code: /*
   * Copyright (c) 2017-2018 The Regents of the University of California
   *
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are
   * met:
   *
   * 1. Redistributions of source code must retain the above copyright
   * notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   * notice, this list of conditions and the following disclaimer in the
   * documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  package edu.berkeley.cs.jqf.fuzz.util;
  
  /**
   * Utility class for computing bounded hash values.
   *
   * @author Rohan Padhye
   */
  public class Hashing {
  
      private Hashing() {
          // Static only
      }
  
      private static int cap(long x, int bound) {
          int res = (int) (x % bound);
          if (res < 0) {
              res += bound;
          }
          return res;
      }
  
      /**
       * Compute knuth's multiplicative hash.
       *
       * <p>Source: Donald Knuth's <em>The Art of Computer Programming</em>,
       * Volume 3 (2nd edition), section 6.4, page 516.</p>
       *
       * @param x     the input value to hash
       * @param bound the upper bound
       * @return the hash value
       */
      protected static int knuth(long x, int bound) {
          return cap(x*2654435761L, bound);
      }
  
      /**
       * Returns a bounded hashed value with one input.
       *
       * @param x     the input to hash
       * @param bound the upper bound
       * @return a pseudo-uniformly distributed value in [0, bound)
       */
      public static int hash(long x, int bound) {
          return knuth(x, bound);
      }
  
      /**
       * Returns a bounded hashed value with two inputs.
       *
       * @param x     the first input to hash
       * @param y     the second input to hash
       * @param bound the upper bound
       * @return a pseudo-uniformly distributed value in [0, bound)
       */
      public static int hash1(long x, long y, int bound) {
          return knuth(x*31 + y, bound);
      }
  
  }
  