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.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.compare.Range;
  import org.apache.arrow.vector.compare.RangeEqualsVisitor;
  import org.apache.arrow.vector.util.DataSizeRoundingUtil;
  
  /** Utilities for vector deduplication. */
  class DeduplicationUtils {
  
    /**
     * Gets the start positions of the first distinct values in a vector.
     *
     * @param vector the target vector.
     * @param runStarts the bit set to hold the start positions.
     * @param <V> vector type.
     */
    public static <V extends ValueVector> void populateRunStartIndicators(
        V vector, ArrowBuf runStarts) {
      int bufSize = DataSizeRoundingUtil.divideBy8Ceil(vector.getValueCount());
      Preconditions.checkArgument(runStarts.capacity() >= bufSize);
      runStarts.setZero(0, bufSize);
  
      BitVectorHelper.setBit(runStarts, 0);
      RangeEqualsVisitor visitor = new RangeEqualsVisitor(vector, vector, null);
      Range range = new Range(0, 0, 1);
      for (int i = 1; i < vector.getValueCount(); i++) {
        range.setLeftStart(i).setRightStart(i - 1);
        if (!visitor.rangeEquals(range)) {
          BitVectorHelper.setBit(runStarts, i);
        }
      }
    }
  
    /**
     * Gets the run lengths, given the start positions.
     *
     * @param runStarts the bit set for start positions.
     * @param runLengths the run length vector to populate.
     * @param valueCount the number of values in the bit set.
     */
    public static void populateRunLengths(ArrowBuf runStarts, IntVector runLengths, int valueCount) {
      int curStart = 0;
      int lengthIndex = 0;
      for (int i = 1; i < valueCount; i++) {
        if (BitVectorHelper.get(runStarts, i) != 0) {
          // we get a new distinct value
          runLengths.setSafe(lengthIndex++, i - curStart);
          curStart = i;
        }
      }
  
      // process the last value
      runLengths.setSafe(lengthIndex++, valueCount - curStart);
      runLengths.setValueCount(lengthIndex);
    }
  
    /**
     * Gets distinct values from the input vector by removing adjacent duplicated values.
     *
     * @param indicators the bit set containing the start positions of distinct values.
     * @param inputVector the input vector.
     * @param outputVector the output vector.
     * @param <V> vector type.
     */
    public static <V extends ValueVector> void populateDeduplicatedValues(
        ArrowBuf indicators, V inputVector, V outputVector) {
      int dstIdx = 0;
      for (int srcIdx = 0; srcIdx < inputVector.getValueCount(); srcIdx++) {
        if (BitVectorHelper.get(indicators, srcIdx) != 0) {
          outputVector.copyFromSafe(srcIdx, dstIdx++, inputVector);
        }
      }
      outputVector.setValueCount(dstIdx);
    }
  }
  