/*
 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.util.regex;

import java.util.Arrays;

A lightweight hashset implementation for positive 'int'. Not safe for concurrent access.
/** * A lightweight hashset implementation for positive 'int'. Not safe for * concurrent access. */
class IntHashSet { private int[] entries; private int[] hashes; private int pos = 0; public IntHashSet() { this.entries = new int[16 << 1]; // initCapacity = 16; this.hashes = new int[(16 / 2) | 1]; // odd -> fewer collisions Arrays.fill(this.entries, -1); Arrays.fill(this.hashes, -1); } public boolean contains(int i) { int h = hashes[i % hashes.length]; while (h != -1) { if (entries[h] == i) return true; h = entries[h + 1]; } return false; } public void add(int i) { int h0 = i % hashes.length; int next = hashes[h0]; // if invoker guarantees contains(i) checked before add(i) // the following check is not needed. int next0 = next; while (next0 != -1) { if (entries[next0 ] == i) return; next0 = entries[next0 + 1]; } hashes[h0] = pos; entries[pos++] = i; entries[pos++] = next; if (pos == entries.length) expand(); } public void clear() { Arrays.fill(this.entries, -1); Arrays.fill(this.hashes, -1); pos = 0; } private void expand() { int[] old = entries; int[] es = new int[old.length << 1]; int hlen = (old.length / 2) | 1; int[] hs = new int[hlen]; Arrays.fill(es, -1); Arrays.fill(hs, -1); for (int n = 0; n < pos;) { // re-hashing int i = old[n]; int hsh = i % hlen; int next = hs[hsh]; hs[hsh] = n; es[n++] = i; es[n++] = next; } this.entries = es; this.hashes = hs; } }