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Data Sketches Core

There is a newer version: 0.13.4

/*
 * Copyright 2015-16, 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.tuple;

import static com.yahoo.sketches.hash.MurmurHash3.hash;
import static java.nio.charset.StandardCharsets.UTF_8;

import com.yahoo.sketches.SketchesArgumentException;

final class Util {

  static final long[] doubleToLongArray(final double value) {
    final double d = (value == 0.0) ? 0.0 : value; // canonicalize -0.0, 0.0
    final long[] array = { Double.doubleToLongBits(d) }; // canonicalize all NaN forms
    return array;
  }

  static final byte[] stringToByteArray(final String value) {
    if (value == null || value.isEmpty()) { return null; }
    return value.getBytes(UTF_8);
  }

  /**
   * Computes and checks the 16-bit seed hash from the given long seed.
   * The seed hash may not be zero in order to maintain compatibility with older serialized
   * versions that did not have this concept.
   * @param seed See Update Hash Seed
   * @return the seed hash.
   */
  static short computeSeedHash(final long seed) {
    final long[] seedArr = {seed};
    final short seedHash = (short)((hash(seedArr, 0L)[0]) & 0xFFFFL);
    if (seedHash == 0) {
      throw new SketchesArgumentException(
          "The given seed: " + seed + " produced a seedHash of zero. "
              + "You must choose a different seed.");
    }
    return seedHash;
  }

  static final void checkSeedHashes(final short seedHashA, final short seedHashB) {
    if (seedHashA != seedHashB) {
      throw new SketchesArgumentException("Incompatible Seed Hashes. " + seedHashA + ", "
          + seedHashB);
    }

  }

}