org.apache.spark.util.sketch.BitArray Maven / Gradle / Ivy
/*
* 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 java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.Arrays;
final class BitArray {
private final long[] data;
private long bitCount;
static int numWords(long numBits) {
if (numBits <= 0) {
throw new IllegalArgumentException("numBits must be positive, but got " + numBits);
}
long numWords = (long) Math.ceil(numBits / 64.0);
if (numWords > Integer.MAX_VALUE) {
throw new IllegalArgumentException("Can't allocate enough space for " + numBits + " bits");
}
return (int) numWords;
}
BitArray(long numBits) {
this(new long[numWords(numBits)]);
}
private BitArray(long[] data) {
this.data = data;
long bitCount = 0;
for (long word : data) {
bitCount += Long.bitCount(word);
}
this.bitCount = bitCount;
}
/** Returns true if the bit changed value. */
boolean set(long index) {
if (!get(index)) {
data[(int) (index >>> 6)] |= (1L << index);
bitCount++;
return true;
}
return false;
}
boolean get(long index) {
return (data[(int) (index >>> 6)] & (1L << index)) != 0;
}
/** Number of bits */
long bitSize() {
return (long) data.length * Long.SIZE;
}
/** Number of set bits (1s) */
long cardinality() {
return bitCount;
}
/** Combines the two BitArrays using bitwise OR. */
void putAll(BitArray array) {
assert data.length == array.data.length : "BitArrays must be of equal length when merging";
long bitCount = 0;
for (int i = 0; i < data.length; i++) {
data[i] |= array.data[i];
bitCount += Long.bitCount(data[i]);
}
this.bitCount = bitCount;
}
void writeTo(DataOutputStream out) throws IOException {
out.writeInt(data.length);
for (long datum : data) {
out.writeLong(datum);
}
}
static BitArray readFrom(DataInputStream in) throws IOException {
int numWords = in.readInt();
long[] data = new long[numWords];
for (int i = 0; i < numWords; i++) {
data[i] = in.readLong();
}
return new BitArray(data);
}
@Override
public boolean equals(Object other) {
if (this == other) return true;
if (other == null || !(other instanceof BitArray)) return false;
BitArray that = (BitArray) other;
return Arrays.equals(data, that.data);
}
@Override
public int hashCode() {
return Arrays.hashCode(data);
}
}