net.jpountz.xxhash.XXHash32JavaSafe Maven / Gradle / Ivy

package net.jpountz.xxhash;

/*
 * 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.
 */

import static java.lang.Integer.rotateLeft;
import static net.jpountz.util.Utils.checkRange;
import static net.jpountz.util.Utils.readIntLE;
import static net.jpountz.xxhash.XXHashUtils.PRIME1;
import static net.jpountz.xxhash.XXHashUtils.PRIME2;
import static net.jpountz.xxhash.XXHashUtils.PRIME3;
import static net.jpountz.xxhash.XXHashUtils.PRIME4;
import static net.jpountz.xxhash.XXHashUtils.PRIME5;

/**
 * Safe Java implementation of {@link XXHash32}.
 */
enum XXHash32JavaSafe implements XXHash32 {

  INSTANCE {

    @Override
    public int hash(byte[] buf, int off, int len, int seed) {
      checkRange(buf, off, len);

      final int end = off + len;
      int h32;

      if (len >= 16) {
        final int limit = end - 16;
        int v1 = seed + PRIME1 + PRIME2;
        int v2 = seed + PRIME2;
        int v3 = seed + 0;
        int v4 = seed - PRIME1;
        do {
          v1 += readIntLE(buf, off) * PRIME2;
          v1 = rotateLeft(v1, 13);
          v1 *= PRIME1;
          off += 4;

          v2 += readIntLE(buf, off) * PRIME2;
          v2 = rotateLeft(v2, 13);
          v2 *= PRIME1;
          off += 4;

          v3 += readIntLE(buf, off) * PRIME2;
          v3 = rotateLeft(v3, 13);
          v3 *= PRIME1;
          off += 4;

          v4 += readIntLE(buf, off) * PRIME2;
          v4 = rotateLeft(v4, 13);
          v4 *= PRIME1;
          off += 4;
        } while (off <= limit);

        h32 = rotateLeft(v1, 1) + rotateLeft(v2, 7) + rotateLeft(v3, 12) + rotateLeft(v4, 18);
      } else {
        h32 = seed + PRIME5;
      }

      h32 += len;

      while (off <= end - 4) {
        h32 += readIntLE(buf, off) * PRIME3;
        h32 = rotateLeft(h32, 17) * PRIME4;
        off += 4;
      }

      while (off < end) {
        h32 += (buf[off] & 0xFF) * PRIME5;
        h32 = rotateLeft(h32, 11) * PRIME1;
        ++off;
      }

      h32 ^= h32 >>> 15;
      h32 *= PRIME2;
      h32 ^= h32 >>> 13;
      h32 *= PRIME3;
      h32 ^= h32 >>> 16;

      return h32;
    }

  };

  @Override
  public String toString() {
    return getDeclaringClass().getSimpleName();
  }

}