| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.giraph.utils; |
| |
| import java.util.BitSet; |
| |
| /** |
| * Bit set optimized for increasing longs to save storage space. |
| * The general idea is that even though some keys will be added out-of-order, |
| * there is a base key that keeps increasing so that the bit set doesn't get |
| * very big. When there are enough set bits, the bit set gets compacted. |
| * Thread-safe. |
| */ |
| public class IncreasingBitSet { |
| /** Minimum number of bits to shift */ |
| public static final int MIN_BITS_TO_SHIFT = 64 * 1024; |
| /** Bit set used */ |
| private BitSet bitSet = new BitSet(); |
| /** Last base key (all keys < this have been accepted */ |
| private long lastBaseKey = 0; |
| |
| /** |
| * Add a key if it is possible. |
| * |
| * @param key Key to add |
| * @return True if the key was added, false otherwise |
| */ |
| public synchronized boolean add(long key) { |
| long remainder = key - lastBaseKey; |
| checkLegalKey(remainder); |
| |
| if (remainder < 0) { |
| return false; |
| } |
| if (bitSet.get((int) remainder)) { |
| return false; |
| } |
| bitSet.set((int) remainder); |
| int nextClearBit = bitSet.nextClearBit(0); |
| if (nextClearBit >= MIN_BITS_TO_SHIFT) { |
| bitSet = bitSet.get(nextClearBit, |
| Math.max(nextClearBit, bitSet.length())); |
| lastBaseKey += nextClearBit; |
| } |
| return true; |
| } |
| |
| /** |
| * Get the number of set bits |
| * |
| * @return Number of set bits |
| */ |
| public synchronized long cardinality() { |
| long size = bitSet.cardinality(); |
| return size + lastBaseKey; |
| } |
| |
| /** |
| * Get the size of the bit set |
| * |
| * @return Size of the bit set |
| */ |
| public synchronized int size() { |
| return bitSet.size(); |
| } |
| |
| /** |
| * Check for existence of a key |
| * |
| * @param key Key to check for |
| * @return True if the key exists, false otherwise |
| */ |
| public synchronized boolean has(long key) { |
| long remainder = key - lastBaseKey; |
| checkLegalKey(remainder); |
| |
| if (remainder < 0) { |
| return true; |
| } |
| return bitSet.get((int) remainder); |
| } |
| |
| /** |
| * Get the last base key (mainly for debugging). |
| * |
| * @return Last base key |
| */ |
| public synchronized long getLastBaseKey() { |
| return lastBaseKey; |
| } |
| |
| /** |
| * Check the remainder for validity |
| * |
| * @param remainder Remainder to check |
| */ |
| private void checkLegalKey(long remainder) { |
| if (remainder > Integer.MAX_VALUE) { |
| throw new IllegalArgumentException( |
| "checkLegalKey: Impossible that to add key " + |
| (remainder + lastBaseKey) + " with base " + |
| lastBaseKey + " since the " + |
| "spread is too large (> " + Integer.MAX_VALUE); |
| } |
| } |
| } |