/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed 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 com.google.common.collect;

import com.google.common.annotations.GwtCompatible;

/**
 * Static methods for implementing hash-based collections.
 *
 * @author Kevin Bourrillion
 * @author Jesse Wilson
 */
@GwtCompatible
final class Hashing {
  private Hashing() {}

  /*
   * This method was written by Doug Lea with assistance from members of JCP
   * JSR-166 Expert Group and released to the public domain, as explained at
   * http://creativecommons.org/licenses/publicdomain
   * 
   * As of 2010/06/11, this method is identical to the (package private) hash
   * method in OpenJDK 7's java.util.HashMap class.
   */
  static int smear(int hashCode) {
    hashCode ^= (hashCode >>> 20) ^ (hashCode >>> 12);
    return hashCode ^ (hashCode >>> 7) ^ (hashCode >>> 4);
  }
}

/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed 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 com.google.common.collect;

import com.google.common.annotations.GwtCompatible;

/**
 * Static methods for implementing hash-based collections.
 *
 * @author Kevin Bourrillion
 * @author Jesse Wilson
 * @author Austin Appleby
 */
@GwtCompatible
final class Hashing {
  private Hashing() {}

  private static final int C1 = 0xcc9e2d51;
  private static final int C2 = 0x1b873593;

  /*
   * This method was rewritten in Java from an intermediate step of the Murmur hash function in
   * http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp, which contained the
   * following header:
   *
   * MurmurHash3 was written by Austin Appleby, and is placed in the public domain. The author
   * hereby disclaims copyright to this source code.
   */
  static int smear(int hashCode) {
    return C2 * Integer.rotateLeft(hashCode * C1, 15);
  }
}

Change Hashing.smear to use MurmurHash3's mixK1, which appears slightly faster and more effective for use in open-addressed hash tables. ------------- Created by MOE: http://code.google.com/p/moe-java MOE_MIGRATED_REVID=37090965