1 == e2) { // s is included in this
                return this;
            }
        }
        if (e2 == null) { // this contains exactly one element
            // if (s.e2 == null) { // cannot happen
            // return new SmallSet(e1, s.e1); // necessarily e1 != s.e1
            // } else
            if (e1 == s.e1 || e1 == s.e2) { // this in included in s
                return s;
            }
        }
        // here we know that there are at least 3 distinct elements
        HashSet<E> r = new HashSet<E>(4);
        r.add(e1);
        if (e2 != null) {
            r.add(e2);
        }
        r.add(s.e1);
        if (s.e2 != null) {
            r.add(s.e2);
        }
        return r;
    }
}