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Lucene example source code file (SentinelIntSet.java)

This example Lucene source code file (SentinelIntSet.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

sentinelintset, sentinelintset, util

The Lucene SentinelIntSet.java source code

/**
 * 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.
 */

package org.apache.lucene.search.grouping;

import java.util.Arrays;

/** A native int set where one value is reserved to mean "EMPTY" */
class SentinelIntSet {
  public int[] keys;
  public int count;
  public final int emptyVal;
  public int rehashCount;   // the count at which a rehash should be done

  public SentinelIntSet(int size, int emptyVal) {
    this.emptyVal = emptyVal;
    int tsize = Math.max(org.apache.lucene.util.BitUtil.nextHighestPowerOfTwo(size), 1);
    rehashCount = tsize - (tsize>>2);
    if (size >= rehashCount) {  // should be able to hold "size" w/o rehashing
      tsize <<= 1;
      rehashCount = tsize - (tsize>>2);
    }
    keys = new int[tsize];
    if (emptyVal != 0)
      clear();
  }

  public void clear() {
    Arrays.fill(keys, emptyVal);
    count = 0;
  }

  public int hash(int key) {
    return key;
  }

  public int size() { return count; }

  /** returns the slot for this key */
  public int getSlot(int key) {
    assert key != emptyVal;
    int h = hash(key);
    int s = h & (keys.length-1);
    if (keys[s] == key || keys[s]== emptyVal) return s;

    int increment = (h>>7)|1;
    do {
      s = (s + increment) & (keys.length-1);
    } while (keys[s] != key && keys[s] != emptyVal);
    return s;
  }

  /** returns the slot for this key, or -slot-1 if not found */
  public int find(int key) {
    assert key != emptyVal;
    int h = hash(key);
    int s = h & (keys.length-1);
    if (keys[s] == key) return s;
    if (keys[s] == emptyVal) return -s-1;

    int increment = (h>>7)|1;
    for(;;) {
      s = (s + increment) & (keys.length-1);
      if (keys[s] == key) return s;
      if (keys[s] == emptyVal) return -s-1;
    }
  }

  public boolean exists(int key) {
    return find(key) >= 0;
  }

  public int put(int key) {
    int s = find(key);
    if (s < 0) {
      if (count >= rehashCount) {
        rehash();
        s = getSlot(key);
      } else {
        s = -s-1;
      }
      count++;
      keys[s] = key;
    }
    return s;
  }

  public void rehash() {
    int newSize = keys.length << 1;
    int[] oldKeys = keys;
    keys = new int[newSize];
    if (emptyVal != 0) Arrays.fill(keys, emptyVal);

    for (int i=0; i<oldKeys.length; i++) {
      int key = oldKeys[i];
      if (key == emptyVal) continue;
      int newSlot = getSlot(key);
      keys[newSlot] = key;
    }
    rehashCount = newSize - (newSize>>2);
  }
}

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