SmallSet.java revision 674060f01e9090cd21b3c5656cc3204912ad17a6 
1/***
2 * ASM: a very small and fast Java bytecode manipulation framework
3 * Copyright (c) 2000-2007 INRIA, France Telecom
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of the copyright holders nor the names of its
15 *    contributors may be used to endorse or promote products derived from
16 *    this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
19 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
22 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
23 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
24 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
25 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
26 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
27 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
28 * THE POSSIBILITY OF SUCH DAMAGE.
29 */
30package org.mockito.asm.tree.analysis;
31
32import java.util.AbstractSet;
33import java.util.HashSet;
34import java.util.Iterator;
35import java.util.Set;
36
37/**
38 * A set of at most two elements.
39 *
40 * @author Eric Bruneton
41 */
42class SmallSet extends AbstractSet implements Iterator {
43
44    // if e1 is null, e2 must be null; otherwise e2 must be different from e1
45
46    Object e1, e2;
47
48    static final Set EMPTY_SET = new SmallSet(null, null);
49
50    SmallSet(final Object e1, final Object e2) {
51        this.e1 = e1;
52        this.e2 = e2;
53    }
54
55    // -------------------------------------------------------------------------
56    // Implementation of inherited abstract methods
57    // -------------------------------------------------------------------------
58
59    public Iterator iterator() {
60        return new SmallSet(e1, e2);
61    }
62
63    public int size() {
64        return e1 == null ? 0 : (e2 == null ? 1 : 2);
65    }
66
67    // -------------------------------------------------------------------------
68    // Implementation of the Iterator interface
69    // -------------------------------------------------------------------------
70
71    public boolean hasNext() {
72        return e1 != null;
73    }
74
75    public Object next() {
76        Object e = e1;
77        e1 = e2;
78        e2 = null;
79        return e;
80    }
81
82    public void remove() {
83    }
84
85    // -------------------------------------------------------------------------
86    // Utility methods
87    // -------------------------------------------------------------------------
88
89    Set union(final SmallSet s) {
90        if ((s.e1 == e1 && s.e2 == e2) || (s.e1 == e2 && s.e2 == e1)) {
91            return this; // if the two sets are equal, return this
92        }
93        if (s.e1 == null) {
94            return this; // if s is empty, return this
95        }
96        if (e1 == null) {
97            return s; // if this is empty, return s
98        }
99        if (s.e2 == null) { // s contains exactly one element
100            if (e2 == null) {
101                return new SmallSet(e1, s.e1); // necessarily e1 != s.e1
102            } else if (s.e1 == e1 || s.e1 == e2) { // s is included in this
103                return this;
104            }
105        }
106        if (e2 == null) { // this contains exactly one element
107            // if (s.e2 == null) { // cannot happen
108            // return new SmallSet(e1, s.e1); // necessarily e1 != s.e1
109            // } else
110            if (e1 == s.e1 || e1 == s.e2) { // this in included in s
111                return s;
112            }
113        }
114        // here we know that there are at least 3 distinct elements
115        HashSet r = new HashSet(4);
116        r.add(e1);
117        if (e2 != null) {
118            r.add(e2);
119        }
120        r.add(s.e1);
121        if (s.e2 != null) {
122            r.add(s.e2);
123        }
124        return r;
125    }
126}
127