package org.apache.cassandra.utils;
import java.io.DataInput;
import java.io.IOException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.io.util.DataOutputPlus;
import org.apache.cassandra.utils.obs.IBitSet;
import org.apache.cassandra.utils.obs.OffHeapBitSet;
import org.apache.cassandra.utils.obs.OpenBitSet;
public class FilterFactory
{
public static final IFilter AlwaysPresent = new AlwaysPresentFilter();
private static final Logger logger = LoggerFactory.getLogger(FilterFactory.class);
private static final long BITSET_EXCESS = 20;
public static void serialize(IFilter bf, DataOutputPlus output) throws IOException
{
BloomFilterSerializer.serialize((BloomFilter) bf, output);
}
public static IFilter deserialize(DataInput input, boolean offheap, boolean oldBfHashOrder) throws IOException
{
return BloomFilterSerializer.deserialize(input, offheap, oldBfHashOrder);
}
public static IFilter getFilter(long numElements, int targetBucketsPerElem, boolean offheap, boolean oldBfHashOrder)
{
int maxBucketsPerElement = Math.max(1, BloomCalculations.maxBucketsPerElement(numElements));
int bucketsPerElement = Math.min(targetBucketsPerElem, maxBucketsPerElement);
if (bucketsPerElement < targetBucketsPerElem)
{
logger.warn("Cannot provide an optimal BloomFilter for {} elements ({}/{} buckets per element).", numElements, bucketsPerElement, targetBucketsPerElem);
}
BloomCalculations.BloomSpecification spec = BloomCalculations.computeBloomSpec(bucketsPerElement);
return createFilter(spec.K, numElements, spec.bucketsPerElement, offheap, oldBfHashOrder);
}
public static IFilter getFilter(long numElements, double maxFalsePosProbability, boolean offheap, boolean oldBfHashOrder)
{
assert maxFalsePosProbability <= 1.0 : "Invalid probability";
if (maxFalsePosProbability == 1.0)
return new AlwaysPresentFilter();
int bucketsPerElement = BloomCalculations.maxBucketsPerElement(numElements);
BloomCalculations.BloomSpecification spec = BloomCalculations.computeBloomSpec(bucketsPerElement, maxFalsePosProbability);
return createFilter(spec.K, numElements, spec.bucketsPerElement, offheap, oldBfHashOrder);
}
@SuppressWarnings("resource")
private static IFilter createFilter(int hash, long numElements, int bucketsPer, boolean offheap, boolean oldBfHashOrder)
{
long numBits = (numElements * bucketsPer) + BITSET_EXCESS;
IBitSet bitset = offheap ? new OffHeapBitSet(numBits) : new OpenBitSet(numBits);
return new BloomFilter(hash, bitset, oldBfHashOrder);
}
}