content: /*
   * Copyright (C) 2016-2023 ActionTech.
   * based on code by MyCATCopyrightHolder Copyright (c) 2013, OpenCloudDB/MyCAT.
   * License: http://www.gnu.org/licenses/gpl.html GPL version 2 or higher.
   */
  package com.actiontech.dble.route.util;
  
  /**
   * PartitionForSingle
   *
   * @author mycat
   */
  public final class PartitionForSingle {
  
      private static final int PARTITION_LENGTH = 1024;
  
      private static final int DEFAULT_HASH_LENGTH = 8;
  
      private static final long AND_VALUE = PARTITION_LENGTH - 1;
  
      private final int[] segment = new int[PARTITION_LENGTH];
  
      public PartitionForSingle(int[] count, int[] length) {
          if (count == null || length == null || (count.length != length.length)) {
              throw new RuntimeException("error,check your scope & scopeLength definition.");
          }
          int segmentLength = 0;
          for (int i = 0; i < count.length; i++) {
              segmentLength += count[i];
          }
          int[] scopeSegment = new int[segmentLength + 1];
  
          int index = 0;
          for (int i = 0; i < count.length; i++) {
              for (int j = 0; j < count[i]; j++) {
                  scopeSegment[++index] = scopeSegment[index - 1] + length[i];
              }
          }
          if (scopeSegment[scopeSegment.length - 1] != PARTITION_LENGTH) {
              throw new RuntimeException("error,check your partitionScope definition.");
          }
  
          for (int i = 1; i < scopeSegment.length; i++) {
              for (int j = scopeSegment[i - 1]; j < scopeSegment[i]; j++) {
                  segment[j] = (i - 1);
              }
          }
      }
  
      public int partition(long h) {
          return segment[(int) (h & AND_VALUE)];
      }
  
      public int partition(String key) {
          return segment[(int) (hash(key) & AND_VALUE)];
      }
  
      private static long hash(String s) {
          long h = 0;
          int len = s.length();
          for (int i = 0; (i < DEFAULT_HASH_LENGTH && i < len); i++) {
              h = (h << 5) - h + s.charAt(i);
          }
          return h;
      }
  
      // for test
      public static void main(String[] args) {
          // split to 16 nodes and every node contains 64.
          // Scope scope = new Scope(new int[] { 16 }, new int[] { 64 });
  
          // split to 23 nodes ,the front 8 nodes contains 8,the last 15 nodes contains 64.
          // Scope scope = new Scope(new int[] { 8, 15 }, new int[] { 8, 64 });
  
          // split to 128 nodes and every node contains 8.
          // Scope scope = new Scope(new int[] { 128 }, new int[] { 8 });
  
          PartitionForSingle p = new PartitionForSingle(new int[]{8, 15}, new int[]{8, 64});
  
          String memberId = "xianmao.hexm";
  
          int value = 0;
          long st = System.currentTimeMillis();
          for (int i = 0; i < 10000000; i++) {
              value = p.partition(memberId);
          }
          long et = System.currentTimeMillis();
  
          System.out.println("value:" + value + ",take time:" + (et - st) + " ms.");
      }
  
  }