content: package com.clearspring.analytics.hash;
  /**
   * 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 java.util.Random;
  
  import org.junit.Test;
  
  import static org.junit.Assert.assertEquals;
  
  /**
   * Tests for lookup3ycs hash functions
   *
   * @author yonik
   */
  public class TestLookup3Hash {
  
      // Test that the java version produces the same output as the C version
  
      @Test
      public void testEqualsLOOKUP3() {
          int[] hashes = new int[]{0xc4c20dd5, 0x3ab04cc3, 0xebe874a3, 0x0e770ef3, 0xec321498, 0x73845e86, 0x8a2db728, 0x03c313bb, 0xfe5b9199, 0x95965125, 0xcbc4e7c2};
          /*** the hash values were generated by adding the following to lookup3.c
           *
           * char* s = "hello world";
           * int len = strlen(s);
           * uint32_t a[len];
           * for (int i=0; i<len; i++) {
           *   a[i]=s[i];
           *   uint32_t result = hashword(a, i+1, i*12345);
           *   printf("0x%.8x\n", result);
           * }
           *
           */
  
          String s = "hello world";
          int[] a = new int[s.length()];
          for (int i = 0; i < s.length(); i++) {
              a[i] = s.charAt(i);
              int len = i + 1;
              int hash = Lookup3Hash.lookup3(a, 0, len, i * 12345);
              assertEquals(hashes[i], hash);
              int hash2 = Lookup3Hash.lookup3ycs(a, 0, len, i * 12345 + (len << 2));
              assertEquals(hashes[i], hash2);
              int hash3 = Lookup3Hash.lookup3ycs(s, 0, len, i * 12345 + (len << 2));
              assertEquals(hashes[i], hash3);
          }
      }
  
  
      /**
       * test that the hash of the UTF-16 encoded Java String is equal to the hash of the unicode code points
       *
       * @param utf32
       * @param len
       */
      void tstEquiv(int[] utf32, int len) {
          int seed = 100;
          StringBuilder sb = new StringBuilder();
          for (int i = 0; i < len; i++) {
              sb.appendCodePoint(utf32[i]);
          }
          int hash = Lookup3Hash.lookup3(utf32, 0, len, seed - (len << 2));
          int hash2 = Lookup3Hash.lookup3ycs(utf32, 0, len, seed);
          assertEquals(hash, hash2);
          int hash3 = Lookup3Hash.lookup3ycs(sb, 0, sb.length(), seed);
          assertEquals(hash, hash3);
          long hash4 = Lookup3Hash.lookup3ycs64(sb, 0, sb.length(), seed);
          assertEquals((int) hash4, hash);
      }
  
      @Test
      public void testHash() {
          Random r = new Random(0);
          int[] utf32 = new int[20];
          tstEquiv(utf32, 0);
  
          utf32[0] = 0x10000;
          tstEquiv(utf32, 1);
          utf32[0] = 0x8000;
          tstEquiv(utf32, 1);
          utf32[0] = Character.MAX_CODE_POINT;
          tstEquiv(utf32, 1);
  
          for (int iter = 0; iter < 10000; iter++) {
              int len = r.nextInt(utf32.length + 1);
              for (int i = 0; i < len; i++) {
                  int codePoint;
                  do {
                      codePoint = r.nextInt(Character.MAX_CODE_POINT + 1);
                  } while ((codePoint & 0xF800) == 0xD800);  // avoid surrogate code points
                  utf32[i] = codePoint;
              }
              // System.out.println("len="+len + ","+utf32[0]+","+utf32[1]);
              tstEquiv(utf32, len);
          }
      }
  
  
  }
  