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.arrow.algorithm.deduplicate;
  
  import org.apache.arrow.memory.ArrowBuf;
  import org.apache.arrow.memory.BufferAllocator;
  import org.apache.arrow.util.Preconditions;
  import org.apache.arrow.vector.BitVectorHelper;
  import org.apache.arrow.vector.IntVector;
  import org.apache.arrow.vector.ValueVector;
  import org.apache.arrow.vector.util.DataSizeRoundingUtil;
  
  /**
   * Remove adjacent equal elements from a vector. If the vector is sorted, it removes all duplicated
   * values in the vector.
   *
   * @param <V> vector type.
   */
  public class VectorRunDeduplicator<V extends ValueVector> implements AutoCloseable {
  
    /**
     * Bit set for distinct values. If the value at some index is not equal to the previous value, its
     * bit is set to 1, otherwise its bit is set to 0.
     */
    private ArrowBuf distinctValueBuffer;
  
    /** The vector to deduplicate. */
    private final V vector;
  
    private final BufferAllocator allocator;
  
    /**
     * Constructs a vector run deduplicator for a given vector.
     *
     * @param vector the vector to deduplicate. Ownership is NOT taken.
     * @param allocator the allocator used for allocating buffers for start indices.
     */
    public VectorRunDeduplicator(V vector, BufferAllocator allocator) {
      this.vector = vector;
      this.allocator = allocator;
    }
  
    private void createDistinctValueBuffer() {
      Preconditions.checkArgument(distinctValueBuffer == null);
      int bufSize = DataSizeRoundingUtil.divideBy8Ceil(vector.getValueCount());
      distinctValueBuffer = allocator.buffer(bufSize);
      DeduplicationUtils.populateRunStartIndicators(vector, distinctValueBuffer);
    }
  
    /**
     * Gets the number of values which are different from their predecessor.
     *
     * @return the run count.
     */
    public int getRunCount() {
      if (distinctValueBuffer == null) {
        createDistinctValueBuffer();
      }
      return vector.getValueCount()
          - BitVectorHelper.getNullCount(distinctValueBuffer, vector.getValueCount());
    }
  
    /**
     * Gets the vector with deduplicated adjacent values removed.
     *
     * @param outVector the output vector.
     */
    public void populateDeduplicatedValues(V outVector) {
      if (distinctValueBuffer == null) {
        createDistinctValueBuffer();
      }
  
      DeduplicationUtils.populateDeduplicatedValues(distinctValueBuffer, vector, outVector);
    }
  
    /**
     * Gets the length of each distinct value.
     *
     * @param lengthVector the vector for holding length values.
     */
    public void populateRunLengths(IntVector lengthVector) {
      if (distinctValueBuffer == null) {
        createDistinctValueBuffer();
      }
  
      DeduplicationUtils.populateRunLengths(
          distinctValueBuffer, lengthVector, vector.getValueCount());
    }
  
    @Override
    public void close() {
      if (distinctValueBuffer != null) {
        distinctValueBuffer.close();
        distinctValueBuffer = null;
      }
    }
  }
  