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Apache Geode provides a database-like consistency model, reliable transaction processing and a shared-nothing architecture to maintain very low latency performance with high concurrency processing

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/*
 * Copyright (C) 2011 Clearspring Technologies, Inc.
 *
 * 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
 *
 * 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.geode.internal.hll;


import java.io.IOException;


public interface ICardinality {

  /**
   * @param o stream element
   * @return false if the value returned by cardinality() is unaffected by the appearance of o in
   *         the stream.
   */
  boolean offer(Object o);

  /**
   * Offer the value as a hashed long value
   *
   * @param hashedLong - the hash of the item to offer to the estimator
   * @return false if the value returned by cardinality() is unaffected by the appearance of
   *         hashedLong in the stream
   */
  boolean offerHashed(long hashedLong);

  /**
   * Offer the value as a hashed long value
   *
   * @param hashedInt - the hash of the item to offer to the estimator
   * @return false if the value returned by cardinality() is unaffected by the appearance of
   *         hashedInt in the stream
   */
  boolean offerHashed(int hashedInt);

  /**
   * @return the number of unique elements in the stream or an estimate thereof
   */
  long cardinality();

  /**
   * @return size in bytes needed for serialization
   */
  int sizeof();

  /**
   * @return byte[]
   * @throws IOException
   */
  byte[] getBytes() throws IOException;

  /**
   * Merges estimators to produce a new estimator for the combined streams of this estimator and
   * those passed as arguments.
   * 
   * Nor this estimator nor the one passed as parameters are modified.
   *
   * @param estimators Zero or more compatible estimators
   * @throws CardinalityMergeException If at least one of the estimators is not compatible with this
   *         one
   */
  ICardinality merge(ICardinality... estimators) throws CardinalityMergeException;
}