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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.commons.rng.core.source64;
19  
20  /**
21   * A fast all-purpose 64-bit generator.
22   *
23   * <p>This is a member of the Xor-Shift-Rotate family of generators. Memory footprint is 256 bits
24   * and the period is 2<sup>256</sup>-1.</p>
25   *
26   * @see <a href="http://xoshiro.di.unimi.it/xoshiro256starstar.c">Original source code</a>
27   * @see <a href="http://xoshiro.di.unimi.it/">xorshiro / xoroshiro generators</a>
28   * @since 1.3
29   */
30  public class XoShiRo256StarStar extends AbstractXoShiRo256 {
31      /**
32       * Creates a new instance.
33       *
34       * @param seed Initial seed.
35       * If the length is larger than 4, only the first 4 elements will
36       * be used; if smaller, the remaining elements will be automatically
37       * set. A seed containing all zeros will create a non-functional generator.
38       */
39      public XoShiRo256StarStar(long[] seed) {
40          super(seed);
41      }
42  
43      /**
44       * Creates a new instance using a 4 element seed.
45       * A seed containing all zeros will create a non-functional generator.
46       *
47       * @param seed0 Initial seed element 0.
48       * @param seed1 Initial seed element 1.
49       * @param seed2 Initial seed element 2.
50       * @param seed3 Initial seed element 3.
51       */
52      public XoShiRo256StarStar(long seed0, long seed1, long seed2, long seed3) {
53          super(seed0, seed1, seed2, seed3);
54      }
55  
56      /**
57       * Creates a copy instance.
58       *
59       * @param source Source to copy.
60       */
61      protected XoShiRo256StarStar(XoShiRo256StarStar source) {
62          super(source);
63      }
64  
65      /** {@inheritDoc} */
66      @Override
67      protected long nextOutput() {
68          return Long.rotateLeft(state1 * 5, 7) * 9;
69      }
70  
71      /** {@inheritDoc} */
72      @Override
73      protected XoShiRo256StarStar copy() {
74          // This exists to ensure the jump function performed in the super class returns
75          // the correct class type. It should not be public.
76          return new XoShiRo256StarStar(this);
77      }
78  }