1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /*
26 * This file is available under and governed by the GNU General Public
27 * License version 2 only, as published by the Free Software Foundation.
28 * However, the following notice accompanied the original version of this
29 * file:
30 *
31 * ASM: a very small and fast Java bytecode manipulation framework
32 * Copyright (c) 2000-2011 INRIA, France Telecom
33 * All rights reserved.
34 *
35 * Redistribution and use in source and binary forms, with or without
36 * modification, are permitted provided that the following conditions
37 * are met:
38 * 1. Redistributions of source code must retain the above copyright
39 * notice, this list of conditions and the following disclaimer.
40 * 2. Redistributions in binary form must reproduce the above copyright
41 * notice, this list of conditions and the following disclaimer in the
42 * documentation and/or other materials provided with the distribution.
43 * 3. Neither the name of the copyright holders nor the names of its
44 * contributors may be used to endorse or promote products derived from
45 * this software without specific prior written permission.
46 *
47 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
48 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
49 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
50 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
51 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
52 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
53 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
54 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
55 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
56 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
57 * THE POSSIBILITY OF SUCH DAMAGE.
58 */
59 package jdk.internal.org.objectweb.asm.tree.analysis;
60
61 import java.util.AbstractSet;
62 import java.util.HashSet;
63 import java.util.Iterator;
64 import java.util.NoSuchElementException;
65 import java.util.Set;
66
67 /**
68 * A set of at most two elements.
69 *
70 * @author Eric Bruneton
71 */
72 class SmallSet<E> extends AbstractSet<E> implements Iterator<E> {
73
74 // if e1 is null, e2 must be null; otherwise e2 must be different from e1
75
76 E e1, e2;
77
78 static final <T> Set<T> emptySet() {
79 return new SmallSet<T>(null, null);
80 }
81
82 SmallSet(final E e1, final E e2) {
83 this.e1 = e1;
84 this.e2 = e2;
85 }
86
87 // -------------------------------------------------------------------------
88 // Implementation of inherited abstract methods
89 // -------------------------------------------------------------------------
90
91 @Override
92 public Iterator<E> iterator() {
93 return new SmallSet<E>(e1, e2);
94 }
95
96 @Override
97 public int size() {
98 return e1 == null ? 0 : (e2 == null ? 1 : 2);
99 }
100
101 // -------------------------------------------------------------------------
102 // Implementation of the Iterator interface
103 // -------------------------------------------------------------------------
104
105 public boolean hasNext() {
106 return e1 != null;
107 }
108
109 public E next() {
110 if (e1 == null) {
111 throw new NoSuchElementException();
112 }
113 E e = e1;
114 e1 = e2;
115 e2 = null;
116 return e;
117 }
118
119 public void remove() {
120 }
121
122 // -------------------------------------------------------------------------
123 // Utility methods
124 // -------------------------------------------------------------------------
125
126 Set<E> union(final SmallSet<E> s) {
127 if ((s.e1 == e1 && s.e2 == e2) || (s.e1 == e2 && s.e2 == e1)) {
128 return this; // if the two sets are equal, return this
129 }
130 if (s.e1 == null) {
131 return this; // if s is empty, return this
132 }
133 if (e1 == null) {
134 return s; // if this is empty, return s
135 }
136 if (s.e2 == null) { // s contains exactly one element
137 if (e2 == null) {
138 return new SmallSet<E>(e1, s.e1); // necessarily e1 != s.e1
139 } else if (s.e1 == e1 || s.e1 == e2) { // s is included in this
140 return this;
141 }
142 }
143 if (e2 == null) { // this contains exactly one element
144 // if (s.e2 == null) { // cannot happen
145 // return new SmallSet(e1, s.e1); // necessarily e1 != s.e1
146 // } else
147 if (e1 == s.e1 || e1 == s.e2) { // this in included in s
148 return s;
149 }
150 }
151 // here we know that there are at least 3 distinct elements
152 HashSet<E> r = new HashSet<E>(4);
153 r.add(e1);
154 if (e2 != null) {
155 r.add(e2);
156 }
157 r.add(s.e1);
158 if (s.e2 != null) {
159 r.add(s.e2);
160 }
161 return r;
162 }
163 }