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.bookkeeper.common.hash;
  
  import io.netty.buffer.ByteBuf;
  
  /**
   * This is a very fast, non-cryptographic hash suitable for general hash-based
   * lookup. See http://murmurhash.googlepages.com/ for more details.
   *
   * <p>
   * The C version of MurmurHash 2.0 found at that site was ported to Java by
   * Andrzej Bialecki (ab at getopt org).
   * </p>
   */
  public class MurmurHash {
  
      /**
       * Create a 32 bits murmur hash value for the provided {@code data}.
       *
       * @param data   the data point to data
       * @param offset offset
       * @param length length
       * @param seed   the seed
       * @return the 32 bits murmur hash value.
       */
      public static int hash32(ByteBuf data, int offset, int length, int seed) {
          int m = 0x5bd1e995;
          int r = 24;
  
          int h = seed ^ length;
  
          int len4 = length >> 2;
  
          for (int i = 0; i < len4; i++) {
              int i4 = i << 2;
              int k = data.getByte(offset + i4 + 3);
              k = k << 8;
              k = k | (data.getByte(offset + i4 + 2) & 0xff);
              k = k << 8;
              k = k | (data.getByte(offset + i4 + 1) & 0xff);
              k = k << 8;
              k = k | (data.getByte(offset + i4 + 0) & 0xff);
              k *= m;
              k ^= k >>> r;
              k *= m;
              h *= m;
              h ^= k;
          }
  
          // avoid calculating modulo
          int lenM = len4 << 2;
          int left = length - lenM;
  
          if (left != 0) {
              if (left >= 3) {
                  h ^= (int) data.getByte(offset + length - 3) << 16;
              }
              if (left >= 2) {
                  h ^= (int) data.getByte(offset + length - 2) << 8;
              }
              if (left >= 1) {
                  h ^= (int) data.getByte(offset + length - 1);
              }
  
              h *= m;
          }
  
          h ^= h >>> 13;
          h *= m;
          h ^= h >>> 15;
  
          return h;
      }
  
      /**
       * Create a 64 bits murmur hash value for the provided {@code data}.
       *
       * @param key    the data point to data
       * @param offset offset
       * @param length length
       * @param seed   the seed
       * @return the 32 bits murmur hash value.
       */
      public static long hash64(ByteBuf key, int offset, int length, long seed) {
          long m64 = 0xc6a4a7935bd1e995L;
          int r64 = 47;
  
          long h64 = (seed & 0xffffffffL) ^ (m64 * length);
  
          int lenLongs = length >> 3;
  
          for (int i = 0; i < lenLongs; ++i) {
              int i8 = i << 3;
  
              long k64 = ((long) key.getByte(offset + i8 + 0) & 0xff)
                  + (((long) key.getByte(offset + i8 + 1) & 0xff) << 8)
                  + (((long) key.getByte(offset + i8 + 2) & 0xff) << 16)
                  + (((long) key.getByte(offset + i8 + 3) & 0xff) << 24)
                  + (((long) key.getByte(offset + i8 + 4) & 0xff) << 32)
                  + (((long) key.getByte(offset + i8 + 5) & 0xff) << 40)
                  + (((long) key.getByte(offset + i8 + 6) & 0xff) << 48)
                  + (((long) key.getByte(offset + i8 + 7) & 0xff) << 56);
  
              k64 *= m64;
              k64 ^= k64 >>> r64;
              k64 *= m64;
  
              h64 ^= k64;
              h64 *= m64;
          }
  
          int rem = length & 0x7;
  
          // CHECKSTYLE.OFF: FallThrough
          switch (rem) {
              case 0:
                  break;
              case 7:
                  h64 ^= (long) key.getByte(offset + length - rem + 6) << 48;
              case 6:
                  h64 ^= (long) key.getByte(offset + length - rem + 5) << 40;
              case 5:
                  h64 ^= (long) key.getByte(offset + length - rem + 4) << 32;
              case 4:
                  h64 ^= (long) key.getByte(offset + length - rem + 3) << 24;
              case 3:
                  h64 ^= (long) key.getByte(offset + length - rem + 2) << 16;
              case 2:
                  h64 ^= (long) key.getByte(offset + length - rem + 1) << 8;
              case 1:
                  h64 ^= (long) key.getByte(offset + length - rem);
                  h64 *= m64;
          }
          // CHECKSTYLE.ON: FallThrough
  
          h64 ^= h64 >>> r64;
          h64 *= m64;
          h64 ^= h64 >>> r64;
  
          return h64;
      }
  }
  