1/*
2 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package java.util.regex;
27
28import java.util.Arrays;
29
30/**
31 * A lightweight hashset implementation for positive 'int'. Not safe for
32 * concurrent access.
33 */
34class IntHashSet {
35    private int[] entries;
36    private int[] hashes;
37    private int pos = 0;
38
39    public IntHashSet() {
40        this.entries = new int[16 << 1];      // initCapacity = 16;
41        this.hashes = new int[(16 / 2) | 1];  // odd -> fewer collisions
42        Arrays.fill(this.entries, -1);
43        Arrays.fill(this.hashes, -1);
44    }
45
46    public boolean contains(int i) {
47        int h = hashes[i % hashes.length];
48        while (h != -1) {
49            if (entries[h] == i)
50                return true;
51            h = entries[h + 1];
52        }
53        return false;
54    }
55
56    public void add(int i) {
57        int h0 = i % hashes.length;
58        int next = hashes[h0];
59        //  if invoker guarantees contains(i) checked before add(i)
60        //  the following check is not needed.
61        int next0 = next;
62        while (next0 != -1) {
63            if (entries[next0 ] == i)
64                return;
65            next0 = entries[next0 + 1];
66        }
67        hashes[h0] = pos;
68        entries[pos++] = i;
69        entries[pos++] = next;
70        if (pos == entries.length)
71            expand();
72    }
73
74    public void clear() {
75        Arrays.fill(this.entries, -1);
76        Arrays.fill(this.hashes, -1);
77        pos = 0;
78    }
79
80    private void expand() {
81        int[] old = entries;
82        int[] es = new int[old.length << 1];
83        int hlen = (old.length / 2) | 1;
84        int[] hs = new int[hlen];
85        Arrays.fill(es, -1);
86        Arrays.fill(hs, -1);
87        for (int n = 0; n < pos;) {  // re-hashing
88            int i = old[n];
89            int hsh = i % hlen;
90            int next = hs[hsh];
91            hs[hsh] = n;
92            es[n++] = i;
93            es[n++] = next;
94        }
95        this.entries = es;
96        this.hashes = hs;
97    }
98}
99