rev 6218 : imported patch smallset

   1 /*
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  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).
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  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
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  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.Objects;
  66 import java.util.Set;
  67 import java.util.function.Block;
  68 
  69 /**
  70  * A set of at most two elements.
  71  *
  72  * @author Eric Bruneton
  73  */
  74 class SmallSet<E> extends AbstractSet<E> implements Iterator<E> {
  75 
  76     // if e1 is null, e2 must be null; otherwise e2 must be different from e1
  77 
  78     E e1, e2;
  79 
  80     static final <T> Set<T> emptySet() {
  81         return new SmallSet<T>(null, null);
  82     }
  83 
  84     SmallSet(final E e1, final E e2) {
  85         this.e1 = e1;
  86         this.e2 = e2;
  87     }
  88 
  89     // -------------------------------------------------------------------------
  90     // Implementation of inherited abstract methods
  91     // -------------------------------------------------------------------------
  92 
  93     @Override
  94     public Iterator<E> iterator() {
  95         return new SmallSet<E>(e1, e2);
  96     }
  97 
  98     @Override
  99     public int size() {
 100         return e1 == null ? 0 : (e2 == null ? 1 : 2);
 101     }
 102 
 103     // -------------------------------------------------------------------------
 104     // Implementation of the Iterator interface
 105     // -------------------------------------------------------------------------
 106 
 107     public boolean hasNext() {
 108         return e1 != null;
 109     }
 110 
 111     public E next() {
 112         if (e1 == null) {
 113             throw new NoSuchElementException();
 114         }
 115         E e = e1;
 116         e1 = e2;
 117         e2 = null;
 118         return e;
 119     }
 120 
 121     public void remove() {
 122     }
 123 
 124     // -------------------------------------------------------------------------
 125     // Utility methods
 126     // -------------------------------------------------------------------------
 127 
 128     Set<E> union(final SmallSet<E> s) {
 129         if ((s.e1 == e1 && s.e2 == e2) || (s.e1 == e2 && s.e2 == e1)) {
 130             return this; // if the two sets are equal, return this
 131         }
 132         if (s.e1 == null) {
 133             return this; // if s is empty, return this
 134         }
 135         if (e1 == null) {
 136             return s; // if this is empty, return s
 137         }
 138         if (s.e2 == null) { // s contains exactly one element
 139             if (e2 == null) {
 140                 return new SmallSet<E>(e1, s.e1); // necessarily e1 != s.e1
 141             } else if (s.e1 == e1 || s.e1 == e2) { // s is included in this
 142                 return this;
 143             }
 144         }
 145         if (e2 == null) { // this contains exactly one element
 146             // if (s.e2 == null) { // cannot happen
 147             // return new SmallSet(e1, s.e1); // necessarily e1 != s.e1
 148             // } else
 149             if (e1 == s.e1 || e1 == s.e2) { // this in included in s
 150                 return s;
 151             }
 152         }
 153         // here we know that there are at least 3 distinct elements
 154         HashSet<E> r = new HashSet<E>(4);
 155         r.add(e1);
 156         if (e2 != null) {
 157             r.add(e2);
 158         }
 159         r.add(s.e1);
 160         if (s.e2 != null) {
 161             r.add(s.e2);
 162         }
 163         return r;
 164     }
 165 
 166     @Override
 167     public void forEach(Block<? super E> block) {
 168         Objects.requireNonNull(block);
 169         if (e1 != null) {
 170             block.accept(e1);
 171             if (e2 != null) {
 172                 block.accept(e2);
 173             }
 174         }
 175     }
 176 }
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