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// Copyright 2022 Google LLC
//
// Licensed 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
//
// https://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 com.google.setfilters.cuckoofilter;
import java.nio.ByteBuffer;
import java.util.Optional;
import java.util.Random;
/** An array of buckets where each bucket can store a fixed number of fingerprints. */
interface CuckooFilterTable {
/** Value of the empty "slot", which is reserved as 0. */
public static long EMPTY_SLOT = 0L;
/**
* Creates an implementation of an empty cuckoo filter based on whether space optimization should
* be used.
*
* <p>Space optimization is best effort, and is not guaranteed.
*/
public static CuckooFilterTable create(
CuckooFilterConfig.Size size, boolean useSpaceOptimization, Random random) {
if (useSpaceOptimization && size.bucketCapacity() == 4 && size.fingerprintLength() >= 4) {
return new SemiSortedCuckooFilterTable(size, random);
}
return new UncompressedCuckooFilterTable(size, random);
}
/** Creates an implementation of the cuckoo filter based on the serialization. */
public static CuckooFilterTable createFromSerialization(
SerializedCuckooFilterTable serializedTable, Random random) {
ByteBuffer buffer = ByteBuffer.wrap(serializedTable.asByteArray());
if (buffer.remaining() <= 16) {
throw new IllegalArgumentException("Unable to parse the SerializedCuckooFilterTable.");
}
int tableType = buffer.getInt();
int bucketCount = buffer.getInt();
int bucketCapacity = buffer.getInt();
int fingerprintLength = buffer.getInt();
CuckooFilterConfig.Size size =
CuckooFilterConfig.Size.newBuilder()
.setBucketCount(bucketCount)
.setBucketCapacity(bucketCapacity)
.setFingerprintLength(fingerprintLength)
.build();
byte[] bitArray = new byte[buffer.remaining()];
buffer.get(bitArray);
if (tableType == UncompressedCuckooFilterTable.TABLE_TYPE) {
return new UncompressedCuckooFilterTable(size, bitArray, random);
} else if (tableType == SemiSortedCuckooFilterTable.TABLE_TYPE) {
return new SemiSortedCuckooFilterTable(size, bitArray, random);
} else {
throw new IllegalArgumentException("Unable to parse the SerializedCuckooFilterTable.");
}
}
/**
* Inserts given {@code fingerprint} to the {@code bucketIndex}th bucket, replacing an arbitrary
* fingerprint if the bucket is full.
*
* <p>How this arbitrary fingerprint is chosen depends on the implementation.
*
* @return the value of the replaced fingerprint if the bucket is full, and an empty {@link
* Optional} otherwise.
*/
Optional<Long> insertWithReplacement(int bucketIndex, long fingerprint);
/** Returns whether {@code bucketIndex}th bucket contains {@code fingerprint}. */
boolean contains(int bucketIndex, long fingerprint);
/**
* Deletes a {@code fingerprint} from {@code bucketIndex}th bucket.
*
* <p>If a bucket contains multiple {@code fingerprint} values, this method only deletes one.
*
* @return {@code true} if {@code fingerprint} is in {@code bucketIndex}th bucket and is deleted,
* and {@code false} otherwise.
*/
boolean delete(int bucketIndex, long fingerprint);
/** Returns whether {@code bucketIndex}th bucket is full. */
boolean isFull(int bucketIndex);
/** Returns the size of {@link CuckooFilterTable}. */
CuckooFilterConfig.Size size();
/** Returns serialization of {@link CuckooFilterTable}. */
SerializedCuckooFilterTable serialize();
// TODO: Add more methods as needed.
}
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