content: /*
   * 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 com.clearspring.analytics.stream.cardinality;
  
  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
       * @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.
       * <p/>
       * 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;
  }
  