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.spark.util.sketch;
  
  /**
   * 32-bit Murmur3 hasher.  This is based on Guava's Murmur3_32HashFunction.
   */
  // This class is duplicated from `org.apache.spark.unsafe.hash.Murmur3_x86_32` to make sure
  // spark-sketch has no external dependencies.
  final class Murmur3_x86_32 {
    private static final int C1 = 0xcc9e2d51;
    private static final int C2 = 0x1b873593;
  
    private final int seed;
  
    Murmur3_x86_32(int seed) {
      this.seed = seed;
    }
  
    @Override
    public String toString() {
      return "Murmur3_32(seed=" + seed + ")";
    }
  
    public int hashInt(int input) {
      return hashInt(input, seed);
    }
  
    public static int hashInt(int input, int seed) {
      int k1 = mixK1(input);
      int h1 = mixH1(seed, k1);
  
      return fmix(h1, 4);
    }
  
    public int hashUnsafeWords(Object base, long offset, int lengthInBytes) {
      return hashUnsafeWords(base, offset, lengthInBytes, seed);
    }
  
    public static int hashUnsafeWords(Object base, long offset, int lengthInBytes, int seed) {
      // This is based on Guava's `Murmur32_Hasher.processRemaining(ByteBuffer)` method.
      assert (lengthInBytes % 8 == 0): "lengthInBytes must be a multiple of 8 (word-aligned)";
      int h1 = hashBytesByInt(base, offset, lengthInBytes, seed);
      return fmix(h1, lengthInBytes);
    }
  
    public static int hashUnsafeBytes(Object base, long offset, int lengthInBytes, int seed) {
      assert (lengthInBytes >= 0): "lengthInBytes cannot be negative";
      int lengthAligned = lengthInBytes - lengthInBytes % 4;
      int h1 = hashBytesByInt(base, offset, lengthAligned, seed);
      for (int i = lengthAligned; i < lengthInBytes; i++) {
        int halfWord = Platform.getByte(base, offset + i);
        int k1 = mixK1(halfWord);
        h1 = mixH1(h1, k1);
      }
      return fmix(h1, lengthInBytes);
    }
  
    private static int hashBytesByInt(Object base, long offset, int lengthInBytes, int seed) {
      assert (lengthInBytes % 4 == 0);
      int h1 = seed;
      for (int i = 0; i < lengthInBytes; i += 4) {
        int halfWord = Platform.getInt(base, offset + i);
        int k1 = mixK1(halfWord);
        h1 = mixH1(h1, k1);
      }
      return h1;
    }
  
    public int hashLong(long input) {
      return hashLong(input, seed);
    }
  
    public static int hashLong(long input, int seed) {
      int low = (int) input;
      int high = (int) (input >>> 32);
  
      int k1 = mixK1(low);
      int h1 = mixH1(seed, k1);
  
      k1 = mixK1(high);
      h1 = mixH1(h1, k1);
  
      return fmix(h1, 8);
    }
  
    private static int mixK1(int k1) {
      k1 *= C1;
      k1 = Integer.rotateLeft(k1, 15);
      k1 *= C2;
      return k1;
    }
  
    private static int mixH1(int h1, int k1) {
      h1 ^= k1;
      h1 = Integer.rotateLeft(h1, 13);
      h1 = h1 * 5 + 0xe6546b64;
      return h1;
    }
  
    // Finalization mix - force all bits of a hash block to avalanche
    private static int fmix(int h1, int length) {
      h1 ^= length;
      h1 ^= h1 >>> 16;
      h1 *= 0x85ebca6b;
      h1 ^= h1 >>> 13;
      h1 *= 0xc2b2ae35;
      h1 ^= h1 >>> 16;
      return h1;
    }
  }
  