swaydb.core.util.MurmurHash3Generic.scala Maven / Gradle / Ivy

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/*
 * Copyright (c) 2020 Simer JS Plaha ([email protected] - @simerplaha)
 *
 * This file is a part of SwayDB.
 *
 * SwayDB is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * SwayDB is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with SwayDB. If not, see .
 *
 * Additional permission under the GNU Affero GPL version 3 section 7:
 * If you modify this Program or any covered work, only by linking or combining
 * it with separate works, the licensors of this Program grant you additional
 * permission to convey the resulting work.
 */

package swaydb.core.util

import java.lang.Long.rotateLeft

import swaydb.core.io.reader.Reader
import swaydb.data.slice.Slice


/**
 * Credit: Original implementation https://github.com/alexandrnikitin/bloom-filter-scala.
 */
private[swaydb] object MurmurHash3Generic {

  private val c1: Long = 0x87c37b91114253d5L
  private val c2: Long = 0x4cf5ad432745937fL

  def fmix64(l: Long): Long = {
    var k = l
    k ^= k >>> 33
    k *= 0xff51afd7ed558ccdL
    k ^= k >>> 33
    k *= 0xc4ceb9fe1a85ec53L
    k ^= k >>> 33
    k
  }

  def murmurhash3_x64_64(key: Slice[Byte], offset: Int, len: Int, seed: Int): Long = {
    val reader = Reader(key)
    var h1: Long = seed & 0x00000000FFFFFFFFL
    var h2: Long = seed & 0x00000000FFFFFFFFL

    val roundedEnd = offset + (len & 0xFFFFFFF0) // round down to 16 byte block

    var i = offset
    while (i < roundedEnd) {
      var k1 = reader.moveTo(i).readLong()
      var k2 = reader.moveTo(i + 8).readLong()
      k1 *= c1
      k1 = rotateLeft(k1, 31)
      k1 *= c2
      h1 ^= k1
      h1 = rotateLeft(h1, 27)
      h1 += h2
      h1 = h1 * 5 + 0x52dce729
      k2 *= c2
      k2 = rotateLeft(k2, 33)
      k2 *= c1
      h2 ^= k2
      h2 = rotateLeft(h2, 31)
      h2 += h1
      h2 = h2 * 5 + 0x38495ab5

      i += 16
    }

    var k1: Long = 0
    var k2: Long = 0

    val lenVar = len & 15
    if (lenVar == 15) k2 = (key(roundedEnd + 14) & 0xffL) << 48
    if (lenVar >= 14) k2 |= (key(roundedEnd + 13) & 0xffL) << 40
    if (lenVar >= 13) k2 |= (key(roundedEnd + 12) & 0xffL) << 32
    if (lenVar >= 12) k2 |= (key(roundedEnd + 11) & 0xffL) << 24
    if (lenVar >= 11) k2 |= (key(roundedEnd + 10) & 0xffL) << 16
    if (lenVar >= 10) k2 |= (key(roundedEnd + 9) & 0xffL) << 8
    if (lenVar >= 9) {
      k2 |= (key(roundedEnd + 8) & 0xffL)
      k2 *= c2
      k2 = rotateLeft(k2, 33)
      k2 *= c1
      h2 ^= k2
    }
    if (lenVar >= 8) k1 = key(roundedEnd + 7).toLong << 56
    if (lenVar >= 7) k1 |= (key(roundedEnd + 6) & 0xffL) << 48
    if (lenVar >= 6) k1 |= (key(roundedEnd + 5) & 0xffL) << 40
    if (lenVar >= 5) k1 |= (key(roundedEnd + 4) & 0xffL) << 32
    if (lenVar >= 4) k1 |= (key(roundedEnd + 3) & 0xffL) << 24
    if (lenVar >= 3) k1 |= (key(roundedEnd + 2) & 0xffL) << 16
    if (lenVar >= 2) k1 |= (key(roundedEnd + 1) & 0xffL) << 8
    if (lenVar >= 1) {
      k1 |= (key(roundedEnd) & 0xffL)
      k1 *= c1
      k1 = rotateLeft(k1, 31)
      k1 *= c2
      h1 ^= k1
    }

    h1 ^= len
    h2 ^= len

    h1 += h2
    h2 += h1

    h1 = fmix64(h1)
    h2 = fmix64(h2)

    h1 += h2
    h2 += h1

    h1 + h2
  }
}