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Data Sketches Core
There is a newer version: 0.6.0
/*
 * Copyright 2017, Yahoo! Inc. Licensed under the terms of the
 * Apache License 2.0. See LICENSE file at the project root for terms.
 */

package com.yahoo.sketches.hll;

import static com.yahoo.sketches.hll.HllUtil.AUX_TOKEN;
import static com.yahoo.sketches.hll.HllUtil.EMPTY;
import static com.yahoo.sketches.hll.HllUtil.LG_AUX_ARR_INTS;

/**
 * Converters for one TgtHllType to another.
 * @author Lee Rhodes
 */
class Conversions {

  static final Hll4Array convertToHll4(final AbstractHllArray srcHllArr) {
    final int lgConfigK = srcHllArr.getLgConfigK();
    final Hll4Array hll4Array = new Hll4Array(lgConfigK);
    hll4Array.putOutOfOrderFlag(srcHllArr.isOutOfOrderFlag());

    //1st pass: compute starting curMin and numAtCurMin:
    final int pair = curMinAndNum(srcHllArr);
    final int curMin = HllUtil.getValue(pair);
    final int numAtCurMin = HllUtil.getLow26(pair);

    //2nd pass: Must know curMin. Populate KxQ registers, build AuxHashMap if needed
    final PairIterator itr = srcHllArr.iterator();
    AuxHashMap auxHashMap = hll4Array.getAuxHashMap(); //may be null
    while (itr.nextValid()) {
      final int slotNo = itr.getIndex();
      final int actualValue = itr.getValue();
      AbstractHllArray.hipAndKxQIncrementalUpdate(hll4Array, 0, actualValue); //was srcHllArr
      if (actualValue >= (curMin + 15)) {
        hll4Array.putSlot(slotNo, AUX_TOKEN);
        if (auxHashMap == null) {
          auxHashMap = new HeapAuxHashMap(LG_AUX_ARR_INTS[lgConfigK], lgConfigK);
          hll4Array.putAuxHashMap(auxHashMap, false);
        }
        auxHashMap.mustAdd(slotNo, actualValue);
      } else {
        hll4Array.putSlot(slotNo, actualValue - curMin);
      }
    }

    hll4Array.putCurMin(curMin);
    hll4Array.putNumAtCurMin(numAtCurMin);
    hll4Array.putHipAccum(srcHllArr.getHipAccum());
    return hll4Array;
  }

  static final int curMinAndNum(final AbstractHllArray hllArr) {
    int curMin = 64;
    int numAtCurMin = 0;
    final PairIterator itr = hllArr.iterator();
    while (itr.nextAll()) {
      final int v = itr.getValue();
      if (v < curMin) {
        curMin = v;
        numAtCurMin = 1;
      } else if (v == curMin) { //missing else
        numAtCurMin++;
      }
    }
    return HllUtil.pair(numAtCurMin, curMin);
  }

  static final Hll6Array convertToHll6(final AbstractHllArray srcHllArr) {
    final int lgConfigK = srcHllArr.lgConfigK;
    final Hll6Array hll6Array = new Hll6Array(lgConfigK);
    hll6Array.putOutOfOrderFlag(srcHllArr.isOutOfOrderFlag());
    int numZeros = 1 << lgConfigK;
    final PairIterator itr = srcHllArr.iterator();
    while (itr.nextAll()) {
      if (itr.getValue() != EMPTY) {
        numZeros--;
        hll6Array.couponUpdate(itr.getPair()); //creates KxQ registers
      }
    }
    hll6Array.putNumAtCurMin(numZeros);
    hll6Array.putHipAccum(srcHllArr.getHipAccum());
    return hll6Array;
  }

  static final Hll8Array convertToHll8(final AbstractHllArray srcHllArr) {
    final int lgConfigK = srcHllArr.lgConfigK;
    final Hll8Array hll8Array = new Hll8Array(lgConfigK);
    hll8Array.putOutOfOrderFlag(srcHllArr.isOutOfOrderFlag());
    int numZeros = 1 << lgConfigK;
    final PairIterator itr = srcHllArr.iterator();
    while (itr.nextAll()) {
      if (itr.getValue() != EMPTY) {
        numZeros--;
        hll8Array.couponUpdate(itr.getPair());
      }
    }
    hll8Array.putNumAtCurMin(numZeros);
    hll8Array.putHipAccum(srcHllArr.getHipAccum());
    return hll8Array;
  }

}