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author | Lukas Stadler <lukas.stadler@jku.at> |
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date | Fri, 06 May 2011 10:25:37 +0200 |
parents | 16b9a8b5ad39 |
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/* * Copyright (c) 2009, 2010, 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. * * 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 com.sun.c1x.util; /** * The {@code ArrayMap} class implements an efficient one-level map which is implemented * as an array. Note that because of the one-level array inside, this data structure performs best * when the range of integer keys is small and densely used. Note that the implementation can * handle arbitrary intervals, including negative numbers, up to intervals of size 2^31 - 1. * * @author Ben L. Titzer */ public class ArrayMap<T> { private static final int INITIAL_SIZE = 5; // how big the initial array should be private static final int EXTRA = 2; // how far on the left or right of a new element to grow Object[] map; int low; /** * Constructs a new {@code ArrayMap} with no initial assumptions. */ public ArrayMap() { } /** * Constructs a new {@code ArrayMap} that initially covers the specified interval. * Note that this map will automatically expand if necessary later. * @param low the low index, inclusive * @param high the high index, exclusive */ public ArrayMap(int low, int high) { this.low = low; this.map = new Object[high - low + 1]; } /** * Puts a new value in the map at the specified index. * @param i the index at which to store the value * @param value the value to store at the specified index */ public void put(int i, T value) { int index = i - low; if (map == null) { // no map yet map = new Object[INITIAL_SIZE]; low = index - 2; map[INITIAL_SIZE / 2] = value; } else if (index < 0) { // grow backwards growBackward(i, value); } else if (index >= map.length) { // grow forwards growForward(i, value); } else { // no growth necessary map[index] = value; } } /** * Gets the value at the specified index in the map. * @param i the index * @return the value at the specified index; {@code null} if there is no value at the specified index, * or if the index is out of the currently stored range */ public T get(int i) { int index = i - low; if (map == null || index < 0 || index >= map.length) { return null; } Class<T> type = null; return Util.uncheckedCast(type, map[index]); } public int length() { return map.length; } private void growBackward(int i, T value) { int nlow = i - EXTRA; Object[] nmap = new Object[low - nlow + map.length]; System.arraycopy(map, 0, nmap, low - nlow, map.length); map = nmap; low = nlow; map[i - low] = value; } private void growForward(int i, T value) { int nlen = i - low + 1 + EXTRA; Object[] nmap = new Object[nlen]; System.arraycopy(map, 0, nmap, 0, map.length); map = nmap; map[i - low] = value; } }