Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/15917#discussion_r88455531
--- Diff:
common/sketch/src/main/java/org/apache/spark/util/sketch/RoaringBitmapArray.java
---
@@ -0,0 +1,136 @@
+/*
+ * 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.spark.util.sketch;
+
+import org.roaringbitmap.RoaringBitmap;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.Arrays;
+
+class RoaringBitmapArray {
+
+ private final RoaringBitmap[] data;
+ private long bitCount; // number of 1`s in bitset
+ private final long numBits; // total number of available bits
+
+ private static int numOfBuckets(long numBits) {
+ if (numBits <= 0) {
+ throw new IllegalArgumentException("numBits must be positive,
but got " + numBits);
+ }
+ return (int) Math.ceil(numBits / (double)Integer.MAX_VALUE);
+ }
+
+ private static RoaringBitmap[] initialVector(int numOfBuckets){
+ RoaringBitmap[] vector = new RoaringBitmap[numOfBuckets];
+ for(int i = 0;i<numOfBuckets;i++){
+ vector[i] = new RoaringBitmap();
+ }
+ return vector;
+ }
+
+ RoaringBitmapArray(long numBits) {
+ this(initialVector(numOfBuckets(numBits)), numBits);
+ }
+
+ private RoaringBitmapArray(RoaringBitmap[] data, long numBits) {
+ this.data = data;
+ this.numBits = numBits;
+ long bitCount = 0;
+ for (RoaringBitmap bucket : data) {
+ bitCount += bucket.getCardinality();
+ }
+ this.bitCount = bitCount;
+ }
+
+ /** Returns true if the bit changed value. */
+ boolean set(long index) {
+ int bucketNum = (int)(index / Integer.MAX_VALUE);
+ int bitIdx = (int)(index % Integer.MAX_VALUE);
+ if(!data[bucketNum].contains(bitIdx)) {
+ data[bucketNum].add(bitIdx);
+ bitCount++;
+ return true;
+ }
+ return false;
+ }
+
+ boolean get(long index) {
+ int bucketNum = (int)(index / Integer.MAX_VALUE);
+ int bitIdx = (int) (index % Integer.MAX_VALUE);
+ return data[bucketNum].contains(bitIdx);
+ }
+
+ /** Number of bits */
+ long bitSize() {
+ return numBits;
--- End diff --
2 space indent everywhere
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