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A module that is everything required to understands Druid Segments

There is a newer version: 30.0.0

/*
 * 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.druid.java.util.common.guava;

import com.google.common.base.Predicate;

import java.io.IOException;

/**
 */
public class FilteredSequence implements Sequence
{
  private final Sequence baseSequence;
  private final Predicate pred;

  public FilteredSequence(
      Sequence baseSequence,
      Predicate pred
  )
  {
    this.baseSequence = baseSequence;
    this.pred = pred;
  }

  @Override
  public  OutType accumulate(OutType initValue, Accumulator accumulator)
  {
    return baseSequence.accumulate(initValue, new FilteringAccumulator<>(pred, accumulator));
  }

  @Override
  public  Yielder toYielder(OutType initValue, YieldingAccumulator accumulator)
  {
    final FilteringYieldingAccumulator filteringAccumulator =
        new FilteringYieldingAccumulator<>(pred, accumulator);

    return wrapYielder(baseSequence.toYielder(initValue, filteringAccumulator), filteringAccumulator);
  }

  private  Yielder wrapYielder(
      final Yielder yielder, final FilteringYieldingAccumulator accumulator
  )
  {
    return new Yielder()
    {
      @Override
      public OutType get()
      {
        return yielder.get();
      }

      @Override
      public Yielder next(OutType initValue)
      {
        return wrapYielder(yielder.next(initValue), accumulator);
      }

      @Override
      public boolean isDone()
      {
        return !accumulator.didSomething() || yielder.isDone();
      }

      @Override
      public void close() throws IOException
      {
        yielder.close();
      }
    };
  }
}