content: /*
   * Copyright 2005-2010 Roger Kapsi, Sam Berlin
   *
   *   Licensed 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.cassandra.index.sasi.utils.trie;
  
  import java.io.Serializable;
  import java.util.AbstractMap;
  import java.util.Map;
  
  /**
   * This class is taken from https://github.com/rkapsi/patricia-trie (v0.6), and slightly modified
   * to correspond to Cassandra code style, as the only Patricia Trie implementation,
   * which supports pluggable key comparators (e.g. commons-collections PatriciaTrie (which is based
   * on rkapsi/patricia-trie project) only supports String keys)
   * but unfortunately is not deployed to the maven central as a downloadable artifact.
   */
  
  /**
   * This class provides some basic {@link Trie} functionality and
   * utility methods for actual {@link Trie} implementations.
   */
  abstract class AbstractTrie<K, V> extends AbstractMap<K, V> implements Serializable, Trie<K, V>
  {
      private static final long serialVersionUID = -6358111100045408883L;
  
      /**
       * The {@link KeyAnalyzer} that's being used to build the
       * PATRICIA {@link Trie}
       */
      protected final KeyAnalyzer<? super K> keyAnalyzer;
  
      /**
       * Constructs a new {@link Trie} using the given {@link KeyAnalyzer}
       */
      public AbstractTrie(KeyAnalyzer<? super K> keyAnalyzer)
      {
          this.keyAnalyzer = Tries.notNull(keyAnalyzer, "keyAnalyzer");
      }
  
      @Override
      public K selectKey(K key)
      {
          Map.Entry<K, V> entry = select(key);
          return entry != null ? entry.getKey() : null;
      }
  
      @Override
      public V selectValue(K key)
      {
          Map.Entry<K, V> entry = select(key);
          return entry != null ? entry.getValue() : null;
      }
  
      @Override
      public String toString()
      {
          StringBuilder buffer = new StringBuilder();
          buffer.append("Trie[").append(size()).append("]={\n");
          for (Map.Entry<K, V> entry : entrySet())
          {
              buffer.append("  ").append(entry).append("\n");
          }
          buffer.append("}\n");
          return buffer.toString();
      }
  
      /**
       * Returns the length of the given key in bits
       *
       * @see KeyAnalyzer#lengthInBits(Object)
       */
      final int lengthInBits(K key)
      {
          return key == null ? 0 : keyAnalyzer.lengthInBits(key);
      }
  
      /**
       * Returns whether or not the given bit on the
       * key is set or false if the key is null.
       *
       * @see KeyAnalyzer#isBitSet(Object, int)
       */
      final boolean isBitSet(K key, int bitIndex)
      {
          return key != null && keyAnalyzer.isBitSet(key, bitIndex);
      }
  
      /**
       * Utility method for calling {@link KeyAnalyzer#bitIndex(Object, Object)}
       */
      final int bitIndex(K key, K otherKey)
      {
          if (key != null && otherKey != null)
          {
              return keyAnalyzer.bitIndex(key, otherKey);
          }
          else if (key != null)
          {
              return bitIndex(key);
          }
          else if (otherKey != null)
          {
              return bitIndex(otherKey);
          }
  
          return KeyAnalyzer.NULL_BIT_KEY;
      }
  
      private int bitIndex(K key)
      {
          int lengthInBits = lengthInBits(key);
          for (int i = 0; i < lengthInBits; i++)
          {
              if (isBitSet(key, i))
                  return i;
          }
  
          return KeyAnalyzer.NULL_BIT_KEY;
      }
  
      /**
       * An utility method for calling {@link KeyAnalyzer#compare(Object, Object)}
       */
      final boolean compareKeys(K key, K other)
      {
          if (key == null)
          {
              return (other == null);
          }
          else if (other == null)
          {
              return false;
          }
  
          return keyAnalyzer.compare(key, other) == 0;
      }
  
      /**
       * A basic implementation of {@link Entry}
       */
      abstract static class BasicEntry<K, V> implements Map.Entry<K, V>, Serializable
      {
          private static final long serialVersionUID = -944364551314110330L;
  
          protected K key;
  
          protected V value;
  
          private transient int hashCode = 0;
  
          public BasicEntry(K key, V value)
          {
              this.key = key;
              this.value = value;
          }
  
          /**
           * Replaces the current key and value with the provided
           * key &amp; value
           */
          public V setKeyValue(K key, V value)
          {
              this.key = key;
              this.hashCode = 0;
              return setValue(value);
          }
  
          @Override
          public K getKey()
          {
              return key;
          }
  
          @Override
          public V getValue()
          {
              return value;
          }
  
          @Override
          public V setValue(V value)
          {
              V previous = this.value;
              this.value = value;
              return previous;
          }
  
          @Override
          public int hashCode()
          {
              if (hashCode == 0)
                  hashCode = (key != null ? key.hashCode() : 0);
              return hashCode;
          }
  
          @Override
          public boolean equals(Object o)
          {
              if (o == this)
              {
                  return true;
              }
              else if (!(o instanceof Map.Entry<?, ?>))
              {
                  return false;
              }
  
              Map.Entry<?, ?> other = (Map.Entry<?, ?>)o;
              return Tries.areEqual(key, other.getKey()) && Tries.areEqual(value, other.getValue());
          }
  
          @Override
          public String toString()
          {
              return key + "=" + value;
          }
      }
  }
  