content: /*
   * 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.cassandra.index.sai.disk.v1.postings;
  
  import java.io.IOException;
  
  import org.apache.cassandra.index.sai.postings.OrdinalPostingList;
  import org.apache.cassandra.index.sai.postings.PostingList;
  import org.apache.lucene.util.FixedBitSet;
  
  /**
   * A wrapper that iterates over a delegate {@link PostingList}, filtering out postings at
   * positions that are not present in a provided filter.
   */
  public class FilteringPostingList implements PostingList
  {
      private final FixedBitSet filter;
      private final OrdinalPostingList delegate;
      private final int cardinality;
      private int position = 0;
  
      public FilteringPostingList(FixedBitSet filter, OrdinalPostingList delegate)
      {
          cardinality = filter.cardinality();
          this.filter = filter;
          this.delegate = delegate;
      }
  
      @Override
      public void close()
      {
          delegate.close();
      }
  
      /**
       *
       * @return the segment row ID of the next match
       */
      @Override
      public long nextPosting() throws IOException
      {
          while (true)
          {
              long segmentRowId = delegate.nextPosting();
  
              if (segmentRowId == PostingList.END_OF_STREAM)
              {
                  return PostingList.END_OF_STREAM;
              }
  
              if (filter.get(position++))
              {
                  return segmentRowId;
              }
          }
      }
  
      @Override
      public long size()
      {
          return cardinality;
      }
  
      @Override
      public  long advance(long targetRowID) throws IOException
      {
          long segmentRowId = delegate.advance(targetRowID);
  
          if (segmentRowId == PostingList.END_OF_STREAM)
          {
              return PostingList.END_OF_STREAM;
          }
  
          // these are always for leaf balanced tree postings so the max is 1024
          position = (int)delegate.getOrdinal();
  
          // If the ordinal of the ID we just read satisfies the filter, just return it...
          if (filter.get(position - 1))
          {
              return segmentRowId;
          }
  
          // ...but if the ID doesn't satisfy the filter, get the next match.
          return nextPosting();
      }
  }
  